Lithium manganate material and preparation method and application thereof

Abstract

The application relates to the technical field of secondary batteries, in particular to a lithium manganate material and a preparation method and application thereof. The lithium manganate material disclosed by the application comprises a matrix, the chemical formula of the matrix is (Li 1‑ x R x ) a Mn 2‑y M y O 4‑z X z , wherein 0 The lithium manganate material disclosed by the application can effectively reduce capacity attenuation in a cycle process and has good cycle stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to a lithium manganate material and a preparation method and application thereof. BACKGROUND

[0002] With the continuous development of the new energy industry, various markets, such as the two-wheeled electric vehicle market and the new energy vehicle market, have put forward more diversified demands for batteries. The positive electrode material is a key component of the battery and affects the capacity size and cycle stability of the battery.

[0003] In the process of charging and discharging of the battery, the active metal elements in the positive electrode material are dissolved and lost from the crystal lattice structure, so that the capacity of the battery is attenuated after multiple charging and discharging. SUMMARY

[0004] In view of the above problems, the present application provides a lithium manganate material and a preparation method and application thereof, which can alleviate the capacity attenuation problem caused by the dissolution of active metal elements during the use of the battery.

[0005] In a first aspect, the present application provides a lithium manganate material, comprising a matrix, the chemical formula of the matrix is (Li 1- x R x ) a Mn 2-y M y O 4-z X z , wherein 0

[0006] The lithium manganate material of the present application introduces a stable doping element R at the lithium site, and R is mainly distributed in the surface layer of the spinel lithium manganate, and the doping form is surface layer doping. Through this doping method, on the one hand, the stable R can be used to stabilize the surface layer oxygen atoms to inhibit the release of oxygen from the lattice, and at the same time, the dissolution channels of Mn 2+ are occupied, thereby inhibiting the dissolution and deposition of Mn 2+ , reducing the loss of Mn 2+ , and thus avoiding the capacity attenuation of spinel lithium manganate during the cycle process; on the other hand, compared with the conventional bulk doping method, the surface layer lithium site doping method can reduce the substitution of R elements for lithium sites and reduce the loss of active lithium, thereby avoiding the capacity loss caused by lithium site doping in the conventional bulk doping method. Therefore, the lithium manganate material of the present application can effectively reduce the capacity attenuation during the cycle process and has good cycle stability.

[0007] In some embodiments, the substrate comprises a surface layer region and a central region, wherein the distance between any point in the surface layer region and the surface of the substrate is greater than or equal to 0 and less than or equal to half of the longest particle size in the direction of the line connecting the point and the center point of the substrate multiplied by 20%; the distance between any point in the central region and the surface of the substrate is greater than or equal to half of the longest particle size in the direction of the line connecting the point and the center point of the substrate multiplied by 70% and less than or equal to half of the longest particle size in the direction of the line connecting the point and the center point of the substrate; and the content of R at the surface layer region is greater than the content of R at the central region.

[0008] In some embodiments, the valence of R is greater than or equal to +1 and less than or equal to +2. The valence of R is the same as or similar to that of lithium ions, has a greater tendency to occupy lithium sites, and does not cause serious damage to the crystal lattice after occupying lithium sites.

[0009] In some embodiments, R comprises at least one of K, Na, Mg, Cu, and Zn.

[0010] In some embodiments, 0 < x ≤ 0.1; in other embodiments, 0 < x ≤ 0.05. The occupation of lithium sites by R elements can effectively stabilize the material structure, control the manganese dissolution channel, inhibit manganese dissolution, and thus improve the cycle life. However, when the occupation of lithium sites by R elements is insufficient, the effect of improving the cycle life is not obvious, and when the occupation is too much, active lithium is lost, and the capacity of the material is greatly reduced.

[0011] In some embodiments, 0 ≤ y ≤ 0.3; in other embodiments, 0 ≤ y ≤ 0.25. The occupation of manganese sites by M elements can effectively stabilize the structure of lithium manganate material and improve the cycle performance of lithium manganate material. Too little M element doping cannot effectively stabilize the spinel lithium manganate structure, and too much M element doping will reduce the capacity of the material.

[0012] In some embodiments, M comprises at least one of transition metals, alkaline earth metals, alkali metals, and Al. Such metal elements can replace manganese sites to achieve doping. The occupation of manganese sites by some M elements can effectively stabilize the material structure and improve the cycle performance of the material.

[0013] In some embodiments, the transition metal comprises at least one of V, Tc, Co, Ni, Fe, Zn, Zr, Y, Nb, Mo, Ti, Cr, and W.

[0014] In some embodiments, the alkaline earth metal comprises at least one of Mg and Ca.

[0015] In some embodiments, the alkali metal comprises Li.

[0016] In some embodiments, X comprises one or more of a sixth main group element and a seventh main group element.

[0017] In some embodiments, the sixth main family element includes S.

[0018] In some embodiments, the seventh group element includes one or both of F and Cl.

[0019] Group 6, or Group VIA, includes nonmetals; Group 7, or Group VIIA, includes halogens. Elements such as sulfur (S) in Group 6 and fluorine (F) and chlorine (Cl) in Group 7 have negative valences, allowing them to incorporate oxygen ions and reduce their content. This stabilizes the bond between manganese (Mn) and oxygen in the matrix, mitigating the excessive oxygen release caused by anionic redox reactions in manganese-rich materials under high voltage, thus improving the material's gas production.

[0020] In some embodiments, the (Li) 1-x R x ) a Mn 2-y M y The volume average diameter (Dv50) of O4 is 2–30 μm. As a cathode material, the appropriate particle size of lithium manganese oxide is beneficial for lithium-ion insertion and extraction, which helps improve the rate performance and capacity of the battery. If the particle size is too small, the corresponding specific surface area is larger, the surface energy of the particles increases, and they are prone to agglomeration and side reactions with the electrolyte, increasing the internal resistance of the battery. Excessive energy will accumulate during charging and discharging, and the temperature will rise, leading to safety hazards. At the same time, too small a particle size will also lead to an increase in irreversible capacity and reduce the cycle performance of the battery. On the other hand, too large a particle size will weaken the lithium-ion insertion and extraction, resulting in a decrease in rate performance and capacity.

[0021] In some embodiments, the lithium manganese oxide material further comprises a coating layer disposed on the surface of the substrate. By providing a coating layer on the substrate surface, side reactions between the electrolyte and the spinel lithium manganese oxide material can be effectively suppressed, while simultaneously suppressing Mn... 2+ Dissolution through the coating layer, synergistic effect of manganese-doped M and lithium-doped R elements on intraparticle Mn 2+ The leaching inhibition effect can effectively suppress manganese leaching and improve the cycle life of materials.

[0022] In some embodiments, the coating layer accounts for a mass percentage greater than 0 and less than or equal to 5% of the lithium manganese oxide material; in other embodiments, the coating layer accounts for a mass percentage of 0.01% to 5% of the lithium manganese oxide material. An excessively high mass percentage of the coating layer will lead to a decrease in the material's capacity, while an excessively low mass percentage will prevent the coating layer from effectively inhibiting the dissolution of manganese through the coating layer.

[0023] In some embodiments, the cladding layer contains at least one of a transition group element, a group IA metal element, a group IIA element, a group IIIA element, a group IVA element, a group VA element, a group VIA element.

[0024] In some embodiments, the transition group element comprises at least one of Co, Ti, Nb, W, Zr.

[0025] In some embodiments, the group IA metal element comprises at least one of Li, Na, K.

[0026] In some embodiments, the group IIA element comprises at least one of Mg, Ca.

[0027] In some embodiments, the group IIIA element comprises at least one of Al, B.

[0028] In some embodiments, the group IVA element comprises at least one of C, Si.

[0029] In some embodiments, the group V element comprises N.

[0030] In some embodiments, the group VI element comprises S.

[0031] In a second aspect, the present application provides a preparation method of a lithium manganate material, comprising:

[0032] mixing a lithium source, a manganese source, an M source and an X source, and obtaining a spinel lithium manganate material doped with manganese by sintering treatment;

[0033] performing ion exchange treatment on the spinel lithium manganate material doped with manganese and an R source in a liquid environment, to obtain a lithium manganate material containing a matrix (Li 1-x R x ) a Mn 2-y M y O 4-z X z ; wherein 0

[0034] 0.95

[0035] The preparation method of the present application disperses the manganese site doped spinel lithium manganate material and the lithium site doped element R in a liquid environment, and relies on ion exchange to realize the substitution of the lithium site doped element R on the lithium element. Compared with the conventional sintering doping technology, the advantages of the method are: ① precise doping of the lithium site can be realized. Under the action of ion exchange, the doping element will tend to occupy the lithium site. ② surface layer doping can be formed. Ion exchange is from the outside to the inside, which can make ion exchange mainly occur in the surface layer of the manganese site doped spinel lithium manganate material, avoiding excessive occupation of the lithium site by R leading to capacity loss. ③ the method is simple and easy to operate, low in cost, and can be applied on a large scale.

