Lithium-containing transition metal oxide, method for preparing same, and related device comprising same

Abstract

The present application relates to a lithium-containing transition metal oxide, a method for preparing same, and a related device comprising same. A lithium ion battery comprises a positive electrode active material, wherein the positive electrode active material comprises a lithium-containing transition metal oxide, the lithium-containing transition metal oxide comprises an L element, and the L element comprises one or more elements of Na, K, Mg, Ca, Sr, Bi, Cu, and Y. The lithium-containing transition metal oxide comprises secondary particles, the secondary particles comprise a plurality of primary particles, and the lithium-containing transition metal oxide satisfies: Mi / M0 is 30% to 100%, wherein on the basis of the mass of the secondary particles, the mass content of the L element located in the secondary particles is M0, and on the basis of the mass of the secondary particles, the doping content of the L element located in the secondary particles is Mi. The present application can achieve improvement of the cycle performance of the lithium ion battery.

Description

Lithium-containing transition metal oxide, preparation method, and related device containing the same

[0001] Citations of Related Applications

[0002] This application claims priority to Chinese patent application No. 202410261191.0 filed on March 7, 2024, entitled “Positive Electrode Active Material and Preparation Method, Positive Electrode Sheet, Battery and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of batteries, and in particular to a lithium-containing transition metal oxide, a preparation method thereof, and related devices containing the same. Background Art

[0004] Lithium-ion batteries are widely used due to their reliable performance, pollution-free operation, and lack of memory effect. For example, with increasing attention paid to environmental protection and the growing popularity of new energy vehicles, the demand for power lithium-ion batteries is expected to experience explosive growth.

[0005] As lithium-ion batteries become increasingly widely used, the requirements for their performance are becoming increasingly stringent. As a key component in lithium-ion batteries, cathode active materials significantly influence their performance. However, the cycling performance of lithium-ion batteries remains poor and needs further improvement. Summary of the Invention

[0006] The present application provides a lithium-containing transition metal oxide and a preparation method, and related devices containing the same, which can improve the cycle performance of lithium-ion batteries when the positive electrode active material is used in the battery.

[0007] In a first aspect, the present application proposes a lithium-ion battery, the lithium-ion battery comprising a positive electrode plate, the positive electrode plate comprising a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material, the positive electrode active material comprising a lithium-containing transition metal oxide, the lithium-containing transition metal oxide comprising an L element, the L element comprising one or more elements selected from the group consisting of Na, K, Mg, Ca, Sr, Bi, Cu, and Y; the lithium-containing transition metal oxide comprising secondary particles, the secondary particles comprising a plurality of primary particles, the lithium-containing transition metal oxide satisfying: M i / M0 is 30% to 100%, wherein the mass content of the L element in the secondary particles is M0 based on the mass of the secondary particles; the doping content of the L element in the secondary particles is M based on the mass of the secondary particles. i .

[0008] Therefore, when the L element in the embodiment of the present application meets the above range, it can effectively support the lithium layer, and during the process of lithium ion release, the crystal structure is not easy to collapse and the structure is relatively stable; when the lithium-containing transition metal oxide is applied to lithium-ion batteries, the cycle performance of the lithium-ion battery can be more effectively improved.

[0009] In some embodiments, based on the mass of the secondary particles, the doping content M of the L element in the secondary particles is i It is 300ppm to 15000ppm; optionally 300ppm to 14000ppm; optionally 400ppm to 5000ppm; further optionally 3400ppm to 4650ppm.

[0010] Therefore, when the mass content of the L element located in the lithium layer in the embodiment of the present application is within the above range, the L element can effectively support the lithium layer and will not occupy too many lithium sites, so that the lithium-containing transition metal oxide can release sufficient lithium ions during the charging process, so that the lithium-containing transition metal oxide can exert excellent capacity characteristics.

[0011] In some embodiments, based on the mass of the secondary particles, the mass content M0 of the L element located in the secondary particles is 300 ppm to 32000 ppm; optionally 800 ppm to 8000 ppm.

[0012] Therefore, when the mass content of the L element in the embodiment of the present application is within the above range, the crystal structure is not easy to collapse and the structure is relatively stable; when the lithium-containing transition metal oxide is applied to lithium-ion batteries, the cycle performance of the lithium-ion battery can be more effectively improved.

[0013] In some embodiments, M i / M0 is 30% to 60%, and can be optionally 40% to 60%.

[0014] Therefore, in the embodiment of the present application, M i When / M0 is within the above range, the doping content of the L element is relatively high, so that the content of the L element in the primary particle is relatively high, which can effectively enhance the supporting effect of the L element on the lithium layer, improve the stability of the lithium-containing transition metal oxide, and thus enhance the cycle performance of the lithium-ion battery.

[0015] In some embodiments, the primary particle includes a central region and a peripheral region surrounding the central region, the peripheral region is a region extending from the outer surface of the primary particle to the interior of the primary particle within a distance of less than 5 nm, wherein the average unit area content of the L element located in the peripheral region is greater than the average unit area content of the L element located in the central region, and the mass content of the L element located in the central region is greater than 0 ppm; optionally, the mass content of the L element located in the central region is 300 ppm to 3000 ppm.

[0016] Therefore, the distribution of the L element in the embodiment of the present application satisfies the above conditions, and the L element can be distributed in the central area, thereby effectively supporting the lithium layer.

[0017] In some embodiments, the lithium transition metal oxide contains multiple lithium layers, and the distance between two adjacent lithium layers is to Optionally, the distance between two adjacent lithium layers is to

[0018] Therefore, in the embodiment of the present application, the lithium layer includes an L element with a relatively large ionic radius, so that the distance between two adjacent lithium layers meets the above range, which can further improve the structural stability of the lithium-containing transition metal oxide.

[0019] In some embodiments, the lithium-containing transition metal oxide includes a lithium-nickel composite oxide. The addition of nickel element is beneficial to improving the energy density of the battery cell.

[0020] In some embodiments, the lithium-containing transition metal oxide includes lithium-containing nickel-cobalt-manganese oxide. The addition of nickel element is beneficial to improving the energy density of the battery cell.

[0021] In some embodiments, the transition metal element of the lithium-containing transition metal oxide includes nickel, and the molar content of nickel relative to the total molar amount of the transition metal element is 80% to 100%. When the molar content of nickel is within the above range, it is beneficial to improve the energy density of the battery cell.

[0022] In some embodiments, the lithium-containing transition metal oxide comprises a general formula of Li a L x Ni b Co c Mn d M (1-b-c-d) O e R f The material, M element includes one or more elements of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, Ta, Mo, W, Nb, Sb and La, R element includes one or more elements of F, S, P and B, 0 <a<2,0<x≤0.8,0≤b≤1,0≤c≤1,0≤d≤1,0<b+c+d≤1,0<e≤2,0≤f<2。

[0023] In some embodiments, 0.001 ≤ x ≤ 0.20; optionally, 0.05 ≤ x ≤ 0.10. When the content of the L element is within the above range, the L element can provide good support for the lithium layer, thereby further improving the structural stability of the lithium-containing transition metal oxide. Furthermore, since the lithium layer is primarily composed of lithium ions, the specific capacity of the lithium-containing transition metal oxide is relatively high.

[0024] In some embodiments, 0.50≤b≤1.00. Alternatively, 0.80≤b≤0.99. When b is within the above range, the molar proportion of Ni is relatively high. As the molar proportion of nickel increases, the gram capacity of the lithium-containing transition metal oxide is relatively high, which is beneficial to improving the energy density of the lithium-ion battery. In the embodiment of the present application, the lithium-containing transition metal oxide also includes L element, and at least part of the L element is located in the lithium layer, which can effectively support the lithium layer and improve the structural stability of the lithium-containing transition metal oxide.

[0025] In some embodiments, the L element includes one or more elements selected from the group consisting of Na, K, and Ca. Alternatively, the L element includes Na. When the above elements are present in the lithium-containing transition metal oxide, the lithium-containing transition metal oxide has a higher structural stability.

[0026] In some embodiments, the lithium-containing transition metal oxide comprises Li 0.99 Na 0.01 Ni 0.92 Co 0.07 Mn 0.01 O2、Li 0.95 Na 0.05 Ni 0.92 Co 0.07 Mn 0.01 O2、Li 0.995 Na 0.005 Ni 0.92 Co 0.07 Mn 0.01 O2、Li 0.90 Na 0.1 Ni 0.92 Co 0.07 Mn 0.01 O2、Li 0.8 Na 0.2 Ni 0.92 Co 0.07 Mn 0.01 O2、Li 0.95 Na 0.05 Ni 0.92 Co 0.06 Mn 0.01 Mg 0.01 O2、Li 0.95 Na 0.05 Ni 0.92 Co0.06 Mn 0.01 Al 0.01 O2、Li 0.95 Na 0.05 Ni 0.915 Co 0.11 Mn 0.01 Al 0.01 O2、Li 0.95 Na 0.05 Ni 0.94 Co 0.085 Mn 0.01 Al 0.01 O2、Li 0.95 Na 0.05 Ni 0.94 Co 0.05 Mn 0.01 O2、Li 0.95 Na 0.05 Ni 0.90 Co 0.08 Mn 0.01 Al 0.01 O2 and Li 0.95 Na 0.05 Ni 0.55 Co 0.07 Mn 0.38 One or more materials in O2.

[0027] In some embodiments, the lithium-containing transition metal oxide comprises a general formula of Li a L x Ni b Co c Mn d M (1-b-c-d) O e R f The material, L element includes Na element, 0.001≤x≤0.20, the X-ray diffraction spectrum of the lithium-containing transition metal oxide includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the peak intensity I of the diffraction peak of the (003) crystal plane is (003) The peak intensity of the diffraction peak of the (104) crystal plane is (104) The ratio is R1;

[0028] Li a Ni b Co c Mn d M (1-b-c-d) O e R f The X-ray diffraction pattern includes the diffraction peak of (003) crystal plane and the diffraction peak of (104) crystal plane. The peak intensity of the diffraction peak of (003) crystal plane is I (003) The peak intensity of the diffraction peak of the (104) crystal plane is(104) The ratio is R0;

[0029] Among them, R1 / R0 is 1 to 1.7, and can be optionally 1.1 to 1.2.

[0030] Therefore, the lithium transition metal oxide in the embodiment of the present application is (003) / I (104) When the above range is met, the degree of mixing of lithium and nickel cations in the lithium-containing transition metal oxide is relatively low, and the lithium layer structure is more stable.

[0031] In some embodiments, the X-ray diffraction pattern of the lithium-containing transition metal oxide includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the peak intensity I of the diffraction peak of the (003) crystal plane is (003) The peak intensity of the diffraction peak of the (104) crystal plane is (104) The ratio is 1.46 to 2.00; optionally, the peak intensity of the diffraction peak of the (003) crystal plane is I (003) The peak intensity of the diffraction peak of the (104) crystal plane is (104) The ratio is 1.46 to 1.60.

[0032] Therefore, the lithium transition metal oxide in the embodiment of the present application is (003) / I (104) When the above range is met, the degree of lithium-nickel cation mixing in the lithium-containing transition metal oxide is relatively low, the lattice distortion is relatively small, and the nickel ions have little effect on the migration of lithium ions during charging; and the L element is located in the lithium layer, which increases the lattice spacing, further reducing the lattice distortion caused by lithium-nickel mixing, making the lattice arrangement more orderly, and the lithium layer structure more stable.

[0033] In some embodiments, the surface of the secondary particles further includes a coating layer, wherein a portion of the L element is located in the primary particles, and another portion of the L element is located in the coating layer. The L element located in the primary particles can support the lithium layer, and the coating layer acts as an interfacial bridge barrier, which can protect the transition metal oxide particles, reduce the corrosion effect of the electrolyte on the transition metal oxide particles in the lithium-ion battery, reduce the electrolyte's disturbance of the internal crystal structure of the transition metal oxide particles, further improve the structural stability of the transition metal oxide particles, and thereby improve the cycling performance of the lithium-ion battery.

