Lithium supplementing material, preparation method thereof, positive electrode and secondary battery

Abstract

This application belongs to the field of secondary battery technology, and particularly relates to a lithium replenishment material and its preparation method, a positive electrode, and a secondary battery. The lithium replenishment material of this application includes materials with the chemical formula Li. x M y O z The lithium-rich component, wherein 1 < x < 10, 0 < y < 6, 0 < z < 13, and M is selected from at least one element from Groups IB to VIIIB, IIIA, and IVA, has a one-dimensional structure and a nanometer size in at least one direction. The lithium-rich material of this application has a one-dimensional structure, which can reduce the Li content in the lithium-rich material. + This increases transmission distance and reduces the internal resistance of lithium-ion materials, thereby improving the capacity and cycle life of lithium-ion batteries; moreover, the Li-type structure of this structure... x M y O z It is easier to combine with coating materials, especially conductive coating materials, to obtain a coating layer with good uniformity, thereby improving the stability of the lithium supplementation material structure.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of secondary batteries, and particularly relates to a lithium supplementing material, a preparation method thereof, a positive electrode and a secondary battery. BACKGROUND

[0002] With the enhancement of people's awareness of environmental protection and energy crisis, secondary batteries, specifically lithium ion batteries, as a kind of green and environmentally friendly energy storage technology, are more and more popular. Lithium ion batteries are widely used due to their high working voltage, relatively small self-discharge level, super-long cycle life and other characteristics. With the popularization of new energy electric vehicles and energy storage, people's requirements for the energy density of lithium ion batteries are also increasing.

[0003] During the first charging process of a lithium ion battery, an SEI film (solid electrolyte interface film) is generated, and a large amount of Li + is consumed, which greatly reduces the capacity of Li + . During the first discharge, the Li + deintercalated from the negative electrode is much smaller than the Li + deintercalated from the positive electrode during charging, which reduces the coulombic efficiency and directly affects the cycle life and energy density of the lithium ion battery. To solve this problem, the loss of this part of irreversible capacity can be eliminated by the method of supplementing lithium to the positive electrode, and the energy density and other electrical properties of the battery can be improved. However, the currently prepared lithium supplementing materials are prone to agglomeration, have a slow lithium ion transfer rate, a high resistivity, an unstable surface interface and a high residual alkali degree. The existing coating technology is difficult to form a uniform and complete coating layer structure on the surface of the lithium supplementing material, and therefore, water and carbon dioxide in the external environment can easily corrode the lithium supplementing material and destroy the structure of the lithium supplementing material. When the lithium supplementing material is applied to a battery, the lithium supplementing material is prone to react with a solvent such as NMP (N-methyl pyrrolidone). SUMMARY

[0004] The application aims to provide a lithium supplementing material, a preparation method thereof, a positive electrode and a secondary battery, and aims to solve the problems of slow Li + transfer rate and difficult coating of the lithium supplementing material.

[0005] To achieve the above application purposes, the technical solutions adopted by the application are as follows.

[0006] In a first aspect, the application provides a lithium supplementing material, which comprises a lithium-rich component with a chemical formula of Li x M y O z , wherein 1 < x < 10, 0 < y < 6, 0 < z < 13, and M is selected from at least one of group IB to group VIIIB elements, group IIIA elements and group IVA elements, the lithium-rich component has a one-dimensional structure, and the lithium-rich component has a nanometer size in at least one direction.

[0007] According to the first aspect of the application, the lithium supplementing material has a one-dimensional structure. On the one hand, the one-dimensional structure has a shortest distance in a certain dimension, and Li + The shortest distance can preferably be used for transmission, and thus the one-dimensional structure can reduce the Li + transport distance in the lithium supplementing material, thereby reducing the internal resistance of the lithium supplementing material and improving the capacity and cycle life of the lithium ion battery; on the other hand, the Li x M y O z is more easily combined with the coating material, especially the coating material having electrical conductivity, to obtain a coating layer with good uniformity, thereby improving the stability of the structure of the lithium supplementing material.

[0008] In some embodiments, the one-dimensional structure includes one or more of a nanorod structure, a nanowire structure, a nanotube structure, and a nanobelt structure.

[0009] In some embodiments, the average diameter of the lithium-rich component ranges from 10 nm to 100 nm. The size of the lithium-rich component is crucial for shortening the Li + transport distance. If the diameter is too small, agglomeration is prone to occur, and the dispersibility is poor; if the diameter is too large, the Li + inside needs to pass through a longer path to contact the coating layer, the electrode active material, the electrolyte, and the like, thereby increasing the internal resistance of the lithium supplementing, reducing the capacity and cycle life of the lithium ion battery.

[0010] In some embodiments, the aspect ratio of the lithium-rich component ranges from 100:1 to 1000:1. The smaller the aspect ratio of the lithium-rich component, the smaller the length and the larger the diameter, which is not conducive to accelerating the Li + transport rate; the larger the aspect ratio of the lithium-rich component, the larger the length and the smaller the diameter, which is prone to poor dispersibility. The lithium-rich component in a suitable aspect ratio range can accelerate the Li + transport rate while having good dispersibility.

[0011] In some embodiments, the crystallinity of the lithium-rich component is greater than or equal to 80%. The higher the crystallinity, the better the morphology of the lithium-rich component, and the easier it is to play the special role of the one-dimensional structure, shorten the Li + transport distance, and improve the capacity and cycle life of the lithium ion battery.

[0012] In some embodiments, the group IB to VIIIB element is selected from at least one of Zr, Fe, Ni, Mn, Co, Cu, and Zn; the group IIIA element includes Al; and the group IVA element includes at least one of Si and Sn.

[0013] In some embodiments, the chemical formula of the lithium-rich component includes Li8ZrO6, Li5FeO4, Li6MnO4, Li6CoO4, and Li2Ni. 0.5 Cu 0.5 At least one of O2 and Li2MnO2.

