CN109802135B - Lithium-sulfur battery positive electrode material, and preparation method and application thereof - Google Patents
Lithium-sulfur battery positive electrode material, and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to a lithium-sulfur battery anode material, which comprises a sulfur-carrying sulfide molecular sieve and a carbon coating layer coated outside the sulfur-carrying sulfide molecular sieve; the sulfur-bearing sulfide molecular sieve comprises a metal-containing sulfide molecular sieve and elemental sulfur arranged in pore channels of the metal-containing sulfide molecular sieve. The sulfide molecular sieve containing metal adopted by the invention has rich pore channel structure, and metal cations in the pore channels are opposite to S in the discharge process2‑The material has the electrostatic attraction effect, so that the combination of sulfur and lithium can be prevented, the volume expansion of the electrode material is reduced, the electrochemical performance of the material is improved, and the cycle life of the material is prolonged; the carbon coating layer can endow the positive electrode material of the lithium-sulfur battery with good electron transport performance on one hand, and can further prevent the combination of sulfur and lithium on the other hand, reduce the dissolution and diffusion of lithium polysulfide in electrolyte and further improve the electrochemical performance of the material.
Description
Technical Field
The invention belongs to the technical field of battery materials, and particularly relates to a lithium-sulfur battery positive electrode material, and a preparation method and application thereof.
Background
At present, limited by the capacity of the positive active material, the energy density of the lithium ion battery can be improved in a small amount, and the limit value of the lithium ion battery is generally considered to be 250-300 Wh/Kg, and the aim of 700Wh/Kg is difficult to achieve by the lithium ion battery, so that the development of a next-generation novel battery is urgently needed. The lithium-sulfur battery is a battery system which adopts sulfur or a sulfur-containing compound as a positive electrode and lithium or a lithium storage material as a negative electrode and realizes mutual conversion of electric energy and chemical energy by breaking/generating a sulfur-sulfur bond. The lithium-sulfur battery can better meet four aspects of the requirements of future power batteries: namely high energy density, better safety, environmental protection and low cost.
However, the lithium metal negative electrode and the sulfur-based positive electrode material in the lithium-sulfur battery mainly have the following problems: (1) at room temperature, the most thermodynamically stable sulfur molecule is a crown S composed of eight S atoms connected together8The bonding between the molecules forms elemental sulphur of very good crystallinity, which is a typical electronic and ionic insulator, and therefore S8The electrochemical activity of the electrode active material is poor, and the utilization rate of the active material is low; (2) elemental sulfur can be reduced into easily soluble polysulfide in the discharging process, so that active substances are lost, and after the polysulfide is dissolved in electrolyte, the concentration of the electrolyte can be increased, and the ionic conductivity of the electrolyte is deteriorated; (3) in the charging process, after the anode is oxidized, long-chain polysulfide dissolved in electrolyte is easily diffused to the surface of a lithium cathode to be subjected to electrochemical reduction, and then is diffused to the anode to be oxidized again, so that a cyclic reaction mechanism of anode oxidation-cathode reduction is formed, namely, the shuttle effect, so that the completion of the normal charging of a battery is influenced, and the coulombic efficiency of charging is reduced; in addition, the large amount of polysulfide is dissolved, so that the viscosity of the electrolyte is increased, the ionic conductivity of the electrolyte is greatly reduced, the degradation of the electrode performance is accelerated, and the reduction deposition of polysulfide on the surface of lithium can cause the corrosion of a lithium negative electrode and influence the chargeability of a lithium electrode; (4) in the discharging process of the lithium-sulfur battery, volume expansion occurs due to the combination of positive electrode sulfur and lithium, negative electrode lithium is reduced in volume due to the consumption of lithium, so that the volumes of the positive electrode and the negative electrode repeatedly change, and the sulfur electrode generates micro cracks due to the repeated change of the size of the electrode, so that the conductive network of the positive electrode and the integrity of the battery are damaged, and the capacity attenuation of the lithium-sulfur battery is aggravated. These problems have severely restricted the development of lithium sulfur batteries, which is also the focus of current lithium sulfur battery research.
CN106299317A discloses a positive electrode material of a lithium-sulfur battery, which includes a positive active material, the positive active material includes elemental sulfur, the positive active material further includes a conductive polymer, and the elemental sulfur and the conductive polymer form a three-dimensional cross-linked hollow tube; the elemental sulfur and the conductive polymer are compounded to form a compound, the polymer molecules contain unsaturated double bonds, and the elemental sulfur and the unsaturated double bonds of the chain polymer form a chemical bonding effect to form a three-dimensional crosslinking network structure. The invention also provides a preparation method of the lithium-sulfur battery positive electrode material. The positive electrode material of the lithium-sulfur battery is easy to generate sulfide to dissolve out in the charge-discharge cycle process, so that capacity fading is caused.
