Lithium supplementing material, preparation method and application thereof, and lithium ion battery

Abstract

The application provides a lithium supplementing material, a preparation method and application thereof, and a lithium ion battery. The lithium supplementing material comprises a core and a coating layer covering at least part of the surface of the core. The core comprises a two-phase composite matrix, and the two-phase composite matrix comprises a first matrix phase and a second matrix phase. The first matrix phase comprises Li2NiO2, and the second matrix phase comprises Li4SiO4. At least part of the first matrix phase and at least part of the second matrix phase are interwoven with each other. The material of the coating layer comprises a carbon material. The lithium supplementing material provided by the application can simultaneously consider air stability, resistivity, ionic conductivity and high-temperature cycle stability.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to lithium replenishment materials, their preparation methods, applications, and lithium-ion batteries. Background Technology

[0002] The initial charge-discharge capacity loss (ICE) of lithium-ion batteries is one of the core bottlenecks restricting their energy density improvement. Lithium replenishment agents can compensate for the lithium-ion loss during the initial delithiation process of the cathode material by providing lithium ions in advance, significantly improving the battery's energy density and cycle life. Li2NiO2, as a high-capacity lithium replenishment agent (theoretically replenishing lithium capacity up to 417 mAh / g), has become a research hotspot in the industry due to its high lithium content and excellent lithium replenishment efficiency. However, current Li2NiO2 lithium replenishment agents suffer from drawbacks such as poor air stability, high resistivity, low ionic conductivity, and poor high-temperature cycling stability, which greatly restricts their widespread application in lithium-ion batteries. Summary of the Invention

[0003] Based on this, this application provides a lithium replenishing material, its preparation method, application, and lithium-ion battery, aiming to synergistically balance the air stability, resistivity, ionic conductivity, and high-temperature cycling stability of the lithium replenishing agent.

[0004] A first aspect of this application provides a lithium replenishment material, comprising a core and a coating layer covering at least a portion of the surface of the core;

[0005] The core includes a biphase composite matrix, which includes a first matrix phase and a second matrix phase. The first matrix phase includes Li2NiO2, and the second matrix phase includes Li4SiO4. At least a portion of the first matrix phase and at least a portion of the second matrix phase are intertwined.

[0006] The coating layer is made of carbon materials.

[0007] In some implementations, one or more of the following conditions are met:

[0008] (1) In the kernel, the first matrix phase and the second matrix phase form a three-dimensional network structure that interweaves and intertwines in three-dimensional space;

[0009] (2) The molar ratio of the first matrix phase to the second matrix phase is (0.95~0.80):(0.05~0.20), and can be selected as (0.90~0.80):(0.10~0.20).

[0010] (3) The first matrix phase and the second matrix phase are nanoscale composites;

[0011] Optionally, the Dv50 particle size of the dual-phase composite matrix is ​​1μm~5μm.

[0012] In some implementations, one or more of the following conditions are met:

[0013] (1) The material of the coating layer also includes aluminum oxide;

[0014] (2) The thickness of the coating layer is 5nm~20nm;

[0015] (3) The carbon material accounts for 2% to 5% of the mass of the lithium supplement material, and can be selected as 2.85% to 5%;

[0016] (4) The porosity of the coating layer is ≤6%, and can be selected as 1%~5%;

[0017] (5) The specific surface area of ​​the coating layer is greater than 0 and less than or equal to 2m². 2 / g, optional 0.9m 2 / g~1.8m 2 / g.

[0018] A second aspect of this application provides a method for preparing a lithium supplement material, comprising:

[0019] Nickel source, lithium source and silicon source are mixed in a preset stoichiometric ratio to prepare a mixed powder;

[0020] The mixed powder is heat-treated under a protective atmosphere to synthesize a core comprising a biphase composite matrix in situ through a one-step solid-state reaction. The biphase composite matrix comprises a first matrix phase and a second matrix phase. The first matrix phase comprises Li2NiO2, and the second matrix phase comprises Li4SiO4. At least a portion of the first matrix phase and at least a portion of the second matrix phase are intertwined.

[0021] A coating layer comprising carbon material is deposited on at least a portion of the surface of the core to prepare a lithium supplement material.

[0022] In some implementations, one or more of the following conditions are met:

[0023] (1) The preset stoichiometric ratio makes the molar ratio of the first matrix phase to the second matrix phase in the lithium replenishment material (0.95~0.80):(0.05~0.20), and the lithium source is 5%~10% in excess of the theoretical lithium requirement for the complete reaction to generate Li2NiO2 and Li4SiO4;

[0024] (2) The lithium source includes one or more of lithium oxide, lithium hydroxide, lithium carbonate and lithium chloride;

[0025] (3) The silicon source includes one or more of silicon dioxide, silicon tetrachloride, and silicon nitride;

[0026] (4) The nickel source includes one or more of nickel oxide, nickel hydroxide, nickel chloride, nickel sulfate, nickel nitrate and nickel carbonate.

[0027] In some implementations, one or more of the following conditions are met:

[0028] (1) The preparation method of the mixed powder includes:

[0029] A mixture of nickel, lithium, and silicon sources was wet-milled to prepare a mixed slurry;

[0030] The mixed slurry is vacuum dried to prepare the mixed powder.

