Cathode materials, electrochemical devices and electronic devices containing them

Abstract

This application relates to the field of energy storage materials technology, and more particularly to a cathode material and an electrochemical and electronic device comprising the same. This application provides a cathode material having a crystal structure belonging to space group Cmc21. The crystal structure of the cathode material provided by this application has a specific space group, which facilitates the diffusion of lithium ions in the bulk phase of the material, improves the kinetic performance of the cathode material, and can effectively improve the capacity performance, coulombic efficiency, and cycle performance of the cathode material.

Description

[Technical Field]

[0001] This application relates to the field of energy storage materials technology, specifically to a cathode material, an electrochemical device and an electronic device containing the same. [Background Technology]

[0002] Electrochemical devices (such as lithium-ion batteries) possess high theoretical specific capacity and high safety performance, and have gradually become the main power source in the 3C field (computers, communications, and consumer electronics) and the power field (EV field). Among these, the cathode material, as a crucial component of lithium-ion batteries, has a significant impact on their performance; therefore, continuous optimization and improvement of cathode materials are particularly important. Currently, the mainstream cathode material used in the 3C field is generally lithium cobalt oxide, while the mainstream cathode material used in the EV field is nickel-cobalt-manganese ternary material. Both of these materials are layered transition metal oxides, in which lithium ions move freely within the interlayer between the transition metal and oxygen.

[0003] To achieve high energy density, increasing the nickel content of cathode materials to improve their reversible specific capacity has become one method for optimizing cathode materials. Therefore, the continuous optimization of high-nickel ternary cathode materials is receiving increasing attention in pursuit of higher capacity and energy density. For high-nickel cathode materials, as the nickel content increases, on the one hand, the interlayer spacing of the lithium-O layer decreases, the lithium-ion migration barrier increases, and the kinetics deteriorate; on the other hand, because the radius of divalent nickel ions is close to that of lithium ions, lithium-nickel mixing easily occurs during synthesis, leading to reduced material capacity and deteriorated kinetics. [Summary of the Invention]

[0004] The purpose of this application is to provide a positive electrode material, an electrochemical device comprising the positive electrode material, and an electronic device comprising the electrochemical device, in an attempt to solve at least one problem existing in the relevant field to some extent.

[0005] According to one aspect of this application, a cathode material is provided having a crystal structure belonging to space group Cmc21.

[0006] According to some embodiments of this application, in the X-ray diffraction pattern of the cathode material, the 003 crystal plane diffraction peak is located in the range of 12° to 18.5°.

[0007] According to some embodiments of this application, in the X-ray diffraction pattern of the cathode material, the intensity ratio of the 003 crystal plane diffraction peak to the 104 crystal plane diffraction peak is I. (003) / I (104) Satisfy: I (003) / I (104) ≥1.8. According to some other embodiments of this application, 1.8 ≤ I (003) / I(104) ≤2.6.

[0008] According to some embodiments of this application, the unit cell parameters of the cathode material According to some other embodiments of this application, the range of the cell parameter a is: to

[0009] According to some embodiments of this application, the unit cell parameters of the cathode material According to some other embodiments of this application, the range of the cell parameter c is: to

[0010] According to some embodiments of this application, the cell parameter c / cell parameter a of the cathode material is ≥ 4.95. According to still other embodiments of this application, the cell parameter c / cell parameter a ranges from 4.95 to 6.68. According to some embodiments of this application, the cathode material comprises a lithium transition metal oxide, wherein the interlayer spacing between Li and O ranges from [missing information]. to

[0011] According to some embodiments of this application, the cathode material includes a lithium transition metal oxide, which contains a transition metal element Me, including Ni element, and the molar percentage of Ni element is ≥50% based on the molar amount of transition metal element Me.

[0012] According to some embodiments of this application, the positive electrode material includes secondary particles composed of primary particles, wherein the average particle size of the primary particles is 0.1 μm to 1.5 μm, and the average particle size of the secondary particles is 1 μm to 30 μm.

[0013] According to some embodiments of this application, the cathode material includes Li x Ni y Co z Mn k Z q O b-a T a Z includes at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, Sr and Ce, T is a halogen, and x, y, z, k, q, a and b satisfy the following conditions: 0.2 < x ≤ 1.2, 0 < y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ k ≤ 1, 0 ≤ q ≤ 1, 1 ≤ b ≤ 2 and 0 ≤ a ≤ 1; preferably, 0.6 ≤ x ≤ 1.2, 0.5 ≤ y ≤ 1, 0 ≤ z ≤ 0.5, 0 ≤ k ≤ 0.5, 0 ≤ q ≤ 0.5, 1.5 ≤ b ≤ 2 and 0 ≤ a ≤ 0.5.

[0014] According to another aspect of this application, this application provides an electrochemical device comprising the positive electrode material described above in this application.

[0015] According to another aspect of this application, this application provides an electronic device that includes the electrochemical device described above according to this application.

[0016] The technical solution of this application has at least the following beneficial effects: the crystal structure of the cathode material provided by this application has a specific space group, which is conducive to the diffusion of metal ions such as lithium ions in the bulk phase of the material, which can improve the kinetic performance of the cathode material, and can effectively improve the capacity performance, coulombic efficiency and cycle performance of the cathode material.