CN107611395A discloses a small-sized graphene lithium-sulfur battery positive electrode material, a lithium-sulfur battery prepared from the same, and a preparation method, where the preparation method includes the following steps: (1) preparing small-size graphene by using microcrystalline graphite powder as a raw material and adopting an electrolytic method; (2) preparing a binder solution; (3) and compounding the small-size graphene or the surface modified small-size graphene with sulfur to form a graphene/sulfur composite material, namely the small-size graphene lithium-sulfur battery positive electrode material. The positive electrode material prepared by the method is easy to generate sulfide dissolution in the charge-discharge cycle process, so that capacity attenuation is caused.
CN106340631A discloses a preparation method of a positive electrode material of a lithium-sulfur battery, which comprises the following steps: (1) soaking cotton: soaking cotton in hydrochloric acid solution containing zinc chloride, sealing, maintaining the temperature, removing the redundant solution, drying the mixture, and maintaining the temperature to obtain gray or brown solid; (2) preparation of porous carbon substrate: sequentially carrying out carbonization treatment and acidification treatment on the solid, and then washing, drying and calcining to obtain a porous carbon matrix; (3) preparation of carbon-sulfur composite material: and co-heating the porous carbon substrate and elemental sulfur to synthesize the lithium-sulfur battery cathode material. The positive electrode material prepared by the method is easy to generate sulfide dissolution in the charge-discharge cycle process, so that capacity attenuation is caused.
Therefore, there is an urgent need in the art to develop a novel positive electrode material for a lithium-sulfur battery, which can inhibit the dissolution and loss of an intermediate product during charge and discharge cycles, thereby improving the cycle stability of a sulfur electrode, and which has a simple preparation method and is industrially producible.
Disclosure of Invention
In view of the defects of the prior art, one of the purposes of the present invention is to provide a lithium sulfur battery cathode material, which comprises a sulfur-loaded sulfide molecular sieve and a carbon coating layer coated outside the sulfur-loaded sulfide molecular sieve;
the sulfur-bearing sulfide molecular sieve comprises a metal-containing sulfide molecular sieve and elemental sulfur arranged in pore channels of the metal-containing sulfide molecular sieve.
The metal-containing sulfide molecular sieve adopted by the invention has rich pore channel structures, can well disperse sulfur simple substances in the pore channels of the molecular sieve in a molecular state, has a function of improving the capacity of anode materials by metal elements in the metal-containing sulfide molecular sieve, and simultaneously has a function of improving the S in the discharging process by metal cations in the pore channels compared with non-carbon molecular sieves such as silicon molecular sieves and the like in the prior art2-The material has the electrostatic attraction effect, so that the combination of sulfur and lithium can be prevented, the volume expansion of the electrode material is reduced, the electrochemical performance of the material is improved, and the cycle life of the material is prolonged; the carbon coating layer can endow the lithium-sulfur battery positive electrode material with good electron transmission performance on one hand, can further prevent the combination of sulfur and lithium on the other hand, and reduce the dissolution and diffusion of lithium polysulfide in electrolyte, thereby endowing the material with good electrochemical performance, wherein under the current density of 1C, the first discharge specific capacity is more than or equal to 1267.2mAh/g, the first coulombic efficiency is more than or equal to 85.0 percent, and the capacity retention rate of 200 weeks is more than or equal to 93.1 percent.
Preferably, the metal-containing sulfide molecular sieve has the formula M1-MS, said M1Including any one or a combination of at least two of Fe, Cu, Co, Zn, Li, Mn and Na, preferably Co.
M in the metal-containing sulfide molecular sieve of the invention1With positive charge, to S2-Has electrostatic adsorption effect.
The M includes any one or a combination of at least two of Sb, Sn, Ga, Ge and In, preferably Sb.
According to the metal-containing sulfide molecular sieve, M in the metal-containing sulfide molecular sieve is different in valence state, so that the metal-containing sulfide molecular sieve takes the super tetrahedral clusters with different sizes as a construction unit.
Preferably, the diameter of the pore channel of the metal-containing sulfide molecular sieve is 0.1-5 nm, such as 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, 3nm, 4nm, etc.
Preferably, the specific surface area of the metal-containing sulfide molecular sieve is 100-10000 m2Per g, preferably 500 to 3000m2G, e.g. 200m2/g、500m2/g、1000m2/g、3000m2/g、5000m2/g、8000m2And/g, etc.
