A positive electrode material and a battery and an electrical device containing the same

Abstract

The present application relates to a multi-cation positive electrode material, the general formula of which is Li a L x Ni b Co c Mn d M (1‑b‑c‑d) O e N f or mLi2MnO3·(1‑m)Li a L x Ni b Co c Mn d M (1‑b‑c‑d) O e N f , wherein L ion is a cation having a radius larger than that of Li ion, M includes at least one of Mg, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, N includes at least one of F, S, and P, 0<a<1, 0≤b<1, 0≤c<1, 0≤d<1, 0<b+c+d≤1, 0<e≤2, 0≤f<2, 0<m<1, 0<x≤0.8, a+x=1, e+f=2, and the following relationship is satisfied: 2.5×10 ‑6 ≤x / v≤2.5×10 ‑3 , wherein v is the gram capacity of the multi-cation positive electrode material. The present application also relates to a lithium ion battery comprising the positive electrode material and an electrical device comprising the lithium ion battery.

Description

Technical Field

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

[0002] Lithium-ion batteries are now widely used in pure electric vehicles, hybrid electric vehicles, and smart grids. With the widespread adoption of lithium-ion batteries, the industry is also placing higher demands on their energy density, rate capability, and safety. As demand for lithium-ion energy density increases, layered cathode materials have gradually evolved from the earliest low-nickel materials to today's high-nickel and lithium-rich manganese-based materials with high gram capacity. However, due to factors such as the mixing of lithium and nickel, these high-nickel and lithium-rich manganese-based materials have poor structural stability, which seriously affects the cycling performance of the battery cells.

[0003] Therefore, there is still a need in the art to develop a new active material for the positive electrode, which has improved stability to suppress lithium nickel mixing, and has high gram capacity and good cycle performance. Summary of the Invention

[0004] The present application is made in view of the above-mentioned issues, and its purpose is to provide a positive electrode active material that can have improved stability at a high gram capacity and effectively inhibit lithium-nickel mixing, thereby solving the technical problem in the prior art that the poor stability of the positive electrode material adversely affects the cycle performance of the battery cell.

[0005] In order to achieve the above-mentioned object, the first aspect of the present application provides a multi-cation positive electrode material, wherein the general formula of the positive electrode material is Li a L x Ni b Co c Mn d M (1-b-c-d) O e N f or mLi2MnO3·(1-m)Li a L x Ni b Co c Mn d M (1-b-c-d) O e N f , wherein the L ion is a cation having a radius larger than that of the Li ion, M includes at least one of Mg, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, N includes at least one of F, S, and P, 0<a<1, 0≤b<1, 0≤c<1, 0≤d<1, 0<b+c+d≤1, 0<e≤2, 0≤f<2, 0<m<1, 0<x≤0.8, a+x=1, e+f=2,

[0006] And the following relationship is satisfied:

[0007] 2.5×10 -6 ≤x / v≤2.5×10 -3 , where v is the gram capacity of the multi-cation positive electrode material.

[0008] By replacing some of the lithium in the layered cathode material with cations with larger ionic radii, the layered structure is supported, lithium-nickel mixing is suppressed, and material stability is improved. Furthermore, by adjusting the ratio of the molar amount of the doped cations with larger ionic radii to the gram capacity of the cathode material, the cycle life of lithium-ion batteries containing this cathode material can be effectively adjusted.

[0009] In any embodiment, 0.001<x≤0.5, preferably 0.003<x≤0.05. In any embodiment, in the multi-cation positive electrode material, x and v satisfy the following formula: 2.5×10 -5 ≤x / v≤2.5×10 -4 By further adjusting the x / v ratio, the stability of the cathode material can be further improved.

[0010] In any embodiment, the gram capacity v of the multi-cation positive electrode material satisfies 120 mAh / g≤v≤300 mAh / g.

[0011] In any embodiment, the L ion comprises at least one of an alkali metal element, alkaline earth metal element, transition metal element, or other main group metal element, excluding lithium. In a further embodiment, the alkali metal element comprises at least one of Na, K, Rb, and Cs; the alkaline earth metal element comprises at least one of Mg, Ca, and Sr; the transition metal element comprises Y; and the other main group metal element comprises Bi. In a further embodiment, the L ion comprises at least two of Na, K, Rb, and Cs; optionally, the molar ratio of each of the at least two elements is greater than 0.5%, based on the molar amount of the Li ion.

[0012] In any embodiment, in the multi-cation positive electrode material, a satisfies 0.5≤a<1; optionally, 0.8≤a<1.

[0013] In any embodiment, in the multi-cationic cathode material, 0.05≤b≤0.98, and 0.05≤c≤0.85.

