WO2015188662A1

WO2015188662A1 - Method of manufacturing long-life lithium-sulfur battery anode

Info

Publication number: WO2015188662A1
Application number: PCT/CN2015/077258
Authority: WO
Inventors: 邱新平; 贾磊; 朱文涛; 程小露
Original assignee: 清华大学
Priority date: 2014-06-12
Filing date: 2015-04-23
Publication date: 2015-12-17
Also published as: CN105304958B; CN105304958A

Abstract

A new method of synthesizing on the anode surface of a lithium-sulfur battery the lithium ion conductive protective film used for preventing diffusion of polysulfide ions and application of the method, to decrease the first discharge voltage lower limit of the lithium-sulfur battery using a carbon-sulfur compound as the anode material below the normal working voltage 1.5 V to produce the lithium ion conductive protective film; in addition, porous carbon with multi-level pores used as a support material can accommodate polysulfide ions and lithium sulfide produced in the charging/discharging process of sulfur and lithium-sulfur batteries.

Description

一种长寿命锂硫电池正极的制作方法Method for manufacturing long-life lithium-sulfur battery positive electrode

技术领域Technical field

本发明涉及锂电池正极材料领域，特别涉及锂硫电池正极材料的制备方法。The invention relates to the field of cathode materials for lithium batteries, in particular to a method for preparing cathode materials for lithium-sulfur batteries.

背景技术Background technique

随着化石燃料的大量使用，环境污染和能源危机日益严重，成为制约经济可持续发展的主要障碍，因此，当务之急是开发可再生的清洁能源。可再生清洁能源包括太阳能、风能、锂离子电池等新型能源，其中，锂离子电池是一种能够将化学能直接转变为电能并可循环使用的装置，其与其他二次能源相结合使用可以作为一个良好的能量储存体系。With the heavy use of fossil fuels, environmental pollution and energy crisis are becoming more and more serious, which has become a major obstacle to sustainable economic development. Therefore, it is imperative to develop renewable and clean energy. Renewable clean energy includes new energy sources such as solar energy, wind energy, and lithium-ion batteries. Among them, lithium-ion batteries are devices that can directly convert chemical energy into electrical energy and can be recycled, and can be used in combination with other secondary energy sources. A good energy storage system.

锂离子电池自1990年问世以来，以其比能量高、工作电压稳定(平均工作电压3.6V)、工作稳定范围宽等优点迅速成为了手机、数码相机、笔记本电脑等便携电子产品的主要电源。然而，目前广泛使用的锂离子电池正极材料的理论容量不高于200mAh/g，其平均工作电压3.6V，因此，其理论能量密度上限为720Wh/kg，而汽油的能量密度为12778KWh/kg，考虑到实际应用产品其他部件的重量和热值利用率，锂离子电池产品的能量密度需要至少提升10倍才有可能部分替代石油产品。Since its inception in 1990, lithium-ion batteries have rapidly become the main power source for portable electronic products such as mobile phones, digital cameras, and notebook computers due to their high specific energy, stable operating voltage (average working voltage of 3.6V), and wide operating stability range. However, the theoretical capacity of the lithium ion battery cathode material widely used at present is not higher than 200 mAh/g, and the average working voltage is 3.6 V. Therefore, the theoretical energy density upper limit is 720 Wh/kg, and the gasoline energy density is 12778 KWh/kg. Considering the weight and calorific value utilization of other components of the actual application, the energy density of lithium-ion battery products needs to be increased by at least 10 times to partially replace petroleum products.

将单质硫作为电池材料，其理论容量达到1675mAh/g，平均工作电压约为2V，能量密度可达3350Wh/kg，高出目前使用的锂离子电池材料5倍左右，而且硫具有价格低廉、自然储量丰富和无毒等优点，因此成功地开发出实用化的锂硫电池将能很好地解决上述问题，为下一代能量储存体系的研发提供技术支持。As the battery material, the elemental sulfur has a theoretical capacity of 1675 mAh/g, an average working voltage of about 2 V, and an energy density of 3350 Wh/kg, which is about 5 times higher than the currently used lithium ion battery material, and the sulfur has a low price and natural With abundant reserves and non-toxicity, the successful development of a practical lithium-sulfur battery will solve the above problems and provide technical support for the development of the next generation energy storage system.

然而，硫单质是高绝缘性的物质，电子导电率很低，单纯使用硫单质作为锂硫电池的正极材料将导致整个电池电阻过大而不能正常工作。目前，常采用开发高导电性的支撑材料对硫单质进行支撑，或引入导电性强的物质解决上述问题。However, the sulfur element is a highly insulating substance, and the electronic conductivity is very low. Simply using the sulfur element as the positive electrode material of the lithium-sulfur battery will cause the entire battery resistance to be too large to operate normally. At present, it is often used to develop a highly conductive support material to support a sulfur element, or to introduce a conductive substance to solve the above problem.

在支撑材料中，以碳作为骨架最为常见，碳是一种高导电性的物质，有多种形貌，比如多孔碳、介孔碳、碳纳米管和石墨烯等。如中国专利CN101986443A中公开了一种锂硫电池正极材料及其制备方法，该方法将纳米硫粒子加热熔化后填充于纳米介孔碳材料的空心纳米碳管中，而其纳米介孔碳材料是以蔗糖为碳源，浓硫酸为碳化剂，二氧化硅为模板剂，当蔗糖碳化后用氢氧化钠溶液或氢氟酸去除模板二氧化硅，该方法使用的试剂浓硫酸、氢氧化钠或氢氟酸均具有很强的腐蚀性，特别是浓硫酸和氢氟酸均属危险化学品，使用不当极易造成人身伤害和环境污染，工业实用性差，此外，其制备的纳米介孔碳材料的孔径单一，对硫在充放电过程中形成的不同粒径的离子无法适应性地附着容纳，从而不能解决聚硫离子在电解液中的溶解而形成的穿梭效应的问题。Among the support materials, carbon is the most common skeleton. Carbon is a highly conductive substance with various morphologies such as porous carbon, mesoporous carbon, carbon nanotubes and graphene. For example, a lithium-sulfur battery cathode material and a preparation method thereof are disclosed in the Chinese patent CN101986443A. The method comprises heating and melting the nano-sulfur particles and filling the hollow carbon nanotubes of the nano mesoporous carbon material, and the nano mesoporous carbon material is Taking sucrose as carbon source, concentrated sulfuric acid as carbonization agent and silica as template, when sucrose is carbonized, template silica is removed by sodium hydroxide solution or hydrofluoric acid. The reagent used in this method is concentrated sulfuric acid, sodium hydroxide or Hydrofluoric acid is highly corrosive. Especially concentrated sulfuric acid and hydrofluoric acid are dangerous chemicals. If used improperly, it is easy to cause personal injury and environmental pollution. The industrial applicability is poor. In addition, the nano-mesoporous carbon material prepared by it is poor. The pore size is single, and ions of different particle sizes formed during the charging and discharging process cannot be adaptively attached and accommodated, thereby failing to solve the problem of the shuttle effect formed by the dissolution of the polysulfide ions in the electrolyte.

又如中国专利CN103219501A公开了一种限制多硫化物溶出的锂硫电池正极材料，其由多孔碳和硫复合而成，其中多孔碳由介孔碳结构的内部核与微孔结构的外部壳构成，该多孔碳虽具有不同孔径结构，但对硫及其在充放电过程中产生的聚硫离子的化学吸附作用弱，因此，聚硫离子仍能在溶解于电解液后于负极一侧形成硫化锂沉积，从而导致由该正极材料制备的锂硫电池循环性能差，其首次放电容量仅为460～830mAh/g，在循环50周后，放电容量急剧下降，为402～682mAh/g，容量保持率仅为79～87％，不能满足实际应用的需求。Another example is Chinese patent CN103219501A, which discloses a lithium sulfur battery positive electrode material which is limited by polysulfide dissolution, which is composed of porous carbon and sulfur, wherein the porous carbon is composed of an inner core of a mesoporous carbon structure and an outer shell of a microporous structure. Although the porous carbon has a different pore structure, the chemical adsorption of sulfur and its polysulfide ions during charge and discharge is weak. Therefore, the polysulfide ions can still form lithium sulfide on the negative electrode side after being dissolved in the electrolyte. Deposition, resulting in poor cycle performance of the lithium-sulfur battery prepared from the positive electrode material, the first discharge capacity is only 460 ~ 830mAh / g, after 50 weeks of cycle, the discharge capacity drops sharply, 402 ~ 682mAh / g, capacity retention rate It is only 79 to 87%, which cannot meet the needs of practical applications.

再如中国专利CN102891292A公开了一种锂硫电池正极复合材料的制备方法，其使用葡萄糖作为碳源、浓硝酸作为碳化剂，二氧化硅作为模板剂，在制备碳纳米管后与升华硫、纳米铁粉、纳米锂盐及纳米钒盐混合，干燥烧结后掺杂稀土材料而得，其不仅在制备纳米碳纤维管过程中使用强腐蚀性及环境污染性试剂浓硝酸和氢氟酸，而且需要在碳纳米纤维管中掺杂稀土材料，这些材料价格昂贵，不易获得，不仅操作复杂还使得生产成本增加，不具有工业实用性；同时，该正极材料中硫包覆在纳米纤维管表面，而未嵌入碳纳米纤维管中，因此，其无法拦截硫在充放电过程中产生的多种形态的聚硫离子在电解液中的溶解和穿梭。Another example is Chinese patent CN102891292A, which discloses a method for preparing a lithium-sulfur battery positive electrode composite material, which uses glucose as a carbon source, concentrated nitric acid as a carbonizing agent, and silica as a template to prepare a carbon nanotube and sublimate sulfur and nanometer. Iron powder, nano lithium salt and nano vanadium salt are mixed, dried and sintered, doped with rare earth material, which not only uses strong corrosive and environmental pollution reagents concentrated nitric acid and hydrofluoric acid in the process of preparing nano carbon fiber tube, but also needs Carbon nanofiber tubes are doped with rare earth materials. These materials are expensive and difficult to obtain. Not only the operation is complicated, but also the production cost is increased, and there is no industrial applicability. Meanwhile, the cathode material is coated with sulfur on the surface of the nanofiber tube, but not Embedded in carbon nanofiber tubes, therefore, it cannot intercept various forms of polysulfide ions generated by sulfur during charge and discharge in the electrolyte. Dissolve and shuttle.

此外，目前锂硫电池在应用时普遍具有库伦效率低，比容量小，且在使用初期时比容量下降明显等问题，现有技术中存在采用对锂离子电池分段化成的方法来提高锂离子电池的使用容量和循环性能，如中国专利CN102185166B，公开了一种电池化成与修复方法，该方法对锂离子电池采用分段式化成，先进行小电流低压段充放电循环1～3次，再对锂离子电池进行大电流中压段快速充放电循环1～5次，使电池内部温度达到30～45℃；再对锂离子电池进行小电流高压段充放电循环1～3次；最后锂离子电池进行大电流深度充放电循环1～3次，该方法步骤繁琐，需要消耗大量时间，且操作条件不易控制，使用不便，而且，锂硫电池与普通锂电池的充放电机理不同，因此该对锂离子电池的性能改良的方法，无法适用到对锂硫电池性能的改良中。In addition, lithium-sulfur batteries generally have problems of low coulombic efficiency, small specific capacity, and significant decrease in specific capacity at the initial stage of use. In the prior art, there is a method of segmenting lithium ion batteries to improve lithium ions. The use capacity and cycle performance of the battery, such as the Chinese patent CN102185166B, discloses a battery formation and repair method. The method adopts a segmentation formation of a lithium ion battery, and first performs a charge and discharge cycle of a small current low voltage section 1 to 3 times, and then Lithium-ion battery is subjected to high-current medium-voltage section rapid charge-discharge cycle 1 to 5 times, so that the internal temperature of the battery reaches 30-45 ° C; then the lithium-ion battery is charged and discharged for 1 to 3 times in a small current and high-voltage section; The battery is subjected to a large current deep charge and discharge cycle 1 to 3 times. The method is cumbersome and requires a large amount of time, and the operating conditions are difficult to control, and the use is inconvenient. Moreover, the charging and discharging mechanism of the lithium-sulfur battery and the ordinary lithium battery are different, so the pair The improved performance of lithium-ion batteries cannot be applied to the improvement of the performance of lithium-sulfur batteries.

因此，亟待开发一种具有多级孔并对硫在充放电过程中产生的多种聚硫离子具有附着容纳或吸附能力的多孔碳支撑材料，和一种能够快速简便地提高锂硫电池比容量、循环性能和倍率性能的方法。Therefore, it is urgent to develop a porous carbon supporting material having a multi-stage pore and having a plurality of polysulfide ions generated by charging and discharging in the charging and discharging process, and a porous carbon supporting material capable of quickly and easily improving the specific capacity of the lithium-sulfur battery. , cycle performance and rate performance methods.

发明内容Summary of the invention

为了解决上述问题，本发明人进行了锐意研究，结果发现：锂硫电池在首次放电时将放电电压下限降低至正常工作电压下限1.5V以下，可使锂硫电池的循环性能及倍率性能显著提升，自放电现象明显降低；用于现场合成锂离子导电保护膜的基体可以通过以下方法制备：将碳源化合物与不同粒径级别的模板粒子在高温下碳化，再用酸溶液或碱溶液去除模板粒子，制得表面未经修饰的具有多级孔的多孔碳，然后，任选地，依次用浓硝酸及浓氨水对该具有多级孔的多孔碳的表面进行修饰，使制得的多孔碳基体的表面修饰有羧酸铵基团，即可简便地制得表面经过修饰的具有多级孔的多孔碳，上述两种多孔碳中的孔均包括两级孔，其中一级孔的孔径约为2～10nm，二级孔的孔径约为100～300nm，将硫磺嵌入上述多孔碳中，即可制成碳-硫复合材料，其中不同孔径的孔对锂硫电池在充放电过程中产生的不同粒径的聚硫离子能够适应性地吸附容纳，使不同半径的聚硫离子均能被嵌入于多孔碳中，减少其在电解液中的溶解，从而降低聚硫离子在电解液中的穿梭效应，进而提高锂硫电池的电化学性能，从而完成本发明。In order to solve the above problems, the inventors conducted intensive research and found that the lithium-sulfur battery reduces the lower limit of the discharge voltage to 1.5V below the lower limit of the normal working voltage during the first discharge, which can significantly improve the cycle performance and rate performance of the lithium-sulfur battery. The self-discharge phenomenon is obviously reduced; the substrate for synthesizing the lithium ion conductive protective film in the field can be prepared by carbonizing the carbon source compound and the template particles of different particle size levels at a high temperature, and then removing the template by using an acid solution or an alkali solution. a particle, a porous carbon having a multistage pore having an unmodified surface, and then, optionally, a surface of the porous carbon having a multistage pore is sequentially modified with concentrated nitric acid and concentrated ammonia water to obtain a porous carbon The surface of the substrate is modified with an ammonium carboxylate group, and the surface-modified porous carbon having a plurality of pores can be easily prepared. The pores in the two porous carbons include two-stage pores, wherein the pore size of the first-order pores is about 2 to 10 nm, the pore size of the secondary pore is about 100-300 nm, and sulfur is embedded in the porous carbon to form a carbon-sulfur composite material, wherein the pores have different pore sizes. The polysulfide ions of different particle sizes produced by the lithium-sulfur battery during charging and discharging can be adaptively accommodated, so that polysulfide ions of different radii can be embedded in the porous carbon to reduce their dissolution in the electrolyte, thereby The invention is accomplished by reducing the shuttle effect of polysulfide ions in an electrolyte, thereby improving the electrochemical performance of the lithium-sulfur battery.

本发明的目的在于提供以下方面：The object of the present invention is to provide the following aspects:

1.一种现场合成锂离子导电保护膜的方法，其特征在于，该方法为以碳-硫复合物为正极材料的锂硫电池在首次放电时，将放电电压下限降低至正常工作电压下限1.5V以下，优选为1.2V或以下，再充电至工作电压。A method for synthesizing a lithium ion conductive protective film in the field, characterized in that the lithium-sulfur battery using a carbon-sulfur composite as a positive electrode material reduces the lower limit of the discharge voltage to a lower limit of a normal working voltage at the first discharge of 1.5. Below V, preferably 1.2 V or less, is recharged to an operating voltage.

2.用作上述1中所述的现场合成锂离子导电保护膜基体的具有多级孔的多孔碳，其特征在于，该多孔碳包括碳骨架，在碳骨架中分布一级孔和二级孔，其中，一级孔的孔径约为2～10nm，二级孔的孔径约为100～300nm，任选地，在碳骨架表面修饰有羧酸铵基团，在一级孔和二级孔的孔壁表面上修饰有羧酸铵基团。2. A porous carbon having a multistage pore as a matrix for synthesizing a lithium ion conductive protective film according to the above 1, characterized in that the porous carbon comprises a carbon skeleton, and a primary pore and a secondary pore are distributed in the carbon skeleton. Wherein the primary pore has a pore diameter of about 2 to 10 nm, and the secondary pore has a pore diameter of about 100 to 300 nm, optionally, a carboxylate group is modified on the surface of the carbon skeleton, in the primary pore and the secondary pore. The surface of the pore wall is modified with an ammonium carboxylate group.

3.根据上述2所述的具有多级孔的多孔碳，其特征在于，所述一级孔通过一级模板粒子形成，二级孔通过二级模板粒子形成，其中，3. The porous carbon having a multi-stage pore according to the above 2, wherein the primary pore is formed by primary template particles, and the secondary pore is formed by secondary template particles, wherein

一级模板粒子为粒径约为2～10nm的化合物颗粒，该化合物颗粒在碳化条件下不与其他成分反应，而易溶于酸和/或碱，和/或，The primary template particles are compound particles having a particle diameter of about 2 to 10 nm, and the compound particles do not react with other components under carbonization conditions, but are easily soluble in acids and/or bases, and/or

二级模板粒子为粒径约为100～300nm的化合物颗粒，该化合物颗粒在碳化条件下不与其他成分反应，而易溶于酸和/或碱，The secondary template particles are compound particles having a particle diameter of about 100 to 300 nm, and the compound particles do not react with other components under carbonization conditions, but are easily soluble in acids and/or bases.

所述碳化条件是指用于形成碳骨架的碳源化合物的碳化条件。The carbonization conditions refer to carbonization conditions of a carbon source compound used to form a carbon skeleton.

4.根据上述2所述的具有多级孔的多孔碳，其特征在于，4. The porous carbon having a plurality of stages according to the above 2, characterized in that

所述一级孔通过用酸溶液或碱溶液将一级模板粒子从含有固态一级模板粒子的碳源化合物的碳化产物中去除而形成；The primary pores are formed by removing primary template particles from a carbonized product of a carbon source compound containing solid primary template particles with an acid solution or an alkali solution;

所述二级孔通过用酸溶液或碱溶液将二级模板粒子从含有固态二级模板粒子的碳源化合物的碳化产物中去除而形成。The secondary pores pass the secondary template particles from the carbon containing the solid secondary template particles with an acid solution or an alkali solution The carbonization product of the source compound is removed to form.

5.上述2所述的具有多级孔的多孔碳的制备方法，其特征在于，该方法包括以下步骤：5. The method for producing porous carbon having a plurality of stages according to the above 2, characterized in that the method comprises the steps of:

(1-1)按重量比为一级模板粒子:二级模板粒子:碳源化合物＝1:(1～3):(2～5)的比例称取一级模板粒子、二级模板粒子和碳源化合物，充分混合均匀，制得混合物，其中，(1-1) by weight ratio of primary template particles: secondary template particles: carbon source compound = 1: (1 ~ 3): (2 ~ 5) ratio of the first template particles, secondary template particles and a carbon source compound which is uniformly mixed to obtain a mixture, wherein

一级模板粒子为粒径约为2～10nm的化合物颗粒，该化合物颗粒在碳化条件下不与其他成分反应，而易溶于酸和/或碱，用于形成具有多级孔的多孔碳中的一级孔，和/或，The primary template particles are compound particles having a particle diameter of about 2 to 10 nm, and the compound particles do not react with other components under carbonization conditions, but are easily soluble in acids and/or bases and are used to form porous carbon having multi-stage pores. Level 1 hole, and / or,

二级模板粒子为粒径约为100～300nm的化合物颗粒，该化合物颗粒在碳化条件下不与其他成分反应，而易溶于酸和/或碱，用于形成具有多级孔的多孔碳中的二级孔，The secondary template particles are compound particles having a particle diameter of about 100 to 300 nm, and the compound particles do not react with other components under carbonization conditions, but are easily soluble in acids and/or bases for forming porous carbon having multi-stage pores. Secondary hole,

所述碳源化合物为易于碳化的化合物，The carbon source compound is a compound that is easily carbonized.