Preferably, the lithium sulfur battery positive electrode material further comprises a carbon material supported on the sulfur-supported sulfide molecular sieve.
The carbon material in the lithium-sulfur battery positive electrode material can endow the lithium-sulfur battery positive electrode material with good conductivity, relieve the shuttle effect of polysulfide of the lithium-sulfur battery positive electrode material in the charging and discharging process, solve the problem of volume expansion and further endow the lithium-sulfur battery positive electrode material with good electrochemical performance.
Preferably, the carbon material comprises a one-dimensional carbon material and/or a two-dimensional carbon material, preferably any one or a combination of at least two of graphene, graphdiyne, and carbon nanotubes.
Preferably, the composition of the positive electrode material of the lithium-sulfur battery comprises the following components in percentage by mass:
50-80 wt% of sulfur-carrying sulfide molecular sieve
3 to 15 weight percent of carbon coating layer
8-20 wt% of carbon film;
the sum of the total mass percentages of the components of the lithium-sulfur battery positive electrode material is 100%.
Preferably, the sulfur-carrying sulfide molecular sieve comprises the following components in percentage by mass:
10-30 wt% of metal-containing sulfide molecular sieve
70-90 wt% of elemental sulfur;
the sum of the total mass percent of all the components of the sulfur-carrying sulfide molecular sieve is 100 percent.
The invention also aims to provide a preparation method of the lithium-sulfur battery positive electrode material, which comprises the following steps:
(1) mixing a metal-containing sulfide molecular sieve with a sulfur simple substance, and heating for one time to obtain a sulfur-carrying sulfide molecular sieve;
(2) and adding a coated carbon source and a carbon film into the sulfur-carrying sulfide molecular sieve, and carrying out secondary heating to obtain the lithium-sulfur battery cathode material.
The preparation process is simple and can be used for industrial production.
Preferably, the preparation method of the metal-containing sulfide molecular sieve in the step (1) comprises the following steps: m source, M1And mixing the source, the sulfur source and the auxiliary solvent, washing and drying the obtained product after hydrothermal treatment to obtain the metal-containing sulfide molecular sieve.
Preferably, said M1The molar ratio of the source, the M source and the sulfur source is 2-40: 4-48: 1-97, for example 22:16:33, 22:17:33, 2:4:8, 38:48:97, 24:12:30, etc.
Preferably, said M1The mass ratio of the total mass of the source, the M source, the sulfur source and the auxiliary solvent to the auxiliary solvent is 0.5-2: 1, such as 0.6:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, and the like.
Preferably, the M source includes any one or a combination of at least two of Sb salt, Sn salt, Ga salt, Ge salt, and In salt, preferably any one or a combination of at least two of Sb salt, Ga salt, and In salt.
Preferably, said M1The source includes any one or a combination of at least two of Li salt, Fe salt, Cu salt, Co salt, Mn salt, Zn salt and Na salt, preferably any one or a combination of at least two of Co salt, Li salt and Fe salt.
Preferably, the sulphur source comprises sulphide and/or sulphur powder.
Preferably, the sulfide includes any one of sodium sulfide, lithium sulfide, zinc sulfide, calcium sulfide, and barium sulfide or a combination of at least two thereof.
Preferably, the auxiliary solvent comprises an aqueous methylamine solution.
Preferably, the mass fraction of the auxiliary solvent is 10 wt% to 30 wt%, such as 12 wt%, 15 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt%, 28 wt%, etc.
Preferably, the hydrothermal temperature is 100 to 200 ℃, for example, 120 ℃, 150 ℃, 180 ℃, and the like.
Preferably, the hydrothermal time is 72h to 240h, such as 100h, 120h, 150h, 180h, 200h, 220h, and the like.
Preferably, the drying temperature is 60 to 90 ℃, such as 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃ and the like.
Preferably, the drying time is 8h to 12h, such as 9h, 10h, 11h, and the like.
Preferably, the mass ratio of the metal-containing sulfide molecular sieve to the elemental sulfur in step (1) is 0.5-9: 1, preferably 3-9: 1, such as 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, and the like.
When the mass ratio of the metal-containing sulfide molecular sieve to the elemental sulfur is less than 0.5:1, the content of the metal-containing sulfide molecular sieve is too small, the elemental sulfur has poor dispersibility in the metal-containing sulfide molecular sieve pore canal, and the metal-containing sulfide molecular sieve has S pairs2-Has a small electrostatic attraction effect and has an excessive S2-The electrochemical performance of the material is reduced by combining with lithium; when the mass ratio of the metal-containing sulfide molecular sieve to the elemental sulfur is more than 9:1, the content of the elemental sulfur is too small, and further the capacity is low.