[0034] In some embodiments, the coating layer further includes acid ions, and the acid ions include one or more of inorganic acid ions and organic acid ions.

[0035] In some embodiments, the inorganic acid ions include one or more of hydroxide, carbonate, sulfate, nitrate, and chloride ions.

[0036] In some embodiments, the organic acid ions include one or more of acetate, formate, oxalate, and sulfonate.

[0037] In some embodiments, the coating layer has a thickness greater than 0 nm and less than or equal to 15 nm; optionally, the coating layer has a thickness of 0.5 nm to 6.0 nm. A coating layer thickness within this range can effectively protect the transition metal oxide particles, reducing the risk of side reactions caused by direct contact between the transition metal oxide particles and the electrolyte in the lithium-ion battery, thereby improving the cycling performance of the lithium-ion battery. Furthermore, the coating layer is not excessively thick, substantially not affecting the transport of lithium ions, resulting in superior kinetic performance.

[0038] In some embodiments, the volume average particle size D of the secondary particles is v50 4 μm to 13 μm; Optionally, the volume average particle size D of the lithium-containing transition metal oxide v50 When the volume average particle size of the lithium-containing transition metal oxide is within the above range, its dynamic performance is relatively excellent.

[0039] In some embodiments, the average particle size of the primary particles is 200 nm to 2000 nm. When the average particle size of the primary particles is within the above range, the kinetic properties are relatively excellent.

[0040] In some embodiments, the lithium-containing transition metal oxide has a discharge capacity per gram of 180 mAh / g to 235 mAh / g; alternatively, the discharge capacity per gram of 215 mAh / g to 235 mAh / g. The relatively high capacity per gram of the lithium-containing transition metal oxide is beneficial for improving the energy density of lithium-ion batteries.

[0041] In some embodiments, the resistivity of the lithium-containing transition metal oxide powder is between 100 Ω*cm and 2000 Ω*cm. When the resistivity of the lithium-containing transition metal oxide powder is within this range, it is slightly increased, so that the resistance of the positive electrode sheet is within an appropriate range, which can reduce the risk of thermal runaway and effectively improve the reliability of the lithium-ion battery.

[0042] In some embodiments, the tap density of the lithium-containing transition metal oxide is 1.5 g / cm 3 Up to 3.0g / cm 3 When the tap density of the lithium-containing transition metal oxide is within the above range, it is beneficial to improve the energy density of the lithium-ion battery.

[0043] In some embodiments, the lithium transition metal oxide contained satisfies: the pH value of the lithium transition metal oxide solution is 11 to 13, wherein the lithium transition metal oxide is dissolved in deionized water to form a lithium transition metal oxide solution, wherein the mass content of the lithium transition metal oxide in the lithium transition metal oxide solution is 10%.

[0044] In some embodiments, the resistance of the positive electrode plate is 0.3Ω to 1.0Ω. The resistance of the positive electrode plate within the above range is beneficial to improving the dynamic performance of the lithium-ion battery.

[0045] In the second aspect, the present application proposes a lithium-containing transition metal oxide, which has a layered structure, and the lithium-containing transition metal oxide includes L elements, and the L elements include one or more elements of Na, K, Mg, Ca, Sr, Bi, Cu and Y; the lithium-containing transition metal oxide includes secondary particles, and the secondary particles include multiple primary particles, and the lithium-containing transition metal oxide includes secondary particles, and the secondary particles include multiple primary particles, and the lithium-containing transition metal oxide satisfies: M i / M0 is 30% to 100%, wherein the mass content of the L element in the secondary particles is M0 based on the mass of the secondary particles; the doping content of the L element in the secondary particles is M based on the mass of the secondary particles. i .

[0046] Therefore, when the L element in the embodiment of the present application meets the above range, it can effectively support the lithium layer. During the process of lithium ion release, the crystal structure is not easy to collapse and the structure is relatively stable.

[0047] In some embodiments, based on the mass of the secondary particles, the doping content M of the L element in the secondary particles is i It is 300ppm to 15000ppm, optionally 300ppm to 14000ppm; optionally 400ppm to 5000ppm; further optionally 3400ppm to 4650ppm.

[0048] Therefore, when the mass content of the L element located in the lithium layer in the embodiment of the present application is within the above range, the L element can effectively support the lithium layer and will not occupy too many lithium sites, so that the lithium-containing transition metal oxide can release sufficient lithium ions during the charging process, so that the lithium-containing transition metal oxide can exert excellent capacity characteristics.

[0049] In some embodiments, based on the mass of the secondary particles, the mass content M0 of the L element located in the secondary particles is 100 ppm to 32000 ppm; optionally 800 ppm to 8000 ppm.

[0050] Therefore, when the mass content of the L element in the embodiment of the present application is within the above range, the crystal structure is not easy to collapse and the structure is relatively stable; when the lithium-containing transition metal oxide is applied to lithium-ion batteries, the cycle performance of the lithium-ion battery can be more effectively improved.

[0051] In some embodiments, based on the mass of the secondary particles, the mass content of the L element in the secondary particles is M0, and the doping content of the L element in the secondary particles is M0. i , where M i / M0 is 30% to 60%, optionally, M i / M0 is 40% to 60%.

[0052] Therefore, in the embodiment of the present application, M i When / M0 is within the above range, it can effectively enhance the supporting effect of the L element on the lithium layer, improve the stability of the lithium-containing transition metal oxide, and thus enhance the cycle performance of the lithium-ion battery.

[0053] In some embodiments, the primary particle includes a central region and a peripheral region surrounding the central region, the peripheral region is a region extending from the outer surface of the primary particle to the interior of the primary particle within a distance of less than 5 nm, wherein the average unit area content of the L element located in the peripheral region is greater than the average unit area content of the L element located in the central region, and the mass content of the L element located in the central region is greater than 0 ppm; optionally, the mass content of the L element located in the central region is 300 ppm to 3000 ppm.

[0054] Therefore, the distribution of the L element in the embodiment of the present application satisfies the above conditions, and the L element can be distributed in the central area, thereby effectively supporting the lithium layer.

[0055] In some embodiments, the lithium transition metal oxide contains multiple lithium layers, and the distance between two adjacent lithium layers is to Optionally, the distance between two adjacent lithium layers is to

[0056] Therefore, in the embodiment of the present application, the lithium layer includes an L element with a relatively large ionic radius, so that the distance between two adjacent lithium layers meets the above range, which can further improve the structural stability of the lithium-containing transition metal oxide.

[0057] In some embodiments, the lithium-containing transition metal oxide includes a lithium-nickel composite oxide, which may be a lithium-containing nickel-cobalt-manganese oxide. The addition of nickel is beneficial for improving the energy density of the battery cell.

[0058] In some embodiments, the transition metal element of the lithium-containing transition metal oxide includes nickel, and the molar content of nickel relative to the total molar amount of the transition metal element is 80% to 100%. When the molar content of nickel is within the above range, it is beneficial to improve the energy density of the battery cell.

[0059] In some embodiments, the lithium-containing transition metal oxide comprises a general formula of Li a L x Ni b Co c Mn d M (1-b-c-d) O e R f The material, L element includes Na element, 0.001≤x≤0.20, the X-ray diffraction spectrum of the lithium-containing transition metal oxide includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the peak intensity I of the diffraction peak of the (003) crystal plane is (003) The peak intensity of the diffraction peak of the (104) crystal plane is (104) The ratio is R1;

[0060] Li a Ni b Co c Mn d M (1-b-c-d) O e R f The X-ray diffraction pattern includes the diffraction peak of (003) crystal plane and the diffraction peak of (104) crystal plane. The peak intensity of the diffraction peak of (003) crystal plane is I (003) The peak intensity of the diffraction peak of the (104) crystal plane is (104) The ratio is R0;

[0061] Among them, R1 / R0 is 1 to 1.7.

[0062] Therefore, the lithium transition metal oxide in the embodiment of the present application is (003) / I (104) When the above range is met, the degree of mixing of lithium and nickel cations in the lithium-containing transition metal oxide is relatively low, and the lithium layer structure is more stable.

[0063] In some embodiments, the X-ray diffraction pattern of the lithium-containing transition metal oxide includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the peak intensity I of the diffraction peak of the (003) crystal plane is (003) The peak intensity of the diffraction peak of the (104) crystal plane is (104) The ratio is 1.46 to 2.00, optionally 1.46 to 1.60.

[0064] Therefore, the lithium transition metal oxide in the embodiment of the present application is(003) / I (104) When the above range is met, the degree of lithium-nickel cation mixing in the lithium-containing transition metal oxide is relatively low, the lattice distortion is relatively small, and the nickel ions have little effect on the migration of lithium ions during charging; and the L element is located in the lithium layer, which increases the lattice spacing, further reducing the lattice distortion caused by lithium-nickel mixing, making the lattice arrangement more orderly, and the lithium layer structure more stable.

[0065] In a third aspect, the present application also proposes a method for preparing a lithium-containing transition metal oxide, comprising providing a transition metal precursor; mixing the transition metal precursor, a lithium source, and an L source, and calcining to obtain a lithium-containing transition metal oxide, wherein the L ions in the L source include cations corresponding to one or more elements selected from the group consisting of Na, K, Mg, Ca, Sr, Bi, Cu, and Y; wherein the lithium-containing transition metal oxide includes secondary particles, the secondary particles include a plurality of primary particles, and the lithium-containing transition metal oxide satisfies: M i / M0 is 30% to 100%, wherein the mass content of the L element in the secondary particles is M0 based on the mass of the secondary particles; the doping content of the L element in the secondary particles is M based on the mass of the secondary particles. i .

[0066] Therefore, according to the method of the embodiment of the present application, the L element in the L source can diffuse into the crystal structure of the lithium-containing transition metal oxide, and the L cation can enter the lithium layer to play a supporting role, which can improve the crystal structure stability of the lithium-containing transition metal oxide, thereby improving the cycle stability of the lithium-containing transition metal oxide.

[0067] In some embodiments, the molar ratio of the lithium source to the L source is 15 to 25. When the lithium source and the L source satisfy the above molar ratio, it is beneficial for more L source to be doped into the lithium layer.

[0068] In some embodiments, the step of mixing a transition metal precursor, a lithium source, and an L source and then calcining to obtain a transition metal oxide includes: mixing the transition metal precursor, the lithium source, and the L source to form an intermediate; and calcining the intermediate above the melting point of the L source to obtain the transition metal oxide.

[0069] Therefore, according to the method of the embodiment of the present application, the calcination treatment is carried out above the melting point of the L source, and the L source can melt during the calcination treatment and present a liquid phase. The calcination treatment is mainly solid-liquid phase sintering. The L cations in the liquid phase L source are easy to diffuse into the crystal structure of the lithium-containing transition metal oxide, and the L cations can enter the lithium layer to play a supporting role, which can improve the intrinsic lithium-nickel mixing phenomenon in the lithium-containing transition metal oxide, thereby improving the crystal structure stability of the lithium-containing transition metal oxide, thereby improving the cycle stability of the lithium-containing transition metal oxide.

[0070] In some embodiments, the step of calcining the intermediate above the melting point of the L source to obtain the transition metal oxide includes: subjecting the intermediate to a first calcination treatment to melt the L source in the intermediate into a liquid phase, wherein the temperature of the first calcination treatment is greater than or equal to the melting point of the L source; and subjecting the intermediate after the first calcination treatment to a second calcination treatment to obtain the transition metal oxide, wherein the temperature of the second calcination treatment is greater than the temperature of the first calcination treatment.