[0036] In some embodiments, the sintering treatment temperature is 600-800℃; in other embodiments, the sintering treatment temperature is 700-800℃. After high-temperature sintering treatment, the lithium source and the manganese source form a spinel lithium manganate structure, and at the same time, the M element enters the manganese site of the spinel lithium manganate at high temperature to form a manganese site doped spinel lithium manganate material.

[0037] In some embodiments, the sintering treatment time is 8-20h; in other embodiments, the sintering treatment time is 10-20h.

[0038] In some embodiments, the sintering treatment is carried out in an oxygen-containing atmosphere. Carrying out sintering treatment in an oxygen-containing atmosphere can incorporate oxygen elements in the atmosphere into the crystal lattice to form a complete structure.

[0039] In some embodiments, the ion exchange treatment step comprises:

[0040] dispersing the manganese site doped spinel lithium manganate material in a solvent, adding the R source, and carrying out ion exchange treatment;

[0041] or dispersing the R source in a solvent, adding the manganese site doped spinel lithium manganate material, and carrying out ion exchange treatment;

[0042] or dispersing the manganese site doped spinel lithium manganate material and the R source in a solvent at the same time, and carrying out ion exchange treatment.

[0043] By carrying out ion exchange in a liquid environment, not only can the surface layer precise doping of R on the lithium site be realized, but also the ion exchange method is simple and easy to operate, the reaction conditions are mild, and it has good adaptability to different types of R sources.

[0044] In some embodiments, the solvent comprises at least one of water, ethanol, acetone, isopropanol, toluene, phosphate buffer, citric acid buffer, and acetic acid buffer.

[0045] In some embodiments, the solid-liquid ratio of the manganese-site doped spinel lithium manganate material to the solvent is 0.05-2 g / mL. In other embodiments, the solid-liquid ratio of the manganese-site doped spinel lithium manganate material to the solvent is 0.3-1 g / mL.

[0046] In some embodiments, the pH of the liquid environment is 6-10, and in other embodiments, the pH of the liquid environment is 7-9. A suitable pH can promote ion exchange of the R element with lithium ions, so that the R element occupies lithium sites on the surface.

[0047] In some embodiments, the ion exchange treatment temperature is 25-100°C, and in other embodiments, the ion exchange treatment temperature is 40-80°C. Within a certain range, the higher the ion exchange temperature, the faster the lithium site doping. However, to avoid loss of the solvent during ion exchange, the ion exchange temperature should not be too high. Compared with conventional sintering technology, the ion exchange temperature in the present application is lower. Without high temperature driving and ion exchange, the doping element R tends to occupy lithium sites, thereby achieving precise doping of lithium sites.

[0048] In some embodiments, the ion exchange treatment time is 1-10 h, and in other embodiments, the ion exchange treatment time is 3-6 h. Generally, the longer the ion exchange time, the higher the utilization rate of the R element, and the more lithium sites in the lithium manganate material occupied by the R element.

[0049] In some embodiments, after the step of ion exchange treatment of the manganese-site doped spinel lithium manganate material with the R source, the method further comprises a step of forming a coating layer on the substrate.

[0050] In some embodiments, the step of forming a coating layer on the substrate comprises mixing the substrate with a coating material, and forming the coating layer on the substrate by heat treatment. By forming a coating layer on the surface of the Li 1-x R x ) a Mn 2-y M y The formation of a coating layer on the surface of the Li 2+ dissolution through the coating layer, and the inhibition of Mn 2+ dissolution by the manganese-site doped M element and the lithium-site doped R element, can effectively inhibit manganese dissolution and improve the cycle life of the material.

[0051] In some embodiments, the heat treatment temperature is 300-600°C, and in other embodiments, the heat treatment temperature is 400-500°C. By high-temperature heat treatment, the coating material is combined with (Li 1-xR x ) a Mn 2-y M y O4are firmly combined together to form a surface protective layer, and the appropriate heat treatment temperature also reduces the generation of side reactions.

[0052] In some embodiments, the heat treatment time is 2-6h, and in other embodiments, the heat treatment time is 3-5h.

[0053] In a third aspect, the application provides a positive electrode sheet, comprising a current collector and an electrode active layer, the electrode active layer being combined with the current collector; wherein the electrode active layer contains the lithium manganate material as described above or prepared by the preparation method as described above.

[0054] The lithium manganate material of the application can be used as the active material of the positive electrode sheet, and in the cycle process, the surface layer lithium site doping element R in the lithium manganate material can be used to inhibit the elution and deposition of Mn 2+ , reduce the loss of Mn 2+ , thereby avoiding the capacity attenuation of spinel lithium manganate in the cycle process; and the lithium site doping in the lithium manganate material is less, which can reduce the loss of active lithium and avoid the capacity loss caused by lithium site doping.

[0055] In a fourth aspect, the application provides a secondary battery comprising the positive electrode sheet as described above.

[0056] The positive electrode sheet containing the lithium manganate material of the application and the negative electrode sheet are combined to form a secondary battery, and the obtained secondary battery has high capacity, high coulomb efficiency, and excellent cycle stability.

[0057] In a fifth aspect, the application provides an electric device comprising the secondary battery as described above.

[0058] The secondary battery of the application has high capacity, high coulomb efficiency, and excellent cycle stability, and the battery module can stably and efficiently provide electric energy, thereby providing power for various electric devices. The electric device includes but is not limited to information household appliances and new energy vehicles.

[0059] The above description is only a summary of the technical solutions of the application, in order to more clearly understand the technical means of the application, the specific embodiments of the application can be implemented in accordance with the content of the description, and in order to make the above and other purposes, features and advantages of the application more obvious and easy to understand, the following specific embodiments of the application are described. BRIEF DESCRIPTION OF DRAWINGS

[0060] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. In the drawings:

[0061] Figure 1 A schematic diagram of the surface and central portions of the lithium manganese oxide material matrix provided in the embodiments of this application;

[0062] Figure 2 This is a scanning electron microscope (SEM) image of the lithium manganese oxide material prepared in Example 1 of this application;

[0063] Figure 3 A cross-sectional scanning electron microscope (SEM) image of the lithium manganese oxide material prepared in Example 1 of the application;

[0064] Figure 4 The first charge-discharge curve of the lithium manganese oxide material prepared in Example 1 of this application at 0.1C is shown. Detailed Implementation

[0065] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0066] 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 pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0067] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0068] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0069] In the description of the embodiments of the present application, the term "and / or" is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0070] In the description of the embodiments of the present application, the term "at least one" means one or more, and "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 item or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can represent 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.

[0071] It should be understood that in various embodiments of the present application, the size of the sequence number of the above 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 each process should be determined according to its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0072] 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 proportional relationship between the weights of 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, etc. mass units commonly known in the chemical industry.

[0073] With the continuous development of the new energy industry, the market has put forward more diversified demands for the positive electrode materials of power batteries. Among the positive electrode materials of lithium ion power batteries, the commonly used materials include lithium cobaltate, spinel lithium manganate, lithium iron phosphate, and nickel-cobalt-manganese ternary material. Among them, spinel lithium manganate material is concerned due to its advantages of abundant resources, low cost, good safety, environmental friendliness, etc., and is considered as a promising positive electrode material, especially in the field of two-wheeled electric vehicles. However, the poor high-temperature storage performance and serious capacity decay during the cycle process of spinel lithium manganate hinder the exertion of its advantages. The main reason is the Jahn-Teller effect and active material loss caused by serious manganese dissolution during charging and discharging.

[0074] For this problem, strategies such as doping and coating are often used to improve it. For spinel lithium manganate, according to the doping position of the doped metal ion therein, the doping method has lithium site doping and manganese site (transition metal site) doping. Lithium site doped spinel lithium manganate can effectively inhibit manganese dissolution, and existing lithium site doping is mainly by mixing lithium manganate with raw materials containing doped metal ions and then sintering. However, there are two major problems with the existing lithium site doped spinel lithium manganate. On the one hand, the metal ions used for lithium site doping will enter both the lithium site and the manganese site during the doping process, and if the existing sintering technology is used, the doped metal ions will mostly enter the transition metal site in most cases, making it difficult to ensure the desired lithium site doping effect. On the other hand, the current lithium site doped spinel lithium manganate material has a bulk doping method, that is, the doped metal ions uniformly enter the entire bulk phase of the spinel lithium manganate particles, which will cause too many doped metal ions to occupy the lithium site, directly reducing the specific capacity of the material, and further causing capacity attenuation during the cycle process.

