Multifunctional multi-region composite CEI film and preparation method and application thereof

Abstract

The application discloses a multifunctional multi-region composite CEI film and a preparation method and application thereof, relates to the technical field of lithium ion batteries, and solves the technical problems of structural instability and performance attenuation of current lithium ion battery positive electrode materials; the application comprises material A, material B and material C, the material A, the material B and the material C divide the CEI film into n regions, n is a positive integer greater than or equal to 3, the material A is selected from any one or more of LiF, Li2CO3, LiNbO3 and LiTaO3, the material B is selected from any one or more of Al2O3, Li2ZrO3 and LiAlO2, and the material C is selected from any one or more of Li3N, BaTiO3 and PbTiO3; the CEI film has good electrochemical stability, mechanical toughness, ion transport property and conductivity, is applied to lithium ion batteries, and significantly improves the comprehensive performance and reliability of the batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a multifunctional multi-region composite CEI thin film, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries, as one of the most mainstream energy storage devices, are widely used in portable electronic devices, electric vehicles, and large-scale energy storage systems. To meet the ever-increasing demand for energy density, researchers are constantly exploring methods to improve battery performance, with the improvement of cathode materials being a key approach. However, current lithium-ion battery cathode materials, such as the high-nickel ternary material NCM811, still face many challenges in practical applications.

[0003] First, cathode materials are prone to lattice contraction and expansion during charging and discharging, leading to structural instability. Cathode material particles may break down, and even irreversible phase transitions may occur, affecting the battery's cycle stability and safety. Furthermore, the CEI (Cathode-Electrolyte Interphase) interface formed between the cathode and electrolyte is typically unstable, easily breaking and disintegrating, leading to direct contact between the electrolyte and the cathode material and triggering side reactions. This direct contact easily causes electrolyte decomposition, producing gas and solid deposits, hindering Li-ion exchange. + Migration channels increase battery internal resistance, affecting battery performance and safety.

[0004] To address these challenges, several solutions have been proposed and applied: (1) Positive electrode doping: Stabilizing the positive electrode structure and improving electrochemical performance through cation or anion doping. (2) Surface coating technology: Effectively suppressing side reactions between the electrode and the electrolyte by depositing inert oxides or fluorides (such as Al2O3) on the surface of the positive electrode material. (3) Electrolyte additives: Adding film-forming additives to the electrolyte to form a stable CEI layer on the electrode surface through in-situ polymerization or decomposition, thereby improving the cycle stability and rate performance of the battery.

[0005] While the above methods have achieved some success, some problems still exist in practical applications. Although doping methods can improve the stability of the cathode structure, under high voltage, more Li... + It will peel off from the positive electrode, making it difficult to suppress oxygen precipitation and lattice distortion. Furthermore, doping may reduce reversible capacity and energy density. Electrolyte additives can improve CEI stability, but additive decomposition may form an excessively thick CEI film at high voltages, hindering Li... + Interfacial reactions can be caused by the migration of these substances, leading to increased battery polarization and reduced capacity retention. While artificially constructing modification layers on the electrode surface can effectively control interfacial reactions, this approach is typically limited to single-component materials, neglecting other battery performance requirements such as rate performance and cycle performance.

[0006] Based on the requirements of the positive electrode electrochemical environment, this invention designs a multi-component, multi-functional, and multi-regional artificial composite CEI film, which can not only effectively solve the limitations of existing methods, but also improve the overall performance and reliability of the battery. Summary of the Invention

[0007] This invention aims to address the technical problems of structural instability and performance degradation faced by current lithium-ion battery cathode materials. The purpose is to provide a multifunctional, multi-regional composite CEI thin film, its preparation method, and its application. This CEI thin film has good electrochemical stability, mechanical toughness, ion transport, and conductivity. When applied to lithium-ion batteries, it significantly improves the overall performance and reliability of the batteries.

[0008] This invention is achieved through the following technical solution:

[0009] The first objective of this invention is to provide a multifunctional multi-region composite CEI film, comprising material A, material B, and material C, wherein material A, material B, and material C divide the CEI film into n regions, where n is a positive integer ≥ 3;

[0010] Material A is selected from any one or more of LiF, Li2CO3, LiNbO3, and LiTaO3;

[0011] Material B is selected from any one or more of Al2O3, Li2ZrO3, and LiAlO2;

[0012] Material C is selected from any one or more of Li3N, BaTiO3, and PbTiO3.

