Positive electrode material coated with lithium-rich disordered rock salt layer, preparation method of positive electrode material and solid-state lithium battery

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a positive electrode material coated with a lithium-rich disordered rock salt layer, a preparation method of the positive electrode material and a solid-state lithium battery. The surface of the ternary positive electrode material is coated with the lithium-rich disordered rock salt material as a coating layer, and the lithium-rich disordered rock salt layer is unique and disordered, so that the ternary positive electrode material is more stable in structure and more resistant to high voltage; moreover, the lithium-rich disordered rock salt layer contains transition metal ions with a d0 structure, and the uniform and compact coating layer prepared by combining an ALD technology can effectively inhibit side reaction between the positive electrode material and the solid electrolyte and reduce interface impedance; in addition, the lithium-rich disordered rock salt layer can form 0-TM pore channels which are coordinated with the lithium-rich high Li < + > seepage network, so that the ion transport kinetics is optimized; moreover, the amorphous / nanocrystalline lithium-rich disordered rock salt phase layer can be plastically deformed, absorb stress, maintain interface contact, buffer volume strain and improve cycle stability, and the capacity, rate capability and cycle stability of the solid-state lithium ion battery are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and in particular relates to a positive electrode material coated with a lithium-rich disordered rock salt layer, a preparation method thereof, and a solid-state lithium battery. Background Art

[0002] Compared with traditional liquid lithium batteries, solid-state batteries are considered to be the optimal system for building the next generation of rechargeable batteries with higher energy density and higher safety. The high specific capacity of high-nickel positive electrode materials (Ni content ≥ 80%) can better meet the high energy density requirements of solid-state batteries and has been widely studied. However, the solid-solid contact between the solid electrolyte and the positive electrode material is poor, the ion diffusion rate is low, and interfacial side reactions are more likely to occur, resulting in increased interfacial impedance; high-nickel positive electrodes are more prone to volume expansion, and solid electrolytes are difficult to deform due to solid-solid contact, and cannot be compatible with the volume strain of the positive electrode particles. The interfacial contact sites will detach and fail due to the repeated expansion / contraction of the active particles, seriously affecting the performance of the solid-state battery.

[0003] The current solution to the above problem is mainly to coat the surface of the positive electrode material, such as coating the surface of the positive electrode material with oxides such as Al2O3, SiO2, ZrO2, and TiO2, to achieve physical isolation between the positive electrode material and the solid electrolyte and inhibit interfacial side reactions. However, the electron / ion conductivity of oxides is low. Ionic conductors such as Li3PO3, LiAlSiO4, LiPON, LATP, and LLZO can also be coated on the surface of the positive electrode material. On the basis of achieving physical isolation, they can provide additional lithium ion transmission channels and help reduce interfacial impedance. For example, the Chinese patent with publication number CN112421010A uses a solid phase method to coat the surface of the positive electrode material with an electron / ion dual-conducting material (LiMn2O4, LiFePO4, Li2TiO3, aluminum-tungsten fluoride or LiNiO3), introduces an electron-ion dual conductor, improves the channel for lithium ion diffusion, and enhances the electrochemical performance; for example, the Chinese patent with publication number CN113437273B uses a sol-gel + heat treatment method to coat a 5-10 nm layer of Li on the surface of the positive electrode material. 1.175 Nb 0.645 Ti 0.4 O3 inhibits the interfacial side reactions between the oxide positive electrode and the sulfide all-solid-state electrolyte, thereby improving the cycle life of the all-solid-state lithium-ion battery.

[0004] However, the traditional coating materials and coating methods still have the following problems:

[0005] 1. Poor quality of coating layer: The thickness of the coating layer is uneven and difficult to control. Too thick will hinder the transmission of lithium ions, while too thin will not provide effective protection. The density is insufficient, the interface stability is poor, and the side reactions cannot be completely isolated.

[0006] 2. The coating layer formed by traditional coating methods (sol-gel, solid-phase method, ball milling, etc.) has weak adhesion and insufficient mechanical stability. The volume change of the positive electrode during charging and discharging may cause the coating layer to rupture and lose its protective effect.

[0007] 3. High-nickel materials are very prone to phase change and volume expansion under high voltage. The existing traditional coating layers (such as Al2O3, LiNbO3, Li2ZrO3, etc.) are still unable to completely inhibit / block interfacial side reactions, hindering the application of high-nickel positive electrodes in solid-state batteries.

[0008] The above problems will lead to poor electrochemical performance of solid-state batteries. Finding new coating materials and coating methods that are more compatible with solid-state electrolytes and high-nickel positive electrode materials is an effective way to apply high-nickel positive electrode materials to solid-state batteries. Summary of the Invention

[0009] In view of this, the technical problem to be solved by the present invention is to provide a positive electrode material coated with a lithium-rich disordered rock salt layer, a preparation method thereof and a solid-state lithium battery. The positive electrode material coated with a lithium-rich disordered rock salt layer can solve the problems of low ion transfer efficiency, many interfacial side reactions, high impedance, and poor (electro)chemical stability caused by solid-solid contact between the positive electrode material and the electrolyte in solid-state lithium-ion batteries, thereby improving the rate performance, cycle stability and energy density of solid-state lithium-ion batteries.

[0010] The present invention provides a positive electrode material coated with a lithium-rich disordered rock salt layer, comprising a core and a coating layer wrapped around the core;

[0011] The core is a ternary positive electrode material;

[0012] The coating layer is a lithium-rich disordered rock salt material; the chemical formula of the lithium-rich disordered rock salt material is Li 1+x M y M' z O 2-n F n ; wherein, x>0, y>0, z≥0, 0≤n<2; M is a transition metal element having redox activity; M' is a transition metal element and / or a d0 transition metal element that is redox inert.

[0013] Preferably, the chemical formula of the ternary cathode material is LiNi a Co b Mn c O2; wherein, 0.10≤a<1, 0<b<1, 0<c<1, a+b+c=1;

[0014] And / or, the M is selected from one or more of Mn, Ni, V, Cr and Fe;

[0015] And / or, the M' is selected from one or more of Ti, Zr, Nb, Mo, Ta and W;

[0016] and / or, the coating layer has a thickness of 1 to 20 nm;

[0017] and / or, 0.1≤x≤0.5; and / or, 0.1≤y≤0.5; and / or, 0≤z≤0.5; and / or, 0≤n≤0.1; and / or, 0.8≤a<1.

[0018] Preferably, the coating layer is formed by an atomic layer deposition layer or multiple atomic layer deposition layers after annealing;

[0019] The multi-layer atomic layer deposition layer includes at least one lithium oxide atomic layer deposition layer and at least one first transition metal oxide atomic layer deposition layer; the first transition metal oxide atomic layer deposition layer includes M oxide;

[0020] The lithium oxide atomic layer deposition layer is in contact with the core.

[0021] Preferably, the multi-layer atomic layer deposition layer includes a multi-layer lithium oxide atomic layer deposition layer and a multi-layer first transition metal oxide atomic layer deposition layer, and the lithium oxide atomic layer deposition layer and the first transition metal oxide atomic layer deposition layer are alternately arranged;

[0022] And / or, the temperature of the annealing treatment is 100° C. to 500° C.; and the time of the annealing treatment is greater than 0 h.

[0023] Preferably, the first transition metal oxide atomic layer further comprises M' oxide;

[0024] And / or, the multi-layer atomic layer deposition layer further comprises at least one second transition metal oxide atomic layer deposition layer; the second transition metal oxide atomic layer comprises M' oxide;

[0025] And / or, the multi-layer atomic layer deposition layer further includes at least one transition metal oxyfluoride atomic layer deposition layer; the transition metal oxyfluoride atomic layer deposition layer includes M and / or M'.

[0026] Preferably, the multi-layer atomic layer deposition layer includes a multi-layer second transition metal oxide atomic layer deposition layer; the multi-layer second transition metal oxide atomic layer deposition layer is separated by a lithium oxide atomic layer deposition layer; the first transition metal oxide atomic layer deposition layer and the second transition metal oxide atomic layer deposition layer are separated by a lithium oxide atomic layer deposition layer.

[0027] The present invention also provides a method for preparing the above-mentioned positive electrode material coated with the lithium-rich disordered rock salt layer, comprising the following steps:

[0028] An atomic layer deposition layer or multiple atomic layer deposition layers are prepared on the surface of the ternary positive electrode material, and annealing treatment is performed to obtain a positive electrode material coated with a lithium-rich disordered rock salt layer; the multiple atomic layer deposition layers include at least one lithium oxide atomic layer deposition layer and at least one first transition metal oxide atomic layer deposition layer; the first transition metal oxide atomic layer deposition layer includes M oxide; and the lithium oxide atomic layer deposition layer is in contact with the core.