[0014] A second aspect of the present application provides a lithium-ion battery, comprising a positive electrode, wherein the positive electrode comprises the positive electrode material according to the first aspect of the present application.

[0015] In any embodiment, the lithium ion battery comprises a negative electrode, the negative electrode active material of the negative electrode comprising at least one of graphite, hard carbon, and soft carbon.

[0016] A third aspect of the present application provides an electrical device comprising the lithium-ion battery according to the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] To more clearly illustrate the technical solution of this application, the following briefly introduces the drawings required for use in the embodiments of this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0018] Figure 1 is a schematic diagram of a lithium-ion secondary battery in one embodiment of the present application.

[0019] Figure 2 yes Figure 1 An exploded view of a lithium-ion secondary battery in one embodiment of the present application is shown.

[0020] Figure 3 is a schematic diagram of a battery pack in one embodiment of the present application.

[0021] Figure 4 yes Figure 3 An exploded view of a battery pack in one embodiment of the present application is shown.

[0022] Figure 5 Schematic diagram of a device in which a battery pack is used as a power source in one embodiment of the present application.

[0023] Description of Reference Numerals

[0024] 1 battery pack

[0025] 2 Upper box

[0026] 3 lower box

[0027] 4 battery modules

[0028] 5 Lithium-ion secondary batteries

[0029] 51 housing

[0030] 52 electrode assembly

[0031] 53 cover DETAILED DESCRIPTION

[0032] For the sake of clarity, this application specifically discloses certain numerical ranges. 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.

[0033] As demand for lithium-ion energy density increases, layered cathode materials have evolved from the earliest low-nickel materials to today's high-nickel and lithium-rich manganese-based materials with high gram capacity. However, due to factors such as lithium-nickel intermixing, these high-nickel and lithium-rich manganese-based materials have poor structural stability, which seriously affects the cycling performance of battery cells. For example, during charging, the low-valent nickel in the transition metal layer migrates to occupy lithium ion vacancies, causing the structure of the high-gram capacity cathode material to be destroyed and its stability and safety performance to deteriorate.

[0034] The inventors have discovered that by doping a certain amount of cations with a radius larger than the Li ion radius into the positive electrode material for lithium-ion batteries to replace some of the lithium ions, the doped cations, whose ionic radius is larger than that of lithium, can support the layered structure, thereby suppressing the mixing of lithium and nickel and improving the material stability. However, the doping amount of the above cations must meet a certain relationship with the gram capacity of the positive electrode material to achieve a satisfactory stabilization effect of the doped element.

[0035] Specifically, the first aspect of the present application provides a multi-cation positive electrode material, the general formula of the positive electrode material is Li a L x Ni b Co c Mn d M (1-b-c-d) O e N f or mLi2MnO3·(1-m)Li a L x Ni b Co c Mn d M (1-b-c-d) O e N f , wherein the L ion is a cation having a radius larger than that of the Li ion, M includes at least one of Mg, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, N includes at least one of F, S, and P, 0<a<1, 0≤b<1, 0≤c<1, 0≤d<1, 0<b+c+d≤1, 0<e≤2, 0≤f<2, 0<m<1, 0<x≤0.8, a+x=1, e+f=2,

[0036] And the following relationship is satisfied:

[0037] 2.5×10 -6 ≤x / v≤2.5×10 -3 , where v is the gram capacity of the multi-cation positive electrode material.

[0038] Without being bound by any specific theory, the inventors believe that by partially replacing the lithium ions in the positive electrode material with cations L whose ionic radius is larger than that of Li, the larger ionic radius of these elements hinders the occupation of lithium ion vacancies by nickel ions to a certain extent, preventing the layered structure of the positive electrode material from being transformed into a spinel structure, thereby helping to improve the stability of the layered structure. In addition, the larger ionic radius of these cations also increases the ion diffusion channel, which helps to improve the rate performance of the material. However, the doping amount of these elements needs to be controlled within a certain range, especially relative to the gram capacity of the positive electrode material. Too little doping amount is insufficient to achieve a supporting effect, while too much doping amount will hinder ion transport and reduce the gram capacity. For example, for a material that meets the requirements of 2.5×10 -6 ≤x / v≤2.5×10 -3 On the one hand, the sodium ions or potassium ions in the new cathode material, which are larger than the lithium radius, can play a supporting role at the lithium site, enhance the mixing energy barrier, prevent the aggravation of the Li / Ni mixing in the layered cathode, improve the stability of the layered structure and thus improve the cycle performance. The multi-cationic cathode material can also be embedded in the negative electrode material, where the ions with larger ionic radius play a supporting role in the graphite, thereby reducing the expansion / contraction of the graphite caused by the ions with smaller ionic radius during the embedding / extraction process, which is beneficial to improve the stability of the SEI film and reduce the consumption of active lithium. When x / v<2.5×10 -6 When x / v>2.5×10 -3 When the electrolyte is charged, a large number of doping ions with a larger radius will hinder the transmission of lithium ions, aggravating the side reaction between the electrolyte and the interface, increasing the impedance, and reducing the gram capacity of the material. It is also difficult to improve the life. The gram capacity of the positive electrode material can be measured by the following method: make a button cell, charge it at a constant voltage after a constant current of 0.1C, and then discharge it at 0.1C. The capacity is measured and divided by the mass of the active material to obtain the gram capacity. In the present invention, unless otherwise specified, the gram capacity of the positive electrode material refers to the gram capacity measured at 25°C.

