A sulfide all-solid-state battery positive electrode material and a preparation method and application thereof
By coating the surface of sulfide solid electrolyte with a metal fluoride layer, the environmental sensitivity and instability of sulfide solid electrolyte materials in dry electrode preparation are solved, enabling efficient preparation and low-cost production of all-solid-state batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SVOLT ENERGY TECH (WUXI) CO LTD
- Filing Date
- 2023-09-26
- Publication Date
- 2026-07-24
AI Technical Summary
Sulfide solid electrolyte materials are environmentally sensitive and unstable with cathode materials in dry electrode preparation, resulting in low preparation efficiency and high cost. Existing improvement schemes have failed to solve these two problems at the same time.
A sulfide solid electrolyte is prepared by coating a metal fluoride layer onto the surface of the sulfide electrolyte through a solid-phase reaction, which isolates it from air contact and avoids direct contact with the positive electrode material. The preparation process is carried out in a non-glovebox environment.
This improves the air stability of sulfide solid electrolytes, alleviates instability with cathode materials, reduces preparation difficulty and cost, and provides an effective way for the industrialization of all-solid-state batteries.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a sulfide all-solid-state battery cathode material, its preparation method, and its application. Background Technology
[0002] With the vigorous development of new energy vehicles, the demand for lithium-ion batteries is also increasing. Lithium-ion batteries consist of three parts: a positive electrode, a negative electrode, and an electrolyte. The positive electrode, as one of the most critical components, has attracted widespread attention and exploration from researchers. Wet coating is currently one of the most common methods for preparing positive electrode sheets. After wet coating, high-temperature drying is required to remove the solvent, leading to excessive energy consumption and high costs. Furthermore, the battery solvent is primarily N-methylpyrrolidone (NMP), and the volatilization and leakage of NMP during drying can pollute the environment, necessitating careful recycling and further increasing the difficulty and production cost of positive electrode preparation. In contrast to wet coating, dry electrode technology directly rolls the mixed positive electrode material into sheets and then composites it with a current collector. The entire process does not require the use of organic solvents, significantly reducing the difficulty and production cost of positive electrode sheet preparation. Moreover, unlike liquid batteries, all-solid-state battery systems do not use any liquid substances. However, to achieve lithium-ion transport, solid-state battery materials with high ionic conductivity and high ion transport number must be added to the positive electrode sheet.
[0003] The process of dry electrode preparation in all-solid-state batteries involves mixing solid electrolyte materials and cathode materials, rolling them into sheets, and then combining them with current collectors. Sulfides, with their high ionic conductivity and soft texture, are often used as solid electrolyte materials in dry electrodes. However, sulfide solid electrolyte materials also have unavoidable problems. First, they are very sensitive to the environment and can only be stored in a glove box. Consequently, dry electrodes can only be prepared in a glove box, which greatly restricts the preparation efficiency and environment of dry electrodes. Second, the instability between sulfide solid electrolytes and cathode materials in dry electrodes leads to poor electrochemical performance.
[0004] To address the two issues raised above regarding sulfide solid electrolytes as electrolyte materials for dry-process electrodes, researchers have made numerous improvements. For the problem that sulfide solid electrolytes are highly sensitive to the environment and can only be stored in a glove box, thus limiting dry-process electrode fabrication to this environment, researchers have doped the sulfides with different elements to continuously improve their air stability, attempting to transition the sulfide solid electrolyte from a glove box environment (H₂O ≤ 0.01 ppm, O₂ ≤ 0.01 ppm) to a dry room environment (dew point -40°C). Regarding the instability between sulfide solid electrolytes and cathode materials, researchers have implemented a series of coatings on the cathode material to prevent direct contact between the cathode material and the sulfide electrolyte, mitigating its instability. However, none of these solutions can simultaneously solve both problems; they must be implemented step-by-step, which significantly increases the cost and efficiency of battery manufacturing.
[0005] Therefore, how to solve the two problems of sulfide solid electrolytes as dry electrode electrolyte materials in one step, improve their air stability, and at the same time alleviate their instability with the cathode material, is a technical problem that urgently needs to be solved. Summary of the Invention
[0006] To address the shortcomings of existing technologies, the present invention aims to provide a sulfide-based all-solid-state battery cathode material, its preparation method, and its applications. This invention coats a sulfide solid electrolyte with a layer of metal fluoride. On one hand, the stable metal fluoride effectively isolates the sulfide from direct contact with air, significantly improving its air stability and alleviating the air sensitivity issue of the sulfide solid electrolyte. On the other hand, the metal fluoride coating layer prevents direct contact between the sulfide solid electrolyte and the cathode material, mitigating the instability between the cathode material and the electrolyte. This provides an effective approach for the industrialization of all-solid-state batteries.
[0007] To achieve this objective, the present invention adopts the following technical solution:
[0008] In a first aspect, the present invention provides a sulfide all-solid-state battery cathode material, the sulfide all-solid-state battery cathode material comprising a cathode active material and a composite sulfide solid electrolyte;
[0009] The composite sulfide solid electrolyte includes a sulfide solid electrolyte matrix and a metal fluoride layer coating the surface of the sulfide solid electrolyte matrix.
