A composite positive electrode material suitable for sulfide solid-state lithium batteries, a preparation method and applications thereof

Abstract

The application belongs to the technical field of lithium ion batteries, and particularly relates to a composite positive electrode material suitable for sulfide solid-state lithium batteries and a preparation method and application thereof. A sulfidation-modified positive electrode active material is modified by a liquid-solid dispersion-gas-solid reaction of a sulfur source on the positive electrode active material, so that a layer of stable sulfide interface phase is constructed on the surface of the positive electrode active material particles; the mass fraction of the sulfur source in the positive electrode active material is 0.1%-15%. The sulfidation-modified positive electrode active material is obtained by the liquid-solid dispersion-gas-solid reaction, which can realize uniform mixing of the sulfur source and the positive electrode active material and uniform sulfidation modification of the positive electrode active material, and is conducive to the construction of the stable sulfide interface phase. Meanwhile, the preparation method is simple, environmentally friendly, and easy to realize batch preparation of high-performance composite positive electrode materials.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and particularly relates to a composite positive electrode material suitable for sulfide solid-state lithium batteries and a preparation method and application thereof. BACKGROUND

[0002] Sulfide solid-state lithium batteries have potential advantages of high energy density and high safety, and are one of the development routes of advanced energy storage technologies. It should be pointed out that the composite positive electrode material composed of a positive electrode active material, a sulfide electrolyte and a conductive agent is a decisive factor affecting the electrochemical performance of the sulfide solid-state battery. In addition to the physical contact state between the components in the composite positive electrode material, such as the dispersion degree, the contact mode, the contact area, the void size and the like, which will affect the ion transmission kinetics of the positive electrode active material / sulfide electrolyte interface, the active material utilization rate and the electrochemical performance of the sulfide solid-state lithium battery, the interface chemical side reaction and the space charge layer between the positive electrode active material and the sulfide electrolyte in the composite positive electrode material will also cause the increase of the interface impedance of the positive electrode active material / sulfide electrolyte, hinder the ion interface transmission and limit the electrochemical performance of the sulfide solid-state lithium battery. Therefore, it is urgent to develop relevant countermeasures to solve the problems of interface chemical reaction and space charge layer faced by the positive electrode active material / sulfide electrolyte.

[0003] CN116230860A discloses a sulfide solid-state electrolyte oxide positive electrode material and a preparation method and application thereof. By adopting a low-speed mechanical ball milling coating process, a conductive oxide material coating layer is constructed on the outside of the oxide positive electrode particles, which effectively prevents the lattice oxygen from being released from the oxide positive electrode particles and the interface chemical side reaction between the oxide positive electrode particles and the sulfide solid-state electrolyte. However, the low-speed mechanical ball milling coating process cannot achieve uniform and dense thin layer coating of the conductive oxide material on the oxide positive electrode particles, resulting in the interface chemical side reaction between the exposed positive electrode active material and the sulfide solid-state electrolyte. In addition, there is still a large chemical potential difference between the conductive oxide coating material and the sulfide solid-state electrolyte, which causes the problem of the space charge layer between the oxide positive electrode particles and the sulfide solid-state electrolyte to be still prominent.

[0004] Wu et al. (Advanced Functional Materials, 2024, 34, 4, 2309822) used ruthenium oxide to dope the lithium-rich manganese-based positive electrode material (Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2) in the bulk phase, and used carbon disulfide as a sulfur source to use carbon disulfide vapor to dope the Li 1.2 Ni 0.13 Co 0.13 Mn 0.54O2 is sulfur-modified, forming a sulfide surface layer on the surface of the lithium-rich manganese-based positive electrode material, effectively inhibiting the interface side reaction of the positive electrode active material and the sulfide electrolyte and the adverse effect of the space charge layer on ion interface transmission. However, carbon disulfide solution has strong volatility, is flammable and explosive, and has safety risks. Moreover, using carbon disulfide to modify the lithium-rich manganese-based positive electrode material also has the disadvantage of introducing carbon impurities.

[0005] CN111697208B discloses a modified lithium ion battery positive electrode material and a preparation method thereof. Using the sublimation characteristics of solid sulfur, the lithium ion battery positive electrode material is modified by sulfurization under heating conditions, effectively improving the cycle performance and rate performance of the positive electrode material in a liquid lithium ion battery, and providing a reference for preparing a high-performance sulfide solid lithium battery composite positive electrode material. However, this method still has the problem of uneven sulfurization degree of the lithium ion battery positive electrode material, i.e. the sulfurization degree of the lithium ion battery positive electrode material near the elemental sulfur is high, and the sulfurization degree of the lithium ion battery positive electrode material far from the elemental sulfur is low.

[0006] CN115477335 A discloses a preparation method of a sulfur element modified cobalt-free lithium-rich positive electrode material. In the aqueous solution of Ni source and Mn source, anhydrous ethanol solution of elemental sulfur is added, and aqueous solution of carbonate is used as a precipitating agent. Through hydrothermal reaction and high-temperature solid-phase reaction, a cobalt-free lithium-rich positive electrode material is obtained, which is doped with elemental sulfur and coated with sulfate on the surface. The cycle stability and rate performance of the cobalt-free lithium-rich positive electrode material can be effectively improved. However, the addition of elemental sulfur anhydrous ethanol solution in this preparation method will change the coordination environment and solubility product constant of Ni and Mn ions in the aqueous solution, resulting in uneven distribution of Ni and Mn in the cobalt-free lithium-rich positive electrode material and element enrichment in local areas. Therefore, there is an urgent need for a composite positive electrode material and a preparation method thereof, which can inhibit the interface chemical reaction of the positive electrode active material / sulfide electrolyte, reduce the adverse effect of the space charge layer, and significantly improve the electrochemical performance of the sulfide solid lithium battery composite positive electrode material. SUMMARY

[0007] The present application aims to overcome the shortcomings of the prior art and provide a composite positive electrode material suitable for sulfide solid lithium batteries, a preparation method and application thereof.

