WO2023045110A1 - 电极包覆材料筛选方法、电极材料、二次电池 - Google Patents

电极包覆材料筛选方法、电极材料、二次电池 Download PDF

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WO2023045110A1
WO2023045110A1 PCT/CN2021/137618 CN2021137618W WO2023045110A1 WO 2023045110 A1 WO2023045110 A1 WO 2023045110A1 CN 2021137618 W CN2021137618 W CN 2021137618W WO 2023045110 A1 WO2023045110 A1 WO 2023045110A1
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electrode
coating material
energy
electrode active
active material
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PCT/CN2021/137618
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English (en)
French (fr)
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薛冬峰
彭超
王晓明
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中国科学院深圳先进技术研究院
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/08—Thermal analysis or thermal optimisation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the application belongs to the technical field of batteries, and in particular relates to a screening method for electrode coating materials, an electrode material, and a secondary battery.
  • the ternary cathode material has excellent electrochemical performance, there will be a certain capacity fading in the lithium-ion battery cathode material during the battery service process.
  • the main reasons include side reactions at the cathode/electrolyte interface and lithium dendrite formation.
  • the current effective method is to coat the surface of the positive electrode material with a layer of material to avoid direct contact between the surface of the positive electrode and the electrolyte, or to dope the surface elements to passivate the highly active sites on the surface and inhibit the chemical reaction with the interface electrolyte.
  • the surface of LiNi 0.50 Mn 0.30 Ni 0.20 O 2 (NCM532) is coated with Li 2 TiO 2 rock-salt structure oxide, which can be well attached to the surface of NCM532 and inhibit the positive electrode/electrolyte interface reaction; the surface of NCM71515 positive electrode is coated with Li 2 ZrO 3 It can effectively protect the positive electrode structure and promote the transport of lithium ions.
  • the surface coating material of the positive electrode is still in the "trial and error" stage. After selecting a positive electrode coating material and preparing the core-shell structure of the positive electrode coating material, it needs to be assembled into a full battery for electrochemical property testing to verify the performance of the coating material. As a result, this type of experimental method is inefficient and cumbersome. How to accurately predict the coating material and realize the screening is a technical problem that needs to be solved urgently.
  • the purpose of this application is to provide a screening method for electrode coating materials, as well as an electrode material, a secondary battery, which aims to solve the problem of screening electrode coating materials to a certain extent, which needs to be assembled into a full battery for electrochemical performance testing. To verify the effect of the coating material, the efficiency is low and the procedure is cumbersome.
  • the present application provides a method for screening electrode coating materials, comprising the following steps:
  • the migration rate of lithium ions is calculated by density functional theory, and the migration system of the coating material is determined;
  • the reaction barrier and reaction thermodynamics between the coating material and the electrolyte are calculated by density functional theory, and the reaction kinetic system of the coating material is determined;
  • the electrode coating material is obtained by screening.
  • the present application provides an electrode material, the electrode material is a core-shell structure, including an electrode active material inner core and a shell layer coated on the outer surface of the inner core, and the electrode coating material of the shell layer is composed of the above-mentioned Screened by the electrode coating material screening method.
  • the present application provides a secondary battery, characterized in that the secondary battery includes the above-mentioned electrode material.
  • the electrode coating material screening method calculates the surface energy of different crystal planes of the electrode active material through density functional theory, investigates the stability of the surface structure of the electrode active material, and uses crystal planes with stable surface structures as electrodes The interface structure of the active material; at the same time, the surface energy of the coating material is calculated, and the coating material with a stable surface structure is screened as the interface system of the coating material.
  • the electrode active materials and coating materials that are easy to combine are preliminarily screened.
  • the formation energy of the electrode active material and the coating material is further calculated, and the coating material with a stable structure after being combined with the electrode active material is screened to determine the formation energy system of the coating material, that is, to construct the stability of the coating material database. Then, for the materials in the formation energy system of the coating material, the migration efficiency of lithium ions is calculated respectively, and the coating material with high lithium ion migration efficiency is screened; at the same time, the reaction between the material and the electrolyte in the formation energy system of the coating material is calculated The reaction kinetic parameters such as potential barrier and reaction thermodynamics are used to screen the cladding material with low reactivity with the electrolyte.
  • the electrode coating material screening method of this application constructs a data screening model from the interface microstructure level. Through high-throughput calculations, the best coating material on the surface of the electrode active material can be quickly and accurately screened, thereby accurately modifying the electrode active material. interface, improve the electrochemical performance of electrode active materials, and lay a good foundation for improving the performance of secondary batteries.
  • the electrode material provided by the second aspect of the present application has a core-shell structure, and its coating material is screened by the above method, so that the electrode material not only has a higher capacity, but also has good structural stability during the cycle charge and discharge process , low reactivity with the electrolyte, less side reactions, and long cycle life.
  • the secondary battery provided by the third aspect of the present application contains the above-mentioned electrode material, and the electrode material has a relatively high capacity, and in the cycle charging and discharging process, the electrode material has good structural stability, low reactivity with the electrolyte, and side effects. Less reaction; thereby improving the comprehensive electrochemical performance of the secondary battery such as energy density, cycle stability, and cycle life.
  • Fig. 1 is a schematic flow chart of the electrode coating material screening method provided in the embodiment of the present application.
  • the term "and/or” describes the association relationship of associated objects, indicating that there may be three relationships, for example, A and/or B may mean: A exists alone, A and B exist simultaneously, and B exists alone Condition. Among them, A and B can be singular or plural.
  • the character "/" generally indicates that the contextual objects are an "or" relationship.
  • At least one means one or more, and “multiple” means two or more.
  • At least one of the following” or similar expressions refer to any combination of these items, including any combination of single or plural items.
  • at least one (one) of a, b or c or “at least one (one) of a, b and c” can mean: a, b, c, a-b (that is, a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple.
  • sequence numbers of the above-mentioned processes do not mean the order of execution, and some or all steps may be executed in parallel or sequentially, and the execution order of each process shall be based on its functions and The internal logic is determined and should not constitute any limitation to the implementation process of the embodiment of the present application.
  • the weight of the relevant components mentioned in the description of the embodiments of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the various components.
  • the scaling up or down of the content of the fraction is within the scope disclosed in the description of the embodiments of the present application.
  • the mass in the description of the embodiments of the present application may be ⁇ g, mg, g, kg and other well-known mass units in the chemical industry.