[0010] This invention coats a sulfide solid electrolyte with a layer of metal fluoride. On the one hand, the stable metal fluoride effectively isolates the sulfide from direct contact with air, greatly improving its air stability and alleviating the problem of the sulfide solid electrolyte's sensitivity to air. On the other hand, the metal fluoride coating layer can prevent the sulfide solid electrolyte from directly contacting the cathode material, alleviating the instability between the cathode material and the electrolyte. This provides an effective approach for the industrialization of all-solid-state batteries.
[0011] As a preferred technical solution of the present invention, the mass ratio of the positive electrode active material to the composite sulfide solid electrolyte is (5-8):(5-2), wherein the positive electrode active material is selected from the range of "5-8", which can be, for example, 5, 6, 7 or 8, and the composite sulfide solid electrolyte is selected from the range of "5-2", which can be, for example, 2, 3, 4 or 5.
[0012] In this invention, if the mass ratio of the positive electrode active material to the composite sulfide solid electrolyte is too small, that is, if the amount of composite sulfide solid electrolyte is too large, then there will be too much sulfide electrolyte between the positive electrode materials; if the mass ratio of the positive electrode active material to the composite sulfide solid electrolyte is too large, that is, if the amount of composite sulfide solid electrolyte is too small, then the composite positive electrode's ability to conduct ions will be slower, because the sulfide electrolyte plays the role of conducting ions.
[0013] Preferably, the thickness of the metal fluoride layer is 2-5 nm, for example, it can be 2 nm, 3 nm or 4 nm.
[0014] In this invention, if the metal fluoride layer is too thin, the sulfide electrolyte will come into direct contact with the positive electrode material, resulting in adverse side reactions and poor cycling performance; if the metal fluoride layer is too thick, the conductivity of the sulfide electrolyte will decrease after coating due to the weak conductivity of lithium ions in the metal fluoride, resulting in the inability to fully release the capacity.
[0015] As a preferred embodiment of the present invention, the sulfide solid electrolyte matrix includes Li7P3S. 11 , β-Li3PS4, Li6PS5Cl, Li6PS5Br, Li7P2S8I, Li4PS4I, Li6PS5Cl x Br 1-x Li6PS5Cl y I 1-y or Li6PS5Br z I 1-zAny combination of one or at least two of the following, where 0≤x≤1, 0≤y≤1, 0≤z≤1, and the values of x can be, for example, 0, 0.2, 0.4, 0.6, 0.8, or 1, the values of y can be, for example, 0, 0.2, 0.4, 0.6, 0.8, or 1, and the values of z can be, for example, 0, 0.2, 0.4, 0.6, 0.8, or 1.
[0016] Preferably, the material of the metal fluoride layer includes any one or a combination of at least two of ferrous fluoride, cobalt fluoride, manganese fluoride, or nickel fluoride.
[0017] Preferably, the positive electrode active material includes any one or a combination of at least two of lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium cobalt oxide, or lithium manganese oxide.
[0018] In a second aspect, the present invention provides a method for preparing a sulfide all-solid-state battery cathode material as described in the first aspect, the method comprising the following steps:
[0019] (1) Mix metal fluoride and sulfide solid electrolyte matrix and sinter to obtain composite sulfide solid electrolyte;
[0020] (2) The composite sulfide solid electrolyte and the positive electrode active material are mixed to obtain the sulfide all-solid-state battery positive electrode material.
[0021] In the preparation method provided by the present invention, the sulfide electrolyte is coated with metal fluoride by solid-phase reaction. This method is simple to operate and is conducive to large-scale industrial preparation. The sulfide electrolyte coated with metal fluoride of appropriate thickness can effectively prevent the sulfide electrolyte from direct contact with the positive electrode material and avoid the generation of side reactions.
[0022] As a preferred technical solution of the present invention, the mixing method in step (1) includes ball milling.
[0023] Preferably, the ball milling rate is 300-500 rpm, for example, 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm, and the time is 20-40 min, for example, 20 min, 25 min, 30 min, 35 min or 40 min.
[0024] Preferably, the sintering temperature in step (1) is 150-250℃, for example, it can be 150℃, 175℃, 200℃, 225℃ or 250℃.
[0025] In this invention, if the sintering temperature is too low, the fluoride electrolyte cannot be tightly coated onto the sulfide electrolyte; if the sintering temperature is too high, the metal fluoride will diffuse into the crystal structure of the sulfide electrolyte, resulting in adverse changes to its performance.
[0026] Preferably, the sintering time in step (1) is 1-3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.
[0027] Preferably, based on the mass of the sulfide solid electrolyte matrix, the mass content of the metal fluoride in step (1) is 0.1-1 wt.%, for example, it can be 0.1 wt.%, 0.3 wt.%, 0.5 wt.%, 0.7 wt.%, 0.9 wt.%, or 1 wt.%.