[0075] Therefore, in order to solve the problem of capacity attenuation of lithium manganate during the cycle process, the present application provides a lithium manganate material, comprising a matrix, the chemical formula of the matrix is (Li 1-x R x ) a Mn 2-y M y O 4-z X z , wherein 0 < x < 0.2, 0.95 < a < 1.2, 0 < y < 0.5, 0 < z < 0.1; R is a lithium site doping element, R is distributed in the surface layer of the matrix; M is a manganese site doping element; X is an oxygen site doping element.

[0076] In the present application, the term "lithium site doping" refers to the doping element occupying the position of lithium in the material lattice; the term "manganese site doping" refers to the doping element occupying the position of manganese in the material lattice. The term "surface layer" refers to the outermost layer of an object.

[0077] The lithium manganate material of the present application introduces a stable doping element R in the lithium site, and R is mainly distributed in the surface layer of the spinel lithium manganate, and the doping form is surface layer doping. Through this doping method, on the one hand, the stable surface layer oxygen atom R can be used to inhibit the release of lattice oxygen, and at the same time, the doping element R can occupy the dissolution channel of Mn 2+ , thereby inhibiting the deposition of Mn 2+ dissolution and reducing the loss of Mn 2+ , thereby avoiding the capacity attenuation of spinel lithium manganate during the cycle process; on the other hand, compared with the conventional bulk doping method, the surface layer lithium site doping method can reduce the substitution of R element for lithium site, reduce the loss of active lithium, and avoid the capacity loss caused by lithium site doping in the conventional bulk doping method. Therefore, the lithium manganate material of the present application can effectively reduce the capacity attenuation during the cycle process, and has good cycle stability.

[0078] In some embodiments, the matrix includes a surface portion and a central portion, wherein the distance between any point in the surface portion and the matrix surface is greater than or equal to 0 and less than or equal to 20% of half the longest particle size in the direction of the line connecting that point and the center point of the matrix; the distance between any point in the central portion and the matrix surface is greater than or equal to 70% of 70% of half the longest particle size in the direction of the line connecting that point and the center point of the matrix, and less than or equal to half the longest particle size in the direction of the line connecting that point and the center point of the matrix; the content of R at the surface portion is greater than the content of R at the central portion.

[0079] The center point of a particle is its equilibrium point, or center of gravity. If the particle is a regular spherical shape, its center point is its sphere's center. The radius is the longest half-length of the particle along a line connecting any point on its surface or in its center to the center point of the matrix. The content of R mainly refers to the atomic percentage of R.

[0080] The structure of the surface and central parts can be referenced. Figure 1 . Figure 1 Consider a single matrix particle, assuming its center point is p0, and any point p1 on its surface. The distance between p1 and the surface of the matrix particle is l1. The longest particle size along the line connecting p1 and p0 is half of the particle's length. Figure 1 Given l2, then l1 is greater than or equal to 0 and less than or equal to l2 × 20%. Now assume there is any point p2 at its center, the distance between p2 and the surface of the matrix particle is l3, and half the longest particle size along the line connecting p2 and p0 is l4. Then, l3 is greater than or equal to l4 × 70% and less than or equal to l4. Furthermore, the percentage of R atoms at p1 is higher than the percentage of R atoms at p2.

[0081] In some implementations, the valence of R is greater than or equal to +1 and less than or equal to +2. The valence of R is the same as or similar to that of lithium ions, and it has a greater tendency to occupy lithium sites without causing serious damage to the crystal lattice after occupying lithium sites.

[0082] In some embodiments, R includes at least one of K, Na, Mg, Cu, and Zn.

[0083] In some embodiments, 0 < x < 0.1; in other embodiments, 0 < x < 0.05; in yet other embodiments, 0.001 < x < 0.05; in yet other embodiments, 0.005 < x < 0.05. Exemplary x can be 0.001, 0.002, 0.004, 0.006, 0.008, 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, 0.2, etc. R occupying part of the lithium sites can effectively stabilize the material structure, control the manganese dissolution channel, inhibit manganese dissolution, and thus improve the cycle life. However, when the R element occupies insufficient lithium sites, its effect on improving the cycle life is not obvious, and when the proportion is too high, it will cause loss of active lithium and greatly reduce the material capacity.

[0084] In some embodiments, 0 < y < 0.3; in other embodiments, 0 < y < 0.25; in yet other embodiments, 0.05 < y < 0.25; in yet other embodiments, 0.05 < y < 0.2. Exemplary y can be 0, 0.01, 0.03, 0.05, 0.07, 0.1, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc. M element doping occupying part of the manganese sites can effectively stabilize the structure of lithium manganate material and improve the cycle performance of lithium manganate material. Too little M element doping cannot effectively stabilize the spinel lithium manganate structure, and too much M element doping will instead reduce the material capacity.

[0085] In some embodiments, M comprises at least one of a transition metal, an alkaline earth metal, an alkali metal, Al. Such metal elements can replace manganese sites to achieve doping. Part of the M element doping occupying manganese sites can effectively stabilize the material structure and improve the cycle performance of the material.

[0086] In some embodiments, the transition metal comprises at least one of V, Tc, Co, Ni, Fe, Zn, Zr, Y, Nb, Mo, Ti, Cr, W.

[0087] In some embodiments, the alkaline earth metal comprises at least one of Mg, Ca.

[0088] In some embodiments, the alkali metal comprises Li.

[0089] In some embodiments, X comprises one or more of a sixth main group element and a seventh main group element.

[0090] In some embodiments, the sixth main group element comprises S.

[0091] In some embodiments, the seventh main group element comprises one or both of F and Cl.

[0092] The sixth main group, i.e. VIA group, includes non-metals; the seventh main group, i.e. VIIA group, includes halogens. The valence of S in the sixth main group and F, Cl and the like in the seventh main group is negative, which can incorporate oxygen to replace oxygen ions, reduce the content of oxygen ions, stabilize the combination of Mn, M and oxygen elements in the matrix, and improve the large amount of hydrogen release behavior caused by the anion oxidation-reduction reaction of the manganese-rich material at high voltage, thereby improving the gas production of the material.

[0093] In some embodiments, the volume average diameter Dv50 of the lithium manganate material is 2-30 μm, and in some examples, the volume average diameter is 2-20 μm. The volume average diameter Dv50 refers to the volume of 1 particle with this diameter, which is exactly equal to the volume average of all particles, and the volume average diameter is also referred to as the volume diameter. The particle morphology of the lithium manganate material can be regular spherical, irregular spherical, ellipsoidal, polygonal, or other irregular shapes, and the size of each particle can be the same or different, so the volume average diameter Dv50 can well describe the particle size of the lithium manganate material. In actual operation, the volume average diameter Dv50 can be tested by a laser particle size analyzer or other methods. As a positive electrode material, the appropriate particle size of the lithium manganate material is beneficial to the intercalation and deintercalation of lithium ions, and is beneficial to improve the rate performance and capacity of the battery; if the particle size is too small, the specific surface area is larger, the particle surface energy is increased, and the particles are easily agglomerated and react with the electrolyte, the battery resistance is increased, and excessive energy is accumulated during the charging and discharging process, thereby causing a safety hazard; at the same time, too small particle size will also increase the irreversible capacity and reduce the cycle performance of the battery; and too large particle size will weaken the deintercalation of lithium ions, resulting in reduced rate performance and capacity.

[0094] In some embodiments, the lithium manganate material further comprises a coating layer arranged on the surface of the matrix. The coating layer here refers to a structure that partially or completely covers the surface of the matrix particles on the surface of the matrix, and at this time the lithium manganate material is a composite material composed of "core" and "shell", wherein the "core" is the matrix and the "shell" is the coating layer. The matrix and the coating layer can be attracted to each other by coulomb electrostatic attraction and / or firmly combined by chemical bonds. By arranging the coating layer on the surface of the matrix, the side reaction between the electrolyte and the spinel lithium manganate material can be effectively inhibited, and the dissolution of Mn 2+ through the coating layer; in cooperation with the inhibitory effect of the M element doped at the manganese site and the R element doped at the lithium site on the dissolution of Mn 2+ in the particle, the manganese dissolution problem can be effectively inhibited, and the cycle life of the material is improved.

[0095] In some embodiments, the coating layer accounts for greater than 0 and less than or equal to 5% of the mass of the lithium manganate material; in other embodiments, the coating layer accounts for 0.01% to 5% of the mass of the lithium manganate material; in other embodiments, the coating layer accounts for 1% to 5% of the mass of the lithium manganate material. Exemplarily, the coating layer accounts for 0.01%, 0.05%, 0.1%, 0.5%, 1%, 3%, 5%, etc. of the mass of the lithium manganate material. Too high a mass percentage of the coating layer will result in a decrease in the capacity of the material, and too low a mass percentage will result in the coating layer failing to inhibit the dissolution of manganese across the coating layer. In some embodiments, the coating layer contains at least one of a secondary group element, a group IA metal element, a group IIA element, a group IIIA element, a group IV element, a group VA element, and a group VIA element.