  • first and second are only used for descriptive purposes to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features.
  • first XX can also be called the second XX
  • second XX can also be called the first XX.
  • a feature defined as “first” and “second” may explicitly or implicitly include one or more of these features.
  • the first aspect of the embodiment of the present application provides a method for screening electrode coating materials, including the following steps:
  • the migration rate of lithium ions is calculated by density functional theory, and the migration system of the coating material is determined;
  • the electrode coating material is obtained by screening.
  • the electrode coating material screening method provided in the first aspect of the embodiment of the present application calculates the surface energy of different crystal planes of the electrode active material through density functional theory, investigates the stability of the surface structure of the electrode active material, and uses the crystal plane with stable surface structure As the interface structure of the electrode active material; at the same time, calculate the surface energy of the coating material, and screen the coating material with stable surface structure as the interface system of the coating material. By calculating the surface energy separately, the electrode active materials and coating materials that are easy to combine are preliminarily screened.
  • the formation energy of the electrode active material and the coating material is further calculated, and the coating material with a stable structure after being combined with the electrode active material is screened to determine the formation energy system of the coating material, that is, to construct the stability of the coating material database. Then, for the materials in the formation energy system of the coating material, the migration efficiency of lithium ions is calculated respectively, and the coating material with high lithium ion migration efficiency is screened; at the same time, the reaction between the material and the electrolyte in the formation energy system of the coating material is calculated The reaction kinetic parameters such as potential barrier and reaction thermodynamics are used to screen the cladding material with low reactivity with the electrolyte.
  • the electrode coating material screening method in the embodiment of this application starts from the interface microstructure level to build a data screening model. Through high-throughput calculations, the best coating material on the surface of the electrode active material can be quickly and accurately screened, thereby accurately modifying the electrode.
  • the active material interface improves the electrochemical performance of the electrode active material and lays a good foundation for improving the performance of the secondary battery.
  • the electrode active material can be either a positive electrode active material or a negative electrode active material
  • the electrode coating material screening method in the embodiment of the present application is applicable to any electrode active material that needs to be coated. It is especially suitable for highly active positive electrode materials, such as ternary positive electrode materials. These high active positive electrode materials are prone to problems such as dissolution of transition metals, side reactions with electrolytes, and formation of lithium dendrites during battery cycle charge and discharge.
  • the electrode coating material screening method of the application example can quickly, accurately and efficiently screen out the best coating materials for highly active cathode materials such as ternary cathode materials.
  • the stability of the surface structure of the electrode active material is investigated by calculating the surface energy of different crystal planes of the electrode active material.
  • the coating materials are combined to form a stable core-shell structure composite electrode material.
  • the step of determining the interface structure of the electrode active material includes: screening the surface energy lower than The crystal face serves as the interface structure of the electrode active material.
  • crystal planes with low surface energy are selected as the interface structure of the electrode active material. The selected crystal planes are large and have good stability of the surface structure, which is favorable for combining with the coating material.
  • the coating material corresponds to the electrode active material. If the electrode active material is selected from the positive electrode active material, the coating material is selected from the positive electrode coating material matching the positive electrode active material; The material is selected from the negative electrode active material, and the coating material is selected from the negative electrode coating material matching the negative electrode active material.
  • the positive electrode active material is selected from at least one of: nickel-cobalt lithium manganate ternary material, lithium cobaltate, lithium iron phosphate, lithium manganate, and lithium nickel-cobalt aluminate.
  • the positive electrode coating material includes at least one of LiTaO 3 , Li 3 PO 4 , LiNbO 3 , Li 2 TiO 2 , Li 2 ZrO 3 , and Li 2 SiO 3 .
  • the structure stability of different coating materials is investigated by calculating the surface energy of different coating materials. Shell-structured composite electrode materials.
  • the step of determining the interface system of the coating material includes: screening the surface energy lower than As the interface system of the coating material, the coating material with low surface energy has better structural stability and better combination stability with the electrode active material.
  • the step of calculating the formation energy of the electrode active material and the coating material includes: selecting the electrode active material and the coating material based on the interface structure of the electrode active material and the interface system of the coating material,
  • DFT density functional theory
  • the surface energies of the electrode active material and the coating material are calculated separately, and the crystal planes of the electrode active material and the coating material that are easy to combine are preliminarily screened out, and the formation energy of the electrode active material and the coating material are further calculated. , taking the size of the interface formation energy as a variable, the lower the formation energy, the easier the combination of the electrode active material and the coating material, and the higher the structural stability. Large-capacity cladding materials, and further screening of cladding materials to construct the formation energy system of cladding materials.
  • the step of determining the formation energy system of the cladding material includes: screening the cladding material whose surface formation energy is lower than 0.8eV as the formation energy system of the cladding material, and the cladding material with the formation energy size is related to the electrode activity
  • the materials are easier to combine and the structural stability is better.
  • the step of calculating the lithium ion migration rate includes:
  • E a E transition state - E initial state E a , where E transition state is the energy corresponding to the transition state structure, and E initial state is the energy of the system structure where lithium ions are not intercalated into the active material;
  • the cladding material with high lithium ion migration efficiency and low migration barrier can be determined to determine the migration system of the cladding material.
  • the thermodynamics of the entire process of lithium ion migration from the shell surface of the cladding material to the core of the electrode active material can also be investigated.
  • the step of determining the migration system of the cladding material includes: screening a cladding material whose lithium ion migration energy barrier is not higher than 0.4eV as the migration system of the cladding material, that is, the cladding material in the migration system of the cladding material
  • the lithium ion migration barrier of the material is ⁇ 0.4eV, and the low migration energy barrier corresponds to the high migration efficiency of lithium ions. Therefore, the coating material not higher than 0.4eV ensures a high migration efficiency of lithium ions.
  • the coating material screened in the embodiment of the present application has high lithium ion migration efficiency and low migration barrier.
  • the reaction barrier and reaction thermodynamics between the coating material and the electrolyte are calculated by density functional theory.
  • the step of determining the reaction kinetic system of the coating material includes: screening the coating material whose reaction barrier with the electrolyte is not lower than 0.7eV, and whose reaction thermodynamics with the electrolyte is greater than 0eV, as the reaction of the coating material dynamic system.
  • the coating material screened in the embodiment of the present application has low electrolyte reactivity and good stability.