[0031] Optionally, the rotation speed of the wet ball mill is 200 r / min to 600 r / min, and the ball milling time is 3 h to 10 h;

[0032] Optionally, the vacuum drying temperature is 80℃~120℃, and the time is 8h~12h;

[0033] (2) The heat treatment includes: heating to 700℃~900℃ at a rate of 5℃ / min~10℃ / min and holding for 2h~10h.

[0034] In some embodiments, the preparation method for depositing the coating layer includes chemical vapor deposition or atomic layer deposition.

[0035] Optionally, the chemical vapor deposition method satisfies one or more of the following conditions:

[0036] (1) The reaction temperature of the chemical vapor deposition method is 450℃~650℃;

[0037] (2) The deposition time of the chemical vapor deposition method is 0.5h~3h;

[0038] (3) The carbon source gas used in the chemical vapor deposition method includes one or more of methane, acetylene and ethylene.

[0039] The third aspect of this application provides the application of a lithium-ion battery in which a lithium-ion battery supplement material as described in the first aspect of this application or a lithium-ion battery supplement material prepared by the preparation method of the second aspect of this application is used.

[0040] The fourth aspect of this application provides a lithium-ion battery, including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive active layer, the positive active layer comprising a positive active material and a lithium replenishing material of the first aspect of this application or a lithium replenishing material prepared by the preparation method of the second aspect of this application.

[0041] In some implementations, one or more of the following conditions are met:

[0042] (1) In the positive electrode active layer, based on the total mass of the positive electrode active material, the amount of lithium supplement material added is 0.5%~5%;

[0043] (2) The positive electrode active material includes Li z (Ni x Co y M 1 1-x-y O2 and Li β Fe α M 2 (1-α) One or more of PO4;

[0044] Among them, M 1 Including Mn and / or Al, 0 <x<1,0<y<1,1≤z≤1.1;

[0045] M 2 It includes one or more of Ti, V, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, and Sr, with 0.2≤α≤1 and 1≤β≤1.1.

[0046] The lithium supplement material provided in this application achieves a synergistic balance of air stability, electronic conductivity, ionic conductivity, and high-temperature cycling performance of Li2NiO2 by forming a specific structure of Li2NiO2 and Li4SiO4 into a two-phase composite matrix and forming a coating layer including carbon material on the surface of the two-phase composite matrix. This breaks through the technical bottleneck that current single modification schemes cannot address multiple pain points simultaneously, thus forming a synergistic effect. Attached Figure Description

[0047] Figure 1 The image shows a scanning electron microscope (SEM) image of the lithium-supplementing material prepared in Example 1. Detailed Implementation

[0048] To facilitate understanding of this application, a more complete description will be provided below. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0049] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. It should be noted that, unless otherwise stated, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items, "above," "below," includes the stated number, and "one or more" with "multiple" means two or more.

[0051] In this document, when referring to numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of selectable values ​​within a numerical interval is considered continuous, and includes the two endpoints (i.e., the minimum and maximum values) of the numerical interval, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all subranges included therein. The "numerical value" in this numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, and other numerical interval types.

[0052] In this document, for methods involving multiple steps, unless otherwise explicitly stated herein, there is no strict order constraint on the execution of these steps; they may be executed in any order other than those described. Moreover, any step may include multiple sub-steps or multiple stages, which are not necessarily completed at the same time, but may be executed at different times, and their execution order is not necessarily sequential, but may be executed in turn, alternately, or simultaneously with other steps or parts of the sub-steps or stages of other steps.

[0053] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0054] The initial charge-discharge capacity loss (ICE) of lithium-ion batteries is one of the core bottlenecks restricting the improvement of their energy density. Lithium replenishment agents can compensate for the lithium-ion loss during the initial delithiation process of the cathode material by providing lithium ions in advance, thus significantly improving the battery's energy density and cycle life. Li2NiO2, as a high-capacity lithium replenishment agent (theoretical lithium replenishment capacity of 417 mAh / g), has become a research hotspot in the industry due to its high lithium content and excellent lithium replenishment efficiency.

[0055] However, the current Li2NiO2 lithium replenishing agents usually have the following significant technical defects, which limit their large-scale application: (1) Extremely poor air stability: Li2NiO2 is prone to react with H2O and CO2 in the air to generate impurity phases such as LiOH and Li2CO3, which leads to a decrease in lithium replenishing activity. Moreover, the impurities will be introduced into the battery system to trigger side reactions, affecting battery safety; (2) High resistivity (poor electronic conductivity): Li2NiO2 itself has high resistivity, which leads to the obstruction of ion and electron transport during the lithium replenishment process, resulting in a decrease in lithium replenishment efficiency and a deterioration in battery rate performance; (3) Poor ionic conductivity: Li2NiO2 itself has low ionic conductivity, resulting in a slow activation rate, low rate lithium replenishment efficiency, and poor cycle stability; (4) Weak high-temperature performance: At high temperatures of 45℃ and above, Li2NiO2 is prone to structural collapse and Ni ion dissolution, which can cause violent side reactions with the electrolyte, leading to accelerated battery capacity decay and deterioration of cycle stability.