[0096] In some embodiments, the secondary group element contains at least one of Co, Ti, Nb, W, and Zr.

[0097] In some embodiments, the group IA metal element contains at least one of Li, Na, and K.

[0098] In some embodiments, the group IIA element contains at least one of Mg and Ca.

[0099] In some embodiments, the group IIIA element contains at least one of Al and B.

[0100] In some embodiments, the group IV element contains at least one of C and Si.

[0101] In some embodiments, the group V element contains N.

[0102] In some embodiments, the group VI element contains S.

[0103] In some embodiments, the coating layer contains oxides and / or salts of at least one of a secondary group element, a group IA metal element, a group IIA element, a group IIIA element, a group IV element, a group VA element, and a group VIA element.

[0104] The present application also provides a method for preparing a lithium manganate material, comprising:

[0105] mixing a lithium source, a manganese source, an M source, and an X source, and performing sintering treatment to obtain a spinel lithium manganate material doped with manganese sites;

[0106] performing ion exchange treatment on the spinel lithium manganate material doped with manganese sites and an R source in a liquid environment to obtain a lithium manganate material comprising a matrix (Li 1-x R x ) a Mn 2-y M y O4-z X z a lithium manganese oxide material of Li

[0107] wherein 0 < x ≤ 0.2, 0.95 < a ≤ 1.2, 0 ≤ y ≤ 0.5, 0 ≤ z ≤ 0.1; R is a lithium site doping element, R is distributed on the surface layer of the matrix; M is a manganese site doping element; X is an oxygen site doping element.

[0108] In the conventional preparation method of lithium site doped spinel lithium manganese oxide material, most of them need to be realized by sintering. However, during the sintering process, the doping elements will enter both the lithium site and the manganese site. Especially for low valence state Due to the very close ion radius, it is possible to be doped into the lithium site. This has been confirmed by researchers who identified the content ratio of the doping element Mg in the lithium site and the manganese site through X-ray photoelectron spectroscopy analysis (XPS) and neutron diffraction (NPD) (Angewandte Chemie, 2020, 132(26): 10681-10689). In addition, the sintering process will also increase the production cost of the material, which will reduce the cost advantage of spinel lithium manganese oxide. The preparation method of the present application disperses the manganese doped spinel lithium manganese oxide material and the lithium site doping element R in a liquid environment, and relies on ion exchange to realize the substitution of lithium site doping element R for lithium element. Compared with the conventional sintering doping technology, the advantages of this method are: ① precise doping of lithium site can be realized. Under the action of ion exchange, the doping element will tend to occupy the lithium site. ② Surface layer doping can be formed. Ion exchange is from the outside to the inside, which can make ion exchange mainly occur in the surface layer of manganese doped spinel lithium manganese oxide material, avoiding excessive occupation of lithium site by R leading to capacity loss. ③ The method is simple and easy to implement, low in cost, and can be applied on a large scale.

[0109] In the present application, the term "lithium source" refers to a substance that can provide lithium ions (or lithium elements), exemplary lithium sources such as lithium carbonate, lithium hydroxide, lithium nitrate, X compound of lithium, etc.

[0110] The term "manganese source" refers to a substance that can provide manganese ions (or manganese elements), exemplary manganese sources such as manganese dioxide, manganese sulfate, trimanganese tetraoxide, manganese carbonate, X compound of manganese, etc.

[0111] The term "M source" refers to a substance that can provide M ions (or M elements), exemplary M sources such as M element-containing oxides, M element-containing carbonates, M element-containing chlorides, M element-containing nitrates, M element-containing sulfates, M-containing X compounds, etc.

[0112] The term "X source" refers to a substance that can provide X ions (or X elements), exemplary X sources such as X compound of lithium, X compound of manganese, M-containing X compound, etc. These substances will not bring other metal impurities while introducing X.

[0113] In some embodiments, the stoichiometric ratio of lithium, manganese and M elements in the lithium source, the manganese source and the M source is set to satisfy (Li 1-x R x ) a Mn 2-y M y O 4-z X z , 0 < x < 0.2, 0.95 < a < 1.2, 0 < y < 0.5, that is, the stoichiometric ratio of lithium, manganese and M elements is 0.95-1.2: 1.5-2: 0-0.5, and in other embodiments, the stoichiometric ratio of lithium, manganese and M elements is 0.95-1.2: 1.75-2: 0-0.25.

[0114] The term "mixing" refers to the dispersion or blending of two or more different substances together. In particular in the present application, mixing the lithium source, the manganese source, the M source and the X source means uniformly dispersing or blending the lithium source, the manganese source, the M source and the X source together. The uniformity of mixing of the lithium source, the manganese source, the M source and the X source has an important influence on the sintering process and the quality of the sintered product. In the present application, the mixing method of the lithium source, the manganese source, the M source and the X source mainly includes mechanical mixing, such as ball milling mixing using a high-energy ball mill, sand milling mixing using a sand mill, resonance mixing using a resonance mixer, spiral mixing using a spiral mixer, etc. At the same time, the mixing process of the lithium source, the manganese source, the M source and the X source can be dry mixing or wet mixing. The dry mixing of the lithium source, the manganese source, the M source and the X source means directly mixing the powders (or particles) of the lithium source, the manganese source and the M source without adding any liquid medium during the mixing process; the wet mixing of the lithium source, the manganese source, the M source and the X source means adding a liquid medium during the mixing process of the lithium source, the manganese source, the M source and the X source. The liquid medium is, for example, water, ethanol, etc. For the case of wet mixing of the mixing method of the lithium source, the manganese source, the M source and the X source, the mixture can be dried before entering the sintering process step.

[0115] In some embodiments, after mixing the lithium source, the manganese source, the M source and the X source, the sintering temperature is 600-800°C; in other embodiments, the sintering temperature is 700-800°C; exemplary sintering temperatures are, for example, 600°C, 650°C, 700°C, 750°C, 800°C, etc. The sintering time is 8-20h; in other embodiments, the sintering time is 10-20h; exemplary sintering times are, for example, 8h, 10h, 12h, 14h, 16h, 18h, 20h, etc.

[0116] After high-temperature sintering, the lithium source and the manganese source form a spinel lithium manganate structure, and at the same time, the M element enters the manganese site of the spinel lithium manganate at high temperature to form a manganese site-doped spinel lithium manganate material.

[0117] In some embodiments, the sintering process is performed in an oxygen-containing atmosphere, for example, in an air atmosphere. Performing sintering in an oxygen-containing atmosphere can incorporate oxygen elements in the atmosphere into the crystal lattice to form a complete structure.

[0118] The term "liquid environment" refers to a liquid-containing, non-solid system environment, including but not limited to a solution system, a suspension system. In this application, the liquid environment in which the manganese site-doped spinel lithium manganate material is subjected to ion exchange treatment with the R source can be a solution system or a suspension system containing the manganese site-doped spinel lithium manganate material and the R source.

[0119] Therefore, in the liquid environment, the step of ion exchange treatment of the manganese site-doped spinel lithium manganate material with the R source can be specifically: providing a liquid environment containing the manganese site-doped spinel lithium manganate material and the R source, and performing ion exchange. More specifically, the step of ion exchange treatment includes: dispersing the manganese site-doped spinel lithium manganate material in a solvent, adding the R source, and performing ion exchange treatment; or dispersing the R source in a solvent, adding the manganese site-doped spinel lithium manganate material, and performing ion exchange; or dispersing the manganese site-doped spinel lithium manganate material and the R source in a solvent at the same time, and performing ion exchange. By performing ion exchange in a liquid environment, not only can R be precisely doped on the surface of the lithium site, but the ion exchange method is simple to operate, the reaction conditions are mild, and it has good adaptability to different types of R sources.

[0120] The term "R source" refers to a substance that can provide R ions (or manganese R elements). In some embodiments, the R source is soluble, for example, water-soluble, alcohol-soluble. Exemplary R sources include oxides, carbonates, chlorides, nitrates, sulfates of R, X compounds of R, etc. The amount of R source needs to satisfy the stoichiometric ratio of R in the chemical formula (Li 1-x R x ) a Mn 2-y M y O4, 0 < x < 0.2, 0.95 < a < 1.2, 0 < y < 0.5. Specifically, the molar ratio of Li elements in the manganese site-doped spinel lithium manganate material to R elements in the R source is 0.8-1:0-0.2; in some embodiments, the molar ratio of Li elements in the manganese site-doped spinel lithium manganate material to R elements in the R source is 0.95-1:0-0.05.