所述碳化条件是指用于形成碳骨架的碳源化合物的碳化条件；The carbonization condition refers to a carbonization condition of a carbon source compound used to form a carbon skeleton;

(1-2)将步骤(1-1)中制得的混合物在保护性气体保护下，于800～1200℃条件下碳化2～20小时，冷却，得到碳化产物，(1-2) The mixture obtained in the step (1-1) is carbonized at 800 to 1200 ° C for 2 to 20 hours under a protective gas atmosphere, and cooled to obtain a carbonized product.

其中，所述保护性气体为，按体积比为氢气:氩气＝(1～15):(85～99)的氢气与氩气的混合气；Wherein, the protective gas is a mixture of hydrogen and argon in a volume ratio of hydrogen: argon = (1 to 15): (85 to 99);

(1-3)将步骤(1-2)中得到的碳化产物置于酸溶液或碱溶液中，去除一级模板粒子和二级模板粒子，制得具有多级孔的多孔碳；(1-3) The carbonized product obtained in the step (1-2) is placed in an acid solution or an alkali solution to remove the primary template particles and the secondary template particles to obtain porous carbon having a plurality of pores;

6.根据上述5所述的具有多级孔的多孔碳的制备方法，其特征在于，该方法在步骤(1-3)之后，任选地，包括以下步骤：6. The method for producing porous carbon having a plurality of stages according to the above 5, characterized in that the method, after the step (1-3), optionally, comprises the following steps:

(1-4)将步骤(1-3)中制得的多孔碳基体置于浓硝酸中，在40～70℃下回流5～15小时，分离除去液体，洗涤，用浓氨水浸泡8～20小时，过滤洗涤，干燥，制得表面经过修饰的具有多级孔的多孔碳。(1-4) The porous carbon substrate obtained in the step (1-3) is placed in concentrated nitric acid, refluxed at 40 to 70 ° C for 5 to 15 hours, the liquid is separated and removed, washed, and soaked in concentrated ammonia water for 8 to 20 After hours, it was filtered, washed, and dried to obtain a surface-modified porous carbon having a plurality of pores.

7.一种碳-硫复合材料，其特征在于，该复合材料包括上述2～4中任一项所述的具有多级孔的多孔碳和硫磺颗粒，其中硫磺颗粒嵌于具有多级孔的多孔碳的一级孔和二级孔中。A carbon-sulfur composite material, comprising the porous carbon and sulfur particles having a multi-stage pore according to any one of the above 2 to 4, wherein the sulfur particles are embedded in a multi-stage pore. The primary and secondary pores of porous carbon.

8.根据上述6所述的碳-硫复合材料的制备方法，其特征在于，该方法包括以下步骤：8. The method for preparing a carbon-sulfur composite according to the above 6, characterized in that the method comprises the following steps:

(2-1)按照重量比为多孔碳:硫磺＝1：(1～3)，将上述2～4中任一项所述的具有多级孔的多孔碳与硫磺混合，研磨，在密封环境、保护性气体保护下升温至155℃，保温，在此情况下，硫磺液化，液体硫磺进入多孔碳的一级孔和二级孔中，再在流动的保护性气体气氛下升温至170～200℃，保温，在此情况下，增加硫磺的气化速率，气体硫磺随着流动的保护性气体进一步分散并进入多孔碳的一级孔和二级孔中或者随着流动性气体而被移除脱离复合材料体系，得到孔中分散有硫磺的多孔碳，(2-1) The porous carbon having a multistage pore according to any one of the above 2 to 4 is mixed with sulfur according to the weight ratio of porous carbon: sulfur = 1: (1 to 3), and is ground in a sealed environment. Under the protection of protective gas, the temperature is raised to 155 ° C, and the temperature is kept. In this case, the sulfur is liquefied, the liquid sulfur enters the primary pores and the secondary pores of the porous carbon, and then the temperature is raised to 170-200 under the flowing protective gas atmosphere. °C, heat preservation, in this case, increase the gasification rate of sulfur, gas sulfur is further dispersed with the flowing protective gas and enters the primary and secondary pores of the porous carbon or is removed with the flowing gas Breaking away from the composite system to obtain porous carbon with sulfur dispersed in the pores,

(2-2)将孔中分散有硫磺的多孔碳置于空气中冷却。(2-2) The porous carbon in which sulfur is dispersed in the pores is cooled in the air.

9.根据上述7所述的碳-硫复合材料作为锂硫电池正极材料的用途。9. Use of the carbon-sulfur composite material according to the above 7 as a cathode material for a lithium sulfur battery.

在本发明中，C-NH₄表示表面经过修饰的多孔碳，C-S表示表面未经修饰的碳-硫复合材料，C-NH₄-S表示表面经过修饰的碳-硫复合材料，上述三种材料均为本发明所提供。In the present invention, C-NH ₄ represents a surface-modified porous carbon, CS represents a surface-unmodified carbon-sulfur composite material, and C-NH ₄ -S represents a surface-modified carbon-sulfur composite material, the above three types. Materials are provided by the present invention.

根据本发明提供的现场合成锂离子导电保护膜的方法、具有多级孔的多孔碳及其制备方法和应用、碳-硫复合材料及其制备方法和应用和该碳-硫复合材料用于锂硫电池正极材料的用途，具有以下有益效果：Method for synthesizing lithium ion conductive protective film in situ according to the present invention, porous carbon having multi-stage pores, preparation method and application thereof, carbon-sulfur composite material, preparation method and application thereof and carbon-sulfur composite material for lithium The use of the sulfur battery positive electrode material has the following beneficial effects:

(1)由该多孔碳制成的碳-硫复合材料在首次放电至1.5V以下，优选为1.2V或以下后，其电容量可较快地稳定于约1000mAh/g(容量以硫磺重量计算，以下均同)，以其组装的电池最大容量可达1200mAh/g，库伦效率可达100％；(1) The carbon-sulfur composite material made of the porous carbon can be stabilized at about 1000 mAh/g relatively quickly after the first discharge to 1.5 V or less, preferably 1.2 V or less (the capacity is calculated by the weight of sulfur) , the following are the same), the maximum capacity of the battery assembled by it can reach 1200mAh/g, and the Coulomb efficiency can reach 100%;

(2)该具有多级孔的多孔碳具有碳骨架，其中分布有孔径不同的一级孔和二级孔，同时，其碳骨架上也存在微孔，使得该多孔碳能够将硫磺及在充放电过程中产生的不同粒径的聚硫离子适应性地嵌于孔内，阻止其溶解于电解液中，从而彻底解决了聚硫离子的穿梭效应，并且这些孔的表面可任选地修饰有羧酸铵基团，使上述作用更为显著；(2) The porous carbon having a multi-stage pore has a carbon skeleton in which a primary pore and a secondary pore having different pore diameters are distributed, and at the same time, micropores are also present on the carbon skeleton, so that the porous carbon can carry sulfur and charge Different particles produced during discharge The polysulfide ion of the diameter is adaptively embedded in the pore to prevent it from being dissolved in the electrolyte, thereby completely solving the shuttle effect of the polysulfide ion, and the surface of the pore may optionally be modified with an ammonium carboxylate group. The above effects are more significant;

(3)该具有多级孔的多孔碳在孔表面修饰羧酸铵基团后，锂硫电池在首次放电时放电至1.5V以下可以实现对正极材料的活化，而表面未经修饰的多孔碳在放电至0.8V以下时可以实现对正极材料的活化，减少电池负极材料金属锂的消耗，操作难度低；(3) After the porous carbon having a multi-stage pore is modified with an ammonium carboxylate group on the surface of the pore, the lithium-sulfur battery can be activated to the cathode material by discharging to 1.5 V or less at the first discharge, and the surface is unmodified porous carbon. When the discharge reaches 0.8V or less, the activation of the positive electrode material can be realized, and the consumption of the metal lithium of the battery negative electrode material can be reduced, and the operation difficulty is low;

(4)制备该具有多级孔的多孔碳的方法操作简单，去除模板粒子的方法简便，不会造成环境污染；(4) The method for preparing the porous carbon having multi-stage pores is simple in operation, and the method for removing the template particles is simple and does not cause environmental pollution;

(5)由上述多孔碳制备的碳-硫复合材料在充放电过程中可快速形成锂离子导电保护膜，从而提高电池的循环性能、倍率性能，降低其自放电效应；(5) The carbon-sulfur composite material prepared by the above porous carbon can rapidly form a lithium ion conductive protective film during charging and discharging, thereby improving the cycle performance and rate performance of the battery and reducing the self-discharge effect;

(6)硫磺颗粒与多孔碳中其所在孔的孔壁之间存在一定空间，允许硫在放电过程中形成硫化锂而引起体积膨胀，有效避免碳-硫复合材料的崩塌。(6) There is a certain space between the sulfur particles and the pore walls of the pores in the porous carbon, which allows the formation of lithium sulfide during the discharge of sulfur to cause volume expansion, and effectively avoids collapse of the carbon-sulfur composite material.

附图说明DRAWINGS

图1a示出C-NH₄的透射电镜图；Figure 1a shows a transmission electron micrograph of C-NH ₄ ;

图1b示出C-NH₄的透射电镜图；Figure 1b shows a transmission electron micrograph of C-NH ₄ ;

图2a示出C-NH₄-S的透射电镜图；Figure 2a shows a transmission electron micrograph of C-NH ₄ -S;

图2b示出C-NH₄-S的透射电镜图；Figure 2b shows a transmission electron micrograph of C-NH ₄ -S;

图3a示出C-NH₄-S制备的样品高分辨电镜图；Figure 3a shows the sample C-NH HREM FIG prepared ₄ -S;

图3b示出C-NH₄-S制备的样品EDS(Energy Dispersive Spectroscopy，以下均同)图；Figure 3b shows a sample EDS (Energy Dispersive Spectroscopy) prepared by C-NH ₄ -S;

图4a示出C-NH₄(曲线a)、C-NH₄-S(曲线b)、C(曲线c)制得样品的XRD(X-ray diffraction，以下均同)光谱图；4a shows an XRD (X-ray diffraction, hereinafter the same) spectrum of a sample prepared by C-NH ₄ (curve a), C-NH ₄ -S (curve b), and C (curve c);

图4b示出硫磺单质的XRD光谱图；Figure 4b shows an XRD spectrum of the sulfur element;

图5a示出实施例2(曲线a)、实施例4(曲线b)、实施例1(曲线c)制得样品的拉曼光谱图；Figure 5a shows a Raman spectrum of a sample prepared in Example 2 (curve a), Example 4 (curve b), and Example 1 (curve c);

图5b示出单质硫的拉曼光谱图；Figure 5b shows a Raman spectrum of elemental sulfur;

图6a示出本发明提供的C-S首次放电至1.0V后充放电曲线；Figure 6a shows the charge-discharge curve of the C-S after the first discharge to 1.0V provided by the present invention;

图6b示出本发明提供的C-S首次放电至1.0V后比电容曲线；Figure 6b shows the specific capacitance curve of the C-S after the first discharge to 1.0V provided by the present invention;

图7a示出本发明提供的C-S首次放电至0.9V后充放电曲线；Figure 7a shows the charge-discharge curve of the C-S after the first discharge to 0.9V provided by the present invention;

图7b示出本发明提供的C-S首次放电至0.9V后比电容曲线；Figure 7b shows the specific capacitance curve of the C-S after the first discharge to 0.9V provided by the present invention;

图8a示出本发明提供的C-S首次放电至0.8V后充放电曲线；Figure 8a shows the charge-discharge curve of the C-S after the first discharge to 0.8V provided by the present invention;

图8b示出本发明提供的C-S首次放电至0.8V后比电容曲线；Figure 8b shows the specific capacitance curve of the C-S after the first discharge to 0.8V provided by the present invention;

图9a示出本发明提供的C-S首次放电至0.7V后充放电曲线；Figure 9a shows the charge-discharge curve of the C-S after the first discharge to 0.7V provided by the present invention;

图9b示出本发明提供的C-S首次放电至0.7V后比电容曲线；Figure 9b shows the specific capacitance curve of the C-S after initial discharge to 0.7V provided by the present invention;

图10a示出本发明提供的C-NH₄-S首次放电至1.0V后充放电曲线；Figure 10a shows the charge-discharge curve of the C-NH ₄ -S provided by the present invention after first discharge to 1.0V;

图10b示出本发明提供的C-NH₄-S首次放电至1.0V后比电容曲线；Figure 10b shows the specific capacitance curve after the first discharge of C-NH ₄ -S to 1.0 V provided by the present invention;

图11a示出本发明提供的C-NH₄-S首次放电至0.9V后充放电曲线；Figure 11a shows the charge-discharge curve of C-NH ₄ -S after initial discharge to 0.9V provided by the present invention;

图11b示出本发明提供的C-NH₄-S首次放电至0.9V后比电容曲线；Figure 11b shows the specific capacitance curve of the C-NH ₄ -S first discharge to 0.9V provided by the present invention;

图12a示出本发明提供的C-NH₄-S首次放电至0.8V后充放电曲线；Figure 12a shows the charge-discharge curve of the C-NH ₄ -S provided by the present invention after first discharge to 0.8V;

图12b示出本发明提供的C-NH₄-S首次放电至0.8V后比电容曲线；Figure 12b shows the specific capacitance curve of the C-NH ₄ -S after the first discharge to 0.8V provided by the present invention;

图13a示出本发明提供的C-NH₄-S首次放电至0.7V后充放电曲线；Figure 13a shows the charge-discharge curve of C-NH ₄ -S after initial discharge to 0.7V provided by the present invention;

图13b示出本发明提供的C-NH₄-S首次放电至0.7V后比电容曲线；Figure 13b shows the specific capacitance curve of the C-NH ₄ -S first discharge to 0.7V provided by the present invention;

图14a示出本发明提供的C-NH₄-S首次放电未经低压放电处理的充放电曲线；Figure 14a shows a charge and discharge curve of the first discharge of C-NH ₄ -S provided by the present invention without low-pressure discharge treatment;

图14b示出本发明提供的C-NH₄-S首次放电未经低压放电处理的比电容曲线；14b shows C-NH ₄ -S present invention provides the first discharge curve of the capacitor without the low-pressure discharge treatment;

图15a示出本发明提供的C-S首次放电未经低压放电处理的充放电曲线；Figure 15a shows a charge and discharge curve of the first discharge of the C-S provided by the present invention without low-pressure discharge treatment;

图15b示出本发明提供的C-S首次放电未经低压放电处理的比电容曲线； Figure 15b shows a specific capacitance curve of the first discharge of the C-S provided by the present invention without low-voltage discharge treatment;

图16a示出用本发明提供的C-NH₄-S制得的电极片初始状态的HRSEM图；Figure 16a is a HRSEM image showing an initial state of an electrode sheet prepared by using C-NH ₄ -S provided by the present invention;

图16b示出用本发明提供的C-NH₄-S制得的电极片在1.5V电压下的HRSEM图；Figure 16b shows an HRSEM image of an electrode sheet prepared by using the C-NH ₄ -S provided by the present invention at a voltage of 1.5V;

图16c示出用本发明提供的C-NH₄-S制得的电极片在1.0V电压下的HRSEM图；Figure 16c shows an HRSEM image of an electrode sheet prepared by using C-NH ₄ -S provided by the present invention at a voltage of 1.0 V;

图16d示出用本发明提供的C-NH₄-S制得的电极片在0.8V电压下的HRSEM图；Figure 16d shows C-NH with the present invention provides ₄ -S electrode sheet obtained HRSEM FIG voltage at 0.8V;

图17a示出用本发明提供的C-S在放电至不同电压下的XRD图；Figure 17a shows an XRD pattern of the C-S provided by the present invention at discharge to different voltages;

图17b为实施例2制得的样品在放电至不同电压下的XRD图；Figure 17b is an XRD pattern of the sample prepared in Example 2 under discharge to different voltages;

图17c为本发明提供的C-S在不同循环次数下的XRD图；Figure 17c is an XRD diagram of the C-S provided by the present invention at different cycle times;

图17d为实施例2制得的样品在不同循环次数下的XRD图；Figure 17d is an XRD pattern of the sample prepared in Example 2 at different cycle times;

图18a示出本发明提供的C-NH₄-S的充放电电压曲线(首次放电时放电至1.0V，0.1C循环10周之后以0.5C充放电)；Figure 18a shows the charge-discharge voltage curve of C-NH ₄ -S provided by the present invention (discharge to 1.0 V at the first discharge, charge and discharge at 0.5 C after a 10 C cycle at 0.1 C);

图18b示出本发明提供的C-NH₄-S的倍率性能测试(首次放电时放电至1.0V，0.1C循环10周之后以0.5C充放电)；18b shows C-NH ₄ -S rate performance testing of the present invention provides (when the first discharge discharged to 1.0V, 0.1C after 10 cycles of charge and discharge at 0.5C);

图19a示出本发明提供的C-NH₄-S的充放电电压曲线(首次放电时放电至1.0V，0.1C循环10周之后以1C充放电)；Figure 19a shows the charge-discharge voltage curve of C-NH ₄ -S provided by the present invention (discharge to 1.0 V at the first discharge, charge and discharge at 1 C after a 10 C cycle at 0.1 C);

图19b示出本发明提供的C-NH₄-S的倍率性能测试(首次放电时放电至1.0V，0.1C循环10周之后以1C充放电)；Figure 19b shows the rate performance test of C-NH ₄ -S provided by the present invention (discharge to 1.0 V at the first discharge, charge and discharge at 1 C after a 10 C cycle at 0.1 C);

图20a示出本发明提供的C-NH₄-S的充放电电压曲线(首次放电时未经低压放电处理，0.1C循环10周之后以0.5C充放电)；Figure 20a shows the charge-discharge voltage curve of the C-NH ₄ -S provided by the present invention (the first discharge is not subjected to the low-pressure discharge treatment, and the 0.1C cycle is charged and discharged at 0.5 C after 10 weeks);

图20b示出本发明提供的C-NH₄-S的倍率性能测试(首次放电时未经低压放电处理，0.1C循环10周之后以0.5C充放电)；Figure 20b shows the rate performance test of C-NH ₄ -S provided by the present invention (there is no low-pressure discharge treatment at the first discharge, and 0.5 C charge and discharge after 10 cycles of 0.1 C cycle);

图21a示出本发明提供的C-NH₄-S的充放电电压曲线(首次放电时未经低压放电处理，0.1C循环10周之后以1C充放电)；Figure 21a shows the charge-discharge voltage curve of C-NH ₄ -S provided by the present invention (there is no low-pressure discharge treatment at the first discharge, and 1 C charge and discharge after 10 cycles at 0.1 C);

图21b示出本发明提供的C-NH₄-S的倍率性能测试(首次放电时未经低压放电处理，0.1C循环10周之后以1C充放电)；Figure 21b shows the rate performance test of C-NH ₄ -S provided by the present invention (there is no low-pressure discharge treatment at the first discharge, and 1 C charge and discharge after 10 cycles at 0.1 C);

图22a示出以本发明提供的C-NH₄-S为正极的锂硫电池的总循环数据与库伦效率图；Figure 22a shows a C-NH to the present invention provides ₄ -S positive electrode of lithium-sulfur battery and the total cycle coulombic efficiency map data;

图22b示出以本发明提供的C-NH₄-S为正极的锂硫电池充放电6周后搁置48小时前后的循环数据与库伦效率图；Figure 22b is a graph showing cycle data and coulombic efficiency before and after the lithium-sulfur battery provided with the C-NH ₄ -S provided by the present invention as a positive electrode for 6 weeks after being charged and discharged for 6 weeks;

