CN115621434A - Integrated preparation system and method of silicon-oxygen cathode material - Google Patents

Abstract

The invention discloses an integrated preparation system and method of a silicon-oxygen cathode material, wherein the system comprises a silicon monoxide generation device, a gasification chamber, a reaction deposition chamber and a grading discharge device which are sequentially communicated, the silicon monoxide generation device is connected with an inert drainage dilution air source, the gasification chamber is connected with a dopant supply device and a lithium source supply device, the head part of the reaction deposition chamber is connected with a carbon source air supply device, and the tail part of the reaction deposition chamber is connected with a vacuum pump; the preparation method comprises the steps of preparing gas-phase silicon monoxide, gas-phase dopants and a gas-phase lithium source, conveying the gas-phase silicon monoxide, the gas-phase dopants, the gas-phase lithium source and the gas-phase carbon source to a reaction deposition chamber in a certain sequence by using inert gas, completing deposition, doping, lithium supplement and carbon coating of the silicon monoxide in a certain sequence, and performing graded shaping treatment to obtain the silicon-oxygen cathode material. The invention integrates the processes of silicon monoxide preparation, gas phase doping, carbon coating, lithium supplement and the like, reduces the equipment investment and energy consumption, and ensures the uniformity and consistency of doping, lithium supplement and carbon coating.

Description

Integrated preparation system and method of silicon-oxygen cathode material

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to an integrated preparation system and method of a silica anode material.

Background

Lithium ion batteries have been widely used in smart phones, electric vehicles, and power storage. With the increase of intelligent power consumption and the urgent need of electric vehicles for high endurance mileage, the lithium ion battery is forced to need higher energy density. The improvement of the energy density of the lithium ion battery mainly depends on the improvement of the specific capacity of the anode material and the cathode material and the increase of the pressure difference between the anode and the cathode. At present, the negative electrode material is mainly based on a carbon system, which comprises natural graphite and artificial graphite, but the lower theoretical specific capacity (372 mAh/g) of the negative electrode material cannot meet the requirement of a lithium ion battery core with higher energy density (350-450 Wh/kg). Among the many alternative materials, silicon material has a high theoretical specific capacity (4200 mAh/g), and thus, is the most potential material for replacing graphite negative electrodes. However, the pure silicon negative electrode has problems of large volume expansion (over 300%), unstable SEI film (solid electrolyte interface film), low conductivity, and the like, which limits its practical application; at present, the problems can be relieved to a certain extent mainly by means of nanocrystallization, compounding with carbon and the like, but practical conditions are not yet achieved.

Although the theoretical specific capacity (2000 mAh/g) of the silicon monoxide composite material is lower than that of a pure silicon cathode, the theoretical specific capacity is more than 5 times of that of a graphite cathode, and the silicon monoxide composite material can completely meet the requirement of 450Wh/kg of energy density of a lithium ion battery monomer in design. Meanwhile, because the oxygen element exists as a volume buffer region in the lithium deintercalation process, compared with a pure silicon negative electrode material, the lithium deintercalation material shows smaller lithium deintercalation volume expansion effect (less than 150%) and excellent cycling stability, and becomes a high-capacity negative electrode material which is most likely to be applied in a large scale at present.

However, the electronic conductivity of SiO is poor and there is still a greater volume expansion effect than that of the graphite negative electrode (less than 20%). The larger lithium intercalation and deintercalation expansion can cause the fracture and regeneration of an SEI film formed by the negative electrode, hydrofluoric acid can corrode the silicon-based negative electrode after the film is fractured, so that the loss of reversible capacity is increased, and the first coulombic efficiency and the cycle stability of the lithium ion battery are reduced. Meanwhile, due to the existence of oxygen element in SiO, part of active lithium is consumed in the first charging process to form lithium oxide, so the theoretical first coulombic efficiency is only 77%. Therefore, how to improve the electronic conductivity of the SiO, how to compensate the first coulombic efficiency and how to relieve the volume effect are the key links for the large-scale use of the SiO.