Preferably, the metal-containing sulfide molecular sieve and the elemental sulfur are mixed by grinding and mixing.
Preferably, the temperature of the primary heating is 100 to 200 ℃, for example, 120 ℃, 150 ℃, 180 ℃ and the like.
Preferably, the time of the primary heating is 5-48 h, preferably 10-20 h, such as 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h and the like.
Preferably, the mass ratio of the sulfur-loaded metal-containing sulfide molecular sieve, the coated carbon source and the carbon film in the step (2) is 10-100: 1: 5-20, preferably 20-80: 1: 5-10, such as 20:1:6, 30:1:8, 40:1:10, 50:1:12, 60:1:15, 80:1:18, and the like.
Preferably, the coated carbon source comprises any one or a combination of at least two of polyacrylonitrile, polyvinylidene fluoride, polyoxyethylene, polymethyl methacrylate, polyvinylidene fluoride-hexafluoropropylene, polyvinyl butyral, polyvinylpyrrolidone, polypyrrole, polyaniline, polythiophene, tetrabutyl titanate and lithium phosphate, and is preferably polypyrrole.
Preferably, the temperature of the secondary heating is 80 to 150 ℃, for example, 100 ℃, 120 ℃, 140 ℃ and the like.
Preferably, the time of the secondary heating is 2-10 h, such as 3h, 4h, 5h, 6h, 7h, 8h, 9h and the like.
As a preferred technical scheme, the preparation method of the lithium-sulfur battery positive electrode material comprises the following steps:
(1) mixing Li salt, Ga salt, sulfur powder and methylamine water solution according to the molar ratio of the Li salt, the Ga salt and the sulfur powder of 2-40: 4-48: 1-97 and the mass ratio of the total mass of the Li salt, the Ga salt and the sulfur powder to the methylamine water solution with the mass fraction of 10-30 wt% of 0.5-2: 1, carrying out hydrothermal treatment at 100-200 ℃ for 72-240 h, washing the obtained product, and drying at 60-90 ℃ for 8-12 h to obtain a sulfide molecular sieve containing metal;
(2) grinding and mixing the metal-containing sulfide molecular sieve and the sulfur simple substance according to the mass ratio of the metal-containing sulfide molecular sieve to the sulfur simple substance of 3-9: 1, and heating for 10-20 hours at 100-200 ℃ to obtain a sulfur-carrying sulfide molecular sieve;
(3) and adding polypyrrole and a carbon film into the sulfur-loaded sulfide molecular sieve according to the mass ratio of 20-80: 1: 5-10 of the sulfur-loaded sulfide molecular sieve to the carbon film, and heating at 80-150 ℃ for 2-10 hours to obtain the lithium-sulfur battery cathode material.
It is a further object of the present invention to provide a lithium sulfur battery comprising the lithium sulfur battery positive electrode material according to one of the objects.
Preferably, the lithium-sulfur battery positive electrode material is one of the objects.
Compared with the prior art, the invention has the following beneficial effects:
(1) the metal-containing sulfide molecular sieve adopted by the invention has rich pore channel structures, can well disperse sulfur simple substances in the pore channels of the molecular sieve in a molecular state, has a function of improving the capacity of anode materials by metal elements in the metal-containing sulfide molecular sieve, and simultaneously has a function of improving the S in the discharging process by metal cations in the pore channels compared with non-carbon molecular sieves such as silicon molecular sieves and the like in the prior art2-The material has the electrostatic attraction effect, so that the combination of sulfur and lithium can be prevented, the volume expansion of the electrode material is reduced, the electrochemical performance of the material is improved, and the cycle life of the material is prolonged; the carbon coating layer can endow the lithium-sulfur battery positive electrode material with good electron transmission performance on one hand, can further prevent the combination of sulfur and lithium on the other hand, and reduce the dissolution and diffusion of lithium polysulfide in electrolyte, thereby endowing the material with good electrochemical performance, wherein under the current density of 1C, the first discharge specific capacity is more than or equal to 1267.2mAh/g, the first coulombic efficiency is more than or equal to 85.0 percent, and the capacity retention rate of 200 weeks is more than or equal to 93.1 percent.
(2) The carbon material in the lithium-sulfur battery positive electrode material can endow the lithium-sulfur battery positive electrode material with good conductivity, and can relieve the problem of volume expansion of the lithium-sulfur battery positive electrode material in the charging and discharging processes, so that the lithium-sulfur battery positive electrode material is endowed with good electrochemical performance.