[0039] In some embodiments, in the polycationic cathode material, x satisfies 0.001 < x ≤ 0.5, and optionally 0.003 < x ≤ 0.05. x represents the doping ratio of cations L, whose ionic radius is larger than that of Li, in the Li ion. Adjusting this ratio can further improve the stabilization effect of cations L on the cathode material.

[0040] In some embodiments, in the multi-cation positive electrode material, x and v satisfy the following formula: 2.5×10 -5 ≤x / v≤2.5×10 -4 As described above, the ratio of the doping amount of the cation L to the gram capacity of the positive electrode material must be controlled within a certain range and can be further adjusted to further enhance the stabilization of the positive electrode material. Within this further selected ratio range, the cycle life of a lithium-ion battery containing the positive electrode material is further significantly improved.

[0041] In some embodiments, the gram capacity v of the polycationic cathode material satisfies 120 mAh / g ≤ v ≤ 300 mAh / g. If the gram capacity of the polycationic cathode material is too low, a high energy density of the battery cannot be achieved; if the gram capacity is too high, the stability of the cathode material decreases, resulting in an insufficient cycle life of the battery.

[0042] In some embodiments, in the polycationic cathode material, the L ions comprise at least one of an alkali metal element, an alkaline earth metal element, a transition metal element, or other main group metal element, excluding lithium. Furthermore, the alkali metal element comprises at least one of Na, K, Rb, and Cs; the alkaline earth metal element comprises at least one of Mg, Ca, and Sr; the transition metal element comprises Y; and the other main group metal element comprises Bi. In some embodiments, the L ions are different from other ions already present in the polycationic cathode material, such as Co, Ni, Mn, and possible M ions. In some embodiments, the L ions comprise at least two, optionally at least three, and further optionally all four of Na, K, Rb, and Cs. Optionally, the molar ratio of each of the at least two, three, or four elements is greater than 0.5%, based on the molar amount of Li ions. In some embodiments, the molar ratio of at least two of Na, K, Rb, and Cs is greater than 0.005, for example, between 0.01 and 0.25, based on the molar amount of Li ions. Specifically, the doping molar ratio of each element in the present application may include the following technical solutions: Na and K are not 0, or are greater than 0.005; Na and Rb are not 0, or are greater than 0.005; Na and Cs are not 0, or are greater than 0.005; K and Rb are not 0, or are greater than 0.005; K and Cs are not 0, or are greater than 0.005; Rb and Cs are not 0, or are greater than 0.005; Na, K and Rb are not 0, or are greater than 0.005; Na, Rb and Cs are not 0, or are greater than 0.005; Na, K and Cs are not 0, or are greater than 0.005; K, Rb and Cs are not 0, or are greater than 0.005; Na, K, Rb and Cs are not 0, or are greater than 0.005, all of which are based on the molar amount of Li ions. The doping molar ratio of each element in Na, K, Rb, and Cs can be the same or different. For example, the multi-cation positive electrode material of the present application can be Li 0.96 Na 0.01 K 0.01 Cs 0.01 Rb 0.01 Ni 0.8 Co 0.1 Mn 0.1 O2、Li 0.94 Na 0.02 K 0.02 Cs 0.01 Rb 0.01 Ni 0.8 Co 0.1 Mn 0.1 O2、Li 0.96 Na 0.02 K 0.02 Ni0.8 Co 0.1 Mn 0.1 O2 or Li 0.97 K 0.01 Cs 0.01 Rb 0.01 Ni 0.8 Co 0.1 Mn 0.1 The molar ratio of each element in Na, K, Rb, and Cs can be adjusted by adjusting the type and amount of each element. For example, during the preparation of the positive electrode material, the specific doping elements and the relative molar amounts of each element can be selected. The specific composition of the final positive electrode material can be determined by methods such as ICP.