[0121] The term "solvent" as used herein refers to a medium capable of dissolving or dispersing the manganese-site doped spinel lithium manganate material and the R source, and includes at least one of water, ethanol, acetone, isopropanol, toluene, phosphate buffer, citric acid buffer, and acetic acid buffer. The amount of solvent used is required to be at least capable of completely dissolving or uniformly dispersing the manganese-site doped spinel lithium manganate material and the R source. In some embodiments, the solid-liquid ratio of the manganese-site doped spinel lithium manganate material to the solvent is 0.05-2 g / mL; in other embodiments, the solid-liquid ratio of the manganese-site doped spinel lithium manganate material to the solvent is 0.3-1 g / mL. Exemplary solid-liquid ratios of the manganese-site doped spinel lithium manganate material to the solvent include 0.05 g / mL, 0.1 g / mL, 0.2 g / mL, 0.3 g / mL, 0.4 g / mL, 0.6 g / mL, 0.8 g / mL, 1 g / mL, 1.2 g / mL, 1.4 g / mL, 1.5 g / mL, 1.6 g / mL, 1.8 g / mL, 2 g / mL, etc.

[0122] In some embodiments, the pH of the liquid environment is 6-10, and in other embodiments, the pH of the liquid environment is 7-9. Exemplary pH values include 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, etc. A suitable pH value can facilitate the ion exchange of the R element with lithium ions, so that the R element occupies the lithium sites in the surface layer.

[0123] In some embodiments, the ion exchange treatment is performed at a temperature of 25-100°C, and in other embodiments, the ion exchange treatment is performed at a temperature of 40-80°C. Exemplary ion exchange treatment temperatures include 25°C, 40°C, 60°C, 80°C, 100°C, etc. Within a certain range, the higher the ion exchange temperature, the faster the lithium site doping. However, to avoid loss of the solvent during the ion exchange process, the ion exchange temperature should not be too high. Compared with conventional sintering techniques, the ion exchange temperature in the present application is lower. Without the high temperature driving force and ion exchange effect, the doping element R tends to occupy the lithium sites, thereby achieving precise doping of the lithium sites.

[0124] In some embodiments, the ion exchange treatment is performed for a time period of 1-10 h, and in other embodiments, the ion exchange treatment is performed for a time period of 3-6 h, such as 1 h, 2 h, 4 h, 6 h, 8 h, 10 h, etc. Generally, the longer the ion exchange time, the higher the utilization rate of the R element, and the more lithium sites in the lithium manganate material that are occupied by the R element.

[0125] The ion exchange process can be carried out under stirring, ultrasonic or shaking to make the manganese-site doped spinel lithium manganate material fully contact with the R source, accelerate the ion exchange, and meanwhile avoid the manganese-site doped spinel lithium manganate material from being precipitated. After the ion exchange, the solid can be collected through solid-liquid separation (including but not limited to filtration, standing precipitation, centrifugation, etc.), and the solid can be washed to obtain (Li 1-x R x ) a Mn 2-y M y O4.

[0126] In some embodiments, after the step of ion exchanging the manganese-site doped spinel lithium manganate material with the R source in the liquid environment, the method further comprises a step of forming a coating layer on the substrate.

[0127] The method of forming the coating layer includes but is not limited to solid phase reaction (heat treatment), mechanical mixing, vapor deposition, spraying, etc. In some embodiments, the method of forming the coating layer includes solid phase reaction.

[0128] In some embodiments, the method of forming the coating layer on the substrate comprises mixing the substrate with a coating material, and heat treating the substrate to form the coating layer on the substrate.

[0129] The term "coating material" refers to a substance used to form the coating layer. The coating material can be attracted to each other by Coulomb electrostatic force and / or form a coating layer on the surface of the substrate by chemical bonding. In the process of forming the coating layer, the chemical composition of the coating material generally does not change, i.e., the chemical composition of the coating material is the same as that of the formed coating layer. Of course, chemical reactions can also occur so that the chemical composition of the coating material and the coating layer is different. In this application, the coating layer contains at least one of the following elements: a secondary group element, an IA group metal element, a IIA group element, a IIIA group element, a IVA group element, a VA group element, and a VIA group element. Correspondingly, the coating material should also contain at least one of the following elements: a secondary group element, an IA group metal element, a IIA group element, a IIIA group element, a IVA group element, a VA group element, and a VIA group element. In some embodiments, when the coating layer contains an oxide and / or a salt containing at least one of the following elements: a secondary group element, an IA group metal element, a IIA group element, a IIIA group element, a IVA group element, a VA group element, and a VIA group element, the corresponding coating material can be an oxide and / or a salt containing at least one of the following elements: a secondary group element, an IA group metal element, a IIA group element, a IIIA group element, a IVA group element, a VA group element, and a VIA group element.

[0130] In some embodiments, the temperature of the heat treatment is 300-600°C, in other embodiments, the temperature of the heat treatment is 400-500°C, for example 300°C, 340°C, 400°C, 450°C, 500°C, 550°C, 600°C, etc. By high-temperature heat treatment, the coating material is firmly combined with the substrate to form a surface protective layer, and the appropriate heat treatment temperature also reduces the generation of side reactions.

[0131] In some embodiments, the time of the heat treatment is 2-6h, in other embodiments, the time of the heat treatment is 3-5h, for example 2h, 3h, 4h, 5h, 6h, etc.

[0132] The lithium manganate material of the present application can be applied to the positive electrode sheet, and further applied to at least one of secondary batteries, and power consuming devices.

[0133] Specifically, the present application also proposes a positive electrode sheet, which comprises a current collector and an electrode active layer, and the electrode active layer is combined with the current collector; wherein the electrode active layer contains the lithium manganate material as described above or the lithium manganate material prepared by the preparation method as described above.

[0134] The term "positive electrode" also refers to the cathode of the battery, which contains a positive electrode material, i.e. an active material. In a lithium ion battery, when charging, lithium ions are released from the lattice of the positive electrode material, pass through the electrolyte and insert into the lattice of the negative electrode material; when discharging, lithium ions are released from the lattice of the negative electrode material, pass through the electrolyte and insert into the lattice of the positive electrode material. The current collector is a substrate on the electrode for combining with the electrode active layer, and as the current collector of the positive electrode sheet, a metal current collector, a carbon current collector, a conductive resin current collector, a composite current collector of metal and resin, etc. can be selected, such as aluminum, nickel, stainless steel, carbon fiber, carbon nanotube (CNT), graphite, etc.

[0135] The lithium manganate material of the present application can be used as the active material of the positive electrode sheet, and in the cycle process, the surface lithium site doping element R in the lithium manganate material can be used to inhibit the deposition of Mn 2+ dissolution, reduce the loss of Mn 2+ , thereby avoiding the capacity attenuation of spinel lithium manganate in the cycle process; and the lithium site doping in the lithium manganate material is less, which can reduce the loss of active lithium and avoid the capacity loss caused by lithium site doping.

[0136] In some embodiments, the electrode active layer further comprises at least one of a conductive agent and a binder. The conductive agent and / or the binder can form the electrode active layer together with the lithium manganate material.

[0137] In the positive electrode sheet, the conductive agent collects micro-currents between the active materials and between the active materials and the current collector, improving the electronic conductivity, and the conductive agent can also promote the infiltration of the electrolyte into the positive electrode sheet. Exemplary conductive agents include carbon nanotubes, conductive carbon black (super-P), Ketjen black, carbon fibers, graphene, etc. The ratio of the conductive agent to the lithium manganate material can be set according to the requirements and the ratios known in the art. As an example, the mass ratio of the conductive agent to the lithium manganate material is 30-100: 1, and in some embodiments, the mass ratio of the conductive agent to the lithium manganate material is 40-60: 1.

[0138] The binder is used to improve the binding ability of the electrode active layer to the current collector. Exemplary binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), fluorinated rubber, polyethylene, polyethylene, polyurethane, etc. The ratio of the binder to the lithium manganate material can be set according to the requirements and the ratios known in the art. As an example, the mass ratio of the binder to the lithium manganate material is 5-50: 1, and in some embodiments, the mass ratio of the binder to the lithium manganate material is 10-40: 1.

[0139] The application also provides a secondary battery, which includes the positive electrode sheet described above.

[0140] The positive electrode sheet containing the lithium manganate material of the application is applied to a secondary battery, and the resulting secondary battery has high capacity, high coulombic efficiency, and excellent cycle stability.

[0141] In some embodiments, the secondary battery further includes a negative electrode sheet, and the positive electrode sheet and the negative electrode sheet form a loop in the case of charging and discharging of the secondary battery.

[0142] In some embodiments, the negative electrode sheet can be a metal lithium sheet.

[0143] In some embodiments, the negative electrode sheet can also be a negative electrode sheet including a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. For example, the negative electrode current collector includes two opposite surfaces in the thickness direction of the negative electrode current collector, and the negative electrode active material layer is laminated on either one or both of the two surfaces of the negative electrode current collector.

[0144] In some embodiments, the negative electrode active material layer includes a negative electrode active material. The embodiments of the application do not specifically limit the type of negative electrode active material, which can be selected according to actual requirements. As an example, the negative electrode active material can be natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite.

