Cathode materials, electrochemical devices, and electrical devices

Abstract

The positive electrode material includes lithium manganese oxide. The Raman spectrum of the positive electrode material is at 401 cm ‑1 Up to 410cm ‑1 There is a characteristic peak 1 at 598cm ‑1 Up to 611cm ‑1 There is a characteristic peak in the range of 2. The positive electrode material has a high charge capacity and excellent structural stability, which can improve the cycle performance and storage performance of the electrochemical device on the basis of greatly improving the energy density of the electrochemical device.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a positive electrode material, an electrochemical device, and an electrical device. Background Art

[0002] In order to solve serious problems such as the global energy crisis, environmental pollution, climate change, and low-carbon economy, the research and development and application of power sources in the fields of electric vehicles, large-scale power supplies, and energy storage have become inevitable.

[0003] Spinel LiMn2O4 and olivine-type LiFePO4 are widely used as cathode materials in lithium-ion batteries due to their low cost, safety, and reliability. However, these materials also suffer from low charge and discharge capacity, which in turn reduces the energy density of lithium-ion batteries.

[0004] To improve the energy density of lithium-ion batteries based on these materials, existing technologies often employ methods such as increasing the Li / Mn ratio of spinel LiMn2O4 materials, doping with high-valent cations, or mixing high-energy-density cathode materials such as ternary materials. However, increasing the Li / Mn ratio or doping with high-valent cations can significantly degrade the high-temperature cycling performance of lithium-ion batteries, while mixing high-energy-density cathode materials such as ternary materials can significantly increase the cost of lithium-ion batteries. Summary of the Invention

[0005] In view of the above-mentioned problems existing in the prior art, the present application provides a positive electrode material and an electrochemical device comprising the positive electrode material. The positive electrode material of the present application has a high charge capacity and excellent structural stability, thereby greatly improving the energy density of the electrochemical device and improving the cycle and storage performance of the electrochemical device.

[0006] In a first aspect, the present application provides a positive electrode material comprising lithium manganese oxide, wherein the Raman spectrum of the positive electrode material is at 401 cm -1 Up to 410cm -1 There is a characteristic peak 1 at 598cm -1 Up to 611cm -1There is a characteristic peak 2 in the range. Among them, characteristic peak 1 is the characteristic peak of the orthorhombic phase in lithium manganese oxide, and characteristic peak 2 is the characteristic peak of the monoclinic phase in lithium manganese oxide. On the one hand, the orthorhombic phase and monoclinic phase in lithium manganese oxide have a high lithium storage capacity, which can provide a high charge capacity, thereby greatly improving the energy density of the electrochemical device; on the other hand, the monoclinic phase coexists with the orthorhombic phase to form a solid solution, which can improve the structural stability of lithium manganese oxide in the charged state of the electrochemical device. The solid solution formed by the coexistence of the two phases has oxygen vacancies, which can promote the release of lithium ions, thereby further improving the charge capacity of lithium manganese oxide; at the same time, the presence of the orthorhombic phase and monoclinic phase composite phase structure in lithium manganese oxide can stabilize the structure of Mn and reduce the lattice distortion of the octahedron, thereby improving the stability of the crystal structure of lithium manganese oxide in a highly delithiated state, thereby inhibiting the dissolution of the Mn element and improving the cycle and storage performance of the electrochemical device.

[0007] In some embodiments, the half-peak width of characteristic peak 1 is H1, and the half-peak width of characteristic peak 2 is H2, satisfying: H1≤25cm -1 、H2≤30cm -1 The half-peak width H1 of characteristic peak 1 and the half-peak width H2 of characteristic peak 2 are within the above ranges, and both the orthorhombic phase and the monoclinic phase in the lithium manganese oxide have high crystalline regularity, which can inhibit the structural phase transition during cycling and storage, thereby improving the cycling and storage performance of the electrochemical device.

[0008] In some embodiments, the peak area of ​​characteristic peak 1 is S1, and the peak area of ​​characteristic peak 2 is S2, satisfying: 1≤S2 / S1≤5.

[0009] In some embodiments, 1≤S2 / S1≤1.3, or 2.2≤S2 / S1≤5. When S2 / S1 is within the above range, there is a large difference in the content of the orthorhombic phase and the monoclinic phase in the lithium manganese oxide, which can synergistically form a solid solution, promote the release of Li ions from the lithium manganese oxide, and thus further improve the charge capacity of the lithium manganese oxide.

[0010] In some embodiments, the Raman spectrum of the positive electrode material is at 270 cm -1 Up to 279cm -1 There is a characteristic peak 3 in the Raman spectrum of the positive electrode material. The presence of characteristic peak 3 indicates that the monoclinic phase in the lithium manganese oxide has a high crystalline order, which is conducive to the release of lithium ions during charging, thereby improving the charging capacity of the electrochemical device.