In order to solve the conductivity problem, patent CN108172775A discloses a phosphorus doped silicon carbon negative electrode material for a lithium ion battery and a preparation method thereof, the method improves the electronic conductivity of nano silicon by phosphorus doping, and improves the volume effect of silicon by carbon coating, but because the strength of the carbon coating layer is not enough, the carbon coating layer is not compact enough, the carbon coating layer is easy to break in the cycle process, and the cycle life is short. In order to solve the problem of insufficient first coulombic efficiency, patent CN105489846A discloses a method and a system for lithium supplement of a pole piece, and specifically, a lithium band and a to-be-supplemented lithium pole piece are compounded to form a lithium supplement composite pole piece, so that the problem of insufficient first coulombic efficiency of a negative electrode material is solved. However, the dependence of pole piece lithium supplement on equipment is high, and gaps are left after lithium is consumed to influence a battery interface; meanwhile, the lithium is only supplemented on the surface of the pole piece, the uniformity of the lithium supplement is poor, and the problems of insufficient lithium or lithium enrichment exist.

Meanwhile, the prior art has more process steps, and each link of carbon coating, lithium supplement and the like needs a process of heating and then cooling, so that the equipment investment is large, the energy consumption is high, the cooling heat cannot be fully utilized, and the consumed time is long; meanwhile, the preparation is carried out step by step, which is unfavorable for the uniformity and consistency of the material, and no matter how conditions are optimized, the back-end process influences the result of the front-end process, thereby influencing the comprehensive performance and consistency of carbon coating, lithium supplement and the like.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and provides an integrated preparation system and method of a silicon-oxygen cathode material, which integrates the processes of silicon monoxide preparation, gas phase doping, CVD carbon coating, CVD lithium supplement and the like, reduces equipment investment and energy consumption, and ensures the uniformity and consistency of doping, lithium supplement and carbon coating.

The invention provides the following technical scheme:

the first aspect provides an integrated preparation system of a silicon-oxygen cathode material, which comprises a silicon monoxide generation device, a gasification chamber, a reaction deposition chamber and a grading discharge device which are sequentially communicated;

the silicon monoxide generating device is connected with an inert drainage dilution air source;

the gasification chamber is connected with a dopant supply device and a lithium source supply device;

the head of the reaction deposition chamber is connected with a carbon source gas supply device, and the tail of the reaction deposition chamber is connected with a vacuum pump.

Further, the vacuum pump is connected with a tail gas recovery device; an upper fluid baffle connected with the top and a lower fluid baffle connected with the bottom are arranged in the reaction deposition chamber, the upper fluid baffle and the lower fluid baffle are distributed at intervals, and a fluid channel is formed between the upper fluid baffle and the lower fluid baffle.

In a second aspect, there is provided a method for preparing a silicon-oxygen anode material using the system of the first aspect, comprising the steps of:

preparing gas-phase SiO in a SiO generator,

the dopant supply device supplies dopant quantitatively to the gasification chamber and generates gas phase dopant in the gasification chamber;

the lithium source supply device quantitatively supplies a lithium source to the gasification chamber and generates a gas-phase lithium source in the gasification chamber;

the carbon source gas supply device supplies a gas-phase carbon source to the head part of the reaction deposition chamber;

under the condition of vacuum pumping, sequentially draining and pushing gas-phase silicon monoxide and gas-phase dopants to a reaction deposition chamber by using inert gas provided by an inert drainage dilution gas source, finishing deposition and doping of the silicon monoxide according to the sequence, then pushing a gas-phase lithium source and a gas-phase carbon source to the reaction deposition chamber in any sequence or simultaneously, finishing lithium supplement and carbon coating of the silicon monoxide, and obtaining a solid product;

and (4) carrying out grading and shaping treatment on the solid product in a grading discharging device to obtain the silica cathode material.

Furthermore, the inert gas is one of high-purity argon gas, helium gas, nitrogen gas, argon-hydrogen mixed gas and nitrogen-hydrogen mixed gas.