[0071] Multiple calcinations are beneficial for L cations to diffuse preferentially into the lattice structure and occupy the sites of the lithium layer; and the lithium ions in the lithium source diffuse into the lattice structure, thereby forming the desired material with a more stable crystal structure.

[0072] In some embodiments, the melting point of the L source is 200° C. to 600° C.; alternatively, the melting point of the L source is 210° C. to 400° C. The L source has a relatively low melting point and can melt during the first calcination process, which facilitates diffusion in a liquid phase, allowing the L element to be evenly dispersed in the lithium layer, providing a stable support.

[0073] In some embodiments, the L ions in the L source include cations corresponding to one or more elements selected from the group consisting of Na, K, Mg, Ca, Sr, Bi, Cu, and Y.

[0074] In some embodiments, the L source includes one or more of an inorganic L source and an organic L source.

[0075] In some embodiments, the anions in the inorganic L source include one or more of hydroxide, carbonate, sulfate, nitrate, and chloride.

[0076] In some embodiments, the anion in the organic L source includes one or more of acetate, formate, oxalate, and sulfonate.

[0077] In some embodiments, the transition metal precursor includes at least one of a nickel source, a cobalt source, and a manganese source. Alternatively, the transition metal precursor includes a nickel source, a cobalt source, and a manganese source.

[0078] In a fourth aspect, the present application further proposes a positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector and containing a positive electrode active material, wherein the positive electrode active material comprises a lithium-containing transition metal oxide, the lithium-containing transition metal oxide comprises an L element, and the L element comprises one or more elements selected from the group consisting of Na, K, Mg, Ca, Sr, Bi, Cu, and Y; wherein the lithium-containing transition metal oxide comprises secondary particles, the secondary particles comprise a plurality of primary particles, and the lithium-containing transition metal oxide satisfies: M i / M0 is 30% to 100%, wherein the mass content of the L element in the secondary particles is M0 based on the mass of the secondary particles; the doping content of the L element in the secondary particles is M based on the mass of the secondary particles. i .

[0079] In the fifth aspect, the present application also proposes a battery device comprising one or more lithium-ion batteries or positive electrode sheets as in any embodiment of the first aspect of the present application, the positive electrode sheet comprising a positive electrode active material, the positive electrode active material comprising a lithium-containing transition metal oxide in any embodiment of the second aspect of the present application or a lithium-containing transition metal oxide prepared by the preparation method of any embodiment of the third aspect of the present application.

[0080] In a sixth aspect, the present application further proposes an electrical device comprising a battery device according to any embodiment of the fifth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0082] FIG1 is a schematic diagram of an embodiment of a lithium-ion battery of the present application.

[0083] FIG. 2 is an exploded schematic diagram of the embodiment of the lithium-ion battery of FIG. 1 .

[0084] FIG3 is a schematic diagram of an embodiment of a battery module of the present application.

[0085] FIG4 is a schematic diagram of an embodiment of a battery pack of the present application.

[0086] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .

[0087] FIG6 is a schematic diagram of an embodiment of an electric device including the lithium-ion battery of the present application as a power source.

[0088] FIG7 is a scanning electron microscope (SEM) image of the positive electrode active material in Comparative Example 1-1 of the present application.

[0089] FIG8 is a scanning electron microscope (SEM) image of the positive electrode active material in Comparative Example 1-2 of the present application.

[0090] FIG9 is a scanning electron microscope (SEM) image of the positive electrode active material in Example 1-1 of the present application.

[0091] FIG10 is an X-ray diffraction XRD pattern of the positive electrode active materials in Comparative Example 1-1, Comparative Example 1-2 and Example 1-1 of the present application.

[0092] FIG11 is a grayscale diagram of X-ray diffraction (XRD) patterns of the positive electrode active materials in Comparative Example 1-1, Comparative Example 1-2, and Example 1-1 shown in FIG10 .

[0093] FIG12 is a schematic diagram of nickel element distribution in the positive electrode active material in Comparative Example 1-1.

[0094] FIG13 is a grayscale diagram showing the nickel element distribution of the positive electrode active material in Comparative Example 1-1.

[0095] FIG14 is a schematic diagram showing the distribution of nickel and sodium elements in the positive electrode active material in Example 1-1.

[0096] FIG15 is a grayscale diagram showing the distribution of nickel and sodium elements in the positive electrode active material in Example 1-1.

[0097] The accompanying drawings are described as follows: 1. battery pack; 2. upper case; 3. lower case; 4. battery module; 5. lithium-ion battery; 51. housing; 52. electrode assembly; 53. cover plate; 6. electrical device. DETAILED DESCRIPTION

[0098] The following detailed description of the embodiments of the present application is appropriately referred to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0099] " Range " disclosed in this application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3,4 and 5 are listed, then the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" are listed herein, and "0 to 5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0100] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0101] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0102] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0103] Cathode active materials are a crucial component of lithium-ion batteries, providing a source of freely intercalated and deintercalated lithium ions. These materials include lithium iron phosphate (LIFP) and lithium-containing transition metal oxides. Compared to LFP, LTOs have a higher energy density.

[0104] The lithium layer of the lithium-containing transition metal oxide may undergo cation mixing with the transition metal layer. The transition metal elements in the transition metal layer occupy the lithium layer position, resulting in a decrease in the lithium layer spacing in the crystal structure. The transition metal elements occupying the lithium layer position will be oxidized during the charging process, and their ion radius will further decrease, which may cause the structure of the lithium-containing transition metal oxide to collapse. When the lithium-containing transition metal oxide is used in lithium-ion batteries, it will cause the capacity and life to decay rapidly and the cycle performance to be poor.

[0105] In view of this, the embodiments of the present application propose a lithium-containing transition metal oxide, which includes an L element. The ionic radius corresponding to the L element is larger than the lithium ion radius. The L element is located in the lithium layer and occupies part of the lithium site, which can reduce the phenomenon of transition metal elements occupying lithium sites. Since the ionic radius of the L element is relatively large, it can effectively support the lithium layer and improve the crystal structure stability of the lithium-containing transition metal oxide. When the lithium-containing transition metal oxide is used in a lithium-ion battery, it can improve the cycle performance of the lithium-ion battery. The embodiments of the present application are described in detail below.

[0106] Lithium-containing transition metal oxides

[0107] In a first aspect, an embodiment of the present application provides a lithium-containing transition metal oxide.

[0108] The lithium-containing transition metal oxide has a layered structure, and the lithium-containing transition metal oxide includes L elements, and the L elements include one or more elements selected from the group consisting of Na, K, Mg, Ca, Sr, Bi, Cu, and Y;

[0109] The lithium-containing transition metal oxide includes secondary particles, and the secondary particles include a plurality of primary particles.

[0110] Lithium-containing transition metal oxides satisfy: M i / M0 is 30% to 100%,

[0111] in,

[0112] Based on the mass of the secondary particles, the mass content of the L element located in the secondary particles is M0;

[0113] Based on the mass of the secondary particles, the doping content of the L element in the secondary particles is M i .

[0114] The L element includes one or more elements selected from the group consisting of Na, K, Mg, Ca, Sr, Bi, Cu, and Y, the ionic radius of which is larger than that of lithium ions, and which can more easily enter the lithium site during doping.

[0115] The lithium-containing transition metal oxide includes secondary particles, which are formed by the aggregation of multiple primary particles. The primary particles include lithium layers and transition metal layers. The lithium layers and transition metal layers are alternately stacked, which is conducive to the insertion and extraction of lithium ions.

[0116] In the embodiment of the present application, the L element is mainly located in the lithium-containing transition metal oxide as a doping element, for example, located in the lithium layer of the primary particle to play the role of supporting the lithium layer; there may also be some L elements that do not enter the lithium layer, for example, located on the surface of the lithium-containing transition metal oxide, for example, located in the optional coating layer.

[0117] The L element can be located in the primary particles. The L element includes one or more elements selected from Na, K, Mg, Ca, Sr, Bi, Cu and Y. Its ionic radius is larger than that of lithium ions, and its valence state is the same or similar to that of lithium ions. It is easier to enter the lithium layer and occupy part of the lithium site during doping. The total mass content of the L element in all primary particles of the secondary particles can be understood as the doping content of the L element in the secondary particles, M. i ;

[0118] The total content of L elements in the secondary particles is recorded as the mass content of L elements in the secondary particles M0. In other words, the mass content of L elements M0 refers to the sum of the mass content of L elements in the primary particles and the mass content of L elements in the coating layer, that is, the doping content of L elements in the secondary particles M0. i and the optional sum of the mass contents of the L element in the coating layer.

[0119] The content of L element can be tested in accordance with EPA6010D-2014, and can be tested by plasma atomic emission ICP-OES spectrometry, using the ThermoICAP7400 plasma atomic emission device to detect the mass content of L element.

[0120] To measure the mass content (M0) of the L element in secondary particles, a 0.4g sample of a lithium-containing transition metal oxide was weighed and 10ml (50% concentration) of aqua regia was added. The sample was then placed on a plate at 180°C for 30 minutes. After digestion on the plate, the volume was adjusted to 100ml. The L element was quantitatively measured using a standard curve method to determine the mass content (M0) of the L element in the secondary particles.

[0121] When testing the doping content M of the L element in the secondary particles iWhen the lithium-containing transition metal oxide is taken, the lithium-containing transition metal oxide is washed with water, and the optional coating layer is removed as a sample; before and after washing with water, the lithium-containing transition metal oxide is subjected to scanning electron microscopy SEM testing, and the SEM image can be used to determine whether the coating layer has been removed. Weigh 0.4g of the sample and add 10ml (50% concentration) of aqua regia thereto. Then place it on a 180℃ plate for 30min. After digestion on the plate, the volume is fixed to 100mL, and the standard curve method is used to perform a quantitative test of the L element to obtain the doping content M of the L element located in the secondary particles. i .

[0122] In the embodiment of the present application, M i / M0 can represent the mass percentage of all L elements in the primary particles in the secondary particles. i The larger the value of / M0, the higher the mass proportion of L element in primary particles; i The smaller the value of / M0, the lower the mass proportion of the L element located in the primary particles.

[0123] When the doping content of L element is too low, the lithium layer cannot be effectively supported; i When / M0 is greater than or equal to 30%, the L element occupies part of the lithium site, which can reduce the phenomenon of transition metal elements occupying the lithium site. In addition, the ionic radius of the L element is relatively large, and it can also effectively support the lithium layer. During the process of lithium ion extraction, the crystal structure is not easy to collapse, and the structure is relatively stable, which can improve the crystal structure stability of the lithium-containing transition metal oxide. When the lithium-containing transition metal oxide is used in lithium-ion batteries, it can more effectively improve the cycle performance of the lithium-ion battery. i / M0 is less than or equal to 60%, and the doping content of the L element will not be too high, which can reduce the risk of excessive occupation of lithium sites and make the positive electrode plate have a relatively high capacity.

[0124] In the embodiment of the present application, M i / M0 can be 30% to 100%, optionally 30% to 60%, optionally 40% to 60%. i / M0 may be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 70%, 80%, 90%, 100% or a range consisting of any two of the above values.

[0125] M i When / M0 is 100%, it can be understood that the L element is basically all located in the primary particles, playing an effective supporting role for the lithium layer.

[0126] M iWhen / M0 is less than 100%, it can be understood that the L element is located not only in the primary particles but also partially in the coating layer.

[0127] M i When / M0 is within the above range, it can effectively enhance the supporting effect of the L element on the lithium layer, improve the stability of the lithium-containing transition metal oxide, and thus enhance the cycle performance of the lithium-ion battery.

[0128] The primary particles are divided into a central area and a peripheral area. The peripheral area is the area extending from the outer surface of the primary particle to the interior of the primary particle within 5 nm. The peripheral area can be understood as the outer shell, and the central area is the remaining area of ​​the primary particle, which can be understood as the core. The central area and the peripheral area are connected to each other, and the peripheral area is arranged around the central area. There may be no obvious boundary between the central area and the peripheral area, which is only an artificial division.