[0011] In some embodiments, the half-peak width of characteristic peak 3 is H3, which satisfies: H3≤35cm -1The half-maximum width H3 of characteristic peak 3 is within this range. On the one hand, its crystallinity is relatively complete, which can provide a higher lithium removal capacity. On the other hand, the particle size of individual crystals is small, and the solid-phase diffusion path of lithium ions in the material is short, which can effectively improve the kinetic performance of lithium insertion and extraction in the positive electrode material.

[0012] In some embodiments, the positive electrode material further includes an M1 element, and based on the molar amount of the Mn element in the positive electrode material, the molar percentage of the M1 element in the positive electrode material is a1, satisfying: 0.1%≤a1≤10%, wherein the M1 element includes at least one of Al, Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, Gd, Cu, Na, Zn, Fe, Co, Ni, Cr or Ca.

[0013] In some embodiments, the positive electrode material further comprises Al. Based on the molar amount of Mn in the positive electrode material, the molar percentage of Al in the positive electrode material is b1, satisfying the following conditions: 0.1% ≤ b1 ≤ 10%. The Al content can alter the phase ratios. Excessively high or low Al content can lead to an increase in interphases in the material, which in turn increases grain boundary barriers and reduces capacity.

[0014] In some embodiments, the molar ratio of Li to Mn in the positive electrode material is c1, satisfying the following: 0.9≤c1≤1.2. Within this range, the Li / Mn molar ratio can stably generate an orthorhombic and monoclinic mixed phase, thereby increasing the energy density of the electrochemical device.

[0015] In some embodiments, the lithium manganese oxide has a lamellar structure, which facilitates the release of Li ions from the lithium manganese oxide, thereby increasing the charge capacity of the lithium manganese oxide.

[0016] In some embodiments, the lithium manganese oxide includes Li x Mn y M1 z O2, wherein 0.9≤x≤1.2, 0.9≤y≤1, 0≤z≤0.1, and M1 comprises at least one of Al, Nb, Mg, Ti, W, Ga, Zr, W, Y, V, Sr, Mo, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, Gd, Cu, Na, Zn, Fe, Co, Ni, Cr, or Ca. In some embodiments, 0.9≤x≤1.2, 0.9≤y≤1, and 0.001≤z≤0.1.

[0017] In some embodiments, the positive electrode material further includes a coating layer located on the surface of the positive electrode material, wherein the coating layer includes an M2 element, and the molar percentage of the M2 element in the coating layer is 0.05% to 2% based on the molar amount of the Mn element in the coating layer, wherein the M2 element includes at least one of S, C, B, or F. The coating layer on the surface of the positive electrode material can further inhibit the dissolution of Mn, thereby improving the cycling and storage performance of the electrochemical device.

[0018] In some embodiments, the positive electrode material also includes an Al element, and the positive electrode material includes a matrix and a coating layer. Based on the molar amount of the Mn element in the matrix, the molar percentage of the Al element in the matrix is ​​d1, and based on the molar amount of the Mn element in the coating layer, the molar percentage of the Al element in the coating layer is d2, satisfying: d2 / d1≥1.3.

[0019] In some embodiments, the residual lithium content of the positive electrode material is less than or equal to 0.05% based on the mass of the positive electrode material.

[0020] In some embodiments, the pH value of the cathode material is 11 to 12.

[0021] In a second aspect, the present application provides a method for preparing the positive electrode material of the first aspect, comprising: S1: mixing a manganese-containing oxide, a lithium source and an optional M1 element source to obtain a first mixture; subjecting the obtained first mixture to a first heat treatment under a first atmosphere condition and a first temperature condition to obtain a first lithium manganese oxide; wherein the manganese-containing oxide and the lithium source are mixed according to a lithium-manganese molar ratio Li / Mn in the range of 0.9-1.2; and the first atmosphere condition is an inert atmosphere.

[0022] In some embodiments, the inert atmosphere includes at least one of nitrogen, argon, or helium.

[0023] In some embodiments, the first temperature is from 880°C to 1100°C.

[0024] In some embodiments, the first heat treatment time is 5 hours to 20 hours.

[0025] In some embodiments, the manganese-containing oxide comprises Mn 3 O 4 .

[0026] In some embodiments, the M1 element includes at least one of Al, Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, Gd, Cu, Na, Zn, Fe, Co, Ni, Cr, or Ca.

[0027] In some embodiments, the M1 element source includes at least one of CrO2, Al2O3, MgO, TiO2, or Y2O3.

[0028] In some embodiments, the manganese-containing oxide and the M1 element source are mixed such that a molar ratio of the M1 element to the Mn element is in the range of 0.001-0.1.

[0029] In some embodiments, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium acetate, lithium nitrate, or lithium sulfate.

[0030] In some embodiments, step S1 is followed by step S2: mixing the first lithium manganese oxide synthesized in S1 with an M2 element source to obtain a second mixture, and subjecting the obtained second mixture to a second heat treatment under second atmospheric conditions and second temperature conditions to obtain a second lithium manganese oxide having a coating layer on the surface.