Further, the raw materials for preparing the gas-phase silicon monoxide are silicon powder and silicon dioxide powder, wherein the molar ratio of the silicon powder to the silicon dioxide powder is 3-0.5: 1.

further, the dopant is one or more of organic phosphorus, inorganic phosphorus, organic boron and inorganic boron, preferably one or more of phosphorus oxychloride, phosphorus pentachloride, phosphorus oxybromide, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, boric acid, boron oxide, boron tribromide, trimethyl borate, triethyl borate, tripropyl borate and the like;

further, the lithium source is one of lithium simple substance, lithium oxide, lithium sulfide, lithium halide, lithium salt or other lithium compounds.

Further, the gas-phase carbon source is one or more of methane, acetylene, ethanol, methanol, acetaldehyde and gaseous alkane.

Further, before preparing the gas-phase SiO, the SiO raw material, the dopant and the lithium source are respectively filled into the SiO generating device, the dopant supply device and the lithium source supply device; starting a vacuum pump until the vacuum degree in the SiO generating device is 10-1000 Pa, and adjusting the flow of inert gas to be 0.1-10L; the temperature of the gasification chamber is preset to be 1200-1500 ℃, the temperature of the reaction deposition chamber is preset to be 600-1100 ℃, and then the temperature of the SiO generation device is adjusted to be 1300-1800 ℃ to prepare the gas-phase SiO.

Furthermore, more than two temperature zones are preset in the reaction deposition chamber, and the temperature difference between two adjacent temperature zones is 100-300 ℃.

Furthermore, the heating modes of the SiO generating device, the gasification chamber and the reaction deposition chamber are one or more of resistance wire heating, medium-high frequency induction heating, graphite heating element heating, plasma radiation heating and microwave heating.

Further, the reaction time of doping silicon monoxide is 1-1000 min, the reaction time of lithium supplement is 1-1000 min, and the reaction time of carbon coating is 1-1000 min.

Further, the reaction deposition chamber is cooled to 25-100 ℃ after the reaction is finished.

Compared with the prior art, the invention has the beneficial effects that:

(1) The integrated preparation system of the silicon-oxygen cathode material integrates the processes of silicon monoxide preparation, gas phase doping, CVD carbon coating, CVD lithium supplement and the like, is simple to operate, and can simplify the process flow, reduce the equipment investment, reduce the occupied area and reduce the energy consumption;

(2) The integrated preparation system of the silicon-oxygen cathode material provided by the invention has the advantages that the whole equipment is totally closed, the reaction substances are conveyed through the inert gas, the possibility of pollution and oxidation is reduced, and the introduction of magnetic substances is avoided in the whole gas phase process;

(3) According to the preparation method of the silicon-oxygen cathode material, the doping process is started under the gaseous state of the silicon monoxide, and the atomic or molecular mixed doping is more uniform and sufficient;

(4) According to the preparation method of the silicon-oxygen cathode material, the lithium supplement and the carbon coating both adopt a CVD (chemical vapor deposition) mode, and are uniformly coated on the surface of cured silicon oxide particles in an atomized manner, so that the reaction time is short; meanwhile, as the silicon monoxide is in a deposition and curing state, the silicon monoxide has the characteristics of fluffy interior and high surface activity, the fluffy interior is favorable for rapid and uniform diffusion and infiltration of lithium atoms, the high surface activity is favorable for efficient and rapid carbonization and deposition of a gas phase carbon source, the adhesive force is strong, the stability is high, and the technical problems of local lithium enrichment and non-uniform coating of the existing process are solved;

(5) According to the preparation method of the silica cathode material, the particle size distribution of the product can be flexibly designed and adjusted by adjusting the process sequence of carbon coating and lithium supplement, the particle size is larger when lithium supplement is performed first and then carbon coating is performed, the particle size is smaller when carbon coating is performed first and then lithium supplement is performed, and the particle size is between the two conditions when lithium supplement and carbon coating are performed simultaneously, so that high-energy-consumption process links such as subsequent crushing are not needed;

(6) According to the invention, the integrated preparation process of the silica cathode material is realized through the integrated preparation system, the processes of reheating and cooling in the intermediate process are avoided, the technical problems of coating layer falling and crystal grain annealing and coarsening caused by the former process in the latter process are ingeniously avoided, and the preparation system can effectively adjust the reaction temperature, thereby being beneficial to the control of the reaction condition.