[0056] To address the aforementioned shortcomings, researchers have proposed several modification schemes: First, doping modification (such as doping with metal ions like Cu, Al, and Mg) can improve structural stability to some extent, but it is difficult to simultaneously improve conductivity and air stability. Second, carbon coating modification, traditionally using solid-phase mixed carbon sources (such as sucrose or acetylene black) followed by sintering and coating, however, results in uneven carbon layer thickness, weak bonding with the matrix, and easy blockage of lithium-ion transport channels, thus reducing ionic conductivity. Third, multiphase physical mixing modification, such as using a multi-step process of "preparing Li2NiO2 and the composite phase separately, then mechanically mixing," however, this method suffers from uneven dispersion of the composite phase and poor interfacial bonding, resulting in limited performance improvement. It is evident that current modification schemes generally suffer from drawbacks such as singular performance improvement, cumbersome processes, and high costs, making it difficult to achieve a synergistic balance of air stability, resistivity and conductivity, ionic conductivity, and high-temperature cycling performance in Li2NiO2 lithium supplementers. In view of this, the inventors have proposed the following technical solution in this application.

[0057] In a first aspect, this application provides a lithium replenishment material, including a core and a coating layer covering at least a portion of the surface of the core;

[0058] The core comprises a two-phase composite matrix, which includes a first matrix phase and a second matrix phase. The first matrix phase includes Li2NiO2, and the second matrix phase includes Li4SiO4. At least a portion of the first matrix phase and at least a portion of the second matrix phase are interwoven. The coating layer is made of carbon material.

[0059] It is understood that the "two-phase composite matrix" in this application refers to a structure formed by combining two phases (or materials) with different properties that are independent and interlocked in three-dimensional space, aiming to achieve comprehensive properties that are difficult for a single material to possess at the same time.

[0060] Li4SiO4 possesses both high chemical stability and lithium-ion conductivity, and exhibits virtually no delithiation reaction. It also demonstrates good air stability and insensitivity to water. Therefore, it can physically isolate Li2NiO2 from contact with air and electrolyte, inhibiting impurity formation and structural collapse. Furthermore, it can enhance the lithium-ion conductivity of the system, ensuring rapid lithium ion extraction from the lithium replenisher and improving its utilization rate. Based on this, this application establishes a two-phase composite matrix of Li2NiO2 and Li4SiO4. Li4SiO4 acts as a three-dimensional ionic conductive network and structurally stable framework throughout the two-phase composite matrix, intertwining and interlocking with Li2NiO2. This specific structure further enhances the chemical stability, ionic conductivity, and air stability of the lithium replenishment material. Specifically, the two phases of Li2NiO2 and Li4SiO4 form coherent grain boundaries through chemical bonding, resulting in high interfacial bonding strength and low ion transport resistance. Furthermore, the two phases interpenetrate uniformly during synthesis, forming a continuous three-dimensional lithium-conducting network, which significantly improves ionic conductivity. The simultaneous synthesis of Li2NiO2 and Li4SiO4 phases forms an intercrystalline framework, which helps to suppress structural distortion and Ni ion dissolution, and improves cycle and high-temperature stability. In addition, the two-phase composite matrix can improve the overall intrinsic stability of the material, effectively passivate the surface active sites, and form a double protection with the coating layer, which greatly enhances air stability.

[0061] Meanwhile, the carbon coating not only enhances the electronic conductivity of Li2NiO2 but also further blocks the erosion of the core by air and electrolyte, forming a dual protection with Li4SiO4 and strengthening air stability and high-temperature performance. Therefore, the lithium supplement material provided in this application, by forming a specific structure of a two-phase composite matrix of Li2NiO2 and Li4SiO4 and forming a carbon coating on the surface of the two-phase composite matrix, achieves a synergistic balance of air stability, electronic conductivity, ionic conductivity, and high-temperature cycling performance of Li2NiO2. This overcomes the technical bottleneck of current single modification schemes being unable to address multiple pain points simultaneously, resulting in a synergistic effect.

[0062] In some embodiments, within the core, the first matrix phase and the second matrix phase form an interwoven three-dimensional network structure in three-dimensional space. This interwoven three-dimensional network structure is beneficial for further enhancing the structural and chemical stability of the lithium replenishment material, giving it high air stability and high-temperature cycling performance; at the same time, this three-dimensional network structure is beneficial for strengthening the three-dimensional ionic conductivity network, giving the lithium replenishment material high ionic conductivity.

[0063] In some embodiments, the molar ratio of the first matrix phase to the second matrix phase is (0.95~0.80):(0.05~0.20), optionally (0.90~0.80):(0.10~0.20). For example, the molar ratio of the first matrix phase to the second matrix phase can be 0.80:0.20, 0.90:0.20, 0.95:0.20, 0.80:0.05, 0.90:0.05, 0.95:0.05, or within any range of the above values. Reasonably controlling the molar ratio of the first matrix phase to the second matrix phase allows the lithium-supplementing material to contribute more effective lithium with a limited amount added, achieving a synergistic balance between stability and conductivity, rather than solely relying on physical protection. This is beneficial for considering the lithium-supplementing effect, air stability, ionic conductivity, and high-temperature cycling performance of the lithium-supplementing material.

[0064] In some embodiments, the first matrix phase and the second matrix phase are nanoscale composites. This nanoscale composite is beneficial for increasing the interweaving and interlocking of Li2NiO2 and Li4SiO4, resulting in further enhancement of the chemical stability, ionic conductivity, and air stability of the lithium supplementation material.