[0031] In some embodiments, the second atmosphere condition is an inert atmosphere. In some embodiments, the inert atmosphere comprises at least one of nitrogen, argon, or helium.

[0032] In some embodiments, the second heat treatment time is 2 hours to 5 hours. In some embodiments, the second temperature is 200°C to 600°C.

[0033] In some embodiments, the M2 element includes at least one of S, C, B, or F.

[0034] In a third aspect, the present application provides an electrochemical device comprising a positive electrode, wherein the positive electrode comprises the positive electrode material of the first aspect or the positive electrode material prepared according to the preparation method of the second aspect.

[0035] In a fourth aspect, the present application provides an electrical device comprising the electrochemical device of the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a charge and discharge curve diagram of the lithium-ion button battery of Example 1. DETAILED DESCRIPTION

[0037] To make the purpose, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of this application, rather than all the embodiments. The relevant embodiments described herein are illustrative and are used to provide a basic understanding of this application. The embodiments of this application should not be interpreted as limiting this application.

[0038] For the sake of clarity, only some numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined with any other point or single value, or with other lower limits or upper limits, to form an unspecified range.

[0039] In the description herein, unless otherwise specified, “above” and “below” include the number itself.

[0040] Unless otherwise specified, the terms used in this application have the commonly understood meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0041] 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, 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, 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 component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0042] In a first aspect, the present application provides a positive electrode material comprising lithium manganese oxide, wherein the Raman spectrum of the positive electrode material is at 401 cm -1 Up to 410cm -1 There is a characteristic peak 1 at 598cm -1 Up to 611cm -1There is a characteristic peak 2 in the range. Among them, characteristic peak 1 is the characteristic peak of the orthorhombic phase in lithium manganese oxide, and characteristic peak 2 is the characteristic peak of the monoclinic phase in lithium manganese oxide. On the one hand, the orthorhombic phase and monoclinic phase in lithium manganese oxide have a high lithium storage capacity, which can provide a high charge capacity, thereby greatly improving the energy density of the electrochemical device; on the other hand, the monoclinic phase coexists with the orthorhombic phase to form a solid solution, which can improve the structural stability of lithium manganese oxide in the charged state of the electrochemical device. The solid solution formed by the coexistence of the two phases has oxygen vacancies, which can promote the release of lithium ions, thereby further improving the charge capacity of lithium manganese oxide; at the same time, the presence of the orthorhombic phase and monoclinic phase composite phase structure in lithium manganese oxide can stabilize the structure of Mn and reduce the lattice distortion of the octahedron, thereby improving the stability of the crystal structure of lithium manganese oxide in a highly delithiation state, thereby inhibiting the dissolution of the Mn element and improving the cycle and storage performance of the electrochemical device.

[0043] In some embodiments, the half-peak width of characteristic peak 1 is H1, and the half-peak width of characteristic peak 2 is H2, satisfying: H1≤25cm -1 、H2≤30cm -1 The half-peak width H1 of characteristic peak 1 and the half-peak width H2 of characteristic peak 2 are within the above ranges, and both the orthorhombic phase and the monoclinic phase in the lithium manganese oxide have high crystalline regularity, which can inhibit the structural phase change during cycling and storage, thereby improving the cycling and storage performance of the electrochemical device. In some embodiments, H1 is 13 cm -1 , 14cm -1 , 15cm -1 , 16cm -1 , 17cm -1 、18cm -1 、19cm -1 , 20cm -1 , 21cm -1 , 22cm -1 , 23cm -1 , 24cm -1 , 25cm -1 Or any two of these values. In some embodiments, H2 is 20cm -1 , 21cm -1 , 22cm -1 , 23cm -1 , 24cm -1 , 25cm -1 , 26cm -1 , 27cm -1 , 28cm -1 、29cm -1 Or a range consisting of any two of these values.

[0044] In some embodiments, the cathode material of the present application includes lithium manganese oxide having both an orthorhombic phase structure and a monoclinic phase structure.

[0045] In some embodiments, the peak area of ​​characteristic peak 1 is S1, and the peak area of ​​characteristic peak 2 is S2, satisfying: 1≤S2 / S1≤5. In some embodiments, S2 / S1 is 1.1, 1.3, 1.5, 1.7, 2.0, 2.3, 2.5, 2.7, 3.0, 3.3, 3.5, 3.7, 4.0, 4.3, 4.5, 4.7, or a range consisting of any two of these values.

[0046] In some embodiments, 1≤S2 / S1≤1.3, or 2.2≤S2 / S1≤5. When S2 / S1 is within the above range, there is a large difference in the content of the orthorhombic phase and the monoclinic phase in the lithium manganese oxide, which can synergistically form a solid solution, promote the release of Li ions from the lithium manganese oxide, and thus further improve the charge capacity of the lithium manganese oxide.