[0028] In this invention, if the mass content of metal fluoride is too small, the thickness of the metal fluoride layer will be too thin, which will cause the sulfide electrolyte to come into direct contact with the positive electrode material, resulting in unfavorable side reactions and poor cycling performance. If the mass content of metal fluoride is too large, the thickness of the metal fluoride layer will be too thick. Since the lithium-ion conductivity of metal fluoride is weak, the conductivity of the sulfide electrolyte after coating will decrease, resulting in the inability to fully release the capacity.
[0029] As a preferred technical solution of the present invention, the preparation step of the metal fluoride in step (1) includes:
[0030] (a) Mixing a metal oxide with a reducing gas to carry out a reduction reaction yields a metallic element;
[0031] (b) The metal element and the fluorine-containing gas are mixed and subjected to a fluorination reaction to obtain a metal fluoride.
[0032] Preferably, the metal oxide in step (a) includes any one or a combination of at least two of Fe2O3, CoO, MnO2 or NiO2.
[0033] Preferably, the reducing gas in step (a) includes any one or a combination of at least two of hydrogen, carbon monoxide, hydrogen sulfide, or methane, with hydrogen being the most preferred.
[0034] In this invention, the mechanism equation for the reduction reaction can be, for example, Fe2O3 + H2↑ = Fe + H2O↑.
[0035] Preferably, the reduction reaction in step (a) is carried out in a protective atmosphere.
[0036] Preferably, the gas in the protective atmosphere includes argon.
[0037] Preferably, the temperature of the reduction reaction in step (a) is 500-700℃, for example, it can be 500℃, 550℃, 600℃, 650℃ or 700℃.
[0038] Preferably, the reduction reaction time in step (a) is 8-12 min, for example, it can be 8 min, 9 min, 10 min, 11 min or 12 min.
[0039] In this invention, the mechanistic equation for the fluorination reaction can be, for example, 3Fe + 2NF3 = 3FeF2 + N2↑.
[0040] Preferably, the fluorine-containing gas in step (b) includes any one or a combination of at least two of nitrogen trifluoride, hexafluoroethane, octafluoropropane, octafluorocyclobutane, or hexafluorobutadiene.
[0041] Preferably, the temperature of the fluorination reaction in step (b) is 200-400°C, for example, it can be 200°C, 250°C, 300°C, 350°C or 400°C.
[0042] Preferably, the fluorination reaction time in step (b) is 10-20 min, for example, 10 min, 12 min, 14 min, 16 min, 18 min or 20 min.
[0043] As a preferred technical solution of the present invention, a conductive agent and a binder are also added during the mixing process in step (2).
[0044] The present invention does not specifically limit the type of conductive agent. For example, it may be acetylene black, Ketjen black, Super-P, carbon nanotubes or graphene, etc.
[0045] The present invention does not specifically limit the type of adhesive. For example, it may be polytetrafluoroethylene, vinylidene fluoride, guar gum, sodium alginate, or carboxymethyl cellulose.
[0046] Preferably, based on the mass of the sulfide all-solid-state battery cathode material, the mass fraction of the conductive agent is 0.2-0.6%, for example, it can be 0.2%, 0.3%, 0.4%, 0.5% or 0.6%, etc.
[0047] Preferably, based on the mass of the sulfide all-solid-state battery cathode material, the mass fraction of the binder is 0.2-0.6%, for example, it can be 0.2%, 0.3%, 0.4%, 0.5% or 0.6%, etc.
[0048] Preferably, the specific steps of mixing in step (2) include:
[0049] The composite sulfide solid electrolyte and the positive electrode active material are ball-milled once, then a conductive agent is added for a second ball milling, and finally a binder is added for grinding.
[0050] This invention enables the composite sulfide solid electrolyte, positive electrode active material, conductive agent and conductive agent to be uniformly dispersed through a single ball milling, a second ball milling and grinding process.
[0051] As a preferred technical solution of the present invention, the preparation method includes the following steps:
[0052] (I) Mix metal oxide and reducing gas, and carry out reduction reaction in a protective atmosphere to obtain elemental metal;
[0053] The reduction reaction temperature is 500-700℃, and the reduction reaction time is 8-12 min;
[0054] (II) The metal element and the fluorine-containing gas are mixed to carry out a fluorination reaction to obtain a metal fluoride;
[0055] The fluorination reaction is carried out at a temperature of 200-400℃ for 10-20 minutes.
[0056] (III) Mix the metal fluoride and sulfide solid electrolyte matrix by ball milling at 300-500 rpm for 20-40 min, and then sinter at 150-250℃ for 1-3 h to obtain the composite sulfide solid electrolyte.
[0057] The mass content of metal fluoride is 0.1-1 wt.%, based on the mass of the sulfide solid electrolyte matrix.
[0058] (IV) The composite sulfide solid electrolyte and positive electrode active material are ball-milled once, then a conductive agent is added for a second ball milling, and then a binder is added for grinding. After grinding, the sulfide all-solid-state battery positive electrode material is obtained.
[0059] The first ball milling process involves a rotation speed of 400-500 rpm and a time of 20-40 minutes; the second ball milling process involves a rotation speed of 400-500 rpm and a time of 30-50 minutes.