[0145] In some embodiments, the negative active material layer can further include a conductive agent and a binder. The present application does not make specific limitations on the types of the conductive agent and the binder in the negative active material layer, which can be selected according to actual needs. As an example, the conductive agent is one or more of graphite, super-conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; and the binder is one or more of styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin, and carboxymethyl cellulose (CMC).

[0146] In some embodiments, the negative active material layer can further optionally include a thickening agent, such as carboxymethyl cellulose (CMC).

[0147] In some embodiments, the negative current collector can be a metal foil or a porous metal plate with good electrical conductivity and mechanical properties, and the material can be one or more of copper, nickel, titanium, iron, and their respective alloys. The negative current collector is, for example, a copper foil.

[0148] In some embodiments, the negative electrode sheet can be prepared according to conventional methods in the art. For example, the negative active material, the conductive agent, the binder, and the thickening agent are dispersed in a solvent, which can be N-methyl pyrrolidone (NMP) or deionized water, to form a uniform negative electrode slurry, the negative electrode slurry is coated on the negative current collector, and after drying, rolling, and other processes, the negative electrode sheet is obtained.

[0149] In some embodiments, the secondary battery further includes an electrolyte. The electrolyte can serve as a carrier for ion transport in the secondary battery, ensuring that the reactions occurring during the operation of the secondary battery are reversible. In some embodiments, the electrolyte can be a solid electrolyte, such as a polymer electrolyte, an inorganic solid-state electrolyte, etc., but is not limited thereto. The electrolyte can also be an electrolyte solution. As the above-mentioned electrolyte solution, it includes a solvent and a lithium salt dissolved in the solvent.

[0150] In some embodiments, the secondary battery further includes an electrolyte. The electrolyte can serve as a carrier for ion transport in the secondary battery, ensuring that the reactions occurring during the operation of the secondary battery are reversible. In some embodiments, the electrolyte can be a solid electrolyte, such as a polymer electrolyte, an inorganic solid-state electrolyte, etc., but is not limited thereto. The electrolyte can also be an electrolyte solution. As the above-mentioned electrolyte solution, it includes a solvent and a lithium salt dissolved in the solvent.

[0151] The lithium salt can be one or more of LiPF6(lithium hexafluorophosphate), LiBF4(lithium tetrafluoroborate), LiClO4(lithium perchlorate), LiAsF6(lithium hexafluoroarsenate), LiFSI(lithium bisfluorosulfonylimide), LiTFSI(lithium bis(trifluoromethylsulfonyl)imide), LiTFS(lithium trifluoromethanesulfonate), LiDFOB(lithium difluoro(oxalato)borate), LiBOB(lithium bis(oxalato)borate), LiPO2F2(lithium difluorophosphate), LiDFOP(lithium difluoro(oxalato)phosphate), and LiTFOP(lithium tetrafluoro(oxalato)phosphate), for example one or more of LiPF6(lithium hexafluorophosphate), LiBF4(lithium tetrafluoroborate), LiBOB(lithium bis(oxalato)borate), LiDFOB(lithium difluoro(oxalato)borate), LiTFSI(lithium bis(trifluoromethylsulfonyl)imide), and LiFSI(lithium bisfluorosulfonylimide).

[0152] The electrolyte solution can also optionally contain other additives, such as one or more of vinyl carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), succinonitrile (SN), adiponitrile (ADN), glutaronitrile (GLN), hexanetritrile (HTN), 1,3-propane sultone (1,3-PS), vinyl sulfate (DTD), methyl methylsulfate (MMDS), 1-propene-1,3-sultone (PST), 4-methyl ethylene sulfate (PCS), 4-ethyl ethylene sulfate (PES), 4-propyl ethylene sulfate (PEGLST), propylene sulfate (TS), 1,4-butane sultone (1,4-BS), ethylene sulfite (DTO), dimethyl sulfite (DMS), diethyl sulfite (DES), sulfonate cyclic quaternary ammonium salt, tris(trimethylsilyl)phosphate (TMSP), and tris(trimethylsilyl)borate (TMSB), but is not limited thereto.

[0153] In some embodiments, the secondary battery further includes a separator stacked between the positive electrode sheet and the negative electrode sheet. In some secondary batteries, a separator is provided to separate the positive electrode sheet and the negative electrode sheet, so that the electrons in the battery cannot pass freely, preventing the two poles from being in contact and short-circuiting, while allowing the ions in the electrolyte to pass freely between the positive and negative electrodes.

[0154] The lithium ion secondary battery of the embodiments of the present application is not particularly limited with respect to the separator, and any known porous structure separator having electrochemical stability and mechanical stability can be used, such as a single layer or multiple layers of film of one or more of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride (PVDF).

[0155] The positive electrode sheet and the negative electrode sheet are alternately stacked, and a separation film is arranged between the positive electrode sheet and the negative electrode sheet to play a separation role, so as to obtain a battery cell, which can also be obtained after being wound. The battery cell is placed in a shell, electrolyte is injected, and the shell is sealed, so as to obtain a lithium ion secondary battery.

[0156] In addition, the application further provides a power utilization device comprising the secondary battery.

[0157] The secondary battery disclosed in the embodiments of the application can be used in a power utilization device using the battery as a power source or a variety of energy storage systems using the battery as an energy storage element. The power utilization device can be, but is not limited to, a mobile phone, a tablet computer, a notebook computer, an electric toy, an electric tool, an electric vehicle, an electric automobile, a ship, a spacecraft, and the like. The electric toy can include a fixed or mobile electric toy, such as a game machine, an electric automobile toy, an electric ship toy, an electric aircraft toy, and the like. The spacecraft can include an airplane, a rocket, a space shuttle, a spacecraft, and the like.

[0158] The application will be described in detail below with reference to specific embodiments.

[0159] Embodiment 1

[0160] (1) A lithium manganate material (Li 0.995 Mg 0.005 ) 1.1 Mn 1.9 Zr 0.1 O4@TiO2, comprising (Li 0.995 Mg 0.005 ) 1.1 Mn 1.9 Zr 0.1 O4, (Li 0.995 Mg 0.005 ) 1.1 Mn 1.9 Zr 0.1 O4 contains a lithium site doping element Mg, a manganese site doping element Zr, (Li 0.995 Mg 0.005 ) 1.1 Mn 1.9 Zr 0.1 O4 is provided with a coating layer E, i.e., TiO2, on the surface.

[0161] The lithium manganate material (Li 0.995 Mg 0.005 ) 1.1 Mn 1.9 Zr 0.1 O4@TiO2 is prepared as follows:

[0162] 1) Selecting electrodeposited manganese dioxide, lithium carbonate and zirconium dioxide, weighing according to the molar ratio of lithium-manganese-zirconium elements being 1.1:1.9:0.1, ball milling in a high-energy ball mill for 4h, mixing uniformly; after drying, sintering at 750℃ for 16h in an air atmosphere to obtain manganese site doped spinel lithium manganate (Li 1.1 Mn 1.9 Zr0 .1 O4).

[0163] 2) Dispersing the manganese site doped spinel lithium manganate material obtained in step 1) in water, controlling the solid-liquid ratio to be 0.6g / mL, stirring and dispersing uniformly, adjusting to pH 8.5 with 0.05M disodium hydrogen phosphate-sodium dihydrogen phosphate buffer. Then adding a certain amount of MgCl2 according to the molar ratio of Li element in the manganese site doped spinel lithium manganate to added Mg element being 0.995:0.005, controlling the ion exchange temperature to be 60℃, reacting for 4h, and obtaining lithium site doped spinel lithium manganate material (Li 0.995 Mg 0.005 ) 1.1 Mn 1.9 Zr 0.1 O4 after filtration and washing.

[0164] 3) Weighing the lithium site doped spinel lithium manganate material (Li 0.995 Mg 0.005 ) 1.1 Mn 1.9 Zr 0.1 O4 obtained in step 2) and titanium dioxide (TiO2) according to the mass ratio of 97.5:2.5, and ball milling in a high-energy ball mill for 3h, then heat treating at 450℃ for 4h, forming a coating layer E on the surface of (Li 0.995 Mg 0.005 ) 1.1 Mn 1.9 Zr 0.1 O4, to obtain lithium manganate material (Li 0.995 Mg 0.005 ) 1.1 Mn 1.9 Zr 0.1 O4@TiO2.

[0165] The morphology and structure of the lithium manganate material (Li 0.995 Mg 0.005 ) 1.1 Mn 1.9 Zr 0.1 O4@TiO2 prepared in Example 1 can be seen from Figure 2 . From Figure 2It can be seen that the lithium manganate material of the embodiment has a micro morphology with good dispersity, and the particles present a certain agglomeration; analyzing the particle size, the particle size distribution of the particles is wide, and the particle diameter is about 2-20 μm.