[0014] In some embodiments, the lithium replenishment material further includes a conductive coating layer covering the surface of the lithium-rich component. Because the lithium-rich component of this application has a one-dimensional structure, it can effectively combine with various coating materials to form a coating layer on the lithium-rich component, effectively preventing structural damage caused by environmental degradation. Simultaneously, after the coating layer is formed on the lithium-rich component, the lithium replenishment material as a whole still maintains a one-dimensional nanorod structure, which can reduce the Li content in the lithium replenishment material. + Increase transmission distance and reduce the internal resistance of lithium replenishment materials, thereby improving the capacity and cycle life of lithium-ion batteries.

[0015] In some embodiments, the mass of the conductive coating layer is 0.5% to 10% of the mass of the lithium-rich component.

[0016] In some embodiments, the average thickness of the conductive coating layer ranges from 1 to 200 nm.

[0017] In some embodiments, the conductive coating layer covers more than 50% of the surface area of ​​the lithium-rich component. Increasing the coating area percentage is more beneficial for improving the capacity and cycle performance of the lithium-ion battery.

[0018] In some embodiments, the conductive coating layer includes at least one selected from the following: a carbon coating layer, a metal oxide coating layer, a metal fluoride coating layer, a metal carbide coating layer, and a lithium compound coating layer. Such coating layers can bind to lithium-rich components and are conductive, thus contributing to improved capacity and cycle performance of lithium-ion batteries.

[0019] Secondly, this application provides a method for preparing a lithium supplement material, comprising the following steps:

[0020] A precursor solution containing an M source and a surfactant is provided, and an M precursor with a one-dimensional structure is obtained by hydrothermal reaction treatment; wherein the M source contains at least one element selected from Group IB to VIIIB, Group IIIA, and Group IVA.

[0021] The lithium source is mixed with the M precursor and sintered to obtain a product containing the chemical formula Li. x M y O z A lithium-rich component for lithium supplementation; wherein 1 < x < 10, 0 < y < 6, 0 < z < 13; the lithium-rich component has a one-dimensional structure and the lithium-rich component has a nanoscale size in at least one direction.

[0022] According to the preparation method of the second aspect of the present application, the M source is subjected to a hydrothermal reaction under the action of a surfactant to form an M precursor with stable morphology, good dispersibility and one-dimensional structure. After lithium source and the M precursor with one-dimensional structure are co-sintered, a lithium-rich component Li x M y O z The preparation method is simple, and the obtained product has high crystallinity, stable morphology, and good dispersibility.

[0023] In some embodiments, the temperature of the hydrothermal reaction treatment is 90-140°C, and the time length of the hydrothermal reaction treatment is 1-10 h. In the hydrothermal reaction, the precursor solution containing the M source and the surfactant generates self-pressure at high temperature in a sealed environment, thereby promoting the reaction.

[0024] In some embodiments, the concentration of the M source in the precursor solution is 0.0001-0.1 g / mL. At a suitable concentration, the M source can be effectively stabilized and dispersed by the surfactant, and a one-dimensional structure M precursor with stable structure and good dispersibility is formed by reaction.

[0025] In some embodiments, the mass ratio of the M source to the surfactant is 1:3-30. In the process of converting the M source into a one-dimensional structure M precursor by hydrothermal reaction, the surfactant can play a structure guiding role and has a stabilizing effect on the formed one-dimensional structure M precursor, effectively reducing agglomeration. Too low or too high mass of the surfactant can affect the formation of the one-dimensional structure of the M precursor, and affect the dispersibility and structural stability of the M precursor.

[0026] In some embodiments, the M source includes at least one of an M-containing sulfate, an M-containing oxychloride, an M-containing carbonate, an M-containing nitrate, an M-containing chloride, an M-containing sulfate hydrate, an M-containing oxychloride hydrate, an M-containing carbonate hydrate, an M-containing nitrate hydrate, and an M-containing chloride hydrate. These M sources are subjected to a hydrothermal reaction in the presence of a crystal growth directing agent, and the obtained M precursor with one-dimensional nanorod structure can be at least one of an oxide of M and / or a hydrate thereof, a hydroxide of M and / or a hydrate thereof.

[0027] In some embodiments, the surfactant includes at least one of a fatty acid, a fatty acid salt, a fatty amine, and an amide.

[0028] In a third aspect, the present application provides a positive electrode including a current collector and a positive electrode active layer, the positive electrode active layer being combined with the current collector, and the positive electrode active layer containing the above-mentioned lithium supplementing material or the lithium supplementing material prepared by the above-mentioned method.

[0029] The lithium supplement material has a special one-dimensional structure, which can reduce the Li + The transmission distance is short, the internal resistance is low, and the capacity and cycle life of the lithium ion battery can be effectively improved after being applied to manufacture the positive electrode.

[0030] In a fourth aspect, the application provides a secondary battery, comprising a positive electrode and a negative electrode, wherein the positive electrode comprises the lithium supplement positive electrode according to the third aspect.

[0031] During the operation of the secondary battery comprising the positive electrode, Li + The transmission distance is short, the internal resistance is low, and the capacity and cycle life of the lithium ion battery can be effectively improved after being applied to manufacture the positive electrode. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0033] Figure 1 is a scanning electron microscope (SEM) of the lithium supplement material provided by the embodiment 1 of the application;

[0034] Figure 2 is an X-ray diffraction spectrum (XRD) of the lithium supplement material provided by the embodiment 1 of the application. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects of the application more clearly understood, the following will further describe the application in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the application, and are not used to limit the application.

[0036] In the application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can mean that A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents that the associated objects before and after it are in an "or" relationship.