[0060] In this invention, the rotation speed of a single ball milling is 400-500 rpm, for example, 400 rpm, 420 rpm, 440 rpm, 460 rpm, 480 rpm or 500 rpm, and the time is 20-40 min, for example, 20 min, 25 min, 30 min, 35 min or 40 min.
[0061] In this invention, the rotation speed of the secondary ball mill is 400-500 rpm, for example, 400 rpm, 420 rpm, 440 rpm, 460 rpm, 480 rpm or 500 rpm, and the time is 30-50 min, for example, 30 min, 235 min, 40 min, 45 min or 50 min.
[0062] The present invention does not specifically limit the grinding time; for example, it may be 40 minutes.
[0063] Thirdly, the present invention provides a sulfide all-solid-state battery positive electrode, wherein the sulfide all-solid-state battery positive electrode is obtained by combining a positive electrode current collector and the sulfide all-solid-state battery positive electrode material described in the first aspect.
[0064] Preferably, the positive current collector is aluminum foil.
[0065] The present invention does not specifically limit the thickness of the positive electrode sheet. For example, it can be 80μm, 82μm, 84μm, 85μm, 86μm, 88μm or 90μm.
[0066] It should be noted that the specific steps for combining the positive current collector and the positive electrode material of the sulfide all-solid-state battery can be as follows: roll the sulfide all-solid-state battery positive electrode material to a certain thickness, and then roll it together with the carbon-coated aluminum foil.
[0067] Fourthly, the present invention provides a sulfide all-solid-state battery, the sulfide all-solid-state battery comprising the positive electrode sheet of the sulfide all-solid-state battery as described in the third aspect.
[0068] It should be noted that the present invention does not specifically limit the negative electrode in the sulfide all-solid-state battery. For example, it can be a graphite, lithium titanate, lithium metal or lithium metal alloy negative electrode, etc.
[0069] The numerical range described in this invention includes not only the point values listed above, but also any point values within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values included in the range.
[0070] Compared with the prior art, the present invention has the following beneficial effects:
[0071] This invention coats a sulfide solid electrolyte with a layer of metal fluoride. On the one hand, the stable metal fluoride effectively isolates the sulfide from direct contact with air, greatly improving its air stability and alleviating the problem of the sulfide solid electrolyte's sensitivity to air. On the other hand, the metal fluoride coating layer can prevent the sulfide solid electrolyte from directly contacting the cathode material, alleviating the instability between the cathode material and the electrolyte. This provides an effective approach for the industrialization of all-solid-state batteries. Detailed Implementation
[0072] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.
[0073] Example 1
[0074] This embodiment provides a sulfide all-solid-state battery cathode material, which includes a cathode active material and a composite sulfide solid electrolyte.
[0075] The composite sulfide solid electrolyte includes a sulfide solid electrolyte matrix and a metal fluoride layer coated on the surface of the sulfide solid electrolyte matrix.
[0076] The mass ratio of the positive electrode active material to the composite sulfide solid electrolyte is 8:2. The thickness of the metal fluoride layer is 2 nm. The sulfide solid electrolyte matrix is Li6PS5Cl, the metal fluoride layer material is iron fluoride, and the positive electrode active material is LiNi. 0.8 Co 0.1 Mn 0.1 O2.
[0077] This embodiment also provides a method for preparing the above-mentioned sulfide all-solid-state battery cathode material, the preparation method comprising the following steps:
[0078] (1) Place 1g of Fe2O3 in a crucible and place the crucible in the temperature zone of the tube furnace. Heat the crucible to 600℃ at 2℃ / min and purify it with argon gas as a protective gas throughout the heating process. When the temperature reaches 600℃, immediately turn off the argon gas and purge with a hydrogen-argon mixture (volume fraction: 5% H2) for 10 minutes to carry out the reduction reaction. Reduce Fe2O3 to elemental Fe with H2. Stop purging the hydrogen-argon mixture and then purge with argon gas for protection. After the tube furnace cools naturally to room temperature of 25℃, remove the elemental Fe for later use.
[0079] (2) Place elemental Fe in a tube furnace and heat it to 300°C at 2°C / min. Argon gas is introduced as a protective gas throughout the heating process. When the temperature reaches 300°C, the argon gas is immediately turned off, and then nitrogen trifluoride gas is introduced for 15 minutes to carry out the fluorination reaction. The resulting iron fluoride is placed in a glove box for later use.
[0080] (3) Mix 0.05g of iron fluoride and 5g of Li6PS5Cl by ball milling at 400rpm for 30min, and then sinter at 200℃ for 2h to obtain a composite sulfide solid electrolyte. Put it in a glove box for later use and label it as 1%FeF3@Li6PS5Cl.
[0081] Among them, based on the mass of the sulfide solid electrolyte matrix, the mass content of iron fluoride is 1 wt.%;
[0082] (4) Mix 1.372g of composite sulfide solid electrolyte and 5.6g of LiNi 0.8 Co 0.1 Mn 0.1 The material was ball-milled once with O2, and then 0.014g of acetylene black was added for a second ball milling. The material after the second ball milling was removed and placed in an agate grinding pot with 0.014g of polytetrafluoroethylene added for 40 minutes of grinding. After grinding, the sulfide all-solid-state battery cathode material was obtained.