[0008] To achieve the above-mentioned purposes, the technical scheme adopted by the present application is as follows:

[0009] A sulfur-modified positive electrode active material, the sulfur-modified positive electrode active material is modified by a liquid-solid dispersion-gas-solid reaction with a sulfur source to form a layer of structurally stable sulfide interface phase on the surface of the positive electrode active material particles; the mass fraction of the sulfur source in the positive electrode active material is 0.1%-15%.

[0010] Use of the sulfur-modified positive electrode active material in the preparation of a composite positive electrode material suitable for a sulfide solid-state lithium battery.

[0011] A composite positive electrode material suitable for a sulfide solid-state lithium battery, the composite positive electrode material being the sulfur-modified positive electrode active material, a sulfide electrolyte and a conductive agent in a mass ratio of 30-90:10-70:0.1-5.

[0012] The sulfur-modified positive electrode active material is prepared by dissolving elemental sulfur in an organic alcohol, adding a positive electrode active material to the solution to form a uniformly dispersed suspension, and then drying to obtain a solid powder material; the solid powder material is heated at 100-400°C under vacuum and sealed conditions to sublimate elemental sulfur, uniformly modify the positive electrode active material, and form a layer of a structurally stable sulfide interface phase on the surface of the positive electrode active material particles; wherein the sulfide interface phase contains TM-S, SO x n- An interface buffer layer of the component (TM is a transition metal element (generally Ni, Co, Mn) in the positive electrode active material; 3≤x≤4, 0

[0013] The organic alcohol is one or more of methanol, ethanol, propanol, propylene glycol, and butanol, and the elemental sulfur is one or more of dimer sulfur, trimer sulfur, tetramer sulfur, pentamer sulfur, cyclohexa sulfur, and cycloocta sulfur.

[0014] The positive electrode active material is stirred in the organic alcohol solution containing elemental sulfur at room temperature for 0.5-5h to obtain a uniformly dispersed suspension, and then vacuum dried at 40-80°C for 5-24h to obtain a solid powder material.

[0015] The positive electrode active material is a high-capacity positive electrode active material, wherein the specific capacity is generally greater than or equal to 180mAh / g.

[0016] The conductive agent is one or more of conductive carbon black (SP), carbon nanotubes, vapor-grown carbon fibers (VGCF), and graphene.

[0017] The sulfide solid-state electrolyte is one or more of Li6PS5Cl, Li3PS4, Li6PS5Br, Li 10 GeP2S 12 .

[0018] The high-capacity positive electrode active material is lithium cobaltate (LiCoO2), lithium nickel cobalt manganese oxide (LiNi a Co bMn 1-a-b O2, 0.6≤a<1, 0<b≤0.2) and lithium-rich manganese-based layered oxides (xLi2MnO3·(1-x)LiNi a Co b Mn 1-a-b O2, 0<x<1, 0.3≤a<1, 0.3≤b<1).

[0019] A preparation method of the composite cathode material suitable for sulfide solid-state lithium battery, the sulfidation modified cathode active material, the sulfide electrolyte and the conductive agent are mixed and treated by dry ball milling in proportion to realize the full contact and dispersion between the components, and the composite cathode material for the sulfide solid-state lithium battery is obtained.

[0020] The dry ball milling treatment is carried out in the ball mill, the rotation speed of the ball mill is 100-400 rpm, and the ball milling time is 0.5-5 h.

[0021] The application of the composite cathode material suitable for sulfide solid-state lithium battery, and the application of the composite cathode material in the preparation of a sulfide electrolyte full solid-state battery.

[0022] A sulfide electrolyte full solid-state battery containing the composite cathode material.

[0023] The negative electrode of the sulfide electrolyte full solid-state battery is one of a lithium metal negative electrode, a lithium-indium negative electrode, a carbon negative electrode, a silicon negative electrode and a silicon-carbon negative electrode.

[0024] The preparation of the sulfide electrolyte full solid-state battery is prepared as follows: firstly, the sulfide solid-state electrolyte powder material is placed in a solid-state battery mold and pressure is applied to form a sulfide electrolyte layer, then the composite cathode material obtained above is placed on one side of the sulfide solid-state electrolyte layer and pressure is applied, and then the negative electrode material is placed on the other side of the sulfide solid-state electrolyte layer and pressure is applied. Finally, the preparation of the sulfide electrolyte full solid-state battery is completed by a sealing rubber ring and a pressure mechanical clamp.

[0025] The present application has the following advantages:

[0026] The present application adopts a liquid-solid dispersion-gas-solid reaction mode to obtain the sulfidation modified cathode active material, which can realize the uniform mixing of the sulfur source and the cathode active material and the uniform sulfidation modification of the cathode active material, is conducive to the construction of a structure-stable sulfide interface phase, inhibits the interface chemical side reaction between the cathode active material and the sulfide electrolyte, reduces the adverse effects of the space charge layer on the electrochemical performance of the sulfide solid-state lithium battery, promotes the efficient transmission of lithium ions at the interface, and helps to improve the electrochemical performance of the sulfide solid-state lithium battery. Meanwhile, the preparation method is simple, environmentally friendly and easy to realize batch preparation of high-performance composite cathode materials. Attached Figure Description

[0027] Figure 1 The diagram shows the sulfurization modification of the positive electrode active material; (a) is a schematic diagram of the sulfurization modification of the positive electrode active material using the liquid-solid dispersion-gas-solid reaction method in Example 1; and (b) is a schematic diagram of the sulfurization modification of the positive electrode active material using the gas-solid reaction method in Comparative Example 2.