Detailed Description
For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
A preparation method of a lithium-sulfur battery positive electrode material comprises the following steps:
(1) according to the formula Li24Ga12S30Mixing lithium chloride, gallium nitrate and sulfur powder according to a molar ratio of 24:12:30, adding 25 wt% of methylamine aqueous solution, wherein the mass ratio of the total mass of the lithium chloride, the gallium nitrate and the sulfur powder to the methylamine aqueous solution is 0.8:1, carrying out hydrothermal treatment at 180 ℃ for 200 hours, and washing the obtained productDrying at 80 ℃ for 10h to obtain a metal-containing sulfide molecular sieve;
(2) grinding and mixing the metal-containing sulfide molecular sieve and the elemental sulfur according to the mass ratio of the metal-containing sulfide molecular sieve to the elemental sulfur of 8:1, and heating at 180 ℃ for 18h to obtain a sulfur-loaded sulfide molecular sieve;
(3) and adding polypyrrole and a carbon film into the sulfur-loaded sulfide molecular sieve according to the mass ratio of the sulfur-loaded sulfide molecular sieve to the polypyrrole to the graphene to be 30:1:6, and heating at 120 ℃ for 8h to obtain the lithium-sulfur battery cathode material.
Example 2
The difference from example 1 is that the mass ratio of the metal-containing sulfide molecular sieve to elemental sulfur in step (2) is 0.5: 1.
Example 3
The difference from example 1 is that the mass ratio of the metal-containing sulfide molecular sieve to elemental sulfur in step (2) is 9: 1.
Example 4
The difference from example 1 is that the mass ratio of the metal-containing sulfide molecular sieve to elemental sulfur in step (2) is 0.4: 1.
Example 5
The difference from example 1 is that the mass ratio of the metal-containing sulfide molecular sieve to elemental sulfur in step (2) is 10: 1.
Example 6
The difference from the example 1 is that the mass ratio of the sulfur-loaded sulfide molecular sieve, polypyrrole and graphene in the step (3) is 9:1: 21.
Example 7
The difference from the example 1 is that the mass ratio of the sulfur-loaded sulfide molecular sieve, polypyrrole and graphene in the step (3) is 101:1: 4.
Example 8
A preparation method of a lithium-sulfur battery positive electrode material comprises the following steps:
(1) according to the formula Li10Fe12In16S33Lithium chloride, ferrous chloride, indium nitrate and sulfur powder are mixed according to a molar ratio of 10:12:16:33, then adding 10 wt% of methylamine water solution, wherein the mass ratio of the total mass of the lithium chloride, the ferrous chloride, the indium nitrate and the sulfur powder to the methylamine water solution is 2:1, carrying out hydrothermal treatment at 100 ℃ for 240 hours, washing the obtained product, and drying at 90 ℃ for 12 hours to obtain the metal-containing sulfide molecular sieve;
(2) grinding and mixing the metal-containing sulfide molecular sieve and the elemental sulfur according to the mass ratio of the metal-containing sulfide molecular sieve to the elemental sulfur of 8:1, and heating at 100 ℃ for 20 hours to obtain a sulfur-carrying sulfide molecular sieve;
(3) and adding the polyvinylidene fluoride and the graphite alkyne into the sulfur-loaded sulfide molecular sieve according to the mass ratio of the sulfur-loaded sulfide molecular sieve to the polyvinylidene fluoride to the graphite alkyne to be 100:1:20, and heating for 2 hours at 150 ℃ to obtain the lithium-sulfur battery cathode material.
Example 9
A preparation method of a lithium-sulfur battery positive electrode material comprises the following steps:
(1) according to the formula Co2In4S8Mixing cobalt sulfate, indium nitrate and sulfur powder according to a molar ratio of 2:4:8, then adding a methylamine aqueous solution with the mass fraction of 30 wt%, wherein the mass ratio of the total mass of the cobalt sulfate, the indium nitrate and the sulfur powder to the methylamine aqueous solution is 0.5:1, carrying out hydrothermal treatment at 200 ℃ for 72 hours, washing an obtained product, and drying at 60 ℃ for 8 hours to obtain a sulfide molecular sieve containing metal;
(2) grinding and mixing the metal-containing sulfide molecular sieve and the elemental sulfur according to the mass ratio of the metal-containing sulfide molecular sieve to the elemental sulfur of 8:1, and heating at 200 ℃ for 10 hours to obtain a sulfur-carrying sulfide molecular sieve;
(3) adding the polythiophene and the carbon nano tube into the sulfur-loaded sulfide molecular sieve according to the mass ratio of 10:1:5 of the sulfur-loaded sulfide molecular sieve, and heating at 80 ℃ for 10 hours to obtain the lithium-sulfur battery cathode material.