[0083] The ball milling process involved a first milling speed of 420 rpm and a time of 30 min; a second milling speed of 430 rpm and a time of 40 min; and a mass ratio of conductive agent to binder of 1:1.
[0084] Example 2
[0085] This embodiment provides a sulfide all-solid-state battery cathode material, which includes a cathode active material and a composite sulfide solid electrolyte.
[0086] The composite sulfide solid electrolyte includes a sulfide solid electrolyte matrix and a metal fluoride layer coated on the surface of the sulfide solid electrolyte matrix.
[0087] The mass ratio of the positive electrode active material to the composite sulfide solid electrolyte is 8:2. The thickness of the metal fluoride layer is 2 nm. The sulfide solid electrolyte matrix is Li6PS5Cl, the metal fluoride layer material is cobalt fluoride, and the positive electrode active material is LiNi. 0.8 Co 0.1 Mn 0.1 O2.
[0088] This embodiment also provides a method for preparing the above-mentioned sulfide all-solid-state battery cathode material, the preparation method comprising the following steps:
[0089] (1) Place 1g of CoO in a crucible and place the crucible in the temperature zone of the tube furnace. Heat the crucible to 600℃ at 2℃ / min and purify it with argon gas as a protective gas throughout the heating process. When the temperature reaches 600℃, immediately turn off the argon gas and purge the hydrogen-argon mixture (volume fraction: 5% H2) for 10 minutes to carry out the reduction reaction. Reduce CoO to metallic element Co with H2. Stop purging the hydrogen-argon mixture and then purge with argon gas for protection. After the tube furnace cools naturally to room temperature of 25℃, take out the metallic element Co for later use.
[0090] (2) Place the elemental Co in a tube furnace and heat it to 300°C at 2°C / min. Argon gas is introduced as a protective gas throughout the heating process. When the temperature reaches 300°C, the argon gas is immediately turned off, and then nitrogen trifluoride gas is introduced for 15 minutes to carry out the fluorination reaction. The resulting cobalt fluoride is placed in a glove box for later use.
[0091] (3) Mix 0.05g cobalt fluoride and 5g Li6PS5Cl by ball milling at 400rpm for 30min, and then sinter at 200℃ for 2h to obtain composite sulfide solid electrolyte. Put it in a glove box for later use and label it as 1%CoF2@Li6PS5Cl.
[0092] Based on the mass of the sulfide solid electrolyte matrix, the mass content of cobalt fluoride is 1 wt.%.
[0093] (4) Mix 1.372g of composite sulfide solid electrolyte and 5.6g of LiNi 0.8 Co 0.1 Mn 0.1 The material was ball-milled once with O2, and then 0.014g of acetylene black was added for a second ball milling. The material after the second ball milling was removed and placed in an agate grinding pot with 0.014g of polytetrafluoroethylene added for 40 minutes of grinding. After grinding, the sulfide all-solid-state battery cathode material was obtained.
[0094] The ball milling process involved a first milling speed of 420 rpm and a time of 30 min; a second milling speed of 430 rpm and a time of 40 min; and a mass ratio of conductive agent to binder of 1:1.
[0095] Example 3
[0096] This embodiment provides a sulfide all-solid-state battery cathode material, which includes a cathode active material and a composite sulfide solid electrolyte.
[0097] The composite sulfide solid electrolyte includes a sulfide solid electrolyte matrix and a metal fluoride layer coated on the surface of the sulfide solid electrolyte matrix.
[0098] The mass ratio of the positive electrode active material to the composite sulfide solid electrolyte is 8:2, the thickness of the metal fluoride layer is 2 nm, the sulfide solid electrolyte matrix is Li6PS5Cl, the material of the metal fluoride layer is manganese fluoride, and the positive electrode active material is LiNi. 0.8 Co 0.1 Mn 0.1 O2.
[0099] This embodiment also provides a method for preparing the above-mentioned sulfide all-solid-state battery cathode material, the preparation method comprising the following steps:
[0100] (1) Place 1g of MnO2 in a crucible and place the crucible in the temperature zone of the tube furnace. Heat the crucible to 500℃ at 2℃ / min and purify it with argon gas as a protective gas throughout the heating process. When the temperature reaches 500℃, immediately turn off the argon gas and purge with a hydrogen-argon mixture (volume fraction: 5% H2) for 12 minutes to carry out the reduction reaction. Reduce MnO2 to metallic element Mn with H2. Stop purging the hydrogen-argon mixture and then purge with argon gas for protection. After the tube furnace cools naturally to room temperature of 25℃, remove the metallic element Mn for later use.
[0101] (2) Place the metallic element Mn in a tube furnace and heat it to 200°C at 2°C / min. Argon gas is introduced as a protective gas throughout the heating process. When the temperature reaches 200°C, the argon gas is immediately turned off, and then nitrogen trifluoride gas is introduced for 20 minutes to carry out the fluorination reaction. The resulting manganese fluoride is placed in a glove box for later use.