[0166] CP cross-section polishing analysis was performed on the material, and the electron micrograph thereof is shown in FIG. 1, and the element composition and distribution thereof were analyzed, and multiple points were selected on the cross-section of the particles, and the points were labeled as 1, 12, 13, 15, 16 and 17, wherein 1, 12, 13, 16 and 17 are located at the surface layer of the particles, and 15 is located at the bulk phase, i.e. the center of the particles, and the atomic percentage of Mg element in each point is shown in Table 1 below. It can be found that the lithium site doping element Mg is distributed in the surface layer and the bulk phase of the particles, but mainly in the surface layer, and the atomic percentage of Mg element in the surface layer is obviously greater than that in the bulk phase. Figure 3

[0167] Table 1.

[0168] Spectrograph point Position Mg element atomic percentage / % 1 Surface layer 0.39 12 Surface layer 0.27 13 Surface layer 0.22 15 Bulk phase 0.10 16 Surface layer 0.19 17 Surface layer 0.25

[0169] (2) Positive electrode sheet and lithium ion battery

[0170] (Li 0.995 Mg 0.005 ) 1.1 Mn 1.9 Zr 0.1 O4@TiO2 as the positive electrode material, slurry was prepared according to the mass ratio of the positive electrode material, conductive agent super-P, CNT and PVDF of 94:1.5:0.5:3, coated on an Al foil with a thickness of 13 μm, and then vacuum dried at 120°C, cold pressed, cut and striped to obtain a positive electrode sheet. Lithium sheet was used as the negative electrode sheet, and the positive electrode sheet, the separator and the negative electrode sheet were stacked in order, the separator was located between the positive electrode and the negative electrode to play a separating role, and then the bare cell was obtained by winding. The bare cell was placed in an outer package, and then electrolyte solution was injected, packaged, injected, formed and degassed to obtain a lithium ion battery.

[0171] (3) Electrochemical performance test

[0172] 1) Capacity test

[0173] The positive electrode sheet prepared above was used as the positive electrode, lithium sheet was used as the negative electrode, 1 mol / L LiPF6 ethylene carbonate (EC) + dimethyl carbonate (DMC) + diethyl carbonate (DEC) solution (volume ratio of 1:1:1) was used as the electrolyte, a coin lithium ion battery was assembled, and the charge and discharge capacity and the charge and discharge curve of the coin lithium ion battery at 3-4.35 V at 0.1C were tested. The (Li 0.995 Mg 0.005 ) 1.1 Mn​1.9 Zr 0.1 The first cycle charge-discharge curve of TiO2@O4 is shown in Figure 1. Figure 4 .

[0174] 2) Cycle performance test

[0175] The lithium ion battery was subjected to charge-discharge cycle test at 25°C with a current density of 1C, and the voltage interval was set to 3V-4.3V.

[0176] (4) Manganese dissolution test

[0177] The cell after the cycle performance test was disassembled in a glove box, the anode sheet was taken out, soaked and cleaned with dimethyl carbonate (DMC), and the surface residues were removed and dried in an oven. The anode powder on the dried anode sheet was scraped off, and the content of manganese element deposited in the anode powder was tested by inductively coupled plasma spectrometer (ICP), and the specific test data is shown in Table 2.

[0178] Examples 2-4

[0179] Examples 2-4 are different from Example 1 only in that in step 1) of the preparation method of lithium manganate material, lithium, manganese and zirconium elements are weighed according to the molar ratio of 1.1:1.95:0.05, 1.1:1.8:0.2, and 1.1:1.7:0.3, respectively. The others are the same as Example 1.

[0180] Examples 5-11

[0181] Examples 5-11 are different from Example 1 only in that in step 1) of the preparation method of lithium manganate material, the manganese site doping element M is changed from Zr element in Example 1 to V, Tc, Ni, Nb, Mo, Ti, and W, respectively, that is, the raw material zirconium dioxide in this step is changed to V2O5, Tc2O7, NiO, Nb2O5, MoO2, TiO2, and WO3, respectively. The others are the same as Example 1.

[0182] Examples 12-14

[0183] Examples 12-14 are different from Example 1 only in that in step 2) of the preparation method of lithium manganate material, the molar ratio of Li element in the manganese site doped spinel lithium manganate to the added Mg element is changed to 0.999:0.001, 0.99:0.01, and 0.9:0.1, respectively. The others are the same as Example 1.

[0184] Examples 15-18

[0185] Examples 15-18 differ from Example 1 only in that in step 2) of the preparation method of the lithium manganate material, the element ion-exchanged with the manganese-site doped spinel lithium manganate is changed from Mg to Na, K, Cu, Zn, respectively, that is, MgCl2in this step is changed to the same metal molar amount of NaCl, KCl, CuCl2, ZnCl2, respectively. The others are the same as Example 1.

[0186] Examples 19-20

[0187] Examples 19-20 differ from Example 1 only in that in step 3) of the preparation method of the lithium manganate material, the lithium-site doped spinel lithium manganate material and titanium dioxide (TiO2) are weighed according to the mass ratio of 99:1, 95:5, respectively. The others are the same as Example 1.

[0188] Examples 21-24

[0189] Examples 21-24 differ from Example 1 only in that in step 3) of the preparation method of the lithium manganate material, the raw material of the coating layer E added is Al2O3, TiO2, WO3, ZrO2, respectively, that is, TiO2in this step is changed to the same mass of Al2O3, TiO2, WO3, ZrO2, respectively. The others are the same as Example 1.

[0190] Comparative Example 1

[0191] Comparative Example 1 differs from Example 1 only in that in step 1) of the preparation method of the lithium manganate material, the manganese-site doped element Zr is not added, that is, the raw material in this step does not contain zirconium dioxide, and steps 2) and 3) of the preparation method of the lithium manganate material are not performed. The others are the same as Example 1.

[0192] Comparative Example 2

[0193] Comparative Example 2 differs from Example 1 only in that in step 1) of the preparation method of the lithium manganate material, the manganese-site doped element Zr is not added, that is, the raw material in this step does not contain zirconium dioxide. The others are the same as Example 1.

[0194] Comparative Example 3

[0195] Comparative Example 3 differs from Example 1 only in that in step 2) of the preparation method of the lithium manganate material, the lithium-site doped element R is not added, that is, MgCl2is not added in this step. The others are the same as Example 1.

[0196] Comparative Example 4

[0197] The difference between Comparative Example 4 and Example 1 is only that in step 1) of the preparation method of the lithium manganate material, MgCl2 is added in a Li element to Mg element molar ratio of 0.995:0.005, and after being mixed uniformly with the electrodeposited manganese dioxide, lithium carbonate, and zirconium dioxide, sintering is performed together, and in step 2), no MgCl2 is added, thereby obtaining a bulk-doped lithium manganate material. The other aspects are the same as in Example 1.

[0198] Comparative Example 5

[0199] The difference between Comparative Example 5 and Example 1 is only that in step 3) of the preparation method of the lithium manganate material, no coating layer raw material (TiO2) is added.

[0200] The element composition or raw material composition and electrochemical test results of each example and comparative example are summarized in Table 2.

[0201] Table 2.

[0202]

[0203]

[0204] In the above table, “M element ratio to manganese site” refers to the value of y in the chemical formula (Li 1-x R x ) a Mn 2-y M y O 4-z X z ;

[0205] “R element ratio to lithium site” refers to the value of x in the chemical formula (Li 1-x R x ) a Mn 2-y M y O 4-z X z ;

[0206] “Coating layer E feeding ratio” refers to the mass percentage of the mass of the coating layer E in the entire lithium manganate material, coating layer E feeding ratio = coating layer mass / lithium manganate material mass x 100% = coating layer mass / [coating layer mass + (Li 1-x R x ) a Mn 2-y M y O 4-z X z mass] x 100%;

[0207] “room temperature” refers to 25°C.

[0208] Comparing Examples 1-4 with Comparative Example 2, it can be seen that Examples 1-4 add manganese site doping element M to the lithium manganate material, and under the condition of a suitable M element ratio to manganese site, the capacity retention rate of the lithium manganate material after 800 cycles can be improved from 88.8% of Comparative Example 2 to a maximum of 93.3%, reflecting that partial M element doping occupying manganese sites can effectively stabilize the material structure and improve the cycle performance of the material. Among them, M element doping with too little M element ratio to manganese sites cannot effectively stabilize the spinel lithium manganate structure, and too much M element doping will instead reduce the material capacity.

[0209] Comparing Examples 1, 5-11, it can be seen that Zr, V, Tc, Ni, Nb, Mo, Ti, and W element doping manganese sites can effectively stabilize the material structure and improve the cycle life.