[0013] Furthermore, the mass ratio of material A, material B and material C is 1:(0.5-2):(0.5-2).

[0014] Furthermore, the mass ratio of material A, material B and material C is 1:(1-1.5):(1-1.5).

[0015] Furthermore, the number of regions formed by materials A, B, and C on the CEI film is the same.

[0016] The second objective of this invention is to provide a method for preparing a multifunctional, multi-region composite CEI thin film, comprising the following steps:

[0017] Using a high-vacuum thermal evaporation system, materials A, B, and C are placed in their respective evaporation boats. The substrate to be coated is fixed on a rotating substrate support, and a porous baffle is placed to shield different material areas of the substrate.

[0018] In a high vacuum environment, start the evaporation source corresponding to any material, open the baffle hole of the material area to be coated for evaporation, and close the baffle hole corresponding to other material areas. Only repeat the operation to complete the regional coating of materials A, B and C.

[0019] After evaporation, the coated substrate is cooled and annealed to obtain a multifunctional, multi-region composite CEI film.

[0020] Furthermore, the cooling and annealing treatment of the coated substrate includes:

[0021] The coated substrate is cooled and gradually restored to normal pressure. The coated substrate is then removed and annealed at 300°C in an argon atmosphere for 2 hours.

[0022] Furthermore, during evaporation, materials A, B, and C use independent evaporation sources.

[0023] Furthermore, the substrate to be coated is in a rotating state during the evaporation process.

[0024] The third objective of this invention is to provide the application of the above-mentioned CEI film in positive electrode sheets and lithium-ion batteries, specifically:

[0025] A positive electrode is provided, the surface of which has a CEI film as described above.

[0026] A lithium-ion battery is provided, comprising a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode is the aforementioned positive electrode.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] 1. The CEI film of the present invention is composed of three materials. By designing and preparing a regional, multi-component, and multifunctional artificial CEI film, the structural instability and performance degradation problems faced by current lithium-ion battery cathode materials are solved to a certain extent.

[0029] 2. The CEI film of this invention possesses high electrochemical stability, mechanical toughness, and density, effectively suppressing volume changes in electrode materials and effectively blocking side reactions between the positive electrode material and the electrolyte, reducing electrolyte decomposition and by-product formation, lowering battery internal resistance, and improving battery performance and safety. Simultaneously, this CEI film exhibits high ion transport and conductivity, ensuring high rate capability and high energy density, and extending battery life. The multi-component composite CEI film of this invention demonstrates excellent overall performance, significantly improving the overall performance and reliability of the battery. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0031] Figure 1 A schematic diagram of the regional structure of the CEI film prepared for the example; Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments and accompanying drawings. Obviously, the illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0033] The following details embodiments of a multifunctional multi-region composite CEI film, its preparation method, and its applications according to the present invention. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art.

[0034] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. The range defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range.

[0035] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0036] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0037] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other substances not listed may also be included, or that only the listed substances may be included.

[0038] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0039] The technical solution of the present invention is to provide a multifunctional multi-region composite CEI film, comprising material A, material B and material C, wherein material A, material B and material C divide the CEI film into n regions, where n is a positive integer ≥3;

[0040] Material A is selected from any one or more of LiF, Li2CO3, LiNbO3, and LiTaO3;

[0041] Material B is selected from any one or more of Al2O3, Li2ZrO3, and LiAlO2;

[0042] Material C is selected from any one or more of Li3N, BaTiO3, and PbTiO3.

[0043] The CEI film of this invention is composed of three materials. By designing and preparing a regional, multi-component, and multifunctional artificial CEI film, the structural instability and performance degradation problems faced by current lithium-ion battery cathode materials are solved to a certain extent.

[0044] The CEI film of this invention possesses high electrochemical stability, mechanical toughness, and density, effectively suppressing volume changes in electrode materials and effectively blocking side reactions between the cathode material and the electrolyte, reducing electrolyte decomposition and by-product formation, lowering battery internal resistance, and improving battery performance and safety. Simultaneously, this CEI film exhibits high ion transport and conductivity, ensuring high rate capability and high energy density, and extending battery life. The multi-component composite CEI film of this invention demonstrates excellent overall performance, significantly improving the overall performance and reliability of the battery.