[0043] In some embodiments, in the multi-cation positive electrode material, a satisfies 0.5≤a<1; optionally, 0.8≤a<1. a characterizes the molar ratio of lithium ions in the positive electrode material. Since a is less than 1, x is not 0, that is, at least part of the lithium ions in the positive electrode material are replaced by at least one L ion, such as Na, K, Rb and Cs. Among the alkali metal ions in the positive electrode material, the molar ratio of lithium ions is advantageously adjusted to 50% or more, more advantageously 80% or more. If the lithium ion content is too low, the lithium ion transport is hindered, resulting in a decrease in capacity and kinetics.

[0044] In some embodiments, in the polycationic cathode material, 0.05 ≤ b ≤ 0.98, and 0.05 ≤ c ≤ 0.85. The values ​​of b and c can be selected within a wide range depending on the desired material and are not particularly limited. Typically, for high-gram capacity cathode materials, the Ni content is relatively high, for example, b can be greater than 0.5, greater than 0.6, or even as high as 0.98. The value of c can typically be between 0.05 and 0.3, or between 0.1 and 0.2.

[0045] M ions are cations used to partially replace Ni, Co, and Mn, and include at least one of Mg, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La. Optionally, M ions are selected from Mg, Zr, Al, B, Ta, Mo, W, Nb, Sb, or La ions. The relative molar ratio of M ions, based on the total molar amount of Ni, Co, and Mn, may be 0-20%, and optionally 0-10%. N ions are ions used to dope and replace a portion of O ions, and include at least one of F, S, and P; optionally, they are selected from F, S, or P. The doping amount of N ions, based on the molar amount of O ions, may be 0-20%, and optionally 0-5%.

[0046] In some embodiments, the polycationic cathode material can be prepared by the following method: first, a conventional precursor is prepared by mixing compounds of lithium, cobalt, nickel, etc., then the precursor is mixed with a compound of the doping element, ground, and calcined. After cooling, the doped polycationic cathode material is obtained. The compound can be a salt of each element, such as a carbonate. The amount of compound containing each element can be determined based on the desired final composition of the cathode material, for example, by the molar ratio of each element in the final composition. The lithium salt is typically added in excess to compensate for losses during the calcination process.

[0047] The second aspect of the present application provides a lithium-ion battery, which includes a positive electrode, wherein the positive electrode comprises the multi-cation positive electrode material according to the first aspect of the present application. Typically, the positive electrode material is coated on a positive electrode current collector to form a positive electrode active material layer. In the preparation of the positive electrode plate, the positive electrode material and the binder, conductive agent, etc. can be dispersed in an organic solvent (such as N-methylpyrrolidone (NMP)) to form a uniform slurry, which is coated on the positive electrode current collector and then dried at a high temperature. The plate obtained after drying can be rolled and cut into a predetermined shape. There is no particular restriction on the choice of binder. As an example, it can be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB). There is no specific restriction on the type of conductive agent, and those skilled in the art can choose according to actual needs. As an example, the conductive agent used in the positive electrode material can be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the weight ratio of the positive electrode active material, conductive agent, and binder contained in the slurry of the positive electrode sheet is 70-90:5-15:5-15, or alternatively 75-85:8-12:8-12.

[0048] In some embodiments, the lithium ion battery comprises a negative electrode, and the negative electrode active material of the negative electrode comprises at least one of graphite, hard carbon, and soft carbon. However, there is no particular limitation on the selection of the negative electrode material, and negative electrode materials conventionally used in lithium ion batteries can be selected.

[0049] A third aspect of the present application provides an electrical device comprising the lithium-ion battery according to the second aspect of the present application.

[0050] The composition and structure of lithium-ion batteries are described in detail below.

[0051] The materials of the components of the lithium-ion battery of the present application can be selected from a wide range. In some embodiments, the battery is specifically a lithium-ion secondary battery. The battery cells of the lithium-ion secondary battery are described in detail below.

[0052] Typically, a lithium-ion secondary battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The separator is placed between the positive and negative electrodes to isolate them. The electrolyte conducts ions between the positive and negative electrodes.

[0053] [Electrolyte]

[0054] The electrolyte conducts ions between the positive and negative electrodes and consists of electrolyte salts and solvents.

[0055] In the present application, the electrolyte salt may be a commonly used electrolyte salt in lithium-ion secondary batteries, such as a lithium salt, including the lithium salts described above as high thermal stability salts, lithium salts as low impedance additives, or lithium salts that inhibit corrosion of aluminum foil. As an example, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP), lithium fluorosulfonate (LiSO3F), difluorobis(oxalato) (NDFOP), Li2F(SO2N)2SO2F, KFSI, CsFSI, Ba(FSI)2, and LiFSO2NSO2CH2CH2CF3.

[0056] The type of solvent is not particularly limited and can be selected according to actual needs. In some embodiments, the solvent is a non-aqueous solvent. Alternatively, the solvent may include one or more of linear carbonate, cyclic carbonate, and carboxylate. In some embodiments, the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), tetrahydrofuran, sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).