[0028] Figure 2 The images shown are SEM and EDS images of the sulfide-modified lithium-rich manganese-based cathode material in Example 1.

[0029] Figure 3 The images show (a) XPS and (b) XRD patterns of the sulfide-modified lithium-rich manganese-based cathode material in Example 1.

[0030] Figure 4 The first charge-discharge curve of the sulfide solid-state battery assembled with the composite cathode material prepared in Example 1.

[0031] Figure 5 Cyclic performance testing of sulfide solid-state batteries assembled from the composite cathode materials prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0032] The following examples further illustrate specific embodiments of the present invention. It should be noted that the specific embodiments described herein are merely for illustration and explanation and are not intended to limit the scope of the present invention.

[0033] This invention utilizes liquid-solid dispersion-gas-solid reaction to sulfide modify positive electrode active materials. By controlling the combination of substances in the positive electrode material, the amount of elemental sulfur, and the corresponding conditions, uniform sulfide modification of the positive electrode active material is achieved, resulting in the formation of a specific, uniform, and dense layer containing TM-S and SO on the surface of the positive electrode active material. x n- The sulfide coating layer of the component suppresses interfacial chemical side reactions between the positive electrode active material particles and the sulfide electrolyte, effectively eliminates the adverse effects of the space charge layer, reduces the impedance of lithium ions at the positive electrode active material / sulfide electrolyte interface, and promotes rapid lithium ion transport. Furthermore, the sulfide modification of the positive electrode active material can also regulate the oxygen vacancies and crystal structure at the surface of the positive electrode material, improving its structural stability and kinetic performance. Therefore, the sulfide-modified composite positive electrode material exhibits outstanding advantages in electrochemical performance in sulfide solid-state lithium batteries.

[0034] Example 1

[0035] The composite cathode material for sulfide solid-state batteries is a sulfur-modified lithium-rich manganese-based single-crystal cathode material (0.5Li2MnO3·0.5LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2), Li6PS5Cl sulfide electrolyte and conductive agent VGCF, wherein the mass ratio of 0.5Li2MnO3·0.5LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 cathode material, Li6PS5Cl sulfide electrolyte and conductive agent VGCF is 40:60:3.

[0036] The sulfur modification method of the composite cathode material for sulfide solid-state lithium batteries includes the following specific steps:

[0037] Step 1: 0.03 g of cyclooctasulfur (S8) is added to 300 ml of ethanol solution, and magnetic stirring is carried out at 30°C for 1 hour to promote the complete dissolution of S8 in the ethanol solution, obtaining an ethanol solution of S8.

[0038] Step 2: 3.0 g of 0.5Li2MnO3·0.5LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 cathode material is added to the above-mentioned ethanol solution of S8, and magnetic stirring is carried out at 30°C for 2 hours to obtain a solid-liquid mixture of lithium-rich manganese-based cathode and cyclooctasulfur.

[0039] Step 3: The obtained solid-liquid mixture of lithium-rich manganese-based cathode and cyclooctasulfur is transferred to a vacuum oven, and vacuum drying is carried out at 50°C for 10 hours to obtain a solid-state powder material uniformly mixed with lithium-rich manganese-based cathode and cyclooctasulfur.

[0040] Step 4: The powder obtained in the above step is placed in a quartz glass tube and subjected to vacuum sealing treatment, as shown in Figure 1 a. The sealed quartz glass tube is placed in a muffle furnace, and the heating rate is 2°C / min, the temperature is raised to 200°C and maintained for 12 hours. The sulfur-modified lithium-rich manganese-based cathode material is obtained (see Figure 2 and 3 ).

[0041] As shown in Figure 2 and 3 , the scanning electron microscope image and energy dispersive X-ray spectroscopy analysis of the sulfur-modified lithium-rich manganese-based cathode material. After the sulfur modification treatment, a sulfide interface phase containing TM-S, SO x n- components is formed on the surface of the lithium-rich manganese-based cathode material. Powder X-ray diffraction analysis shows that the lithium-rich manganese-based cathode material still maintains a good layered crystal structure after the sulfur modification treatment.

[0042] A method for preparing a composite cathode material suitable for a sulfide solid-state lithium battery: In an argon-filled glove box, 2 g of sulfur-modified lithium-rich manganese-based cathode material, 3 g of sulfide electrolyte Li6PS5Cl, and 0.15 g of conductive agent VGCF were placed in a ball milling jar, 20 pieces of zirconia milling beads with a diameter of 10 mm were placed in the jar, and the jar was ball-milled at a speed of 250 rpm for 2 hours to obtain a sulfur-modified composite cathode material. Then the obtained composite cathode material was manually ground in the glove box for 0.5 hours to obtain a composite cathode material in which the lithium-rich manganese-based single crystal cathode material, Li6PS5Cl, and VGCF were fully contacted and mixed.