[0037] In this application, "at least one" means one or more, "multiple" means two or more. "At least one of the following" or similar expressions means any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0038] It should be understood that in various embodiments of the present application, the size of the sequence of processes does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence, and the execution order of the processes should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0039] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0040] The weight of the related components mentioned in the specification of the embodiments of the present application can not only refer to the specific content of each component, but also represent the weight ratio relationship between each component, therefore, as long as the content of the related components in the specification of the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass mentioned in the specification of the embodiments of the present application can be μg, mg, g, kg and other mass units commonly known in the chemical field.

[0041] The first aspect of the embodiments of the present application provides a lithium supplementing material, which comprises a lithium-rich component with a chemical formula of Li x M y O z , wherein 1 < x < 10, 0 < y < 6, 0 < z < 13, M is selected from at least one of group IB to group VIIIB elements, group IIIA elements and group IVA elements, the lithium-rich component has a one-dimensional structure, and the lithium-rich component has a nanometer size in at least one direction.

[0042] In the present application, group IB to group VIIIB elements refer to elements in columns 3-12 of the periodic table, including elements of group IIIB, group IVB, group VB, group VIB, group VIIB, group VIII and group IB, group IIB, which are transition metal elements. Group IIIA elements and group IVA elements refer to elements in columns 13 and 14 of the periodic table, which include metal elements and non-metal elements. These elements can form oxides with lithium.

[0043] In the present application, the one-dimensional structure of the lithium-rich component means that the lithium-rich component extends in the positive and negative directions of the first dimension and the second dimension in the three-dimensional space. The size of the lithium-rich component in the first dimension is in the nanometer scale, and the size of the lithium-rich component in the second dimension is greater than the size of the lithium-rich component in the first dimension. The first dimension can be referred to as the lateral direction or the radial direction, and the second dimension can be referred to as the longitudinal direction or the axial direction. The angle between the first dimension and the second dimension is greater than 0° and less than or equal to 90°. The cross-sectional shape of the lithium-rich component in the first dimension and the second dimension can be a regular circle, an ellipse, a rectangle, a square, a polygon, or various irregular shapes, respectively.

[0044] According to the lithium supplementing material of the first aspect of the application, the lithium supplementing material has a one-dimensional structure. On the one hand, the one-dimensional structure has the shortest distance in a certain dimension, and the Li + The shortest distance can be preferably used for transmission, and thus the one-dimensional structure can reduce the Li + transport distance and reduce the internal resistance of the lithium supplementing material, thereby improving the capacity and cycle life of the lithium ion battery; on the other hand, the Li x M y O z The Li is more easily combined with the coating material, especially the coating material having electrical conductivity, to obtain a uniform coating layer, thereby improving the stability of the structure of the lithium supplementing material.

[0045] In some embodiments, the one-dimensional structure includes one or more of a nanorod structure, a nanowire structure, a nanotube structure, and a nanobelt structure. Generally, a one-dimensional structure with a small aspect ratio (the ratio of length to diameter, or the ratio of axial dimension to radial dimension, or the ratio of the longest dimension to the shortest dimension) is referred to as a nanorod, and a one-dimensional structure with a large aspect ratio is referred to as a nanowire. So far, there is no uniform standard between nanorods and nanowires, and generally, a length less than 1 μm is referred to as a nanorod, and a length greater than 1 μm is referred to as a nanowire, also called a nanowire. The nanotube structure is a structure with a radial dimension in the nanometer scale, an axial dimension in the micrometer scale, and a hollow interior. The nanobelt structure has a larger size in the radial direction than the nanowire structure and is flat in the axial direction.

[0046] In some embodiments, the average diameter of the lithium-rich component ranges from 10 nm to 100 nm, and in some embodiments, the average diameter ranges from 10 nm to 50 nm. The average diameter of the lithium-rich component refers to the average size in the radial direction. For the case of a circular radial cross-section, the average diameter of the cross-section is the actual average diameter of the circle. For the case of a non-circular radial cross-section, such as a triangle, a quadrilateral, a polygon, an ellipse, or other irregular shapes, the average diameter of the cross-section is the average equivalent diameter of the cross-section. The diameter of the lithium-rich component is used to shorten the Li +The transmission distance is crucial. If the diameter is too small, agglomeration is prone to occur and the dispersibility is poor; if the diameter is too large, the internal Li + It needs to pass through a longer path to contact the coating layer, electrode active material, electrolyte, etc., which increases the internal resistance of lithium supplement, and reduces the capacity and cycle life of the lithium ion battery.

[0047] In some embodiments, the length-diameter ratio of the lithium-rich component ranges from (100-1000): 1; in some embodiments, the length-diameter ratio ranges from (300-1000): 1; in other embodiments, the length-diameter ratio ranges from (300-500): 1. In this application, the length-diameter ratio refers to the ratio of the length to the diameter of the lithium-rich component, i.e., the ratio of the axial dimension to the radial dimension. The length-diameter ratio is also sometimes referred to as the aspect ratio. The smaller the length-diameter ratio of the lithium-rich component, the smaller the length and the larger the diameter, which is not conducive to speeding up the Li + The transmission rate; the larger the length-diameter ratio of the lithium-rich component, the larger the length and the smaller the diameter, which is prone to poor dispersibility.

[0048] In some embodiments, 1≤x≤8, 1≤y≤5, 1≤z≤10. x, y, and z can be independently selected from integers or non-integers.

[0049] In some embodiments, the crystallinity of the lithium-rich component is ≥80%, and in some embodiments, the crystallinity of the lithium-rich component can reach 90% or more. The crystallinity refers to the percentage of crystalline phase in the material, which can be fitted by using the diffraction peak in the X-ray diffraction pattern (XRD) to obtain the crystallinity of the material. In the XRD results of the material, the higher the crystallinity, the sharper the diffraction peak. The higher the crystallinity, the better the one-dimensional structural morphology of the lithium-rich component, and the easier it is to play the special role of the one-dimensional structure, shorten the Li + transmission distance, and improve the capacity and cycle life of the lithium ion battery.