[0047] In some embodiments, the Raman spectrum of the positive electrode material is at 270 cm -1 Up to 279cm -1 There is a characteristic peak 3 in the Raman spectrum of the positive electrode material. The presence of characteristic peak 3 indicates that the monoclinic phase in the lithium manganese oxide has a high crystalline order, which is conducive to the release of lithium ions during charging, thereby improving the charging capacity of the electrochemical device.

[0048] In some embodiments, the half-peak width of characteristic peak 3 is H3, which satisfies: H3≤35cm -1 In some embodiments, H3 is 18 cm -1 、19cm -1 , 20cm -1 , 21cm -1 , 22cm -1 , 23cm -1 , 24cm -1 , 25cm -1 , 26cm -1 , 28cm -1 、29cm -1 , 30cm -1 、31cm -1 、32cm -1 、33cm -1 、34cm -1 、35cm -1or a range consisting of any two of these values. The half-maximum width H3 of characteristic peak 3 within this range indicates, on the one hand, a relatively complete degree of crystallization, which can provide a higher lithium removal capacity; on the other hand, the particle size of individual crystals is small, and the solid-phase diffusion path of lithium ions in the material is short, which can effectively improve the kinetics of lithium insertion and extraction in the positive electrode material.

[0049] In some embodiments, the positive electrode material further comprises an M1 element, and the molar percentage of the M1 element in the positive electrode material is a1, based on the molar amount of the Mn element in the positive electrode material, satisfying the following: 0.1%≤a1≤10%, wherein the M1 element comprises at least one of Al, Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, Gd, Cu, Na, Zn, Fe, Co, Ni, Cr, or Ca. In some embodiments, a1 is 0.1%, 0.5%, 1%, 15%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a range consisting of any two of these values.

[0050] In some embodiments, the positive electrode material further comprises an Al element. Based on the molar amount of the Mn element in the positive electrode material, the molar percentage of the Al element in the positive electrode material is b1, satisfying the following: 0.1% ≤ b1 ≤ 10%. In some embodiments, b1 is 0.1%, 0.5%, 1%, 15%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a range consisting of any two of these values. The content of the element Al will cause the phase ratio to change. Too high or too low a content will lead to an increase in the intermediate phase of the material, which in turn increases the grain boundary barriers and reduces the capacity.

[0051] In some embodiments, the molar ratio of Li to Mn in the positive electrode material is c1, satisfying the following: 0.9 ≤ c1 ≤ 1.2. In some embodiments, c1 is 0.91, 0.93, 0.95, 0.97, 0.99, 1.01, 1.03, 1.05, 1.07, 1.09, 1.11, 1.13, 1.15, 1.17, 1.19, or a range consisting of any two of these values. Within the above range, the Li / Mn molar ratio can stably generate orthorhombic and monoclinic mixed phases, thereby improving the energy density of the electrochemical device.

[0052] In some embodiments, the lithium manganese oxide has a lamellar structure, which facilitates the release of Li ions from the lithium manganese oxide, thereby increasing the charge capacity of the lithium manganese oxide.

[0053] In some embodiments, the lithium manganese oxide includes Li x Mn y M1 z O2, wherein 0.9≤x≤1.2, 0.9≤y≤1, 0≤z≤0.1, and M1 comprises at least one of Al, Nb, Mg, Ti, W, Ga, Zr, W, Y, V, Sr, Mo, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, Gd, Cu, Na, Zn, Fe, Co, Ni, Cr, or Ca. In some embodiments, 0.9≤x≤1.2, 0.9≤y≤1, and 0.001≤z≤0.1.

[0054] In some embodiments, the positive electrode material further includes a coating layer located on the surface of the positive electrode material, the coating layer including an M2 element, and the molar percentage of the M2 element in the coating layer is 0.05% to 2% based on the molar amount of the Mn element in the coating layer, wherein the M2 element includes at least one of S, C, B, or F. In some embodiments, the molar percentage of the M2 element is 0.05%, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1%, 1.3%, 1.5%, 1.7%, 1.9%, 2%, or a range consisting of any two of these values. The coating layer on the surface of the positive electrode material can further inhibit the dissolution of Mn, thereby improving the cycling and storage performance of the electrochemical device.

[0055] In some embodiments, the positive electrode material also includes an Al element, and the positive electrode material includes a matrix and a coating layer. Based on the molar amount of the Mn element in the matrix, the molar percentage of the Al element in the matrix is ​​d1, and based on the molar amount of the Mn element in the coating layer, the molar percentage of the Al element in the coating layer is d2, satisfying: d2 / d1≥1.3.

[0056] In some embodiments, the residual lithium content of the positive electrode material is less than or equal to 0.05% based on the mass of the positive electrode material. In some embodiments, the residual lithium content of the positive electrode material is 0.0005%, 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, or a range consisting of any two of these values.

[0057] In some embodiments, the pH value of the cathode material is 11 to 12, such as 11.3, 11.5, 11.7, or 11.9.