  • the step of screening the electrode coating material includes: selecting a coating material that satisfies both the migration system of the coating material and the reaction kinetic system of the coating material as the electrode coating material.
  • a highly stable electrode coating material with little impact on lithium intercalation kinetics and low reactivity of the interfacial electrolyte was finally screened out.
  • the cladding material with higher stability that is, a smaller forming energy
  • the embodiment of the present application further studied the lithium intercalation kinetics and the electrolyte reaction kinetics on the basis of the coating interface, and the screening can satisfy the influence on the lithium intercalation kinetics at the same time.
  • Coating materials with small and low interface electrolyte reactivity can realize accurate screening of coating structures and coating materials, so that the electrode active material/coating material core-shell structure composite electrode material has the best comprehensive electrochemical performance.
  • the second aspect of the embodiment of the present application provides an electrode material.
  • the electrode material is a core-shell structure, including an electrode active material inner core and a shell layer coated on the outer surface of the inner core.
  • the electrode coating material of the shell layer is composed of the above-mentioned electrode coating material Screened by the screening method.
  • the electrode material provided in the second aspect of the embodiment of the present application has a core-shell structure, and its coating material is screened by the method of the above embodiment, so that the electrode material not only has a higher capacity, but also has a high capacity during the cycle charge and discharge process. Good structural stability, low reactivity with electrolyte, less side reactions, and long cycle life.
  • the third aspect of the embodiment of the present application provides a secondary battery, including the above-mentioned electrode material.
  • the secondary battery provided by the third aspect of the embodiment of the present application contains the above-mentioned electrode material, the electrode material has a relatively high capacity, and in the process of cycle charging and discharging, the electrode material has good structural stability and low reactivity with the electrolyte , fewer side reactions; thereby improving the energy density, cycle stability, cycle life and other electrochemical comprehensive performance of the secondary battery.
  • a method for screening electrode coating materials comprising the steps of:
  • cladding materials such as LiTaO 3 , Li 3 PO 4 , LiNbO 3 , Li 2 TiO 2 , Li 2 ZrO 3 , Li 2 SiO 3 , etc., and construct different surfaces of cladding materials such as (100), (012) and (110) crystal planes, calculate the size of the surface energy, and screen the surface energy as The material LiNbO 3 (012) surface and surface energy are The surface of the material Li 3 PO 4 (100) is used to construct the interface system database of cladding materials.
  • ⁇ 2 (E' slab -N'.E' bulk )/2A' to calculate the surface energy ⁇ 2 of different cladding materials;
  • E' slab is the surface system of cladding materials Energy
  • E' bulk is the bulk structure energy of the coating material
  • N' is the atomic number of the surface system of the coating material
  • A' is the surface area of the surface system of the coating material.
  • E f E(cathode
  • shell), E(cathode) and E(shell) can be obtained by calculating the cathode
  • DFT density functional theory
  • thermodynamic changes final state energy-initial state energy
  • migration energy barrier changes transition state energy-initial state energy
  • the energy of the final state and the energy of the initial state are the energies of the architecture after lithium ion intercalation and non-intercalation in the positive electrode material, respectively, which can be obtained by DFT calculation of the corresponding architecture.
  • the transition state can be obtained by the Nudged elastic band (NEB) method.
  • the interface electrolyte reaction is studied. Calculate the reactivity of different coating materials with the electrolyte and solvent of the pre-assembled battery system, including the reaction thermodynamic changes and energy barrier changes, and screen out the coating material LiNbO 3 that is inert to the electrolyte reaction of the pre-assembled battery system as the coating material. Reaction kinetic system.
  • a kind of electrode material will screen out LiNbO 3 cladding material and NCM811 anode material are made core-shell structure composite electrode material, and its preparation method is:
  • a kind of lithium ion battery, its assembly step comprises:
  • a kind of lithium ion battery its preparation comprises the steps: take by weighing 0.5g nickel-cobalt-manganese NCM811 ternary positive electrode material, 0.1g carbon black conductive agent, 0.1g polyvinylidene fluoride binding agent, evenly coat on copper foil, obtain Positive sheet.
  • the diaphragm is made of PE film
  • the counter electrode is made of lithium metal sheet
  • a lithium ion battery the preparation of which comprises the steps of: weighing 0.5g of lithium phosphate-coated nickel-cobalt-manganese NCM811/Li 3 PO 4 composite ternary positive electrode material, 0.1g of carbon black conductive agent, and 0.1g of polyvinylidene fluoride binder , evenly coated on the copper foil to obtain a positive electrode sheet.
  • the diaphragm is made of PE film
  • the counter electrode is made of lithium metal sheet
  • Example 1 the lithium-ion batteries prepared in Example 1 and Comparative Example 1 were subjected to a cycle charge and discharge performance test under the conditions of a voltage range of 2 to 4.2V and a rate of 0.1C, and the test results As shown in Table 1 below:
  • the NCM811/ LiNbO3 composite positive electrode material obtained after screening the coating material by the electrode coating material screening method of Example 1 of the embodiment of the present application shows greater stability in cycle stability.