[0057] In some embodiments, the electrolyte may optionally include other additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that improve battery low temperature performance. As an example, the additive is selected from at least one of a cyclic carbonate compound containing an unsaturated bond, a halogen-substituted cyclic carbonate compound, a sulfate compound, a sulfite compound, a sultone compound, a disulfonic acid compound, a nitrile compound, an aromatic compound, an isocyanate compound, a phosphazene compound, a cyclic acid anhydride compound, a phosphite compound, a phosphate compound, a borate compound, and a carboxylate compound.

[0058] [Positive electrode]

[0059] The positive electrode sheet 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. The positive electrode active material layer includes a positive electrode active material and a conductive agent.

[0060] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0061] In the lithium-ion secondary battery of the present application, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (e.g., aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (e.g., a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0062] The positive electrode active material layer disposed on the surface of the positive electrode current collector includes a positive electrode active material. The positive electrode active material used in this application may be any conventional positive electrode active material used in secondary batteries. In some embodiments, the positive electrode active material may include one or more selected from lithium transition metal oxides, olivine-structured lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Examples of olivine-structured lithium-containing phosphates include, but are not limited to, lithium iron phosphate, lithium iron phosphate-carbon composites, lithium manganese phosphate, lithium manganese phosphate-carbon composites, lithium iron manganese phosphate, lithium iron manganese phosphate-carbon composites, and their modified compounds. These materials are commercially available. The surface of the positive electrode active material may be coated with carbon. The positive electrode active material may be doped to obtain a doped positive electrode active material. The doping element may include, but is not limited to, at least one selected from Na, K, Rb, and Cs.

[0063] The positive electrode active material layer may optionally include a conductive agent. However, the type of conductive agent is not particularly limited, and those skilled in the art may select one based on actual needs. For example, the conductive agent used in the positive electrode material may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0064] The positive electrode active material layer also includes an aqueous binder. The aqueous binder can be selected from one or more of soluble polysaccharides and their derivatives, and water-soluble or water-dispersible polymers. Examples of aqueous binders include methylcellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts, polyethyleneimine and its salts, polyacrylamide, acrylic acid copolymers, and their derivatives.

[0065] In this application, the positive electrode sheet can be prepared according to methods known in the art. For example, a carbon-coated positive electrode active material, a conductive agent, and an aqueous binder can be dispersed in a solvent (e.g., water) to form a uniform positive electrode slurry; the positive electrode slurry is coated on a positive electrode current collector, and after drying, cold pressing, and other processes, a positive electrode sheet is obtained.

[0066] [Negative electrode]

[0067] The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode material layer includes a negative electrode active material.

[0068] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0069] In the lithium-ion secondary battery of the present application, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material. The composite current collector may be formed by forming a metal material (e.g., copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0070] In the lithium-ion secondary battery of the present application, the negative electrode material layer generally comprises a negative electrode active material and an optional binder, an optional conductive agent, and other optional additives, and is generally formed by coating and drying a negative electrode slurry. The negative electrode slurry coating is generally formed by dispersing the negative electrode active material and the optional conductive agent and binder in a solvent and stirring the mixture uniformly. The solvent may be N-methylpyrrolidone (NMP) or deionized water.

[0071] The specific type of negative electrode active material is not limited. Active materials known in the art for use in negative electrodes of lithium-ion secondary batteries can be used, and those skilled in the art can select according to actual needs. As an example, the negative electrode active material can be selected from one or more of graphite, soft carbon, hard carbon, mesocarbon microbeads, carbon fibers, carbon nanotubes, elemental silicon, silicon oxides, silicon-carbon composites, and lithium titanate.

[0072] As an example, the conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0073] As an example, the binder can be selected from one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0074] Other optional auxiliary agents include, for example, thickeners (such as sodium carboxymethyl cellulose (CMC-Na)).

[0075] [Diaphragm]

[0076] The lithium-ion secondary battery using an electrolyte includes a diaphragm. The diaphragm is arranged between the positive electrode plate and the negative electrode plate to play an isolating role. The diaphragm of the present application is as described above; however, the lithium-ion battery of the present application may also further include a conventional diaphragm. There is no particular restriction on the type of conventional diaphragm, and any well-known porous structure diaphragm with good chemical stability and mechanical stability can be selected. In some embodiments, the material of the conventional diaphragm can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The diaphragm can be a single-layer film or a multi-layer composite film, without particular restriction. When the diaphragm is a multi-layer composite film, the materials of each layer can be the same or different, without particular restriction.

[0077] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0078] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0079] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft package, such as a pouch-type soft package. The soft package can be made of plastic, such as polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0080] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. For example, Figure 1 As an example, a lithium-ion secondary battery 5 having a square structure is shown.