[0043] Sulfide electrolyte all-solid-state battery: In an argon-filled glove box, a sulfide solid-state battery was assembled, and an all-solid-state battery was assembled using a 10 mm diameter STC-SB polyether ether ketone (PEEK) finished mold. First, 80 mg of LPSCl powder was added to the column cavity and pressed at 150 MPa for 2 min, then 10 mg of composite cathode powder was evenly laid on one side of the electrolyte sheet, and pressed at 370 MPa for 2 min, and finally a lithium-indium alloy anode composed of an indium foil (Φ=8 mm) and a lithium foil (Φ=3 mm) was placed on the other side of the electrolyte sheet and pressed at 150 MPa for 1 min. At this time, the battery formed a three-layer structure of cathode-electrolyte-anode inside, and a current collector sheet was assembled on both ends of the cathode and anode to facilitate the transfer of charge carriers. During the electrochemical test, a stainless steel press was assembled outside the battery mold to stabilize the contact between the internal components of the battery. The electrochemical test was carried out at 30℃, 2.0-4.7V (vs. Li + / Li), 0.1C (1C=200mAg -1 ).

[0044] Comparative Example 1

[0045] The composite cathode material for the sulfide solid-state battery was composed of a lithium-rich manganese-based single crystal cathode material (0.5Li2MnO3·0.5LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2), a Li6PS5Cl sulfide electrolyte, and a conductive agent VGCF, wherein the mass ratio of the lithium-rich manganese-based single crystal cathode material, the Li6PS5Cl sulfide electrolyte, and the conductive agent VGCF was 40:60:3.

[0046] The specific steps of the lithium-rich manganese-based single crystal cathode material are as follows:

[0047] Step 1: 3.0 g of lithium-rich manganese-based single crystal cathode material was added to 300 ml of ethanol solution, and the mixture was magnetically stirred at 30℃ for 2 hours to obtain a suspension of lithium-rich manganese-based single crystal cathode material.

[0048] Step 2: The obtained suspension of lithium-rich manganese-based single-crystal positive electrode material was transferred into a vacuum oven and vacuum dried at 50°C for 10 hours to obtain a solid powder of lithium-rich manganese-based single-crystal positive electrode material.

[0049] Step 3: The solid powder of lithium-rich manganese-based single-crystal positive electrode material was placed in a quartz glass tube and vacuum sealed, and the sealed quartz glass tube was placed in a muffle furnace, heated to 200°C at a heating rate of 2°C / min and maintained for 12 hours to obtain a lithium-rich manganese-based single-crystal positive electrode material.

[0050] Method for preparing a composite positive electrode material for a sulfide solid-state battery: In an argon-filled glove box, 2 g of lithium-rich manganese-based single-crystal positive electrode material, 3 g of sulfide electrolyte Li6PS5Cl, and 0.15 g of conductive agent VGCF were placed in a ball mill jar, and 20 zirconia ball milling beads with a diameter of 10 mm were placed in the jar. The mixture was ball milled at a speed of 250 rpm for 2 hours to obtain a composite positive electrode material in which the lithium-rich manganese-based composite positive electrode material, Li6PS5Cl, and VGCF were in full contact and mixed.

[0051] A sulfide solid-state battery was assembled according to the method described in Example 1: The obtained lithium-rich manganese-based sulfide composite positive electrode, Li6PS5Cl sulfide electrolyte, and lithium-indium alloy negative electrode material were assembled into a sulfide solid-state battery in an argon-filled glove box.

[0052] The sulfide solid-state batteries assembled in Example 1 and Comparative Example 1 above were respectively subjected to charge-discharge tests at 30°C, 2.0-4.7V (vs. Li + / Li), 0.1C (1C = 200 mAg -1 ) (see Figure 4 and 5 ).

[0053] As shown in Figure 4 and 5 , the first cycle discharge capacity of the sulfide solid-state lithium battery assembled in Example 1 was 175.24 mAh g -1 , the first cycle coulombic efficiency was 73.44%, and the discharge specific capacity of the solid-state lithium battery after 100 cycles was still 177.40 mAh g -1 The first cycle discharge capacity of the sulfide solid-state lithium battery assembled in Comparative Example 1 was only 76.13 mAh g -1 , the first cycle coulombic efficiency was 59.63%, and the discharge specific capacity of the solid-state lithium battery after 100 cycles was only 110.06 mAh g -1, both of which can be seen, the positive electrode material of Example 1 is obtained by sulfurization modification of the positive electrode active material particles through liquid-solid dispersion-gas-solid reaction, which overcomes the shortcomings of the prior art in introducing additional pollution sources and uneven sulfurization degree during the sulfurization treatment of the positive electrode active material, and can realize the formation of a uniform and dense sulfur-containing TM-S, SO x n- The sulfide coating layer of the component can inhibit the interfacial chemical side reaction of the positive electrode active material particles and the sulfide electrolyte and effectively eliminate the adverse effects of the space charge layer, reduce the impedance of lithium ions on the positive electrode active material / sulfide electrolyte interface, and promote the rapid transport of lithium ions. As can be seen, the battery assembled in Comparative Example 1 significantly inhibits the chemical decomposition of the sulfide electrolyte during the charge and discharge process, reduces the electrochemical polarization, promotes the rapid transport of lithium ions, and thus has higher capacity contribution and coulombic efficiency. Compared with the sulfide solid-state lithium batteries based on lithium-rich manganese-based positive electrode materials reported at home and abroad, the performance is at a leading level.

[0054] Example 2

[0055] The composite positive electrode material for sulfide solid-state batteries is a sulfurization-modified lithium-rich manganese-based single-crystal positive electrode material, a Li6PS5Cl sulfide electrolyte and a conductive agent VGCF, wherein the mass ratio of the sulfurization-modified lithium-rich manganese-based single-crystal positive electrode material, the Li6PS5Cl sulfide electrolyte and the conductive agent VGCF is 40:60:3.