Comparative example 1
The difference from example 1 is that no metal-containing sulfide molecular sieve is added in step (2).
Comparative example 2
The difference from example 1 is that in step (2), the metal-containing sulfide molecular sieve is replaced by a hexagonal mesoporous all-silicon molecular sieve.
And (3) performance testing:
the prepared lithium-sulfur battery positive electrode material is subjected to the following performance tests:
(1) assembling the battery: the positive pole piece is made of the positive pole material of the lithium-sulfur battery prepared by the invention, the negative pole is a metal lithium piece, the diaphragm is Celgard2400, and the electrolyte is 1mol/L LiPF6/DMC + DEC, so that the CR2025 type button battery is assembled. The preparation process of the positive pole piece comprises the following steps: mixing the prepared lithium-sulfur battery positive electrode material, conductive agent acetylene black and binder PVDF (polyvinylidene fluoride) according to the mass ratio of 8:1:1, using N-methylpyrrolidone NMP as a solvent to prepare slurry, coating the slurry on an aluminum foil, drying the aluminum foil at 120 ℃ for 12 hours, and rolling and punching the aluminum foil into a wafer with the diameter of 8.4mm to serve as a positive electrode plate.
(2) Electrochemical testing: and (2) testing the prepared button battery on a LAND battery testing system under a normal temperature condition, wherein the charging and discharging voltage interval is 1.5-3.0V, and the charging and discharging test is carried out under the current density of 1C, wherein the holding ratio of 200 cycles is discharge specific capacity/first discharge specific capacity of 200 cycles, and the first coulombic efficiency is first discharge specific capacity/first charge specific capacity.
TABLE 1
As can be seen from Table 1, the lithium-sulfur battery positive electrode materials obtained in examples 1 to 9 have good electrochemical properties, and under the current density of 1C, the first discharge specific capacity is not less than 1267.2mAh/g, the first coulombic efficiency is not less than 85.0%, and the capacity retention rate at 200 weeks is not less than 93.1%.
As can be seen from Table 1, in example 4, compared to example 1, the first coulombic efficiency and the capacity retention rate at 200 weeks are lower at the current density of 1C, probably because the content of the metal-containing sulfide molecular sieve in example 4 is too low, and further the sulfur is less dispersed in the pores of the metal-containing sulfide molecular sieve, and the metal-containing sulfide molecular sieve has a poor S pair2-Has less electrostatic attraction effectMultiple S2-In combination with lithium, the electrochemical performance of the material is reduced, so that the first coulombic efficiency and 200-week capacity retention rate are lower in example 4 compared with example 1.
As can be seen from Table 1, in example 5, compared with example 1, the specific capacity of initial discharge is lower at a current density of 1C, probably because the content of the metal-containing sulfide molecular sieve in example 5 is too high, the content of elemental sulfur is too low, and the active capacity of electrochemical reaction is lower, so that example 5 is compared with example 1
In example 1, the first discharge specific capacity was low.
As can be seen from table 1, in example 6, compared to example 1, the first discharge specific capacity is lower at a current density of 1C, which is probably because the content of the sulfur-loaded sulfide molecular sieve in example 6 is too low, the content of graphene is too high, and the active capacity of the electrochemical reaction is lower, so that in example 6, compared to example 1, the first discharge specific capacity is lower.
As can be seen from table 1, in example 7, compared to example 1, the first coulombic efficiency and the 200-cycle capacity retention rate are lower at a current density of 1C, and probably because the content of the sulfur-loaded sulfide molecular sieve in example 7 is too high and the content of graphene is too low, and further the conductivity of the obtained lithium sulfur battery positive electrode material is poor, and the coating property on the sulfur-loaded sulfide molecular sieve is poor, the first coulombic efficiency and the 200-cycle capacity retention rate of example 7 are lower than those of example 1.
As can be seen from Table 1, in comparative example 1, the first coulombic efficiency and the capacity retention rate at 200 weeks were lower at the current density of 1C than that of example 1, probably because the metal-containing sulfide molecular sieve was not added in comparative example 1, and S generated during the discharge process2-The lithium ion battery is easy to combine with lithium, so that the volume of an electrode material is expanded, and a product is easy to enter an electrolyte to cause the loss of active substances, so that the electrochemical performance of the material is reduced, so that the first coulombic efficiency and the 200-week capacity retention rate of the comparative example 1 are lower than those of the example 1.