[0017] Additional aspects and advantages of the embodiments of this application will be described, shown, or illustrated in part by way of implementation of the embodiments of this application in the following description. [Attached Image Description]

[0018] The accompanying drawings, necessary for describing embodiments of this application or the prior art, will be briefly described below to facilitate the depiction of embodiments of this application. It is obvious that the drawings described below represent only a portion of the embodiments in this application. Those skilled in the art can still derive other embodiments based on the structures illustrated in these drawings.

[0019] Figure 1 This is a schematic diagram of the Li and O interlayer spacing of the cathode material provided in Embodiment 1 of this application;

[0020] Figure 2 This is a schematic diagram of the Li-O interlayer spacing of the cathode material provided in Comparative Example 1 of this application;

[0021] Figure 3 A schematic diagram of Li / Ni mutual occupancy of cathode materials provided as an exemplary embodiment of this application;

[0022] Figure 4 The X-ray diffraction pattern (XRD pattern) of the cathode material provided in Example 1 of this application.

Detailed Implementation Methods

[0023] The embodiments of this application will be described in detail below. These embodiments should not be construed as limiting the scope of this application.

[0024] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0025] Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format in this document. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0026] I. Cathode Materials

[0027] High-nickel ternary cathode materials are one type of cathode material used in electrochemical devices such as lithium-ion batteries. High-nickel ternary cathode materials suffer from issues such as unimproved kinetic performance and the potential for lithium-nickel mixing during synthesis. In related technologies, optimizations to improve the kinetic performance of high-nickel ternary cathode materials generally focus on the following aspects: reducing particle size; doping the lithium layer with elements having large ionic radii; and coating the surface with fast ion conductors. However, reducing particle size decreases the material's compaction density, thus affecting its energy density. Furthermore, smaller particle sizes mean a larger specific surface area (BET), increasing side reactions between the material and the electrolyte. Doping the lithium layer with elements having large ionic radii is a common method to increase the interlayer spacing, but this method requires high precision in doping elements and processes, and the doping amount is relatively small, limiting its effectiveness. Coating the surface with fast ion conductors is an auxiliary solution and cannot fundamentally solve the diffusion problem of metal ions such as lithium ions in the bulk phase of the cathode material, resulting in poor performance in improving the material's kinetics.

[0028] Based at least on the above insights into the prior art, and given that cathode materials are crucial to the electrochemical performance of electrochemical devices, this application conducts further extensive research on the structure and properties of cathode materials in order to improve the electrochemical performance of electrochemical devices, especially to improve the discharge specific capacity, first-cycle coulombic efficiency and cycle performance of electrochemical devices, and strives to obtain an electrochemical device with superior electrochemical performance.

[0029] In one aspect of this application, a cathode material is provided. According to some embodiments of this application, the cathode material has a crystal structure belonging to space group Cmc21.

[0030] The cathode material provided in this application has a specific space group, Cmc21, which increases the range of lithium layer spacing, facilitates the diffusion of lithium ions in the bulk phase of the material, makes the structure more stable, improves the kinetic performance of the cathode material, and can effectively improve the capacity performance, coulombic efficiency and cycle performance of the cathode material.

[0031] In some embodiments, the 003 crystal plane diffraction peak in the X-ray diffraction (XRD) spectrum of the cathode material is located in the range of 12° to 18.5°. When the 003 crystal plane diffraction peak is within this range, the cathode material exhibits superior kinetic performance and structural stability, resulting in better discharge specific capacity, first-cycle coulombic efficiency, and cycle performance.

[0032] In some embodiments, in the X-ray diffraction (XRD) spectrum of the cathode material, the intensity ratio of the 003 crystal plane diffraction peak to the 104 crystal plane diffraction peak is I. (003) / I (104) Satisfy: I (003) / I (104) ≥1.8. In some embodiments, in the XRD pattern of the cathode material, the intensity ratio I of the 003 crystal plane diffraction peak to the 104 crystal plane diffraction peak is... (003) / I (104) Satisfy: I (003) / I (104) ≥2.0. In some embodiments, in the XRD pattern of the cathode material, the intensity ratio I of the 003 crystal plane diffraction peak to the 104 crystal plane diffraction peak is... (003) / I (104) Satisfy: 1.8≤I (003) / I (104) ≤2.6.

[0033] The cathode material according to the embodiments of this application has a crystal structure belonging to space group Cmc21, and the intensity ratio of the diffraction peaks of the 003 and 104 crystal planes in the XRD pattern is I (003) / I (104) Satisfy: I (003) / I (104) With a concentration ≥1.8, the diffusion of Li between the Li layer and the transition metal layer in the material can be improved, the occupancy of Li in the transition metal layer is appropriate, and the crystal structure is more thermodynamically stable. Thus, the cathode material is suitable for realizing high-capacity devices. Similarly, it can be considered that the cathode material is also suitable for realizing electrochemical devices with excellent cycle performance.

[0034] In some embodiments, the range of the cell parameter 'a' of the positive electrode material is: In some embodiments, the range of the cell parameter c is: In some embodiments, the ratio of cell parameter c to cell parameter a is ≥4.95. In some embodiments, the range of cell parameter a of the cathode material is... to In some embodiments, the range of the cell parameter c is: to In some embodiments, the ratio of cell parameter c to cell parameter a ranges from 4.95 to 6.68. When the cell parameter a, cell parameter c, and the ratio of cell parameter c to cell parameter a of the cathode material are within the above ranges, the structure of the cathode material is more stable, resulting in better cycle performance; at the same time, it is more conducive to the extraction and insertion of lithium ions, which can better improve the discharge specific capacity and coulombic efficiency of the cathode material.