[0050] In some embodiments, the elements of groups IB to VIIIB are selected from at least one of Zr, Fe, Ni, Mn, Co, Cu, and Zn; the elements of group IIIA include Al; the elements of group IVA include at least one of Si and Sn. In some embodiments, M is selected from at least one of Zr, Fe, Ni, Mn, Co, and Cu.

[0051] In some embodiments, the chemical formula of the lithium-rich component includes Li8ZrO6, Li5FeO4, Li6MnO4, Li6CoO4, Li2Ni 0.5 Cu 0.5 O2, Li2MnO2, and the like.

[0052] In some embodiments, the lithium supplement material further comprises an electrically conductive coating layer coated on the surface of the lithium-rich component. The lithium-rich component of the present application has a one-dimensional structure, which can be well combined with various electrically conductive coating materials to form an electrically conductive coating layer on the surface of the lithium-rich component, which can effectively prevent the lithium-rich component from being destroyed and eroded by the external environment, thereby preventing the destruction of the structure. At the same time, after forming the coating layer on the lithium-rich component, the lithium supplement material as a whole still maintains a one-dimensional structure, which can reduce the Li + transmission distance, reduce the internal resistance of the lithium supplement material, and thus improve the capacity and cycle life of the lithium ion battery.

[0053] In some embodiments, the mass of the electrically conductive coating layer is 0.5% to 10% of the mass of the lithium-rich component, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0054] In some embodiments, the average thickness of the electrically conductive coating layer ranges from 1 to 200 nm, and in some embodiments, the average thickness of the coating layer ranges from 1 to 50 nm, for example, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 100 nm, 250 nm, 200 nm, etc.

[0055] In some embodiments, the coating area ratio of the electrically conductive coating layer on the surface of the lithium-rich component is greater than 50%; in some embodiments, the coating area ratio is greater than or equal to 60%; in some embodiments, the coating area ratio can reach 90% or more, or even 100%. The coating area ratio of the electrically conductive coating layer on the surface of the lithium-rich component is the ratio of the coating area of the electrically conductive coating layer on the surface of the lithium-rich component to the total area of the surface of the lithium-rich component. For example, the coating area ratio of the electrically conductive coating layer on the surface of the lithium-rich component is greater than 50%, which means that more than 50% of the total area of the surface of the lithium-rich component is covered by the electrically conductive coating layer. With the increase of the coating area ratio, the capacity and cycle performance of the lithium ion battery will be improved.

[0056] In some embodiments, the electrically conductive coating layer comprises at least one of a carbon coating layer, a metal oxide coating layer, a metal fluoride coating layer, a metal carbide coating layer, and a lithium compound coating layer. Such coating layers can be combined with the lithium-rich component and have electrical conductivity, which helps to improve the capacity and cycle performance of the lithium ion battery.

[0057] In some embodiments, the electrically conductive coating layer is a carbon coating layer. The carbon coating layer can be formed by using carbon nanotubes, carbon nanofibers, carbon nanospheres, nanoporous carbon, graphite, graphene, etc. Compared with other coating materials, carbon materials are easier to combine with one-dimensional structure materials to form a carbon coating layer, and carbon materials have better electrical conductivity, better compatibility when used with positive electrode materials, and hydrophobic properties (which can prevent water vapor in the external environment from reacting with the lithium-rich component).

[0058] The second aspect of the embodiments of the present application provides a preparation method of a lithium supplementing material, comprising the following steps:

[0059] A precursor solution containing an M source and a surfactant is provided, and an M precursor with a one-dimensional structure is obtained through a hydrothermal reaction treatment; the M source contains at least one element selected from the group consisting of IB to VIIIB group elements, IIIA group elements and IVA group elements;

[0060] A lithium source is mixed with the M precursor, and a sintering treatment is performed to obtain a lithium supplementing material containing a lithium-rich component with a chemical formula of Li x M y O z ; wherein 1 < x < 10, 0 < y < 6 and 0 < z < 13; the lithium-rich component has a one-dimensional structure, and the lithium-rich component has a nanoscale size in at least one direction.

[0061] According to the preparation method of the second aspect of the present application, the M source is subjected to a hydrothermal reaction under the action of the surfactant to form an M precursor with a stable morphology structure, good dispersibility and a one-dimensional structure. The lithium source and the M precursor with a one-dimensional structure are sintered together to form a lithium-rich component Li x M y O z with a one-dimensional structure. The preparation method is simple, and the obtained product has high crystallinity, a stable morphology structure and good dispersibility.

[0062] In some embodiments, the temperature of the hydrothermal reaction treatment is 90-140°C; in some embodiments, the temperature of the hydrothermal reaction treatment is 110-130°C, such as 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, etc.; the time length of the hydrothermal reaction treatment is 1-10h, and in some embodiments, the time length of the hydrothermal reaction treatment is 2-5h, such as 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, etc. In the hydrothermal reaction, the precursor solution containing the M source and the surfactant generates self-pressure at high temperature in a sealed environment, thereby promoting the reaction.

[0063] In some embodiments, the concentration of the M source in the precursor solution is 0.0001-0.1g / mL; in some embodiments, the concentration of the M source in the precursor solution is 0.001-0.05g / mL; in other embodiments, the concentration of the M source in the precursor solution is 0.003-0.02g / mL. Under a suitable concentration, the M source can be effectively stabilized and dispersed by the surfactant to form an M precursor with a stable structure and good dispersibility.