[0129] The average unit area content of the L element in the central area can be understood as taking a sample of area S (for example, 20nm*20nm) in the central area, sampling 32 times in parallel, calculating the content of the L element in the sample, and using the ratio of the content to the area S as the unit area content; taking multiple samples, calculating the unit area content respectively, and then calculating the average of the unit area content as the average unit area content.

[0130] The average unit area content of the L element in the peripheral area can be understood as taking a sample of area S (for example, 20nm*20nm) in the peripheral area, taking parallel samples 32 times, calculating the content of the L element in the sample, and using the ratio of the content to the area S as the unit area content; taking multiple samples, calculating the unit area content respectively, and then calculating the average of the unit area content as the average unit area content.

[0131] When testing the content of L element, the fully charged lithium-ion battery is disassembled, and the positive electrode sheet is taken out. The positive electrode sheet is cleaned with dimethyl carbonate DMC solvent, and focused ion beam FIB sectioning is performed along the thickness direction of the positive electrode sheet to obtain a cross section of the positive electrode film layer. Transmission electron microscopy TEM-energy dispersive X-ray spectroscopy EDX is used to test the element distribution of the positive electrode active material in the positive electrode film layer (as shown in the cross-sectional schematic diagrams of the positive electrode film layer of comparative example 1-1 in Figures 12 and 13, and the cross-sectional schematic diagrams of the positive electrode film layer of embodiment 1-1 in Figures 14 and 15).

[0132] The mass concentration of the L element in the peripheral area is greater, and the mass concentration of the L element in the central area is relatively small. In the embodiment of the present application, the average unit area content of the L element is used to qualitatively characterize the mass concentration. The average unit area content of the L element in the peripheral area is greater than the average unit area content of the L element in the central area.

[0133] During the charge and discharge process of lithium-ion batteries, lithium ions preferentially escape from the peripheral area and embed into the peripheral area. Increasing the lithium ion diffusion rate in the external area can greatly improve the lithium ion transmission rate and thus improve the electrochemical performance. The mass concentration of the L element in the peripheral area is relatively larger, which increases the distance between adjacent lithium layers, which is beneficial to the escape and embedding of lithium ions; the mass concentration of the L element in the central area is relatively smaller. On the one hand, the L element can effectively support the lithium layer and improve the crystal structure stability of the primary particles. On the other hand, it is beneficial to the escape and embedding of lithium ions in the central area. The structural stability of lithium-containing transition metal oxides is better. When lithium-containing transition metal oxides are used in lithium-ion batteries, the cycle stability of the lithium-containing transition metal oxides is relatively excellent, which can more effectively improve the cycle performance of lithium-ion batteries.

[0134] Optionally, the mass content of the L element in the central region is greater than 0 ppm; optionally, it is 300 ppm to 3000 ppm. For example, the mass content of the L element in the central region is 100 ppm, 300 ppm, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, or a range consisting of any two of the foregoing values.

[0135] The L element can be doped into the central region to enhance the support effect on the lithium layer and further improve the cycle performance.

[0136] In the embodiment of the present application, based on the mass of the secondary particles, the doping content M of the L element in the secondary particles is i Greater than or equal to 300ppm to 15000ppm, for example, 300ppm, 500ppm, 800ppm, 1000ppm, 1200ppm, 1500ppm, 1800ppm, 2000ppm, 2200ppm, 2500ppm, 2800ppm, 3000ppm, 3200ppm, 3500ppm, 3800ppm, 4000ppm, 4200ppm, 4500ppm, 4800ppm, 5000ppm, 6000ppm, 7000ppm, 8000ppm, 9000ppm, 10000ppm, 11000ppm, 12000ppm, 13000ppm, 14000ppm, 15000ppm or a range consisting of any two of the above values.

[0137] Alternatively, based on the mass of the secondary particles, the doping content M of the L element in the secondary particles may be i It is 300ppm to 14000ppm, optionally 400ppm to 5000ppm, optionally 3400ppm to 4650ppm.

[0138] When the doping content of the L element is within the above range, the L element can effectively support the lithium layer and will not occupy too many lithium sites, so that the lithium-containing transition metal oxide can release sufficient lithium ions during the charging process, so that the lithium-containing transition metal oxide can exert excellent capacity characteristics.

[0139] The lithium-containing transition metal oxide is in granular form and can be modified by coating, for example, with carbon or a compound containing the element L. It can also be modified by adding a doping transition metal element. Of course, the lithium-containing transition metal oxide can also be unmodified, for example, without coating.

[0140] In the case of coating modification, the coating layer is located on the surface of the secondary particles; in the case of doping modification, the transition metal elements are located in the primary particles.

[0141] In some embodiments, the lithium-containing transition metal oxide may not include a coating layer, and the L element is located in the primary particle. This arrangement makes the L element content in the lithium layer relatively high, provides excellent support for the lithium layer, and can effectively improve the stability of the crystal structure.

[0142] In other embodiments, the surface of the lithium-containing transition metal oxide includes a coating layer, wherein a portion of the L element is located in the primary particles, and another portion of the L element is located in the coating layer. The coating layer acts as an interfacial bridge barrier, protecting the transition metal oxide particles, reducing the corrosion of the transition metal oxide particles by the electrolyte in the lithium-ion battery, and reducing the electrolyte's disturbance of the internal crystal structure of the transition metal oxide particles, further improving the structural stability of the transition metal oxide particles, thereby enhancing the cycling performance of the lithium-ion battery.

[0143] In some embodiments, the mass content M0 of the L element located in the secondary particles is 300 ppm to 32000 ppm, for example, 300 ppm, 500 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1800 ppm, 2000 ppm, 2200 ppm, 2500 ppm, 2800 ppm, 3000 ppm, 3200 ppm, 3500 ppm, 3800 ppm, 4000 ppm, 4200 ppm, 4500 ppm, 4800 ppm, 5000 ppm, 5500 ppm, 6000 ppm, 6500 ppm, 7000 ppm, 7500 ppm, 7600 ppm, 7700 ppm, 7800 ppm, 7900 ppm, 8000 ppm, 8100 ppm, 8200 ppm, 8300 ppm, 8400 ppm, 8500 ppm, 8600 ppm, 8700 ppm, 8800 ppm, 8900 ppm, 9000 ppm, 9100 ppm, 9200 ppm, 9300 ppm, 9400 ppm, 9500 ppm, 9600 ppm, 9700 ppm, 9800 ppm, 9900 ppm, 10000 ppm, 10100 ppm ppm, 500ppm, 8000ppm, 9000ppm, 10000ppm, 11000ppm, 12000ppm, 13000ppm, 14000ppm, 15000ppm, 16000ppm, 17000ppm, 18000ppm, 19000ppm, 20000ppm, 21000ppm, 22000ppm, 23000ppm, 24000ppm, 25000ppm, 26000ppm, 27000ppm, 28000ppm, 29000ppm, 30000ppm, 31000ppm, 32000ppm, or a range consisting of any two of the above values. It should be noted that the mass content M0 of the L element refers to the mass content of all L elements in the lithium-containing transition metal oxide.

[0144] Optionally, the mass content M0 of the L element is 800 ppm to 8000 ppm based on the mass of the secondary particles.

[0145] In the case where the lithium-containing transition metal oxide does not include a coating layer, substantially all of the L element is located in the primary particles, for example, in the lithium layer.

[0146] In the case where the lithium-containing transition metal oxide also includes a coating layer, the L element is distributed in the primary particles and the coating layer. The mass content of the L element M0 refers to the sum of the mass content of the L element located in the primary particles and the mass content of the L element located in the coating layer, that is, the doping content of the L element located in the secondary particles M0. i and the sum of the mass contents of the L element located in the coating layer.

[0147] In some embodiments, the lithium-containing transition metal oxide comprises a plurality of lithium layers, and the distance between two adjacent lithium layers is to Optional to Optional to For example, the distance between two adjacent lithium layers is Or a range consisting of any two of the above values.

[0148] The lithium layer includes an L element with a relatively large ionic radius, so that the distance between two adjacent lithium layers meets the above range, which can further improve the structural stability of the lithium-containing transition metal oxide.

[0149] In an embodiment of the present application, the spacing between two adjacent lithium layers can be measured using a transmission electron microscope (TEM) to measure the spacing between two adjacent lithium layers. For example, a thin slice of about 100 nm is cut from the middle of a single particle, and then the slice is subjected to a transmission electron microscope (TEM) analysis test to obtain a TEM image. The dimensions of multiple (e.g., 5 or more) different positions on the TEM image are then measured, and at least 6 samples are tested. The average of the test results is taken as the spacing between two adjacent lithium layers.

[0150] Lithium-containing transition metal oxides include various materials depending on the transition metal element. For example, the transition metal element includes one or more of nickel, cobalt, manganese, and aluminum. Specifically, the lithium-containing transition metal oxide may include a lithium-nickel composite oxide. Further, the lithium-containing transition metal oxide includes one or more of lithium-containing nickel-cobalt-manganese oxide, lithium-containing nickel-cobalt-aluminum oxide, and lithium-containing nickel-cobalt-manganese-aluminum. Optionally, the lithium-containing transition metal oxide includes lithium-containing nickel-cobalt-manganese oxide.

[0151] In some embodiments, when the transition metal element includes nickel, the molar content of nickel relative to the total molar amount of the transition metal element is greater than or equal to 80% and less than or equal to 100%, such as 80%, 81%, 82%, 83%, 85%, 88%, 90%, 92%, 93%, 95%, 96%, 97%, 98%, 99%, 100%, or a range consisting of any two of the foregoing values. When the molar content of nickel is within the above range, the energy density of the battery cell is improved.

[0152] In the related art, the radii of nickel divalent ions and lithium ions in lithium-containing nickel-cobalt-manganese oxide are similar, and lithium-nickel mixing may occur, causing nickel divalent ions to migrate to the lithium layer to occupy lithium sites. The nickel divalent ions occupying the lithium layer will be oxidized into nickel trivalent ions with a smaller ion radius during the charging process of the lithium-ion battery, which may cause the crystal structure of the lithium-containing nickel-cobalt-manganese oxide to collapse; with the increase of nickel content, the lithium-nickel mixing intensifies and the risk of crystal structure collapse increases; in the embodiment of the present application, the ion radius of L is relatively large, and it can enter the lithium layer to occupy the lithium site, reducing the number of nickel divalent ions entering the lithium layer, thereby effectively alleviating the lithium-nickel mixing phenomenon; and the number of L entering the primary particles is relatively large, which can effectively support the lithium layer and improve the crystal structure stability of the positive electrode active material. When the positive electrode active material is applied to lithium-ion batteries, the cycle performance of the lithium-ion battery can be improved.

[0153] The crystal structure of lithium-containing nickel-cobalt-manganese oxide can be confirmed by X-ray diffraction (XRD) patterns, for example, by the peak intensity I of the diffraction peak of the (003) crystal plane. (003) The peak intensity of the diffraction peak of the (104) crystal plane is (104) The ratio of lithium nickel cations reflects the degree of mixing, I (003) / I (104) The larger the value of , the lower the degree of cation mixing. The peak intensity of the diffraction peak refers to the intensity represented by the maximum value (maximum height) of the diffraction peak in the XRD pattern. The peak intensity ratio of the X-ray diffraction peaks of the (003) crystal plane and the (104) crystal plane can be obtained from the X-ray diffraction pattern. The (003) crystal plane refers to the lattice plane corresponding to the Miller index (003), and the (104) crystal plane refers to the lattice plane corresponding to the Miller index (104).

[0154] Specifically, the test process can use an X-ray powder diffractometer (XRD, instrument model: Bruker D8 ADVANCE) to test the peak intensity of the crystal plane, for example, the target material is CuKα; the test parameters can use the parameter range known in the art and are not limited in the embodiments of this application.