Drawings

FIG. 1 is a schematic structural diagram of an integrated preparation system of a silicon-oxygen anode material in an embodiment of the invention;

FIG. 2 is a SEM photograph of a product of example 2 of the present invention;

FIG. 3 is the charge and discharge curve of the button cell of the product of example 2 of the present invention;

FIG. 4 is an SEM photograph of the product of example 3 of the invention;

FIG. 5 shows the charge-discharge curve of the button cell of the product of example 3 of the present invention;

FIG. 6 is an SEM photograph of the product of example 4 of the invention;

fig. 7 shows the charge-discharge curve of the button cell of the product in example 4 of the present invention;

FIG. 8 is a graph of product cycle performance for examples 2, 3 and 4 of the present invention;

labeled in the figure as: 1. an inert drainage dilution air source; 2. a silicon monoxide generating device; 3. a dopant supply device; 4. a lithium source supply device; 5. a gasification chamber; 6. a carbon source gas supply device; 7. a reaction deposition chamber; 8. an upper fluid barrier; 9. a fluid channel; 10. a vacuum pump; 11. a grading discharging device; 12. a tail gas recovery device; 13. a lower fluid baffle.

Detailed Description

The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

Example 1

As shown in fig. 1, the embodiment provides an integrated preparation system of a silicon-oxygen anode material, which includes a silicon monoxide generating device 2, a vaporizing chamber 5, a reaction deposition chamber 7 and a grading discharging device 11, which are sequentially communicated; the silicon monoxide generating device 2 is connected with an inert drainage dilution air source 1 through a closed pipeline; the gasification chamber 5 is connected with a dopant supply device 3 and a lithium source supply device 4 through closed pipelines; the head of the reaction deposition chamber 7 is connected with a carbon source gas supply device 6 through a closed pipeline, the tail of the reaction deposition chamber is connected with a vacuum pump 10, and the vacuum pump 10 is connected with a tail gas recovery device 12.

The inert drainage dilution gas source 1 is used for providing inert gas with certain purity and certain flow rate to guide the reaction substance to be transmitted or dilute the reaction substance to control the reaction amount; the inert gas flows through the SiO generating device 2, the gasification chamber 5 and the reaction deposition chamber 7 in sequence through a closed pipeline, and finally is pumped by a vacuum pump 10 to enter a tail gas recovery device 12 for recovery treatment.

The SiO production unit 2 is used to produce gas-phase SiO at a certain temperature and vacuum.

The dopant supply device 3 is used for quantitatively supplying dopants, and the dopant is quantitatively conveyed to the gasification chamber 5 through a closed pipeline, gasified or cracked at high temperature, and sent to the reaction deposition chamber 7 under the dilution and drainage of inert gas.

The lithium source supply device 4 is used for quantitatively supplying a lithium source, the lithium source is quantitatively conveyed to the gasification chamber 5 through a closed pipeline, gasified or cracked at high temperature, and pushed to the reaction deposition chamber 7 under the dilution and drainage of inert gas.

The gasification chamber 5 is used as a closed pipeline for guiding gas or gas-phase solid, and can also be used as a gasification or pyrolysis gasification chamber of a dopant or a lithium source to generate the gas-phase dopant or the gas-phase lithium source under high-temperature vacuum.

The carbon source gas supply device 6 is used for quantitatively supplying a gas-phase carbon source, and the gas-phase carbon source can be further diluted and quantitatively drained to the reaction deposition chamber 7 under the drainage and dilution of the inert gas, so that the reaction is further controllable.

The reaction deposition chamber 7 is used for finishing the operations of deposition, doping, lithium supplement and carbon cladding of the silicon monoxide according to a certain sequence. An upper fluid baffle plate 8 connected with the top and a lower fluid baffle plate 13 connected with the bottom are arranged in the reaction deposition chamber 7, the upper fluid baffle plate 8 and the lower fluid baffle plate 13 are distributed at intervals, and a fluid channel 9 is formed between the upper fluid baffle plate 8 and the lower fluid baffle plate 13. The interior of the reaction deposition chamber 7 is divided into more than two sections, and different sections are independent temperature rising areas for forming different temperature fields and promoting the reaction to occur uniformly and efficiently.