图22c示出以本发明提供的C-NH₄-S为正极的锂硫电池以0.1C充放电结束后搁置48小时后再以1C充放电的循环数据与库伦效率图；Figure 22c is a cycle data and coulombic efficiency diagram of a lithium-sulfur battery with a C-NH ₄ -S provided by the present invention as a positive electrode after being charged and discharged at 0.1 C for 48 hours and then charged and discharged at 1 C;

图22d示出以本发明提供的C-NH₄-S为正极的锂硫电池以1C充放电结束后搁置48小时后再以0.1C充放电的循环数据与库伦效率图；Figure 22d is a cycle data and coulombic efficiency diagram of a lithium-sulfur battery provided with a C-NH ₄ -S provided by the present invention as a positive electrode after being charged and discharged for 1 hour, and then charged and discharged at 0.1 C after being charged for 1 hour;

图22e示出以本发明提供的C-NH₄-S为正极的锂硫电池首先充电至未充满状态再搁置48小时的循环数据与库伦效率图；Figure 22e is a graph showing cycle data and coulombic efficiency of a lithium-sulfur battery in which the C-NH ₄ -S provided by the present invention is first charged to an unfilled state and then left for 48 hours;

图22f示出以本发明提供的C-NH₄-S为正极的锂硫电池充电至2.5V后，分步放电的循环数据与库伦效率图；Figure 22f is a cycle data and coulombic efficiency diagram of a step discharge after charging a lithium-sulfur battery having a C-NH ₄ -S positive electrode provided by the present invention to 2.5V;

图22g示出以本发明提供的C-NH₄-S为正极的锂硫电池搁置6天的循环数据与库伦效率图；FIG. 22g shows C-NH to the present invention provides ₄ -S 6 days for the rest of the positive electrode and lithium-sulfur battery cycle coulombic efficiency map data;

图22h示出以本发明提供的C-NH₄-S为正极的锂硫电池搁置15天的循环数据与库伦效率图；Figure 22h shows a cycle data and a coulombic efficiency map of a lithium-sulfur battery with a C-NH ₄ -S provided by the present invention as a positive electrode for 15 days;

图22i示出以本发明提供的C-NH₄-S为正极的锂硫电池搁置6天的电压变化图；Figure 22i is a graph showing voltage changes of a lithium-sulfur battery in which C-NH ₄ -S provided by the present invention is a positive electrode for 6 days;

图22j示出以本发明提供的C-NH₄-S为正极的锂硫电池搁置15天的电压变化图；Figure 22j is a graph showing voltage changes of a lithium-sulfur battery in which C-NH ₄ -S provided by the present invention is a positive electrode for 15 days;

图23a示出本发明提供的C-S复合材料在初始状态和放电至1.5V和1.0V电压状态下的阻抗谱；Figure 23a shows the impedance spectrum of the C-S composite provided by the present invention in an initial state and discharged to a voltage of 1.5V and 1.0V;

图23b示出本发明提供的C-S复合材料在放电至1.0V、0.8V和0.6V电压状态下的阻抗谱； Figure 23b shows the impedance spectrum of the C-S composite provided by the present invention at a voltage of 1.0 V, 0.8 V, and 0.6 V;

图24a示出本发明提供的C-NH₄-S复合材料在初始状态和放电至1.5V、1.0V电压状态下的阻抗谱；Figure 24a shows the impedance spectrum of the C-NH ₄ -S composite provided by the present invention in an initial state and discharged to a voltage of 1.5 V and 1.0 V;

图24b示出本发明提供的C-NH₄-S复合材料在放电至1.0V、0.8V和0.6V电压状态下的阻抗谱；Figure 24b shows the impedance spectrum of the C-NH ₄ -S composite provided by the present invention at a voltage of 1.0 V, 0.8 V, and 0.6 V;

图24c示出本发明提供的C-NH₄-S复合材料在放电至0.8V、0.6V和0.4V电压状态下的阻抗谱；Figure 24c shows the impedance spectrum of the C-NH ₄ -S composite provided by the present invention at a voltage of 0.8 V, 0.6 V, and 0.4 V;

图24d示出本发明提供的C-NH₄-S复合材料在放电至0.6V、0.4V和0.2V电压状态下的阻抗谱；Figure 24d shows the impedance spectrum of the C-NH ₄ -S composite provided by the present invention at a voltage of 0.6 V, 0.4 V, and 0.2 V;

图25示出本发明提供的具有多级孔的多孔碳的微观结构示意图；Figure 25 is a schematic view showing the microstructure of porous carbon having a plurality of stages of pores provided by the present invention;

图26示出锂硫电池充放电过程中锂离子导电保护膜生成机理示意图，其中1为锂离子导电保护膜；26 is a schematic view showing a mechanism of formation of a lithium ion conductive protective film during charging and discharging of a lithium-sulfur battery, wherein 1 is a lithium ion conductive protective film;

图27示出锂硫电池充放电过程中惰性硫化锂保护机理示意图，其中2为失活部分。Fig. 27 is a view showing the mechanism of protection of inert lithium sulfide during charging and discharging of a lithium-sulfur battery, wherein 2 is a deactivated portion.

具体实施方式detailed description

下面通过对本发明进行详细说明，本发明的特点和优点将随着这些说明而变得更为清楚、明确。The features and advantages of the present invention will become more apparent from the description of the invention.

本发明人经过研究发现，以碳-硫复合材料作为正极材料的锂硫电池，在首次放电时使正常放电电压下限降低至1.5V以下，可以促进锂硫电池的正极材料在首次放电时快速形成锂离子导电保护膜，从而提高锂硫电池的循环性能、倍率性能和自放电性能等，同时，具有多级孔的多孔碳对锂硫电池中作为正极材料的硫磺及在充放电过程中产生的不同半径的聚硫离子具有良好的附着容纳作用，其可以通过以在常规条件下容易碳化的化合物作为碳源化合物，以可被酸和/或碱溶液去除的化合物颗粒作为多孔碳孔径的模板粒子，将碳源化合物碳化后用酸溶液及碱溶液去除包裹于碳化产物中的模板粒子，即可制得，任选地，再通过化学方法对该多孔碳的表面进行修饰，使多孔碳表面修饰有羧酸铵基团，即可得到表面经过修饰的具有多级孔的多孔碳，再将该具有多级孔的多孔碳与硫磺进行物理化学性复合，即可制得用作锂硫电池正极材料的碳-硫复合材料。The inventors have found through research that a lithium-sulfur battery using a carbon-sulfur composite material as a positive electrode material reduces the lower limit of the normal discharge voltage to less than 1.5 V during the first discharge, which can promote the rapid formation of the positive electrode material of the lithium-sulfur battery during the first discharge. Lithium ion conductive protective film, thereby improving the cycle performance, rate performance and self-discharge performance of the lithium-sulfur battery, and at the same time, the porous carbon having a multi-stage pore is used as a positive electrode material in a lithium-sulfur battery and is generated during charging and discharging. Polysulfide ions of different radii have a good adhesion-accommodating effect, and can be used as a carbon source compound by a compound which is easily carbonized under a conventional condition, and a compound particle which can be removed by an acid and/or an alkali solution as a template particle of a porous carbon pore size. After carbonizing the carbon source compound, the template particles encapsulated in the carbonized product are removed by using an acid solution and an alkali solution, and optionally, the surface of the porous carbon is modified by a chemical method to modify the surface of the porous carbon. With a carboxylate group, a surface-modified porous carbon having a plurality of pores can be obtained, and the multi-stage Porous carbon composite physicochemical sulfur, carbon can be prepared as a positive electrode material lithium-sulfur battery - sulfur composite material.

SEI膜为“solid electrolyte interface，固体电解质界面膜”，本发明中提出的锂离子导电保护膜可以理解为一种SEI膜，其是在液态锂离子电池首次充放电过程中，电极材料与电解液在固液相界面上发生反应，形成一层覆盖于电极材料表面的钝化膜，这种钝化膜是一种界面层，具有固体电解质的特征，是电子绝缘体却是Li⁺的优良导体，Li⁺可以经过该钝化膜自由地嵌入和脱出于正极材料。The SEI film is a "solid electrolyte interface", and the lithium ion conductive protective film proposed in the present invention can be understood as an SEI film, which is an electrode material and an electrolyte during the first charge and discharge of a liquid lithium ion battery. A reaction occurs at the solid-liquid phase interface to form a passivation film covering the surface of the electrode material. The passivation film is an interface layer having the characteristics of a solid electrolyte, and is an excellent insulator of the electronic insulator but Li ⁺ . Li ⁺ can be freely embedded and removed from the positive electrode material through the passivation film.

SEI膜的形成对电极材料的性能产生至关重要的影响：一方面，SEI膜的形成消耗了部分作为负极材料的Li⁺，使得首次充放电不可逆容量增加，降低了电极材料的首次充放电效率，即库伦效率；另一方面，SEI膜具有有机溶剂不溶性，在有机电解质溶液中能稳定存在，并且溶剂分子不能通过该层钝化膜，从而能有效防止溶剂分子的共嵌入，避免了因溶剂分子共嵌入对电极材料造成的破坏，因而大大提高了电极的循环性能和使用寿命。因此，在锂电池中快速形成稳定的SEI膜有利于锂电池的循环性能、倍率性能和库伦效率的提高。The formation of the SEI film has a crucial influence on the performance of the electrode material: on the one hand, the formation of the SEI film consumes part of the Li ⁺ as the negative electrode material, so that the irreversible capacity of the first charge and discharge is increased, and the first charge and discharge efficiency of the electrode material is lowered. Coulon efficiency; on the other hand, the SEI film is insoluble in organic solvents, stable in organic electrolyte solution, and solvent molecules cannot pass through the passivation film, thereby effectively preventing co-insertion of solvent molecules and avoiding solvent The molecular co-intercalation causes damage to the electrode material, thereby greatly improving the cycle performance and service life of the electrode. Therefore, rapid formation of a stable SEI film in a lithium battery is advantageous for the cycle performance, rate performance, and coulombic efficiency of the lithium battery.

根据本发明的第一方面，提供一种现场合成锂离子导电保护膜的方法，该方法为以碳-硫复合材料为正极的锂硫电池，在首次放电时，将电压降低至1.5V以下，再充电至工作电压。According to a first aspect of the present invention, a method for synthesizing a lithium ion conductive protective film in the field is provided, which is a lithium-sulfur battery using a carbon-sulfur composite material as a positive electrode, and the voltage is lowered to 1.5 V or less during the first discharge. Recharge to the operating voltage.

本发明人发现，将锂硫电池在首次放电时将电压下限降低至正常工作电压以下，优选1.2V或以下，锂硫电池的电化学性能即出现明显提高，且首次放电电压越低，其电化学性能提升越显著。The inventors have found that the lithium-sulfur battery reduces the lower voltage limit to below the normal working voltage during the first discharge, preferably 1.2 V or less, and the electrochemical performance of the lithium-sulfur battery is significantly improved, and the lower the initial discharge voltage, the electricity is The more obvious the chemical performance is improved.

其中，表面未经修饰的碳-硫复合材料(C-S)在首次放电时将电压降至0.8V左右时可以达到该效果，稳定容量为1000mAh/g左右(具体参见实验例7)。 Among them, the surface unmodified carbon-sulfur composite (C-S) can achieve this effect when the voltage is lowered to about 0.8 V during the first discharge, and the stable capacity is about 1000 mAh/g (see Experimental Example 7 for details).

C-S在首次放电时未经低压放电处理，其在正常使用初期时的容量显著下降，在100次循环周期内难以恢复至较高水平，当循环至100周以上时，其电容量稳定在900mAh/g左右(具体参见实验例10)。CS is not treated with low-voltage discharge during the first discharge. Its capacity at the initial stage of normal use is significantly reduced, and it is difficult to return to a higher level in 100 cycles. When it is cycled to more than 100 weeks, its capacity is stable at 900 mAh/ g or so (see Experimental Example 10 for details).

而表面经过修饰的碳-硫复合材料(C-NH₄-S)，在首次放电时将电压降至1.0V时，其稳定容量约为1200mAh/g，而首次放电未经低压放电处理，其稳定容量明显低于经过低压放电处理的材料，仅为1000mAh/g左右，即首次放电时进行低压放电处理，其稳定容量可提高约200mAh/g(具体参见实验例8和实验例9)。The surface-modified carbon-sulfur composite (C-NH ₄ -S) has a stable capacity of about 1200 mAh/g when the voltage is reduced to 1.0 V during the first discharge, and the first discharge is not treated by low-voltage discharge. The stable capacity is significantly lower than that of the low-voltage discharge treated material, which is only about 1000 mAh/g, that is, low-voltage discharge treatment at the first discharge, and the stable capacity can be increased by about 200 mAh/g (see Experimental Example 8 and Experimental Example 9 for details).

碳-硫复合材料的表面在首次使用时进行低压放电处理后可产生变化，由HRSEM(high resolution scanning electron microscope，高分辨率扫描电子显微镜)图明显可见其表面形态发生了变化(具体参见实验例11)，生成了锂离子导电保护膜，颗粒表面明显有物质生成。The surface of the carbon-sulfur composite material can be changed after low-pressure discharge treatment for the first time. The surface morphology is obviously changed by HRSEM (high resolution scanning electron microscope) (see the experimental example for details). 11), a lithium ion conductive protective film is formed, and a substance is formed on the surface of the particle.

同时，C-NH₄-S在首次放电进行低压放电处理后，对其进行XRD检测(具体参见实验例12)，由实验例12可知，生成的硫化锂处于碳骨架的孔中，而未裸露于一级孔或二级孔外。Meanwhile, C-NH ₄ -S low pressure discharge in the first discharge process, subjected to XRD results (see in particular Experimental Example 12), seen from the experimental Example 12, the resultant lithium sulfide in a porous carbon skeleton, without nudity Outside the primary or secondary wells.

然而，锂离子导电保护膜的形成需要Li⁺的参与，从而消耗金属锂，所以本发明提供的方法，其首次充放电过程的库伦效率不高，但随着充放电次数的增加，循环性能不断增强，因此，本发明选择牺牲首次库伦效率得到后续持续较高的库伦效率、循环性能。However, the formation of a lithium ion conductive protective film requires the participation of Li ⁺ , thereby consuming metal lithium. Therefore, the method provided by the present invention has a low coulombic efficiency in the first charge and discharge process, but the cycle performance is constantly increased as the number of charge and discharge times increases. Enhanced, therefore, the present invention chooses to sacrifice the first coulombic efficiency to obtain a subsequent sustained higher coulomb efficiency, cycle performance.

根据本发明的第二～第四方面，提供一种用作上述现场合成锂离子导电保护膜基体的具有多级孔的多孔碳，该多孔碳包括碳骨架，在碳骨架中分布有一级孔和二级孔，其中，一级孔的孔径约为2～10nm，二级孔的孔径约为100～300nm，任选地，在碳骨架表面修饰有羧酸铵基团，在一级孔和二级孔的孔壁表面修饰有羧酸铵基团。According to a second to fourth aspect of the present invention, there is provided a porous carbon having a plurality of pores as a matrix for synthesizing a lithium ion conductive protective film in the above-mentioned manner, the porous carbon comprising a carbon skeleton in which a primary pore is distributed in the carbon skeleton a secondary pore, wherein the primary pore has a pore diameter of about 2 to 10 nm, and the secondary pore has a pore diameter of about 100 to 300 nm, and optionally, a carboxylate group is modified on the surface of the carbon skeleton, in the primary pore and the second The pore wall surface of the pores is modified with an ammonium carboxylate group.

该具有多级孔的多孔碳的透射电镜图如图1a和1b所示，由透射电镜图明显可见，具有多级孔的多孔碳的碳骨架中存在丰富的孔，所述孔包括一级孔和二级孔这两级孔，其中每级孔的孔体积都很均匀，孔径分布集中，其中，一级孔的孔径与一级模板粒子的粒径相对应，二级孔的孔径与二级模板粒子的粒径相对应；同时，该多孔碳的碳骨架壁中也分布有一定数量的微孔，微孔的孔径小于2nm。The transmission electron micrograph of the porous carbon having multi-stage pores is as shown in Figs. 1a and 1b, and it is apparent from the transmission electron micrograph that there are abundant pores in the carbon skeleton of the porous carbon having multi-stage pores, and the pores include the primary pores. And two holes of the secondary hole, wherein the pore volume of each of the holes is uniform, and the pore size distribution is concentrated, wherein the pore size of the first hole corresponds to the particle size of the first template particle, and the pore size of the second hole is two The particle size of the template particles corresponds to each other; meanwhile, a certain number of micropores are distributed in the carbon skeleton wall of the porous carbon, and the pore diameter of the micropores is less than 2 nm.

为使硫磺颗粒可以完全被嵌于多孔碳的一级孔和二级孔中，并为硫磺在充放电过程中产生的体积膨胀预留空间，本发明选择设计两级孔，其中一级孔的孔径约为2～10nm，二级孔的孔径约为100～300nm，由于这些孔是通过将模板粒子与碳源化合物混合，当碳源化合物碳化为碳化产物后，再从碳化产物中去除而形成；而碳骨架中分布的微孔是由于碳源化合物在碳化过程中脱水而不可避免地形成，因此，一级孔、二级孔和微孔可以为通孔和/或盲孔，且一级孔与二级孔在碳骨架中的分布无规则次序，同样，微孔在碳骨架中的分布也无规则次序。In order to allow the sulfur particles to be completely embedded in the primary and secondary pores of the porous carbon, and to reserve space for the volume expansion of sulfur generated during charging and discharging, the present invention selectively designs a two-stage pore, wherein the primary pore The pore size is about 2 to 10 nm, and the pore size of the secondary pore is about 100 to 300 nm. Since the pores are mixed with the carbon source compound by the template particles and the carbon source compound, the carbon source compound is carbonized into a carbonized product, and then removed from the carbonized product. And the micropores distributed in the carbon skeleton are inevitably formed due to dehydration of the carbon source compound during carbonization, and therefore, the primary pores, the secondary pores, and the micropores may be through holes and/or blind holes, and one stage The distribution of the pores and the secondary pores in the carbon skeleton is irregular, and likewise, the distribution of the micropores in the carbon skeleton is also in an irregular order.

为使具有多级孔的多孔碳的孔径略大于硫磺颗粒的粒径，使硫磺颗粒嵌于一级孔或二级孔内，并与其所在孔的孔壁预留有一定的空间，允许硫磺在放电过程中与锂离子化合而引起的体积膨胀，防止由于体积膨胀而引起的多孔碳碳骨架的坍塌，本发明选择在具有多级孔的多孔碳中分布上述两种孔径的孔。In order to make the pore size of the porous carbon with multi-stage pores slightly larger than the particle size of the sulfur particles, the sulfur particles are embedded in the primary pores or the secondary pores, and a certain space is reserved for the pore walls of the pores in which the holes are located, allowing sulfur to be The volume expansion caused by the combination of lithium ions during discharge prevents the collapse of the porous carbon-carbon skeleton due to volume expansion, and the present invention selects pores of the above two pore sizes to be distributed in porous carbon having multi-stage pores.

同时，本发明提供的具有多级孔的多孔碳的碳骨架表面、一级孔和二级孔的孔壁表面可以修饰有羧酸铵基团，该基团可对孔壁表面进行微观改造，修饰在孔壁表面的羧酸铵基团在后续使用时，能够促进锂离子导电保护膜的快速形成。Meanwhile, the surface of the carbon skeleton surface of the porous carbon having the multi-stage pores, the pore walls of the first-order pores and the second-order pores may be modified with an ammonium carboxylate group, and the group may micro-reform the surface of the pore wall. The ammonium carboxylate group modified on the surface of the pore wall can promote rapid formation of the lithium ion conductive protective film in the subsequent use.

根据本发明的第五和第六方面，提供上述具有多级孔的多孔碳的制备方法，该方法包括以下步骤：According to a fifth and sixth aspect of the invention, there is provided a method of producing the above porous carbon having a plurality of stages, the method comprising the steps of:

步骤(1-1)，按重量比为一级模板粒子:二级模板粒子:碳源化合物＝1:(1～3):(2～5)称取一级模板粒子、二级模板粒子和碳源化合物，充分混合均匀，制得混合物。Step (1-1), according to the weight ratio of the first template particles: secondary template particles: carbon source compound = 1: (1 ~ 3): (2 ~ 5) weigh the first template particles, the secondary template particles and The carbon source compound is thoroughly mixed to obtain a mixture.