[0065] In some embodiments, the Dv50 particle size of the dual-phase composite matrix is ​​1 μm to 5 μm. For example, the Dv50 particle size can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or within any range of these values. Reasonably controlling the Dv50 particle size of the dual-phase composite matrix is ​​beneficial for increasing the interweaving and interlocking of Li2NiO2 and Li4SiO4, leading to further enhancement of the chemical stability, ionic conductivity, and air stability of the lithium-supplementing material.

[0066] In some embodiments, the thickness of the coating layer is 5 nm to 20 nm. For example, the thickness of the coating layer can be 5 nm, 8 nm, 11 nm, 13 nm, 15 nm, 17 nm, 20 nm, or any value within the range above. By reasonably controlling the thickness of the coating layer, the electronic conductivity of the lithium replenishment material can be improved, and the coating layer can also provide good air barrier properties, while ensuring good transport and migration of active lithium extracted from the core. This prevents the coating layer from blocking ion transport channels and guarantees lithium replenishment efficiency.

[0067] Without limitation, the average particle size of the first matrix phase, the average particle size of the second matrix phase, and the thickness of the coating layer can all be measured by scanning electron microscopy (SEM).

[0068] In some embodiments, the carbon material accounts for 2% to 5% of the mass of the lithium-supplementing material, optionally 2.85% to 5%. For example, the mass percentage of carbon material in the lithium-supplementing material can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any range thereof. This effectively reduces the porosity and surface active sites of the coating layer, reduces the contact area between air (H2O, CO2) and electrolyte and the Li2NiO2 matrix, avoids impurity generation and interfacial side reactions, and, combined with the dual-phase composite effect of Li4SiO4, significantly improves the air stability and electrolyte erosion resistance of the lithium-supplementing material.

[0069] In some embodiments, the porosity of the coating layer is ≤6%, and can be selected from 1% to 5%. For example, the porosity of the coating layer can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, or within any range of the above values. Low porosity (≤6%) ensures that the coating layer has virtually no through-pores, forming a continuous and dense protective barrier, inhibiting Ni ion dissolution and Li2NiO2 crystal structure collapse under high-temperature conditions, and improving high-temperature cycling stability.

[0070] In some embodiments, the specific surface area of ​​the coating layer is greater than 0 and less than or equal to 2m². 2 / g, optional 0.9m 2 / g~1.8m 2 / g. The specific surface area of ​​the coating layer can be 0.1m². 2 / g, 0.3m 2 / g, 0.5m 2 / g, 0.7m 2 / g, 1m 2 / g, 1.3m 2 / g, 1.5m 2 / g, 1.7m 2 / g、2m 2 / g or within any of the above values. This indicates that the coating layer has high density, which helps to prevent air and electrolyte from eroding the Li2NiO2 in the core, giving the lithium supplement material high air stability. At the same time, it avoids the increased lithium-ion transport resistance caused by excessively thick or porous coating layers, ensuring rapid lithium-ion conduction between the coating layer, the substrate, and the electrolyte. Combined with the continuous ion transport channels constructed by Li4SiO4, it improves lithium-ion conductivity.

[0071] In some embodiments, the coating material also includes alumina. Alumina helps to further improve the density of the coating, giving it better barrier properties against air and electrolyte, and further improving the air stability of the lithium replenishment material. Furthermore, when the coating material includes a two-phase mixture of carbon materials and alumina, the two-phase dispersion is better than that of a single phase, resulting in better barrier protection.

[0072] In some embodiments, the second matrix phase also includes Li3PO4, which forms a solid solution with Li4SiO4. Li3PO4 exhibits stronger chemical stability, which is beneficial for further improving high-temperature cycling performance. Meanwhile, Li3PO4 is an inert phase and lacks ion conductivity; therefore, when mixed with Li4SiO4 to form a solid solution, numerous defects and disordered atomic arrangement are generated internally, which can open efficient three-dimensional channels for the rapid migration of lithium ions, thereby improving ionic conductivity.

[0073] Secondly, this application provides a method for preparing a lithium-supplementing material, which can be used to prepare the lithium-supplementing material of the first aspect of this application, and may include the following steps:

[0074] S1. Mix the nickel source, lithium source and silicon source according to a preset stoichiometric ratio to prepare a mixed powder;

[0075] S2. The mixed powder is heat-treated under a protective atmosphere to synthesize a core comprising a biphase composite matrix in situ through a one-step solid-phase reaction. The biphase composite matrix comprises a first matrix phase and a second matrix phase. The first matrix phase comprises Li2NiO2 and the second matrix phase comprises Li4SiO4. At least a portion of the first matrix phase and at least a portion of the second matrix phase are intertwined.

[0076] S3. A coating layer including carbon material is deposited on at least a portion of the surface of the core to prepare a lithium supplement material.

[0077] In the above preparation method, the mixed powder obtained in step S1 is heat-treated under a protective atmosphere. A first matrix phase is generated by reacting the nickel source and part of the lithium source through a one-step solid-state reaction, while a second matrix phase is generated by reacting the silicon source and part of the lithium source. This results in a two-phase composite matrix of Li2NiO2 and Li4SiO4 in situ. Then, a coating layer is formed on the surface of the two-phase composite matrix through the deposition process in step S3.