[0081] In some embodiments, reference Figure 2, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the diaphragm can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the lithium-ion secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0082] In some embodiments, lithium-ion secondary batteries can be assembled into a battery module 4. The number of lithium-ion secondary batteries contained in the battery module 4 can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module 4. In the battery module 4, multiple lithium-ion secondary batteries 5 can be arranged in sequence along the length direction of the battery module. Of course, they can also be arranged in any other manner. The multiple lithium-ion secondary batteries 5 can further be fixed by fasteners. Optionally, the battery module 4 can also include a shell having a storage space, and the multiple lithium-ion secondary batteries 5 are accommodated in the storage space.

[0083] In some embodiments, the lithium-ion secondary batteries 5 or battery modules 4 can be assembled into a battery pack 1 , and the number of lithium-ion secondary batteries 5 or battery modules 4 contained in the battery pack 1 can be selected by those skilled in the art based on the application and capacity of the battery pack 1 .

[0084] The lithium-ion secondary battery of the present application may be in the form of a battery cell, a battery module, or a battery pack. In some embodiments, the battery cells may be assembled into a battery module. In some embodiments, the battery cells may be assembled into a battery pack. In some embodiments, the battery modules may also be assembled into a battery pack.

[0085] Figure 3 and Figure 4 The battery pack 1 is used as an example. Figure 3 and Figure 4 The battery pack 1 may include a battery box and a plurality of battery cells disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery cells.

[0086] In addition, the present application also provides a device, which includes a battery pack provided in the present application. The battery pack can be used as a power source for the device, and can also be used as an energy storage unit for the device. The device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc. As the device, a battery pack can be selected according to its usage requirements.

[0087] Figure 5 This is an example device. The device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density of lithium-ion secondary batteries, a battery pack or battery module can be used.

[0088] Example

[0089] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature within the art or the product specifications are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially. Unless otherwise specified, all experimental steps were carried out under normal pressure.

[0090] Example 1

[0091] Doped high nickel cathode material Li 0.96 Na 0.01 K 0.01 Cs 0.01 Rb 0.01 Ni 0.8 Co 0.1 Mn 0.1 Preparation of O2

[0092] First, nickel acetate, cobalt acetate, and manganese acetate are added to deionized water in a stoichiometric ratio and stirred thoroughly. The sodium carbonate solution is quickly poured into the transition metal salt solution and the reaction continues for 9 hours. The mixture is then allowed to age for 4 hours to allow for primary particle growth. The product is then washed three times with deionized water, dried in a blast dryer, and vacuum-dried at 100°C for 12 hours. The dried solid is collected as the precursor.

[0093] The precursor was mixed evenly with lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate and cesium carbonate in a molar ratio of 1:1.05:0.01:0.01:0.01:0.01, and then ground. The excess lithium carbonate was used to compensate for the loss of lithium during high-temperature calcination. The fully ground solid powder was transferred to a crucible and placed in a muffle furnace with programmed temperature for calcination. The calcination procedure was: pre-calcination from room temperature to 500°C for 5h, and then calcined at a high temperature of 800°C for 12h, with a heating rate of 3°C min -1 The resulting material was then collected after cooling to room temperature.

[0094]

Preparation of positive electrode sheet

[0095] The positive electrode material prepared as described above is mixed with polyvinylidene fluoride (PVDF) and a conductive agent (carbon black Super P) in a mass ratio of 90:5:5. N-methyl-pyrrolidone (NMP) is used as a solvent and the amount of solvent added is adjusted to control the viscosity of the slurry to 100-20000mPa.s. The slurry is coated on the surface of the aluminum foil using a coating machine and then transferred to a vacuum drying oven for complete drying. After drying at 85°C, cold pressing is performed, followed by trimming, cutting, and striping, and then drying at 85°C under vacuum conditions for 4 hours, welding the tabs, and making positive electrode sheets. The total coating amount of the positive electrode active material on the obtained sheet is 0.3g / 1540.25mm 2 .

[0096]

Preparation of negative electrode sheet

[0097] The active material graphite, conductive agent Super-P, thickener CMC, and adhesive SBR are added to the solvent deionized water in a mass ratio of 96.5:1.0:1.0:1.5 and mixed evenly to form the anode slurry; the anode slurry is coated on the current collector copper foil and dried at 85°C, and then trimmed, cut into pieces, and divided into strips, and then dried under vacuum conditions at 110°C for 4 hours, and the tabs are welded to form the negative electrode sheet.