[0029] The present invention also provides a positive electrode, comprising the positive electrode material coated with the lithium-rich disordered rock salt layer.

[0030] Preferably, the positive electrode comprises a positive electrode current collector and a positive electrode active layer provided on at least one surface of the positive electrode current collector; the positive electrode active layer comprises the positive electrode material coated with the lithium-rich disordered rock salt layer, a conductive agent, a solid electrolyte and a binder;

[0031] The mass content of the positive electrode material coated with the lithium-rich disordered rock salt layer in the positive electrode active layer is greater than or equal to 70%;

[0032] And / or, the conductive agent is selected from one or more of vapor-grown carbon fiber, Super-P, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, Ketjen black and acetylene black;

[0033] and / or, the solid electrolyte is selected from sulfide solid electrolytes;

[0034] And / or, the binder is selected from one or more of polyvinyl alcohol, hydrogenated nitrile rubber, styrene-butadiene rubber, polytetrafluoroethylene and polyvinylidene fluoride.

[0035] The present invention also provides a solid-state lithium battery comprising the above-mentioned positive electrode.

[0036] The present invention provides a positive electrode material coated with a lithium-rich disordered rock salt layer, comprising a core and a coating layer wrapped around the core; the core is a ternary positive electrode material; the coating layer is a lithium-rich disordered rock salt material; the chemical formula of the lithium-rich disordered rock salt material is Li 1+x M y M' z O 2-n F n ; wherein, x>0, y>0, z≥0, 0≤n<2; M is a transition metal element with redox activity; M' is a transition metal element and / or d0 transition metal element with redox inertness. Compared with the prior art, the present invention coats the surface of the ternary cathode material with a lithium-rich disordered rock salt material as a coating layer. The unique disorder of the lithium-rich disordered rock salt layer makes its structure more stable and more resistant to high pressure; and the lithium-rich disordered rock salt layer contains d 0The transition metal ions of the structure and the uniform and dense coating layer prepared by ALD technology can effectively inhibit the side reaction between the positive electrode material and the solid electrolyte and reduce the interface impedance; in addition, the lithium-rich disordered rock salt layer can form 0-TM channels and lithium-rich high Li + The coordination of the percolation network, combined with the nano-scale ultra-thin coating layer, optimizes the ion transport kinetics; furthermore, the amorphous / nanocrystalline lithium-rich disordered rock salt phase layer can plastically deform, absorb stress, maintain interfacial contact, buffer volume strain, and improve cycle stability, effectively improving the capacity, rate performance and cycle stability of solid-state lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a charge and discharge curve diagram of the sulfide solid-state lithium-ion battery obtained in Example 1 of the present invention in the first cycle;

[0038] Figure 2 This is a cycle retention curve of the sulfide solid-state lithium-ion battery obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] The present invention provides a positive electrode material coated with a lithium-rich disordered rock salt layer, comprising a core and a coating layer wrapped around the core; the core is a ternary positive electrode material; the coating layer is a lithium-rich disordered rock salt material; the chemical formula of the lithium-rich disordered rock salt material is Li 1+x M y M' z O 2-n F n ; wherein, x>0, y>0, z≥0, 0≤n<2; M is a transition metal element having redox activity; M' is a transition metal element and / or a d0 transition metal element that is redox inert.

[0041] The positive electrode material provided by the present invention has a ternary positive electrode material as the core; the ternary positive electrode material can be a ternary positive electrode material well known to those skilled in the art, and there is no special limitation. In a specific embodiment provided by the present invention, the chemical formula of the ternary positive electrode material is LiNi a Co b Mn cO2; wherein, 0.10≤a<1, 0<b<1, 0<c<1, a+b+c=1; optionally, a is 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 0.99 or a range between any two of the above values. Depending on a, the ternary positive electrode material can be divided into medium-low nickel positive electrode material and high-nickel positive electrode material; when a≤0.6, the ternary positive electrode material is a medium-low nickel positive electrode material with better stability but slightly lower energy density; when a>0.6, the ternary positive electrode material is a high-nickel positive electrode material with higher capacity. The ternary positive electrode material may also include doping elements, which may be, for example, but not limited to, one or more of Al, Ti, Zr, Mg, Sr, Nb, Mo, Ta and W.

[0042] In a specific embodiment provided by the present invention, 0.80≤a<1.

[0043] In a specific embodiment provided by the present invention, 0.80≤a<0.95.

[0044] Cobalt is mainly responsible for improving the stability of the battery and extending its service life in the positive electrode material. It can reduce the occupancy of the cationic mixture, stabilize the layered structure of the material, reduce the impedance value, and improve the conductivity, thereby improving the cycle and rate performance of the battery. However, too high a cobalt content will also lead to a decrease in the actual capacity, so its ratio also needs to be precisely controlled. In a specific embodiment provided by the present invention, 0<b≤0.40; optionally, b is 0.01, 0.04, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40 or a range between any two of the above values.

[0045] In a specific embodiment provided by the present invention, 0.01≤b≤0.40.

[0046] In a specific embodiment provided by the present invention, 0.04≤b≤0.40.

[0047] Manganese optimizes the interfacial stability of the positive electrode material during cycling. In a specific embodiment provided by the present invention, 0<c≤0.50; optionally, c is 0.01, 0.04, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.50, or a range between any two of the above values.

[0048] In a specific embodiment provided by the present invention, 0.01≤c≤0.50.

[0049] In a specific embodiment provided by the present invention, 0.01≤c≤0.30.

[0050] The ternary positive electrode material can be divided into polycrystalline material and single crystal material according to the microscopic morphology of the particles. The present invention has no special restrictions on it. It can be a single crystal ternary positive electrode material, a polycrystalline ternary positive electrode material, or a mixture of the two. Among them, the polycrystalline ternary positive electrode material has a higher gram capacity and can provide a higher energy density, thereby extending the service life and endurance of the battery; the single crystal ternary positive electrode material has a more complete crystal structure, and its strength and stability are higher, and its ability to withstand high temperature and high voltage is stronger. Although the gram capacity of the single crystal ternary material is lower than that of the polycrystalline material, it can release more capacity under high voltage, thereby improving the energy density.

[0051] D50 refers to the particle size corresponding to when the cumulative particle size distribution percentage of the sample reaches 50%. A smaller D50 value means a smaller particle size, which helps shorten the diffusion path of lithium ions and increase the migration rate of lithium ions, thereby improving the charge and discharge rate and cycle stability of the battery. However, too small a particle size may also lead to an increase in the specific surface area, increasing the probability of side reactions, thereby affecting the cycle life and safety of the battery. According to the present invention, the D50 of the ternary positive electrode material is preferably 1.8 to 9 μm; optionally, the D50 of the ternary positive electrode material is 1.8 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or a range between any two of the above values.

[0052] According to the present invention, the surface of the core is coated with a coating layer. The present invention uses a lithium-rich disordered rock salt material as the coating layer. The disordered rock salt phase is a material with a rock salt structure but with disordered cations. It is composed of anions arranged in a face-centered cubic pattern and cations (such as Li) filling the octahedral gaps. + , transition metal ions), forming an alternating cubic close packing. It has the characteristics of long-range disorder and short-range order.

[0053] In the present invention, the chemical formula of the lithium-rich disordered rock salt material is Li 1+x M y M' z O 2-n F n ; wherein x>0, y>0, z≥0, n≥0; M is a transition metal element (TM) having redox activity; M' is a transition metal element and / or a d0 transition metal element that is redox inert. d 0 The structure refers to the electronic configuration of transition metal ions with no d electrons in their valence shell (i.e., the number of d electrons is 0). These ions are typically in their highest oxidation state and cannot lose further electrons. Therefore, they rarely participate in redox reactions in electrochemical reactions and generally serve to stabilize the structure.

[0054] In lithium-rich disordered rock salt materials, the excess degree of lithium (x) plays a role mainly by affecting the electrochemical properties and structural stability of the material. The introduction of moderately excessive lithium can enhance the Li+ transport kinetics through the 0-TM channel diffusion mechanism (0-TM channel refers to a special type of lithium ion transport channel, which is not blocked by transition metal (TM) ions around the channel and is composed only of a local coordination environment composed of lithium and oxygen. This structure can significantly reduce the energy barrier for lithium ion migration and improve the ionic conductivity of the material). At the same time, it introduces some lithium defects and optimizes the crystal structure of the material, making it more conducive to Li+ transport. + diffusion, thereby improving the discharge capacity and rate performance of the material. However, the excessive introduction of lithium elements will increase the average valence state of the initial transition metal, which may lead to the redox reaction of oxygen anions (O-redox). Although this provides an additional source of reversible capacity, it also increases the risk of oxygen migration, which may lead to structural damage and a decrease in capacity retention. Therefore, in a specific embodiment provided by the present invention, preferably 0.1≤x≤0.5; optionally, x is 0.1, 0.2, 0.3, 0.4, 0.5 or a range between any two of the above values.