[0064] In some embodiments, the mass ratio of the M source to the surfactant is 1:3-30; in some embodiments, the mass ratio of the M source to the surfactant is 1:3-20; in some other embodiments, the mass ratio of the M source to the surfactant is 1:3-15. In the process of converting the M source into the M precursor with one-dimensional structure through hydrothermal reaction, the surfactant can play a role of structure guiding and at the same time has a stabilizing effect on the one-dimensional structure M precursor formed, effectively reducing agglomeration. Too low or too high mass of the surfactant can affect the formation of the one-dimensional structure of the M precursor, the dispersibility and the structural stability of the M precursor.

[0065] In some embodiments, the M source includes at least one of M-containing sulfate, M-containing oxychloride, M-containing carbonate, M-containing nitrate, M-containing chloride, M-containing sulfate hydrate, M-containing oxychloride hydrate, M-containing carbonate hydrate, M-containing nitrate hydrate, M-containing chloride hydrate. For example, for the case where M is Zr, the M source includes at least one of ZrSO4·2H2O, ZrOCl2·8H2O, Zr(CO3)2, Zr(NO3)4, ZrCl4. These M sources are subjected to hydrothermal reaction in the presence of the surfactant, and the M precursor with one-dimensional structure obtained can be at least one of an oxide of M and / or a hydrate thereof, a hydroxide of M and / or a hydrate thereof.

[0066] In some embodiments, the surfactant includes at least one of a fatty acid, a fatty acid salt, a fatty amine, an amide. In the process of hydrothermal reaction, one surfactant can be used alone or multiple surfactants can be used together. In the process of synthesizing the M precursor with one-dimensional structure, the fatty acid, the fatty acid salt, the fatty amine can play a role of stabilizer, effectively preventing agglomeration of the nanoparticles in the system, and the amide can promote the formation of one-dimensional structure.

[0067] wherein the fatty acid includes at least one of an alkyl acid with a C atom number of 2-30 and an alkenyl acid with a C atom number of 2-30; in some embodiments, the fatty acid includes at least one of an alkyl acid with a C atom number of 2-20 and an alkenyl acid with a C atom number of 2-20. In some embodiments, the fatty acid includes at least one of oleic acid, acetic acid, octanoic acid.

[0068] The fatty acid salt includes an alkali metal salt, an alkaline earth metal salt, a transition metal salt, an ammonium salt, etc. of the fatty acid, wherein the alkali metal salt is at least one of a lithium salt, a sodium salt, a potassium salt, the alkaline earth metal salt is at least one of a magnesium salt, a calcium salt, a barium salt, and the transition metal salt is at least one of an iron salt, a zinc salt, a copper salt, a nickel salt, a silver salt.

[0069] The fatty amine includes at least one of an alkyl amine with a C-atom number of 2-30, an alkenyl amine with a C-atom number of 2-30; in some embodiments, the fatty amine includes at least one of an alkyl amine with a C-atom number of 2-20, an alkenyl amine with a C-atom number of 2-20. In some embodiments, the fatty amine includes at least one of oleyl amine, dodecyl amine.

[0070] The amide includes a substance with a structural formula of R1C(O)NR2(R3), wherein R1 is selected from any one of H, a substituted or unsubstituted alkyl with a C-atom number of 1-20, a substituted or unsubstituted alkenyl with a C-atom number of 1-20, R2 and R3 are independently selected from H, a substituted or unsubstituted alkyl with a C-atom number of 1-20. 1～20 1～3 In some embodiments, the amide includes at least one of urea (carbamide), N,N-dimethylacetamide, stearic acid amide.

[0071] In some embodiments, the surfactant includes a combination of the fatty acid, the fatty amine, and the amide. In this combination, the mass ratio of the fatty acid, the fatty amine, and the amide can be set as 1:(0.5-4):(0.01-1); in some embodiments, the mass ratio of the fatty acid, the fatty amine, and the amide is 1:(1-3):(0.1-0.3); in some embodiments, the mass ratio of the fatty acid, the fatty amine, and the amide is 1:(1-2):(0.05-0.2). The simultaneous use of the fatty acid, the fatty amine, and the amide can synthesize a one-dimensional structure M precursor with stable structure and good dispersibility.

[0072] For the convenience of actual operation, in the case where the surfactant includes a combination of the fatty acid, the fatty amine, and the amide, the mass of each component can also be configured according to the following ratio: the mass ratio of the M source to the fatty acid is 1:1-10, the mass ratio of the M source to the fatty amine is 1:1-20, and the mass ratio of the M source to the amide is 1:0.1-2; in some embodiments, the mass ratio of the M source to the fatty acid is 1:2-6, the mass ratio of the M source to the fatty amine is 1:3-10, and the mass ratio of the M source to the amide is 1:0.5-1.

[0073] In some embodiments, the surfactant includes a combination of oleic acid, oleyl amine, and urea. The simultaneous use of oleic acid, oleyl amine, and urea can synthesize a one-dimensional structure M precursor with stable structure and good dispersibility.

[0074] In some embodiments, the precursor solution containing the M source and the surfactant further contains a base. In the process of synthesizing the one-dimensional structure M precursor, the base can promote the formation of the one-dimensional structure and has the same effect as the above-mentioned amide. In the case where the surfactant contains the amide, the base can be added to enhance the formation of the one-dimensional structure; in the case where the surfactant does not contain the amide, the base can be added to promote the formation of the one-dimensional structure. In some embodiments, the base includes at least one of sodium hydroxide, potassium hydroxide, and ammonia.​

[0075] In some embodiments, the precursor solution contains a solvent, which includes at least one of water, phosphate buffer, and acetic acid buffer. Such solvent can well disperse or dissolve the M source and the surfactant, and meanwhile does not participate in the reaction.