[0098] Preparation of electrolyte

[0099] A mixture of ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) was used as a non-aqueous organic solvent, wherein the mass ratio of each component was EC:PC:DEC = 30:30:40, and lithium hexafluorophosphate (LiPF6) was used as the lithium salt to prepare an electrolyte with a concentration of 1M.

[0100]

Isolation film

[0101] A 12 μm polypropylene film was used as the separator.

[0102] Preparation of lithium-ion batteries

[0103] The positive electrode sheet, separator, and negative electrode sheet as described above are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation. The above electrolyte is added to assemble a laminated battery, which is the lithium-ion secondary battery of Example 1.

[0104] Example 2

[0105] Doped high nickel cathode material Li 0.96 Na 0.04 Ni 0.8 Co 0.1 Mn 0.1 Preparation of O2

[0106] First, nickel acetate, cobalt acetate, and manganese acetate are added to deionized water in a stoichiometric ratio and stirred thoroughly. The sodium carbonate solution is quickly poured into the transition metal salt solution and the reaction continues for 9 hours. The mixture is then allowed to age for 4 hours to allow for primary particle growth. The product is then washed three times with deionized water, dried in a blast dryer, and vacuum-dried at 100°C for 12 hours. The dried solid is collected as the precursor.

[0107] The precursor was mixed with lithium carbonate and sodium carbonate in a molar ratio of 1:1.05:0.04, and then ground. The excess lithium carbonate was used to compensate for the loss of lithium during high-temperature calcination. The fully ground solid powder was transferred to a crucible and placed in a muffle furnace with programmed temperature rise. The calcination procedure was: pre-calcination from room temperature to 500°C for 5 hours, and then calcined at a high temperature of 800°C for 12 hours, with a heating rate of 3°C min -1 The resulting material was then collected after cooling to room temperature.

[0108] The preparation process of the lithium-ion battery of Example 2 is the same as that of Example 1, except that the positive electrode material used is the positive electrode material prepared according to Example 2.

[0109] Comparative Example 1

[0110] Undoped cathode material LiNi0 .8 Co 0.1 Mn 0.1 Preparation of O2

[0111] First, nickel acetate, cobalt acetate, and manganese acetate are added to deionized water in a stoichiometric ratio and stirred thoroughly. The sodium carbonate solution is quickly poured into the transition metal salt solution and the reaction continues for 9 hours. The product is then allowed to age for 4 hours to allow for primary particle growth. The product is then washed three times with deionized water, dried in a blast dryer, and vacuum-dried at 100°C for 12 hours. The dried solid is collected as the precursor.

[0112] The precursor and lithium carbonate were mixed evenly in a molar ratio of 1:1.07, and then ground. The excess lithium carbonate was used to compensate for the loss of lithium during high-temperature calcination. The fully ground solid powder was transferred to a crucible and placed in a muffle furnace with programmed temperature rise. The calcination procedure was: pre-calcination from room temperature to 500°C for 5 hours, and then calcined at a high temperature of 800°C for 12 hours, with a heating rate of 3°C min -1 The resulting material was then collected after cooling to room temperature.

[0113] The preparation process of the lithium ion battery of Comparative Example 1 is the same as that of Example 1, except that the positive electrode material used is the positive electrode material prepared according to the method described in Comparative Example 1.

[0114] Comparative Example 2

[0115] Cathode material Li 0.4 Na 0.6 Ni 0.8 Co 0.1 Mn 0.1 Preparation of O2

[0116] First, nickel acetate, cobalt acetate, and manganese acetate are added to deionized water in a stoichiometric ratio and stirred thoroughly. The sodium carbonate solution is quickly poured into the transition metal salt solution and the reaction continues for 9 hours. The product is then allowed to age for 4 hours to allow for primary particle growth. The product is then washed three times with deionized water, dried in a blast dryer, and vacuum-dried at 100°C for 12 hours. The dried solid is collected as the precursor.

[0117] The precursor was mixed evenly with lithium carbonate and sodium carbonate in a molar ratio of 1:0.43:0.6, and then ground. The excess lithium carbonate was used to compensate for the loss of lithium during high-temperature calcination. The fully ground solid powder was transferred to a crucible and placed in a muffle furnace with programmed temperature rise. The calcination procedure was: pre-calcination from room temperature to 500°C for 5 hours, and then calcined at a high temperature of 800°C for 12 hours, with a heating rate of 3°C min -1 The resulting material was then collected after cooling to room temperature.

[0118] The preparation process of the lithium ion battery of Comparative Example 2 is the same as that of Example 1, except that the positive electrode material used is the positive electrode material prepared according to the method described in Comparative Example 2.