[0155] In some embodiments, the X-ray diffraction pattern of the lithium-containing transition metal oxide includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the peak intensity I of the diffraction peak of the (003) crystal plane is (003) The peak intensity of the diffraction peak of the (104) crystal plane is (104) The ratio is 1.46 to 2.00; optionally 1.46 to 1.60. (003) / I (104) When the above range is met, the degree of lithium-nickel cation mixing in the lithium-containing transition metal oxide is relatively low, the lattice distortion is relatively small, and the nickel ions have little effect on the migration of lithium ions during charging; and the L element is located in the lithium layer, which increases the lattice spacing, further reducing the lattice distortion caused by lithium-nickel mixing, making the lattice arrangement more orderly, and the lithium layer structure more stable.

[0156] For example, I (003) / I (104) It can be 146, 1.48, 1.50, 1.52, 1.55, 1.58, 1.60, 1.62, 1.65, 1.68, 1.70, 1.72, 1.75, 1.78, 1.80, 1.85, 1.90, 1.95, 2.00 or a range consisting of any two of the above values.

[0157] Regardless of whether the lithium-containing transition metal oxide includes a coating layer, in some embodiments, the lithium-containing transition metal oxide includes a general formula of Lia L x Ni b Co c Mn d M (1-b-c-d) O e R f For the material of , element M represents the doping element of the transition metal layer in the transition metal oxide particles, element R includes one or more elements of F, S, P, and B, 0 < a < 2, 0 < x ≤ 0.8, 0 ≤ b ≤ 1, 0 ≤ c ≤ 1, 0 ≤ d ≤ 1, 0 < b + c + d ≤ 1, 0 < e ≤ 2, 0 ≤ f < 2.

[0158] 0 < x ≤ 0.8. Optionally, 0 < x ≤ 0.2. Further optionally, 0.001 ≤ x ≤ 0.200. Still further optionally, 0.05 ≤ x ≤ 0.10. When the content of element L is within the above range, element L can play a good supporting role for the lithium layer, thereby further improving the structural stability of the lithium-containing transition metal oxide; and the lithium layer is mainly composed of lithium ions, and the specific capacity of the lithium-containing transition metal oxide is relatively high.

[0159] Exemplarily, x can be 0.001, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.5, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80 or the range composed of any two of the above values.

[0160] 0≤b≤1, optionally, 0<b≤1, further optionally, 0.50≤b≤1.00, further optionally, 0.80≤b≤0.99. Exemplarily, b can be 0.01, 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.52, 0.55, 0.58, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68 , 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1 or a range consisting of any two of the above values.

[0161] When b is within the above range, the molar fraction of Ni is high. As the molar fraction of nickel increases, the gram capacity of the lithium-containing transition metal oxide increases, which is beneficial for improving the energy density of lithium-ion batteries. However, the higher the degree of lithium-nickel intermixing, the higher the risk of crystal structure collapse in the lithium-containing transition metal oxide. In the embodiment of the present application, the lithium-containing transition metal oxide also includes the L element, at least part of which is located in the lithium layer, which can effectively support the lithium layer and improve the structural stability of the lithium-containing transition metal oxide.

[0162] 0≤c≤1, optionally, 0<c≤1, further optionally, 0<c<1. c can be 0.01, 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.52, 0.55, 0.58, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0. 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1 or a range consisting of any two of the above values.

[0163] 0≤d≤1, optionally, 0<d≤1, further optionally, 0<d<1. d can be 0.01, 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.52, 0.55, 0.58, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 0.99, 0.91 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1 or a range consisting of any two of the above values.

[0164] Optionally, 0<b+c+d<1.

[0165] For example, b+c+d can be 0.01, 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.52, 0.55, 0.58, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99 or a range consisting of any two of the above values.

[0166] Alternatively, e can be 0.01, 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.52, 0.55, 0.58, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72 , 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or a range consisting of any two of the above values.

[0167] In the examples of the positive electrode active materials in the embodiments of the present application, the molar content of oxygen O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen O to change. In practice, the molar content of oxygen O will fluctuate.

[0168] In some embodiments, 0≤f<2.

[0169] For example, f can be 0, 0.01, 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.52, 0.55, 0.58, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.9 ... 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or a range consisting of any two of the above values.

[0170] In some embodiments, a can be 0.01, 0.02, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, 0.28, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.52, 0.55, 0.58, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or a range consisting of any two of the above values.

[0171] The charge and discharge process of lithium-ion batteries is accompanied by the deintercalation and consumption of active ions such as Li. The molar content of Li in lithium-ion batteries varies at different discharge states. The molar content of Li in the examples of positive electrode active materials in the embodiments of this application refers to the initial state of the material, i.e., the state before the material is added. When the positive electrode active material is used in a battery system, the molar content of Li may change after charge and discharge cycles.

[0172] The M element represents the doping element of the transition metal layer in the transition metal oxide particle. Optionally, the M element includes one or more elements selected from the group consisting of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, Ta, Mo, W, Nb, Sb, and La.

[0173] The L element may include one or more elements selected from the group consisting of Na, K, and Ca; optionally, the L element includes Na. These elements are located in the lithium-containing transition metal oxide, and their valence states are the same as or similar to those of lithium ions, making them more easily accessible to the lithium layer. Furthermore, their ionic radius is larger than that of lithium ions, allowing them to provide support within the lithium layer, thereby enhancing the structural stability of the lithium-containing transition metal oxide.

[0174] For example, the lithium-containing transition metal oxide may include Li 0.99 Na 0.01 Ni 0.92 Co 0.07 Mn 0.01 O2、Li 0.95 Na 0.05 Ni 0.92 Co 0.07 Mn0.01 O2、Li 0.995 Na 0.005 Ni 0.92 Co 0.07 Mn 0.01 O2、Li 0.90 Na 0.1 Ni 0.92 Co 0.07 Mn 0.01 O2、Li 0.8 Na 0.2 Ni 0.92 Co 0.07 Mn 0.01 O2、Li 0.95 Na 0.05 Ni 0.92 Co 0.06 Mn 0.01 Mg 0.01 O2、Li 0.95 Na 0.05 Ni 0.92 Co 0.06 Mn 0.01 Al 0.01 O2、Li 0.95 Na 0.05 Ni 0.915 Co 0.11 Mn 0.01 Al 0.01 O2、Li 0.95 Na 0.05 Ni 0.94 Co 0.085 Mn 0.01 Al 0.01 O2、Li 0.95 Na 0.05 Ni 0.94 Co 0.05 Mn 0.01 O2、Li 0.95 Na 0.05 Ni 0.90 Co 0.08 Mn 0.01 Al 0.01 O2 and Li 0.95 Na 0.05 Ni 0.55 Co 0.07 Mn 0.38 One or more materials in O2.

[0175] Alternatively, the lithium-containing transition metal oxide may include Li 0.99 Na 0.01 Ni 0.92 Co 0.07 Mn 0.01 O2、Li0.95 Na 0.05 Ni 0.92 Co 0.07 Mn 0.01 O2、Li 0.995 Na 0.005 Ni 0.92 Co 0.07 Mn 0.01 O2、Li 0.90 Na 0.1 Ni 0.92 Co 0.07 Mn 0.01 O2、Li 0.8 Na 0.2 Ni 0.92 Co 0.07 Mn 0.01 O2、Li 0.95 Na 0.05 Ni 0.92 Co 0.06 Mn 0.01 Mg 0.01 O2、Li 0.95 Na 0.05 Ni 0.92 Co 0.06 Mn 0.01 Al 0.01 O2、Li 0.95 Na 0.05 Ni 0.915 Co 0.11 Mn 0.01 Al 0.01 O2、Li 0.95 Na 0.05 Ni 0.94 Co 0.085 Mn 0.01 Al 0.01 O2、Li 0.95 Na 0.05 Ni 0.94 Co 0.05 Mn 0.01 O2 and Li 0.95 Na 0.05 Ni 0.90 Co 0.08 Mn 0.01 Al 0.01 One or more materials in O2.

[0176] In some embodiments, the lithium-containing transition metal oxide comprises a general formula of Li a L x Ni b Co c Mn d M (1-b-c-d) Oe R f The material, L element includes Na element, 0.001≤x≤0.20, the X-ray diffraction spectrum of the lithium-containing transition metal oxide includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the peak intensity I of the diffraction peak of the (003) crystal plane is (003) The peak intensity of the diffraction peak of the (104) crystal plane is (104) The ratio is R1;

[0177] Li a Ni b Co c Mn d M (1-b-c-d) O e R f The X-ray diffraction pattern includes the diffraction peak of (003) crystal plane and the diffraction peak of (104) crystal plane. The peak intensity of the diffraction peak of (003) crystal plane is I (003) The peak intensity of the diffraction peak of the (104) crystal plane is (104) The ratio is R0;

[0178] Wherein, R1 / R0 is 1 to 1.7, such as 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7 or a range consisting of any two of the above values. Optionally, R1 / R0 is 1.1 to 1.2.

[0179] I containing lithium transition metal oxides (003) / I (104) When the above range is met, the degree of mixing of lithium and nickel cations in the lithium-containing transition metal oxide is relatively low, and the lithium layer structure is more stable.

[0180] When the lithium-containing transition metal oxide further includes a coating layer, the coating layer includes L element, which mainly exists in the form of cations. The coating layer may further include acid ions, which include one or more of inorganic acid ions and organic acid ions.

[0181] Illustratively, the inorganic acid radical ions include one or more of hydroxide, carbonate, sulfate, nitrate, and chloride ions. For example, the coating layer includes sodium ions, and the main substance of the coating layer may include one or more of sodium hydroxide, sodium carbonate, sodium sulfate, sodium nitrate, or sodium chloride; for example, the coating layer may include a mixture of sodium hydroxide and sodium carbonate, and for another example, the coating layer may include sodium hydroxide. For another example, the coating layer includes potassium ions, and the main substance of the coating layer may include one or more of potassium hydroxide, potassium carbonate, potassium sulfate, potassium nitrate, or potassium chloride. For another example, the coating layer includes calcium ions, and the main substance of the coating layer may include one or more of calcium hydroxide, calcium carbonate, calcium sulfate, calcium nitrate, or calcium chloride.

[0182] For example, the organic acid radical ions include one or more of acetate, formate, oxalate, and sulfonate. For example, the coating layer includes sodium ions, and the main substance of the coating layer may include one or more of sodium acetate, sodium formate, sodium oxalate, or sodium sulfonate. For another example, the coating layer includes potassium ions, and the main substance of the coating layer may include one or more of potassium acetate, potassium formate, potassium oxalate, or potassium sulfonate. For another example, the coating layer includes calcium ions, and the main substance of the coating layer may include one or more of calcium acetate, calcium formate, calcium oxalate, or calcium sulfonate.

[0183] In the embodiment of the present application, the elements on the surface of the lithium-containing transition metal oxide, i.e., the elements in the coating layer, can be tested by X-ray EDX. The test can be performed by the following steps: taking the lithium-containing transition metal oxide as a sample, uniformly dispersing the sample in an ethanol solvent and ultrasonically dispersing it for uniform testing. It should be noted that the sample is required to be less than 100nm. If the particles are too large, focused ion beam FIB thinning treatment is required to allow the electron beam to penetrate the sample.

[0184] In some embodiments, the coating layer has a thickness greater than 0 nm and less than or equal to 15 nm, and can be selected from 0.5 nm to 6.0 nm. For example, the coating layer has a thickness of 0.2 nm, 0.5 nm, 1.0 nm, 1.5 nm, 2.0 nm, 2.5 nm, 3.0 nm, 3.5 nm, 4.0 nm, 4.5 nm, 5.0 nm, 6.0 nm, 7.0 nm, 8.0 nm, 9.0 nm, 10.0 nm, 11.0 nm, 12.0 nm, 13.0 nm, 14.0 nm, 15 nm, or a range consisting of any two of the foregoing values.