本发明以碳源化合物为起点，在碳源化合物中掺杂可被酸和/或碱去除的一级模板粒子和二级模板粒子，使得其在高温碳化过程中可将模板粒子均匀的掺杂于碳骨架中，再通过高温碳化使碳源化合物形成碳化产物，同时一级模板粒子、二级模板粒子均匀地分布于碳化产物中，再以化学手段除去模板粒子，使多孔碳中形成分布均匀的一级孔和二级孔，且孔的孔径分布均匀、集中。The invention uses a carbon source compound as a starting point, and the carbon source compound is doped with primary template particles and secondary template particles which can be removed by acid and/or alkali, so that the template particles can be uniformly doped in the high temperature carbonization process. In the carbon skeleton, re-pass The high-temperature carbonization causes the carbon source compound to form a carbonization product, and the primary template particles and the secondary template particles are uniformly distributed in the carbonization product, and the template particles are removed by chemical means to form a uniform distribution of the first-order pores and the second in the porous carbon. The pores are well-disposed, and the pore size distribution of the pores is uniform and concentrated.

本发明选用的碳源化合物为易于碳化的化合物，如固态小分子有机化合物—糖类化合物，这类化合物在常温常压下为固体小颗粒，在通过湿法混合法与其他原料进行混合时，易于形成类似凝胶的含水连续相，从而使模板粒子与糖类化合物均匀混合，进而使得形成的碳骨架中均匀分布有不同孔径的孔；同时，本发明所选用的糖类化合物具有较低的熔点，在100～200℃时即可熔化为液态，从而形成连续相，使其在后续碳化步骤中可以形成连续的碳骨架，优选碳化温度低的糖类化合物，如葡萄糖、蔗糖、鼠李糖等，更优选产量较大、较为常见的蔗糖。The carbon source compound selected in the present invention is a compound which is easy to be carbonized, such as a solid small molecule organic compound-saccharide compound, and the compound is a solid small particle at normal temperature and normal pressure, and is mixed with other raw materials by wet mixing method. It is easy to form a gel-like aqueous continuous phase, so that the template particles and the saccharide compound are uniformly mixed, so that the formed carbon skeleton is evenly distributed with pores having different pore diameters; meanwhile, the saccharide compound selected in the present invention has a lower concentration. The melting point, at 100-200 ° C, can be melted into a liquid state to form a continuous phase, which can form a continuous carbon skeleton in the subsequent carbonization step, preferably a saccharide compound having a low carbonization temperature, such as glucose, sucrose, rhamnose Etc., more preferred is the relatively high yield, more common sucrose.

为制得孔径多样的多孔碳，利于吸附容纳粒径不同的聚硫离子，本发明优选粒径在不同的数量级上的一级模板粒子和二级模板粒子。In order to obtain porous carbon having various pore diameters, which facilitates adsorption of polysulfide ions having different particle diameters, the present invention preferably uses primary template particles and secondary template particles having different particle diameters on different orders of magnitude.

本发明选择一级模板粒子用于形成具有多级孔的多孔碳中的一级孔，该一级模板粒子为粒径约为2～10nm的化合物颗粒，该化合物颗粒在碳化条件下不与碳源化合物、碳化产物或其他模板粒子等其他成分反应，同时，该一级模板粒子易溶于酸和/或碱等试剂，在碳化产物中易于被除去，优选为金属氧化物，如氧化铝、氧化镁等，优选为氧化铝，其粒径约为5nm。The present invention selects a primary template particle for forming a primary pore in a porous carbon having a plurality of pores, the primary template particle being a compound particle having a particle diameter of about 2 to 10 nm, and the compound particle is not carbonized under carbonization conditions. Other components such as a source compound, a carbonized product or other template particles are reacted, and at the same time, the primary template particles are easily dissolved in a reagent such as an acid and/or a base, and are easily removed in the carbonized product, preferably a metal oxide such as alumina. Magnesium oxide or the like is preferably alumina and has a particle diameter of about 5 nm.

本发明选择二级模板粒子用于形成具有多级孔的多孔碳中的二级孔，该二级模板粒子为粒径约为100～300nm的化合物颗粒，该化合物颗粒在碳化条件下不与碳源化合物、碳化产物或其他模板粒子等其他成分反应，同时，该二级模板粒子易溶于酸和/或碱等试剂，在碳化产物中易于被除去，优选为在高温时可以分解产生气体的化合物颗粒，如粒径为100～300nm的碳酸盐化合物颗粒，具体如碳酸钙、碳酸镁等。The present invention selects secondary template particles for forming secondary pores in porous carbon having multi-stage pores, the secondary template particles being compound particles having a particle diameter of about 100 to 300 nm, and the compound particles are not carbonized under carbonization conditions. Other components such as a source compound, a carbonized product or other template particles are reacted, and at the same time, the secondary template particles are easily dissolved in an agent such as an acid and/or a base, and are easily removed in the carbonized product, and are preferably decomposed to generate a gas at a high temperature. The compound particles, such as particles of a carbonate compound having a particle diameter of 100 to 300 nm, specifically, such as calcium carbonate, magnesium carbonate or the like.

在本发明中，碳化条件是指用于形成碳骨架的碳源化合物的碳化条件。In the present invention, carbonization conditions refer to carbonization conditions of a carbon source compound for forming a carbon skeleton.

本发明优选二级模板粒子为碳酸盐化合物颗粒，如纳米碳酸钙、纳米碳酸镁，这些化合物颗粒在高温条件下可以分解为相应的固态氧化物及气态二氧化碳，其中，分解得到的固态氧化物为可被酸去除的金属氧化物，其与酸反应后可以生成易溶于液相的盐，随洗涤液被去除，从而在碳骨架上形成粒径与固态氧化物相当的孔，而分解得到的二氧化碳在逸出体系时能在碳骨架上形成气孔通道，有些大孔会破裂成为类泡沫结构，从而使得多孔碳的孔径多于模板孔径范围。Preferably, the secondary template particles of the present invention are carbonate compound particles, such as nano calcium carbonate and nano magnesium carbonate, and the particles of the compound can be decomposed into corresponding solid oxides and gaseous carbon dioxide under high temperature conditions, wherein the solid oxides obtained by decomposition are obtained. A metal oxide which can be removed by an acid, which reacts with an acid to form a salt which is easily soluble in the liquid phase, and is removed with the washing liquid, thereby forming a pore having a particle diameter equivalent to that of the solid oxide on the carbon skeleton, and decomposing The carbon dioxide can form pore channels on the carbon skeleton when it escapes from the system, and some large pores can be broken into a foam-like structure, so that the porous carbon has a pore diameter larger than the template pore size range.

二级模板粒子更优选纳米碳酸钙，其粒径约为150nm，同时，纳米碳酸钙在碳化温度下可以分解为氧化钙及二氧化碳，其中，氧化钙可以在酸中溶解，生成可溶性钙盐，易于随酸溶液被除去，此外，由碳酸钙在碳化条件下可以分解得到气态二氧化碳，其在逸出未完全碳化的碳化产物时，能够在碳化产物中形成气孔通道，气孔通道孔径较小，从而使制得的碳化产物形成类泡沫结构，并且碳源化合物在碳化过程中会因脱水而在多孔碳的碳骨架壁中形成微孔，对锂硫电池正极材料硫在充放电过程中形成的不同粒径的聚硫离子具有更好的吸附容纳能力。The secondary template particles are more preferably nano calcium carbonate having a particle diameter of about 150 nm. Meanwhile, the nano calcium carbonate can be decomposed into calcium oxide and carbon dioxide at a carbonization temperature, wherein the calcium oxide can be dissolved in the acid to form a soluble calcium salt, which is easy. The acid solution is removed, and in addition, the carbon dioxide can be decomposed under carbonization conditions to obtain gaseous carbon dioxide, which can form a pore passage in the carbonized product when the carbonization product is not completely carbonized, and the pore diameter of the pore passage is small, thereby The obtained carbonized product forms a foam-like structure, and the carbon source compound forms micropores in the carbon skeleton wall of the porous carbon due to dehydration during carbonization, and different particles formed in the lithium-sulfur battery cathode material during charging and discharging The polysulfide ion of the diameter has better adsorption capacity.

本发明中所述的酸或碱为常规的酸试剂或碱试剂，即常见的有机酸、无机酸、有机碱或无机碱，如甲酸、乙酸、盐酸、硫酸、硝酸、磷酸、氨水、氢氧化钠、氢氧化钾等，本发明对上述试剂的浓度不做特别限定，以能够将一级模板粒子和/或其产物、二级模板粒子和/或其产物去除为优选。The acid or base described in the present invention is a conventional acid reagent or an alkali reagent, that is, a common organic acid, inorganic acid, organic base or inorganic base such as formic acid, acetic acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, ammonia water, or hydroxide. The concentration of the above reagent is not particularly limited in the present invention, so that the primary template particles and/or their products, the secondary template particles, and/or their products are preferably removed.

本发明对一级模板粒子、二级模板粒子和碳源化合物的混合方法不做特别限定，如固相干法混合法或液相湿法混合法等，其中，液相湿法混合法具体可以通过以下方式实施：将一级模板粒子、二级模板粒子和碳源化合物置于适量的去离子水当中形成混合溶液，将混合溶液置于70～90℃的油浴锅中搅拌，至溶剂蒸发至干，形成粘稠状混合物，然后再将粘稠状混合物置于160～180℃的烘箱中保温12～24h后，研磨即得混合物。The method for mixing the primary template particles, the secondary template particles and the carbon source compound is not particularly limited, such as a solid phase dry mixing method or a liquid phase wet mixing method, wherein the liquid phase wet mixing method may specifically The method comprises the following steps: placing the primary template particles, the secondary template particles and the carbon source compound in an appropriate amount of deionized water to form a mixed solution, and stirring the mixed solution in an oil bath at 70-90 ° C until the solvent evaporates. To dryness, a viscous mixture is formed, and then the viscous mixture is placed in an oven at 160 to 180 ° C for 12 to 24 hours, and then ground to obtain a mixture.

由于该多孔碳主要是用作锂硫电池正极材料的支撑材料，而正极材料硫磺在充放电过程中会由单质状态经过S₆ ^2-、S₄ ^2-等中间粒子逐步转化为S^2-，这些中间粒子的粒径虽存在差异，但其保持在小于10nm的数量级上，为减少其在电解液中的溶解扩散，设计孔径为2～10nm的一级孔，将中间粒子限制于一级孔内，为了提供数量足够的一级孔来嵌入聚硫粒子，本发明选择粒径为2～10nm的一级模板粒子:碳源化合物(重量比)＝1:(2～5)。Since the porous carbon is mainly used as a support material a lithium-sulfur battery positive electrode material, the positive electrode material during charge and discharge of sulfur will by the elemental state through S ₆ ^{^2-,} S ₄ ^2- and the like gradually transformed into particles of the intermediate S ^2-, Although there are differences in the particle size of these intermediate particles, they are kept on the order of less than 10 nm. In order to reduce the dissolution and diffusion in the electrolyte, a primary pore having a pore diameter of 2 to 10 nm is designed to restrict the intermediate particles to the primary pore. In order to provide a sufficient number of primary pores to embed the polysulfide particles, the present invention selects primary template particles having a particle diameter of 2 to 10 nm: carbon source compound (weight ratio) = 1: (2 to 5).

由于硫磺在放电过程中生成电化学惰性硫化锂伴随着很大的体积膨胀，为避免由于这种体积膨胀而引起的多孔碳骨架结构的坍塌及由于引发的锂硫电池在使用中的不安全因素，本发明选用粒径较大的二级模板粒子，为生成的硫化锂留有空间，允许其在正极材料中的体积膨胀，从而提高锂硫电池的安全性能，因此，本发明选择二级模板粒子与碳源化合物的重量比为二级模板粒子:碳源化合物＝(1～3):(2～5)。Due to the large volume expansion of sulfur generated by the sulfur during the discharge process, in order to avoid the collapse of the porous carbon skeleton structure due to the volume expansion and the unsafe factors in the use of the lithium-sulfur battery The invention selects two-stage template particles with larger particle diameter, leaving space for the generated lithium sulfide, allowing its volume expansion in the positive electrode material, thereby improving the safety performance of the lithium-sulfur battery. Therefore, the present invention selects the secondary template. The weight ratio of the particles to the carbon source compound is secondary template particles: carbon source compound = (1 to 3): (2 to 5).

步骤(1-2)，将步骤(1-1)中制得的混合物在保护性气体保护下，于800～1200℃条件下碳化2～20小时，冷却，得到碳化产物，其中，Step (1-2), the mixture prepared in the step (1-1) is carbonized at a temperature of 800 to 1200 ° C for 2 to 20 hours under a protective gas atmosphere, and cooled to obtain a carbonized product, wherein

所述保护性气体为体积比为按体积比为氢气:氩气＝(1～15):(85～99)的氢气与氩气的混合气。The protective gas is a mixture of hydrogen and argon in a volume ratio of hydrogen: argon = (1 to 15): (85 to 99).

由于本发明选择的碳源化合物为糖类化合物，属于小分子有机化合物，其在高温、氧化性气体共同存在的条件下会生成二氧化碳和水，而不会发生碳化，因此，本发明在对碳源化合物进行碳化时使用保护性气体，该保护性气体为化学惰性气体或具有还原性的气体，或上述两类气体的混合气，如氢气、氮气、氪气、氖气和氩气等，优选氢气和氩气，更优选氢气与氩气的混合气，其体积比为(1～15):(99～85)，优选为(2～10):(98～90)，如5:95，一方面保证在碳化过程中碳源化合物不被氧化而是被碳化，另一方面保证保护气在使用时的安全性。Since the carbon source compound selected by the present invention is a saccharide compound and belongs to a small molecule organic compound, carbon dioxide and water are generated under the condition that high temperature and oxidizing gas coexist, and carbonization does not occur. Therefore, the present invention is in the form of carbon. When the source compound is carbonized, a protective gas is used, and the protective gas is a chemically inert gas or a reducing gas, or a mixed gas of the above two types of gases, such as hydrogen, nitrogen, helium, neon, and argon. Hydrogen and argon, more preferably a mixture of hydrogen and argon, the volume ratio of (1 to 15): (99 to 85), preferably (2 to 10): (98 to 90), such as 5:95, On the one hand, it is ensured that the carbon source compound is not oxidized but carbonized during the carbonization process, and on the other hand, the safety of the shielding gas during use is ensured.

在本发明中，碳骨架的作用主要在于改良硫磺的导电性和碳骨架中分布的一级孔和二级孔对于聚硫离子的吸附容纳能力，因此在保证碳源可以碳化成碳骨架的同时，基于节约能源的角度，选择碳化温度为800℃～1200℃，优选850℃～1000℃，如900℃。In the present invention, the carbon skeleton mainly functions to improve the conductivity of sulfur and the adsorption capacity of the primary and secondary pores distributed in the carbon skeleton for the polysulfide ions, thereby ensuring that the carbon source can be carbonized into a carbon skeleton. From the viewpoint of energy saving, the carbonization temperature is selected from 800 ° C to 1200 ° C, preferably from 850 ° C to 1000 ° C, such as 900 ° C.

在上述碳化温度下，碳化2～20小时即可使碳源化合物碳化完全，优选为5～15小时，更优选为10小时。The carbon source compound can be completely carbonized at a carbonization temperature of 2 to 20 hours, preferably 5 to 15 hours, more preferably 10 hours.

步骤(1-3)，将步骤(1-2)中得到的碳化产物置于酸溶液或碱溶液中，去除一级模板粒子和二极模板粒子，制得具有多级孔的多孔碳。In the step (1-3), the carbonized product obtained in the step (1-2) is placed in an acid solution or an alkali solution to remove the primary template particles and the dipolar template particles to obtain porous carbon having a plurality of pores.

本发明通过酸溶液或碱溶液将包裹于碳化产物中的一级模板粒子、二级模板粒子溶解，从而将其去除，而不会破坏碳化产物的碳骨架结构。The present invention dissolves the primary template particles and the secondary template particles encapsulated in the carbonized product by an acid solution or an alkali solution, thereby removing them without destroying the carbon skeleton structure of the carbonized product.

任选地，包括以下步骤：Optionally, the following steps are included:

步骤(1-4)，将步骤(1-3)中制得的多孔碳基体置于浓硝酸中，在40～70℃下回流5～15小时，分离除去液体，洗涤，用浓氨水浸泡8～20小时，过滤洗涤，干燥，制得表面经过修饰的具有多级孔的多孔碳。Step (1-4), the porous carbon substrate prepared in the step (1-3) is placed in concentrated nitric acid, refluxed at 40 to 70 ° C for 5 to 15 hours, separated and removed, washed, soaked with concentrated ammonia water 8 ～20 hours, filtered and washed, and dried to obtain a surface-modified porous carbon having a plurality of pores.

本发明人研究发现，将多孔碳的一级孔的孔壁表面、二级孔的孔壁表面及碳骨架表面修饰有羧酸铵基团后，多孔碳对硫磺颗粒及聚硫离子的附着容纳效果显著提升，同时，更容易现场合成锂离子导电保护膜，从而提高多孔碳对聚硫粒子的限制作用和对硫磺的利用率，因此，本发明优选在具有多级孔的多孔碳表面进行化学修饰。The present inventors have found that after the surface of the pore wall of the primary pore of the porous carbon, the surface of the pore wall of the secondary pore, and the surface of the carbon skeleton are modified with an ammonium carboxylate group, the porous carbon is attached to the sulfur particle and the polysulfide ion. The effect is remarkably improved, and at the same time, it is easier to synthesize a lithium ion conductive protective film on site, thereby increasing the restriction effect of porous carbon on the polysulfide particles and the utilization of sulfur. Therefore, the present invention preferably performs chemistry on the surface of a porous carbon having a plurality of pores. Modification.

由于具有多级孔的多孔碳表面为碳原子，带有一定数量的碳-氢、碳-羟基基团，因此，本发明在对具有多级孔的多孔碳表面进行修饰时，使用浓的强氧化性酸，如浓硝酸，由于硝酸具有挥发性，可在对多孔碳基体进行修饰后通过加热的方式完全除尽，而其他强氧化性酸或氧化性物质则可能产生残留而对多孔碳的性能造成负面影响，因此，本发明优选浓硝酸作为多孔碳的羧酸化试剂，所用的浓硝酸为市售的发烟硝酸或浓度为65％～86％的发烟硝酸的稀释液，高浓度的硝酸可以氧化碳基体表面官能团，使多孔碳表面形成羧基，而游离的羧基的极性过大，且不稳定，因此用氨水与羧基反应，生成羧酸铵，成盐后提高多孔碳表面的稳定性。Since the surface of the porous carbon having a plurality of pores is a carbon atom with a certain amount of carbon-hydrogen and carbon-hydroxy groups, the present invention uses a strong strong when modifying the surface of a porous carbon having a plurality of pores. Oxidizing acids, such as concentrated nitric acid, can be completely removed by heating after modification of the porous carbon matrix due to the volatility of nitric acid, while other strong oxidizing acids or oxidizing substances may cause residue to the porous carbon. The performance has a negative effect. Therefore, in the present invention, concentrated nitric acid is preferably used as the carboxylating agent for porous carbon, and the concentrated nitric acid used is a commercially available fuming nitric acid or a diluted solution of fuming nitric acid having a concentration of 65% to 86%, and a high concentration. Nitric acid can oxidize the surface functional groups of the carbon matrix to form a carboxyl group on the surface of the porous carbon, and the polarity of the free carboxyl group is too large and unstable. Therefore, the reaction of ammonia water with the carboxyl group produces ammonium carboxylate, and the salt is formed to improve the stability of the porous carbon surface. Sex.

根据本发明的第七方面，提供一种碳-硫复合材料，该碳-硫复合材料包括上述第二～第四方面中任一项所述的具有多级孔的多孔碳和硫磺颗粒，其中硫磺颗粒嵌于具有多级孔的多孔碳的一级孔和二级孔中。According to a seventh aspect of the present invention, a carbon-sulfur composite material comprising the above second - The porous carbon and sulfur particles having a multistage pore according to any one of the fourth aspect, wherein the sulfur particles are embedded in the primary pores and the secondary pores of the porous carbon having the multistage pores.