[0078] Accordingly, this application combines a one-step solid-state reaction for core preparation with a deposition process for coating layer preparation. The former ensures close contact and an ideal interface between the functional phase (Li4SiO4) and the active phase (Li2NiO2); the latter provides a uniform, dense, and thickness-controllable electronically conductive and physically insulating layer, achieving simultaneous optimization of air stability, electronic conductivity, ionic conductivity, and high-temperature performance. This overcomes the technical bottleneck of single modification schemes failing to address multiple pain points simultaneously, resulting in a synergistic effect. Furthermore, the preparation method provided in this application, especially the one-step solid-state process, simplifies the process, reduces energy consumption, and helps lower industrialization costs.

[0079] In some embodiments, a preset stoichiometric ratio is used such that the molar ratio of the first matrix phase to the second matrix phase in the lithium supplementation material is (0.95~0.80):(0.05~0.20), and the lithium source is in excess by 5%~10% relative to the theoretical lithium requirement for the complete reaction to generate Li2NiO2 and Li4SiO4. By precisely controlling the preset stoichiometric ratio and the lithium source ratio, the first matrix phase and the second matrix phase can be converted in situ during the one-step solid-state reaction, and the molar ratio of the first matrix phase to the second matrix phase is (0.95~0.80):(0.05~0.20), while simultaneously achieving uniform composite of the Li2NiO2 active phase and the Li4SiO4 functional phase at the nanoscale.

[0080] In some embodiments, the heat treatment includes heating to 700°C to 900°C at a rate of 5°C / min to 10°C / min and holding at that temperature for 2 hours to 10 hours. For example, this rate can be 5°C / min, 7°C / min, 9°C / min, 10°C / min, or any range thereof. This heat treatment condition is beneficial for promoting the formation of a biphase composite matrix, achieving uniform composite of the Li2NiO2 active phase and the Li4SiO4 functional phase at the nanoscale, and forming an interwoven three-dimensional network structure in three-dimensional space.

[0081] In some embodiments, the lithium source includes one or more of lithium oxide, lithium hydroxide, lithium carbonate, and lithium chloride.

[0082] In some implementations, the silicon source includes one or more of silicon dioxide, silicon tetrachloride, and silicon nitride.

[0083] In some embodiments, the nickel source includes one or more of nickel oxide, nickel hydroxide, nickel chloride, nickel sulfate, nickel nitrate, and nickel carbonate.

[0084] In some embodiments, the method for preparing the mixed powder may include the following steps:

[0085] S11. A mixture of nickel source, lithium source and silicon source is wet-milled to prepare a mixed slurry;

[0086] S12. Vacuum dry the mixed slurry to prepare mixed powder.

[0087] In some embodiments, the rotation speed of the wet ball mill is 200 r / min to 600 r / min, and the milling time is 3 h to 10 h. In other embodiments, the medium for wet ball milling includes, but is not limited to, anhydrous ethanol.

[0088] In some embodiments, the vacuum drying temperature is 80°C to 120°C, and the time is 8 hours to 12 hours.

[0089] In some embodiments, the preparation method for depositing the coating layer includes chemical vapor deposition (CVD) or atomic layer deposition (ALD).

[0090] In some embodiments, the reaction temperature of the chemical vapor deposition (CVD) process is 450°C to 650°C. For example, the reaction temperature can be 450°C, 500°C, 550°C, 600°C, 650°C, or any value within the range described above. In other embodiments, the deposition time of the CVD process is 0.5 h to 3 h. For example, the deposition time can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, or any value within the range described above. Reasonably controlling the reaction temperature and reaction time is beneficial for promoting the formation of a dense coating layer, enabling the porosity and specific surface area of ​​the coating layer to reach the ranges described above in this application.

[0091] In some implementations, the carbon source gas used in chemical vapor deposition includes one or more of methane, acetylene, and ethylene.

[0092] Thirdly, this application provides the application of a lithium-ion battery in which a lithium-ion battery is prepared as described in the first aspect of this application or by the preparation method described in the second aspect of this application is used.

[0093] Fourthly, this application provides a lithium-ion battery, including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive active layer, the positive active layer containing the lithium replenishing material of the first aspect of this application or the lithium replenishing material prepared by the preparation method of the second aspect of this application.

[0094] In some embodiments, the amount of lithium-replenishing material added to the positive electrode active layer is 0.5% to 5% based on the total mass of the positive electrode active material. For example, the amount of lithium-replenishing material added can be 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, or within any range of the above values. This is beneficial for balancing lithium replenishment effect and battery capacity.

[0095] In some embodiments, the positive electrode active material includes Li z (Nix Co y M 1 1-x-y O2 and Li β Fe α M 2 (1-α) One or more of PO4;

[0096] Among them, M 1 Including Mn and / or Al, 0 <x<1,0<y<1,1≤z≤1.1;

[0097] M 2 It includes one or more of Ti, V, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, and Sr, with 0.2≤α≤1 and 1≤β≤1.1.

[0098] In some embodiments, the lithium-ion battery further includes a negative electrode, an electrolyte, and a separator. During battery charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0099] Fifthly, this application provides an electronic device including the secondary battery of the third aspect of this application.

[0100] In some implementations, the type of electronic device is not particularly limited, and it can be any electronic device known in the prior art. For example, electronic devices may include, but are not limited to, power tools, electric vehicles, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, etc.