[0185] When the thickness of the coating layer is within the above range, it can provide good protection for the transition metal oxide particles and alleviate the side reactions between the electrolyte and the transition metal oxide particles.

[0186] In the embodiment of the present application, the thickness of the coating layer has a meaning well known in the art and can be detected by equipment and methods well known in the art. For example, a transmission electron microscope (TEM) is used to detect the thickness of the coating layer in the lithium-containing transition metal oxide. A thin slice of about 100 nm is cut from the middle of a single particle, and then the thin slice is subjected to a transmission electron microscope (TEM) analysis test to obtain a TEM image. Then, the thickness of multiple (for example, more than 5) different positions is measured on the TEM image, and at least 6 samples are tested. The average value of the test results is taken as the average thickness of the coating layer.

[0187] In some embodiments, the volume average particle size D of the secondary particles containing lithium transition metal oxide is v50The lithium-containing transition metal oxide can be 4 to 13 μm, optionally 6 to 13 μm, or 7.5 to 11.5 μm, for example, 4 μm, 5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8.0 μm, 8.5 μm, 9.0 μm, 9.5 μm, 10.0 μm, 10.5 μm, 11.0 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, or a range consisting of any two of the foregoing values. When the volume average particle size of the lithium-containing transition metal oxide is within the above range, its kinetic properties are relatively excellent.

[0188] In the embodiment of the present application, the volume average particle size D of the secondary particles containing lithium transition metal oxide is v50 The volume average particle size D of the lithium-containing transition metal oxide is well known in the art. v50 It refers to the particle size corresponding to 50% of the volume distribution. It can be tested using equipment and methods known in the art. A certain amount of lithium-containing transition metal oxide is taken as a sample and the volume average particle size D is measured by Mastersizer 2000E laser particle size analyzer according to the test standard GB / T19077-2016. v50 .

[0189] In some embodiments, the average particle size of the primary particles is 200 nm to 2000 nm, for example, 200 nm, 500 nm, 1000 nm, 1500 nm, 2000 nm, or a range consisting of any two of these values. When the average particle size of the primary particles is within this range, the kinetic properties of the lithium-containing transition metal oxide are further improved.

[0190] In the embodiment of the present application, the average particle size of the primary particles has a meaning well known in the art and can be detected using equipment and methods well known in the art. A certain amount of lithium-containing transition metal oxide is taken as a sample, and a thin slice of about 100 nm is cut from the middle of a single particle. The slice is then subjected to transmission electron microscopy (TEM) analysis to obtain a TEM image. The particle sizes of the primary particles at multiple (for example, more than 5) different positions are then measured on the TEM image, and at least 6 samples are tested. The average value of the test results is taken as the average particle size of the primary particles.

[0191] In some embodiments, the discharge capacity per gram of the lithium-containing transition metal oxide is from 180 mAh / g to 235 mAh / g, optionally from 200 mAh / g to 235 mAh / g, optionally from 215 mAh / g to 235 mAh / g, for example, 200 mAh / g, 225 mAh / g, 226 mAh / g, 227 mAh / g, 228 mAh / g, 229 mAh / g, 230 mAh / g, 231 mAh / g, 232 mAh / g, 233 mAh / g, 234 mAh / g, 235 mAh / g, or a range consisting of any two of the foregoing values. Specifically, the discharge capacity per gram of the lithium-containing transition metal oxide in a button cell at a rate of 0.1 C is from 180 mAh / g to 235 mAh / g, optionally from 200 mAh / g to 235 mAh / g, or optionally from 215 mAh / g to 235 mAh / g. The relatively high capacity per gram of the lithium-containing transition metal oxide is beneficial for improving the energy density of the lithium-ion battery.

[0192] In the embodiment of the present application, the discharge gram capacity of the positive electrode active material is the discharge gram capacity of the positive electrode active material in the button battery. The test of the gram capacity of the positive electrode active material can be carried out using equipment and methods known in the art. The test method of the first coulomb efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T24533-2019 can be used. A metal lithium sheet is used as the negative electrode and a sample electrode is used as the positive electrode to assemble a button battery. Under the conditions of 23°C±2°C, the button battery is placed on a battery tester or other test equipment of equivalent performance, and the charge and discharge rate of 0.1C is used to obtain the button capacity. The capacity is then divided by the mass of the electrode active material to obtain the gram capacity parameter. Specifically,

[0193] The positive electrode active material, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an appropriate amount of solvent N-methylpyrrolidone (NMP) in a mass ratio of 92:3:5 to form a uniform positive electrode slurry; the positive electrode slurry is evenly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, the positive electrode sheet is obtained.

[0194] A button cell was assembled in an argon-protected glove box using a metallic lithium sheet as the counter electrode and a few drops of electrolyte. The electrolyte consisted of an organic solvent (ethylene carbonate (EC) and diethyl carbonate (DMC)) in a 1:1 volume ratio, and an electrolyte salt (1 mol / L lithium hexafluorophosphate).

[0195] The button cell was charged and discharged at a low rate of 0.1C to obtain the button capacity, and then the capacity was divided by the mass of the active material of the electrode to obtain the gram capacity parameter.

[0196] In some embodiments, the resistivity of the lithium-containing transition metal oxide powder is 100 Ω*cm to 2000 Ω*cm, and optionally 500 Ω*cm to 1680 Ω*cm.

[0197] Illustratively, the powder resistivity of the lithium-containing transition metal oxide is 100Ω*cm, 200Ω*cm, 300Ω*cm, 400Ω*cm, 500Ω*cm, 1000Ω*cm, 1500Ω*cm, 2000Ω*cm, or a range consisting of any two of the above values.

[0198] When the resistivity of the powder containing lithium transition metal oxide is within the above range, especially when the lithium transition metal oxide includes a coating layer, the coating layer may slightly deteriorate the electron transmission ability, causing the powder resistivity to slightly increase, thereby increasing the resistance of the positive electrode sheet, reducing the risk of thermal runaway, and effectively improving the reliability of lithium-ion batteries.

[0199] In the embodiment of the present application, the discharge capacity in grams of lithium-containing transition metal oxides has a meaning well known in the art. The testing of lithium-containing transition metal oxides can be carried out using equipment and methods well known in the art. For example, reference can be made to GB / T30835-2014 and testing can be carried out using a PRCD1100 powder resistivity meter.

[0200] In some embodiments, the resistance of the positive electrode plate is 0.3Ω to 1.0Ω, optionally 0.3Ω to 0.95Ω, such as 0.3Ω, 0.4Ω, 0.5Ω, 0.6Ω, 0.7Ω, 0.8Ω, 0.9Ω, 1.0Ω or a range consisting of any two of the above values.

[0201] In the embodiments of the present application, the resistance of the positive electrode sheet has a meaning well known in the art. The resistance of the positive electrode sheet can be tested using equipment and methods well known in the art. For example, small discs with a diameter of 10 mm are cut from the left, middle, and right sides of the positive electrode sheet. Turn on the indicator light of the Yuanneng Technology electrode sheet resistor meter, place them in the appropriate position of the "probe" of the membrane resistor meter, click the "Start" button, wait for the reading to stabilize, and then read it. Each small disc is tested in two positions, and the average of the six measurements is finally calculated, which is the resistance of the electrode sheet.

[0202] In some embodiments, the tap density of the lithium-containing transition metal oxide is 1.5 g / cm 3 Up to 3.0g / cm 3 , optional 2.4g / cm 3 Up to 2.55g / cm 3 , for example 1.5g / cm 3 , 1.8g / cm 3 , 2.0g / cm 3 , 2.2g / cm3 , 2.5g / cm 3 , 2.8g / cm 3 , 3.0g / cm 3 When the tap density of the lithium-containing transition metal oxide is within the above range, it is beneficial to improve the energy density of the lithium-ion battery.

[0203] In the embodiments of this application, the tap density of a material is a term generally known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using a powder tap density tester, as described in GB / T 5162-2006. A Dandong Better BT-301 can be used as the tester.

[0204] In some embodiments, a lithium-containing transition metal oxide is dissolved in deionized water to form a lithium-containing transition metal oxide solution, wherein the mass content of the lithium-containing transition metal oxide in the lithium-containing transition metal oxide solution is 10%, and the pH value of the lithium-containing transition metal oxide solution is 11 to 13, and can be optionally 11.5 to 12.5, for example, 11, 11.2, 11.3, 11.5, 11.6, 11.7, 11.8, 11.9, 12, 12.2, 12.3, 12.4, 12.5, 12.7, 12.9, 13 or a range consisting of any two of the above values.

[0205] Specifically, a lithium-containing transition metal oxide and deionized water were mixed in a container at a fixed ratio of 1:9 to form a lithium-containing transition metal oxide solution. The container was sealed and stirred on a magnetic stirrer for 30 minutes. After stirring, the container was placed in a 25°C water bath and allowed to stand for 1.5 hours before testing. A pH composite electrode was inserted into the lithium-containing transition metal oxide solution to form an electrochemical cell, and the solution pH was measured.

[0206] Preparation method of lithium-containing transition metal oxide

[0207] In a second aspect, an embodiment of the present application provides a method for preparing a lithium-containing transition metal oxide. The method can be used to prepare the lithium-containing transition metal oxide according to any embodiment of the first aspect of the present application.

[0208] The preparation method comprises:

[0209] Step S100, providing a transition metal precursor;

[0210] Step S200, mixing a transition metal precursor, a lithium source, and an L source, and calcining to obtain a lithium-containing transition metal oxide, wherein the L ions in the L source include cations corresponding to one or more elements selected from the group consisting of Na, K, Mg, Ca, Sr, Bi, Cu, and Y;

[0211] The lithium-containing transition metal oxide includes secondary particles, and the secondary particles include a plurality of primary particles.

[0212] Lithium-containing transition metal oxides satisfy: M i / M0 is 30% to 100%,

[0213] in,

[0214] Based on the mass of the secondary particles, the mass content of the L element located in the secondary particles is M0;

[0215] Based on the mass of the secondary particles, the doping content of the L element in the secondary particles is M i .

[0216] According to the method implemented in the present application, the L element in the L source can diffuse into the crystal structure of the lithium-containing transition metal oxide, and the L cation can enter the lithium layer to play a supporting role, which can improve the crystal structure stability of the lithium-containing transition metal oxide, thereby improving the cycle stability of the lithium-containing transition metal oxide.

[0217] [Step S100]

[0218] The metal precursor can be prepared by co-precipitation method, and of course other methods can also be used to prepare the metal precursor.

[0219] In some implementations, step S100 may include:

[0220] The transition metal precursor includes one or more of a nickel source, a cobalt source and a manganese source. At least one of the nickel source, cobalt source and manganese source is added to a solvent to mix into a metal salt solution. The metal salt solution is mixed with a precipitant and then precipitated, and then washed and dried to obtain a metal precursor.

[0221] For example, a nickel source, a cobalt source, and a manganese source are added to a solvent to form a metal salt solution. The metal salt solution is mixed with a precipitant and allowed to precipitate for 8 to 12 hours, followed by aging for 3.5 to 6 hours to allow primary particle growth. The product is then washed with deionized water three to five times, dried in a blast dryer, and vacuum-dried at 90°C to 110°C for 10 to 12 hours to obtain a metal precursor.

[0222] The stoichiometric ratio of the nickel source, the cobalt source, and the manganese source can be calculated based on the stoichiometric ratio of the desired product.

[0223] In some embodiments, the nickel source may include at least one of nickel sulfate, nickel nitrate, nickel oxalate, nickel chloride, and nickel acetate.

[0224] In some embodiments, the cobalt source may include at least one of cobalt sulfate, cobalt nitrate, cobalt oxalate, cobalt chloride, and cobalt acetate.