[0055] In a specific embodiment provided by the present invention, x≥0.3; at this time, the coating layer is a lithium-rich disordered rock salt phase, and the lithium-rich structure provides Li + Seepage channels improve ionic conductivity; further preferably, 0.3≤x≤0.5; further preferably, 0.3≤x≤0.4; further preferably, 0.3≤x≤0.35.

[0056] In a specific embodiment provided by the present invention, the M is preferably one or more of Mn, Ni, V, Cr and Fe; 3+ / Mn 4+ / Mn 5+ , Ni 2+ / Ni 4+ , V 3+ / V 4+ / V 5+ , Cr 3+ / Cr 6+ with Fe 2+ / Fe 3+ One or more of the redox pairs can provide charge compensation, providing capacity.

[0057] In a specific embodiment provided by the present invention, 0.1≤y≤0.5; optionally, y is 0.1, 0.2, 0.3, 0.4, 0.5 or a range between any two of the above values.

[0058] In a specific embodiment provided by the present invention, 0.3≤y≤0.4.

[0059] In a specific embodiment provided by the present invention, M' is preferably one or more of Ti, Zr, Nb, Mo, Ta and W; the form of M' in the lithium-rich disordered rock salt material is mainly Ti 4+ 、Zr 4+ 、Nb 5+ 、Mo 6+ 、Ta 5+ 、W 6+ etc. They do not participate in redox reactions, and their main function is to reduce the distortion energy of the octahedral structure and stabilize the structure.

[0060] In a specific embodiment provided by the present invention, M' is a single transition metal element or multiple different transition metal elements; when M' is multiple different transition metal elements, the molar numbers of the different transition metal elements are preferably the same.

[0061] In a specific embodiment provided by the present invention, 0≤z≤0.5; optionally, z is 0, 0.1, 0.2, 0.3, 0.4, 0.5 or a range between any two of the above values.

[0062] In a specific embodiment provided by the present invention, 0≤z≤0.4; specifically, z may be 0, 0.25 or 0.4.

[0063] In a specific embodiment provided by the present invention, 0≤n≤0.1; by partially replacing the oxygen element with the fluorine element, oxygen vacancies can be formed to promote Li+ diffusion; optionally, n is 1, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 or a range between any two of the above values.

[0064] In a specific embodiment provided by the present invention, 0≤n≤0.08.

[0065] The structural characteristics of the lithium-rich disordered rock salt phase give it the following features: 1) High structural stability: Structural disorder avoids stress concentration and anisotropic deformation, and random ion distribution makes the local chemical environment more uniform, reducing the anisotropic stress during lithium ion insertion and extraction, thereby inhibiting phase transition and alleviating volume change. Under high pressure (>4.5V vs Li / Li + ) can still maintain structural stability; 2) low electronic conductivity: the unique d 0 The structure makes its electronic conductivity low, which can effectively inhibit the side reaction between the positive electrode material and the solid electrolyte and reduce the interface impedance; 3. Diversified ion transport channels: disorder leads to the diversification of lithium ion migration channels, and the 0-TM channel forms a low energy barrier Li + Transmission high-speed channel, lithium-rich structure to build Li +The percolation network accelerates ion transport, making the material ion diffusion coefficient reach 10 -15 ~10 -10 cm 2 S -1 , which is superior to traditional coating materials (Al2O3<10 -16 cm 2 S -1 ,LiNbO3:10 -15 ~10 -14 cm 2 S -1 ).

[0066] In a specific embodiment provided by the present invention, the thickness of the coating layer is preferably 1 to 20 nm; optionally, the thickness of the coating layer is 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm or a range between any two of the above values.

[0067] In a specific embodiment provided by the present invention, the coating layer is formed by an annealing treatment of a layer of atomic layer deposition or multiple layers of atomic layer deposition; the multiple layers of atomic layer deposition include at least one lithium oxide atomic layer deposition layer and at least one first transition metal oxide atomic layer deposition layer; the first transition metal oxide atomic layer deposition layer includes M oxide; and the lithium oxide atomic layer deposition layer is in contact with the core. The preparation of the lithium-rich disordered rock salt phase requires not only a complete and uniform mixing of elements, but also atomic-level dispersion as much as possible. The lithium-rich disordered rock salt material coating provided by the present invention is formed by an annealing treatment of multiple layers of atomic layer deposition (ALD). The ALD preparation method not only achieves atomic-level mixing / reaction of the lithium-rich disordered rock salt layer, but also the prepared coating layer is nano-scale, uniform, and dense, giving full play to the advantages of the lithium-rich disordered rock salt phase. The unique disorder of the lithium-rich disordered rock salt layer makes its structure more stable and more resistant to high pressure; the d 0 The uniform and dense coating layer prepared by ALD technology effectively inhibits the side reaction between the positive electrode material and the solid electrolyte and reduces the interface impedance; the 0-TM pores of the lithium-rich disordered rock salt and the lithium-rich high Li + The coordination of the percolation network, combined with the nano-scale ultra-thin coating layer, optimizes the ion transport kinetics; the amorphous / nanocrystalline lithium-rich disordered rock salt phase layer can plastically deform, absorb stress, maintain interfacial contact, buffer volume strain, and improve cycle stability, effectively improving the capacity, rate performance and cycle stability of solid-state lithium-ion batteries.

[0068] In a specific embodiment provided by the present invention, the multilayer atomic layer deposition layer includes a multilayer lithium oxide atomic layer deposition layer and a multilayer first transition metal oxide atomic layer deposition layer, and the lithium oxide atomic layer deposition layer and the first transition metal oxide atomic layer deposition layer are alternately arranged.

[0069] Among them, the number of lithium oxide atomic layer deposition layers and the number of multi-layer first transition metal oxide atomic layer deposition layers in the multi-layer atomic layer deposition layers can be selected according to the thickness of the required coating layer; in a specific embodiment provided by the present invention, the number of lithium oxide atomic layer deposition layers in the multi-layer atomic layer deposition layers is preferably 2 to 10 layers; optionally, the number of lithium oxide atomic layer deposition layers in the multi-layer atomic layer deposition layers is 2 layers, 3 layers, 4 layers, 5 layers, 6 layers, 7 layers, 8 layers, 9 layers, 10 layers or a range between any two of the above values; the number of multi-layer first transition metal oxide atomic layer deposition layers is preferably 2 to 10 layers; optionally, the number of multi-layer first transition metal oxide atomic layer deposition layers is 2 layers, 3 layers, 4 layers, 5 layers, 6 layers, 7 layers, 8 layers, 9 layers, 10 layers or a range between any two of the above values.

[0070] In a specific embodiment provided by the present invention, the first transition metal oxide atomic layer also includes an M' oxide; in this case, an amorphous / nanocrystalline oxide containing M and M' can be formed through co-deposition of M and M'. During a subsequent annealing process, Li+ migrates from Li2O to the amorphous / nanocrystalline oxide of M and M', occupying octahedral interstitial sites. Simultaneously, the cations in the amorphous / nanocrystalline oxide are disordered, and Mn / Nb atoms randomly occupy transition metal sites, disrupting the long-range order and forming a disordered rock salt phase.

[0071] In a specific embodiment provided by the present invention, the multi-layer atomic layer deposition layer further includes at least one second transition metal oxide atomic layer deposition layer; the second transition metal oxide atomic layer includes M' oxide.

[0072] In a specific embodiment provided by the present invention, the multi-layer atomic layer deposition layer further includes a second transition metal oxide atomic layer deposition layer; in this case, the second transition metal oxide atomic layer deposition layer is preferably located between the two lithium oxide atomic layer deposition layers.

[0073] In a specific embodiment provided by the present invention, the multi-layer atomic layer deposition also includes a multi-layer second transition metal oxide atomic layer deposition layer; the multi-layer second transition metal oxide atomic layer deposition layer is separated by a lithium oxide atomic layer deposition layer; the first transition metal oxide atomic layer deposition layer and the second transition metal oxide atomic layer deposition layer are separated by a lithium oxide atomic layer deposition layer; that is, the first transition metal oxide atomic layer deposition layer and the second transition metal oxide atomic layer deposition layer are not in contact.