[0035] In some embodiments, the cathode material comprises a lithium transition metal oxide, wherein the interlayer spacing between Li and O ranges from [value missing]. to In some embodiments, the cathode material comprises a lithium transition metal oxide, wherein the interlayer spacing between Li and O ranges from [value missing]. to In some embodiments, the cathode material comprises a lithium transition metal oxide, wherein the interlayer spacing between Li and O ranges from [value missing]. to Increasing the interlayer spacing of lithium layers facilitates the diffusion of lithium ions, enabling them to migrate more smoothly. This, in turn, improves the discharge specific capacity and coulombic efficiency of the cathode material, and enhances its cycle performance.

[0036] In some embodiments, the cathode material comprises a lithium transition metal oxide containing a transition metal element Me, wherein the transition metal element Me includes Ni, and the molar percentage of Ni is ≥50% based on the molar amount of the transition metal element Me. In some embodiments, the cathode material comprises a lithium transition metal oxide containing a transition metal element Me, wherein the transition metal element Me includes Ni, and the molar percentage of Ni is ≥70% based on the molar amount of the transition metal element Me. In some embodiments, the cathode material comprises a lithium transition metal oxide containing a transition metal element Me, wherein the transition metal element Me includes Ni, and the molar percentage of Ni is ≥80% based on the molar amount of the transition metal element Me. In some embodiments, the cathode material is a high-nickel ternary cathode material, i.e., the molar percentage of Ni (relative to the total metal elements other than Li) is not less than 50%.

[0037] In some embodiments, the cathode material contains sulfur (S), and the mass percentage of S is ≥0.1% based on the mass of the cathode material.

[0038] In some embodiments, the cathode material includes secondary particles composed of primary particles, wherein the average particle size of the primary particles is 0.1 μm to 1.5 μm, and the average particle size of the secondary particles is 1 μm to 30 μm.

[0039] The particle size of the cathode material affects the capacity, rate performance, and cycle performance of an electrochemical device. Generally speaking, in cathode materials that include secondary particles formed from primary particles, a suitable primary particle size is beneficial for improving the cycle performance and rate performance of the cathode material. Furthermore, it allows the cathode active material to achieve higher capacity utilization, thereby increasing the energy density of the battery.

[0040] When the average particle size of the cathode material is within an appropriate range, the electrochemical device can simultaneously possess good kinetic performance and high energy density, which is beneficial to improving the overall performance of the material and the electrochemical device.

[0041] In some embodiments, the average particle size of the secondary particles is 5 μm to 20 μm. In some embodiments, the average particle size of the secondary particles is 10 μm to 20 μm.

[0042] In some embodiments, the positive electrode material includes Li x Ni y Co z Mn k Z q O b-a T a Z includes at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, and Ce, T is a halogen, and x, y, z, k, q, a, and b satisfy the following conditions: 0.2 < x ≤ 1.2, 0 < y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ k ≤ 1, 0 ≤ q ≤ 1, 1 ≤ b ≤ 2, and 0 ≤ a ≤ 1. Preferably, in some embodiments, 0.6 ≤ x ≤ 1.2, 0.5 ≤ y ≤ 1, 0 ≤ z ≤ 0.5, 0 ≤ k ≤ 0.5, 0 ≤ q ≤ 0.5, 1.5 ≤ b ≤ 2, and 0 ≤ a ≤ 0.5.

[0043] In some embodiments, the cathode material may include at least one of lithium-containing transition metal oxides such as lithium cobalt oxide, lithium nickel cobalt manganese oxide (ternary cathode material), and lithium manganese oxide. In some embodiments, the cathode material includes a high-nickel ternary cathode material.

[0044] Typically, high-nickel ternary cathode materials are prepared by using β-phase R3m precursor Ni. 1-x-y Co x Mn y The mixture of (OH)₂ and lithium salt LiOH·H₂O was sintered under an oxygen atmosphere. However, during the preparation process, the Ni in the precursor was in the +2 valence state, which was difficult to completely oxidize to the +3 valence state. 2+ Ionic radius and Li + With very similar radii, lithium-nickel mixing easily occurs during synthesis, preventing some lithium from being utilized and thus reducing the material's capacity. Furthermore, even if high-nickel cathode materials with standard stoichiometry are obtained by controlling the synthesis process conditions, the use of β-Ni precursors can still lead to issues. 1-x-y Co x Mn y (OH)2 results in a smaller lithium layer spacing in high-nickel materials, making lithium-ion diffusion difficult and reducing kinetic performance.

[0045] According to embodiments of this application, the cathode material can be a high-nickel ternary cathode material, which can be prepared by the following method: α-Ni 1-x-y Co x Mn y (OH)2 serves as a precursor for ternary cathode materials, enabling α-Ni 1-x-y Co x Mn y (OH)₂, when mixed with lithium salts and sintered in a solid-state process, can produce a cathode material with a crystal structure belonging to space group Cmc₂₁. Furthermore, the resulting cathode material exhibits a larger interlayer spacing; for example, the interlayer spacing between Li and O ranges from [insert range here]. to Because the lithium interlayer spacing is much larger than the Ni-O bond length, it suppresses the easy formation of Li / Ni intersubstituents in the lithium layer, thus alleviating the problems of poor kinetic performance, high discharge temperature rise at high rates, and lithium-nickel mixing that exist in existing ternary materials. Of course, this cathode material is not limited to this, nor is the preparation method of the cathode material limited to this; other methods can also be used for preparation.