锂硫电池以硫为正极反应物质，以锂为负极，放电时负极反应为锂失去电子变为锂离子，正极反应为硫与锂离子及电子反应生成硫化物，正极和负极反应的电势差即为锂硫电池所提供的理论放电最高电压；在外加电压作用下，锂硫电池的正极和负极反应逆向进行，即为充电过程。目前，锂硫电池存在以下问题：Lithium-sulfur battery uses sulfur as the positive reaction material and lithium as the negative electrode. When the negative electrode reacts, the negative electrode reacts with lithium, and the electron loses into lithium ion. The positive electrode reacts with sulfur to react with lithium ions and electrons to form sulfide. The potential difference between the positive electrode and the negative electrode is The theoretical discharge maximum voltage provided by the lithium-sulfur battery; under the action of the applied voltage, the positive and negative electrodes of the lithium-sulfur battery react in reverse, which is the charging process. At present, lithium-sulfur batteries have the following problems:

1.放电中间产物聚硫离子可溶解于电解液当中，并且充放电过程中存在的穿梭效应使锂硫电池的库伦效率降低；1. The discharge intermediate polysulfide ion can be dissolved in the electrolyte, and the shuttle effect in the process of charging and discharging reduces the coulombic efficiency of the lithium-sulfur battery;

2.硫磺导电性差，直接使用硫磺作为电池材料会使电池内阻剧烈增大以至于不能正常工作；2. Sulfur conductivity is poor, direct use of sulfur as a battery material will cause the internal resistance of the battery to increase so much that it does not work properly;

3.硫磺在充放电过程中，体积的膨胀和缩小的幅度很大，有可能导致电池损坏。3. During the charging and discharging process, the volume expansion and contraction of the sulfur is large, which may cause damage to the battery.

因此，本发明将作为正极材料的硫磺颗粒嵌入多孔碳的一级孔和二级孔中，使硫磺颗粒嵌在多孔碳的一级孔和二级孔中，并利用硫在孔中的空隙避免由于硫在充放电过程中的体积变化而引起的多孔碳结构的坍塌。Therefore, the present invention embeds sulfur particles as a positive electrode material into the primary pores and secondary pores of the porous carbon, so that the sulfur particles are embedded in the primary and secondary pores of the porous carbon, and the voids in the pores are avoided by using sulfur. The collapse of the porous carbon structure due to the volume change of sulfur during charging and discharging.

本发明中所使用的多孔碳为上述第二～第四方面所述的具有多级孔的多孔碳，其碳骨架内分布有一级孔和二级孔，一方面可以使不同粒径大小的硫磺颗粒嵌于其中，另一方面可以嵌入充放电过程中产生的聚硫离子，阻止聚硫离子在电解液中溶解，从而降低聚硫离子在电解液中穿梭的可能性，进而提高正极材料的循环性能和倍率性能。The porous carbon used in the present invention is the porous carbon having the multi-stage pores described in the above second to fourth aspects, and the primary and secondary pores are distributed in the carbon skeleton, and sulfur of different particle sizes can be obtained on the one hand. The particles are embedded in the film, and on the other hand, the polysulfide ions generated during the charging and discharging process can be embedded to prevent the polysulfide ions from being dissolved in the electrolyte, thereby reducing the possibility of the shuttle of the polysulfide ions in the electrolyte, thereby improving the circulation of the positive electrode material. Performance and rate performance.

硫磺在上述具有多级孔的多孔碳中分散均匀，负载量大，其透射电镜图(TEM)和能谱分析(EDS)如图2a、图2b、图3a和图3b所示(具体参见实验例2、实验例3)，由图2a和图2b明显可见，多孔碳的碳骨架结构保持良好，硫磺很好的分散于多孔碳的孔当中，并与碳骨架中的孔壁具有很好的表面接触；由图3a和图3b可知，硫磺在多孔碳中的分布非常均匀，并与多孔碳的孔内表面接触良好。Sulfur is uniformly dispersed in the above porous carbon with multi-stage pores, and its loading is large. Its transmission electron micrograph (TEM) and energy spectrum analysis (EDS) are shown in Fig. 2a, Fig. 2b, Fig. 3a and Fig. 3b (see the experiment for details). Example 2, Experimental Example 3), as is apparent from Fig. 2a and Fig. 2b, the carbon skeleton structure of the porous carbon is kept good, the sulfur is well dispersed in the pores of the porous carbon, and has a good wall with the pores in the carbon skeleton. Surface contact; as can be seen from Figures 3a and 3b, the distribution of sulfur in the porous carbon is very uniform and is in good contact with the inner surface of the pores of the porous carbon.

本发明提供的多孔碳的一级孔和二级孔表面修饰有羧酸铵基团，从而使得由该多孔碳制得的碳-硫复合材料的电化学性能显著提升。The primary pores and secondary pores of the porous carbon provided by the present invention are modified with an ammonium carboxylate group, so that the electrochemical performance of the carbon-sulfur composite material prepared from the porous carbon is remarkably improved.

本发明提供的碳-硫复合材料将硫磺完全嵌于多孔碳的一级孔和二级孔中(具体参见实验例4)。The carbon-sulfur composite material provided by the present invention completely embeds sulfur in the primary and secondary pores of the porous carbon (see Experimental Example 4 for details).

其XRD图谱中未显示单质硫的特征峰。如图4a和图4b所示，由图4a和图4b对比可知，多孔碳在用羧酸铵进行表面修饰后，其在XRD光谱中的特征峰保持不变，强度也保持稳定，说明多孔碳结构未发生明显变化，多孔碳结构完整，复合硫后形成的碳-硫复合材料，其XRD光谱在2θ角为25°附近的特征峰变得更为尖锐，而2θ角为43°附近的特征峰基本消失，但硫单质的特征峰未出现在碳-硫复合材料的XRD光谱中，这表明硫磺已经嵌入多孔碳的一级孔和二级孔中，与多孔碳具有很好的表面接触。The characteristic peak of elemental sulfur is not shown in the XRD pattern. As shown in Fig. 4a and Fig. 4b, it can be seen from the comparison of Fig. 4a and Fig. 4b that after the surface modification of the porous carbon with ammonium carboxylate, the characteristic peak in the XRD spectrum remains unchanged, and the strength remains stable, indicating that the porous carbon The structure did not change significantly, the porous carbon structure was intact, and the carbon-sulfur composite formed by the composite sulfur had a characteristic curve in which the XRD spectrum became sharper at a 2θ angle of 25°, and the 2θ angle was around 43°. The peaks disappeared substantially, but the characteristic peaks of the sulfur element did not appear in the XRD spectrum of the carbon-sulfur composite, indicating that the sulfur has been embedded in the primary and secondary pores of the porous carbon, and has good surface contact with the porous carbon.

其拉曼光谱如图5a和图5b所示(具体参见实验例5)，由图5a和图5b可知，经过羧酸铵对多孔碳表面进行修饰后或将硫磺颗粒嵌入到多孔碳中形成的碳-硫复合材料，多孔碳的碳骨架结构没有发生明显变化，并且碳-硫复合材料(硫重量分数为61％或者72％)中不存在硫单质的特征峰，说明硫磺已经被载入到多级孔的一级孔和二级孔当中。The Raman spectrum is shown in Fig. 5a and Fig. 5b (see Experimental Example 5 in detail). It can be seen from Fig. 5a and Fig. 5b that the surface of the porous carbon is modified by ammonium carboxylate or the sulfur particles are embedded in the porous carbon. Carbon-sulfur composite material, the carbon skeleton structure of porous carbon did not change significantly, and the characteristic peak of sulfur element was not present in the carbon-sulfur composite material (the sulfur weight fraction was 61% or 72%), indicating that sulfur has been loaded into Among the primary and secondary pores of the multi-stage pore.

其比表面积和孔径相对于多孔碳材料和多孔碳基体均有较大的减小(具体参见实验例6)，这也说明硫磺嵌入了碳-硫复合材料的孔中。Its specific surface area and pore diameter are greatly reduced with respect to both the porous carbon material and the porous carbon substrate (see Experimental Example 6 for details), which also indicates that sulfur is embedded in the pores of the carbon-sulfur composite.

以C-S复合材料作为正极材料的锂硫电池，在首次放电至0.8V以下后，其充放电特性有很大提升，库伦效率也显著提高，当循环至近100周后，其电容量稳定在900mAh/g左右(具体参见实验例7)，如图6a～9b所示。The lithium-sulfur battery with CS composite material as the positive electrode material has greatly improved its charge-discharge characteristics after initial discharge to below 0.8V, and the Coulomb efficiency is also significantly improved. When the cycle reaches nearly 100 weeks, its capacity is stable at 900mAh/ g or so (see Experimental Example 7 for details), as shown in Figures 6a to 9b.

从循环性能上来看，随着循环次数的增加，循环容量逐渐上升并趋于稳定，这表明在锂硫电池的正极表面发生了界面反应，生成了锂离子导电保护膜并且趋于稳定，而放电至低压过程即促使了这一保护膜的迅速形成。From the point of view of cycle performance, as the number of cycles increases, the cycle capacity gradually increases and tends to be stable, which indicates that an interfacial reaction occurs on the positive electrode surface of the lithium-sulfur battery, and a lithium ion conductive protective film is formed and tends to be stable, and the discharge The rapid formation of this protective film is facilitated by the low pressure process.

同样，具有多级孔的多孔碳在其表面经羧酸铵基团修饰后与硫磺复合合成C-NH₄-S 复合材料，在首次放电至1.5V以下，如1.2V或以下后，可以在正常使用中迅速恢复电容量，并具有接近100％的库伦效率(具体参见实验例8)，其电化学性能如图10a～13b所示。Similarly, a porous carbon having a multi-stage pore is synthesized with a sulfuric acid ammonium group to synthesize a C-NH ₄ -S composite material, and after the first discharge to 1.5 V or less, such as 1.2 V or less, The capacity was quickly restored in normal use and had a coulombic efficiency close to 100% (see Experimental Example 8 for details), and its electrochemical performance is shown in Figures 10a to 13b.

与C-S相比，其稳定容量最高可提高200mAh/g，首次放电至1.5V以下，如1.2V或以下时已经可以达到理想的效果，首次放电的低压下限的提高可以降低负极材料金属锂的损耗，同时提高锂的利用率；此外，由实验例8可知，C-NH₄-S作为锂硫电池的正极材料时，较易形成稳定界面，不受理论束缚，本发明人推断这种稳定界面的作用类似于锂离子导电保护膜，多孔碳表面修饰的羧酸铵基团在低压区间的氧化还原反应有助于锂离子导电保护膜的形成。Compared with CS, its stable capacity can be increased by up to 200mAh/g, and the first discharge can be as low as 1.5V. If it is 1.2V or less, the ideal effect can be achieved. The lower limit of the low voltage of the first discharge can reduce the loss of lithium metal of the negative electrode material. At the same time, the utilization rate of lithium is improved; in addition, it can be seen from Experimental Example 8 that when C-NH ₄ -S is used as a positive electrode material for a lithium-sulfur battery, a stable interface is easily formed and is not bound by theory, and the inventors infer this stable interface. The effect is similar to the lithium ion conductive protective film, and the redox reaction of the porous carbon surface-modified ammonium carboxylate group in the low pressure region contributes to the formation of the lithium ion conductive protective film.

基于电学性能的对比和碳-硫复合材料的微观结构，不受任何理论的束缚，本发明人认为，本发明提供的表面经过修饰的具有多级孔的多孔碳可能具有如图25所示的微观结构，其碳骨架表面修饰有羧酸铵基团，基于该结构，本发明人认为在锂硫电池充放电过程中同时存在两种并存的反应机理，一种是锂离子导电保护膜生成保护机理，如图26所示；另一种是惰性硫化锂保护机理，如图27所示。两种机理都可产生一种阻止聚硫离子进入电解液的界面。Based on the comparison of electrical properties and the microstructure of the carbon-sulfur composite, without any theory, the inventors believe that the surface modified porous carbon having multi-stage pores provided by the present invention may have the structure shown in FIG. The microstructure of the carbon skeleton is modified with an ammonium carboxylate group. Based on the structure, the inventors believe that there are two coexisting reaction mechanisms in the charging and discharging process of the lithium-sulfur battery, and one is the protection of the lithium ion conductive protective film. The mechanism is shown in Figure 26; the other is the inert lithium sulfide protection mechanism, as shown in Figure 27. Both mechanisms produce an interface that blocks the entry of polysulfide ions into the electrolyte.

其中，锂离子导电保护膜生成机理为，在首次放电至1.5V时，硫磺已完全转化为惰性的硫化锂，然后以碳基体计算的0.1C电流继续放电，如放电至1.2V或以下，这样多孔碳会有嵌锂反应发生并且伴随着不可逆的锂离子导电保护膜形成反应发生，而且锂离子导电保护膜形成于固液界面，这样就能保证所有的正极颗粒被锂离子导电保护膜包裹，然后在1.5V～2.5V对硫进行充放电时低压形成的锂离子导电保护膜，一方面阻止聚硫离子与电解液的直接接触而溶解于电解液当中，另一方面可以传输锂离子从而不影响正极活性物质硫磺与锂离子之间的电化学反应，整个过程避免了聚硫离子溶解于电解液也避免了聚硫离子在电解液当中的穿梭效应因而电池的库伦效率趋于100％，并且聚硫离子不穿梭沉积于锂片一侧和正极颗粒被锂离子导电保护膜很好的包裹，电化学惰性的硫化锂与导电性锂离子导电保护膜很好的结合提高了正极总体的导电性，这一点从其制得的锂硫电池的阻抗测试结果中可以得到佐证(具体参见实验例15)，因此电池的容量也不发生明显衰减。Among them, the formation mechanism of the lithium ion conductive protective film is that when the first discharge reaches 1.5V, the sulfur is completely converted into inert lithium sulfide, and then the 0.1C current calculated by the carbon matrix continues to discharge, such as discharging to 1.2V or below, The porous carbon has a lithium intercalation reaction and is accompanied by an irreversible lithium ion conductive protective film formation reaction, and a lithium ion conductive protective film is formed at the solid-liquid interface, so that all the positive electrode particles are encapsulated by the lithium ion conductive protective film. Then, the lithium ion conductive protective film formed at a low pressure during charging and discharging of sulfur at 1.5V to 2.5V prevents the polysulfide ions from being directly dissolved in the electrolyte by direct contact with the electrolyte, and on the other hand, can transport lithium ions without Affecting the electrochemical reaction between the sulfur and lithium ions of the positive active material, the whole process avoids the dissolution of the polysulfide ions in the electrolyte and avoids the shuttle effect of the polysulfide ions in the electrolyte, so the coulombic efficiency of the battery tends to 100%, and The polysulfide ions are not shuttled on one side of the lithium sheet and the positive electrode particles are well encapsulated by the lithium ion conductive protective film, electrochemically inert The good combination of lithium sulfide and conductive lithium ion conductive protective film improves the overall conductivity of the positive electrode, which can be confirmed from the impedance test results of the lithium-sulfur battery obtained (see Experimental Example 15 for details). The capacity does not significantly decay.

而惰性硫化锂保护机理为，硫磺在放电形成硫化锂时会有体积膨胀，在充电时体积又有收缩，这样在充放电过程中会有硫磺活性材料的重新分布，再考虑到硫化锂是高度绝缘性这一因素，在具有孔径合适的一级孔和二级孔分布的多孔碳材料当中，在充放电过程中会有一部分硫化锂变为惰性并处于孔内部，导致最终的孔隙度很小以至于聚硫离子不能够逸出到达电解液，成为失活部分，因此同样保证了在充放电过程当中聚硫离子不溶解于电解液，比容量和库伦效率都达到了与上述机理相同的理想结果，并很好地解释了在以普通多孔碳作为支撑材料制得的碳-硫复合材料作为锂硫电池正极材料循环稳定性差的原因。The protective mechanism of the inert lithium sulfide is that the sulfur expands when the discharge forms lithium sulfide, and the volume shrinks during charging, so that there is a redistribution of the sulfur active material during the charging and discharging process, and then the lithium sulfide is highly considered. Insulation is a factor in the porous carbon material with a suitable pore size and secondary pore distribution. During the charge and discharge process, a part of the lithium sulfide becomes inert and is inside the pores, resulting in a small porosity. Therefore, the polysulfide ions can not escape to the electrolyte and become the deactivated part. Therefore, the polysulfide ions are not dissolved in the electrolyte during the charging and discharging process, and the specific capacity and coulombic efficiency are the same as the above mechanism. As a result, the carbon-sulfur composite material prepared by using ordinary porous carbon as a supporting material is well explained as a cause of poor cycle stability of the lithium sulfur battery positive electrode material.

根据本发明的第八方面，提供上述的碳-硫复合材料的制备方法，其特征在于，该方法包括以下步骤：According to an eighth aspect of the present invention, there is provided a method of producing the above-described carbon-sulfur composite material, characterized in that the method comprises the following steps:

步骤(2-1)，将第二～第四方面中所述的具有多级孔的多孔碳与硫磺按照重量比为多孔碳:硫磺＝1：(1～3)混合，研磨，在密封环境中、保护性气体保护下升温至155℃，保温，再在流动保护性气体保护下升温至170～200℃，保温；Step (2-1), mixing the porous carbon having a multi-stage pore according to the second to fourth aspects with sulfur in a weight ratio of porous carbon: sulfur = 1: (1 to 3), grinding, and sealing in a sealed environment Under the protection of protective gas, the temperature is raised to 155 ° C, and the temperature is raised, and then heated to 170-200 ° C under the protection of flowing protective gas, and the temperature is kept;

步骤(2-2)，将步骤(2-1)得到的体系迅速置于空气中冷却；Step (2-2), the system obtained in the step (2-1) is rapidly placed in the air for cooling;

其中，所述保护性气体为，按体积比为氢气:氩气＝(1～15):(85～99)，优选为(2～10):(98～90)，优选为5:95的氢气与氩气的混合气。Wherein, the protective gas is hydrogen in a volume ratio: argon = (1 to 15): (85 to 99), preferably (2 to 10): (98 to 90), preferably 5: 95. a mixture of hydrogen and argon.

由于硫磺具有较低的熔点，其在较低的温度下即可熔为液态，并可气化为气态，因此本发明选择将上述具有多级孔的多孔碳与硫磺混合，在155℃下保温3～8小时，在此温度下液态硫磺的黏度较低，因此在毛细作用下液体硫磺会充分地填充于具有多级孔的多孔碳的一级孔和二级孔中，再将体系温度升高至170～200℃，保温0.5～2小时，提高覆盖于碳骨架表面的硫磺的气化程度，气体硫磺更充分地扩散进入多孔碳的一级孔和二级孔中和/或随同流动的保护性气体进入多孔碳的一级孔和二级孔中，或者伴随流动性气体而被移除于复合材料体系，从而使硫磺能够完全分布于多孔碳的孔中，从而提高其作为锂硫电池正极的电学性能。Since sulfur has a lower melting point, it can be melted into a liquid state at a lower temperature and can be vaporized into a gaseous state. Therefore, the present invention chooses to mix the above porous carbon having a multi-stage pore with sulfur and keep it at 155 ° C. 3 to 8 hours, at this temperature, the viscosity of liquid sulfur is low, so under the action of capillary action, liquid sulfur will be fully filled in the primary and secondary pores of porous carbon with multi-stage pores, and then the temperature of the system will rise. Up to 170-200 ° C, heat preservation for 0.5 to 2 hours, improve the degree of gasification of sulfur covering the surface of the carbon skeleton, gas sulfur diffuses more fully into the primary and secondary pores of the porous carbon and / or The flowing protective gas enters the primary and secondary pores of the porous carbon, or is removed from the composite system with the flow of the gas, thereby allowing the sulfur to be completely distributed in the pores of the porous carbon, thereby enhancing its The electrical properties of the positive electrode of lithium-sulfur battery.

本发明对硫磺的加热方式不做特别限定，以能够实现对体系的密闭加热及通入流动的保护性气体为优选，如管式炉加热等。The heating method of the sulfur in the present invention is not particularly limited, and it is preferable to provide a protective gas for the closed heating and the flow of the system, such as tube furnace heating.