[0074] In a specific embodiment provided by the present invention, the multilayer ALD layers include multilayer lithium oxide ALD layers, multilayer first transition metal oxide ALD layers, and multilayer second transition metal oxide ALD layers; the multilayer lithium oxide ALD layers are first arranged alternately with the multilayer first transition metal oxide ALD layers, and then the multilayer lithium oxide ALD layers are arranged alternately with the multilayer second transition metal oxide ALD layers; that is, the arrangement is lithium oxide ALD layer, first transition metal oxide ALD layer, lithium oxide ALD layer, first transition metal oxide ALD layer... lithium oxide ALD layer, second transition metal oxide ALD layer, lithium oxide ALD layer, second transition metal oxide ALD layer... lithium oxide ALD layer, second transition metal oxide ALD layer. By depositing Li-MO and Li-M'-O intermediate phases in a stepwise manner, the atomic migration path is shortened, the energy barrier for cation migration is reduced, and the interdiffusion effect during annealing is utilized to promote cation (M / M') disordering, thereby more efficiently forming a stable disordered rock salt (lithium-rich disordered rock salt phase).

[0075] The number of layers of the multi-layer second transition metal oxide atomic layer deposition layer can be selected according to the content of M' in the coating layer; in a specific embodiment provided by the present invention, the number of layers of the multi-layer second transition metal oxide atomic layer deposition layer is preferably 2 to 10 layers; optionally, the number of layers of the multi-layer second transition metal oxide atomic layer deposition layer is 2 layers, 3 layers, 4 layers, 5 layers, 6 layers, 7 layers, 8 layers, 9 layers, 10 layers or a range between any two of the above values.

[0076] In a specific embodiment provided by the present invention, the multi-layer atomic layer deposition layer further includes at least one transition metal oxyfluoride atomic layer deposition layer; the transition metal oxyfluoride atomic layer deposition layer includes M and / or M'.

[0077] In a specific embodiment provided by the present invention, the transition metal fluoride oxide atomic layer deposition layer can be located between the lithium oxide atomic layer deposition layer and the first transition metal oxide atomic layer deposition layer; it can also be located between the lithium oxide atomic layer deposition layer and the second transition metal oxide atomic layer deposition layer; it can also be located in the outermost layer of the multi-layer atomic layer deposition layer, that is, the outer layer away from the inner core.

[0078] In a specific embodiment provided by the present invention, when the transition metal oxyfluoride atomic layer deposition layer is located at the outermost layer of multiple atomic layer deposition layers, it is in contact with the first transition metal oxide atomic layer deposition layer or the second transition metal oxide atomic layer deposition layer.

[0079] In a specific embodiment provided by the present invention, the temperature of the annealing treatment is preferably 100°C to 500°C; optionally, the temperature of the annealing treatment is 100°C, 200°C, 300°C, 400°C, 500°C or a range between any two of the above values; the time of the annealing treatment is preferably greater than 0h, more preferably greater than 0h and less than or equal to 24h; optionally, the time of the annealing treatment is 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h or a range between any two of the above values.

[0080] In a specific embodiment provided by the present invention, the temperature of the annealing treatment is preferably 200° C. to 500° C.; and the time of the annealing treatment is preferably 1 to 12 hours.

[0081] The present invention also provides a method for preparing the above-mentioned positive electrode material coated with the lithium-rich disordered rock salt layer, comprising the following steps: preparing a layer of atomic layer deposition layer or multiple layers of atomic layer deposition layers on the surface of the ternary positive electrode material, annealing, and obtaining the positive electrode material coated with the lithium-rich disordered rock salt layer; the multiple layers of atomic layer deposition layers include at least one layer of lithium oxide atomic layer deposition layer and at least one layer of first transition metal oxide atomic layer deposition layer; the first transition metal oxide atomic layer deposition layer includes M oxide; and the lithium oxide atomic layer deposition layer is in contact with the core.

[0082] The present invention has no particular limitation on the sources of all raw materials, and any commercially available raw materials may be used.

[0083] Atomic layer deposition (ALD) is a thin film manufacturing technology based on saturated self-limitation, which can accurately control the coating thickness of the thin film and has the advantages of uniformity, conformality, and density. Compared with the traditional chemical vapor deposition method, the two precursors in the atomic layer deposition method can react with the substrate surface in alternating pulses. Due to the self-limiting saturated adsorption of the precursor molecules, the precursor molecules can only be adsorbed on the substrate surface in a single layer, so the number of cycles of the ALD reaction can be controlled to achieve layer-by-layer deposition of the thin film. The present invention prepares a positive electrode material coated with a lithium-rich disordered rock salt layer through the ALD process. Through atomic layer deposition, the uniform mixing of various elements at the atomic level is promoted, and the coating thickness itself is controlled within 20nm, is uniform and dense, and is composed of elements such as M' / F with low energy barriers. The interatomic diffusion path is short, the required energy is lower, and low-temperature annealing can form a lithium-rich disordered rock salt phase.

[0084] In addition, batch coating of ternary positive electrode materials can be achieved through atomic layer deposition technology; the mass of the ternary positive electrode material is preferably 100-3000g; the mass of the ternary positive electrode material can be optionally 100g, 200g, 300g, 400g, 500g, 600g, 700g, 800g, 900g, 1000g, 1500g, 2000g, 2500g, 3000g or a range between any two of the above values.

[0085] In the present invention, the ternary cathode material is preferably first vacuum dried and cleaned with an inert gas, and then an atomic layer deposition layer or multiple atomic layer deposition layers are prepared on the surface; the vacuum drying temperature is preferably 100°C to 150°C; optionally, the vacuum drying temperature is 100°C, 110°C, 120°C, 130°C, 140°C, 150°C or a range between any two of the above values; the vacuum drying time is preferably 0.5 to 3 hours; optionally, the vacuum drying time is 0.5h, 1h, 1.5h, 2h, 2.5h, 3h or a range between any two of the above values; the vacuum degree of the vacuum drying is preferably less than 0.1 torr; The inert gas can be any inert gas well known to those skilled in the art without any special limitation. In the present invention, nitrogen is preferably used. The flow rate of the inert gas during cleaning is preferably 100 to 500 sccm. Optionally, the flow rate of the inert gas during cleaning is 100 sccm, 200 sccm, 300 sccm, 400 sccm, 500 sccm, or a range between any two of the above values. The time for cleaning with the inert gas is preferably 0 to 1 h. Optionally, the time for cleaning with the inert gas is 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, or a range between any two of the above values.

[0086] In a specific embodiment provided by the present invention, vacuum drying and inert gas cleaning of the ternary positive electrode material are carried out in an ALD reaction chamber; the moisture contained in the ternary positive electrode material can be removed by vacuum drying and inert gas cleaning, and coating can be carried out directly after completion to avoid the introduction of impurities.

[0087] In the present invention, the complete reaction of an atomic layer deposition layer includes four steps: (a) introducing a first precursor into the reaction chamber for pulse adsorption; (b) purging with an inert gas; (c) introducing a second precursor into the reaction chamber for pulse reaction; and (d) purging with an inert gas.

[0088] In the present invention, the type of the first precursor can be selected according to the type of the atomic layer deposition layer, and can be one or more of a lithium source precursor, an M source precursor, an M' source precursor, and a fluorine source precursor; the lithium source precursor is a lithium source precursor well known to those skilled in the art, and is not particularly limited, including but not limited to LiO t Bu (lithium tert-butoxide) and / or LiOC2H5 (lithium ethoxide); the M source precursor includes but is not limited to Mn(thd)3 (tris(2,2,6,6-tetramethyl-3,5-heptanedione) manganese), CpMn(CO)3 (cyclopentadienyl manganese tricarbonyl), Mn(EtCp)2 (diethylcyclopentadienyl manganese), Ni(thd)2 (nickel bis(2,2,6,6-tetramethyl-3,5-heptanedione)), NiCp2 (nickelocene), Ni(acac)2 (nickel acetylacetonate), VO(thd)2 (vanadium bis(2,2,6,6-tetramethyl-3,5-heptanedione)), V( One or more of NMe2)4 (tetrakis(dimethylamino)vanadium), Cr(thd)3 (tris(2,2,6,6-tetramethyl-3,5-heptanedione)chromium), CpCr(CO)3 (cyclopentadienyltricarbonylchromium), Fe(thd)3 (tris(2,2,6,6-tetramethyl-3,5-heptanedione)iron) and FeCp2 (ferrocene); the M' source precursor includes but is not limited to MoCl5 (molybdenum pentachloride), Mo(CO)6 (molybdenum hexacarbonyl), WCl6 (tungsten hexachloride), WF6 (tungsten hexafluoride), TiCl4 (titanium tetrachloride), TTIP (tetraisopropyl titanate, Ti(O i One or more of: Pr)4), Zr(thd)4 (tetrakis(2,2,6,6-tetramethyl-3,5-heptanedione) zirconium), TEMAZ (tetrakis(ethylmethylamino) zirconium, Zr(NEtMe)4), Nb(OEt)5 (niobium ethoxide), NbCl5 (niobium pentachloride), Ta(OEt)5 (tantalum pentaethoxide) and TaCl5 (tantalum pentachloride); the fluorine source precursor can be a fluorine source precursor well known to those skilled in the art, without special restrictions, and is preferably a transition metal fluoride in the present invention; the transition metal in the transition metal fluoride is preferably M and / or M'.