The vacuum pump 10 is used for vacuumizing, the boiling point of solid-phase substances can be reduced in a vacuum environment, and a drainage effect can be achieved; the tail gas recovery device 12 is connected with the vacuum pump 10 and is used for treating waste gas generated in the reaction process and reducing environmental pollution.

And the grading discharging device 11 is connected with the outlet end of the reaction deposition chamber 7 and is used for grading the reacted substances.

Example 2

The embodiment provides a method for preparing a silica anode material by using the system described in embodiment 1, and the specific steps are as follows:

s1, mixing a mixture of 1.5:1, the silicon powder and the silica powder were charged into a silicon monoxide generating apparatus 2, a lithium source (metallic lithium powder, molar ratio calculated as lithium atoms) 2.4 times the molar ratio of the silica powder was charged into a lithium source supplying apparatus 4, and a dopant phosphorus pentoxide powder of 1% mass ratio of the silica powder was charged into a dopant supplying apparatus 3.

S2, starting the vacuum pump 10 until the whole system is in a negative pressure state (the vacuum degree is 50 Pa), closing the vacuum pump 10, and keeping for 2 hours, wherein the vacuum degree is not higher than 60Pa; and opening an inert drainage dilution gas source 1, filling the silicon monoxide generating device 2, the dopant supply device 3, the lithium source supply device 4, the gasification chamber 5, the reaction deposition chamber 7 and the grading discharge device 11 with inert gas high-purity argon, and balancing the gas pressure with the atmosphere.

S3, closing the dopant supply device 3, the lithium source supply device 4, the carbon source gas supply device 6 and the grading discharge device 11, respectively connecting with the gasification chamber 5 and the reaction deposition chamber 7 in a physical transmission manner, starting the vacuum pump again to pump the system to a vacuum degree below 50Pa, simultaneously introducing high-purity argon, adjusting the flow rate to be 2L/min, presetting the temperature in the gasification chamber 5 to be 1300 ℃, presetting the temperature of the front section in the reaction deposition chamber 7 to be 700 ℃, the temperature of the middle section to be 900 ℃ and the temperature of the rear section to be 600 ℃.

S4, when the temperatures in the gasification chamber 5 and the reaction deposition chamber 7 are stable, adjusting the temperature in the SiO generating device 2 to 1400 ℃, and heating the silica powder and the silica powder to react under the condition to form gas-phase SiO, and pushing the gas-phase SiO into the reaction deposition chamber 7 for deposition and curing through the gasification chamber 5 under the conditions of vacuum pumping and argon drainage; when the temperature in the SiO 2 is stabilized at 1400 ℃, the connection between the dopant supply device 3 and the vaporizer 5 is opened, the release rate of the dopant is controlled (the dopant supply device 3 has a certain pressure, and the vaporizer 5 is under a certain negative pressure and has a directional flow function), the dopant phosphorus pentoxide released into the vaporizer 5 is rapidly gasified and sublimated at 1300 ℃, the mixed SiO vapor is subjected to doping reaction under the vacuum pumping and the drainage of high-purity argon, and is continuously deposited and cured while diffusing into the reaction deposition chamber 7, so that the doped SiO is obtained; tail gas generated in the reaction is pumped to a tail gas recovery device 12 by a vacuum pump, so that 100 percent of harmful gas is recovered, and the environment is not polluted.