[0076] In some embodiments, the sintering treatment is performed at a temperature of 600-850℃ in an inert atmosphere for 2-20h. In some embodiments, the sintering treatment is performed at a temperature of 600-700℃ in an inert atmosphere for 6-16h. Exemplary sintering treatment temperatures include 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, etc., and exemplary sintering treatment time lengths include 2h, 4h, 6h, 8h, 10h, 12h, 14h, 15h, 16h, 18h, 20h, etc., and exemplary inert atmospheres include nitrogen atmosphere and / or helium atmosphere. By sintering at a high temperature in an inert atmosphere, the lithium element and the M precursor are mixed well and doped with each other, and the Li x M y O z .

[0077] In some embodiments, the lithium source includes at least one of lithium oxide, lithium hydroxide, lithium carbonate, lithium oxalate, and lithium sulfate.

[0078] In some embodiments, after the sintering treatment, the product of the sintering treatment is mixed with a coating material, and then subjected to a secondary sintering treatment to obtain the lithium supplement material. The secondary sintering treatment is performed at a temperature of 500-700℃, such as 500℃, 550℃, 600℃, 650℃, 700℃, etc., for a time length of 3-6h, such as 3h, 4h, 5h, 6h, etc. The secondary sintering treatment is performed in an inert atmosphere, such as in a nitrogen atmosphere and / or a helium atmosphere. The product of the sintering treatment, i.e., the lithium-rich component Li x M y O z , is mixed with the coating material and subjected to the secondary sintering treatment, and the coating material can form a coating layer on the surface of the lithium-rich component.

[0079] In some embodiments, the lithium-rich component and the coating material are configured in a ratio of 0.5%-10% of the mass of the coating material to the mass of the lithium-rich component.

[0080] The third aspect of the embodiments of the present application provides a lithium supplement positive electrode, which includes a current collector and a positive electrode active layer. The positive electrode active layer is combined with the current collector, and contains the lithium supplement material described above or prepared by the method described above.

[0081] The lithium supplement material has a special one-dimensional structure, which can reduce the Li + The transmission distance is short, the internal resistance is low, and after being applied to the preparation of the positive active layer in the positive electrode, the capacity and cycle life of the lithium ion battery can be effectively improved.

[0082] In some embodiments, the positive active layer further comprises a positive electrode material, and the positive electrode material and the lithium supplement material jointly form the positive active layer and are combined with the current collector. The lithium supplement material of the present application can be used as a positive electrode material alone to prepare a positive electrode, or can be used together with a common positive electrode material to jointly form a positive active layer and a current collector. When the lithium supplement material is used together with the positive electrode material, the lithium supplement material is generally mixed with the lithium supplement material, and at the same time, necessary conductive agents, binders, etc. are mixed to form a positive electrode slurry, which is coated on the surface of the current collector. The mass ratio of the positive electrode material to the lithium supplement material can be determined according to actual needs and general techniques in the art, and the mass of the exemplary lithium supplement material is 1% to 10% of the mass of the positive electrode material. The positive electrode material can be at least one of lithium cobaltate, lithium manganate, lithium nickelate, nickel-cobalt-manganese ternary material, lithium borate, and lithium iron phosphate.

[0083] The fourth aspect of the present application provides a secondary battery comprising a positive electrode and a negative electrode, wherein the positive electrode comprises the above-mentioned lithium supplement positive electrode. During the charging and discharging process of the secondary battery, the positive electrode and the negative electrode form a loop. During the operation of the secondary battery comprising the above-mentioned lithium supplement positive electrode, Li + The transmission distance is short, the internal resistance is low, and after being applied to the preparation of the positive active layer in the positive electrode, the capacity and cycle life of the lithium ion battery can be effectively improved.

[0084] In some embodiments, the secondary battery further comprises an electrolyte and a separator stacked between the positive electrode and the negative electrode.

[0085] In some embodiments, the secondary battery comprises a lithium ion battery.

[0086] The specific embodiments will be described below.

[0087] Embodiment 1

[0088] The present embodiment provides a lithium supplement material, which has a chemical formula of Li8ZrO6, and a preparation method thereof comprises the following steps:

[0089] S1: ZrSO4·2H2O is mixed with oleic acid, oleylamine, urea, and water in a mass ratio of 1:3.25:5.12:0.76:50, the hydrothermal temperature is 120°C, and the reaction time is 4h, to obtain ZrO2·H2O with a one-dimensional nanorod structure.

[0090] S2: The ZrO2·H2O prepared in step S1 is mixed with lithium hydroxide with an average particle size of 15 μm at a molar ratio of 1:8, and reacted at 870°C for 8h under a nitrogen atmosphere to obtain a Li8ZrO6 lithium supplement material with a one-dimensional nanorod structure.

[0091] The morphology of the lithium supplement material is shown in Figure 1 As can be seen from the SEM image, the lithium supplement material of the present embodiment has a one-dimensional nanorod structure with complete morphology and good dispersibility. The aspect ratio of the lithium supplement material is 150.6, and the diameter is 13.2 nm.

[0092] The XRD spectrum of the lithium supplement material is shown in Figure 2 As can be seen from the XRD spectrum, the Li8ZrO6 lithium supplement material prepared has high purity and crystallinity, and the crystallinity is 95.0%.

[0093] Example 2

[0094] The present embodiment provides a lithium supplement material, which includes a lithium-rich component core with a chemical formula of Li8ZrO6 and a carbon coating layer on the lithium-rich component, and a preparation method thereof includes the following steps:

[0095] S1: Same as S1 in Example 1.

[0096] S2: Same as S2 in Example 1.

[0097] S3: Take 2g of Li8ZrO6, add 3% (0.06g) of carbon black by mass percentage, mix uniformly, and then heat at 500°C for 3h under a nitrogen atmosphere to obtain a Li8ZrO6 lithium supplement material with a carbon coating layer.

[0098] The lithium supplement material has an aspect ratio of 113.8, a diameter of 18.0 nm, a crystallinity of 95.4%, a carbon coating layer thickness of 2.4 nm, and a coating area ratio of 63.3%.