[0101] The following are specific embodiments, which describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations within the scope of the disclosure of this application will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0102] Example 1

[0103] S1: Mixed powder: NiO, LiOH·H2O (5% excess) and nano SiO2 were weighed according to the stoichiometric ratio of Li2NiO2 to Li4SiO4 in the final product of 0.95:0.05. The mixture was ball-milled with anhydrous ethanol as the dispersion medium at 250 r / min for 6 h to obtain a slurry. The slurry was then vacuum-dried at 100℃ for 10 h to obtain the mixed powder.

[0104] S2: In-situ synthesis of the biphase composite matrix core: Under nitrogen atmosphere protection, the heating rate is 5℃ / min, and the temperature is raised to 800℃ and held for 6h.

[0105] S3: Carbon coating: Under nitrogen atmosphere protection, the temperature is raised to 650℃ at a rate of 5℃ / min, with an acetylene to nitrogen volume ratio of 1:10, and the coating is carried out for 1 hour to obtain the lithium-replenishing material (see [reference]). Figure 1 ).

[0106] Example 2

[0107] S1: Mixed raw materials: NiO, LiOH·H2O (5% excess) and nano SiO2 were weighed according to the stoichiometric ratio of Li2NiO2 to Li4SiO4 in the final product of 0.9:0.1. The mixture was ball-milled with anhydrous ethanol as the dispersion medium at 250 r / min for 6 h to obtain a slurry. The slurry was then vacuum-dried at 100℃ for 10 h to obtain a mixed powder.

[0108] S2: In-situ synthesis of the biphase composite matrix core: Under nitrogen atmosphere protection, the heating rate is 5℃ / min, and the temperature is raised to 800℃ and held for 6h.

[0109] S3: Carbon coating: Under nitrogen atmosphere protection, the temperature is raised to 650℃ at a rate of 5℃ / min, with an acetylene to nitrogen volume ratio of 1:10, and the coating is carried out for 1 hour to obtain the lithium replenishment material.

[0110] Example 3

[0111] S1: Mixed raw materials: NiO, LiOH·H2O (5% excess) and nano SiO2 were weighed according to the stoichiometric ratio of Li2NiO2 to Li4SiO4 in the final product of 0.85:0.15. The mixture was ball-milled with anhydrous ethanol as the dispersion medium at 250 r / min for 6 h to obtain a slurry. The slurry was then vacuum-dried at 100℃ for 10 h to obtain a mixed powder.

[0112] S2: In-situ synthesis of the biphase composite matrix core: Under nitrogen atmosphere protection, the heating rate is 5℃ / min, and the temperature is raised to 800℃ and held for 6h.

[0113] S3: Carbon coating: Under nitrogen atmosphere protection, the temperature is raised to 650℃ at a rate of 5℃ / min, with an acetylene to nitrogen volume ratio of 1:10, and the coating is carried out for 1 hour to obtain the lithium replenishment material.

[0114] Example 4

[0115] S1: Mixed raw materials: NiO, LiOH·H2O (5% excess) and nano SiO2 were weighed according to the stoichiometric ratio of Li2NiO2 to Li4SiO4 in the final product of 0.8:0.2. The mixture was ball-milled with anhydrous ethanol as the dispersion medium at 250 r / min for 6 h to obtain a slurry. The slurry was then vacuum-dried at 100℃ for 10 h to obtain a mixed powder.

[0116] S2: In-situ synthesis of the biphase composite matrix core: Under nitrogen atmosphere protection, the heating rate is 5℃ / min, and the temperature is raised to 800℃ and held for 6h.

[0117] S3: Carbon coating: Under nitrogen atmosphere protection, the temperature is raised to 650℃ at a rate of 5℃ / min, with an acetylene to nitrogen volume ratio of 1:10, and the coating is carried out for 1 hour to obtain the lithium replenishment material.

[0118] Comparative Example 1

[0119] Similar to the preparation method in Example 1, the main difference is that nano-SiO2 is not used in step S1, so that the core contains only the first matrix phase Li2NiO2 and does not contain the second matrix phase Li4SiO4.

[0120] Comparative Example 2

[0121] Similar to the preparation method in Example 1, the main difference is that the CVD carbon coating step in S3 is omitted, so that the lithium supplement material does not contain a carbon coating layer.

[0122] Comparative Example 3

[0123] Similar to the preparation method in Example 1, the main difference is that pure phase Li2NiO2 and pure phase Li4SiO4 are physically ball-milled and mixed at a molar ratio of 0.90:0.10 for 1 hour to obtain a mixed powder; then the mixed powder is used to replace the biphase composite matrix core prepared in steps S1 and S2.

[0124] Comparative Example 4

[0125] Similar to the preparation method in Example 1, the main difference is that in step S1, an equal amount of nano Fe2O3 is used to replace nano SiO2, so that the first matrix phase in the core is Li2NiO2 and the second matrix phase is Li5FeO4.

[0126] The lithium replenishment materials or batteries prepared in the examples and comparative examples were subjected to relevant performance tests, and the test results are shown in Tables 1 and 2 below. In Table 1, "molar ratio" refers to the molar ratio of the first matrix phase to the second matrix phase, "mass percentage" refers to the mass percentage of carbon material in the lithium replenishment material, "specific surface area" refers to the specific surface area of ​​the coating layer, and "porosity" refers to the porosity of the coating layer.