[0119] Comparative Example 3

[0120] Cathode material Li 0.9996 Na 0.0004 Ni 0.8 Co 0.1 Mn 0.1 Preparation of O2

[0121] First, nickel acetate, cobalt acetate, and manganese acetate are added to deionized water in a stoichiometric ratio and stirred thoroughly. The sodium carbonate solution is quickly poured into the transition metal salt solution and the reaction continues for 9 hours. The product is then allowed to age for 4 hours to allow for primary particle growth. The product is then washed three times with deionized water, dried in a blast dryer, and vacuum-dried at 100°C for 12 hours. The dried solid is collected as the precursor.

[0122] The precursor was mixed evenly with lithium carbonate and sodium carbonate in a molar ratio of 1:1.07:0.0004, and then ground. The excess lithium carbonate was used to compensate for the loss of lithium during high-temperature calcination. The fully ground solid powder was transferred to a crucible and placed in a muffle furnace with programmed temperature rise. The calcination procedure was: pre-calcination from room temperature to 500°C for 5 hours, and then calcined at a high temperature of 800°C for 12 hours, with a heating rate of 3°C min -1 The resulting material was then collected after cooling to room temperature.

[0123] The preparation process of the lithium ion battery of Comparative Example 3 is the same as that described in Example 1, except that the positive electrode material used is the positive electrode material prepared according to the method described in Comparative Example 3.

[0124]

Battery performance test

[0125] 1. Gram capacity of positive electrode material

[0126] A button cell was made, charged at a constant voltage after a constant current of 0.1C, and then discharged at 0.1C. The capacity was measured and divided by the mass of the active material to obtain the gram capacity.

[0127] 2. Cycle performance test:

[0128] The cycle test conditions are as follows: the secondary battery is subjected to a 1C / 1C cycle test at 25°C and 45°C, with a charge and discharge voltage range of 2.8 to 4.35V, and the test is stopped when the capacity decays to 80% of the initial discharge capacity.

[0129] The lithium ion batteries prepared in Examples 1-2 and Comparative Examples 1-3 were subjected to the performance tests described above, and the test results are summarized in Table 1 below.

[0130] Table 1

[0131]

[0132] As can be seen from the results in Table 1, by using cations L with larger ionic radius to dope and replace the Li ions in the positive electrode material to a certain extent, the structural stability of the positive electrode material can be effectively improved, and the cycle life of the lithium ion battery can be improved. In addition, the ratio of the molar amount of the doping element to the gram capacity needs to be controlled within a certain range. Excessive doping (Comparative Example 2) and insufficient doping (Comparative Example 3) may both lead to insufficient improvement in the cycle life of the lithium ion battery.

[0133] Although the present application has been described with reference to the embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A multi-cation positive electrode material, the general formula of the positive electrode material is LiaLxNibCocMndM(1-bcd)OeNf or mLi2MnO3•(1-m)LiaLxNibCocMndM(1-bcd)OeNf, wherein the L ion is a cation having a radius larger than the Li ion radius, M includes at least one of Mg, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, N includes at least one of F, S, and P, 0<a<1, 0≤b<1, 0≤c<1, 0≤d<1, 0<b+c+d≤1, 0<e≤2, 0≤f<2, 0<m<1, 0<x≤0.8, a+x=1, e+f=2, And the following relationship is satisfied: 2.5×10-6≤x / v≤2.5×10-3, where v is the gram capacity of the multi-cation positive electrode material. The positive electrode material according to claim 1 , wherein 0.001<x≤0.

5.

3. The positive electrode material according to claim 1, wherein x and v satisfy the following formula: 2.5×10-5≤x / v≤2.5×10-4. The positive electrode material according to claim 1 , wherein the gram capacity v of the positive electrode material satisfies 120 mAh / g≤v≤300 mAh / g. 5 . The cathode material according to claim 1 , wherein the L ion element includes at least one of alkali metal elements, alkaline earth metal elements, transition metal elements, and other main group metal elements other than lithium.

6. The positive electrode material according to claim 5, wherein the alkali metal element includes at least one of Na, K, Rb, and Cs; the alkaline earth metal element includes at least one of Mg, Ca, and Sr; the transition metal element includes Y; and the other main group metal elements include Bi. 7 . The cathode material according to claim 6 , wherein the elements of the L ions include at least two of Na, K, Rb, and Cs. The positive electrode material according to claim 1 , wherein a satisfies 0.5≤a<1. The cathode material according to claim 1 , wherein 0.05≤b≤0.98, and 0.05≤c≤0.

85. 10 . A lithium ion battery comprising a positive electrode, wherein the positive electrode comprises the multi-cation positive electrode material according to claim 1 . 11 . The lithium ion battery according to claim 10 , comprising a negative electrode, wherein a negative electrode active material of the negative electrode comprises at least one of graphite, hard carbon, and soft carbon.

12. An electrical device comprising the lithium-ion battery according to claim 10 or 11.

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