[0099] Example 3

[0100] The present embodiment provides a lithium supplement material, which has a chemical formula of Li8ZrO6, and a preparation method thereof includes the following steps:

[0101] S1: Same as S1 in Example 1, except that ZrSO4·2H2O is mixed with oleic acid, oleylamine, urea, and water at a mass ratio of 1:3.02:4.52:0.61:52, and the hydrothermal temperature is 100°C, and the reaction time is 5h.

[0102] S2: Same as S2 in Example 1.

[0103] The lithium supplement material has an aspect ratio of 155.7, a diameter of 10.4 nm, and a crystallinity of 94.8%.

[0104] Example 4

[0105] The lithium supplement material has a chemical formula of Li8ZrO6, and includes a lithium-rich component core and a carbon coating layer on the lithium-rich component. The preparation method includes the following steps:

[0106] S1: same as S1 in Example 3.

[0107] S2: same as S2 in Example 3.

[0108] S2: same as S3 in Example 2.

[0109] The lithium supplement material has an aspect ratio of 153.1, a diameter of 13.6 nm, a crystallinity of 94.3%, a carbon coating layer thickness of 2.10 nm, and a coating area ratio of 86.7%.

[0110] Example 5

[0111] The lithium supplement material has a chemical formula of Li5FeO4, and includes a lithium-rich component core and a carbon coating layer on the lithium-rich component. The preparation method includes the following steps:

[0112] S1: same as S1 in Example 3, except that ZrSO4·2H2O is replaced by Fe2(SO4)3·2H2O, and Fe2(SO4)3·2H2O is mixed with oleic acid, oleylamine, urea, and water in a mass ratio of 1:2.41:3.26:0.51:62.

[0113] S2: same as S2 in Example 3.

[0114] The lithium supplement material has an aspect ratio of 529.5, a diameter of 30.4 nm, and a crystallinity of 93.9%.

[0115] Example 6

[0116] The lithium supplement material has a chemical formula of Li5FeO4, and includes a lithium-rich component core and a carbon coating layer on the lithium-rich component. The preparation method includes the following steps:

[0117] S1: same as S1 in Example 3, except that ZrSO4·2H2O is replaced by Fe2(SO4)3·2H2O, and Fe2(SO4)3·2H2O is mixed with oleic acid, oleylamine, urea, and water in a mass ratio of 0.1:0.5:1:0.1:30.

[0118] S2: same as S2 in Example 3.

[0119] The aspect ratio of the lithium supplementing material was 50.1, the diameter was 6.7 nm, and the crystallinity was 85.7%.

[0120] Comparative Example 1

[0121] The comparative example provided a lithium supplementing material, which was different from Example 1 in that granular ZrO2·H2O with an average particle size of 20 μm was used as a raw material. The preparation method was as follows:

[0122] S1. Granular ZrO2·H2O and lithium hydroxide with an average particle size of 15 μm were mixed in a molar ratio of 1:8, and reacted at 780°C for 9 h in a nitrogen atmosphere to obtain a Li8ZrO6 lithium supplementing material.

[0123] It was found by testing that the Li8ZrO6 lithium supplementing material was granular and did not have a one-dimensional nanorod structure.

[0124] Comparative Example 2

[0125] The comparative example provided a lithium supplementing material, which was different from Example 2 in that granular ZrO2·H2O with an average particle size of 20 μm was used as a raw material. The preparation method was as follows:

[0126] S1. The same as S1 in Comparative Example 1.

[0127] S2: 2 g of the Li8ZrO6 lithium supplementing material prepared in step S1 was taken, 3% (0.06 g) of carbon black was added, and the mixture was uniformly mixed, and then was heated at 500°C for 3 h in a nitrogen atmosphere to obtain a Li8ZrO6 lithium supplementing material with a carbon coating layer.

[0128] It was found by testing that the carbon coating of the lithium supplementing material was poor in uniformity.

[0129] The physicochemical properties of the lithium supplementing materials in the examples and comparative examples were summarized in Table 1 below:

[0130] Table 1

[0131]

[0132]

[0133] Electrochemical performance test:

[0134] The lithium supplementing materials prepared in the examples and comparative examples were applied to lithium ion batteries, and the preparation steps of the lithium ion batteries specifically included:

[0135] Preparation of the positive electrode sheet: the lithium supplement material prepared in each example and the comparative example was mixed with lithium manganese iron phosphate at a mass ratio of 5:95, and the mixture was stirred for 2 h with a ball mill stirrer after mixing with SP (conductive carbon black), PVDF (polyvinylidene fluoride) and NMP (N-methyl pyrrolidone) at a mass ratio of 93.5:2.5:4:100 to obtain a positive electrode slurry; the prepared positive electrode slurry was added to an aluminum foil, uniformly scraped with a spatula, dried at 130°C, and then rolled to obtain a positive electrode sheet.

[0136] Assembly of the lithium ion battery: the positive electrode sheet prepared in step 1 was attached to the positive electrode metal shell with conductive glue, a lithium sheet was used as the negative electrode, a Celgard 2400 microporous membrane was used as the separator, and a 1.0 mol / L LiPF6 solution was used as the electrolyte, and the solvent of the electrolyte was a mixed solution of ethylene carbonate (EC), diethyl carbonate (DEC) and methyl ethyl carbonate (EMC) at a volume ratio of 1:1:1, and the lithium ion battery was assembled into a button type in a glove box.

[0137] The lithium ion battery containing the lithium supplement material of each example or comparative example assembled in step 2 was subjected to electrochemical performance test, and the test conditions were as follows:

[0138] First charge-discharge capacity: constant current constant voltage charging at 0.055C rate to 4.2V, and the cutoff current was 0.02C; standing for 10 min, constant current discharging at 0.055C rate to 2.0V;

[0139] Cycle performance: constant current constant voltage charging at 2C rate to 4.2V, and the cutoff current was 0.02C; standing for 10 min, constant current discharging at 2C rate to 2.0V, and the discharge capacity retention rate was calculated after 100 cycles;

[0140] The test results are as follows.