S5, when no smoke is observed from a reaction window in the SiO generating device 2, opening a communication pipeline between the lithium source supply device 4 and the gasification chamber 5, quantitatively releasing metal lithium powder into the gasification chamber 5, and carrying out gasification treatment at 1300 ℃; meanwhile, the flow rate of high-purity argon is adjusted to 5L/min to dilute lithium vapor and conduct the lithium vapor to the reaction deposition chamber 7 in vacuum, the vacuum in the reaction deposition chamber 7 is kept at about 50Pa all the time, gas-phase lithium atoms pass through the fluid flow channel 9, the gas flows through the aging doped silicon monoxide in a turbulent flow manner, the atoms deposit and react on the particle surface, the deposition time is controlled to be 10min, and the lithium supplement is completed; and tail gas generated in the lithium supplementing process is pumped to a tail gas recovery device 12 through a vacuum pump 10 for treatment, and then is discharged in a qualified manner.

S6, after lithium supplement is completed, opening a communication pipeline between a carbon source gas supply device 6 and a reaction deposition chamber 7, wherein acetylene gas is in the carbon source gas supply device 6, and adjusting the flow rate to be 2L/min; meanwhile, the flow rate in the high-purity argon is adjusted to be 2L/min, the vacuum degree in the reaction deposition chamber 7 is kept to be about 50Pa, acetylene gas enters the fluid channel 9, contacts the surface of the lithium-supplemented silicon oxide particles, and is carbonized and deposited for 180min, so that the carbon coating process of CVD is completed; the generated tail gas is pumped to a tail gas treatment device 12 through a vacuum pump 10 and then is discharged in a qualified mode.

S7, cooling the silicon monoxide negative electrode powder subjected to deposition, collaborative doping, lithium supplement and carbon coating to room temperature, and conveying the silicon monoxide negative electrode powder to a grading discharging device 11; classifying the particle size under the protection of high-purity argon, screening and recovering through a classifying device, wherein the classifying device mainly comprises an airflow mill, classifying under the protection of argon, and recovering by combining a cloth bag recovery device to finally obtain qualified silicon monoxide powder.

Example 3

This example provides a method for preparing a silicon-oxygen anode material, which is different from example 2 in that the steps of S5 and S6 are opposite to those of S5 and S6 in example 2, and specifically the following steps are included:

s5, when no smoke generation is observed in a reaction window in the SiO generating device 2, opening a communication pipeline between a carbon source gas supply device 6 and a reaction deposition chamber 7, wherein acetylene gas is in the carbon source gas supply device 6, and adjusting the flow rate to be 2L/min; meanwhile, the flow rate in the high-purity argon is adjusted to be 2L/min, the vacuum degree in the reaction deposition chamber 7 is kept to be about 50Pa, acetylene gas enters the fluid channel 9, contacts the surface of the lithium-supplemented silicon oxide particles, and is carbonized and deposited for 180min, so that the carbon coating process of CVD is completed; the generated tail gas is pumped to a tail gas treatment device 12 through a vacuum pump 10 and then is discharged qualified.

S6, opening a communication pipeline between the lithium source supply device 4 and the gasification chamber 5, quantitatively releasing metal lithium powder into the gasification chamber 5, and carrying out gasification treatment at 1300 ℃; meanwhile, the flow rate of high-purity argon is adjusted to 5L/min, so that lithium vapor is diluted and is drained into the reaction deposition chamber 7 in a vacuum mode, the vacuum in the reaction deposition chamber 7 is kept at about 50Pa all the time, gas-phase lithium atoms pass through the fluid flow channel 9, turbulent flow flows through the aged doped silicon monoxide, atomic deposition and reaction are carried out on the particle surfaces of the silicon monoxide, the deposition time is controlled to be 10min, and lithium supplement is finished; and tail gas generated in the lithium supplementing process is pumped to a tail gas recovery device 12 through a vacuum pump 10 for treatment, and then is discharged in a qualified manner.

Example 4

This example provides a method for preparing a silicon-oxygen anode material, which is different from example 2 in that: s5, controlling the deposition time of lithium supplement to be 100min; and S6, controlling the carbonization and deposition time during carbon coating to be 360min.

Example 5

This example provides a method for preparing a silicon-oxygen anode material, which is different from example 2 in that: in the step S1, the molar ratio of the silicon powder to the silicon dioxide powder is 0.5:1.

example 6

This example provides a method for preparing a silicon-oxygen anode material, which is different from example 2 in that: and in the step S4, when the temperatures in the gasification chamber 5 and the reaction deposition chamber 7 are stable, the temperature in the SiO generation device 2 is adjusted to 1800 ℃, and other conditions are not changed.