而硫磺具有还原性，其在氧化性物质存在的条件下可被氧化为二氧化硫、三氧化硫或其他含硫化合物，因此，本发明选择在对其进行加热时用保护性气体进行隔氧保护，保护性气体为化学惰性气体或具有还原性的气体，或上述两类气体的混合气，如氢气、氮气、氪气、氖气和氩气等，优选氢气和氩气，更优选氢气与氩气的混合气，其体积比为(1～15):(99～85)，优选为(2～10):(98～90)，如5:95。Sulfur is reductive and can be oxidized to sulfur dioxide, sulfur trioxide or other sulfur-containing compounds in the presence of an oxidizing substance. Therefore, the present invention selectively protects against oxygen by a protective gas when heating it. The protective gas is a chemically inert gas or a reducing gas, or a mixture of the above two types of gases, such as hydrogen, nitrogen, helium, neon, and argon, preferably hydrogen and argon, more preferably hydrogen and argon. The mixture gas has a volume ratio of (1 to 15): (99 to 85), preferably (2 to 10): (98 to 90), such as 5:95.

当气体/液体硫磺在多孔碳的一级孔和二级孔中分散均匀后，快速降温使气体/液体硫磺凝华/凝固结晶，从而使硫磺以固态的形式被嵌于多孔碳的一级孔和二级孔中，本发明选择对体系进行迅速降温处理，如将步骤(2-1)中得到的体系迅速置于空气中，自然冷却，使体系温度降至室温。When the gas/liquid sulfur is uniformly dispersed in the primary and secondary pores of the porous carbon, the rapid cooling causes the gas/liquid sulfur to be desublimed/solidified and crystallized, so that the sulfur is embedded in the first-order pore of the porous carbon in a solid form. In the second and second holes, the present invention selects a rapid cooling treatment of the system. For example, the system obtained in the step (2-1) is quickly placed in the air and naturally cooled to lower the temperature of the system to room temperature.

由于本发明提供的具有多级孔的多孔碳具有适宜的孔径，及丰富的一级孔和二级孔和较大的比表面积，而且，作为支撑材料的多孔碳具有良好的导电性，将导电性差的硫磺分散于其中可以避免硫磺电阻大的问题，因此本发明提供的具有多级孔的多孔碳可以负载更多的硫磺，本发明选择多孔碳与硫磺的重量比为1：(1～3)。Since the porous carbon having multi-stage pores provided by the present invention has a suitable pore diameter, and abundant primary pores and secondary pores and a large specific surface area, and the porous carbon as a supporting material has good electrical conductivity, it will conduct electricity. The poor sulfur is dispersed therein to avoid the problem of large sulfur resistance. Therefore, the porous carbon having multi-stage pores provided by the present invention can carry more sulfur, and the weight ratio of porous carbon to sulfur in the present invention is 1: (1~3) ).

根据本发明的第九方面，提供上述的碳-硫复合材料用于锂-硫电池正极材料的用途。According to a ninth aspect of the invention, there is provided the use of the above-described carbon-sulfur composite material for a lithium-sulfur battery positive electrode material.

将硫磺作为正极的锂硫电池是一种高能量密度的锂离子电池。硫作为电池材料理论容量达到1675mAh/g，平均工作电压为2V左右，能量密度达3350Wh/kg，将高出传统商业电池5倍左右，而且硫还有价格低廉、自然储量丰富和无毒等优点，因此本发明选择将硫磺作为电池的正极材料，由于硫磺的导电性差，单纯将硫磺作为正极材料将会导致整个锂硫电池电阻过大而不能正常工作，通常通过加入大量的炭黑来增加其导电性，这就不可避免的降低了整个正极材料的能量密度；而且硫磺在充放电过程中的中间反应产物聚硫阴离子可以溶解于电解液当中，其在放电过程中会在电场作用下迁移至负极锂金属一侧，并在负极一侧形成惰性的多硫化锂,该多硫化锂将在电池的后续充放电过程中失去电化学活性，即电池的正极材料和负极材料等相关活性物质失活；正极材料硫磺在充放电过程中还会形成难溶性硫化锂，造成体积膨胀，导致锂硫电池使用时的安全隐患，而且会消耗大量负极材料金属锂；而溶解于电解液当中那部分聚硫离子会在放电时向负极一侧迁移，充电时向正极一侧迁移，这种穿梭效应会导致电池的库伦效率低下，能量的利用率降低；此外，硫磺的完全还原产物也是高度绝缘的，随着充放电次数的增多，颗粒在正极一侧的沉积与长大会不可避免的导致某些活性物质失效，这将导致电池容量的衰减与性能的减弱，而本发明提供的碳-硫复合材料可以很好的避免上述问题。A lithium-sulfur battery using sulfur as a positive electrode is a high-energy density lithium ion battery. Sulfur as the battery material theoretical capacity of 1675mAh / g, the average working voltage is about 2V, energy density of 3350Wh / kg, will be about 5 times higher than the traditional commercial battery, and sulfur is also cheap, natural reserves and non-toxic Therefore, the present invention selects sulfur as the positive electrode material of the battery. Due to the poor conductivity of sulfur, simply using sulfur as the positive electrode material will cause the entire lithium-sulfur battery to be too large to work properly, and is usually increased by adding a large amount of carbon black. Conductivity, which inevitably reduces the energy density of the entire positive electrode material; and the intermediate reaction product of sulfur in the charge and discharge process, the polysulfide anion can be dissolved in the electrolyte, which will migrate to the electric field during the discharge process. On the negative side of the lithium metal side, and forming an inert lithium polysulfide on the negative electrode side, the lithium polysulfide will lose electrochemical activity during the subsequent charge and discharge of the battery, that is, the active material of the positive electrode material and the negative electrode material of the battery are deactivated. The positive electrode material sulfur will also form insoluble lithium sulfide during charge and discharge, causing volume expansion, resulting in The safety hazard of lithium-sulfur battery use, and it will consume a large amount of lithium metal as the negative electrode material; and the part of the polysulfide ion dissolved in the electrolyte will migrate to the negative electrode side during discharge, and migrate to the positive electrode side during charging. The effect will cause the coulombic efficiency of the battery to be low and the energy utilization rate to be lowered. In addition, the complete reduction product of sulfur is also highly insulated. As the number of charge and discharge times increases, the deposition and long assembly of the particles on the positive electrode side inevitably lead to some Some of the active materials fail, which will result in a decrease in battery capacity and a decrease in performance, and the carbon-sulfur composite material provided by the present invention can well avoid the above problems.

在放电时S₈逐渐开环形成一系列聚硫阴离子Sn(4≤n≤8)，最终完全被还原成Li₂S或Li₂S₂，充电时物质转化相反。在电池构造中硫作为活性物质处于正极一层，金属锂处于负极一层，理想状态下，电池放电时锂离子脱离锂金属经电解液到达正极与硫磺反应逐渐形成Li₂S或Li₂S₂，电子经外电路到达正极从而完成整个放电过程。本发明提供碳-硫复合材料在首次放电时将电压降低至正常工作电压下限1.5V以下即可使锂硫电池具有较好的长期使用前景，优选将首次放电电压降至0.6～1.2V，更优选为0.7～1.0V，如0.8V，首次放电电压越低，其后期的电化学性能越好。At the time of discharge, S _{8 is} gradually opened to form a series of polysulfide anions Sn (4 ≤ n ≤ 8), which is finally completely reduced to Li ₂ S or Li ₂ S ₂ , and the substance conversion is reversed upon charging. In the battery structure, sulfur is used as the active material in the positive electrode layer, and the metal lithium is in the negative electrode layer. Under ideal conditions, when the battery is discharged, the lithium ions are separated from the lithium metal and reach the positive electrode through the electrolyte to react with sulfur to form Li ₂ S or Li ₂ S _{2 .} The electrons reach the positive electrode through the external circuit to complete the entire discharge process. The invention provides that the carbon-sulfur composite material reduces the voltage to 1.5V below the lower limit of the normal working voltage during the first discharge, so that the lithium-sulfur battery has a good long-term use prospect, and preferably reduces the first discharge voltage to 0.6-1.2V, and more Preferably, it is 0.7 to 1.0 V, such as 0.8 V, and the lower the initial discharge voltage, the better the electrochemical performance in the latter stage.

本发明提供的碳-硫复合材料在低压区间的氧化还原反应有助于锂离子导电保护膜的形成，因为锂离子导电保护膜的形成需要Li⁺的参与，所以会损失首次库伦效率，但从长期来看，电池的库伦效率会在很长的一段循环周期内都趋于理想100％的状态。The redox reaction of the carbon-sulfur composite material provided by the invention in the low pressure interval contributes to the formation of the lithium ion conductive protective film, because the formation of the lithium ion conductive protective film requires the participation of Li ⁺ , so the first coulombic efficiency is lost, but In the long run, the coulombic efficiency of the battery will tend to be 100% ideal for a long period of time.

以本发明提供的碳-硫复合材料作为正极材料制备的锂硫电池具有良好的倍率性能(具体参见实验例13)。 The lithium-sulfur battery prepared by using the carbon-sulfur composite material provided by the present invention as a positive electrode material has good rate performance (see Experimental Example 13 for details).

由实验例13可知，以0.1C的电流大小充放电过程中，锂硫电池的容量趋于稳定，并维持在一个相对较高的水平(约1000mAh/g),在更换至大电流0.5C/1C后，电池容量有小幅度衰减，其衰减值处于一个正常范围，此外，在使用大电流循环时，电池的稳定性良好，在测试圈数内没有发生剧烈的衰减，电池性能稳定。It can be seen from the experimental example 13 that the capacity of the lithium-sulfur battery tends to be stable during the charging and discharging process with a current of 0.1 C, and is maintained at a relatively high level (about 1000 mAh/g), and is replaced with a large current of 0.5 C/. After 1C, the battery capacity has a small attenuation, and its attenuation value is in a normal range. In addition, when using a large current cycle, the stability of the battery is good, no significant attenuation occurs in the test lap, and the battery performance is stable.

同时，由本发明提供的表面经过修饰的碳-硫复合材料作为正极材料制得的锂硫电池具有良好的自放电性能(具体参见实验例14)，其在充放电若干周后进行搁置48小时，其循环性能和库伦效率均未受到影响；其在前期没有充满电再进行搁置处理，再对其进行充放电处理，其循环性能和库伦效率也未受到影响；当搁置时间延长至若干天，锂硫电池的电压也未发生显著变化。Meanwhile, the lithium-sulfur battery prepared by using the surface-modified carbon-sulfur composite material provided by the present invention as a positive electrode material has good self-discharge performance (refer to Experimental Example 14 for details), and it is left for 48 hours after charging and discharging for several weeks. The cycle performance and coulombic efficiency were not affected; it was not fully charged in the early stage and then shelved, and then charged and discharged, its cycle performance and coulombic efficiency were not affected; when the shelf life was extended to several days, lithium The voltage of the sulfur battery did not change significantly.

用本发明提供的表面经过修饰的碳-硫复合材料作为正极材料制得的锂硫电池同时还具有较小的阻抗性能(具体参见实验例15)，在0.8V以下，电池阻抗减少，不受任何理论的束缚，本发明人认为是锂离子导电保护膜的形成提高了绝缘性物质硫化锂的导电性能，从而使电池电阻趋于一个较小的值。The lithium-sulfur battery prepared by using the surface-modified carbon-sulfur composite material provided by the invention as a positive electrode material also has a small impedance performance (see Experimental Example 15 for details), and the battery impedance is reduced below 0.8V. Any theoretical constraint, the inventors believe that the formation of a lithium ion conductive protective film enhances the electrical conductivity of the insulating material lithium sulfide, thereby causing the battery resistance to tend to a small value.

根据本发明提供的现场合成锂离子导电保护膜的新方法、具有多级孔的多孔碳及其制备方法、碳-硫复合材料及其制备方法和该碳-硫复合材料用于锂硫电池正极材料的用途，具有以下优点：Novel method for synthesizing lithium ion conductive protective film in situ according to the present invention, porous carbon having multi-stage pores, preparation method thereof, carbon-sulfur composite material and preparation method thereof, and carbon-sulfur composite material used for positive electrode of lithium sulfur battery The use of materials has the following advantages:

(1)使用低压放电现场合成锂离子导电保护膜的新方法，仅损失首次库伦效率即可实现并长期保持较高的循环性能、倍率性能、库伦效率和较低的自放电性能，从而延长了锂硫电池的使用寿命，降低使用成本，实现资源的充分利用；(1) A new method for synthesizing lithium ion conductive protective film on-site using low-voltage discharge, which can achieve high cycle performance, rate performance, coulombic efficiency and low self-discharge performance only by losing the first coulombic efficiency, thereby prolonging The service life of lithium-sulfur batteries, reduce the cost of use, and realize the full utilization of resources;

(2)该具有多级孔的多孔碳中存在不同孔径的孔，还可以在孔表面修饰有羧酸铵基团，这些不同孔径的孔可对硫磺及锂硫电池在充放电过程中生成的不同粒径的聚硫离子及硫化锂进行包封，使上述微粒被嵌于一级孔和二级孔中，而不溶于电解液中，减少了硫在电解液中的穿梭作用，从而提高锂硫电池的循环性能及倍率性能；(2) The pores having different pore diameters exist in the porous carbon having multi-stage pores, and the ammonium carboxylate groups may be modified on the surface of the pores, and the pores of different pore sizes may be generated during charging and discharging of the sulfur and lithium sulfur batteries. The polysulfide ions of different particle sizes and lithium sulfide are encapsulated, so that the above-mentioned microparticles are embedded in the primary pores and the secondary pores, and are insoluble in the electrolyte, thereby reducing the shuttle effect of sulfur in the electrolyte, thereby increasing lithium Cycle performance and rate performance of sulfur batteries;

(3)该具有多级孔的多孔碳的孔径相对于硫磺颗粒及生成的硫化锂略大，使硫磺颗粒完全嵌于一级孔和二孔中，并与所在孔的孔壁存有一定空间，允许硫在充放电过程中生成硫化锂而引起的体积膨胀，有效防止因体积膨胀而造成的具有多级孔的多孔碳的碳骨架结构坍塌，从而保证锂硫电池使用时的安全性和使用寿命；(3) The pore diameter of the porous carbon having the multi-stage pores is slightly larger than that of the sulfur particles and the generated lithium sulfide, so that the sulfur particles are completely embedded in the first-order pores and the two pores, and a space is reserved with the pore walls of the pores, allowing The volume expansion caused by the formation of lithium sulfide during the charging and discharging process, effectively preventing the collapse of the carbon skeleton structure of the porous carbon having multi-stage pores due to volume expansion, thereby ensuring the safety and service life of the lithium-sulfur battery when used;

(4)制备该具有多级孔的多孔碳的方法简便易行，原料来源广泛，制备成本低，具有工业实用性，同时，用该方法制得的具有多级孔的多孔碳的孔径及其中存在的一级孔和二级孔分布均匀、可控，且孔径可根据需要进行定量合成，该方法不会在具有多级孔的多孔碳中残留模板粒子，成孔率高；(4) The method for preparing the porous carbon having multi-stage pores is simple and convenient, has a wide source of raw materials, low preparation cost, industrial applicability, and pore diameter of porous carbon having multi-stage pores prepared by the method and The first-order pores and the second-order pores are uniformly distributed and controllable, and the pore diameter can be quantitatively synthesized as needed. The method does not leave template particles in the porous carbon having multi-stage pores, and the pore formation rate is high;

(5)用以上具有多级孔的多孔碳制成的碳-硫复合材料中硫磺含量大，可以充分利用硫磺的电容量，而且将具有多级孔的多孔碳作为其支撑材料，可以减轻硫磺由于导电性差而引起的锂硫电池电阻大的问题，同时，利用具有多级孔的多孔碳的孔径略大于硫磺粒径，从而保证了其所制成的锂-硫电池的安全性；(5) The carbon-sulfur composite material made of the above porous carbon having multi-stage pores has a large sulfur content, and can fully utilize the capacity of sulfur, and the porous carbon having multi-stage pores can be used as a supporting material to reduce sulfur. The problem of large resistance of the lithium-sulfur battery due to poor conductivity, and at the same time, the pore diameter of the porous carbon having the multi-stage pores is slightly larger than the sulfur particle diameter, thereby ensuring the safety of the lithium-sulfur battery produced thereby;

(6)制备上述碳-硫复合材料的方法简便、利用硫的物理性质即可快速制得，不需要经过化学反应，绿色环保。(6) The method for preparing the above carbon-sulfur composite material is simple and can be quickly obtained by utilizing the physical properties of sulfur, and does not require a chemical reaction, and is environmentally friendly.

实施例Example

实施例1具有多级孔的多孔碳的制备Example 1 Preparation of Porous Carbon with Multistage Pores

(1)按照质量比1:2:3分别称取6g纳米Al₂O₃、12gCaCO₃和18g蔗糖溶于水中，磁力搅拌均匀，80℃油浴保温至体系中溶剂水蒸发至干，移除磁子将体系转移至烘箱，180℃放置12h，研磨样品，制得混合物；(1) Weigh 6g nano-Al ₂ O ₃ , 12gCaCO ₃ and 18g sucrose in water according to mass ratio 1:2:3, stir in water, stir evenly in 80°C oil bath until the solvent water in the system evaporates to dry, remove The magnetic body transferred the system to an oven, placed at 180 ° C for 12 h, and the sample was ground to prepare a mixture;

(2)将步骤1中制得的混合物置于管式炉中，在H₂/Ar(5:95)流动气氛保护(流速50ml/min)、900℃下碳化8h，自然冷却，制得碳化产物；(2) The mixture prepared in the step 1 was placed in a tube furnace, and subjected to H ₂ /Ar (5:95) flow atmosphere protection (flow rate 50 ml/min), carbonized at 900 ° C for 8 hours, and naturally cooled to obtain carbonization. product;

(3)将步骤2中制得的碳化产物置于盐酸(4.5mol/L)中搅拌12h，移除模板CaCO₃，洗涤后将产物置于10mol/L的NaOH溶液中85℃下回流24h，移除模板Al₂O₃，再经离心、洗涤、干燥，制得具有多级孔的多孔碳，记为C。(3) The carbonized product obtained in the step 2 was placed in hydrochloric acid (4.5 mol/L) and stirred for 12 h, and the template CaCO _{3 was} removed. After washing, the product was placed in a 10 mol/L NaOH solution at 85 ° C for 24 h. The template Al ₂ O _{3 was} removed, and then centrifuged, washed, and dried to obtain a porous carbon having a multistage pore, which was designated as C.

实施例2表面经过修饰的具有多级孔的多孔碳的制备Example 2 Preparation of Surface Modified Porous Carbon with Multistage Pores

(4)将步骤3中制得的多孔碳基体置于适量的浓硝酸中，在50℃下回流8h，离心移除液相物质，用去离子水洗涤后，再用浓氨水浸泡12h，再以洗涤、真空干燥即得到具有多级孔的多孔碳材料，记为C-NH₄。(4) The porous carbon substrate prepared in the step 3 is placed in an appropriate amount of concentrated nitric acid, refluxed at 50 ° C for 8 h, centrifuged to remove the liquid phase, washed with deionized water, and then immersed in concentrated ammonia for 12 h, and then A porous carbon material having a plurality of stages of pores was obtained by washing and vacuum drying, and was designated as C-NH ₄ .

实施例3表面未经修饰的碳-硫复合材料的制备Example 3 Preparation of surface unmodified carbon-sulfur composite

(1)按照质量比1:2分别称取实施例1中制得的具有多级孔的多孔碳0.1g和硫磺0.2g，将其研磨混合后，置于管式炉中，在保护性气体H₂/Ar(5:95)气氛下1h内升温至155℃，保温5h，然后在流动保护性气体H₂/Ar(5:95)条件下(流速50ml/min)0.5h升温至180℃后保温1h；(1) 0.1 g of porous carbon having multistage pores and 0.2 g of sulfur obtained in Example 1 were weighed according to a mass ratio of 1:2, ground and mixed, and placed in a tube furnace in a protective gas The temperature was raised to 155 ° C in H ₂ /Ar (5:95) atmosphere for 1 h, and then heated to 180 ° C under the condition of flowing protective gas H ₂ /Ar (5:95) (flow rate 50 ml/min) 0.5 h. After heat preservation for 1h;

(2)保温结束后立即将体系从管式炉中取出，置于空气中自然冷却，即得到碳-硫复合材料，记为C-S。(2) Immediately after the end of the heat preservation, the system was taken out from the tube furnace and naturally cooled in the air to obtain a carbon-sulfur composite material, which was recorded as C-S.