[0045] In a preferred embodiment, the mass ratio of material A, material B and material C is 1:(0.5-2):(0.5-2).

[0046] In a preferred embodiment, the mass ratio of material A, material B and material C is 1:(1-1.5):(1-1.5).

[0047] In a preferred embodiment, materials A, B, and C form the same number of regions on the CEI film.

[0048] The present invention also provides a method for preparing the above-mentioned CEI film, comprising the following steps:

[0049] Using a high-vacuum thermal evaporation system, materials A, B, and C are placed in their respective evaporation boats. The substrate to be coated is fixed on a rotating substrate support, and a porous baffle is placed to shield different material areas of the substrate.

[0050] In a high vacuum environment, start the evaporation source corresponding to any material, open the baffle hole of the material area to be coated for evaporation, and close the baffle hole corresponding to other material areas. Only repeat the operation to complete the regional coating of materials A, B and C.

[0051] After evaporation, the coated substrate is cooled and annealed to obtain a multifunctional, multi-region composite CEI film.

[0052] In the coating process, this invention temporarily blocks areas that do not need coating by setting up porous baffles, opening only the baffle holes in the areas that need coating, thus achieving regional coating. During coating, different materials require different evaporation sources, and the film thickness and substrate temperature are monitored in real time. The power and time of each evaporation source are dynamically adjusted to ensure uniform film growth and uniform deposition of each component in a predetermined ratio, ultimately forming a multi-component, multi-region composite CEI film.

[0053] In a preferred embodiment, the cooling and annealing treatment of the substrate to which the coating is applied includes:

[0054] The coated substrate is cooled and gradually restored to normal pressure. The coated substrate is then removed and annealed at 300°C in an argon atmosphere for 2 hours.

[0055] As a preferred embodiment, materials A, B and C use independent evaporation sources during evaporation.

[0056] In a preferred embodiment, the substrate to be coated is rotated during the evaporation process. To ensure uniform material deposition and avoid uneven thickness and composition caused by different relative positions of the evaporation source and the substrate, the substrate to be coated needs to be rotated.

[0057] This invention also provides the application of the above-mentioned CEI film in positive electrode sheets and lithium-ion batteries, specifically:

[0058] A positive electrode is provided, the surface of which has a CEI film as described above.

[0059] A lithium-ion battery is provided, comprising a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode is the aforementioned positive electrode.

[0060] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0061] It should be noted that, unless otherwise specified, the experimental methods used in the embodiments are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0062] Example 1

[0063] The preparation of LiF-LiAlO2-Li3N composite CEI films includes the following steps:

[0064] (1) Three different functional materials were placed in the corresponding evaporation boat, including LiF, LiAlO2 and Li3N, with a mass ratio of 1:1:1.

[0065] (2) Place the evaporation source materials into molybdenum crucibles and fix them in the evaporation boat. Use an independent evaporation source for each material (LiF, LiAlO2, Li3N). Also, place the cathode material (ternary nickel-rich layered oxide LiNi) into the evaporation boat. 0.8 Co 0.1 Mn 0.1 O2 (NCM811) is used as a substrate and fixed on a rotating substrate support. A porous baffle is placed there to separate the different functional material areas. In this embodiment, the substrate is divided into 6 regions, and two coating areas are set for each material.

[0066] (3) Evacuate the system to 10 -5 Below Pa, the LiF evaporation source was preheated to 1100℃, the LiAlO2 evaporation source to 1600℃, and the Li3N evaporation source to 600℃, respectively. First, the LiF evaporation source was started, the corresponding orifice was opened, and the evaporation power was controlled at 100-150W. Then, the LiF region was closed, and the LiAlO2 evaporation source was started, the corresponding orifice was opened, and the power was controlled at 300-600W. Finally, the LiAlO2 region was closed, and the Li3N evaporation source was started, the corresponding orifice was opened, and the power was controlled at 60-120W. The evaporation order of the three materials is not fixed.