As can be seen from Table 1, in comparative example 2, the specific capacity at the first discharge, the first discharge at a current density of 1C, and the first discharge at a current density of 1C, are compared with those in example 1The lower coulombic efficiency and 200-week capacity retention rate may be due to the use of hexagonal mesoporous all-silica molecular sieve, hexagonal mesoporous all-silica molecular sieve pair S in comparative example 22-Without electrostatic attraction, and S is thereby produced2-Lithium polysulfide is easily generated by combining with lithium, and is dissolved and diffused in electrolyte to cause loss of active substances, so that the electrochemical performance of the material is reduced, and compared with the embodiment 1, the comparative example 2 has lower first discharge specific capacity, first coulombic efficiency and 200-cycle capacity retention rate.
The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (38)
1. A preparation method of a lithium-sulfur battery positive electrode material is characterized by comprising the following steps:
(1) mixing a metal-containing sulfide molecular sieve with a sulfur simple substance, and heating for one time to obtain a sulfur-carrying sulfide molecular sieve;
(2) adding a coated carbon source and a carbon material into the sulfur-loaded sulfide molecular sieve, and carrying out secondary heating to obtain a lithium-sulfur battery positive electrode material;
the carbon material is any one or combination of at least two of graphene, graphite alkyne and carbon nano tube;
the coating carbon source comprises any one or the combination of at least two of polyacrylonitrile, polyvinylidene fluoride, polyoxyethylene, polymethyl methacrylate, polyvinylidene fluoride-hexafluoropropylene, polyvinyl butyral, polyvinylpyrrolidone, polypyrrole, polyaniline, polythiophene, tetrabutyl titanate and lithium phosphate;
the lithium-sulfur battery positive electrode material comprises a sulfur-carrying sulfide molecular sieve and a carbon coating layer coated outside the sulfur-carrying sulfide molecular sieve;
the lithium-sulfur battery positive electrode material also comprises a carbon material loaded on the sulfur-loaded sulfide molecular sieve;
the sulfur-bearing sulfide molecular sieve comprises a metal-containing sulfide molecular sieve and elemental sulfur arranged in pore channels of the metal-containing sulfide molecular sieve.
2. The method of claim 1, wherein the metal-containing sulfide molecular sieve has a formula of M1-MS, said M1Including any one or a combination of at least two of Fe, Cu, Co, Zn, Li, Mn and Na.
3. The method of claim 2, wherein the metal-containing sulfide molecular sieve has a formula of M1-MS, said M1Is Co.
4. The method of claim 2, wherein the metal-containing sulfide molecular sieve has a formula of M1-MS, said M comprising any one or a combination of at least two of Sb, Sn, Ga, Ge and In.
5. The method of claim 4, wherein the metal-containing sulfide molecular sieve has a formula of M1-MS, said M being Sb.
6. The method of claim 1, wherein the metal-containing sulfide molecular sieve has a pore diameter of 0.1 to 5 nm.
7. The method according to claim 1, wherein the metal-containing sulfide molecular sieve has a specific surface area of 100 to 10000m2/g。
8. The method of claim 7, wherein the metal-containing sulfide molecular sieve is a metal-containing sulfide molecular sieveThe specific surface area of (A) is 500 to 3000m2/g。
9. The preparation method according to claim 1, wherein the composition of the positive electrode material for the lithium-sulfur battery comprises the following components in percentage by mass:
50-80 wt% of sulfur-carrying sulfide molecular sieve
3 to 15 weight percent of carbon coating layer
8-20 wt% of carbon material;
the sum of the total mass percentages of the components of the lithium-sulfur battery positive electrode material is 100%.
10. The method of claim 9, wherein the sulfur-loaded sulfide molecular sieve has a composition comprising, in mass percent:
10-30 wt% of metal-containing sulfide molecular sieve
70-90 wt% of elemental sulfur;
the sum of the total mass percent of all the components of the sulfur-carrying sulfide molecular sieve is 100 percent.
11. The method of claim 1, wherein the method of preparing the metal-containing sulfide molecular sieve of step (1) comprises the steps of: will M1And mixing the source, the M source, the sulfur source and the auxiliary solvent, washing and drying an obtained product after hydrothermal treatment to obtain the metal-containing sulfide molecular sieve.
12. The method of claim 11, wherein M is1The molar ratio of the source, the M source and the sulfur source is 2-40: 4-48: 1-97.
13. The method of claim 11, wherein the M source, M1The mass ratio of the total mass of the source and the sulfur source to the auxiliary solvent is 0.5-2: 1.