[0056] The sulfurization modification method of the composite positive electrode material for sulfide solid-state lithium batteries, the specific steps are as follows:

[0057] Step 1: 0.015g of cyclooctasulfur (S8) is added to 300ml of ethanol solution, and magnetic stirring is carried out at 30℃ for 1 hour to promote the complete dissolution of S8 in the ethanol solution, obtaining an ethanol solution of S8.

[0058] Step 2: 3.0g of lithium-rich manganese-based single-crystal positive electrode material (0.5Li2MnO3·0.5LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2) is added to the above-mentioned ethanol solution of S8, and magnetic stirring is carried out at 30℃ for 2 hours to obtain a solid-liquid mixture of lithium-rich manganese-based positive electrode and cyclooctasulfur.

[0059] Step 3: The obtained solid-liquid mixture of lithium-rich manganese-based positive electrode and cyclooctasulfur is transferred to a vacuum oven, vacuum dried at 50℃ for 10 hours to obtain a solid-state powder material uniformly mixed with lithium-rich manganese-based single-crystal positive electrode and cyclooctasulfur.

[0060] Step 4: The uniformly mixed sulfur-modified lithium-rich manganese-based single-crystal cathode material and the cyclotetrasulfur solid powder material were placed in a quartz glass tube and vacuum sealed. The sealed quartz glass tube was placed in a muffle furnace and heated to 200°C at a heating rate of 2°C / min and maintained for 12 hours to obtain the sulfur-modified lithium-rich manganese-based single-crystal cathode material.

[0061] The preparation method of the composite cathode material suitable for the sulfide solid-state lithium battery: In an argon-filled glove box, 2 g of the sulfur-modified lithium-rich manganese-based single-crystal cathode material obtained above, 3 g of the sulfide electrolyte Li6PS5Cl, and 0.15 g of the conductive agent VGCF were placed in a ball mill jar, and 20 zirconia milling beads with a diameter of 10 mm were placed in the jar. The ball mill was operated at a speed of 250 rpm for 2 hours to obtain the sulfur-modified composite cathode material. Then, the obtained composite cathode material was manually ground in the glove box for 0.5 hours to obtain the composite cathode material in which the lithium-rich manganese-based single-crystal cathode material, Li6PS5Cl, and VGCF were fully contacted and mixed.

[0062] The sulfide solid-state battery was assembled as described in Example 1 and subjected to charge-discharge test at 30°C, 2.0-4.7V (vs. Li + / Li), 0.1C (1C = 200 mAg -1 ). The assembled sulfide solid-state lithium battery had a first cycle discharge capacity of 168.3 mAh g -1 and a first cycle coulombic efficiency of 72.2%.

[0063] Example 3

[0064] The composite cathode material for the sulfide solid-state battery is the sulfur-modified lithium-rich manganese-based single-crystal cathode material, the Li6PS5Cl sulfide electrolyte, and the conductive agent VGCF, wherein the mass ratio of the sulfur-modified lithium-rich manganese-based single-crystal cathode material, the Li6PS5Cl sulfide electrolyte, and the conductive agent VGCF is 40:60:3.

[0065] The sulfur-modification method of the composite cathode material for the sulfide solid-state lithium battery includes the following specific steps:

[0066] Step 1: 0.045 g of cyclotetrasulfur (S8) was added to 300 ml of ethanol solution, and the solution was magnetically stirred at 30°C for 1 hour to ensure that S8 was completely dissolved in the ethanol solution to obtain an ethanol solution of S8.

[0067] Step 2: 3.0 g of the lithium-rich manganese-based single-crystal cathode material (0.5Li2MnO3·0.5LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2) is added into the above S8 ethanol solution, and the mixture is stirred magnetically at 30℃ for 2 hours to obtain a solid-liquid mixture of lithium-rich manganese-based single-crystal cathode material and cyclooctasulfur.

[0068] Step 3: The obtained solid-liquid mixture of lithium-rich manganese-based single-crystal cathode material and cyclooctasulfur is transferred into a vacuum oven, and vacuum drying is performed at 50℃ for 10 hours to obtain a solid powder material of lithium-rich manganese-based single-crystal cathode material and cyclooctasulfur which are fully dispersed and mixed.

[0069] Step 4: The solid powder material of lithium-rich manganese-based single-crystal cathode material and cyclooctasulfur which are fully dispersed and mixed is placed in a quartz glass tube and vacuum sealed, and the sealed quartz glass tube is placed in a muffle furnace, heated to 220℃ at a heating rate of 2℃ / min, and maintained for 8 hours to obtain a sulfur-modified lithium-rich manganese-based single-crystal cathode material.

[0070] The preparation method of the composite cathode material suitable for the sulfide solid-state lithium battery is as follows: in an argon-filled glove box, 2g of the sulfur-modified lithium-rich manganese-based single-crystal cathode material, 3g of the sulfide electrolyte Li6PS5Cl, and 0.15g of the conductive agent VGCF are placed in a ball mill jar, and 20 pieces of zirconia ball milling beads with a diameter of 10mm are placed therein, and ball milling is performed at a rotation speed of 200rpm for 3 hours to obtain a sulfur-modified composite cathode material. Then, the obtained composite cathode material is manually ground in the glove box for 0.5 hours to obtain a composite cathode material in which the components of lithium-rich manganese-based single-crystal cathode material, Li6PS5Cl, and VGCF are fully contacted and mixed.