实施例4表面经过修饰的碳-硫复合材料的制备Example 4 Preparation of surface modified carbon-sulfur composite

本对比例与实施例3所用方法相同，区别仅在于所用具有多级孔的多孔碳为实施例2中制备的表面经过修饰的具有多级孔的多孔碳，记为C-NH₄-S(1)。This comparative example was the same as that used in Example 3 except that the porous carbon having a multistage pore was used as the surface-modified porous carbon having a multistage pore prepared in Example 2, which was designated as C-NH ₄ -S ( 1).

通过测量坩埚前后质量的变化来求得复合材料中硫磺的质量分数，测得本实验中硫磺质量分数大约为61％。The mass fraction of sulfur in the composite was determined by measuring the change in mass before and after the crucible, and the sulfur mass fraction in this experiment was determined to be about 61%.

实施例5表面经过修饰的碳-硫复合材料的制备Example 5 Preparation of surface modified carbon-sulfur composite

本实施例与实施例3所用方法相同，区别仅在于实施例2中制备的表面经过修饰的具有多级孔的多孔碳与硫磺的质量比为1:3，用与实施例4相同的方法测得碳-硫复合材料中硫磺的质量分数约为72％，记为C-NH₄-S(2)。This example is the same as the method used in Example 3 except that the mass ratio of the porous carbon having a multistage pore having a surface modified in Example 2 to sulfur is 1:3, and the same method as in Example 4 is used. The mass fraction of sulfur in the carbon-sulfur composite was about 72%, which was recorded as C-NH ₄ -S (2).

实验例Experimental example

(一)在实验例中，所用锂硫纽扣电池按照下述方法制作：(1) In the experimental example, the lithium-sulfur button battery used was produced as follows:

按照质量比为活性物质:碳黑:PVDF粘结剂＝7:1:2比例将上述三种物质混均制备成浆料，并涂覆于铜箔之上，涂布器选用250μm或者300μm，真空干燥后压片，制得电极片，再组装成为纽扣电池，其中，According to the mass ratio of active material: carbon black: PVDF binder = 7:1:2 ratio, the above three substances are mixed and prepared into a slurry, and coated on copper foil, and the applicator is selected to be 250 μm or 300 μm. After vacuum drying, the sheet is pressed to obtain an electrode sheet, which is then assembled into a button battery, wherein

活性物质是指在各实验例中具体所用的碳-硫复合材料。The active material means a carbon-sulfur composite material specifically used in each experimental example.

PVDF粘结剂是指聚偏二氟乙烯粘结剂。The PVDF binder refers to a polyvinylidene fluoride binder.

在实验例中，电池容量按照硫的重量计算，充放电电流大小按照硫理论容量1675mAh/g计算，0.1C表示每毫克硫电流大小为0.1675mA；低压区间按照碳-硫复合材料中碳元素的重量计算，理论容量取350mAh/g，实际电流大小也按照相应碳元素的重量计算，0.1C表示每毫克碳电流大小为0.035mA，本实验中低压充放电电流均为按照相应碳含量取0.1C电流值大小，其中，低压是指低于正常工作电压的电压。In the experimental example, the battery capacity is calculated according to the weight of sulfur. The charge and discharge current is calculated according to the theoretical capacity of sulfur of 1675 mAh/g, 0.1 C is 0.1675 mA per milligram of sulfur current, and the low pressure interval is according to carbon in the carbon-sulfur composite. According to the weight calculation, the theoretical capacity is 350mAh/g, and the actual current is also calculated according to the weight of the corresponding carbon element. 0.1C means that the current per milligram of carbon current is 0.035mA. In this experiment, the low-voltage charge and discharge current is 0.1C according to the corresponding carbon content. The magnitude of the current value, where low voltage refers to a voltage lower than the normal operating voltage.

实验例1具有多级孔的多孔碳的透射电镜图(TEM)Experimental Example 1 Transmission electron micrograph (TEM) of porous carbon having multistage pores

将实施例2制备的样品进行TEM测试，在不同放大倍数下得到的电镜图如图1a和图1b所示。The samples prepared in Example 2 were subjected to TEM testing, and electron micrographs obtained at different magnifications are shown in Figures 1a and 1b.

由图1a和图1b明显可见，实施例2制备的多孔碳中的孔分为两级，分别对应于纳米CaCO₃和Al₂O₃的粒径尺寸，同时，由于在高温灼烧蔗糖使之碳化过程中，纳米CaCO₃会分解生成气态CO₂，因此大的孔会被破裂成为类泡沫结构，由图1b可见，在多孔碳的骨架壁上存在微孔和气孔通道。It can be clearly seen from Fig. 1a and Fig. 1b that the pores in the porous carbon prepared in Example 2 are divided into two stages corresponding to the particle size of the nano CaCO ₃ and Al ₂ O ₃ , respectively, and at the same time, due to the burning of sucrose at a high temperature. During the carbonization process, the nano-CaCO ₃ decomposes to form gaseous CO ₂ , so the large pores are broken into a foam-like structure. As can be seen from Fig. 1b, micropores and pore channels exist on the skeleton wall of the porous carbon.

实验例2碳-硫复合材料的透射电镜图(TEM)Experimental Example 2 Transmission electron micrograph (TEM) of carbon-sulfur composite

将实施例4制备的样品进行TEM测试，在不同放大倍数下得到的电镜图如图2a和图2b所示。The samples prepared in Example 4 were subjected to TEM testing, and electron micrographs obtained at different magnifications are shown in Figures 2a and 2b.

从图2a和图2b中可以看出，多孔碳的碳骨架结构保持良好，硫磺颗粒很好的分散于多孔碳的孔径当中，并与碳骨架的孔壁表面具有很好的表面接触。 It can be seen from Fig. 2a and Fig. 2b that the carbon skeleton structure of the porous carbon is kept good, and the sulfur particles are well dispersed in the pore diameter of the porous carbon and have good surface contact with the pore wall surface of the carbon skeleton.

实验例3碳-硫复合材料的能谱分析(EDS)Experimental Example 3 Energy Spectrum Analysis (EDS) of Carbon-Sulfur Composites

对实施例4制备的样品进行能谱分析，其中高分辨电镜图如图3a所示，与其对应的EDS图如图3b所示，其中，绿色部分代表在分析区域内硫元素的分布。The sample prepared in Example 4 was subjected to energy spectrum analysis, wherein the high-resolution electron microscope image is shown in Fig. 3a, and the corresponding EDS pattern is shown in Fig. 3b, wherein the green portion represents the distribution of sulfur element in the analysis region.

由图3a和图3b可知，硫磺颗粒在多孔碳中的分布非常均匀，并与多孔碳的孔内表面接触良好。As can be seen from Fig. 3a and Fig. 3b, the distribution of the sulfur particles in the porous carbon is very uniform and is in good contact with the inner surface of the pores of the porous carbon.

实验例4碳-硫复合材料的XRD光谱认定Experimental Example 4 XRD Spectroscopic Determination of Carbon-Sulfur Composites

本实验例所用样品为实施例2(曲线a)、实施例4(曲线b)、实施例1(曲线c)和硫磺单质(图4b)，对上述四种样品进行XRD测定，测定结果如图4a和图4b所示。The samples used in this experimental example were Example 2 (curve a), Example 4 (curve b), Example 1 (curve c), and sulfur element (Fig. 4b). The above four samples were subjected to XRD measurement, and the results were as shown in the figure. 4a and Figure 4b.

由图4a和图4b对比可知，多孔碳基体在用羧酸铵进行表面修饰后，其在XRD光谱中的特征峰保持不变，强度也保持稳定，说明多孔碳结构未发生明显变化，多孔碳结构完整，复合硫形成碳-硫复合材料后，其XRD光谱在2θ角为25°附近的特征峰变得更为尖锐，而2θ角为43°附近的特征峰基本消失，但硫单质的特征峰未出现在碳-硫复合材料的XRD光谱中，这表明硫磺颗粒已经被嵌于多孔碳的一级孔和二级孔中，与多孔碳的孔壁具有很好的表面接触。It can be seen from the comparison of Fig. 4a and Fig. 4b that the characteristic peak of the porous carbon matrix in the XRD spectrum remains unchanged after the surface modification with ammonium carboxylate, and the strength remains stable, indicating that the porous carbon structure has not changed significantly, and the porous carbon When the structure is complete and the composite sulfur forms a carbon-sulfur composite, the characteristic peak of the XRD spectrum near 25° of 2θ angle becomes sharper, and the characteristic peak near the angle of 2θ is almost disappeared, but the characteristics of sulfur element The peak did not appear in the XRD spectrum of the carbon-sulfur composite, indicating that the sulfur particles have been embedded in the primary and secondary pores of the porous carbon with good surface contact with the pore walls of the porous carbon.

实验例5碳-硫复合材料的拉曼光谱认定Experimental Example 5 Raman Spectroscopic Determination of Carbon-Sulfur Composites

本实验例所用样品为实施例2(曲线a)、实施例3(曲线b)、实施例4(曲线c)、实施例1(曲线d)和单质硫(图5b)，对上述四种样品进行Raman(拉曼)测定，结果如图5a和图5b所示。The samples used in this experimental example are Example 2 (curve a), Example 3 (curve b), Example 4 (curve c), Example 1 (curve d), and elemental sulfur (Fig. 5b) for the above four samples. The Raman (Raman) measurement was carried out, and the results are shown in Fig. 5a and Fig. 5b.

由图5a和图5b可知，经过羧酸铵基团对多孔碳的碳骨架表面和孔壁表面进行修饰后或将硫磺嵌入到修饰后的多孔碳中形成碳-硫复合材料之后，多孔碳的碳骨架结构没有发生明显变化，并且碳-硫复合材料(硫重量分数为61％或者72％)中不存在硫单质的特征峰，说明硫单质已经被嵌入到多级孔的一级孔和二级孔当中。5a and 5b, after the modification of the carbon skeleton surface and the pore wall surface of the porous carbon by the ammonium carboxylate group or the embedding of the sulfur into the modified porous carbon to form the carbon-sulfur composite material, the porous carbon There is no significant change in the carbon skeleton structure, and the characteristic peak of sulfur element is not present in the carbon-sulfur composite material (the sulfur weight fraction is 61% or 72%), indicating that the sulfur element has been embedded in the first-order pores and two of the multi-stage pores. Among the holes.

实验例6碳-硫复合材料比表面积(BET)测定Experimental Example 6 Determination of specific surface area (BET) of carbon-sulfur composites

本实验例所用样品为实施例2、实施例1和实施例3，对上述三种样品进行BET测定，其BET测定数据如下表1所示。The samples used in the experimental examples were Example 2, Example 1 and Example 3, and the above three samples were subjected to BET measurement, and the BET measurement data are shown in Table 1 below.

由表1可知，多孔碳基体在经羧酸铵修饰后，其比表面积有所减小，由476.3m²/g减小到361.9m²/g，孔体积减小明显，由1.259cc/g减少至0.900cc/g，当碳骨架中嵌入单质硫，形成碳-硫复合材料后，其比表面积减小至26.14m²/g、孔体积减小至0.091cc/g，和孔半径减小至1.88nm，均有明显减小，这也说明单质硫嵌入了碳-硫复合材料的孔中。It can be seen from Table 1 that the specific surface area of the porous carbon matrix is reduced from 476.3 m ² /g to 361.9 m ² /g after modification with ammonium carboxylate, and the pore volume decreases significantly from 1.259 cc/g. Reduced to 0.900 cc / g, when the elemental sulfur is embedded in the carbon skeleton, the specific surface area is reduced to 26.14 m ² /g, the pore volume is reduced to 0.091 cc / g, and the pore radius is reduced after the carbon-sulfur composite is formed. At 1.88 nm, there is a significant decrease, which also indicates that elemental sulfur is embedded in the pores of the carbon-sulfur composite.

表1碳材料BET数据Table 1 carbon material BET data

实验例7 C-S复合材料低压成膜后充放电曲线及库伦效率测定Experimental Example 7 Charging and discharging curves and coulombic efficiency of C-S composites after low pressure film formation

本实验例所用样品为实施例4(硫重量分数64.44％)中制备的碳-硫复合材料。The sample used in this experimental example was a carbon-sulfur composite prepared in Example 4 (sulfur weight fraction 64.44%).

实验操作步骤：Experimental steps:

选取四块纽扣电池首次放电电压分别降至1.0V、0.9V、0.8V和0.7V，分别测定其充放电曲线及循环性能曲线，其结果分别对应图6a～6b、图7a～7b、图8a～8b和图9a～9b，由图6a～9b可知：The first discharge voltage of four button batteries was reduced to 1.0V, 0.9V, 0.8V and 0.7V, respectively. The charge-discharge curves and cycle performance curves were measured. The results correspond to Figures 6a-6b, Figures 7a-7b and Figure 8a, respectively. ～8b and Figs. 9a-9b, as can be seen from Figures 6a to 9b:

C-S复合材料在首次放电至0.8V以下后，以其作为正极材料的锂硫电池的充放电特性有很大提升，库伦效率也显著提高，当循环至近100周后，其电容量稳定在900mAh/g左右。After the first discharge of the CS composite material to 0.8V or less, the charge-discharge characteristics of the lithium-sulfur battery as the positive electrode material are greatly improved, and the Coulomb efficiency is also significantly improved. When the cycle is nearly 100 weeks, the capacitance is stabilized at 900 mAh/ g or so.

从循环性能曲线上来看，随着循环次数的增加，循环容量逐渐趋于上升并趋于稳定，这表明发生了界面反应合成了锂离子导电保护膜并且趋于稳定，而放电至低压过程促使这一锂离子导电保护膜的迅速形成。 From the cycle performance curve, as the number of cycles increases, the cycle capacity gradually increases and tends to be stable, which indicates that the interfacial reaction has synthesized a lithium ion conductive protective film and tends to be stable, and the discharge to low pressure process promotes this. Rapid formation of a lithium ion conductive protective film.

实验例8 C-NH₄-S复合材料低压成锂离子导电保护膜后充放电曲线及库伦效率测定Experimental Example 8 Charging and discharging curves and coulombic efficiency of C-NH ₄ -S composites after low-voltage lithium ion conductive protective film

本实验例操作步骤与实验例7相同，区别仅在所用样品为实施例4制备的样品，所得实验结果分别对应图10a～10b、图11a～11b、图12a～12b和图13a～13b所示。The operation procedure of this experimental example is the same as that of Experimental Example 7, except that the sample used is the sample prepared in Example 4, and the obtained experimental results correspond to those shown in Figs. 10a to 10b, Figs. 11a to 11b, Figs. 12a to 12b, and Figs. 13a to 13b, respectively. .

由图10a～图13b可知，当首次放电电压降至1.0V时，其比容量在10个循环周期以内即可迅速趋于稳定，且稳定电容约为1200mAh/g，较普通碳-硫复合材料提高约200mAh/g。It can be seen from Fig. 10a to Fig. 13b that when the first discharge voltage is reduced to 1.0V, the specific capacity can be stabilized stably within 10 cycles, and the stable capacitance is about 1200 mAh/g, which is higher than ordinary carbon-sulfur composite materials. Increase by about 200 mAh/g.

实验例9 C-NH₄-S复合材料未经低压成锂离子导电保护膜处理充放电曲线及库伦效率测Experimental Example 9 Charging and discharging curves and coulombic efficiency of C-NH ₄ -S composites without lithium-ion conductive protective film 定set

本实验例所用样品为实施例4制备的样品，操作步骤与实验例8相同，区别仅在于首次放电时不经低压放电处理，所得实验结果如图14a和图14b所示。The sample used in this experimental example was the sample prepared in Example 4. The procedure was the same as in Experimental Example 8, except that the first discharge was not subjected to low-pressure discharge treatment, and the obtained experimental results are shown in Figs. 14a and 14b.

由图14a和图14b可知，电池的电容在约前50个循环周期中不稳定，其稳定电容约为1000mAh/g。As can be seen from Figures 14a and 14b, the capacitance of the battery is unstable for about the first 50 cycle periods, and its stable capacitance is about 1000 mAh/g.

实验例10 C-S复合材料未经低压成锂离子导电保护膜处理充放电曲线及库伦效率测定Experimental Example 10 C-S composite material without charge and lithium ion conductive protective film treatment charge and discharge curve and coulombic efficiency determination

本实验例所用样品为实施例3制备的样品，操作步骤与实验例8相同，区别仅在于首次放电时不经低压放电处理，所得实验结果如图15a和图15b所示。The sample used in this experimental example was the sample prepared in Example 3. The procedure was the same as in Experimental Example 8, except that the first discharge was not subjected to low-pressure discharge treatment, and the obtained experimental results are shown in Figs. 15a and 15b.

由图15a和图15b可知，电池的电容在约前100个循环周期中电容极不稳定，电容量损失大，其稳定电容约为900mAh/g。As can be seen from Fig. 15a and Fig. 15b, the capacitance of the battery is extremely unstable in the first 100 cycle periods, and the capacitance loss is large, and the stable capacitance is about 900 mAh/g.

实验例11不同低电压状态的HRSEM测定Experimental Example 11 HRSEM Determination of Different Low Voltage States

本实验例所用样品为实施例4中制备，所用电极片为(一)中方法制作。The sample used in this experimental example was prepared in Example 4, and the electrode sheet used was produced by the method (1).

在不同低电压状态的HRSEM图像如下图16a～图16d所示，图16a～图16d分别对应电极片初始状态、放电至1.5V、1.0V和0.8V时的HRSEM电镜图片，对比可以发现低压区间在颗粒表面明显有物质生成，该物质为上文所述的锂离子导电保护膜，充当保护聚硫离子不脱离正极而溶解于电解液的作用。The HRSEM images in different low-voltage states are shown in Figure 16a to Figure 16d. Figures 16a to 16d correspond to HRSEM images of the initial state of the electrode sheets and discharges to 1.5V, 1.0V and 0.8V, respectively. There is a significant substance formation on the surface of the particles, which is a lithium ion conductive protective film as described above, which acts to protect the polysulfide ions from dissolving in the electrolyte without leaving the positive electrode.

实验例12低电压下碳-硫材料的XRD图Experimental Example 12 XRD pattern of carbon-sulfur material at low voltage

将实施例3和实施例4制得的样品作为正极的锂硫电池放电至不同电压状态，正极极片的XRD图谱如下图17a～17d所示，The samples prepared in Example 3 and Example 4 were discharged as lithium sulphur batteries of the positive electrode to different voltage states, and the XRD patterns of the positive electrode tabs are as shown in Figs. 17a to 17d.

其中，图17a为C-S复合材料在放电至不同电压下的XRD图；Wherein, Figure 17a is an XRD pattern of the C-S composite material discharged to different voltages;

图17b为C-NH₄-S(1)复合材料在放电至不同电压下的XRD图；Figure 17b is an XRD pattern of the C-NH ₄ -S(1) composite material discharged to different voltages;

图17c为C-S复合材料在不同循环次数下的XRD图，其中，曲线5表示循环5周，曲线10表示循环10周，曲线20表示循环20周；Figure 17c is an XRD pattern of the C-S composite at different cycle times, wherein curve 5 represents a cycle of 5 weeks, curve 10 represents a cycle of 10 weeks, and curve 20 represents a cycle of 20 weeks;

图17d为C-NH₄-S(1)复合材料在不同循环次数下的XRD图，其中，曲线5表示循环5周，曲线10表示循环10周，曲线20表示循环20周。Figure 17d is a C-NH ₄ -S (1) composites at different cycles XRD pattern, wherein curve 20 represents the cycle represents a cycle of 5 weeks 5, curve 10 represents the 10 cycles, the curve 20 weeks.