[0089] In the present invention, the second precursor is an oxidant; the oxidant is any oxidant well known to those skilled in the art without any particular limitation. In the present invention, the oxidant preferably includes but is not limited to one or more of ozone, water and ethanol.

[0090] In the present invention, the flow rates of the first precursor and the second precursor are each independently preferably 1 to 800 sccm, more preferably 100 to 600 sccm; optionally, the flow rates of the first precursor and the second precursor are each independently 100 sccm, 200 sccm, 300 sccm, 400 sccm, 500 sccm, 600 sccm or a range between any two of the above values.

[0091] In the present invention, the temperature for preparing one atomic layer deposition layer or multiple atomic layer deposition layers can be set according to the saturated vapor pressure of different types of precursors, preferably 0°C to 500°C, more preferably 25°C to 400°C; optionally, the temperature for preparing one atomic layer deposition layer or multiple atomic layer deposition layers is 25°C, 50°C, 100°C, 150°C, 190°C, 200°C, 250°C, 300°C, 350°C, 400°C or a range between any two of the above values.

[0092] In a specific embodiment provided by the present invention, the time of the pulse adsorption is preferably 0 to 60 s (excluding 0), more preferably 0 to 30 s (excluding 0), further preferably 1 to 20 s, further preferably 1 to 10 s, and most preferably 1 to 5 s; optionally, the time of the pulse adsorption is 1 s, 2 s, 3 s, 4 s, 5 s or a range between any two of the above values.

[0093] In a specific embodiment provided by the present invention, the inert gas used for purging can be any inert gas well known to those skilled in the art without any particular limitation. In the present invention, nitrogen is preferably used.

[0094] In a specific embodiment provided by the present invention, the purge time of the inert gas is preferably 10 to 240 s, more preferably 30 to 120 s, and even more preferably 60 to 120 s.

[0095] In a specific embodiment provided by the present invention, the time of the pulse reaction is preferably 0 to 60 s (excluding 0), more preferably 0 to 30 s (excluding 0), further preferably 1 to 20 s, further preferably 1 to 10 s, and most preferably 1 to 5 s; optionally, the time of the pulse adsorption is 1 s, 2 s, 3 s, 4 s, 5 s or a range between any two of the above values.

[0096] Multi-layer atomic layer deposition layers are formed by multi-layer alternating cyclic deposition. The specific type of each layer is the same as described above and will not be repeated here; the number of alternating cycles is preferably 1 to 1000 times, more preferably 1 to 500 times, more preferably 1 to 100 times, more preferably 1 to 50 times, and most preferably 2 to 10 times; optionally, the number of alternating cycles is 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times or a range between any two of the above values.

[0097] In a specific embodiment provided by the present invention, the temperature of the annealing treatment is preferably 100°C to 500°C; optionally, the temperature of the annealing treatment is 100°C, 200°C, 300°C, 400°C, 500°C or a range between any two of the above values; the time of the annealing treatment is preferably greater than 0h, more preferably greater than 0h and less than or equal to 24h; optionally, the time of the annealing treatment is 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h or a range between any two of the above values. Annealing treatment can promote the migration of Li+ from Li2O to the first transition metal oxide atomic layer deposition layer and / or the second transition metal oxide atomic layer deposition layer, occupying the octahedral interstitial sites. At the same time, the mutual diffusion effect during the annealing process is used to promote cation disordering and form a disordered rock salt phase. In addition, in this process, F- partially replaces O2- (forming O vacancies, promoting Li+ diffusion).

[0098] In a specific embodiment provided by the present invention, the temperature of the annealing treatment is preferably 200° C. to 500° C.; and the time of the annealing treatment is preferably 1 to 12 hours.

[0099] The present invention also provides a positive electrode, comprising the positive electrode material coated with the lithium-rich disordered rock salt layer.

[0100] In a specific embodiment provided by the present invention, the positive electrode includes a positive electrode collector and a positive electrode active layer arranged on at least one surface of the positive electrode collector; the positive electrode active layer includes the above-mentioned positive electrode material coated with the lithium-rich disordered rock salt layer, a conductive agent, a solid electrolyte and a binder.

[0101] In a specific embodiment provided by the present invention, the positive electrode current collector can be any positive electrode current collector well known to those skilled in the art without any special limitation. In the present invention, it is preferably aluminum foil or carbon-coated aluminum foil.

[0102] In a specific embodiment provided by the present invention, the mass content of the positive electrode material coated with the lithium-rich disordered rock salt layer in the positive electrode active layer is preferably greater than or equal to 70%, more preferably 70% to 99%; optionally, the mass content of the positive electrode material coated with the lithium-rich disordered rock salt layer in the positive electrode active layer is 70%, 75%, 80%, 85%, 90%, 95%, 99% or a range between any two of the above values.

[0103] In a specific embodiment provided by the present invention, the conductive agent is preferably conductive carbon, more preferably one or more of vapor-grown carbon fiber, Super-P, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, Ketjen black and acetylene black.

[0104] In a specific embodiment provided by the present invention, the mass of the conductive agent is preferably 0.1% to 5% of the mass of the positive electrode active layer; optionally, the mass of the conductive agent is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% of the mass of the positive electrode active layer or a range between any two of the above values.

[0105] In a specific embodiment provided by the present invention, the solid electrolyte is preferably a sulfide solid electrolyte; the sulfide solid electrolyte is a sulfide solid electrolyte well known to those skilled in the art, and is not particularly limited, including but not limited to Li7P3S 11 、Li3PS4、Li6PS5Cl、Li 10 GeP2S 12 、Li6PS5Br、Li 5.5 PS 4.5 Cl 1.5 With Li 5.3 PS 4.3 Cl 0.8 Br 0.7 One or more of.

[0106] In a specific embodiment provided by the present invention, the D50 of the solid electrolyte is preferably 0.5 to 8 μm; optionally, the D50 of the solid electrolyte is 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm or a range between any two of the above values.

[0107] In a specific embodiment provided by the present invention, the mass of the solid electrolyte is preferably 10% to 29.8% of the mass of the positive electrode active layer; optionally, the mass of the solid electrolyte is 10%, 15%, 20%, 22%, 23%, 23.8%, 25%, 28%, 29.8% of the mass of the positive electrode active layer or a range between any two of the above values.

[0108] In a specific embodiment provided by the present invention, the binder can be any binder well known to those skilled in the art without any special limitation, including but not limited to one or more of polyvinyl alcohol, hydrogenated nitrile rubber, styrene-butadiene rubber, polytetrafluoroethylene and polyvinylidene fluoride.

[0109] In a specific embodiment provided by the present invention, the mass of the binder is preferably 0.1% to 5% of the mass of the positive electrode active layer; optionally, the mass of the binder is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% of the mass of the positive electrode active layer or a range between any two of the above values.

[0110] In a specific embodiment provided by the present invention, the surface density of the positive electrode active layer is preferably 10 to 40 mg / cm 2 ; Optionally, the surface density of the positive electrode active layer is 10 mg / cm 2 , 20mg / cm 2 、30mg / cm 2 , 40mg / cm 2 Or the range between any two of the above values.

[0111] The present invention also provides a solid-state lithium battery comprising the above-mentioned positive electrode.

[0112] In a specific embodiment provided by the present invention, the solid-state lithium battery further includes a negative electrode and an electrolyte separator.

[0113] In a specific embodiment provided by the present invention, the negative electrode can be any negative electrode well known to those skilled in the art without any special limitation, including but not limited to lithium metal alloy, lithium indium alloy, lithium metal, graphite, Si-C composite negative electrode, etc.