[0067] (4) After evaporation, cool the substrate and gradually restore it to normal pressure. Take out the coated substrate and anneal it at 300°C in an argon atmosphere for 2 hours.

[0068] (5) The annealed substrate was placed under an atomic force microscope (AFM) and the Young's modulus of the electrode surface coated with the CEI film was calculated by measuring the force-displacement curve to evaluate its mechanical strength. Then it was assembled into a coin cell and its performance was tested, including interfacial impedance, cycle life, and rate performance.

[0069] This experiment required configuring the positive electrode material into a button cell for testing. The specific procedures were as follows: NCM811 with a coating was used as the positive electrode material, and lithium metal was used as the negative electrode. A 1 mol / L LiPF6 / EC (ethylene carbonate) / DMC (diethyl carbonate) electrolyte (EC and DMC volume ratio 1:1) was used, and a polypropylene microporous membrane was used as the separator. Battery assembly was performed in a glove box under a high-purity argon atmosphere. A two-electrode battery testing module was used to test the battery's performance.

[0070] Interfacial impedance testing: Electrochemical impedance spectroscopy (EIS) was used in the frequency range of 10... 5 Up to 10 -3 Within Hz, a 5mV AC voltage signal is applied to the battery after 100 cycles, and the impedance of lithium ions migrating through the interface film is measured.

[0071] Cyclic performance testing: Under room temperature conditions, the battery was cycled at a charge rate of 0.5C and a discharge rate of 1C within a voltage range of 3.0 to 4.3V. The battery was allowed to rest for 1 minute before each constant current charge / discharge cycle. Cyclic testing continued until the battery's discharge capacity decreased to a certain percentage of its initial capacity to assess its cycle life.

[0072] Rate performance testing: Under room temperature conditions, the battery was subjected to constant current discharge testing at a rate of 7C within a voltage range of 3.0 to 4.3V. Before each discharge, the battery was allowed to stand for 1 minute to ensure the stability of the electrochemical system. The discharge process continued until the voltage reached the set lower limit (3.0V), and the battery's discharge capacity and performance indicators were recorded to evaluate its rate performance at high rates.

[0073] Example 2

[0074] The difference between this embodiment and Embodiment 1 is that the ratio of LiF, LiAlO2 and Li3N is 1:1:1.5, while the other steps remain unchanged.

[0075] Example 3

[0076] Compared with Example 1, the difference in this embodiment is that the high mechanical strength and structural density material LiAlO2 is replaced with Li2ZrO3, the corresponding evaporation source is preheated to 1400℃, the evaporation power is controlled at 300-500W, and the proportion of the three functional materials remains unchanged.

[0077] Example 4

[0078] The difference between this embodiment and Embodiment 1 is that Li3N is replaced with BaTiO3, the corresponding evaporation source is preheated to 850°C, the evaporation power is controlled between 100-400W, and the proportions of the three functional materials remain unchanged.

[0079] Example 5

[0080] Compared with Example 1, the difference in this embodiment is that Li3N is replaced with PbTiO3, the corresponding evaporation source is preheated to 800°C, the evaporation power is controlled at 100-300W, and the proportion of the three functional materials remains unchanged.

[0081] Comparative Example 1

[0082] To compare the overall electrochemical performance of the multi-component composite CEI film, the difference between this comparative example and Example 1 is that only LiF was used for evaporation coating and then electrochemical testing was performed.

[0083] Comparative Example 2

[0084] To compare the overall electrochemical performance of the multi-component composite CEI film, the difference between this comparative example and Example 1 is that only LiAlO2 was used for evaporation coating and then electrochemical testing was performed.

[0085] Comparative Example 3

[0086] To compare the overall electrochemical performance of the multi-component composite CEI film, the difference between this comparative example and Example 1 is that the coating is LiF-LiAlO2, and Li3N material is not coated.

[0087] First, start the LiF evaporation source, open the corresponding baffle orifice, and control the evaporation power at 100-150W; then close the baffle orifice in the LiF region, start the LiAlO2 evaporation source, open the corresponding orifice, and control the power at 300-600W; control the ratio of LiF to LiAlO2 to 1:1 by dynamically adjusting the power and evaporation time of each evaporation source, and then perform electrochemical tests.