[0102] (3) Mix 0.05g manganese fluoride and 5g Li6PS5Cl by ball milling at 300rpm for 40min, and then sinter at 150℃ for 3h to obtain composite sulfide solid electrolyte. Put it in a glove box for later use and label it as 1%MnF2@Li6PS5Cl.
[0103] Based on the mass of the sulfide solid electrolyte matrix, the mass content of manganese fluoride is 1 wt.%.
[0104] (4) Mix 1.372g of composite sulfide solid electrolyte and 5.6g of LiNi 0.8 Co 0.1 Mn 0.1 The material was ball-milled once with O2, and then 0.014g of acetylene black was added for a second ball milling. The material after the second ball milling was removed and placed in an agate grinding pot with 0.014g of polytetrafluoroethylene added for 40 minutes of grinding. After grinding, the sulfide all-solid-state battery cathode material was obtained.
[0105] The ball milling process involved a first milling speed of 400 rpm and a time of 40 min; a second milling speed of 400 rpm and a time of 50 min; and a mass ratio of conductive agent to binder of 1:1.
[0106] Example 4
[0107] This embodiment provides a sulfide all-solid-state battery cathode material, which includes a cathode active material and a composite sulfide solid electrolyte.
[0108] The composite sulfide solid electrolyte includes a sulfide solid electrolyte matrix and a metal fluoride layer coated on the surface of the sulfide solid electrolyte matrix.
[0109] The mass ratio of the positive electrode active material to the composite sulfide solid electrolyte is 8:2, the thickness of the metal fluoride layer is 2 nm, the sulfide solid electrolyte matrix is Li6PS5Cl, the material of the metal fluoride layer is nickel fluoride, and the positive electrode active material is LiNi. 0.8 Co 0.1 Mn 0.1 O2.
[0110] This embodiment also provides a method for preparing the above-mentioned sulfide all-solid-state battery cathode material, the preparation method comprising the following steps:
[0111] (1) Place 1g of NiO2 in a crucible and place the crucible in the temperature zone of the tube furnace. Heat the crucible to 700℃ at 2℃ / min and purify it with argon gas as a protective gas throughout the heating process. When the temperature reaches 700℃, immediately turn off the argon gas and purge the hydrogen-argon mixture (volume fraction: 5% H2) for 8 minutes to carry out the reduction reaction. Reduce NiO2 to metallic elemental Ni with H2. Stop purging the hydrogen-argon mixture and then purge with argon gas for protection. After the tube furnace cools naturally to room temperature of 25℃, remove the metallic elemental Ni for later use.
[0112] (2) Place metallic elemental Ni in a tube furnace and heat it to 400°C at 2°C / min. Argon gas is introduced as a protective gas throughout the heating process. When the temperature reaches 400°C, the argon gas is immediately turned off, and then nitrogen trifluoride gas is introduced for 10 minutes to carry out the fluorination reaction. The obtained nickel fluoride is placed in a glove box for later use.
[0113] (3) Mix 0.05g of nickel fluoride and 5g of Li6PS5Cl by ball milling at 500rpm for 20min, and then sinter at 250℃ for 1h to obtain a composite sulfide solid electrolyte. Place it in a glove box for later use and label it as 1%NiF2@Li6PS5Cl.
[0114] Based on the mass of the sulfide solid electrolyte matrix, the mass content of nickel fluoride is 1 wt.%.
[0115] (4) Mix 1.372g of composite sulfide solid electrolyte and 5.6g of LiNi 0.8 Co 0.1 Mn 0.1 The material was ball-milled once with O2, and then 0.014g of acetylene black was added for a second ball milling. The material after the second ball milling was removed and placed in an agate grinding pot with 0.014g of polytetrafluoroethylene added for 40 minutes of grinding. After grinding, the sulfide all-solid-state battery cathode material was obtained.
[0116] The ball milling process involved a first milling speed of 500 rpm and a time of 20 min; a second milling speed of 500 rpm and a time of 30 min; and a mass ratio of conductive agent to binder of 1:1.
[0117] Example 5
[0118] The difference between this embodiment and Embodiment 1 is that the positive electrode active material is LiNi. 0.8 Co 0.1 Mn 0.1 The mass ratio of O2 to the complex sulfide solid electrolyte is 5:6.
[0119] The remaining preparation methods and parameters are consistent with those in Example 1.
[0120] Example 6
[0121] The difference between this embodiment and Embodiment 1 is that the positive electrode active material is LiNi. 0.8 Co 0.1 Mn 0.1 The mass ratio of O2 to the complex sulfide solid electrolyte is 9:1.
[0122] The remaining preparation methods and parameters are consistent with those in Example 1.
[0123] Example 7
[0124] The difference between this embodiment and embodiment 1 is that the sintering temperature in step (3) is 100°C.
[0125] The remaining preparation methods and parameters are consistent with those in Example 1.
[0126] Example 8
[0127] The difference between this embodiment and embodiment 1 is that the sintering temperature in step (3) is 300°C.
[0128] The remaining preparation methods and parameters are consistent with those in Example 1.