[0114] In a specific embodiment provided by the present invention, the electrolyte membrane is preferably a sulfide electrolyte membrane, more preferably including but not limited to Li7P3S 11 、Li3PS4、Li6PS5Cl、Li 10 GeP2S 12 、Li6PS5Br、Li 5.5 PS 4.5 Cl 1.5 With Li 5.3 PS 4.3 Cl 0.8 Br 0.7 One or more of.

[0115] To further illustrate the present invention, a positive electrode material coated with a lithium-rich disordered rock salt layer, a preparation method thereof, and a solid-state lithium battery provided by the present invention are described in detail below in conjunction with examples.

[0116] The reagents used in the following examples are all commercially available.

[0117] Example 1: Lithium-rich disordered rock salt phase coating layer Li 1.35 Nb 0.25 Mn 0.4 O 1.95 F 0.05

[0118] (1) Weigh 200g LiNi 0.8 Co 0.1 Mn 0.1 O2 single crystal cathode material (D50≈3.6μm) is placed in an ALD reaction chamber and evacuated to a vacuum (<0.1torr).

[0119] (2) The powder was vacuum dried at 120 °C for 1 h and purged with inert gas (N2, flow rate 300 sccm) for 10 min.

[0120] (3) Setting the ALD process: Setting the reaction chamber temperature to 190°C;

[0121] (3.1) Lithium layer deposition: LiOtBu (flow rate set to 200 sccm, pulse 2s) is introduced into the reaction chamber → N2 purge (flow rate set to 500 sccm, purge 60s) → O3 (flow rate set to 200 sccm, pulse 4s) → N2 purge (flow rate set to 500 sccm, purge 60s) to form Li2O amorphous / nanocrystalline oxide, construct a lithium-rich interface, and provide a Li+ source;

[0122] (3.2) Mn / Nb co-deposition: Mn(thd)3 (flow rate set at 300 sccm, pulse 4 s) → Nb(OEt)5 (flow rate set at 300 sccm, pulse 2 s) → N2 purge (flow rate set at 500 sccm, purge 120 s) → O3 (flow rate set at 500 sccm, pulse 6 s) → N2 purge (flow rate set at 500 sccm, purge 60 s) were introduced into the reaction chamber to form MnNbO x Amorphous / nanocrystalline oxides;

[0123] (3.3) F doping: TiF4 (flow rate set to 150 sccm, pulse 1s) was introduced into the reaction chamber → N2 purge (flow rate set to 500 sccm, purge 60s) → O3 (flow rate set to 300 sccm, pulse 2s) → N2 purge (flow rate set to 500 sccm, purge 60s) to form F doping source TiO x F n Amorphous / nanocrystalline oxides;

[0124] In the above process, (3.1-3.2) is cycled three times, followed by (3.3) once, and then (3.1-3.2) is cycled twice, for a total of six cycles, to control the thickness of the amorphous / nanocrystalline lithium-rich disordered rock salt phase coating to be 2-5 nm;

[0125] After the above ALD process, the ALD chamber temperature was set to 300 ° C and low temperature annealing was performed for 2 hours to promote the transfer of Li+ from Li2O to MnNbO x Migrate and occupy the octahedral interstitial sites. At the same time, the cations in the amorphous / nanocrystalline oxides are disordered, and Mn / Nb atoms randomly occupy the transition metal sites, breaking the long-range order and forming a disordered rock salt phase. - Partially substituted O 2- (forming O vacancies, promoting Li + Diffusion). The Mn / Nb sites in the lithium-rich disordered rock salt phase have a significant influence on the Ti 4+ The solid solubility of F- Compare Easier to replace So Ti tends to form surface TiO x (Byproducts) volatilize or retain a very small amount, which can be ignored. Finally, the positive electrode material B1 (LiNi 0.8 Co 0.1 Mn 0.1 O2@Li 1.35 Nb 0.25 Mn 0.4 O 1.95 F 0.05 ).

[0126] (4) Appropriate amounts of coated cathode materials B1, Li6PS5Cl (D50≈3 μm), VGCF, and PTFE were weighed in a mass ratio of 75:23.8:1:0.2, and the four materials were fully mixed and coated on a carbon-coated aluminum foil current collector by dry roller pressing to prepare a cathode (about 18 mg of the mixed cathode was weighed and pressed on the current collector at 210 MPa for 8 min). The cathode active material was 20 mg / cm 2 The positive electrode, Li6PS5Cl solid electrolyte membrane (150 mg solid electrolyte, 100 MPa, 10 min compaction, thickness of about 3 mm) and lithium indium alloy sheet (indium sheet diameter 15 mm, thickness 100 μm, lithium sheet diameter 8 mm, thickness 50 μm, pressed at 100 MPa, 20 min) were pressed at 200 MPa for 10 min and then assembled into a sandwich-structured sulfide solid-state lithium-ion battery.

[0127] At 25°C, the prepared battery was charged and discharged at a current density of 0.1C, with a charge and discharge range of 2.5V to 4.3V (vs Li / Li + ), the charge and discharge curve of the assembled sulfide solid-state lithium-ion battery in the first cycle is as follows Figure 1 As shown, the cycle retention rate curve of the assembled sulfide solid-state lithium-ion battery is as shown in Figure 2 As shown. Figure 1 It can be seen that the discharge capacity of the battery during the first charge and discharge process is 211.2mAh / g, and the charge and discharge efficiency is 85.2%. Figure 2 It can be seen that the capacity retention rate after 50 cycles at 0.33C is 95.8%.

[0128] Example 2: Lithium-rich disordered rock salt phase coating layer Li 1.3 Mn 0.4 Ti 0.3 O2

[0129] (1) Weigh 200g LiNi 0.93 Co 0.05 Mn 0.02 O2 single crystal cathode material (D50≈2.5μm) is placed in an ALD reaction chamber and evacuated to a vacuum (<0.1torr).

[0130] (2) The powder was vacuum dried at 120 °C for 1 h and purged with inert gas (N2, flow rate 300 sccm) for 10 min.

[0131] (3) Set the ALD process: set the reaction chamber temperature to 200°C;

[0132] (3.1) Lithium layer deposition: LiO is introduced into the reaction chamber t Bu (flow setting 230sccm, pulse 2s) → N2 purge (flow setting 500sccm, purge 60s) → O3 (flow setting 230sccm, pulse 4s) → N2 purge (flow setting 500sccm, purge 60s) to form Li2O amorphous / nanocrystalline oxide, build a lithium-rich interface, and provide Li + source;

[0133] (3.2) Mn layer deposition: Mn(thd)3 (flow rate set to 300 sccm, pulse 2s) is introduced into the reaction chamber → N2 purge (flow rate set to 500 sccm, purge 60s) → O3 (flow rate set to 300 sccm, pulse 4s) → N2 purge (flow rate set to 500 sccm, purge 60s) to form MnO x Amorphous / nanocrystalline oxides;

[0134] The above process is repeated twice to accumulate the Li-Mn-O intermediate phase and preliminarily build the Mn-O framework;

[0135] (3.3) Lithium layer deposition: LiOtBu (flow rate set to 230 sccm, pulse 2s) was introduced into the reaction chamber → N2 purge (flow rate set to 500 sccm, purge 60s) → O3 (flow rate set to 230 sccm, pulse 4s) → N2 purge (flow rate set to 500 sccm, purge 60s) to add a new Li2O layer, replenish the Li source, and provide reaction sites for Ti deposition;

[0136] (3.4) Ti layer deposition: Ti(O i Pr)4 (flow rate setting 300sccm, pulse 2s) → N2 purge (flow rate setting 500sccm, purge 60s) → O3 (flow rate setting 300sccm, pulse 4s) → N2 purge (flow rate setting 500sccm, purge 60s) to form TiO x Amorphous / nanocrystalline oxides;

[0137] The above process was repeated twice to accumulate the Li-Ti-O intermediate phase and preliminarily construct the Ti-O framework.

[0138] After the above ALD process is completed, the ALD chamber temperature is set to 300 ° C and low-temperature annealing is performed for 2 hours. By depositing Li-Mn-O and Li-Ti-O intermediate phases in steps, the atomic migration path is shortened, the cation migration energy barrier is reduced, and the mutual diffusion effect during the annealing process is used to promote the disordering of cations (Mn / Ti), thereby more efficiently forming a stable disordered rock salt (lithium-rich disordered rock salt phase) phase, and finally obtaining a positive electrode material B2 (LiNi) coated with a 2-5 nm lithium-rich disordered rock salt phase layer. 0.93 Co 0.05 Mn 0.02 O2@Li 1.3 Mn 0.4 Ti 0.3 O2).