[0058] In a second aspect, the present application provides a method for preparing the positive electrode material of the first aspect, comprising: S1: mixing a manganese-containing oxide, a lithium source and an optional M1 element source to obtain a first mixture; subjecting the obtained first mixture to a first heat treatment under a first atmosphere condition and a first temperature condition to obtain a first lithium manganese oxide; wherein the manganese-containing oxide and the lithium source are mixed according to a lithium-manganese molar ratio Li / Mn in the range of 0.9-1.2; and the first atmosphere condition is an inert atmosphere.

[0059] In some embodiments, the inert atmosphere includes at least one of nitrogen, argon, or helium.

[0060] In some embodiments, the first temperature is from 880°C to 1100°C.

[0061] In some embodiments, the first heat treatment time is 5 hours to 20 hours.

[0062] In some embodiments, the manganese-containing oxide comprises Mn 3 O 4 .

[0063] In some embodiments, the M1 element includes at least one of Al, Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, Gd, Cu, Na, Zn, Fe, Co, Ni, Cr, or Ca.

[0064] In some embodiments, the M1 element source includes at least one of CrO2, Al2O3, MgO, TiO2, or Y2O3.

[0065] In some embodiments, the manganese-containing oxide and the M1 element source are mixed such that a molar ratio of the M1 element to the Mn element is in the range of 0.001-0.1.

[0066] In some embodiments, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium acetate, lithium nitrate, or lithium sulfate.

[0067] In some embodiments, step S1 is followed by step S2: mixing the first lithium manganese oxide synthesized in S1 with an M2 element source to obtain a second mixture, and subjecting the obtained second mixture to a second heat treatment under second atmospheric conditions and second temperature conditions to obtain a second lithium manganese oxide having a coating layer on the surface.

[0068] In some embodiments, the second atmosphere condition is an inert atmosphere. In some embodiments, the inert atmosphere comprises at least one of nitrogen, argon, or helium.

[0069] In some embodiments, the second heat treatment time is 2 hours to 5 hours. In some embodiments, the second temperature is 200°C to 600°C.

[0070] In some embodiments, the M2 element includes at least one of S, C, B, or F.

[0071] In a third aspect, the present application provides an electrochemical device comprising a positive electrode, wherein the positive electrode comprises a positive electrode active material layer, wherein the positive electrode active material layer comprises the positive electrode material of the first aspect or the positive electrode material prepared according to the preparation method of the second aspect.

[0072] In some embodiments, the positive electrode active material layer further includes a conductive agent and a binder. In some embodiments, the binder includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber or acrylic (ester) styrene-butadiene rubber, etc. 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 is selected from graphite, carbon black, acetylene black, Ketjen black, carbon nanotubes, carbon fibers, graphene or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0073] In some embodiments, the positive electrode further includes a positive electrode current collector, which can be a metal foil or a composite current collector. For example, aluminum foil can be used. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer substrate.

[0074] The electrochemical device of the present application further includes a negative electrode, which includes a negative electrode active material layer and a negative electrode current collector.

[0075] In some embodiments, the negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder. In some embodiments, the negative electrode active material may include a material that reversibly intercalates and deintercalates lithium ions, lithium metal, a lithium metal alloy, or a transition metal oxide. In some embodiments, the negative electrode active material includes at least one of a carbon material or a silicon material, the carbon material includes at least one of graphite and hard carbon, and the silicon material includes at least one of silicon, a silicon oxide, a silicon carbon compound, or a silicon alloy. In some embodiments, the binder may include various binder polymers. In some embodiments, the binder includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinyl pyrrolidone, polyvinyl ether, polytetrafluoroethylene, polyhexafluoropropylene, or styrene-butadiene rubber. In some embodiments, the conductive agent may use any conductive material as long as it does not cause chemical changes. In some embodiments, the conductive agent includes at least one of conductive carbon black, acetylene black, carbon nanotubes, Ketjen black, carbon fiber, or graphene.

[0076] In some embodiments, the negative electrode current collector may be copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0077] The electrochemical device of the present application further includes an electrolyte, which includes a lithium salt and a non-aqueous solvent.

[0078] In some embodiments of the present application, the lithium salt is selected from one or more of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate. For example, the lithium salt can be LiPF6.

[0079] The non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof.

[0080] The carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorinated carbonate compound or a combination thereof.

[0081] Examples of the above-mentioned linear carbonate compounds are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), and combinations thereof. Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), and combinations thereof. Examples of fluorocarbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.

[0082] Examples of the carboxylic acid ester compound are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerolactone, mevalonolactone, caprolactone, and combinations thereof.

[0083] Examples of the above-mentioned ether compound are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.

[0084] Examples of the above-mentioned other organic solvents are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate and phosphoric acid esters and combinations thereof.

[0085] In some embodiments, in the electrochemical device, an isolation membrane is provided between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the isolation membrane used in the embodiments of the present application are not particularly limited, and it can be any technology disclosed in the prior art. In some embodiments, the isolation membrane includes a polymer or inorganic substance formed from a material that is stable to the electrolyte of the present application. For example, the isolation membrane may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer includes at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film can be selected. A surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic substance. The inorganic layer includes inorganic particles and a binder, wherein the inorganic particles include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate. The binder includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene. The polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, an acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly (vinylidene fluoride and hexafluoropropylene).