[0071] The sulfide solid-state battery is assembled according to the method described in Example 1, and is subjected to charge-discharge test at 30℃, 2.0-4.7V (vs. Li + / Li), 0.1C (1C=200mAg -1 ). The assembled sulfide solid-state lithium battery has a first cycle discharge capacity of 170.0mAh g -1 , and a first cycle coulombic efficiency of 74.1%.

[0072] Example 4

[0073] The composite cathode material for the sulfide solid-state battery is a sulfur-modified lithium cobalt oxide cathode material (LiCoO2), Li 10 GeP2S 12 sulfide electrolyte, and a conductive agent SP, wherein the mass ratio of the sulfur-modified lithium cobalt oxide cathode material, Li 10 GeP2S 12 sulfide electrolyte, and the conductive agent SP is 70:30:3.

[0074] The sulfur modification method of the composite cathode material for the sulfide solid-state lithium battery includes the following steps:

[0075] Step 1: 0.03 g of octasulfur (S8) was added into 300 ml of ethanol solution, and stirred magnetically at 30 °C for 1 hour to make S8 completely dissolved in the ethanol solution, obtaining an ethanol solution of S8.

[0076] Step 2: 3.0 g of lithium cobalt oxide positive electrode material was added into the above ethanol solution of S8, and stirred magnetically at 30 °C for 2 hours to obtain a solid-liquid mixture of lithium cobalt oxide positive electrode material and octasulfur.

[0077] Step 3: The obtained solid-liquid mixture of lithium cobalt oxide positive electrode material and octasulfur was transferred into a vacuum oven, and vacuum dried at 55 °C for 12 hours to obtain a solid powder material of lithium cobalt oxide positive electrode material and octasulfur fully dispersed and mixed.

[0078] Step 4: The solid powder material of lithium cobalt oxide positive electrode material and octasulfur fully dispersed and mixed was placed in a quartz glass tube and vacuum sealed, and the sealed quartz glass tube was placed in a muffle furnace, heated to 190 °C at a heating rate of 2 °C / min, and maintained for 20 hours to obtain a sulfurized modified lithium cobalt oxide positive electrode material.

[0079] Preparation method of composite positive electrode material suitable for sulfide solid-state lithium battery: in an argon-filled glove box, 2.1 g of sulfurized modified lithium cobalt oxide positive electrode material, 0.9 g of sulfide electrolyte Li 10 GeP2S 12 , 0.09 g of conductive agent SP were placed in a ball mill jar, and 20 zirconia milling beads with a diameter of 10 mm were placed, and ball milled at a speed of 200 rpm for 5 hours to obtain a sulfurized modified composite positive electrode material. Then the obtained composite positive electrode material was manually ground in the glove box for 0.5 hours to obtain a composite positive electrode material in which the components of lithium cobalt oxide positive electrode material, Li 10 GeP2S 12 and SP were in full contact and mixed.

[0080] A sulfide solid-state battery was assembled according to the description in Example 1, and was subjected to charge-discharge test at 30 °C, 2.5-4.2 V (vs. Li + / Li), 0.1 C (1 C = 140 mAg -1 ). The assembled sulfide solid-state lithium battery had a first circle discharge capacity of 115.0 mAh g -1 , and a first circle coulombic efficiency of 86.7%.

[0081] Example 5

[0082] The composite cathode material for sulfide solid-state batteries is a sulfidation modified lithium cobaltate cathode material (LiCoO2), a Li6PS5Cl sulfide electrolyte, and a conductive agent VGCF, wherein the mass ratio of the sulfidation modified lithium cobaltate cathode material, the Li6PS5Cl sulfide electrolyte, and the conductive agent VGCF is 70:30:3.

[0083] The sulfidation modification method of the composite cathode material for sulfide solid-state lithium batteries includes the following specific steps:

[0084] Step 1: 0.045 g of disulfide (S2) is added to 300 ml of propylene glycol solution, and magnetic stirring is performed at 30°C for 1 hour to promote complete dissolution of S2 in the propylene glycol solution, obtaining a propylene glycol solution of S2.

[0085] Step 2: 3.0 g of lithium cobaltate cathode material is added to the above-mentioned propylene glycol solution of S2, and magnetic stirring is performed at 30°C for 2 hours, obtaining a solid-liquid mixture of lithium cobaltate cathode material and disulfide.

[0086] Step 3: The obtained solid-liquid mixture of lithium cobaltate cathode material and disulfide is transferred to a vacuum oven, and vacuum drying is performed at 55°C for 12 hours, obtaining a solid-state powder material of fully dispersed and mixed lithium cobaltate cathode material and disulfide.

[0087] Step 4: The fully dispersed and mixed solid-state powder material of lithium cobaltate cathode material and disulfide is placed in a quartz glass tube and subjected to vacuum sealing treatment, and the sealed quartz glass tube is placed in a muffle furnace, heated to 190°C at a heating rate of 2°C / min, and maintained for 20 hours, obtaining a sulfidation modified lithium cobaltate cathode material.

[0088] The preparation method of the composite cathode material suitable for sulfide solid-state lithium batteries: in an argon-filled glove box, 2.1 g of sulfidation modified lithium cobaltate cathode material, 0.9 g of sulfide electrolyte Li6PS5Cl, and 0.09 g of conductive agent VGCF are placed in a ball mill jar, and 20 zirconia milling beads with a diameter of 10 mm are placed, and ball milling is performed at a speed of 200 rpm for 5 hours, obtaining a sulfidation modified composite cathode material. Then the obtained composite cathode material is manually ground in the glove box for 0.5 hours, obtaining a composite cathode material in which the components of lithium nickel cobalt manganese oxide, Li6PS5Cl, and SP are fully contacted and mixed.