[0046] Unless otherwise specified, the various parameters mentioned in this specification have the general meanings known in the art and can be measured by methods known in the art, and will not be described in detail here.

[0047] II. Electrochemical Device

[0048] In some embodiments, this application provides an electrochemical device including a positive electrode, a negative electrode, an electrolyte, and a separating membrane disposed between the positive and negative electrodes.

[0049] The electrochemical device of this application can be a lithium-ion battery or a lithium metal battery, or any other suitable electrochemical device. For example, without departing from the disclosure of this application, the electrochemical device in the embodiments of this application includes any device in which an electrochemical reaction occurs, and specific examples include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, which includes, but is not limited to, lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries. The electrochemical device of this application is an electrochemical device having a positive electrode with a positive electrode active material capable of adsorbing and releasing metal ions and a negative electrode active material capable of adsorbing and releasing metal ions. Its main feature is that it includes any of the above-mentioned positive electrode materials of this application. Therefore, the electrochemical device of the embodiments of this application, by including the above-mentioned positive electrode materials, can alleviate the problems of poor kinetic performance of positive electrode materials and lithium-nickel mixing during the synthesis process in existing electrochemical devices, and can improve the kinetic performance and cycle performance of the electrochemical device.

[0050] The positive electrode material used in the electrochemical device of this application is any of the positive electrode materials mentioned above in this application. In addition, the positive electrode material used in the electrochemical device of this application may also include other positive electrode materials that do not depart from the scope of this application.

[0051] positive electrode

[0052] In some embodiments, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes the aforementioned positive electrode material.

[0053] In some embodiments, the positive electrode active material layer further includes a binder. The binder can improve the bonding between the positive electrode material particles and the bonding between the positive electrode material and the positive electrode current collector. In some embodiments, the binder includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon, etc.

[0054] In some embodiments, the adhesive includes at least one of polyvinylidene fluoride (PVDF), carboxymethyl cellulose, and styrene-butadiene rubber.

[0055] In some embodiments, the positive electrode active material layer further includes a conductive agent to impart conductivity to the electrode. The conductive agent may include any conductive material as long as it does not cause unwanted chemical changes. In some embodiments, the conductive agent includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material may be selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof; the metal-based material may be selected from metal powder, metal fiber, copper, nickel, aluminum, silver, or any combination thereof; and the conductive polymer may be selected from polyphenylene derivatives.

[0056] In some embodiments, the conductive agent includes at least one of conductive carbon black, acetylene black, graphene, Ketjen black, and conductive nanotubes.

[0057] The binder and conductive agent in the above-mentioned positive electrode active material layer, as well as their types and contents, are not subject to specific restrictions and can be selected according to actual needs.

[0058] In some embodiments, the positive current collector can be a commonly used positive current collector in the art. The positive current collector is a metal, such as, but not limited to, aluminum foil or nickel foil.

[0059] In some embodiments, the structure of the positive electrode is a positive electrode structure known in the art and suitable for use in electrochemical devices.

[0060] In some embodiments, the method for preparing the positive electrode is a method known in the art for preparing a positive electrode that can be used in electrochemical devices. For example, the positive electrode can be obtained by mixing a positive electrode material, a conductive agent, and a binder in a solvent to prepare a slurry, and then coating the slurry onto a current collector. In some embodiments, the solvent may include, but is not limited to, water, N-methylpyrrolidone, etc.

[0061] negative electrode

[0062] In some embodiments, the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. In some embodiments, the negative electrode active material layer includes a negative electrode active material, which may include a material capable of reversibly inserting / deintercalating lithium ions, lithium metal, lithium metal alloy, or transition metal oxide. In some embodiments, the negative electrode active material includes at least one of carbon material or silicon material, wherein the carbon material includes at least one of graphite and hard carbon, and the silicon material includes at least one of silicon, silicon oxide, silicon carbide, or silicon alloy. In some embodiments, a lithium-containing metal sheet is used as the negative electrode active material layer. For example, the negative electrode current collector includes two opposing surfaces in its thickness direction, and the lithium-containing metal sheet is stacked on either or both of the two surfaces of the negative electrode current collector. The lithium-containing metal sheet may be formed on the negative electrode current collector by at least one of mechanical rolling, vapor deposition, or electroless plating.

[0063] In some embodiments, the negative current collector can be a negative current collector commonly used in the art. The negative current collector can be made of materials such as metal foil or porous metal plate, for example, using foil or porous plate of metals or alloys thereof such as copper, nickel, titanium or iron, such as copper foil.

[0064] In other embodiments, the negative electrode active material layer comprises a negative electrode active material, a binder, and a conductive agent. The negative electrode active material is capable of reversibly inserting and de-intercalating lithium ions. According to some embodiments of this application, the specific type of negative electrode active material is not specifically limited and can be selected according to requirements.

[0065] In some embodiments, the structure and preparation method of the negative electrode are known in the art and can be used in electrochemical devices.