14. The production method according to claim 13, wherein the M source includes any one of an Sb salt, an Sn salt, a Ga salt, a Ge salt, and an In salt or a combination of at least two thereof.
15. The production method according to claim 14, wherein the M source is any one of an Sb salt, a Ga salt, and an In salt or a combination of at least two thereof.
16. The method of claim 11, wherein M is1The source includes any one of Li salt, Fe salt, Cu salt, Co salt, Mn salt, Zn salt and Na salt or the combination of at least two of them.
17. The method of claim 16, wherein M is1The source is any one of Co salt, Li salt and Fe salt or the combination of at least two of them.
18. The method of claim 11, wherein the sulfur source comprises sulfide and/or sulfur powder.
19. The method of claim 18, wherein the sulfide includes any one of sodium sulfide, lithium sulfide, zinc sulfide, calcium sulfide, and barium sulfide or a combination of at least two thereof.
20. The method of claim 11, wherein the auxiliary solvent comprises an aqueous solution of methylamine.
21. The method according to claim 20, wherein the auxiliary solvent is present in an amount of 10 to 30 wt%.
22. The method according to claim 11, wherein the hydrothermal temperature is 100 to 200 ℃.
23. The method of claim 22, wherein the hydrothermal time is 72 to 240 hours.
24. The method according to claim 11, wherein the drying temperature is 60 to 90 ℃.
25. The method of claim 24, wherein the drying time is 8 to 12 hours.
26. The preparation method of claim 1, wherein the mass ratio of the metal-containing sulfide molecular sieve to the elemental sulfur in the step (1) is 0.5-9: 1.
27. The method of claim 26, wherein the mass ratio of the metal-containing sulfide molecular sieve to elemental sulfur is 3-9: 1.
28. The method of claim 1, wherein the metal-containing sulfide molecular sieve is mixed with elemental sulfur by attrition mixing.
29. The method according to claim 1, wherein the temperature of the primary heating is 100 to 200 ℃.
30. The method according to claim 29, wherein the time for the first heating is 5 to 48 hours.
31. The method according to claim 30, wherein the time for the first heating is 10 to 20 hours.
32. The preparation method according to claim 1, wherein the mass ratio of the sulfur-loaded sulfide molecular sieve, the coated carbon source and the carbon material in the step (2) is 10-100: 1: 5-20.
33. The method according to claim 32, wherein the mass ratio of the sulfur-loaded sulfide molecular sieve, the coated carbon source and the carbon material is 20-80: 1: 5-10.
34. The method of claim 32, wherein the coated carbon source is polypyrrole.
35. The method according to claim 1, wherein the secondary heating is carried out at a temperature of 80 to 150 ℃.
36. The method of claim 35, wherein the secondary heating is performed for 2 to 10 hours.
37. The method of preparing the positive electrode material for a lithium-sulfur battery according to claim 1, comprising the steps of:
(1) mixing Li salt, Ga salt, sulfur powder and methylamine water solution according to the molar ratio of the Li salt, the Ga salt and the sulfur powder of 2-40: 4-48: 1-97 and the mass ratio of the total mass of the Li salt, the Ga salt and the sulfur powder to the methylamine water solution with the mass fraction of 10-30 wt% of 0.5-2: 1, carrying out hydrothermal treatment at 100-200 ℃ for 72-240 h, washing the obtained product, and drying at 60-90 ℃ for 8-12 h to obtain a sulfide molecular sieve containing metal;
(2) grinding and mixing the metal-containing sulfide molecular sieve and the sulfur simple substance according to the mass ratio of the metal-containing sulfide molecular sieve to the sulfur simple substance of 3-9: 1, and heating for 10-20 hours at 100-200 ℃ to obtain a sulfur-carrying sulfide molecular sieve;
(3) and adding polypyrrole and a carbon material into the sulfur-loaded sulfide molecular sieve according to the mass ratio of 20-80: 1: 5-10 of the sulfur-loaded sulfide molecular sieve to the carbon material, and heating for 2-10 h at 80-150 ℃ to obtain the lithium-sulfur battery cathode material.
38. A lithium-sulfur battery comprising the positive electrode material for a lithium-sulfur battery produced by the production method according to any one of claims 1 to 37.
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| CN110854376B (en) * | 2019-11-27 | 2021-04-06 | 中科(马鞍山)新材料科创园有限公司 | Composite material, preparation method thereof and application thereof in lithium ion battery |
| CN114220952B (en) * | 2021-11-23 | 2022-10-28 | 高能时代(珠海)新能源科技有限公司 | Electrode material for reducing volume change of electrode in charging and discharging processes and battery |
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