[0089] According to the method described in Example 1, a sulfide solid-state battery is assembled, and charge-discharge test is performed at 30°C, 2.5-4.2V (vs. Li + / Li), 0.1C (1C=140mAg -1 ). The assembled sulfide solid-state lithium battery has a first circle discharge capacity of 111.0mAh g -1, the first circle Coulombic efficiency is 83.6%.

[0090] Example 6

[0091] The composite cathode material for the sulfide solid-state battery is a sulfur-modified lithium nickel cobalt manganese oxide cathode material (LiNi 0.8 Co 0.1 Mn 0.1 O2), Li6PS5Cl sulfide electrolyte and conductive agent VGCF, wherein the mass ratio of the sulfur-modified lithium nickel cobalt manganese oxide cathode material, Li6PS5Cl sulfide electrolyte and conductive agent VGCF is 70:30:3.

[0092] The method for sulfur modification of the composite cathode material for the sulfide solid-state lithium battery comprises the following specific steps:

[0093] Step 1: 0.015g of cyclooctasulfur (S8) is added to 300ml of propylene glycol solution, and magnetic stirring is carried out at 30°C for 1 hour to promote complete dissolution of S8 in the propylene glycol solution, obtaining a propylene glycol solution of S8.

[0094] Step 2: 3.0g of lithium nickel cobalt manganese oxide cathode material is added to the above-mentioned propylene glycol solution of S8, and magnetic stirring is carried out at 30°C for 2 hours, obtaining a solid-liquid mixture of lithium nickel cobalt manganese oxide cathode material and cyclooctasulfur.

[0095] Step 3: The obtained solid-liquid mixture of lithium nickel cobalt manganese oxide cathode material and cyclooctasulfur is transferred to a vacuum oven, and vacuum drying is carried out at 55°C for 12 hours, obtaining a solid-state powder material of lithium nickel cobalt manganese oxide cathode material and cyclooctasulfur fully dispersed and mixed.

[0096] Step 4: The solid-state powder material of lithium nickel cobalt manganese oxide cathode material and cyclooctasulfur fully dispersed and mixed is placed in a quartz glass tube and subjected to vacuum sealing treatment, and the sealed quartz glass tube is placed in a muffle furnace, heated to 200°C at a heating rate of 2°C / min, and maintained for 20 hours, obtaining a sulfur-modified lithium nickel cobalt manganese oxide cathode material.

[0097] The preparation method of the composite cathode material suitable for the sulfide solid-state lithium battery: in an argon-filled glove box, 2.1g of the sulfur-modified lithium nickel cobalt manganese oxide cathode material, 0.9g of the sulfide electrolyte Li6PS5Cl and 0.09g of the conductive agent VGCF are placed in a ball mill jar, and 20 zirconia ball milling beads with a diameter of 10mm are placed, and ball milling is carried out at a speed of 200rpm for 5 hours, obtaining a sulfur-modified composite cathode material. Then the obtained composite cathode material is manually ground in the glove box for 0.5 hours, obtaining a composite cathode material in which the components of lithium nickel cobalt manganese oxide cathode material, Li6PS5Cl and VGCF are fully contacted and mixed.

[0098] A sulfide solid-state battery was assembled according to Example 1 and tested at 30°C and 3.0-4.3V (vs. Li). + / Li), 0.1C (1C=200mAg) -1 Under these conditions, charge-discharge tests were conducted. The assembled sulfide solid-state lithium battery achieved a first-cycle discharge capacity of 143.1 mAh g. -1 The first lap efficiency was 82.2%.

[0099] Comparative Example 2

[0100] The composite cathode material for sulfide solid-state batteries consists of sulfide-modified lithium-rich manganese-based monocrystalline cathode material, Li6PS5Cl sulfide electrolyte, and conductive agent VGCF, wherein the mass ratio of sulfide-modified lithium-rich manganese-based monocrystalline cathode material, Li6PS5Cl sulfide electrolyte, and conductive agent VGCF is 40:60:3.

[0101] The specific steps for using composite cathode materials in sulfide solid-state lithium batteries are as follows:

[0102] Step 1: Place 0.03g of cyclooctasulfide (S2) in quartz tube 1, and add 3.0g of lithium-rich manganese-based single-crystal cathode material (0.5Li2MnO3·0.5LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2) is placed inside quartz tube 2, such as Figure 1 As shown in b.

[0103] Step 2: Vacuum seal the quartz glass tube 2 and place it in a muffle furnace. Heat it to 200℃ at a heating rate of 2℃ / min and maintain the temperature for 12 hours. Sulfide-modified lithium-rich manganese-based cathode material is obtained.

[0104] Step 3: In an argon-filled glove box, place 2g of sulfur-modified lithium-rich manganese-based cathode material, 3g of sulfurized electrolyte Li6PS5Cl, and 0.15g of conductive agent VGCF into a ball mill jar, and place 20 zirconium oxide grinding balls with a diameter of 10mm. Grind at 250rpm for 2 hours to obtain sulfur-modified composite cathode material.

[0105] The obtained composite cathode material was then manually ground in a glove box for 0.5 hours to obtain a composite cathode material in which lithium-rich manganese-based cathode material, Li6PS5Cl and VGCF components were fully contacted and mixed.