Performance characterization

1. SEM analysis of the SiO powders prepared in examples 2-4 showed that the results are shown in FIGS. 2, 4 and 6, respectively. As can be seen from the figure, the product after carbon coating and lithium supplement is slightly smaller in size and uniform in distribution; the carbon coating and pre-lithiation time is prolonged, floating powder with more carbon can appear in the product, and the product quality uniformity is poor; the carbon coating and lithium supplement are controlled as much as possible to realize the optimal uniform reaction in a short time.

2. Taking a Japanese Beacon chemical product as a comparative example, taking the comparative example and the silicon monoxide powder prepared in the examples 2 to 6 to carry out an electrochemical test, and the specific steps are as follows:

(1) According to the mass ratio of 8:1:1 mixing silicon monoxide powder, PAA (polyacrylic acid) and SP (conductive carbon black), grinding uniformly by hand in an agate mortar, and mixing into aqueous pasty slurry.

(2) Coating the mixed slurry on a copper foil with a thickness of 10 μm by using a doctor blade with a gap of 250 μm, and drying at 100 deg.C for 10hrs under vacuum; rolling the mixture to the thickness of 100 mu m on a manual double-roller machine, punching the mixture into a circular pole piece with the diameter of 12mm, weighing the pole piece and calculating the weight of the active substance; left in the glove box overnight.

(3) The next day, CR2016 type button cell was assembled in a glove box, with metal lithium as the counter electrode, PE (polyethylene) film as the separator, and lithium salt concentration of 1M LiFP ₆ (hexafluorophosphoric acid), solvent ratio EC (ethylene carbonate): EMC (methyl ethyl carbonate) =3: 7% by weight of an electrolyte containing 5% (w%) of FEC (fluoroethylene carbonate) additive.

(4) The button cell is kept stand at normal temperature for 12h, and is subjected to constant current charge and discharge test on a blue test system, wherein 0.1C battery is used for discharging to 5mV, then 0.02C constant current discharging to 5mV, and then 0.1C charging to 1.5V.

The charge and discharge curves of examples 2 to 4 are shown in fig. 3, 5 and 7, respectively, the cycle performance of the products of examples 2 to 4 is shown in fig. 8, and the electrochemical data of comparative example and examples 2 to 6 are summarized in table 1.

TABLE 1 summary of electrochemical data for comparative example and examples 2-6

Note: in table 1, capacity retention for 100 weeks of cycling was obtained based on first charge capacity.

Example 2 is compared with example 3, and shows that the sequential order of the two processes of lithium supplement and carbon coating has great influence on gram capacity exertion, first efficiency and cycling stability of the silicon-oxygen negative electrode: alloying firstly and then carbon coating, wherein the rear-section coating process influences the front section to coarsen crystal grains, the grains are large, the gram volume is low, the cycle stability is weak, and the first efficiency is high; the carbon coating is carried out firstly and then the alloying is carried out, the particle size can be effectively controlled, the gram volume and the cycling stability are greatly improved, and the first coulombic efficiency is slightly low.

Example 2 is compared with example 4, and shows that the prolonging of the lithium supplement time and the carbon coating time can reduce the gram capacity and the cycling stability, particularly the cycling stability is seriously degraded, although the first coulombic efficiency is improved to 95 percent; possibly long high temperature annealing, resulting in deep lithiation and coarsening growth of silicon grains.

Example 2 is compared with example 5, which shows that the charging ratio of silicon powder and silica powder has a great influence on the capacity and the first efficiency of the final product, and the larger the proportion of silica, the poorer the performance.

Example 2 compares with example 6 and demonstrates that the production temperature of SiO is increased, which can improve the capacity and first efficiency of the final product.

The overall electrochemical performance of examples 2-6 is superior to that of the best commercial product (comparative).