[0066] electrolyte

[0067] The electrolyte used in the embodiments of this application can be any electrolyte known in the prior art. Electrolytes can be divided into aqueous electrolytes and non-aqueous electrolytes. Compared to aqueous electrolytes, electrochemical devices using non-aqueous electrolytes can operate over a wider voltage window, thereby achieving higher energy densities. In some embodiments, the non-aqueous electrolyte includes an organic solvent and an electrolyte.

[0068] The electrolytes that can be used in the electrolytes of the embodiments of this application include, but are not limited to: inorganic lithium salts, such as LiClO4, LiAsF6, LiPF6, LiBF4, LiSbF6, LiSO3F, LiN(FSO2)2, etc.; fluorinated organic lithium salts, such as LiCF3SO3, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,3-hexafluoropropane disulfonylimide lithium, cyclic 1,2-tetrafluoroethane disulfonylimide lithium, LiPF4(CF3)2, LiN(C2F5SO2)2, etc. The electrolytes include F3SO2)(C4F9SO2), LiC(CF3SO2)3, LiPF4(CF3SO2)2, LiPF4(C2F5)2, LiPF4(C2F5SO2)2, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, and LiBF2(C2F5SO2)2; lithium salts containing dicarboxylic acid complexes, such as lithium bis(oxalate)borate, lithium difluorooxalate borate, lithium tri(oxalate)phosphate, lithium difluorobis(oxalate)phosphate, and lithium tetrafluoro(oxalate)phosphate. Furthermore, one of the above electrolytes can be used alone, or two or more can be used simultaneously.

[0069] The organic solvents that can be used in the electrolytes of this application embodiments may be any organic solvent known in the prior art. In some embodiments, the organic solvent includes, but is not limited to: carbonate compounds, ester-based compounds, ether-based compounds, ketone-based compounds, alcohol-based compounds, aprotic solvents, or combinations thereof. Examples of carbonate compounds include, but are not limited to, chain carbonate compounds, cyclic carbonate compounds, fluorocarbonate compounds, or combinations thereof. In some embodiments, the organic solvent includes at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, propyl propionate, and ethyl propionate.

[0070] Separating membrane

[0071] The separator can be any material suitable for separators in electrochemical energy storage devices, for example, it can be one or more of the following: polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fibers.

[0072] This application does not impose any particular limitations on the material and shape of the separator; any known porous separator with electrochemical and chemical stability can be selected. In some embodiments, the separator is, for example, a single-layer or multi-layer film selected from one or more of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride (PVDF).

[0073] III. Application

[0074] In some embodiments, this application provides an electronic device that includes the aforementioned electrochemical device.

[0075] The cathode material according to the embodiments of this application can alleviate the problems of poor kinetic performance, high temperature rise during high-rate discharge, and lithium-nickel mixing of existing cathode materials, and can improve the discharge specific capacity, first-cycle coulombic efficiency and cycle performance of electrochemical devices, making the electrochemical devices manufactured thereby suitable for electronic devices in various fields.

[0076] The application of the electrochemical device in this application is not particularly limited, and it can be used in any electronic device known in the prior art. For example, such electronic devices include, but are not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc. In addition to being applicable to the electronic devices exemplified above, the electrochemical device in this application is also applicable to energy storage power stations, marine transport vehicles, and air transport vehicles. Air transport vehicles include both intra-atmosphere and extra-atmosphere air transport vehicles.

[0077] The following embodiments describe the contents of this invention in more detail. These embodiments are merely illustrative and are not intended to limit the scope of the invention. Various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all reagents used in the following embodiments and comparative examples are commercially available or synthesized using conventional methods and can be used directly without further processing. The instruments used in the embodiments are also commercially available.

[0078] IV. Examples

[0079] Preparation of lithium secondary batteries

[0080] The cathode materials used in the examples and comparative examples were prepared into lithium secondary batteries using the following preparation method.

[0081] (1) Preparation of the positive electrode: The positive electrode material prepared in the following examples and comparative examples, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were thoroughly mixed in N-methylpyrrolidone at a weight ratio of 90:10:10 to form a positive electrode slurry. The obtained positive electrode slurry was then uniformly coated onto the aluminum foil of the positive electrode current collector. After drying, cold pressing, slitting, and cutting, the positive electrode was obtained. The obtained positive electrode was a circular sheet with a diameter of 14 mm.

[0082] (2) Preparation of negative electrode: A lithium metal sheet with a diameter of 18 mm is used as the negative electrode.

[0083] (3) Preparation of the isolation membrane: Polyethylene porous membrane is used as the isolation membrane, which is a circular piece with a diameter of 18 mm.

[0084] (4) Preparation of electrolyte: In a dry argon atmosphere glove box, ethylene carbonate (EC), diethyl carbonate (DEC) and propylene carbonate (PC) are mixed evenly in a mass ratio of 3:4:3. Then, fully dried lithium salt LiPF6 is dissolved in the above non-aqueous solvent to form an electrolyte, wherein the content of LiPF6 is 1 mol / L.

[0085] (5) Assembly of lithium secondary batteries: The obtained positive electrode, separator, negative electrode, electrolyte, battery case and other related accessories are transferred into a glove box with a water content of less than 11ppm; the batteries are assembled in a stacking order from bottom to top and the electrolyte is injected; the batteries are packaged on a packaging machine to obtain lithium secondary batteries.