[0225] In some embodiments, the manganese source may include at least one of manganese sulfate, manganese nitrate, manganese oxalate, manganese chloride, and manganese acetate.

[0226] The compound form of the doped metal source can refer to the nickel source and will not be described in detail here.

[0227] In some embodiments, the solvent may include at least one of deionized water and alcohols, for example, the solvent may be water or ethanol, etc. Optionally, the solvent is deionized water.

[0228] In some embodiments, the precipitant may include at least one of sodium carbonate, sodium hydroxide, potassium carbonate, and potassium hydroxide, and may be sodium carbonate.

[0229] [Step S200]

[0230] In step S200, a transition metal precursor, a lithium source, and an L source are mixed to form an intermediate. Furthermore, an M source may be added to the intermediate. For example, at least the metal precursor, the lithium source, the L source, and the M source are mixed and ground to form an intermediate, wherein the M source includes one or more of a Zr source, an Al source, a Cu source, a Mg source, a Zn source, a Ti source, a V source, a Ga source, a Sn source, a Ge source, a Ta source, a Mo source, a W source, a Nb source, a Sb source, and a La source.

[0231] Alternatively, the M source can be added after the first calcination treatment and subjected to a second calcination treatment together with other raw materials.

[0232] In some embodiments, the M source may include at least one of sulfate, nitrate, oxalate, chloride, and acetate.

[0233] The stoichiometric ratios of the metal precursor, lithium source, L source, and M source can be calculated based on the stoichiometric ratios of the desired products.

[0234] In some embodiments, the lithium source may include at least one of an inorganic lithium source and an organic lithium source. If the lithium source includes phosphorus, it may also serve as a phosphorus source. For example, the inorganic lithium source may include at least one of lithium carbonate, lithium sulfate, lithium hydroxide, lithium dihydrogen phosphate, and lithium phosphate. For example, the organic lithium source may include at least one of lithium acetate, lithium oxalate, and lithium citrate.

[0235] In some embodiments, the L source may include at least one of a sodium source, a potassium source, a magnesium source, a calcium source, a copper source, a strontium source, a bismuth source, and a yttrium source. Alternatively, the L source may include at least one of a sodium source, a potassium source, and a calcium source. The L source has a relatively low melting point and can melt in the early stage of the calcination process. The molten L source provides a liquid phase environment. Compared with the traditional solid phase interface, the liquid phase interface has a stronger transmission and diffusion capacity. The molten ions quickly diffuse through the precursor framework into the lithium layer lattice, which is conducive to the uniform diffusion of L cations into the lithium layer, reducing the lattice distortion caused by the mixed arrangement of lithium and nickel, improving the orderliness of the lattice arrangement, increasing the lattice spacing, and improving the stability of the lithium layer.

[0236] In some embodiments, the L source may further include acid ions, and the acid ions include one or more of inorganic acid ions and organic acid ions.

[0237] Exemplarily, the inorganic acid radical ions include one or more of hydroxide, carbonate, sulfate, nitrate, and chloride ions. For example, the L source includes sodium ions, and the main substance of the L source may include one or more of sodium hydroxide, sodium carbonate, sodium sulfate, sodium nitrate, or sodium chloride; for example, the L source may include a mixture of sodium hydroxide and sodium carbonate, and for another example, the coating layer may include sodium hydroxide. For another example, the L source includes potassium ions, and the main substance of the L source may include one or more of potassium hydroxide, potassium carbonate, potassium sulfate, potassium nitrate, or potassium chloride. For another example, the L source includes calcium ions, and the main substance of the L source may include one or more of calcium hydroxide, calcium carbonate, calcium sulfate, calcium nitrate, or calcium chloride.

[0238] For example, the organic acid radical ions include one or more of acetate, formate, oxalate, and sulfonate. For example, if the L source includes sodium ions, the main substance of the L source may include one or more of sodium acetate, sodium formate, sodium oxalate, or sodium sulfonate. For another example, if the L source includes potassium ions, the main substance of the L source may include one or more of potassium acetate, potassium formate, potassium oxalate, or potassium sulfonate. For another example, if the L source includes calcium ions, the main substance of the L source may include one or more of calcium acetate, calcium formate, calcium oxalate, or calcium sulfonate.

[0239] In some embodiments, the molar ratio of the lithium source to the L source is 15 to 25, for example, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, or a range consisting of any two of the foregoing values. When the lithium source and the L source meet the above molar ratio, it is beneficial for the L source to be more doped into the lithium layer.

[0240] In some embodiments, the intermediate is calcined above the melting point of the L source to obtain a lithium-containing transition metal oxide.

[0241] When the temperature of the sodium source is high, melting basically does not occur during the calcination process. The calcination process is mainly solid-state sintering. Sodium ions diffuse in the solid state, and the diffusion resistance is large. The content diffused into the positive electrode active material is relatively small, especially the content in the lithium layer is relatively small.

[0242] According to the method of the embodiment of the present application, the calcination treatment is carried out above the melting point of the L source. The L source can melt during the calcination treatment and appear in the liquid phase. The calcination treatment is mainly solid-liquid phase sintering. The L cations in the liquid phase L source are easy to diffuse into the crystal structure of the lithium-containing transition metal oxide, and the L cations can enter the lithium layer to play a supporting role, which can improve the intrinsic lithium-nickel mixing phenomenon in the lithium-containing transition metal oxide, thereby improving the crystal structure stability of the lithium-containing transition metal oxide, thereby improving the cycle stability of the lithium-containing transition metal oxide.

[0243] The calcination treatment process of the embodiment of the present application can adopt a single calcination, that is, the L source, lithium source and metal precursor are sintered simultaneously. In this case, both lithium ions and L cations can diffuse into the lattice structure. The L cations mainly diffuse in the liquid-solid state, and their diffusion resistance is relatively small. They can diffuse more quickly into the lithium layer to occupy sites and can be evenly distributed in the lithium layer; lithium ions mainly diffuse in the solid-solid state. Due to their small ionic radius, they can diffuse into the lithium layer in large quantities, occupy sites in the lithium layer, and increase the gram capacity of the positive electrode active material.

[0244] Of course, the calcination process can also adopt multi-stage calcination, such as two-stage calcination, which can specifically include a first calcination treatment and a second calcination treatment. The temperature of the first calcination treatment is greater than or equal to the melting point of the L source. During the first calcination treatment, the L source melts, and the L cations can preferentially diffuse into the lattice structure and occupy the sites of the lithium layer; during the second calcination treatment, the lithium ions in the lithium source diffuse and diffuse into the lattice structure, thereby forming the desired material.

[0245] Exemplarily, step S200 may include:

[0246] Step S210, mixing a transition metal precursor, a lithium source, and an L source to form an intermediate;

[0247] Step S220, performing a first calcination treatment on the intermediate to melt the L source in the intermediate into a liquid phase, wherein the temperature of the first calcination treatment is greater than or equal to the melting point of the L source;

[0248] In step S230 , the intermediate product after the first calcination treatment is subjected to a second calcination treatment to obtain a transition metal oxide, wherein the temperature of the second calcination treatment is higher than the temperature of the first calcination treatment.

[0249] The temperature of the first calcination treatment is greater than or equal to the melting point of the L source. During the first calcination treatment, the L source can melt to form a liquid phase. The diffusion resistance of the L cations in the L source in the liquid phase is relatively small, which is conducive to the rapid and uniform diffusion of the L cations into the crystal structure of the positive electrode active material, thereby playing a role in supporting the lithium layer.

[0250] In some embodiments, the temperature of the first calcination treatment is 450°C to 600°C. For example, the temperature of the first calcination treatment may be 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, or a range consisting of any two of the foregoing values. In this case, the melting point of the L source is less than or equal to the temperature of the first calcination treatment. Specifically, when the first calcination treatment temperature is 600°C, the melting point of the L source may be ≤600°C. For example, when the first calcination treatment temperature is 450°C, the melting point of the L source may be ≤450°C.

[0251] In some embodiments, the melting point of the L source is 200°C to 600°C, and may be 210°C to 400°C, such as 200°C, 210°C, 250°C, 280°C, 300°C, 320°C, 350°C, 380°C, 400°C, 420°C, 430°C, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, or a range consisting of any two of the foregoing values. The L source has a relatively low melting point and can be melted during the first calcination process, which is conducive to diffusion in a liquid phase, allowing the L element to be uniformly dispersed in the lithium layer and provide a stable support.

[0252] In some embodiments, the first calcination treatment time is 5 hours to 10 hours. For example, the first calcination treatment time can be 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, or a range consisting of any two of the above values.

[0253] Illustratively, the intermediate is heated from room temperature to 450° C. to 600° C. at a heating rate of 1° C. / min to 3° C. / min, and calcined for 5 h to 10 h.

[0254] The temperature of the second calcination treatment is higher than that of the first calcination treatment. During the second calcination treatment, the L cations further diffuse into the lattice structure. Due to the smaller ionic radius of lithium ions, lithium ions can diffuse into the lattice structure quickly, thereby obtaining the desired positive electrode active material. Furthermore, the positive electrode active material can be further pulverized to obtain the desired final product.

[0255] In some embodiments, the temperature of the second calcination treatment is 700° C. to 750° C. For example, the temperature of the second calcination treatment can be 700° C., 705° C., 710° C., 715° C., 720° C., 725° C., 730° C., 735° C., 740° C., 745° C., 750° C., or a range consisting of any two of the foregoing values.

[0256] In some embodiments, the second calcination treatment time is 10 hours to 12 hours. For example, the second calcination treatment time can be 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, or a range consisting of any two of the above values.

[0257] Illustratively, the intermediate is heated from the temperature of the first calcination treatment to 700° C. to 750° C. at a heating rate of 1° C. / min to 3° C. / min, and calcined for 10 to 12 hours.

[0258] Positive electrode

[0259] In a third aspect, an embodiment of the present application proposes a positive electrode plate, which includes a positive electrode collector and a positive electrode film layer arranged on at least one side of the positive electrode collector, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing transition metal oxide as in any embodiment of the first aspect of the present application, or a lithium-containing transition metal oxide prepared by the method of any embodiment of the second aspect of the present application.

[0260] In some embodiments, the weight percentage of the lithium-containing transition metal oxide, based on the total weight of the positive electrode film layer, can be 85 wt % to 95 wt %, for example, 85 wt %, 88 wt %, 90 wt %, 92 wt %, 95 wt %, or a range consisting of any two of these values. A lithium-containing transition metal oxide in this weight range can provide the positive electrode sheet with a higher capacity and better cycling performance.

[0261] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The present embodiments do not particularly limit the type of the positive electrode conductive agent. By way of example, the positive electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent based on the total mass of the positive electrode film layer is ≤5%.

[0262] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. The embodiments of the present application do not particularly limit the type of positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin. In some embodiments, the mass percentage of the positive electrode binder is ≤5% based on the total mass of the positive electrode film layer.

[0263] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer may include at least one of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0264] The positive electrode film layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0265] lithium-ion batteries

[0266] In a fourth aspect, an embodiment of the present application further provides a lithium-ion battery.

[0267] Lithium-ion batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged after discharge to reactivate the active materials and continue to be used. Typically, a lithium-ion battery consists of an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. The separator is placed between the positive and negative electrodes to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0268] In some embodiments, the lithium-ion battery comprises the positive electrode sheet of any one of the third aspects of the embodiments of the present application. Thus, the lithium-ion battery of the embodiments of the present application can effectively improve the cycle performance of the lithium-ion battery.

[0269] [Negative electrode]

[0270] In some embodiments, the lithium-ion battery further includes a negative electrode.

[0271] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and comprising a negative electrode active material. For example, the negative electrode current collector has two opposing surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0272] The negative electrode active material may be any of those known in the art for lithium-ion batteries. For example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include at least one of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxide, and tin alloys.