Abstract

本申请属于电池技术领域，尤其涉及一种电极包覆材料筛选方法，以及一种电极材料，一种二次电池。其中，电极包覆材料筛选方法，包括步骤：确定电极活性材料的界面结构；确定包覆材料的界面体系；基于电极活性材料的界面结构和包覆材料的界面体系，确定包覆材料的形成能体系；基于包覆材料的形成能体系，分别确定包覆材料的迁移体系和确定包覆材料的反应动力学体系；再基于包覆材料的迁移体系和包覆材料的反应动力学体系，筛选得到电极包覆材料。本申请电极包覆材料筛选方法，从界面微结构水平出发构建数据筛选模型，可快速精准的筛选出电极活性材料表面的最佳包覆材料，从而精准改性电极活性材料界面，提高电极活性材料的电化学性能。

Description

电极包覆材料筛选方法、电极材料、二次电池 技术领域
本申请属于电池技术领域，尤其涉及一种电极包覆材料筛选方法，以及一种电极材料，一种二次电池。
背景技术
随着新能源汽车的战略部署和推广，开发能量密度更高、价格更经济且寿命更长的新型锂离子电池便成为了我国电化学储能领域的重点研究内容。由于在二次电池中，正极是输运离子的供体，同时也决定了电池的能量密度和综合电化学性能。开发高能量密度锂离子电池正极材料便成为了学术界和工业界的研究热点。其中高镍三元正极材料因高电压和高能量密度等优异性质备受关注，产品也得到了系列开发。尽管三元正极材料拥有出色的电化学性能，然而在电池使役过程中，锂离子电池正极材料会存在一定的容量衰减，主要原因包括正极/电解液界面副反应、锂枝晶形成等。
为了提高电池的循环寿命和安全性，研究者们相继提出了正极表面包覆以及界面掺杂。目前有效的方法是在正极材料表面包覆一层物质，避免正极表面和电解液的直接接触，或进行表面元素掺杂钝化表面高活性位点，抑制与界面电解液的化学反应。如LiNi 0.50Mn 0.30Ni 0.20O 2(NCM532)表面包覆Li 2TiO 2岩盐结构氧化物，能够很好地附着在NCM532表面，抑制正极/电解液界面反应；NCM71515正极表面包覆Li 2ZrO 3能有效保护正极结构并促进锂离子输运等。然而，目前正极表面包覆材料仍停留在“试错”阶段，选择一种正极包覆材料并制备正极包覆材料核壳结构后，需组装成全电池进行电化学性质测试，验证包覆材料的效果，该类实验方法效率低下，程序繁琐，如何精准预测包覆材料实现筛选是急需解决的技术问题。
发明内容
本申请的目的在于提供一种电极包覆材料筛选方法，以及一种电极材料，一种二次电池，旨在一定程度上解决电极包覆材料的筛选方法需要组装成全电池进行电化学性能测试来验证包覆材料的效果，效率低，程序繁琐的问题。
为实现上述申请目的，本申请采用的技术方案如下：
第一方面，本申请提供电极包覆材料筛选方法，包括以下步骤：
获取电极活性材料，通过密度泛函理论计算所述电极活性材料不同晶面的表面能，确定电极活性材料的界面结构；
获取包覆材料，通过密度泛函理论计算所述包覆材料的表面能，确定包覆材料的界面体系；
基于所述电极活性材料的界面结构和所述包覆材料的界面体系，计算电极活性材料与包覆材料的形成能，确定包覆材料的形成能体系；
基于所述包覆材料的形成能体系，通过密度泛函理论计算锂离子迁移速率，确定包覆材料的迁移体系；
基于所述包覆材料的形成能体系，通过密度泛函理论计算包覆材料与电解液的反应势垒和反应热力学，确定包覆材料的反应动力学体系；
基于所述包覆材料的迁移体系和所述包覆材料的反应动力学体系，筛选得到电极包覆材料。
第二方面，本申请提供一种电极材料，所述电极材料为核壳结构，包括电极活性材料内核和包覆在所述内核外表面的壳层，所述壳层的电极包覆材料由上述的电极包覆材料筛选方法筛选得到。
第三方面，本申请提供一种二次电池，其特征在于，所述二次电池包含有上述的电极材料。
本申请第一方面提供的电极包覆材料筛选方法，通过密度泛函理论计算电极活性材料不同晶面的表面能大小，考察电极活性材料表面结构的稳定性，以 表面结构稳定的晶面作为电极活性材料的界面结构；同时计算包覆材料的表面能大小，筛选表面结构稳定的包覆材料作为包覆材料的界面体系。通过分别计算表面能，初步筛选易于结合的电极活性材料与包覆材料。再基于表面能筛选的材料进一步计算电极活性材料与包覆材料的形成能，筛选与电极活性材料复合后结构稳定的包覆材料，确定包覆材料的形成能体系，即构建包覆材料稳定性数据库。然后，针对包覆材料的形成能体系中材料，分别计算锂离子的迁移效率，筛选锂离子迁移效率高的包覆层材料；同时，计算包覆材料的形成能体系中材料与电解液的反应势垒和反应热力学等反应动力学参数，筛选与电解液反应活性低的包覆层材料。最后，基于所述包覆材料的迁移体系和所述包覆材料的反应动力学体系，筛选锂离子迁移效率高且与电解液反应活性低的包覆材料作为电极包覆材料，有利于获得综合性能优异的电极材料。本申请电极包覆材料筛选方法，从界面微结构水平出发构建数据筛选模型，通过高通量计算，可快速精准的筛选出电极活性材料表面的最佳包覆材料，从而精准改性电极活性材料界面，提高电极活性材料的电化学性能，为提高二次电池性能打下良好基础。
本申请第二方面提供的电极材料，具有核壳结构，其包覆材料通过上述方法筛选得到，因而使得电极材料不但具有较高的容量，且在循环充放电过程中，电极材料结构稳定性好，与电解液反应活性低，副反应少，循环寿命长。
本申请第三方面提供的二次电池，由于包含有上述电极材料，该电极材料具有较高的容量，且在循环充放电过程中，电极材料结构稳定性好，与电解液反应活性低，副反应少；从而提高了二次电池能量密度，循环稳定性，循环寿命等电化学综合性能。
附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅 仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是本申请实施例提供的电极包覆材料筛选方法的流程示意图。
具体实施方式
为了使本申请要解决的技术问题、技术方案及有益效果更加清楚明白，以下结合实施例，对本申请进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本申请，并不用于限定本申请。