[0086] Discharge specific capacity test and initial efficiency test

[0087] The lithium secondary battery was charged to 4.3V at a rate of 0.1C, then charged at a constant voltage to 0.05C, and then discharged to 2.8V at a rate of 0.1C using DF203946PCT10, thus obtaining the initial charge capacity and the initial discharge capacity.

[0088] Discharge specific capacity (mAh / g) = Initial discharge capacity (mAh) / Mass of cathode material (g).

[0089] First-time efficiency (%) = First-time discharge capacity (mAh) / First-time charge capacity (mAh) × 100%.

[0090] Cyclic capacity retention test

[0091] An accelerated cycling method was used to raise the cutoff voltage to 4.5V. The lithium secondary battery that had completed the discharge specific capacity test was charged to 4.5V at 0.5C at 25℃, then charged at a constant voltage to 0.05C, and then discharged to 2.8V at 0.5C. This cycle was repeated 50 times, and then the capacity of the lithium secondary battery after 50 cycles was calculated.

[0092] Cycle capacity retention = (Discharge capacity at 50th cycle (mAh) / Discharge capacity at first cycle (mAh)) × 100%.

[0093] Methods for measuring the average particle size of primary and secondary particles

[0094] Taking primary particles as an example, the sample is spread on the test sample stage, and images of different areas of the sample are taken using a scanning electron microscope. Then, using image analysis software, 20 primary particles with complete and unobstructed shapes are randomly selected from the SEM images, and the area of ​​each of these primary particles is calculated. Next, assuming that the primary particles are spherical, their particle diameter R is calculated using the following formula: R = 2 × (S / π)¹ / ², where S is the area of ​​the primary particle. The particle diameter R of the primary particles is calculated from 5 SEM images, and the particle diameters of the resulting 100 (20 × 5) primary particles are arithmetically averaged to obtain the average particle diameter of the primary particles.

[0095] The method for measuring the average particle size of secondary particles is the same as that for primary particles.

[0096] The following will describe in detail the specific embodiments of the cathode material provided in this application, as well as the performance test results of each embodiment and comparative example.

[0097] Comparative Example 1

[0098] Comparative Example 1: A mixed solution containing NiSO4, CoSO4, and MnSO4 was prepared according to the elemental molar ratio Ni:Co:Mn = 80:10:10. This mixed solution was then mixed with a precipitant (NaOH solution) and a complexing agent (ammonia water) and reacted. The concentration of ammonia water was adjusted to 6 g / L and the pH value was adjusted to 12 under stirring. When the particle size in the reaction slurry reaches 8 μm, the reactor is stopped. After the volume of the supernatant is reduced to 1 / 4 of the total volume of the reaction slurry, concentration is started and stirring is carried out. Stirring is stopped when the large particles reach 10 μm. The mixture is aged at 58℃ for 10 h to obtain a β-phase nickel-cobalt-manganese precursor TM(OH)2 (TM = Ni / Co / Mn) with an average particle size Dv50 of 10 μm. The crystal structure of this precursor is an R3m layered structure. The obtained β-phase nickel-cobalt-manganese precursor TM(OH)2 and lithium hydroxide are ground and mixed evenly, and calcined at 750℃ in an oxygen atmosphere for 10 h to obtain lithium nickel-cobalt-manganese oxide agglomerates with a molar ratio of Ni:Co:Mn = 80:10:10 and an average particle size Dv50 of 10 μm, which is the cathode material. The crystal structure of this cathode material is an R3m layered structure, the molar percentage of nickel is 80%, and the average particle size Dv50 is 10 μm.

[0099] Examples 1 to 8

[0100] Example 1: A mixed solution containing NiSO4, CoSO4, and MnSO4 was prepared according to the elemental molar ratio Ni:Co:Mn = 80:10:10. The mixed solution was then mixed with a precipitant (NaOH solution) and a complexing agent (ammonia water) and the ammonia water concentration was adjusted to 5.5 g / L and the pH value was adjusted to 11 under stirring. When the particle size in the reaction slurry reaches 8 μm, the reactor is stopped. After the volume of the supernatant is 1 / 4 of the total volume of the reaction slurry, concentration is started and stirring is carried out. Stirring is stopped when the large particles reach 10 μm. The mixture is aged at 58℃ for 10 h to obtain an α-phase nickel-cobalt-manganese precursor TM(OH)2 (TM = Ni / Co / Mn) with an average particle size Dv50 of 10 μm. The crystal structure of this precursor is an R3m layered structure. The obtained α-phase nickel-cobalt-manganese precursor TM(OH)2 and lithium hydroxide are ground and mixed evenly, and calcined at 750℃ in an oxygen atmosphere for 10 h to obtain lithium nickel-cobalt-manganese oxide agglomerates with a molar ratio of Ni:Co:Mn = 80:10:10 and an average particle size Dv50 of 10 μm, which is the cathode material. The crystal structure of this cathode material is a Cmc21 layered structure, the molar percentage of nickel is 80%, and the average particle size Dv50 is 10 μm.

[0101] Example 2: The difference from Example 1 is that the ammonia concentration was adjusted to 2.5 g / L and the pH value to 8 under stirring, and the aging time was 22 h.

[0102] Example 3: The difference from Example 1 is that the ammonia concentration was adjusted to 3g / L and the pH value to 8.5 under stirring, and the aging time was 20h.