[0106] Sulfide solid-state battery: The obtained sulfur-modified lithium-rich manganese-based sulfide composite cathode, Li6PS5Cl sulfide electrolyte, and lithium-indium alloy anode material are assembled into a sulfide solid-state battery in an argon-filled glove box.

[0107] The assembled sulfide solid-state battery was subjected to charge-discharge test at 30℃, 2.0-4.7V (vs. Li + / Li), 0.1C (1C=200mAg -1 ) rate condition. The discharge capacity of the first cycle of the assembled sulfide solid-state lithium battery was 110.51mAh g -1 , the coulombic efficiency of the first cycle was 68.82%, and the discharge specific capacity of the solid-state lithium battery after 100 cycles was 121.06mAh g -1 Compared with the battery assembled by the positive active material of the application using liquid-solid dispersion-gas-solid reaction, although a sulfide coating layer was formed in both, the degree of sulfurization of elemental S on the lithium-rich manganese-based single crystal positive material in Comparative Example 2 was not uniform, resulting in that the sulfide coating layer could not uniformly coat the surface of the positive material. However, the positive material in the application example could be uniformly sulfurized by elemental S, the formed sulfide coating layer could uniformly coat the surface of the positive material, inhibit the interface chemical side reaction of the positive active material particles and the sulfide electrolyte and eliminate the adverse effects of the space charge layer, reduce the impedance of lithium ions on the positive active material / sulfide electrolyte interface, and promote the rapid transport of lithium ions. In addition, the sulfurization modification treatment of the positive active material could also realize the regulation of the surface interface oxygen vacancy and crystal structure of the positive material, and improve the structural stability and kinetic performance of the positive active material.

[0108] The composition and electrochemical performance of the composite positive material of each of the above examples and comparative examples are shown in Table 1.

[0109] Table 1

[0110]

Claims

1. A sulfidation-modified positive electrode active material, characterized by: The sulfur-modified positive electrode active material is modified by liquid-solid dispersion-gas-solid reaction with a sulfur source, so that a layer of stable sulfide interface phase is constructed on the surface of the positive electrode active material particles; the mass fraction of the sulfur source in the positive electrode active material is 0.1%-15%. The sulfur-modified positive electrode active material is obtained by dissolving elemental sulfur in an organic alcohol, uniformly dispersing the positive electrode active material in the solution to obtain a suspension, and then drying to obtain a solid powder material; the elemental sulfur is sublimated under vacuum and sealing at 100-400℃, and the positive electrode active material is uniformly modified by sulfurization to construct a layer of stable sulfide interface phase on the surface of the positive electrode active material particles.

2. Use of the sulfϊdation-modified positive electrode active material according to claim 1, characterized by: The sulfur-modified positive electrode active material is used for preparing a composite positive electrode material suitable for sulfide solid-state lithium batteries.

3. A composite cathode material suitable for use in a sulfide solid-state lithium battery, characterized in that: The composite positive electrode material is prepared according to the mass ratio of 30-90:10-70: 0.1-5 of the sulfur-modified positive electrode active material of claim 1, a sulfide electrolyte, and a conductive agent.

4. The composite cathode material suitable for sulfide solid-state lithium battery according to claim 3, characterized in that: The sulfur-modified positive electrode active material is obtained by dissolving elemental sulfur in an organic alcohol, uniformly dispersing the positive electrode active material in the solution to obtain a suspension, and then drying to obtain a solid powder material; the elemental sulfur is sublimated under vacuum and sealing at 100-400℃, and the positive electrode active material is uniformly modified by sulfurization to construct a layer of stable sulfide interface phase on the surface of the positive electrode active material particles; the mass fraction of the elemental sulfur in the positive electrode active material is 0.1%-15%.

5. The composite cathode material suitable for use in sulfide solid-state lithium batteries according to claim 4, characterized in that: The organic alcohol is one or more of methanol, ethanol, propanol, propylene glycol, and butanol; the elemental sulfur is one or more of dimer sulfur, trimer sulfur, tetramer sulfur, pentamer sulfur, cyclohexasulfur, and cyclooctasulfur.

6. The composite cathode material suitable for sulfide solid-state lithium battery according to claim 4, characterized in that: The positive electrode active material is stirred in the organic alcohol solution containing elemental sulfur at room temperature for 0.5-5 h to obtain a uniformly dispersed suspension, and then vacuum dried at 40-80℃ for 5-24 h to obtain a solid powder material.

7. The composite positive electrode material suitable for sulfide solid-state lithium batteries according to claim 3 or 4, characterized in that: The positive electrode active material is a high-capacity positive electrode active material; The conductive agent is one or more of conductive carbon black SP, carbon nanotubes, vapor-grown carbon fiber VGCF, and graphene; The sulfide solid-state electrolyte is one or more of Li6PS5CI, Li3PS4, Li6PS5Br, Li 10 GeP2S 12 one or more of Li6PS5CI, Li3PS4, Li6PS5Br, Li 8. A method of preparing the composite cathode material for use in sulfide solid-state lithium batteries according to claim 3, characterized by: The sulfur-modified positive electrode active material of claim 1, a sulfide electrolyte, and a conductive agent are mixed in the above proportions by dry ball milling to realize sufficient contact and dispersion among the components, and a composite positive electrode material for sulfide solid-state lithium batteries is obtained.

9. Use of the composite cathode material of claim 3 for a sulfide solid-state lithium battery, characterized in that: The composite positive electrode material suitable for sulfide solid-state lithium batteries is used for preparing a sulfide electrolyte full-solid-state battery.

10. A sulfide electrolyte all-solid-state battery characterized by: The composite positive electrode material of claim 3.

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