本申请中，术语“和/或”，描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B的情况。其中A，B可以是单数或者复数。字符“/”一般表示前后关联对象是一种“或”的关系。
本申请中，“至少一个”是指一个或者多个，“多个”是指两个或两个以上。“以下至少一项(个)”或其类似表达，是指的这些项中的任意组合，包括单项(个)或复数项(个)的任意组合。例如，“a，b或c中的至少一项(个)”，或，“a，b和c中的至少一项(个)”，均可以表示：a，b，c，a-b(即a和b)，a-c，b-c，或a-b-c，其中a，b，c分别可以是单个，也可以是多个。
应理解，在本申请的各种实施例中，上述各过程的序号的大小并不意味着执行顺序的先后，部分或全部步骤可以并行执行或先后执行，各过程的执行顺序应以其功能和内在逻辑确定，而不应对本申请实施例的实施过程构成任何限定。
在本申请实施例中使用的术语是仅仅出于描述特定实施例的目的，而非旨在限制本申请。在本申请实施例和所附权利要求书中所使用的单数形式的“一种”和“该”也旨在包括多数形式，除非上下文清楚地表示其他含义。
本申请实施例说明书中所提到的相关成分的重量不仅仅可以指代各组分的具体含量，也可以表示各组分间重量的比例关系，因此，只要是按照本申请实 施例说明书相关组分的含量按比例放大或缩小均在本申请实施例说明书公开的范围之内。具体地，本申请实施例说明书中的质量可以是μg、mg、g、kg等化工领域公知的质量单位。
术语“第一”、“第二”仅用于描述目的，用来将目的如物质彼此区分开，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。例如，在不脱离本申请实施例范围的情况下，第一XX也可以被称为第二XX，类似地，第二XX也可以被称为第一XX。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括一个或者更多个该特征。
本申请实施例第一方面提供一种电极包覆材料筛选方法，包括以下步骤：
S10.获取电极活性材料，通过密度泛函理论计算电极活性材料不同晶面的表面能，确定电极活性材料的界面结构；
S20.获取包覆材料，通过密度泛函理论计算包覆材料的表面能，确定包覆材料的界面体系；
S30.基于电极活性材料的界面结构和包覆材料的界面体系，计算电极活性材料与包覆材料的形成能，确定包覆材料的形成能体系；
S40.基于包覆材料的形成能体系，通过密度泛函理论计算锂离子迁移速率，确定包覆材料的迁移体系；
S50.基于包覆材料的形成能体系，通过密度泛函理论计算包覆材料与电解液的反应势垒和反应热力学，确定包覆材料的反应动力学体系；
S60.基于包覆材料的迁移体系和包覆材料的反应动力学体系，筛选得到电极包覆材料。
本申请实施例第一方面提供的电极包覆材料筛选方法，通过密度泛函理论计算电极活性材料不同晶面的表面能大小，考察电极活性材料表面结构的稳定性，以表面结构稳定的晶面作为电极活性材料的界面结构；同时计算包覆材料的表面能大小，筛选表面结构稳定的包覆材料作为包覆材料的界面体系。通过分别计算表面能，初步筛选易于结合的电极活性材料与包覆材料。再基于表面 能筛选的材料进一步计算电极活性材料与包覆材料的形成能，筛选与电极活性材料复合后结构稳定的包覆材料，确定包覆材料的形成能体系，即构建包覆材料稳定性数据库。然后，针对包覆材料的形成能体系中材料，分别计算锂离子的迁移效率，筛选锂离子迁移效率高的包覆层材料；同时，计算包覆材料的形成能体系中材料与电解液的反应势垒和反应热力学等反应动力学参数，筛选与电解液反应活性低的包覆层材料。最后，基于包覆材料的迁移体系和包覆材料的反应动力学体系，筛选锂离子迁移效率高且与电解液反应活性低的包覆材料作为电极包覆材料，有利于获得综合性能优异的电极材料。本申请实施例电极包覆材料筛选方法，从界面微结构水平出发构建数据筛选模型，通过高通量计算，可快速精准的筛选出电极活性材料表面的最佳包覆材料，从而精准改性电极活性材料界面，提高电极活性材料的电化学性能，为提高二次电池性能打下良好基础。
在一些实施例中，上述步骤S10中，电极活性材料既可以是正极活性材料，也可以是负极活性材料，本申请实施例电极包覆材料筛选方法适应于需要进行包覆的任意电极活性材料。尤其适用于高活性正极材料，如三元正极材料等，这些高活性正极材料在电池循环充放电过程中，容易出现过渡金属溶解、与电解液发生副反应、形成锂枝晶等问题，通过本申请实施例电极包覆材料筛选方法可快速精准高效的筛选出三元正极材料等高活性正极材料的最佳包覆材料。
在一些实施例中，计算电极活性材料不同晶面的表面能的步骤包括：对电极活性材料进行切面处理，构建不同晶面，通过公式：γ 1＝(E slab-N.E bulk)/2A计算不同晶面的表面能γ 1；其中，E slab是电极活性材料表面体系能量，E bulk是电极活性材料体相结构能量，N为电极活性材料表面体系原子数，A为电极活性材料表面体系表面面积。本申请实施例通过计算电极活性材料不同晶面的表面能大小，考察电极活性材料表面结构的稳定性，表面能越小，则对应晶面越大，构建的表面结构越稳定，越有利于与包覆材料结合形成性能稳定的核壳结构复合电极材料。
在一些实施例中，确定电极活性材料的界面结构的步骤包括：筛选表面能低于
Figure PCTCN2021137618-appb-000001
的晶面作为电极活性材料的界面结构。本申请实施例筛选低表面能的晶面作为电极活性材料的界面结构，所选晶面大，表面结构稳定性好，有利于与包覆材料结合。
在一些实施例中，上述步骤S20中，包覆材料与电极活性材料对应，若电极活性材料选自正极活性材料，则包覆材料选自与正极活性材料匹配的正极包覆材料；若电极活性材料选自负极活性材料，则包覆材料选自于与负极活性材料匹配的负极包覆材料。
在一些实施例中，正极活性材料选自：镍钴锰酸锂三元材料、钴酸锂、磷酸铁锂、锰酸锂、镍钴铝酸锂中的至少一种。此时，正极包覆材料包括：LiTaO 3、Li 3PO 4、LiNbO 3、Li 2TiO 2、Li 2ZrO 3、Li 2SiO 3中的至少一种。