[0129] Example 9
[0130] The difference between this embodiment and embodiment 1 is that the amount of ferric fluoride added in step (3) is 0.005g.
[0131] The remaining preparation methods and parameters are consistent with those in Example 1.
[0132] Example 10
[0133] The difference between this embodiment and embodiment 1 is that the amount of ferric fluoride added in step (3) is 0.5g.
[0134] The remaining preparation methods and parameters are consistent with those in Example 1.
[0135] Comparative Example 1
[0136] This comparative example provides a method for preparing a sulfide-based all-solid-state battery cathode material, the method comprising:
[0137] 1.372g Li6PS5Cl and 5.6g LiNi 0.8 Co 0.1 Mn 0.1 The material was ball-milled once with O2, and then 0.014g of acetylene black was added for a second ball milling. The material after the second ball milling was removed and placed in an agate grinding pot with 0.014g of polytetrafluoroethylene added for 40 minutes of grinding. After grinding, the sulfide all-solid-state battery cathode material was obtained.
[0138] The ball milling process involved a first milling speed of 420 rpm and a time of 30 min; a second milling speed of 430 rpm and a time of 40 min; and a mass ratio of conductive agent to binder of 1:1.
[0139] Performance testing
[0140] The sulfide all-solid-state battery cathode materials prepared in the above embodiments and comparative examples are used to make cathode sheets and assemble sulfide all-solid-state batteries. The specific steps include:
[0141] (I) The sulfide all-solid-state battery positive electrode material is placed in a roller press and repeatedly rolled (the temperature of the upper roller of the roller press is 90°C and the temperature of the lower roller is 100°C). When the thickness is 85μm, the rolling is stopped. The 85μm positive electrode material is rolled and compounded with carbon-coated aluminum foil to obtain the positive electrode sheet.
[0142] (II) Using the above-prepared positive electrode as the positive electrode, and cutting it into small circular pieces with a diameter of 10 mm using a punching machine, using Li6PS5Cl as the sulfide solid electrolyte, and using a lithium indium metal electrode as the negative electrode, the sulfide solid electrolyte was placed between the positive and negative electrodes. The above-prepared sulfide all-solid-state battery was placed in the Blue Battery Test System, and its electrochemical performance was tested at a rate of 0.1C. The test results are shown in Table 1.
[0143] Table 1
[0144]
[0145] analyze:
[0146] As shown in the table above, by coating a sulfide solid electrolyte with a layer of metal fluoride, this invention can effectively improve the first-cycle discharge specific capacity of sulfide all-solid-state batteries, while also improving their cycle stability. Furthermore, it has been found that the performance improvement effect of metal fluoride is universal.
[0147] A comparison of the data results from Examples 1 and 5-6 shows that if the mass ratio of the positive electrode active material to the composite sulfide solid electrolyte is too small, there will be too much sulfide electrolyte between the positive electrode materials, resulting in a decrease in battery capacity and cycle performance; if the mass ratio of the positive electrode active material to the composite sulfide solid electrolyte is too large, the composite positive electrode will have a slower ion conduction ability, resulting in a decrease in battery capacity and cycle performance.
[0148] Comparison of the data results of Example 1 and Examples 7-8 shows that if the sintering temperature in step (3) is too low, the fluoride electrolyte cannot be tightly coated on the sulfide electrolyte, resulting in a decrease in battery capacity and cycle performance; if the sintering temperature in step (3) is too high, the metal fluoride will diffuse into the crystal structure of the sulfide electrolyte, resulting in an adverse change in its performance.
[0149] A comparison of the data results from Examples 1 and 9-10 shows that if the amount of iron fluoride added is too small, i.e. the metal fluoride layer is too thin, the improvement in electrochemical performance is very weak and has no significant effect. If the amount of iron fluoride added is too large, i.e. the metal fluoride layer is too thick, the first discharge specific capacity of the sulfide all-solid-state battery decreases significantly. This may be because the metal fluoride has a weak conductivity for conducting electrons, and the excessively thick coating layer leads to weak lithium-ion transport in the all-solid-state battery, which further results in the inability to fully release the capacity.
[0150] A comparison of the data results from Example 1 and Comparative Example 1 shows that if the sulfide solid electrolyte is not coated with metal fluoride, the sulfide will be in direct contact with the air, resulting in poor air stability. Furthermore, it is impossible to avoid direct contact between the sulfide solid electrolyte and the positive electrode material, which leads to a decrease in battery capacity and cycle performance.
[0151] The applicant declares that the technical solution of this invention is illustrated by the above embodiments, but this invention is not limited to the above embodiments, that is, it does not mean that this invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the products of this invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.