[0127] The test conditions or standards for each performance test item are as follows:

[0128] 1. Electrochemical performance testing: 2Ah pouch cell, NCM811 / graphite pouch cell, with NCM811 (LiNi) as the cathode material. 0.8 Co 0.1 Mn 0.1 Based on O2), the mass ratio of lithium supplementation material is 4%. Among them, the positive electrode active layer is prepared by ternary positive electrode material NCM811, acetylene black, binder PVDF and lithium supplementation material in a mass ratio of 92:4:4:4; the negative electrode active layer is prepared by artificial graphite, conductive agent conductive carbon black and binder SBR in a mass ratio of 95:2:3.

[0129] High temperature cycling test: Under the condition of 45±2℃, the battery is charged to 4.5V at a constant current of 0.5C, charged to 0.05C at a constant voltage of 4.5V, and then discharged to 3.0V at a constant current of 1.0C. The charging and discharging equipment used is the Blue Electric Charge-Discharge Tester.

[0130] First charge / discharge efficiency = (First discharge specific capacity / First charge specific capacity) × 100%;

[0131] Cycle capacity retention = (100-cycle discharge specific capacity / initial discharge specific capacity) × 100%;

[0132] Air stability (capacity retention after 24 hours of exposure) = (first discharge specific capacity of the battery assembled after 24 hours of exposure of the positive electrode / first discharge specific capacity of the battery assembled without exposure of the positive electrode) × 100%.

[0133] 2. Powder resistivity test: Four-probe method test.

[0134] 3. Ionic conductivity test: AC impedance method.

[0135] 4. Air stability: Place the positive electrode in a constant temperature and humidity chamber at 25°C and 50% RH for 24 hours.

[0136] 5. Porosity and specific surface area of ​​the coating layer

[0137] The specific surface area was tested using the liquid nitrogen cryogenic nitrogen adsorption method (BET method).

[0138] The overall volumetric porosity of the material is calculated based on the true density and bulk density data of the powder. Porosity = (1 - bulk density / true density) * 100%.

[0139] Table 1

[0140]

[0141] Table 2

[0142]

[0143] In Examples 1-4, the specific surface area is ≤2.0 m². 2 / g and the porosity of the coating layer are both ≤6%, the carbon coating layer is dense, and as the proportion of Li4SiO4 increases, the interface between the two phases is better, the specific surface area and porosity continue to decrease, and the density is getting better and better.

[0144] Electrochemical performance analysis: Regarding the initial charge-discharge efficiency, Examples 1-4 all exceeded 95%, significantly higher than the comparative examples. This indicates that the lithium replenishment material of this application provides abundant and effectively usable active lithium. Through dual-phase composite and carbon coating optimization, this application reduces impurity generation and interfacial side reactions, thereby improving lithium replenishment efficiency and interfacial compatibility. Regarding high-temperature cycle stability, the capacity retention rates of the Examples after 100 cycles at 45°C are comprehensively superior to the comparative examples. With the increase of Li4SiO4 content, the cycle stability (especially high-temperature cycling) systematically improves, with the high-temperature performance advantage being particularly prominent. This confirms the synergistic effect of Li4SiO4 inhibiting Ni ion dissolution and the carbon coating layer blocking electrolyte erosion, effectively mitigating structural collapse and interfacial degradation at high temperatures, and meeting the high-temperature performance requirements of NCM811 / graphite pouch batteries.

[0145] Regarding powder resistivity, the resistivity of the powder in Comparative Example 2 without a carbon coating decreased significantly. As for ionic conductivity, the lithium-ion conductivity of Examples 1-4 increased continuously with the increase in the proportion of Li4SiO4. Comparative Example 1, lacking the Li4SiO4 ionic conductor phase, exhibited low lithium-ion conductivity, hindering ion transport. Comparative Example 3, due to uneven dispersion and poor interfacial bonding in its physically mixed two-phase composition, suffered from insufficient lithium-ion transport efficiency. This indicates that the uniform dispersion of the two phases in one-step solid-phase synthesis can construct continuous ion transport channels, and the carbon coating layer is beneficial for improving electronic conductivity, achieving a synergistic balance between electronic and ionic conductivity.

[0146] Regarding air stability, the positive electrode sheets of Examples 1-4 all exhibited a capacity retention rate of ≥98% after 24 hours of exposure, demonstrating good stability. Furthermore, the capacity retention rate showed a gradual optimization trend with increasing molar proportion of Li4SiO4 (from 0.05 to 0.2). In contrast, Comparative Example 1 had a capacity retention rate of only 94.4%. Due to the lack of physical barrier and ion conduction synergy of Li4SiO4, Li2NiO2 easily reacted with air moisture and carbon dioxide to generate impurities, leading to electrode activity decay. Comparative Examples 2 and 3 had initial efficiency retention rates of 92.1% and 93.8%, respectively. Due to the lack of secondary protection from a dense carbon layer or uneven two-phase dispersion, they were unable to effectively block air erosion, resulting in poor stability. In Comparative Example 4, Li5FeO4 also exhibited poor air stability, resulting in the lowest initial efficiency retention rate. Therefore, the synergistic strategy of "Li4SiO4 composite + carbon coating layer" in this application can significantly improve the air stability of the material during electrode processing and storage by forming a dual barrier through two-phase interface protection and dense carbon layer barrier, effectively mitigating capacity decay.