[0086] In some embodiments, the electrochemical device of the present application includes, but is not limited to, all types of primary or secondary batteries. In some embodiments, the electrochemical device is a lithium secondary battery. In some embodiments, the lithium secondary battery includes, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0087] In a fourth aspect, the electrical device of the present application may be any device using the electrochemical device of the third aspect of the present application.

[0088] In some embodiments, the electrical devices include, but are not limited to: laptop computers, pen-type computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries or lithium-ion capacitors, etc.

[0089] Examples and Comparative Examples

[0090] 1. Preparation of positive electrode materials

[0091] Comparative Example 1

[0092] Li2CO3 and MnO2 were weighed in a Li:Mn molar ratio of 0.56:1, and Al2O3 was added in an Al:Mn molar ratio of 0.03. The mixture was mixed in a high-speed mixer at a speed of 300 r / min for 20 min to obtain a mixture. The mixture was placed in an air kiln, heated to 790°C at a speed of 5°C / min, maintained for 24 h, taken out after natural cooling, and passed through a 300-mesh sieve to obtain spinel lithium manganate.

[0093] Comparative Example 2

[0094] Traditional method: Mn2O3 and Na2CO3 are mixed evenly according to a Na:Mn molar ratio of 1.05:1, and then heated to 800℃ in a N2 atmosphere at a heating rate of 5℃ / min and kept constant at this temperature for 24h to obtain NaMnO2; a 5mol / L LiBr ethanol solution is added according to a LiBr:NaMnO2 molar ratio of 10:1, and the mixture is exchanged at 180℃ for 8h in an air atmosphere. After completion, the mixture is washed with ethanol and the powder is dried in a 120℃ oven for 5h to obtain lithium manganese oxide by the traditional method.

[0095] Example 1 to Example 19

[0096] Step 1: Place Mn(OOH) in a crucible, heat it to 500°C at a heating rate of 5°C / min in an air atmosphere, and maintain the temperature for 4 hours to obtain anhydrous Mn3O4.

[0097] Step 2: Weigh anhydrous Mn3O4 and LiOH according to the molar ratio of Li / Mn (see Table 1 for the specific ratio), add additives containing M1 elements (see Table 1 for the type and amount of additives), and mix them using a mechanical ball mill for 8 hours to obtain a mixture. 3Nitrogen was introduced at a rate of 5°C / min, and the temperature was raised to the sintering temperature at a constant temperature for a period of time (specific sintering temperature and time are shown in Table 1), and then naturally cooled to room temperature to obtain a lamellar lithium manganese oxide LiMnO2 positive electrode material.

[0098] Table 1

[0099]

[0100] Example 20 to Example 26

[0101] The difference between Examples 20 to 22 and Example 1 is that a modified layer is further coated on the surface of the material in Example 1. The specific steps are as follows: the lithium manganese oxide of Example 1 and nano-NH4F (the content of NH4F, the molar ratio of F to Mn is 0.001, 0.03, and 0.1, respectively) are mixed in a high-speed mixer for 0.5 h, and then the temperature is increased to 450°C at a rate of 5°C / min under a nitrogen atmosphere, and the temperature is kept constant for 2 h.

[0102] The difference between Example 23 and Example 21 is that nano-NH4F is replaced with H3BO3, and after mixing in a high-speed mixer for 0.5 h, the temperature is raised to 280°C at a rate of 5°C / min under a nitrogen atmosphere and kept at this temperature for 2 h.

[0103] The difference between Examples 24 to 26 and Example 20 is that nano-NH4F is replaced with Al2O3 (the content of Al2O3 is 0.03, 0.001, and 0.1, respectively, in terms of the molar ratio of Al to Mn) and mixed in a high-speed mixer for 0.5 h. Then, under a nitrogen atmosphere, the temperature is raised to 600°C at a rate of 5°C / min and kept at this temperature for 2 h.

[0104] 2. Preparation of lithium-ion button batteries

[0105] The above-mentioned positive electrode material, conductive carbon black (Super-P), and binder polyvinylidene fluoride (PVDF) were mixed thoroughly in an N-methylpyrrolidone (NMP) solvent system at a weight ratio of 90:5:5, and then coated on aluminum foil to control the coating mass to 10 mg / cm 2 Up to 30mg / cm 2 After drying at 105℃, cold pressing and punching, the positive electrode sheet is obtained.

[0106] The positive electrode sheet, separator, and metal lithium sheet were placed in the button battery steel shell in order, and an appropriate amount of electrolyte (1MLiPF6, EC:EMC:DEC volume ratio of 1:1:1) was dripped into it. After sealing, the button battery was obtained.