[0139] (4) Appropriate amounts of coated positive electrode materials B2, Li6PS5Cl (D50≈3 μm), VGCF, and PTFE were weighed in a mass ratio of 75:23.8:1:0.2, and the four materials were fully mixed and coated on a carbon-coated aluminum foil current collector by dry roller pressing to prepare a positive electrode (the preparation method was the same as in the example). The positive electrode active material was 20 mg / cm 2The positive electrode, Li6PS5Cl solid electrolyte membrane (thickness of about 3 mm, prepared in the same way as in Example 1) and lithium indium alloy sheet (indium sheet diameter 15 mm, thickness 100 μm, lithium sheet diameter 8 mm, thickness 50 μm, pressed at 100 MPa for 20 min) were assembled into a sulfide solid-state lithium-ion battery after pressing at 200 MPa for 10 min.

[0140] At 25°C, the prepared battery was charged and discharged at a current density of 0.1C, with a charge and discharge range of 2.5V to 4.3V (vs Li / Li + ), the battery obtained has a discharge capacity of 216.9 mAh / g during the first charge and discharge process, a charge and discharge efficiency of 85.4%, and a capacity retention rate of 95.3% after 50 cycles at 0.33C.

[0141] Example 3: Lithium-rich disordered rock salt phase coating layer Li 1.3 Nb 0.2 Ti 0.2 Mn 0.3 O 1.92 F 0.08

[0142] (1) Weigh 200g LiNi 0.95 Co 0.04 Mn 0.01 O2 single crystal cathode material (D50≈3.2μm) is placed in an ALD reaction chamber and evacuated to a vacuum (<0.1torr).

[0143] (2) The powder was vacuum dried at 120 °C for 1 h and purged with inert gas (N2, flow rate 300 sccm) for 10 min.

[0144] (3) Set the ALD process: set the reaction chamber temperature to 200°C;

[0145] (3.1) Lithium layer deposition: LiO is introduced into the reaction chamber t Bu (flow setting 200sccm, pulse 2s) → N2 purge (flow setting 500sccm, purge 60s) → O3 (flow setting 200sccm, pulse 4s) → N2 purge (flow setting 500sccm, purge 60s) to form Li2O amorphous / nanocrystalline oxide, build a lithium-rich interface, and provide Li + source;

[0146] (3.2) Mn / Nb co-deposition: Mn(thd)3 (flow rate set to 400 sccm, pulse 5s) → Nb(OEt)5 (flow rate set to 260 sccm, pulse 5s) → N2 purge (flow rate set to 500 sccm, purge 120s) → O3 (flow rate set to 500 sccm, 5s) → N2 purge (flow rate set to 500 sccm, purge 60s) are introduced into the reaction chamber to form MnNbO x Amorphous / nanocrystalline oxides;

[0147] The above process (3.1-3.2) is cycled twice to accumulate the Li-Mn-Nb-O intermediate phase and preliminarily build the Mn-Nb-O framework;

[0148] (3.3) Lithium layer deposition: LiO is introduced into the reaction chamber t Bu (flow rate setting 230 sccm, pulse 2s) → N2 purge (flow rate setting 500 sccm, purge 60s) → O3 (flow rate setting 200 sccm, pulse 4s) → N2 purge (flow rate setting 500 sccm, purge 60s) to add a new Li2O layer, replenish the Li source, and provide reaction sites for the next deposition;

[0149] (3.4) Mn / Ti co-deposition: Mn(thd)3 (flow rate 400 sccm, pulse 5s) → Ti(O i Pr)4 (flow rate setting 300sccm, pulse 4s) → N2 purge (flow rate setting 500sccm, purge 120s) → O3 (flow rate setting 500sccm, 5s) → N2 purge (flow rate setting 500sccm, purge 60s) to form MnNbO x Amorphous / nanocrystalline oxides;

[0150] The above process (3.3-3.4) is cycled twice to accumulate the Li-Mn-Ti-O intermediate phase and preliminarily construct the Mn-Ti-O framework;

[0151] (3.3) F doping: TiF4 (flow rate set to 200 sccm, pulse 2s) is introduced into the reaction chamber → N2 purge (flow rate set to 500 sccm, purge 60s) → O3 (flow rate set to 300 sccm, pulse 2s) → N2 purge (flow rate set to 500 sccm, purge 60s) to form F doping source TiO x F n Amorphous / nanocrystalline oxides, forming F-doped TiO x F n Amorphous / nanocrystalline oxides.

[0152] After the above ALD process is completed, the ALD chamber temperature is set to 300 ° C, and low-temperature annealing is performed for 2 hours to form a stable disordered rock salt (lithium-rich disordered rock salt phase) phase, and finally the positive electrode material B3 (LiNi 0.95 Co 0.04 Mn 0.01 O2@Li 1.3 Nb 0.2 Ti 0.2 Mn 0.3 O 1.92 F 0.08 ), through high valence state (Nb 5+ ), dual TM synergy (Nb-Ti combination), F doping and other designs, B3 can be more resistant to high pressure.

[0153] (4) Appropriate amounts of coated positive electrode materials B3, Li6PS5Cl (D50≈3 μm), VGCF, and PTFE were weighed in a mass ratio of 75:23.8:1:0.2, and the four materials were fully mixed and coated on a carbon-coated aluminum foil current collector by dry roller pressing to prepare a positive electrode (the preparation method was the same as in Example 1). The positive electrode active material was 20 mg / cm 2 The positive electrode, Li6PS5Cl solid electrolyte membrane (thickness of about 3 mm, prepared in the same way as in Example 1) and lithium indium alloy sheet (indium sheet diameter 15 mm, thickness 100 μm, lithium sheet diameter 8 mm, thickness 50 μm, pressed at 100 MPa for 20 min) were assembled into a sulfide solid-state lithium-ion battery after pressing at 200 MPa for 10 min.

[0154] At 25°C, the prepared battery was charged and discharged at a current density of 0.1C, with the charge and discharge range of 2.5V to 4.5V (vs Li / Li + ), the battery obtained has a discharge capacity of 221.5 mAh / g during the first charge and discharge process, a charge and discharge efficiency of 86.1%, and a capacity retention rate of 94.6% after 50 cycles at 0.33C.

[0155] Comparative Example 1

[0156] The original LiNi without coating layer in Example 1 0.8 Co 0.1 Mn 0.1 O2 powder.

[0157] A sulfide solid-state lithium-ion battery was assembled using the same method as in Example 1. Under the same test conditions, the battery exhibited a discharge capacity of 185.6 mAh / g and a charge-discharge efficiency of 78.3% during the initial charge-discharge process. After 50 cycles at 0.33C, the battery maintained a capacity of 77.3%.

[0158] Comparative Example 2

[0159] The original LiNi without coating layer in Example 2 0.93 Co 0.05 Mn 0.02 O2 powder.

[0160] A sulfide solid-state lithium-ion battery was assembled using the same method as in Example 2. Under the same test conditions, the battery exhibited a discharge capacity of 190.2 mAh / g during the initial charge and discharge process, a charge and discharge efficiency of 79.6%, and a capacity retention of 76.4% after 50 cycles at 0.33C.

[0161] Comparative Example 3

[0162] The original LiNi without coating layer in Example 3 0.95 Co 0.04 Mn 0.01 O2 powder.

[0163] A sulfide solid-state lithium-ion battery was assembled using the same method as in Example 3. Under the same test conditions, the battery exhibited a discharge capacity of 198.1 mAh / g during the initial charge and discharge process, a charge and discharge efficiency of 79.1%, and a capacity retention of 74.7% after 50 cycles at 0.33C.

[0164] Comparative Example 4

[0165] Weigh 200g LiNi 0.8 Co 0.1 Mn 0.1 O2 (raw material used in Example 1), Li 1.25 Nb 0.25 Mn 0.5 O 1.9 F 0.1 According to the stoichiometric ratio, the coating layer accounts for ≈1.5% by mass. 1.8 g LiOH·H2O (5% excess Li), 1.4 g MnO2, 1.1 g Nb2O5, and 0.08 g LiF were weighed and placed in a ball mill. 500 g anhydrous ethanol and 2000 g tungsten carbide balls were added. The mixture was ball milled at 300 rpm for 12 h. After mixing evenly, the mixture was vacuum dried at 80 ° C for 6 h to completely remove ethanol. The temperature was raised to 300 ° C at a heating rate of 2.5 ° C in an oxygen atmosphere, kept warm for 12 h, and naturally cooled to obtain Comparative Example 4.

[0166] A sulfide solid-state lithium-ion battery was assembled using the same method as in Example 1. Under the same test conditions, the battery exhibited a discharge capacity of 186.3 mAh / g during the initial charge and discharge process, a charge and discharge efficiency of 79.3%, and a capacity retention of 79.1% after 50 cycles at 0.33C.