[0147] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0148] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A lithium supplementation material, characterized in that, Includes a core and a covering layer covering at least a portion of the surface of the core; The core includes a biphase composite matrix, which includes a first matrix phase and a second matrix phase. The first matrix phase includes Li2NiO2, and the second matrix phase includes Li4SiO4. At least a portion of the first matrix phase and at least a portion of the second matrix phase are intertwined. The coating layer is made of carbon materials.

2. The lithium replenishment material according to claim 1, characterized in that, One or more of the following conditions must be met: (1) In the kernel, the first matrix phase and the second matrix phase form a three-dimensional network structure that interweaves and intertwines in three-dimensional space; (2) The molar ratio of the first matrix phase to the second matrix phase is (0.95~0.80):(0.05~0.20), and can be selected as (0.90~0.80):(0.10~0.20). (3) The first matrix phase and the second matrix phase are nanoscale composites; Optionally, the Dv50 particle size of the dual-phase composite matrix is ​​1μm to 5μm.

3. The lithium replenishment material according to claim 1 or 2, characterized in that, One or more of the following conditions must be met: (1) The material of the coating layer also includes aluminum oxide; (2) The thickness of the coating layer is 5nm~20nm; (3) The carbon material accounts for 2% to 5% of the mass of the lithium supplement material, and can be selected as 2.85% to 5%; (4) The porosity of the coating layer is ≤6%, and can be selected as 1%~5%; (5) The specific surface area of ​​the coating layer is greater than 0 and less than or equal to 2m². 2 / g, optional 0.9m 2 / g~1.8m 2 / g.

4. A method for preparing a lithium-supplementing material, characterized in that, include: Nickel source, lithium source and silicon source are mixed in a preset stoichiometric ratio to prepare a mixed powder; The mixed powder is heat-treated under a protective atmosphere to synthesize a core comprising a biphase composite matrix in situ through a one-step solid-state reaction. The biphase composite matrix comprises a first matrix phase and a second matrix phase. The first matrix phase comprises Li2NiO2, and the second matrix phase comprises Li4SiO4. At least a portion of the first matrix phase and at least a portion of the second matrix phase are intertwined. A coating layer comprising carbon material is deposited on at least a portion of the surface of the core to prepare a lithium supplement material.

5. The preparation method according to claim 4, characterized in that, One or more of the following conditions must be met: (1) The preset stoichiometric ratio makes the molar ratio of the first matrix phase to the second matrix phase in the lithium replenishment material (0.95~0.80):(0.05~0.20), and the lithium source is 5%~10% in excess of the theoretical lithium requirement for the complete reaction to generate Li2NiO2 and Li4SiO4; (2) The lithium source includes one or more of lithium oxide, lithium hydroxide, lithium carbonate and lithium chloride; (3) The silicon source includes one or more of silicon dioxide, silicon tetrachloride, and silicon nitride; (4) The nickel source includes one or more of nickel oxide, nickel hydroxide, nickel chloride, nickel sulfate, nickel nitrate and nickel carbonate.

6. The preparation method according to claim 4 or 5, characterized in that, One or more of the following conditions must be met: (1) The preparation method of the mixed powder includes: A mixture of nickel, lithium, and silicon sources was wet-milled to prepare a mixed slurry; The mixed slurry is vacuum dried to prepare the mixed powder. Optionally, the rotation speed of the wet ball mill is 200 r / min to 600 r / min, and the ball milling time is 3 h to 10 h; Optionally, the vacuum drying temperature is 80℃~120℃, and the time is 8h~12h; (2) The heat treatment includes: heating to 700℃~900℃ at a rate of 5℃ / min~10℃ / min and holding for 2h~10h.

7. The preparation method according to claim 4 or 5, characterized in that, The methods for preparing the coating layer by deposition include chemical vapor deposition or atomic layer deposition. Optionally, the chemical vapor deposition method satisfies one or more of the following conditions: (1) The reaction temperature of the chemical vapor deposition method is 450℃~650℃; (2) The deposition time of the chemical vapor deposition method is 0.5h~3h; (3) The carbon source gas used in the chemical vapor deposition method includes one or more of methane, acetylene and ethylene.

8. The application of a lithium-ion battery in which the lithium-replenishing material as described in any one of claims 1 to 3 or the lithium-replenishing material prepared by the preparation method described in any one of claims 4 to 7 is used.

9. A lithium-ion battery, characterized in that, The invention includes a positive electrode sheet, which comprises a positive current collector and a positive active layer. The positive active layer contains a positive active material and a lithium supplement material according to any one of claims 1 to 3, or the lithium supplement material prepared by any one of claims 4 to 7.

10. The lithium-ion battery according to claim 9, characterized in that, One or more of the following conditions must be met: (1) In the positive electrode active layer, based on the total mass of the positive electrode active material, the amount of lithium supplement material added is 0.5%~5%; (2) The positive electrode active material includes Li z (Ni x Co y M 1 1-x-y O2 and Li β Fe α M 2 (1-α) One or more of PO4; Among them, M 1 Including Mn and / or Al, 0 <x<1,0<y<1,1≤z≤1.1; M 2 It includes one or more of Ti, V, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, and Sr, with 0.2≤α≤1 and 1≤β≤1.1.

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