在一些实施例中，计算包覆材料的表面能的步骤包括：获取不同的包覆材料后进行切面处理，构建不同米勒指数表面，通过公式：γ 2＝(E' slab-N'.E' bulk)/2A'计算不同包覆材料的表面能γ 2；其中，E’ slab是包覆材料表面体系能量，E’ bulk是包覆材料体相结构能量，N’为包覆材料表面体系原子数，A’为包覆材料表面体系表面面积。本申请实施例通过对不同包覆材料的表面能大小进行计算，考察不同包覆材料的结构稳定性，表面能越小，表面结构越稳定，越有利于与电极活性材料结合形成性能稳定的核壳结构复合电极材料。
在一些实施例中，确定包覆材料的界面体系的步骤包括：筛选表面能低于
Figure PCTCN2021137618-appb-000002
的包覆材料作为包覆材料的界面体系，低表面能的包覆材料结构稳定性更好，与电极活性材料有更好的结合稳定性。
在一些实施例中，上述步骤S30中，计算电极活性材料与包覆材料的形成能的步骤包括：基于电极活性材料的界面结构和包覆材料的界面体系，选取电极活性材料和包覆材料，通过公式：E f＝E(Electrode|shell)-E(Electrode)-E(shell)计算选取的电极活性材料与包覆材料之间的结构形成能E f；其中，E(Electrode|shell)为电极活性材料和包覆材料形成核壳结构的表面体系能量， E(Electrode)为电极活性材料形成电极的表面体系能量，E(shell)为包覆材料形成壳层的表面体系能量，E(Electrode|shell)、E(Electrode)、E(shell)分别可通过密度泛函理论(DFT)计算。本申请实施例通过分别计算分别计算电极活性材料与包覆材料的表面能，初步筛选出易于结合的电极活性材料晶面以及包覆材料后，进一步计算电极活性材料和包覆材料的形成能大小，以界面形成能的大小作为变量，形成能越低电极活性材料和包覆材料越容易结合，且结构稳定性越高，从而筛选出与电极活性材料形成能低的包覆材料，筛除形成能大的包覆材料，对包覆材料通过进一步筛选构建包覆材料的形成能体系。
在一些实施例中，确定包覆材料的形成能体系的步骤包括：筛选表面形成能低于0.8eV的包覆材料作为包覆材料的形成能体系，该形成能大小的包覆材料与电极活性材料更容易结合，结构稳定性更好。
在一些实施例中，上述步骤S40中，计算锂离子迁移速率的步骤包括：
S41.从包覆材料的形成能体系中选取包覆材料，通过公式：E a＝E 过渡态-E 初始 态计算锂离子从包覆材料的壳层迁移至活性材料的内核中的迁移能垒E a，其中，E 过渡态为过渡态结构对应能量，E 初始态为锂离子未嵌入活性材料的体系结构能量；
S42.通过公式：r＝A”exp(-E a/kT)计算锂离子迁移速率r；其中，A”为置前因子，E a为迁移能垒，k为玻尔兹曼常数，T为温度。
本申请实施例进一步从包覆材料的形成能体系中选取包覆材料，考察锂离子从包覆材料壳层表面迁移至电极活性材料内核中的整个过程的迁移能垒变化E a(E a＝E 过渡态-E 初始态)，再通过r＝A”exp(-E a/kT)计算锂离子迁移效率，研究包覆材料的形成能体系中不同包覆材料的嵌锂动力学，进一步筛选出锂离子迁移效率高，迁移势垒低的包材料，确定包覆材料的迁移体系。另外，还可以通过考察锂离子从包覆材料壳层表面迁移至电极活性材料内核中的整个过程的热力学变化E b(E b＝E 末态-E 初始态)，通过热力学变化从热力学上考察该锂离子迁移过程是否热力学有利，热力学变化E b值越负，则越有利于锂离子迁移。本申请E 末态、E 初始态通过密度泛函理论DFT计算相应体系结构获取，E 过渡态-E 初始态可通过 轻推弹力带Nudged elastic band(NEB)方法获取。
在一些实施例中，确定包覆材料的迁移体系的步骤包括：筛选锂离子迁移能垒不高于0.4eV的包覆材料作为包覆材料的迁移体系，即包覆材料的迁移体系中包覆材料的锂离子迁移势垒<0.4eV，迁移能垒低对应锂离子迁移效率高，因而不高于0.4eV的包覆材料确保了锂离子具有较高的迁移效率。本申请实施例筛选的包覆材料锂离子迁移效率高，迁移势垒低。
在一些实施例中，上述步骤S50中，基于包覆材料的形成能体系，通过密度泛函理论计算包覆材料与电解液的反应势垒和反应热力学，反应势垒越大，热力学越正，包覆材料与电解液的反应越惰性，则包覆材料与电极活性材料形成的复合电极材料在电池循环充放电过程中越稳定。
在一些实施例中，确定包覆材料的反应动力学体系的步骤包括：筛选与电解液反应势垒不低于0.7eV，且与电解液反应热力学大于0eV的包覆材料作为包覆材料的反应动力学体系。本申请实施例筛选的包覆材料越电解液反应活性低，稳定性好。
在一些实施例中，上述步骤S60中，筛选电极包覆材料的步骤包括：选取同时满足包覆材料的迁移体系和包覆材料的反应动力学体系的包覆材料作为电极包覆材料。本申请实施例基于包覆材料的迁移体系和包覆材料的反应动力学体系，最终筛选出对嵌锂动力学影响小且界面电解液反应活性低的高稳定电极包覆材料。
本申请实施例通过上述实施例步筛选出稳定性较高即形成能较小的包覆材料，与电极活性材料容易结合且结合稳定好，有利于初步确定电极活性材料/包覆材料复合稳定结构。为进一步确保核壳结构复合电极材料的综合电化学性能，本申请实施例在包覆界面的基础上进一步研究了嵌锂动力学和电解液反应动力学，筛选能同时满足对嵌锂动力学影响小和界面电解液反应活性低的包覆材料，实现对包覆结构及包覆材料的精确筛选，从而使电极活性材料/包覆材料核壳结构复合电极材料有最佳的电化学综合性能。
本申请实施例第二方面提供一种电极材料，电极材料为核壳结构，包括电极活性材料内核和包覆在内核外表面的壳层，壳层的电极包覆材料由上述的电极包覆材料筛选方法筛选得到。
本申请实施例第二方面提供的电极材料，具有核壳结构，其包覆材料通过上述实施例方法筛选得到，因而使得电极材料不但具有较高的容量，且在循环充放电过程中，电极材料结构稳定性好，与电解液反应活性低，副反应少，循环寿命长。
本申请实施例第三方面提供一种二次电池，包含有上述的电极材料。
本申请实施例第三方面提供的二次电池，由于包含有上述电极材料，该电极材料具有较高的容量，且在循环充放电过程中，电极材料结构稳定性好，与电解液反应活性低，副反应少；从而提高了二次电池能量密度，循环稳定性，循环寿命等电化学综合性能。
为使本申请上述实施细节和操作能清楚地被本领域技术人员理解，以及本申请实施例电极包覆材料筛选方法、电极材料和二次电池的进步性能显著的体现，以下通过多个实施例来举例说明上述技术方案。