[0167] Comparative Example 5

[0168] Weigh 200g LiNi 0.93 Co 0.05 Mn 0.02 O2 (raw materials used in Example 2), 1.9g LiOH·H2O, 1.3gMnO2, 1.2g TiO2, and 0.14g LiF were placed in a ball mill, and 500g anhydrous ethanol (solid-liquid ratio ≈1:2.5) and 2000g tungsten carbide balls (ball-to-material ratio ≈10:1) were added. The mixture was ball milled at 300rpm for 12h. After mixing evenly, the mixture was vacuum dried at 80°C for 6h, heated to 300°C at a heating rate of 2.5°C in an oxygen atmosphere, kept warm for 12h, and cooled naturally to obtain Comparative Example 5.

[0169] A sulfide solid-state lithium-ion battery was assembled using the same method as in Example 2. Under the same test conditions, the battery exhibited a discharge capacity of 192.7 mAh / g and a charge-discharge efficiency of 80.2% during the initial charge-discharge process. After 50 cycles at 0.33C, the battery maintained a capacity of 78.5%.

[0170] Comparative Example 6

[0171] Weigh 200g LiNi 0.95 Co 0.04 Mn 0.01 O2 (raw materials used in Example 3), 1.9g LiOH·H2O, 1.0gMnO2, 0.54g TiO2, 0.9g Nb2O5, and 0.18g LiF were placed in a ball mill, 500g anhydrous ethanol and 2000g tungsten carbide balls were added, and the mixture was ball milled at 300rpm for 12h. After mixing evenly, the mixture was vacuum dried at 80°C for 6h, heated to 300°C at a heating rate of 2.5°C in an oxygen atmosphere, kept warm for 12h, and naturally cooled to obtain Comparative Example 6.

[0172] A sulfide solid-state lithium-ion battery was assembled using the same method as in Example 3. Under the same test conditions, the battery exhibited a discharge capacity of 199.4 mAh / g during the initial charge and discharge process, a charge and discharge efficiency of 79.5%, and a capacity retention of 76.2% after 50 cycles at 0.33C.

[0173] The process and test data of the positive electrode materials, positive electrode sheets and sulfide solid-state lithium-ion batteries obtained through Examples 1 to 3 and Comparative Examples 1 to 6 were statistically analyzed, and the results are shown in Table 1.

[0174] The interface resistance of the sulfide solid-state lithium-ion batteries obtained in Examples 1 to 3 and Comparative Examples 1 to 6 was tested by electrochemical impedance spectroscopy (EIS). The test amplitude was 5 mV and the frequency range was 0.1-10 5 Hz, and the results are shown in Table 1.

[0175] Table 1 Test results of sulfide solid-state lithium-ion batteries

[0176]

[0177] As shown in Table 1, the results of Examples 1 to 3, Comparative Examples 4 to 6 and Comparative Examples 1 to 3 show that surface coating of the positive electrode material can reduce the interfacial resistance of the battery and improve the discharge capacity and cycle efficiency of the battery.

[0178] It can be seen from the results of Examples 1 to 3 and Comparative Examples 4 to 6 that although similar coating materials are used, since Comparative Examples 4 to 6 adopt the traditional ball milling coating method, the ability to reduce the interfacial resistance of the battery is limited, and the improvement of the battery's discharge specific capacity and cycle efficiency is limited. This further illustrates that the coating layer prepared by ALD technology is uniform and dense, which can effectively inhibit the side reaction between the positive electrode material and the solid electrolyte, reduce the interfacial impedance, optimize the ion transfer kinetics, and effectively improve the capacity, rate performance and cycle stability of the solid-state lithium-ion battery.

[0179] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A positive electrode material coated with a lithium-rich disordered rock salt layer, characterized in that: It includes an inner core and a covering layer wrapped around the inner core; The core is a ternary positive electrode material; The coating layer is a lithium-rich disordered rock salt material; the chemical formula of the lithium-rich disordered rock salt material is Li 1+x M y M' z O 2-n F n ; Wherein, x>0, y>0, z≥0, 0≤n<2; M is a transition metal element with redox activity; and M' is a transition metal element and / or a d0 transition metal element that is redox inert.

2. The positive electrode material according to claim 1, characterized in that The chemical formula of the ternary cathode material is LiNi a Co b Mn c O2; wherein, 0.10≤a<1, 0<b<1, 0<c<1, a+b+c=1; And / or, the M is selected from one or more of Mn, Ni, V, Cr and Fe; And / or, the M' is selected from one or more of Ti, Zr, Nb, Mo, Ta and W; and / or, the coating layer has a thickness of 1 to 20 nm; and / or, 0.1≤x≤0.5; and / or, 0.1≤y≤0.5; and / or, 0≤z≤0.5; and / or, 0≤n≤0.1; and / or, 0.8≤a<1.

3. The positive electrode material according to claim 1, characterized in that The coating layer is formed by an atomic layer deposition layer or multiple atomic layer deposition layers after annealing; The multi-layer atomic layer deposition layer includes at least one lithium oxide atomic layer deposition layer and at least one first transition metal oxide atomic layer deposition layer; the first transition metal oxide atomic layer deposition layer includes M oxide; The lithium oxide atomic layer deposition layer is in contact with the core.

4. The positive electrode material according to claim 3, characterized in that The multi-layer atomic layer deposition layer includes a multi-layer lithium oxide atomic layer deposition layer and a multi-layer first transition metal oxide atomic layer deposition layer, and the lithium oxide atomic layer deposition layer and the first transition metal oxide atomic layer deposition layer are arranged alternately; And / or, the temperature of the annealing treatment is 100° C. to 500° C.; and the time of the annealing treatment is greater than 0 h.

5. The positive electrode material according to claim 3, characterized in that The first transition metal oxide atomic layer further includes M' oxide; And / or, the multi-layer atomic layer deposition layer further comprises at least one second transition metal oxide atomic layer deposition layer; the second transition metal oxide atomic layer comprises M' oxide; And / or, the multi-layer atomic layer deposition layer further includes at least one transition metal oxyfluoride atomic layer deposition layer; the transition metal oxyfluoride atomic layer deposition layer includes M and / or M'.

6. The positive electrode material according to claim 5, characterized in that The multi-layer atomic layer deposition layer includes a multi-layer second transition metal oxide atomic layer deposition layer; the multi-layer second transition metal oxide atomic layer deposition layer is separated by a lithium oxide atomic layer deposition layer; the first transition metal oxide atomic layer deposition layer and the second transition metal oxide atomic layer deposition layer are separated by a lithium oxide atomic layer deposition layer.

7. A method for preparing a positive electrode material coated with a lithium-rich disordered rock salt layer according to any one of claims 1 to 6, characterized in that: The following steps are involved: An atomic layer deposition layer or multiple atomic layer deposition layers are prepared on the surface of the ternary positive electrode material, and annealing treatment is performed to obtain a positive electrode material coated with a lithium-rich disordered rock salt layer; the multiple atomic layer deposition layers include at least one lithium oxide atomic layer deposition layer and at least one first transition metal oxide atomic layer deposition layer; the first transition metal oxide atomic layer deposition layer includes M oxide; and the lithium oxide atomic layer deposition layer is in contact with the core.

8. A positive electrode, characterized in that The invention comprises the positive electrode material coated with the lithium-rich disordered rock salt layer according to any one of claims 1 to 6 or the positive electrode material coated with the lithium-rich disordered rock salt layer prepared by the preparation method according to claim 7.

9. The positive electrode according to claim 8, characterized in that The positive electrode comprises a positive electrode current collector and a positive electrode active layer provided on at least one surface of the positive electrode current collector; the positive electrode active layer comprises the positive electrode material coated with the lithium-rich disordered rock salt layer according to any one of claims 1 to 6 or the positive electrode material coated with the lithium-rich disordered rock salt layer prepared by the preparation method according to claim 7, a conductive agent, a solid electrolyte and a binder; The mass content of the positive electrode material coated with the lithium-rich disordered rock salt layer in the positive electrode active layer is greater than or equal to 70%; And / or, the conductive agent is selected from one or more of vapor-grown carbon fiber, Super-P, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, Ketjen black and acetylene black; and / or, the solid electrolyte is selected from sulfide solid electrolytes; And / or, the binder is selected from one or more of polyvinyl alcohol, hydrogenated nitrile rubber, styrene-butadiene rubber, polytetrafluoroethylene and polyvinylidene fluoride.

10. A solid-state lithium battery, characterized in that: Comprising the positive electrode according to claim 8 or 9.

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