[0107] Test Method

[0108] 1. Raman test

[0109] The cathode material powder was placed on the stage and characterized using the Horibr HR Revolution device. The specific parameters are as follows: Resolution: ~2cm -1 ; Excitation wavelength: 532nm.

[0110] 2. Element content test

[0111] Content of Mn, M1 and Li elements: Use a mixed solvent to dissolve the positive electrode material (for example, 0.4 g of positive electrode material uses a mixed solvent of 10 ml (nitric acid and hydrochloric acid mixed in a ratio of 1:1) aqua regia and 2 ml HF), dilute to 100 mL, and then use ICP-OES (inductively coupled plasma-emission spectrometer, equipment model: ICAP6300) to test and determine the content of Mn, M1 and Li elements in the positive electrode material.

[0112] Content of M2 and Mn elements in the coating layer: XPS test was used to obtain the content of M2 and Mn elements in the coating layer on the surface of the positive electrode material.

[0113] Al and Mn element content in the coating layer and matrix: TEM-EDS test was used to obtain the Al and Mn element content in the positive electrode material matrix and coating layer.

[0114] 3. Test of residual lithium content in positive electrode materials

[0115] The lithium carbonate and lithium hydroxide in the cathode material were titrated using a standard hydrochloric acid solution using an acid-base titration method. Instrument model: 905 Titrando potentiometric titrator; Reagent: 0.05 mol / L HCl solution.

[0116] 4. Gram capacity and first coulombic efficiency test

[0117] In a 45°C environment, the lithium-ion button battery is charged at a constant current of 0.1C to 4.3V, then charged at a constant voltage of 4.3V to a current of 0.05C, and the initial charge capacity of the lithium-ion button battery is recorded. The battery is then discharged at a constant current of 0.1C to 3.0V, and the initial discharge capacity of the lithium-ion button battery is recorded.

[0118] Charge gram capacity = first charge capacity / positive electrode material mass.

[0119] First efficiency = first discharge capacity / first charge capacity × 100%.

[0120] 5. Mn element dissolution test

[0121] At 25°C, lithium-ion button cells were charged to 4V at a constant current of 0.1C. The positive electrode was then disassembled and immersed in an electrolyte (1M LiPF6, EC:EMC:DEC ratio of 1:1:1 by volume) at 60°C for 7 days. The Mn content in the electrolyte was measured using ICP. The Mn release was calculated as the Mn content in the electrolyte divided by the mass of the positive electrode material.

[0122] Test results

[0123]

[0124] From the data of Example 1 and Comparative Examples 1 to 2, it can be seen that when Characteristic Peak 1 and Characteristic Peak 2 are simultaneously present in the positive electrode material, it has a high charge capacity per gram. This is mainly because the orthorhombic and monoclinic phases in the lithium manganese oxide are rich in lithium ions. At the same time, the solid solution formed by the coexistence of the two phases contains oxygen vacancies, which can promote the release of lithium ions, thereby significantly improving the charge capacity per gram of the lithium manganese oxide. At the same time, the presence of the orthorhombic and monoclinic composite phase structure in the lithium manganese oxide can stabilize the Mn structure and reduce octahedral lattice distortion, thereby improving the stability of the crystal structure of the lithium manganese oxide in the highly delithiated state, thereby inhibiting the dissolution of the Mn element and improving its service life in high-temperature applications.

[0125] Table 3

[0126]

[0127]

[0128] Note: The only difference between Examples 6 to 8 and Example 1 is the Li / Mn molar ratio. The rest are the same as Example 1.

[0129] The data from Examples 1 and 6 to 8 show that the Li / Mn molar ratio affects the capacity of the positive electrode material. A Li / Mn molar ratio in the range of 0.9-1.2 can stably generate an orthorhombic and monoclinic mixed phase, thereby increasing the energy density of the electrochemical device.

[0130] Table 4

[0131]

[0132] Note: The only difference between Examples 9 to 12 and Example 1 is the Al content. The rest are the same as Example 1.

[0133] From the data of Examples 1 to 12, it can be seen that when 1≤S2 / S1≤1.3 or 2.2≤S2 / S1≤5 is satisfied, the lithium-ion button cell can have a higher charge capacity. The possible reason is that there is a large difference in the content of the orthorhombic phase and the monoclinic phase in the lithium manganese oxide, which can synergistically form a solid solution and promote the release of Li ions from the lithium manganese oxide, thereby further improving the charge capacity of the lithium manganese oxide.

[0134]

[0135]

[0136] It can be seen from the data of Example 1 and Examples 20 to 26 that the Mn dissolution can be significantly improved after coating with a coating layer.

[0137] Although some exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. On the contrary, those skilled in the art will recognize that some modifications and changes may be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims.

Claims

1. A positive electrode material comprising lithium manganese oxide, wherein: The Raman spectrum of the positive electrode material is at 401 cm -1 Up to 410cm -1 There is a characteristic peak 1 at 598cm -1 Up to 611cm -1 There is a characteristic peak 2 in the range, the molar ratio of Li element to Mn element is (0.92-1.05):1, the peak area of ​​the characteristic peak 1 is S1, the peak area of ​​the characteristic peak 2 is S2, and the following is satisfied: 2.2≤S2 / S1≤5.