实施例1
一种电极包覆材料筛选方法，包括步骤：
①构建NCM811正极不同表面(100)、(001)、(110)、(104)等晶面，计算各晶面表面能大小，筛选出表面能为0.49eV的(104)晶面作为NCM811正极材料的界面结构。表面能(γ 1)计算公式如下：γ 1＝(E slab-N.E bulk)/2A计算不同晶面的表面能γ 1；其中，E slab是NCM811正极材料表面体系能量，E bulk是NCM811正极材料体相结构能量，N为NCM811正极材料表面体系原子数，A为NCM811正极材料表面体系表面面积。
②系统选择系列包覆材料，如LiTaO 3、Li 3PO 4、LiNbO 3、Li 2TiO 2、Li 2ZrO 3、Li 2SiO 3等，构建包覆材料不同表面如(100)、(012)和(110)等晶面，计 算表面能大小，筛选表面能为
Figure PCTCN2021137618-appb-000003
的材料LiNbO 3(012)表面和表面能为
Figure PCTCN2021137618-appb-000004
的材料Li 3PO 4(100)表面，构建的包覆材料的界面体系数据库。表面能(γ 2)计算公式如下：γ 2＝(E' slab-N'.E' bulk)/2A'计算不同包覆材料的表面能γ 2；其中，E’ slab是包覆材料表面体系能量，E’ bulk是包覆材料体相结构能量，N’为包覆材料表面体系原子数，A’为包覆材料表面体系表面面积。
③研究包覆材料和NCM811正极材料之间的包覆效果，计算包覆材料包覆正极后的结构形成能(E f＝E(cathode|shell)-E(cathode)-E(shell))。E(cathode|shell)、E(cathode)和E(shell)分别可通过密度泛函理论(DFT)计算cathode|shell核壳体系、正极表面体系和壳层表面体系获取。以界面形成能作为变量，筛选出形成能低于0.8eV的NCM811/LiNbO 3材料和NCM811/Li 3PO 4材料，构建包覆材料的形成能体系数据库。
④在筛选出的包覆材料的形成能体系数据库中，进行嵌锂理论研究。考察锂离子从壳层表面迁移至核层正极材料中的整个过程的热力学变化(末态能量-初始态能量)和迁移能垒变化(过渡态能量-初始态能量)。其中，末态能量和初始态能量分别为锂离子嵌入和未嵌入正极材料后的体系结构的能量，可通过DFT计算相应体系结构获取。过渡态可通过Nudged elastic band(NEB)方法获取。然后，基于Arrhenius公式：r＝A”exp(-E a/kT)计算不同包覆材料的锂离子迁移速率r；其中，A”为置前因子，E a为迁移能垒，k为玻尔兹曼常数，T为温度。筛选出迁移势垒低于0.4eV的LiNbO 3材料作为包覆材料的迁移体系。
⑤在筛选出的包覆材料的形成能体系数据库中，研究界面电解液反应。计算不同包覆材料与预组装电池体系的电解质和溶剂的反应活性，包括反应热力学变化和能垒变化，筛选出对预组装电池体系的电解液反应惰性的包覆材料LiNbO 3作为包覆材料的反应动力学体系。
⑥从步骤④包覆材料的迁移体系和⑤包覆材料的反应动力学体系中，筛选出同时满足包覆材料的迁移体系和包覆材料的反应动力学体系的包覆材料，即LiNbO 3材料，作为NCM811正极最佳的包覆材料。
一种电极材料，将筛选出的LiNbO 3包覆材料与NCM811正极材料制成核壳结构复合电极材料，其制备方法为：
①分别量取0.8moL的1moL/L的NiSO 4·6H 2O、0.1moL的CoSO 4·7H 2O、0.1moL的MnSO 4·H 2O(Ni:Co:Mn＝8:1:1)均匀混合，取5mol/L NaOH溶液和4mol/L的NH 3·H 2O溶液分别加入反应槽中，调节pH值为10，进行共沉淀反应。通过水洗涤、过滤和干燥后，获取Ni 0.8Co 0.1Mn 0.1(OH) 2前驱体。
②以Li：(Ni+Co+Mn)＝1:1的摩尔比，将锂源与Ni0.9Co0.05Mn0.05(OH)2前驱体在混料罐中进行均匀混合，时间为10小时，之后在氧气下进行两段烧结。首先在500℃下加热预处理5～10小时，然后在800℃下烧结15小时。通过自然冷却至90℃时拿出样品，得到三元正极材料LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)。
③称取0.6g Nb 2O 5与110g镍钴锰氧化物前驱体，分散到100g的乙醇和水混合液中(乙醇：水＝5：1)，转移至油浴锅中搅拌，设置搅拌转速300rpm，温度为90℃。等混合液蒸干，将产物放置匣砵中，转至箱式炉中，调节升温速度为10℃/分钟，达到500℃后放置8小时。之后，进行自然冷却至室温，得到铌酸锂包覆三元正极材料，即NCM811/LiNbO 3复合正极材料。
一种锂离子电池，其组装步骤包括：
称取0.5g铌酸锂包覆镍钴锰NCM811三元正极材料NCM811/LiNbO 3，0.1g碳黑导电剂，0.1g聚偏氟乙烯粘结剂，均匀涂覆在铜箔上，得到正极片。隔膜采用PE膜，对电极采用锂金属片，电解液为1M LiPF 6/(EC:DMC＝1:1)，在惰性气体手套箱中组装成纽扣电池，得到锂离子电池。
对比例1
一种锂离子电池，其制备包括步骤：称取0.5g镍钴锰NCM811三元正极材料，0.1g碳黑导电剂，0.1g聚偏氟乙烯粘结剂，均匀涂覆在铜箔上，得到正极片。隔膜采用PE膜，对电极采用锂金属片，电解液为1M LiPF 6/(EC:DMC＝1:1)，在惰性气体手套箱中组装成纽扣电池，得到锂离子电池。
对比例2
一种锂离子电池，其制备包括步骤：称取0.5g磷酸锂包覆镍钴锰NCM811/Li 3PO 4复合三元正极材料，0.1g碳黑导电剂，0.1g聚偏氟乙烯粘结剂，均匀涂覆在铜箔上，得到正极片。隔膜采用PE膜，对电极采用锂金属片，电解液为1M LiPF 6/(EC:DMC＝1:1)，在惰性气体手套箱中组装成纽扣电池，得到锂离子电池。
进一步的，为了验证本申请实施例的进步性，对实施例1和对比例1制备的锂离子电池在2～4.2V电压区间和0.1C倍率条件下，进行了循环充放电性能测试，测试结果如下表1所示：