Claims
1. A sulfide-based all-solid-state battery cathode material, characterized in that, The sulfide all-solid-state battery cathode material includes a cathode active material and a composite sulfide solid electrolyte. The composite sulfide solid electrolyte includes a sulfide solid electrolyte matrix and a metal fluoride layer coated on the surface of the sulfide solid electrolyte matrix. The mass ratio of the positive electrode active material to the composite sulfide solid electrolyte is (5-8):(5-2); the thickness of the metal fluoride layer is 2-5 nm. The sulfide solid electrolyte matrix includes Li7P3S. 11 , β-Li3PS4, Li6PS5Cl, Li6PS5Br, Li7P2S8I, Li4PS4I, Li6PS5Cl x Br 1-x Li6PS5Cl y I 1-y or Li6PS5Br z I 1-z Any combination of one or at least two of them, where 0 < x < 1, 0 ≤ y < 1, 0 < z < 1; The material of the metal fluoride layer includes any one or a combination of at least two of ferrous fluoride, cobalt fluoride, manganese fluoride, or nickel fluoride. The preparation method of the sulfide all-solid-state battery cathode material includes the following steps: (1) Mix metal fluoride and sulfide solid electrolyte matrix and sinter to obtain composite sulfide solid electrolyte; (2) The composite sulfide solid electrolyte and the positive electrode active material are mixed to obtain the sulfide all-solid-state battery positive electrode material; The mixing method in step (1) includes ball milling; the ball milling speed is 300-500 rpm and the time is 20-40 min; The sintering temperature in step (1) is 150-250℃; the sintering time in step (1) is 1-3h; Based on the mass of the sulfide solid electrolyte matrix, the mass content of the metal fluoride in step (1) is 1 wt.%; The preparation steps of the metal fluoride in step (1) include: (a) Mixing a metal oxide with a reducing gas to carry out a reduction reaction yields a metallic element; (b) The metal element and the fluorine-containing gas are mixed and subjected to a fluorination reaction to obtain a metal fluoride; The reducing gas in step (a) includes hydrogen; The fluorine-containing gas in step (b) includes any one or a combination of at least two of nitrogen trifluoride, hexafluoroethane, octafluoropropane, octafluorocyclobutane, or hexafluorobutadiene.
2. A method for preparing the sulfide all-solid-state battery cathode material as described in claim 1, characterized in that, The preparation method includes the following steps: (1) Mix metal fluoride and sulfide solid electrolyte matrix and sinter to obtain composite sulfide solid electrolyte; (2) The composite sulfide solid electrolyte and the positive electrode active material are mixed to obtain the sulfide all-solid-state battery positive electrode material.
3. The preparation method according to claim 2, characterized in that, The preparation steps of the metal fluoride in step (1) include: (a) Mixing a metal oxide with a reducing gas to carry out a reduction reaction yields a metallic element; (b) The metal element and the fluorine-containing gas are mixed and subjected to a fluorination reaction to obtain a metal fluoride.
4. The preparation method according to claim 3, characterized in that, The metal oxide in step (a) includes any one or a combination of at least two of Fe2O3, CoO, MnO2 or NiO2.
5. The preparation method according to claim 3, characterized in that, The reduction reaction in step (a) is carried out in a protective atmosphere.
6. The preparation method according to claim 3, characterized in that, The temperature of the reduction reaction in step (a) is 500-700℃; The reduction reaction in step (a) takes 8-12 minutes.
7. The preparation method according to claim 3, characterized in that, The fluorination reaction in step (b) is carried out at a temperature of 200-400°C. The fluorination reaction in step (b) takes 10-20 minutes.
8. The preparation method according to claim 2, characterized in that, In step (2), conductive agents and binders are also added during the mixing process.
9. The preparation method according to claim 8, characterized in that, The specific steps of mixing described in step (2) include: The composite sulfide solid electrolyte and the positive electrode active material are ball-milled once, then a conductive agent is added for a second ball milling, and finally a binder is added for grinding.
10. The preparation method according to claim 8, characterized in that, The preparation method includes the following steps: (I) Mix metal oxides and reducing gases and carry out a reduction reaction in a protective atmosphere to obtain elemental metals; The reduction reaction temperature is 500-700℃, and the reduction reaction time is 8-12 min; (II) The metal element and fluorine-containing gas are mixed and subjected to a fluorination reaction to obtain a metal fluoride; The fluorination reaction is carried out at a temperature of 200-400℃ for 10-20 minutes. (III) Mix the metal fluoride and sulfide solid electrolyte matrix by ball milling at 300-500 rpm for 20-40 min, and then sinter at 150-250℃ for 1-3 h to obtain the composite sulfide solid electrolyte. The metal fluoride content is 1 wt.%, based on the mass of the sulfide solid electrolyte matrix. (IV) The composite sulfide solid electrolyte and positive electrode active material are ball-milled once, then a conductive agent is added for a second ball milling, and then a binder is added for grinding. After grinding, the sulfide all-solid-state battery positive electrode material is obtained. The first ball milling process involves a rotation speed of 400-500 rpm and a time of 20-40 minutes; the second ball milling process involves a rotation speed of 400-500 rpm and a time of 30-50 minutes.
11. A sulfide-based all-solid-state battery positive electrode, characterized in that, The positive electrode of the sulfide all-solid-state battery is obtained by combining the positive electrode current collector and the positive electrode material of the sulfide all-solid-state battery according to claim 1.
12. A sulfide all-solid-state battery, characterized in that, The sulfide all-solid-state battery includes the positive electrode sheet of the sulfide all-solid-state battery as described in claim 11.