[0103] Example 4: The difference from Example 1 is that the ammonia concentration was adjusted to 3.5 g / L and the pH value to 9 under stirring, and the aging time was 18 h.

[0104] Example 5: The difference from Example 1 is that the ammonia concentration was adjusted to 4 g / L and the pH value to 9.5 under stirring, and the aging time was 16 h.

[0105] Example 6: The difference from Example 1 is that the ammonia concentration was adjusted to 4.5 g / L and the pH value to 10 under stirring, and the aging time was 14 h.

[0106] Example 7: The difference from Example 1 is that the ammonia concentration was adjusted to 5 g / L and the pH value to 10.5 under stirring, and the aging time was 12 h.

[0107] Example 8: The difference from Example 1 is that the ammonia concentration was adjusted to 5.5 g / L and the pH value was 11 under stirring. Sr element (molar ratio Sr / (Ni+Co+Mn)=0.01%) was introduced while grinding and mixing the precursor and lithium hydroxide. The calcination temperature was 730℃.

[0108] Table 1

[0109]

[0110]

[0111] As can be seen from the data in Table 1, Example 1, with its space group Cmc21 crystal structure, exhibits significantly improved capacity retention at high voltage compared to Comparative Example 1, which uses a conventional precursor and has an R3m layered crystal structure. Furthermore, its discharge specific capacity and first-pass efficiency are also enhanced. This demonstrates that the use of α-phase Ni... 1-x- y Co x Mn y (OH)2, as a precursor for ternary cathode materials, can produce cathode materials with a larger Li-O interlayer spacing in the Cmc21 structure. Since the Li-O interlayer spacing is much larger than the Ni-O bond length, it suppresses the formation of Li / Ni mutual occupancy in the lithium layer, solving problems such as poor kinetics, high temperature rise during high-rate discharge, and lithium-nickel mixing in ternary materials. This results in batteries using this cathode material having better capacity performance, first-time efficiency, and cycle performance.

[0112] As can be seen from Examples 1 to 8, during the preparation of the cathode material, the intensity ratio of the 003 crystal plane diffraction peak to the 104 crystal plane diffraction peak can be controlled by adjusting the ammonia concentration, pH value, aging time, and the addition of large ionic radius elements during the preparation of the α-phase precursor. (003) / I (104) The cell parameters c, c / a value, and Li-O interlayer spacing were analyzed. It can be seen that as the 2θ angle of the 003 diffraction peak decreases, the cell parameter c gradually increases, the a-axis changes little, c / a increases, and the Li-O interlayer spacing increases, resulting in better crystallinity and less Li / Ni mutual occupancy in the cathode material.

[0113] Examples 9 to 21

[0114] Example 9: The difference from Example 8 is that the Sr / (Ni+Co+Mn) molar ratio is 0.5%;

[0115] Example 10: The difference from Example 8 is that the ammonia concentration was adjusted to 4 g / L and the pH value to 9.5 under stirring, and the aging time was 16 h. The Sr / (Ni+Co+Mn) molar ratio was 5%.

[0116] Examples 11 to 21 differ from Example 9 in that the types of doping elements introduced are different, namely: Mg, Ca, Ba, Al, Y, Zr, B, W, Ta, Nb, and La.

[0117] Table 2 shows the relevant performance parameters of the cathode materials in Examples 9 to 21 and the corresponding battery performance. As can be seen from Examples 9 to 21, during the preparation of the cathode material, the interlayer spacing can be improved by incorporating elements with large ionic radii into the lithium layer and controlling their doping amount. This results in better crystallinity and less Li / Ni inter-site occupation in the cathode material, solving problems such as poor kinetics, high temperature rise during high-rate discharge, and lithium-nickel mixing in ternary materials. Consequently, batteries using this cathode material exhibit better capacity performance, initial efficiency, and cycle performance.

[0118] Table 2

[0119]

[0120]

[0121] Examples 22 to 28

[0122] Examples 22 to 28 differ from Example 1 in that the molar content of Ni in the cathode material is different. During the preparation of the cathode material, cathode materials with different molar percentages of Ni were obtained by adjusting the proportions of nickel salt, cobalt salt, and manganese salt.

[0123] Example 22: The difference from Example 1 is that the Ni:Co:Mn molar ratio is 50:20:30;

[0124] Example 23: The difference from Example 1 is that the Ni:Co:Mn molar ratio is 60:20:20;

[0125] Example 24: The difference from Example 1 is that the Ni:Co:Mn molar ratio is 70:10:20;

[0126] Example 25: The difference from Example 1 is that the Ni:Co:Mn molar ratio is 83:12:5;

[0127] Example 26: The difference from Example 1 is that the Ni:Co:Mn molar ratio is 88:7:5;

[0128] Example 27: The difference from Example 1 is that the Ni:Co:Mn molar ratio is 90:5:5;

[0129] Example 28: The difference from Example 1 is that the Ni:Co:Mn molar ratio is 100:0:0;

[0130] Table 3

[0131]

[0132]

[0133] As shown in Table 3, different Ni elements have a certain impact on the battery's discharge specific capacity, initial efficiency, and cycle performance. With increasing Ni content, the battery's discharge specific capacity continuously increases, while its initial efficiency continuously decreases. Therefore, an appropriate Ni content can improve the battery's discharge specific capacity, initial efficiency, and cycle performance to a certain extent.