2. The positive electrode material according to claim 1, wherein The half-peak width of the characteristic peak 1 is H1, and the half-peak width of the characteristic peak 2 is H2, satisfying: H1≤25cm -1 、H2≤30cm -1 .

3. The positive electrode material according to claim 1, wherein The Raman spectrum of the positive electrode material is at 270 cm -1 Up to 279cm -1 There is a characteristic peak 3 in the range.

4. The positive electrode material according to claim 3, wherein The half-peak width of the characteristic peak 3 is H3, which satisfies: H3≤35cm -1 .

5. The positive electrode material according to claim 1, wherein The positive electrode material satisfies at least one of the following conditions: (a) The positive electrode material further includes an M1 element, and the molar percentage of the M1 element in the positive electrode material is a1 based on the molar amount of the Mn element in the positive electrode material, satisfying: 0.1%≤a1≤10%, wherein the M1 element includes at least one of Al, Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, Gd, Cu, Na, Zn, Fe, Co, Ni, Cr or Ca; (b) the positive electrode material further includes an Al element, and based on the molar amount of the Mn element in the positive electrode material, the molar percentage of the Al element in the positive electrode material is b1, satisfying: 0.1%≤b1≤10%; (d) the lithium manganese oxide has a lamellar structure; (e) The lithium manganese oxide includes Li x Mn y M1 z O2, wherein 0.9≤x≤1.2, 0.9≤y≤1, 0≤z≤0.1, and M1 includes at least one of Al, Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, Gd, Cu, Na, Zn, Fe, Co, Ni, Cr, or Ca.

6. The positive electrode material according to claim 1, wherein The positive electrode material also includes a coating layer located on the surface of the positive electrode material, the coating layer includes an M2 element, and based on the molar amount of the Mn element in the coating layer, the molar percentage of the M2 element in the coating layer is 0.05% to 2%, wherein the M2 element includes at least one of S, C, B or F.

7. The positive electrode material according to claim 1, wherein The positive electrode material also includes an Al element. The positive electrode material includes a matrix and a coating layer. Based on the molar amount of the Mn element in the matrix, the molar percentage of the Al element in the matrix is ​​d1. Based on the molar amount of the Mn element in the coating layer, the molar percentage of the Al element in the coating layer is d2, satisfying: d2 / d1≥1.

3.

8. The positive electrode material according to claim 1, wherein Based on the mass of the positive electrode material, the residual lithium content of the positive electrode material is less than or equal to 0.05%; And / or the pH value of the positive electrode material is 11 to 12.

9. A method for preparing the positive electrode material according to any one of claims 1 to 8, comprising: S1: mixing the manganese-containing oxide and the lithium source to obtain a first mixture or mixing the manganese-containing oxide, the lithium source and the M1 element source to obtain the first mixture; subjecting the first mixture to a first heat treatment under first atmospheric conditions and first temperature conditions to obtain a first lithium manganese oxide; The manganese-containing oxide and the lithium source are mixed in a lithium-manganese molar ratio Li / Mn in the range of 0.92-1.05; and the first atmosphere condition is an inert atmosphere.

10. The method for preparing a cathode material according to claim 9, wherein: The preparation method satisfies at least one of the following conditions: (1) The inert atmosphere comprises at least one of nitrogen, argon or helium; (2) the first temperature is 880° C.-1100° C.; (3) The first heat treatment time is 5 hours to 20 hours; (4) the manganese-containing oxide comprises Mn3O4; (5) The M1 element includes at least one of Al, Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, Gd, Cu, Na, Zn, Fe, Co, Ni, Cr or Ca; (6) The M1 element source includes at least one of CrO2, Al2O3, MgO, TiO2 or Y2O3; (7) the manganese-containing oxide and the M1 element source are mixed so that the molar ratio of the M1 element to the Mn element is in the range of 0.001-0.1; (8) The lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium acetate, lithium nitrate or lithium sulfate; (9) Step S1 further includes step S2: mixing the first lithium manganese oxide with an M2 element source to obtain a second mixture, and subjecting the second mixture to a second heat treatment under a second atmosphere and a second temperature to obtain a second lithium manganese oxide having a coating layer on the surface.

11. The method for preparing a positive electrode material according to claim 10, wherein: The preparation method satisfies at least one of the following conditions: (1) The second atmosphere condition is an inert atmosphere; (2) The second heat treatment time is 2 hours to 5 hours; (3) The second temperature is 200° C. to 600° C.; (4) The M2 element includes at least one of S, C, B or F. 12 . An electrochemical device comprising a positive electrode, wherein the positive electrode comprises the positive electrode material according to claim 1 or the positive electrode material prepared by the method for preparing the positive electrode material according to claim 9 .

13. An electrical device comprising the electrochemical device according to claim 12.

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