表1
Figure PCTCN2021137618-appb-000005
由上述测试结果可知，通过本申请实施例实施例1电极包覆材料筛选方法筛选包覆材料后得到的NCM811/LiNbO 3复合正极材料，组装的锂离子电池在循环稳定性方面表现出更大的优势，而对比例1未包覆NCM811正极组装的锂离子电池，以及对比例2未经过筛选直接采用Li 3PO 4包覆的NCM811复合正极所组装的锂离子电池，容量保持率下降明显，循环稳定性差。
以上所述仅为本申请的较佳实施例而已，并不用以限制本申请，凡在本申请的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本申请的保护范围之内。

Claims (10)

  1. 一种电极包覆材料筛选方法，其特征在于，包括以下步骤：
    获取电极活性材料，通过密度泛函理论计算所述电极活性材料不同晶面的表面能，确定电极活性材料的界面结构；
    获取包覆材料，通过密度泛函理论计算所述包覆材料的表面能，确定包覆材料的界面体系；
    基于所述电极活性材料的界面结构和所述包覆材料的界面体系，计算电极活性材料与包覆材料的形成能，确定包覆材料的形成能体系；
    基于所述包覆材料的形成能体系，通过密度泛函理论计算锂离子迁移速率，确定包覆材料的迁移体系；
    基于所述包覆材料的形成能体系，通过密度泛函理论计算包覆材料与电解液的反应势垒和反应热力学，确定包覆材料的反应动力学体系；
    基于所述包覆材料的迁移体系和所述包覆材料的反应动力学体系，筛选得到电极包覆材料。
  2. 如权利要求1所述的电极包覆材料筛选方法，其特征在于，计算所述电极活性材料不同晶面的表面能的步骤包括：对所述电极活性材料进行切面处理，构建不同晶面，通过公式：γ 1＝(E slab-N.E bulk)/2A计算不同晶面的表面能γ 1；其中，E slab是电极活性材料表面体系能量，E bulk是电极活性材料体相结构能量，N为电极活性材料表面体系原子数，A为电极活性材料表面体系表面面积；
    和/或，确定所述电极活性材料的界面结构的步骤包括：筛选表面能低于
    Figure PCTCN2021137618-appb-100001
    Figure PCTCN2021137618-appb-100002
    的晶面作为所述电极活性材料的界面结构。
  3. 如权利要求1或2所述的电极包覆材料筛选方法，其特征在于，计算所述包覆材料的表面能的步骤包括：获取不同的所述包覆材料后进行切面处理，通过公式：γ 2＝(E' slab-N'.E' bulk)/2A'计算不同所述包覆材料的表面能γ 2；其中，E’ slab是包覆材料表面体系能量，E’ bulk是包覆材料体相结构能量，N’为包覆材料表面体系原子数，A’为包覆材料表面体系表面面积；
    和/或，确定所述包覆材料的界面体系的步骤包括：筛选表面能低于
    Figure PCTCN2021137618-appb-100003
    Figure PCTCN2021137618-appb-100004
    的包覆材料作为所述包覆材料的界面体系。
  4. 如权利要求3所述的电极包覆材料筛选方法，其特征在于，所述计算电极活性材料与包覆材料的形成能的步骤包括：基于所述电极活性材料的界面结构和所述包覆材料的界面体系，选取电极活性材料和包覆材料，通过公式：E f＝E(Electrode|shell)-E(Electrode)-E(shell)计算选取的所述电极活性材料与所述包覆材料之间的结构形成能E f；其中，E(Electrode|shell)为所述电极活性材料和所述包覆材料形成核壳结构的表面体系能量，E(Electrode)为所述电极活性材料形成电极的表面体系能量，E(shell)为所述包覆材料形成壳层的表面体系能量；
    和/或，确定所述包覆材料的形成能体系的步骤包括：筛选表面形成能低于0.8eV的包覆材料作为所述包覆材料的形成能体系。
  5. 如权利要求1或4所述的电极包覆材料筛选方法，其特征在于，所述计算锂离子迁移速率的步骤包括：从所述包覆材料的形成能体系中选取包覆材料，通过公式：E a＝E 过渡态-E 初始态计算锂离子从所述包覆材料的壳层迁移至所述活性材料的内核中的迁移能垒E a，其中，E 过渡态为过渡态结构能量，E 初始态为锂离子未嵌入活性材料的体系结构能量；
    通过公式：r＝A”exp(-E a/kT)计算锂离子迁移速率r；其中，A”为置前因子，E a为迁移能垒，k为玻尔兹曼常数，T为温度；
    和/或，确定所述包覆材料的迁移体系的步骤包括：筛选锂离子迁移能垒不高于0.4eV的包覆材料作为所述包覆材料的迁移体系。
  6. 如权利要求5所述的电极包覆材料筛选方法，其特征在于，确定所述包覆材料的反应动力学体系的步骤包括：筛选与电解液反应势垒不低于0.7eV，且与电解液反应热力学大于0eV的包覆材料作为所述包覆材料的反应动力学体系；
    和/或，筛选所述电极包覆材料的步骤包括：选取同时满足所述包覆材料的迁移体系和所述包覆材料的反应动力学体系的包覆材料作为所述电极包覆材料。
  7. 如权利要求1所述的电极包覆材料筛选方法，其特征在于，所述电极活性材料选自正极活性材料，所述包覆材料选自正极包覆材料；
    或者，所述电极活性材料选自负极活性材料，所述包覆材料选自负极包覆材料。
  8. 如权利要求7所述的电极包覆材料筛选方法，其特征在于，所述正极活性材料选自：镍钴锰酸锂三元材料、钴酸锂、磷酸铁锂、锰酸锂、镍钴铝酸锂中的至少一种；
    所述正极包覆材料包括：LiTaO 3、Li 3PO 4、LiNbO 3、Li 2TiO 2、Li 2ZrO 3、Li 2SiO 3中的至少一种。
  9. 一种电极材料，其特征在于，所述电极材料为核壳结构，包括电极活性材料内核和包覆在所述内核外表面的壳层，所述壳层的电极包覆材料由如权利要求1～8任一项所述的电极包覆材料筛选方法筛选得到。
  10. 一种二次电池，其特征在于，所述二次电池包含有如权利要求9所述的电极材料。
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