[0134] Examples 29 to 34

[0135] The difference between Examples 29 to 34 and Example 1 lies in the different average particle sizes of the cathode materials. During the preparation of the cathode materials, cathode materials with different average particle sizes were obtained by controlling the reaction time of the α-phase precursor.

[0136] Example 29: The difference from Example 1 is that when the particle size in the reaction slurry reaches 0.8 μm, the reactor is stopped, the mixture is concentrated, and stirred. Stirring is stopped when the large particles reach 1 μm.

[0137] Example 30: The difference from Example 1 is that when the particle size in the reaction slurry reaches 2.4 μm, the reactor is stopped, the mixture is concentrated, and the mixture is stirred. Stirring is stopped when the large particles reach 3 μm.

[0138] Example 31: The difference from Example 1 is that when the particle size of the reaction slurry reaches 4 μm, the reactor is stopped, the mixture is concentrated, and stirred. Stirring is stopped when the large particles reach 5 μm.

[0139] Example 32: The difference from Example 1 is that when the particle size in the reaction slurry reaches 9.6 μm, the reactor is stopped, the mixture is concentrated, and stirred. Stirring is stopped when the large particles reach 12 μm.

[0140] Example 33: The difference from Example 1 is that when the particle size of the reaction slurry reaches 16 μm, the reactor is stopped, the mixture is concentrated, and stirred. Stirring is stopped when the large particles reach 20 μm.

[0141] Example 34: The difference from Example 1 is that when the particle size of the reaction slurry reaches 24 μm, the reactor is stopped, the mixture is concentrated, and stirred. Stirring is stopped when the large particles reach 30 μm.

[0142] Table 4 shows the relevant performance parameters of the cathode materials in Examples 29 to 34 and the performance of the corresponding batteries.

[0143] Table 4

[0144]

[0145]

[0146] As shown in Table 4, different average secondary particle sizes have a certain impact on the battery's discharge specific capacity, initial efficiency, and cycle performance. With increasing average secondary particle size, the battery's discharge specific capacity decreases, while its initial efficiency and cycle performance increase. Therefore, a suitable average secondary particle size can improve the battery's discharge specific capacity, initial efficiency, and cycle performance to a certain extent.

[0147] also, Figure 1 A schematic diagram of the Li-O interlayer spacing of the cathode material provided in Embodiment 1 of this application is shown; Figure 2 A schematic diagram of the Li-O interlayer spacing of the cathode material provided in Comparative Example 1 of this application is shown. Combined with... Figure 1 and Figure 2 It can be seen that the interlayer spacing between Li and O in the cathode material of Example 1 of this application is much larger than that between Li and O in the cathode material of Comparative Example 1.

[0148] Figure 3A schematic diagram of the Li / Ni mutual occupancy of the cathode material provided in the embodiments of this application is shown. Figure 4 The X-ray diffraction pattern (XRD pattern) of the cathode material provided in Embodiment 1 of this application is shown. In this pattern, Li / Ni cations are mixed, and the larger the ratio of cell parameter c to cell parameter a, the lower the lithium-nickel mixing.

[0149] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A positive electrode material, characterized in that, The cathode material has a crystal structure belonging to space group Cmc21. The cathode material includes a lithium transition metal oxide, which is lithium nickel cobalt manganese oxide. The lithium transition metal oxide contains a transition metal element Me, which includes Ni. Based on the molar amount of the transition metal element Me, the molar percentage of Ni is ≥50%. In the X-ray diffraction pattern of the cathode material, the 003 crystal plane diffraction peak is located in the range of 12° to 18.5°, and the intensity ratio of the 003 crystal plane diffraction peak to the 104 crystal plane diffraction peak is I. (003) / I (104) Satisfy: 1.8≤I (003) / I (104) ≤2.3; The cell parameter c / cell parameter a is ≥4.95 and ≤5.74; the interlayer spacing between Li and O in the lithium transition metal oxide is in the range of 2.7 Å to 3.7 Å.

2. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following conditions a) to b): a) Cell parameter a ≥ 2.90 Å; b) Cell parameter c ≥ 14.25 Å.

3. The cathode material according to claim 1, characterized in that, The cathode material includes secondary particles composed of primary particles, wherein the average particle size of the primary particles is 0.1 μm to 1.5 μm, and the average particle size of the secondary particles is 1 μm to 30 μm.

4. The cathode material according to any one of claims 1 to 3, characterized in that, The cathode material includes Li x Ni y Co z Mn k Z q O b-a T a Z includes at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, Sr and Ce, T is a halogen, and x, y, z, k, q, a and b satisfy the following conditions: 0.2 < x ≤ 1.2, 0 < y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ k ≤ 1, 0 ≤ q ≤ 1, 1 ≤ b ≤ 2 and 0 ≤ a ≤ 1, respectively.

5. The positive electrode material according to claim 4, characterized in that, 0.6≤x≤1.2, 0.5≤y≤1, 0≤z≤0.5, 0≤k≤0.5, 0≤q≤0.5, 1.5≤b≤2, and 0≤a≤0.

5.

6. An electrochemical device, characterized in that, The electrochemical device includes the positive electrode material as described in any one of claims 1 to 5.

7. An electronic device, characterized in that, The electronic device includes the electrochemical device as described in claim 6.

Images