[0141] Table 2

[0142]

[0143] In table 2, the "lithium supplement amount" represents the increase amount of the first charge capacity of the lithium ion battery containing the lithium supplement material at 0.055C rate, compared with the first charge capacity of the lithium ion battery using lithium manganese iron phosphate as the positive electrode material alone at 0.055C rate. Under the same conditions, when lithium manganese iron phosphate is used as the positive electrode material alone, the first charge capacity of the lithium ion battery at 0.055C rate is 165.6 mAh·g -1 .

[0144] From tables 1 and 2, it can be seen that:

[0145] The first charge-discharge specific capacity, lithium supplement amount and cycle performance of the lithium battery prepared in Examples 1-6 are obviously superior to those of Comparative Examples 1 and 2. The reason is that the one-dimensional nanorod lithium supplement material of Examples 1-6 can accelerate the transmission rate of lithium ions, reduce the internal resistance of the battery and improve the electrochemical performance of the battery. Meanwhile, the lithium supplement amount of Examples 2 and 4 is higher than that of other examples because of the carbon coating layer which can improve the conductivity of the lithium supplement material.

[0146] Further analysis of Examples 2 and 4 shows that within a certain range, the smaller the diameter of the nanorod lithium supplement material, the larger the carbon coating area, which indicates that the nanorod lithium supplement material with small diameter is more easily combined with the coating material.

[0147] The lithium supplement amount of Comparative Example 2 is not obviously improved compared with Comparative Example 1 because the lithium supplement material does not have a nanorod structure, and the carbon coating uniformity is poor.

[0148] The above results show that the nanorod lithium supplement material can improve the transmission rate of lithium ions, reduce the internal resistance of the battery and also improve the uniformity of the coating material.

[0149] The above description is merely preferred embodiments of the present application but not to limit the present application. Any modification, equivalent replacement and improvement made within the principle and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A lithium supplementation material, characterized in that, Including the chemical formula Li x M y O z The lithium-rich component, wherein 1 < x < 10, 0 < y < 6, 0 < z < 13, and M is selected from at least one element from Groups IB to VIIIB, IIIA, and IVA, the lithium-rich component has a one-dimensional structure, the lithium-rich component has a nanometer size in at least one direction, and the crystallinity of the lithium-rich component is ≥ 80%; The preparation method of the lithium supplementation material includes the following steps: A precursor solution containing an M source and a surfactant is provided, and an M precursor with a one-dimensional structure is obtained by hydrothermal reaction treatment; wherein the M source contains at least one element selected from Group IB to VIIIB, Group IIIA, and Group IVA. The lithium source is mixed with the M precursor and sintered to obtain a product containing the chemical formula Li. x M y O z A lithium-rich component for lithium supplementation; wherein 1 < x < 10, 0 < y < 6, 0 < z < 13; the lithium-rich component has a one-dimensional structure and the lithium-rich component has a nanoscale size in at least one direction.

2. The lithium replenishment material according to claim 1, characterized in that, The one-dimensional structure includes one or more of the following: nanorod structure, nanowire structure, nanotube structure, and nanoribbon structure.

3. The lithium replenishment material according to claim 2, characterized in that, The average diameter of the lithium-rich component ranges from 10 to 100 nm. And / or, the aspect ratio of the lithium-rich component is in the range of (100~1000):1; And / or, the elements of Groups IB to VIIIB are selected from at least one of Zr, Fe, Ni, Mn, Co, Cu, and Zn; the elements of Group IIIA include Al; and the elements of Group IVA include at least one of Si and Sn.

4. The lithium replenishment material according to claim 3, characterized in that, The chemical formulas of the lithium-rich components include Li8ZrO6, Li5FeO4, Li6MnO4, Li6CoO4, and Li2Ni. 0.5 Cu 0.5 At least one of O2 and Li2MnO2.

5. The lithium replenishment material according to any one of claims 1 to 4, characterized in that, The lithium replenishing material also includes a conductive coating layer covering the surface of the lithium-rich component.

6. The lithium replenishment material according to claim 5, characterized in that, The mass of the conductive coating layer is 0.5% to 10% of the mass of the lithium-rich component; And / or, the average thickness of the conductive coating layer ranges from 1 to 200 nm; And / or, the conductive coating layer covers more than 50% of the surface area of ​​the lithium-rich component; And / or, the conductive coating layer includes at least one of a carbon coating layer, a metal oxide coating layer, a metal fluoride coating layer, a metal carbide coating layer, and a lithium coating layer.

7. The lithium replenishment material according to claim 1, characterized in that, The hydrothermal reaction treatment temperature is 90~140℃, and the hydrothermal reaction treatment duration is 1~10h; And / or, the concentration of the M source in the precursor solution is 0.0001~0.1 g / mL; And / or, the mass ratio of the M source to the surfactant is 1:(3~30); And / or, the M source includes at least one of the following: M-containing sulfate, M-containing oxychloride, M-containing carbonate, M-containing nitrate, M-containing chloride, M-containing sulfate hydrate, M-containing oxychloride hydrate, M-containing carbonate hydrate, M-containing nitrate hydrate, and M-containing chloride hydrate. And / or, the surfactant includes at least one of fatty acids, fatty acid salts, fatty amines, and amides.

8. A positive electrode, characterized in that, It includes a current collector and a positive electrode active layer, wherein the positive electrode active layer is bonded to the current collector, and the positive electrode active layer contains a lithium supplementation material as described in any one of claims 1 to 7.

9. A secondary battery, characterized in that, It includes a positive electrode and a negative electrode, wherein the positive electrode includes the positive electrode as described in claim 8.

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