[0210] Comparing Examples 1, 12-14 and Comparative Examples 1, 3, Examples 1, 12-14 add surface layer lithium site doping element R (specifically Mg) to the lithium manganate material, and the capacity retention rate after cycling is improved, and it also has high capacity and coulombic efficiency, reflecting that Mg element occupying part of the lithium sites in the lithium manganate material can effectively stabilize the material structure, control the manganese dissolution channel, inhibit manganese dissolution, and thus improve the cycle life. However, when the lithium sites occupied by Mg element are insufficient, the improvement effect on the cycle life is not obvious, and when the ratio is too high, it will lead to loss of active lithium and a significant reduction in material capacity.

[0211] At the same time, compared with the lithium manganate material doped with Mg in the bulk phase prepared by using a conventional sintering method in Comparative Example 4, the lithium manganate material doped with Mg element by ion exchange in Example 1 has more Mg element occupying lithium sites and mainly distributed on the surface layer of the particles, which can improve the cycle life while reducing the total amount of lithium replaced by Mg and avoiding loss of material capacity.

[0212] In addition, as can be seen from Examples 15-18, Na, K, Cu, and Zn doping lithium sites can improve the cycle life of the material.

[0213] Analyzing Examples 1, 19-24 and Comparative Examples 1, 5 in the table, the coating layer E can improve the capacity retention rate of the lithium manganate material after cycling, because the coating layer E can effectively inhibit the side reaction between the electrolyte and the spinel lithium manganate material, and also inhibit the Mn 2+ dissolved through the coating layer, and the M element doped in the manganese site and the R element doped in the lithium site have a synergistic inhibitory effect on the dissolution of Mn 2+ in the particles, which can effectively inhibit the manganese dissolution problem and improve the cycle life of the material.

[0214] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than limit them. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced equivalently. Such modifications or replacements do not change the essence of the corresponding technical solutions, which should be covered in the scope of the claims and the specification of the present application. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A lithium manganate material, characterized in that, A cathode material comprising a host having a chemical formula of (Li 1-x R x ) a Mn 2-y M y O 4- z X z , wherein 0 The R is a lithium site doping element, the R is distributed on a surface layer of the host; the M is a manganese site doping element; and the X is an oxygen site doping element.

2. The lithium manganate material of claim 1, wherein, The base body comprises a surface layer part and a central part, wherein the distance between any point in the surface layer part and the surface of the base body is greater than or equal to 0 and less than or equal to half of the longest particle size in the direction of the line connecting the point and the center point of the base body multiplied by 20%; the distance between any point in the central part and the surface of the base body is greater than or equal to half of the longest particle size in the direction of the line connecting the point and the center point of the base body multiplied by 70% and less than or equal to half of the longest particle size in the direction of the line connecting the point and the center point of the base body; the content of R at the surface layer part is greater than the content of R at the central part.

3. The lithium manganate material of claim 1 or 2, wherein, The valence of R is greater than or equal to +1 and less than or equal to +2.

4. The lithium manganate material of claim 3, wherein, R comprises at least one of K, Na, Mg, Cu, Zn.

5. The lithium manganate material of claim 1 or 2, wherein, 0＜x≤0.1。 6. The lithium manganate material of claim 5, wherein, 0＜x≤0.05。 7. The lithium manganate material of claim 1 or 2, wherein, 0≤y≤0.3。 8. The lithium manganate material of claim 7, wherein, 0≤y≤0.25。 9. The lithium manganate material of claim 1 or 2, wherein, M comprises at least one of transition metal, alkaline earth metal, alkali metal, Al; And / or, X comprises one or more of the sixth main group element and the seventh main group element.

10. The lithium manganate material of claim 9, wherein, The transition metal comprises at least one of V, Tc, Co, Ni, Fe, Zn, Zr, Y, Nb, Mo, Ti, Cr, W; And / or, the alkaline earth metal comprises at least one of Mg, Ca; And / or, the alkali metal comprises Li; And / or, the sixth main group element comprises S; And / or, the seventh main group element comprises one or both of F and Cl.

11. The lithium manganate material of claim 1 or 2, wherein, The volume average diameter Dv50 of the lithium manganate material is 2-30 μm.

12. The lithium manganate material of claim 1 or 2, wherein, The lithium manganate material further comprises a coating layer arranged on the surface of the base body.

13. The lithium manganate material of claim 12, wherein, The mass percentage of the coating layer in the lithium manganate material is greater than 0 and less than or equal to 5%.

14. The lithium manganate material of claim 12, wherein, The coating layer contains at least one of the following elements: secondary group element, IA group metal element, IIA group element, IIIA group element, IVA group element, VA group element, VIA group element.

15. The lithium manganate material of claim 14, wherein, The secondary group element comprises at least one of Co, Ti, Nb, W, Zr; And / or, the IA group metal element comprises at least one of Li, Na, K; And / or, the IIA group element comprises at least one of Mg, Ca; And / or, the IIIA group element comprises at least one of Al, B; And / or, the IVA group element comprises at least one of C, Si; And / or, the V group element comprises N; And / or, the VI group element comprises S.

16. A method of producing a lithium manganate material, characterized by, Comprise: Mixing a lithium source, a manganese source, an M source and an X source, and obtaining a spinel lithium manganate material doped with manganese by sintering treatment; In a liquid environment, the manganese site doped spinel lithium manganate material is ion exchanged with an R source to obtain a lithium manganate material containing a matrix (Li 1-x R x ) a Mn 2-y M y O 4-z X z ​ Wherein 0 17. The method for preparing lithium manganese oxide material according to claim 16, characterized in that, The sintering treatment is carried out at a temperature of 600-800°C; And / or, the sintering treatment is carried out for 8-20 h; And / or, the sintering treatment is carried out in an oxygen-containing atmosphere.

18. The method of claim 17, wherein the lithium manganate material is prepared by a process comprising: The sintering treatment is carried out at a temperature of 700-800°C; ​ And / or, the sintering treatment is carried out for 10-20 h.

19. The method for preparing lithium manganese oxide material according to any one of claims 16 to 18, characterized in that, The ion exchange treatment comprises: The manganese site doped spinel lithium manganate material is dispersed in a solvent, the R source is added, and ion exchange treatment is performed. Alternatively, the R source is dispersed in a solvent, the manganese site doped spinel lithium manganate material is added, and ion exchange treatment is performed. Alternatively, the manganese site doped spinel lithium manganate material and the R source are simultaneously dispersed in a solvent, and ion exchange treatment is performed.

20. The method for preparing lithium manganese oxide material according to claim 19, characterized in that, The solvent includes at least one of water, ethanol, acetone, isopropanol, toluene, phosphate buffer, citric acid buffer, and acetic acid buffer.

21. The method of claim 19, wherein the lithium manganate material is prepared by a process comprising: The solid-liquid ratio of the manganese site doped spinel lithium manganate material to the solvent is 0.05-2 g / mL. ​ 22. The method for preparing lithium manganese oxide material according to claim 21, characterized in that, The solid-liquid ratio of the manganese site doped spinel lithium manganate material to the solvent is 0.3-1 g / mL.

23. The method for preparing lithium manganese oxide material according to any one of claims 16 to 18, characterized in that, The pH of the liquid environment is 6-10.

24. The method of claim 23, wherein the lithium manganate material is prepared by a process comprising: The pH of the liquid environment is 7-9. ​ 25. The method of claim 16, 17 or 18, wherein the lithium manganate material is prepared by a process comprising: The temperature of the ion exchange treatment is 25°C-100°C. ​ And / or, the time of the ion exchange treatment is 1-10 h.

26. The method of claim 25, wherein the lithium manganate material is prepared by a process comprising: The temperature of the ion exchange treatment is 40°C-80°C. And / or, the time of the ion exchange treatment is 3-6 h.

27. The method of claim 16, 17 or 18, wherein the lithium manganate material is prepared by a process comprising: After the step of ion exchange treatment of the manganese site doped spinel lithium manganate material and the R source, a step of forming a coating layer on the substrate is further included. ​ 28. The method of claim 27, wherein the lithium manganate material is prepared by a process comprising: The step of forming a coating layer on the substrate includes mixing the substrate with a coating material, and forming the coating layer on the substrate through heat treatment. ​ 29. The method of claim 28, wherein the lithium manganate material is prepared by a process comprising: The temperature of the heat treatment is 300°C-600°C. ​ And / or, the time of the heat treatment is 2-6 h.

30. The method of claim 29, wherein the lithium manganate material is prepared by a process comprising: The temperature of the heat treatment is 400°C-500°C. And / or, the time of the heat treatment is 3-5 h.

31. A positive electrode sheet characterized by comprising: The electrode includes a current collector and an electrode active layer, and the electrode active layer is combined with the current collector; wherein the electrode active layer contains the lithium manganate material according to any one of claims 1-15.

32. A secondary battery characterized by comprising: The positive electrode sheet includes the positive electrode sheet according to claim 31.

33. An electrical device, comprising: The secondary battery includes the secondary battery according to claim 32.

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