[0088] The electrochemical performance test data of Examples 1-5 and Comparative Examples 1-3 are shown in Table 1.

[0089] Table 1. Electrochemical performance test data of Examples 1-5 and Comparative Examples 1-3

[0090]

[0091] As can be seen from the data in Table 1, the CEI films of Examples 1 and 2 are composed of LiF-LiAlO2-Li3N and are divided into 6 functional regions. Their cycle life, rate performance and capacity retention are all at a high level. They also have low interface impedance, which is beneficial to reducing the internal resistance of the battery. The films have good mechanical toughness and can effectively suppress the volume change of the electrode material, thus exhibiting good comprehensive performance.

[0092] In Example 3, LiAlO2 was replaced with Li2ZrO3; in Example 4, Li3N was replaced with BaTiO3; and in Example 5, Li3N was replaced with PbTiO3. Although the interface impedance increased to some extent, the overall performance remained good, and the capacity retention and rate performance were both at a high level. This shows that the various material choices provided in this invention can achieve the technical effects of this invention.

[0093] Comparative Example 1 uses only LiF for evaporation coating. Compared with Example 1, the interface impedance increases significantly, the cycle performance decreases to some extent, and the rate performance decreases significantly.

[0094] Comparative Example 2 used only LiAlO2 for evaporation coating. Compared with Example 1, the interface impedance increased significantly, the cycle performance changed little, but the rate performance decreased significantly.

[0095] Comparative Example 3 uses LiF-LiAlO2 coating without Li3N material. It has good performance in all aspects, but compared with Example 1, the interface impedance increases and the rate performance decreases to some extent, while the cycle performance is better.

[0096] Therefore, as can be seen from the comparison between Comparative Examples 1-3 and Example 1, the multi-component composite CEI film of the present invention can effectively improve the overall performance of the battery.

[0097] Finally, it should be noted that the above specific embodiments are only used to describe the purpose, technical solution, and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation of the present invention and is not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing specific embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions or improvements can be made to some or all of the technical features. These modifications, equivalent substitutions, and improvements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A positive electrode plate, characterized in that, The surface of the positive electrode has a multifunctional multi-region composite CEI film. The CEI film includes material A, material B and material C. Material A, material B and material C divide the CEI film into n regions. Material A, material B and material C form the same number of regions on the CEI film, where n is a positive integer ≥3. Material A is selected from any one or more of LiF, Li2CO3, LiNbO3, and LiTaO3; Material B is selected from any one or more of Al2O3, Li2ZrO3, and LiAlO2; Material C is selected from any one or more of Li3N, BaTiO3, and PbTiO3.

2. The positive electrode sheet according to claim 1, characterized in that, The mass ratio of materials A, B, and C is 1:(0.5-2):(0.5-2).

3. A positive electrode sheet according to claim 2, characterized in that, The mass ratio of material A, material B and material C is 1:(1-1.5):(1-1.5).

4. The positive electrode sheet as described in claim 1, characterized in that, The preparation method of the multifunctional multi-region composite CEI film includes the following steps: Using a high-vacuum thermal evaporation system, materials A, B, and C are placed in their respective evaporation boats. The positive electrode material is fixed on a rotating substrate support as the substrate to be coated, and a porous baffle is placed to shield different material areas of the substrate. In a high vacuum environment, start the evaporation source corresponding to any material, open the baffle hole of the material area to be coated for evaporation, and close the baffle hole corresponding to other material areas. Only repeat the operation to complete the regional coating of materials A, B and C. After evaporation, the coated substrate is cooled and annealed to obtain a multifunctional, multi-region composite CEI film.

5. A positive electrode sheet according to claim 4, characterized in that, The cooling and annealing process of the substrate to which the coating is applied includes: The coated substrate is cooled and gradually restored to normal pressure. The coated substrate is then removed and annealed at 300°C in an argon atmosphere for 2 hours.

6. A positive electrode sheet according to claim 4, characterized in that, During evaporation, materials A, B, and C use independent evaporation sources.

7. A positive electrode sheet according to claim 4, characterized in that, During the evaporation process, the substrate to be coated is in a rotating state.

8. A lithium-ion battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator, characterized in that, The positive electrode is the positive electrode as described in claim 1.

Images