测试环境为空气气氛，从图中17a～17d可以看出随着不同低压放电状态或者不同循环次数均未出现硫化锂的峰而且铜集流体的峰没有发生明显变化，说明电化学反应生成的硫化锂处于碳孔当中和锂离子导电保护膜没有XRD信号。The test environment is air atmosphere. It can be seen from 17a to 17d in the figure that the peak of lithium sulfide does not appear with different low-pressure discharge states or different cycles, and the peak of copper current collector does not change significantly, indicating the vulcanization formed by electrochemical reaction. Lithium is in the carbon pores and the lithium ion conductive protective film has no XRD signal.

实验例13碳-硫复合材料的倍率性能测试Experimental Example 13 Rate Performance Test of Carbon-Sulfur Composites

本实验例对实施例4制得的样品的倍率分别测试了0.5C和1C的倍率性能，结果如图18a～图21b所示。In the experimental example, the magnifications of the samples prepared in Example 4 were tested for the rate performance of 0.5 C and 1 C, respectively, and the results are shown in Figs. 18a to 21b.

在循环间隔为1min的情况下倍率性能良好，稳定性也达到了理想的效果，库伦效率为100％。The ratio performance is good at a cycle interval of 1 min, and the stability is also achieved with an ideal effect, and the Coulomb efficiency is 100%.

采用C-NH₄-S复合材料组装纽扣电池的倍率测试，结果如图18a～图19b所示，具体测试方法为：The magnification test of the button battery was assembled by using C-NH ₄ -S composite material, and the results are shown in Fig. 18a to Fig. 19b. The specific test method is as follows:

首次放电时放电至1.0V低压，并恢复正常测试电压1.5V～2.5V后以0.1C电流大小充放电10圈，然后以0.5C(图18a及图18b)/1C(图19a及图19b)电流大小充放电。Discharge to 1.0V low voltage during the first discharge, and restore the normal test voltage 1.5V ~ 2.5V, then charge and discharge 10 turns with 0.1C current, then 0.5C (Figure 18a and 18b) / 1C (Figure 19a and Figure 19b) The current is charged and discharged.

由图18a～图19b中可看出，在0.1C的充放电过程中电池容量既趋于稳定并维持在一个相对较高的水平(约1000mAh/g),在更换至大电流0.5C/1C后容量有所衰减但是相对较小，减少值处于一个正常范围，重要的是大电流循环稳定性很好，在测试圈数内没有发生剧烈的衰减。因此，本发明碳-硫复合材料的倍率性能优异，可以作为动力电池的正极材料。It can be seen from Fig. 18a to Fig. 19b that the battery capacity tends to be stable and maintained at a relatively high level (about 1000 mAh/g) during the charging and discharging process of 0.1 C, and is replaced with a large current of 0.5 C/1 C. After the capacity is attenuated but relatively small, the reduction value is in a normal range. It is important that the high current cycle is very stable and does not occur within the test lap. Intense attenuation. Therefore, the carbon-sulfur composite material of the present invention is excellent in rate performance and can be used as a positive electrode material for a power battery.

当首次放电时不进行低压放电过程，其倍率性能结果如图20a～图21b所示，具体测试方法与上述方法相同，区别仅在于首次放电时不进行低压放电处理。When the first discharge is performed, the low-pressure discharge process is not performed, and the rate performance results are shown in Figs. 20a to 21b. The specific test method is the same as the above method, except that the low-voltage discharge treatment is not performed at the first discharge.

由图20a～图21b可知，在0.1C测试过程中电池容量有所衰减，在更换至大电流测试过程中又趋于稳定。It can be seen from Fig. 20a to Fig. 21b that the battery capacity is attenuated during the 0.1C test and tends to be stable during the replacement to the high current test.

对比上述两种处理结果，可以得出结论：低压放电有助于锂离子导电保护膜的迅速形成，故进行首次放电时进行低压放电处理可以显著提升锂硫电池的循环稳定性和寿命。Comparing the above two treatment results, it can be concluded that the low-voltage discharge contributes to the rapid formation of the lithium ion conductive protective film, so the low-voltage discharge treatment during the first discharge can significantly improve the cycle stability and life of the lithium-sulfur battery.

实验例14碳-硫复合材料为正极的锂硫电池的自放电性能测试Experimental Example 14 Self-discharge performance test of lithium-sulfur battery with carbon-sulfur composite as positive electrode

将实施例4中制得的碳-硫复合材料作为正极制备锂硫电池，在不同条件下测定其自放电性能，结果如图22a～图22j所示。A lithium-sulfur battery was prepared by using the carbon-sulfur composite material obtained in Example 4 as a positive electrode, and its self-discharge performance was measured under different conditions. The results are shown in Figs. 22a to 22j.

其中，图22a为总的循环数据与库伦效率图；Wherein, Figure 22a is the total cycle data and coulombic efficiency map;

图22b为充放电6周之后搁置48小时再对电池进行测试，可见循环性能与库伦效率均未受到影响；Figure 22b shows that the battery is tested after being left for 48 hours after charging and discharging for 6 weeks. It can be seen that the cycle performance and the coulombic efficiency are not affected.

图22c为在0.1C充放电结束后搁置48小时再以1C电流充放电，电池性能很差；Figure 22c shows that after charging and discharging at the end of 0.1 C, it is left for 48 hours and then charged and discharged with a current of 1 C, and the battery performance is poor;

图22d可以看出在0.1C充放电搁置48h小时之后，1C充放电电池容量很小，但是在充放电结束搁置48小时之后，再以0.1C充放电，电池性能又得到恢复到达之前的水平。Fig. 22d shows that the charge capacity of the 1C charge and discharge battery is small after the charge and discharge of 0.1 C for 48 hours, but after being charged for 48 hours at the end of charge and discharge, the battery is again charged and discharged at 0.1 C, and the battery performance is restored to the level before the arrival.

图22e为先将电池充电到未充满状态然后搁置48h，再继续进行充放电，可知两次充电总和为874.67(586.13+288.54)mAh/g，而随后的放电容量为867.83mAh/g，此步库伦效率达99.22％；Figure 22e shows that the battery is charged to the unfilled state and then left for 48h, and then the charge and discharge are continued. It can be seen that the total charge is 874.67 (586.13 + 288.54) mAh/g, and the subsequent discharge capacity is 867.83 mAh/g. Coulomb efficiency is 99.22%;

图22f为充电至2.5V后，分步放电，先放电585.97mAh/g后搁置48h，然后接着继续放电数据为273.71mAh/g，此步库伦效率达98.94％，从整体数据来看，充放电过程当中的搁置不影响电池的库伦效率和充放电容量也不会对后续的电池性能产生影响；Figure 22f shows the step-by-step discharge after charging to 2.5V. After discharging 585.97mAh/g, it is left for 48h, and then continues to discharge data at 273.71mAh/g. The Coulomb efficiency is 98.94%. From the overall data, charge and discharge. The shelving in the process does not affect the coulombic efficiency and charge and discharge capacity of the battery and does not affect subsequent battery performance;

图22g和图22h为延长搁置时间至6天和15天的电池测试数据，从数据可以看出电池的充放电性能也未有任何影响；Figure 22g and Figure 22h show the battery test data for extending the shelf life to 6 days and 15 days. It can be seen from the data that the charge and discharge performance of the battery has no effect.

图22i和图22j并分别对搁置时间为6天和15天的电池在充放电结束后测试电池电压的变化，Figure 22i and Figure 22j and test the change of the battery voltage after the end of the charge and discharge of the battery with the shelf time of 6 days and 15 days, respectively.

其中，图22i为电池充电至2.5V之后搁置15天的电压变化，可见电池电压可以稳定在约2.15V，没有明显的自放电现象，Figure 22i shows the voltage change after the battery is charged to 2.5V for 15 days. It can be seen that the battery voltage can be stabilized at about 2.15V without obvious self-discharge.

图22j为电池放电至1.5V后搁置15天的电池电压变化，也可以看出电池电压可以稳定在1.77V左右，电池结构成分也很稳定。Fig. 22j shows the change of the battery voltage after the battery is discharged to 1.5V for 15 days. It can also be seen that the battery voltage can be stabilized at about 1.77V, and the structural components of the battery are also stable.

综上所述，采用修饰之后的碳作为硫载体的复合材料很好地解决了锂硫电池中存在的聚硫离子溶解和穿梭效应问题，自放电问题也得到了很好地限制，数据显示在15天的搁置条件下未观察到明显的自放电现象。In summary, the composite material using carbon as a sulfur carrier after modification has solved the problem of polysulfide ion dissolution and shuttle effect in lithium-sulfur batteries, and the self-discharge problem is also well limited. The data is shown in No significant self-discharge was observed under the 15-day shelf life.

实验例15锂硫电池的阻抗测试Experimental Example 15 Impedance Test of Lithium Sulfur Battery

本实验例所用样品为实施例3和实施例4所制的样品。The samples used in this experimental example were the samples prepared in Example 3 and Example 4.

采用三电极测试电池阻抗测试如下图23a～23c和图24a～24d所示，图23a和23c为C-S复合材料的不同低压状态条件下的阻抗谱，图24a～24d为实施例3制得的C-S复合材料的不同低压条件下的阻抗谱，测试状态均为电压稳定之后测定，充放电电流为按照碳计算的0.1C。The three-electrode test battery impedance test is shown in Figures 23a to 23c and Figures 24a to 24d. Figures 23a and 23c show the impedance spectra of the CS composite under different low-pressure conditions. Figures 24a to 24d show the CS produced in Example 3. The impedance spectrum of the composite under different low pressure conditions was measured after the voltage was stabilized, and the charge and discharge current was 0.1 C calculated according to carbon.

对比可以看出，实施例4制得的C-NH₄-S复合材料在0.8V以下，电池阻抗减少，可以推测为锂离子导电保护膜的形成改善了绝缘性物质硫化锂的导电性能，从而使电池电阻趋于一个较小的值，而普通的复合材料则没有这一个减少的趋势，在硫化锂形成之后电池电阻即没有大的变化。Contrast can be seen from Example 4 is C-NH ₄ -S composite 0.8V In the following, the battery impedance is reduced, presumably to improve the conductivity of lithium sulfide insulating material to form a lithium ion conductive protective membrane, thereby The battery resistance tends to a small value, while the conventional composite material does not have this tendency to decrease, and the battery resistance does not change much after the formation of lithium sulfide.

以上结合具体实施方式和范例性实例对本发明进行了详细说明，不过这些说明并不能理解为对本发明的限制。本领域技术人员理解，在不偏离本发明精神和范围的情况下，可以对本发明技术方案及其实施方式进行多种等价替换、修饰或改进，这些均落入本发明的范围内。本发明的保护范围以所附权利要求为准。 The present invention has been described in detail above with reference to specific embodiments and exemplary embodiments, but these descriptions are not It can be understood that the limitations of the invention. Those skilled in the art will appreciate that various equivalents, modifications, and improvements may be made in the present invention without departing from the spirit and scope of the invention. The scope of the invention is defined by the appended claims.

Claims

一种现场合成锂离子导电保护膜的方法，其特征在于，该方法为以碳-硫复合物为正极材料的锂硫电池在首次放电时，将放电电压下限降低至1.5V以下，优选为1.2V或以下，再充电至工作电压。A method for synthesizing a lithium ion conductive protective film in the field, characterized in that the lithium sulfur battery with a carbon-sulfur composite as a positive electrode material reduces the lower limit of the discharge voltage to 1.5 V or less, preferably 1.2, during the first discharge. Recharge V or below to the operating voltage.
用作权利要求1中所述现场合成锂离子导电保护膜基体的具有多级孔的多孔碳，其特征在于，该多孔碳包括碳骨架，在碳骨架中分布有一级孔和二级孔，其中，一级孔的孔径约为2～10nm，二级孔的孔径约为100～300nm，任选地，在碳骨架表面修饰有羧酸铵基团，在一级孔和二级孔的孔壁表面上修饰有羧酸铵基团。a porous carbon having a multi-stage pore as a matrix for synthesizing a lithium ion conductive protective film according to claim 1, wherein the porous carbon comprises a carbon skeleton in which a primary pore and a secondary pore are distributed, wherein The primary pore has a pore diameter of about 2 to 10 nm, and the secondary pore has a pore diameter of about 100 to 300 nm. Optionally, a carboxylate group is modified on the surface of the carbon skeleton, and the pore walls of the primary and secondary pores are modified. The surface is modified with an ammonium carboxylate group.
根据权利要求2所述的具有多级孔的多孔碳，其特征在于，所述一级孔通过一级模板粒子形成，二级孔通过二级模板粒子形成，其中，The porous carbon having a plurality of pores according to claim 2, wherein the primary pores are formed by primary template particles, and the secondary pores are formed by secondary template particles, wherein

一级模板粒子为粒径约为2～10nm的化合物颗粒，该化合物颗粒在碳化条件下不与其他成分反应，易溶于酸和/或碱，和/或，The primary template particles are compound particles having a particle diameter of about 2 to 10 nm, and the compound particles do not react with other components under carbonization conditions, are easily soluble in acids and/or bases, and/or,

二级模板粒子为粒径约为100～300nm的化合物颗粒，该化合物颗粒在碳化条件下不与其他成分反应，易溶于酸和/或碱，The secondary template particles are compound particles having a particle diameter of about 100 to 300 nm, and the compound particles do not react with other components under carbonization conditions, and are easily soluble in acids and/or bases.

所述碳化条件是指用于形成碳骨架的碳源化合物的碳化条件。The carbonization conditions refer to carbonization conditions of a carbon source compound used to form a carbon skeleton.
根据权利要求2所述的具有多级孔的多孔碳，其特征在于，The porous carbon having a plurality of stages according to claim 2, wherein

所述一级孔通过用酸溶液或碱溶液将一级模板粒子从含有一级模板粒子的碳源化合物的碳化产物中去除而形成；The primary pores are formed by removing primary template particles from a carbonized product of a carbon source compound containing primary template particles with an acid solution or an alkali solution;

所述二级孔通过用酸溶液或碱溶液将二级模板粒子从含有二级模板粒子的碳源化合物的碳化产物中去除而形成。The secondary pores are formed by removing secondary template particles from a carbonized product of a carbon source compound containing secondary template particles with an acid solution or an alkali solution.
权利要求2所述的具有多级孔的多孔碳的制备方法，其特征在于，该方法包括以下步骤：A method of producing porous carbon having a plurality of stages according to claim 2, wherein the method comprises the steps of:

(1-1)按重量比为一级模板粒子:二级模板粒子:碳源化合物＝1:(1～3):(2～5)的比例称取一级模板粒子、二级模板粒子和碳源化合物，充分混合均匀，制得混合物，其中，(1-1) by weight ratio of primary template particles: secondary template particles: carbon source compound = 1: (1 ~ 3): (2 ~ 5) ratio of the first template particles, secondary template particles and a carbon source compound which is uniformly mixed to obtain a mixture, wherein

一级模板粒子为粒径约为2～10nm的化合物颗粒，该化合物颗粒在碳化条件下不与其他成分反应，而易溶于酸和/或碱，用于形成具有多级孔的多孔碳中的一级孔，和/或，The primary template particles are compound particles having a particle diameter of about 2 to 10 nm, and the compound particles do not react with other components under carbonization conditions, but are easily soluble in acids and/or bases and are used to form porous carbon having multi-stage pores. Level 1 hole, and / or,

二级模板粒子为粒径约为100～300nm的化合物颗粒，该化合物颗粒在碳化条件下不与其他成分反应，而易溶于酸和/或碱，用于形成具有多级孔的多孔碳中的二级孔，The secondary template particles are compound particles having a particle diameter of about 100 to 300 nm, and the compound particles do not react with other components under carbonization conditions, but are easily soluble in acids and/or bases for forming porous carbon having multi-stage pores. Secondary hole,

所述碳源化合物为易于碳化的化合物，The carbon source compound is a compound that is easily carbonized.

所述碳化条件是指用于形成碳骨架的碳源化合物的碳化条件；The carbonization condition refers to a carbonization condition of a carbon source compound used to form a carbon skeleton;

(1-2)将步骤(1-1)中制得的混合物在保护性气体保护下，于800～1200℃条件下碳化2～20小时，冷却，得到碳化产物，(1-2) The mixture obtained in the step (1-1) is carbonized at 800 to 1200 ° C for 2 to 20 hours under a protective gas atmosphere, and cooled to obtain a carbonized product.

其中，所述保护性气体为，按体积比为氢气:氩气＝(1～15):(85～99)的氢气与氩气的混合气；Wherein, the protective gas is a mixture of hydrogen and argon in a volume ratio of hydrogen: argon = (1 to 15): (85 to 99);

(1-3)将步骤(1-2)中得到的碳化产物置于酸溶液或碱溶液中，去除一级模板粒子和二级模板粒子，制得具有多级孔的多孔碳。(1-3) The carbonized product obtained in the step (1-2) is placed in an acid solution or an alkali solution to remove the primary template particles and the secondary template particles to obtain a porous carbon having a plurality of pores.
根据权利要求5所述的具有多级孔的多孔碳的制备方法，其特征在于，该方法在步骤(1-3)之后，任选地，包括以下步骤：The method for preparing porous carbon having multi-stage pores according to claim 5, wherein the method, after the step (1-3), optionally, comprises the following steps:

(1-4)将步骤(1-3)中制得的多孔碳基体置于浓硝酸中，在40～70℃下回流5～15小时，分离除去液体，洗涤，用浓氨水浸泡8～20小时，过滤洗涤，干燥，制得表面经过修饰的具有多级孔的多孔碳。(1-4) The porous carbon substrate obtained in the step (1-3) is placed in concentrated nitric acid, refluxed at 40 to 70 ° C for 5 to 15 hours, the liquid is separated and removed, washed, and soaked in concentrated ammonia water for 8 to 20 After hours, it was filtered, washed, and dried to obtain a surface-modified porous carbon having a plurality of pores.
一种碳-硫复合材料，其特征在于，该碳-硫复合材料包括权利要求2～4中任一项所述的具有多级孔的多孔碳和硫磺颗粒，其中硫磺颗粒嵌于具有多级孔的多孔碳的一级孔和二级孔中。 A carbon-sulfur composite material, comprising the porous carbon and sulfur particles having a multi-stage pore according to any one of claims 2 to 4, wherein the sulfur particles are embedded in a plurality of stages. The pores of the porous carbon are in the primary and secondary pores.
权利要求6所述的碳-硫复合材料的制备方法，其特征在于，该方法包括以下步骤：A method of preparing a carbon-sulfur composite according to claim 6, wherein the method comprises the steps of:

(2-1)按照重量比为多孔碳:硫磺＝1：(1～3)，将权利要求2～4中任一项所述的具有多级孔的多孔碳与硫磺混合，研磨，在密闭环境、保护性气体气氛下升温至155℃，保温，在此情况下，硫磺液化，液体硫磺进入多孔碳的一级孔和二级孔中，再在流动的保护性气体气氛下升温至170～200℃，保温，在此情况下，增加硫磺的气化速率，气体硫磺随着流动的保护性气体进一步分散并进入多孔碳的一级孔和二级孔中或者脱离复合材料体系被移除，得到孔中分散有硫磺的多孔碳，(2-1) The porous carbon having a multi-stage pore according to any one of claims 2 to 4 is mixed with sulfur according to a weight ratio of porous carbon: sulfur = 1: (1 to 3), and is sealed in a sealed state. Under the environment and protective gas atmosphere, the temperature is raised to 155 ° C, and the temperature is kept. In this case, the sulfur is liquefied, the liquid sulfur enters the primary pores and the secondary pores of the porous carbon, and then the temperature is raised to 170 in the flowing protective gas atmosphere. 200 ° C, heat preservation, in this case, increase the gasification rate of sulfur, gas sulfur is further dispersed with the flowing protective gas and enters the primary and secondary pores of the porous carbon or is removed from the composite system, Obtaining porous carbon in which sulfur is dispersed in the pores,

其中，所述保护性气体为，按体积比为氢气:氩气＝(1～15):(85～99)的氢气与氩气的混合气；Wherein, the protective gas is a mixture of hydrogen and argon in a volume ratio of hydrogen: argon = (1 to 15): (85 to 99);

(2-2)将孔中分散有硫磺的多孔碳置于空气中冷却。(2-2) The porous carbon in which sulfur is dispersed in the pores is cooled in the air.
权利要求7所述的碳-硫复合材料作为锂硫电池正极材料的用途。 Use of the carbon-sulfur composite material of claim 7 as a cathode material for a lithium sulfur battery.