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (10)

1. An integrated preparation system of a silicon-oxygen cathode material is characterized by comprising a silicon monoxide generation device, a gasification chamber, a reaction deposition chamber and a grading discharge device which are sequentially communicated;

the silicon monoxide generating device is connected with an inert drainage dilution air source;

the gasification chamber is connected with a dopant supply device and a lithium source supply device;

the head of the reaction deposition chamber is connected with a carbon source gas supply device, and the tail of the reaction deposition chamber is connected with a vacuum pump.

2. The integrated preparation system of the silicon-oxygen anode material according to claim 1, wherein the vacuum pump is connected with a tail gas recovery device; an upper fluid baffle plate connected with the top and a lower fluid baffle plate connected with the bottom are arranged in the reaction deposition chamber, the upper fluid baffle plate and the lower fluid baffle plate are distributed at intervals, and a fluid channel is formed between the upper fluid baffle plate and the lower fluid baffle plate.

3. A method for preparing a silicon-oxygen negative electrode material by using the system as defined in any one of claims 1 to 2, which is characterized by comprising the following steps:

preparing gas-phase SiO in the SiO generator,

the dopant supply device supplies dopant quantitatively to the gasification chamber and generates gas phase dopant in the gasification chamber;

the lithium source supply device quantitatively supplies a lithium source to the gasification chamber and generates a gas-phase lithium source in the gasification chamber;

the carbon source gas supply device supplies a gas-phase carbon source to the head part of the reaction deposition chamber;

under the condition of vacuum pumping, sequentially guiding and pushing gas-phase silicon monoxide and gas-phase dopants to a reaction deposition chamber by using inert gas provided by an inert drainage dilution gas source, completing deposition and doping of the silicon monoxide according to the sequence, then pushing a gas-phase lithium source and a gas-phase carbon source to the reaction deposition chamber in any sequence or simultaneously, completing lithium supplement and carbon coating of the silicon monoxide, and obtaining a solid product;

and (3) carrying out grading and shaping treatment on the solid product in a grading discharging device to obtain the silica cathode material.

4. The preparation method of the silicon-oxygen anode material according to claim 3, wherein the raw materials for preparing the gas-phase silicon monoxide are silicon powder and silicon dioxide powder, and the molar ratio of the silicon powder to the silicon dioxide powder is 3-0.5: 1.

5. the preparation method of the silicon-oxygen negative electrode material as claimed in claim 3, wherein the dopant is one or more of organic phosphorus, inorganic phosphorus, organic boron and inorganic boron; the lithium source is one of lithium simple substance, lithium oxide, lithium sulfide, lithium halide and lithium salt.

6. The method for preparing the silicon-oxygen anode material according to claim 3, wherein the gas-phase carbon source is one or more of methane, acetylene, ethanol, methanol, acetaldehyde and gaseous alkane.

7. The method for producing a silicon oxide negative electrode material according to claim 3, wherein before producing the gas-phase SiO, a SiO raw material, a dopant, and a lithium source are charged into the SiO generating device, the dopant supply device, and the lithium source supply device, respectively; starting a vacuum pump until the internal vacuum degree of the silicon monoxide generation device is 10 to 1000Pa, and adjusting the flow of inert gas to be 0.1 to 10L; the temperature of the gasification chamber is preset to be 1200-1500 ℃, the temperature of the reaction deposition chamber is preset to be 600-1100 ℃, then the temperature of the silicon monoxide generating device is adjusted to be 1300-1800 ℃, and the gas phase silicon monoxide is prepared.

8. The preparation method of the silicon-oxygen anode material according to claim 7, wherein the reaction deposition chamber is preset with more than two temperature zones, and the temperature difference between two adjacent temperature zones is 100-300 ℃.

9. The preparation method of the silicon oxide negative electrode material as claimed in claim 3, wherein the reaction time for doping silicon monoxide is 1 to 1000min, the reaction time for lithium supplement is 1 to 1000min, and the reaction time for carbon coating is 1 to 1000min.

10. The preparation method of the silicon-oxygen anode material as claimed in claim 3, wherein the reaction deposition chamber is cooled to 25-100 ℃ after the reaction is completed.

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