[0273] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present embodiments do not particularly limit the type of negative electrode conductive agent. For example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the negative electrode conductive agent based on the total weight of the negative electrode film layer is ≤5%.

[0274] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. The present application embodiment does not particularly limit the type of negative electrode binder. As an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide PAM, polyvinyl alcohol PVA, sodium alginate SA, and carboxymethyl chitosan CMCS. In some embodiments, the mass percentage of the negative electrode binder based on the total weight of the negative electrode film layer is ≤5%.

[0275] In some embodiments, the negative electrode film layer may optionally include other additives. For example, these additives may include thickeners, such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, and the like. In some embodiments, the weight percentage of these additives is ≤ 2% based on the total weight of the negative electrode film layer.

[0276] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Copper foil may be used as an example of a metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal material may include at least one of copper, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0277] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0278] The negative electrode sheet does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the embodiments of the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0279] [Electrolyte]

[0280] In some embodiments, the lithium-ion battery further includes an electrolyte.

[0281] During the charge and discharge process of a lithium-ion battery, active ions are embedded and released back and forth between the positive and negative electrodes. The electrolyte conducts the active ions between the positive and negative electrodes. The present application does not impose any particular restrictions on the type of electrolyte, and the electrolyte can be selected based on actual needs.

[0282] The electrolyte solution includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not particularly limited and can be selected according to actual needs.

[0283] As an example, the electrolyte salt may include, but is not limited to, at least one of lithium hexafluorophosphate LiPF6, lithium tetrafluoroborate LiBF4, lithium perchlorate LiClO4, lithium hexafluoroarsenate LiAsF6, lithium bisfluorosulfonyl imide LiFSI, lithium bistrifluoromethanesulfonyl imide LiTFSI, lithium trifluoromethanesulfonate LiTFS, lithium difluorooxalatoborate LiDFOB, lithium bisoxalatoborate LiBOB, lithium difluorophosphate LiPO2F2, lithium difluorobisoxalatophosphate LiDFOP, and lithium tetrafluorooxalatophosphate LiTFOP.

[0284] As an example, the solvent may include, but is not limited to, at least one of 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, methyl butyrate MB, ethyl butyrate EB, 1,4-butyrolactone GBL, sulfolane SF, dimethyl sulfone MSM, methyl ethyl sulfone EMS, and diethyl sulfone ESE.

[0285] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or 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 power performance.

[0286] [Isolation film]

[0287] In some embodiments, the lithium-ion battery further includes a separator.

[0288] In some embodiments, the lithium-ion battery further includes a separator. The embodiments of the present application have no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0289] In some embodiments, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0290] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly through a winding process and / or a lamination process.

[0291] In some embodiments, the lithium-ion battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0292] In some embodiments, the outer packaging of the lithium-ion battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the lithium-ion battery can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0293] The present invention has no particular restrictions on the shape of the lithium-ion battery, which can be cylindrical, square, or any other shape. FIG1 shows a lithium-ion battery 5 having a square structure as an example.

[0294] In some embodiments, as shown in FIG2 , 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 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process and / or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the lithium-ion battery 5 can be one or more, which can be adjusted according to demand.

[0295] The preparation method of the lithium-ion battery of the embodiments of the present application is well known. In some embodiments, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a lithium-ion battery. As an example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly through a winding process and / or a lamination process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. The lithium-ion battery is obtained through vacuum packaging, static standing, formation, and shaping processes.

[0296] In some embodiments of the present invention, the lithium-ion batteries according to the present invention can be assembled into a battery module. The number of lithium-ion batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0297] Figure 3 is a schematic diagram of an exemplary battery module 4. As shown in Figure 3 , within the battery module 4, multiple lithium-ion batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple lithium-ion batteries 5 may be secured using fasteners.

[0298] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of lithium-ion batteries 5 are received in the receiving space.

[0299] In some embodiments, the battery modules can be assembled into a battery pack, and the number of battery modules in the battery pack can be adjusted according to the application and capacity of the battery pack. Lithium-ion batteries, battery modules, and battery packs can all be used as examples of battery devices.

[0300] Figures 4 and 5 are schematic diagrams of an exemplary battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 covers the lower case 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0301] Electrical devices

[0302] A fifth aspect of the embodiments of the present application provides an electrical device, which includes at least one of the lithium-ion batteries, battery modules, or battery packs of the embodiments of the present application. The lithium-ion battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may 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, a satellite, an energy storage system, etc.

[0303] Electrical devices can select lithium-ion batteries, battery modules or battery packs according to their usage requirements.

[0304] FIG6 is a schematic diagram of an exemplary electric device 6. The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device 6, a battery pack or battery module may be used.

[0305] As another example, the electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a lithium-ion battery as a power source.

[0306] Example

[0307] The following examples describe the disclosure of the present invention in more detail. These examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present invention will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0308] Example 1-1 Preparation of lithium-containing transition metal oxide

[0309] First, nickel acetate, cobalt acetate, and manganese acetate were added to deionized water in a stoichiometric ratio of 92:7:1 and stirred to obtain a metal salt solution. Sodium carbonate solution was then poured into the metal salt solution and the reaction continued for 9 hours. The mixture was then allowed to stand for 4 hours to allow for primary particle growth. The product was then washed three times with deionized water, dried in a blast dryer, and vacuum-dried at 100°C for 12 hours. The dried solid was collected to form the transition metal precursor.

[0310] The transition metal precursor, lithium hydroxide and sodium acetate are mixed evenly in a molar ratio of 1:0.9975:0.0525 (after conversion, the molar ratio of lithium hydroxide to sodium acetate is 19), and ground into a solid powder. Excessive addition of lithium hydroxide can make up for the loss of lithium during high-temperature calcination. The fully ground solid powder is transferred to a crucible and placed in a programmed temperature muffle furnace for calcination. The calcination procedure is: pre-calcination from room temperature to 500°C at a heating rate of 3°C / min for 5h, then pre-calcined at a high temperature of 700°C at a heating rate of 3°C / min for 12h, then cooled to room temperature and collected. The lithium-containing transition metal oxide is used as the positive electrode active material of the lithium-ion battery.

[0311] Example 1-2 to Example 1-4

[0312] The positive electrode active material was prepared by a method similar to that of Example 1-1. The difference from Example 1-1 was that the material of the sodium source was adjusted.

[0313] Wherein, in Examples 1-4, a mixed sodium salt is used, and the mixed sodium salt includes sodium hydroxide and sodium carbonate in a mass ratio of 96:4.

[0314] Example 1-5 and Example 1-6

[0315] The positive electrode active material was prepared by a method similar to that of Example 1-1. The difference from Example 1-1 was that the sodium source was changed to a calcium source or a magnesium source. Example 1-5 used a calcium source, and Example 1-6 used a magnesium source.

[0316] Example 1-7 to Example 1-10

[0317] A positive electrode active material was prepared using a method similar to that of Example 1-1, except that the content of the sodium source was adjusted.

[0318] Examples 1-11

[0319] A positive electrode active material was prepared using a method similar to that of Example 1-1. The difference from Example 1-1 was that the doping element Mg was added. The steps for preparing the positive electrode active material were as follows:

[0320] First, nickel acetate, cobalt acetate, and manganese acetate were added to deionized water in a stoichiometric ratio of 92:6:1 and stirred thoroughly to obtain a metal salt solution. Sodium carbonate solution was then poured into the metal salt solution and the reaction continued for 9 hours. The mixture was then allowed to stand for 4 hours to allow for primary particle growth. The product was then washed three times with deionized water, dried in a blast dryer, and vacuum-dried at 100°C for 12 hours. The dried solid was collected to form the transition metal precursor.

[0321] A transition metal precursor, lithium hydroxide, and sodium acetate were mixed uniformly in a molar ratio of 1:0.9975:0.0525 and ground into a solid powder. Excess lithium hydroxide was added to compensate for lithium loss during high-temperature calcination. The thoroughly ground solid powder was transferred to a crucible and calcined in a programmed temperature muffle furnace. The calcination procedure was as follows: pre-calcination from room temperature to 500°C at a heating rate of 3°C / min for 5 hours; magnesium acetate was added to the system, and the temperature was then increased to 700°C at a heating rate of 3°C / min for 12 hours. The positive electrode active material was then cooled to room temperature and collected.

[0322] Examples 1-12

[0323] The positive electrode active material was prepared by a method similar to that of Example 1-1. The difference from Example 1-1 is that the preparation steps of the positive electrode active material are as follows:

[0324] First, nickel acetate, cobalt acetate, and manganese acetate were added to deionized water in a stoichiometric ratio of 94:5:1 and stirred evenly to obtain a metal salt solution. Sodium carbonate solution was then poured into the metal salt solution and the reaction continued for 9 hours. The mixture was then allowed to stand for 4 hours to allow for primary particle growth. The product was then washed three times with deionized water, dried in a blast dryer, and vacuum-dried at 100°C for 12 hours. The dried solid was collected to form the metal precursor.

[0325] The metal precursor, lithium hydroxide, and sodium acetate were mixed uniformly in a molar ratio of 1:0.9975:0.0525 and ground into a solid powder. Excess lithium hydroxide was added to compensate for lithium loss during high-temperature calcination. The thoroughly ground solid powder was transferred to a crucible and calcined in a programmed temperature muffle furnace. The calcination procedure was as follows: pre-calcination from room temperature to 500°C at a heating rate of 3°C / min for 5 hours, followed by calcination at 700°C at a heating rate of 3°C / min for 12 hours. After cooling to room temperature, the positive electrode active material was collected.

[0326] Examples 1-13

[0327] The positive electrode active material was prepared by a method similar to that of Example 1-1. The difference from Example 1-1 is that the steps for preparing the positive electrode active material are as follows:

[0328] First, nickel acetate, cobalt acetate, and manganese acetate were added to deionized water in a stoichiometric ratio of 55:7:38 and stirred evenly to obtain a metal salt solution. Sodium carbonate solution was then poured into the metal salt solution and the reaction continued for 9 hours. The mixture was then allowed to stand for 4 hours to allow for primary particle growth. The product was then washed three times with deionized water, dried in a blast dryer, and vacuum-dried at 100°C for 12 hours. The dried solid was collected to form the metal precursor.

[0329] The metal precursor, lithium hydroxide, and sodium acetate were mixed uniformly in a molar ratio of 1:0.9975:0.0525 and ground into a solid powder. Excess lithium hydroxide was added to compensate for lithium loss during high-temperature calcination. The thoroughly ground solid powder was transferred to a crucible and calcined in a programmed temperature muffle furnace. The calcination procedure was as follows: pre-calcination from room temperature to 500°C at a heating rate of 3°C / min for 5 hours, followed by calcination at 700°C at a heating rate of 3°C / min for 12 hours. After cooling to room temperature, the positive electrode active material was collected.

[0330] Examples 1-14

[0331] A positive electrode active material was prepared using a method similar to that of Example 1-1. The difference from Example 1-1 was that the calcination process was adjusted and a single calcination process was adopted. The steps for preparing the positive electrode active material were as follows:

[0332] First, nickel acetate, cobalt acetate, and manganese acetate were added to deionized water in a stoichiometric ratio of 92:6:1 and stirred evenly to obtain a metal salt solution. Sodium carbonate solution was then poured into the metal salt solution and the reaction continued for 9 hours. The mixture was then allowed to stand for 4 hours to allow for primary particle growth. The product was then washed three times with deionized water, dried in a blast dryer, and vacuum-dried at 100°C for 12 hours. The dried solid was collected to form the metal precursor.

[0333] The metal precursor, lithium hydroxide, and sodium acetate were mixed uniformly in a molar ratio of 1:0.9975:0.0525 and ground into a solid powder. Excess lithium hydroxide was added to compensate for lithium loss during high-temperature calcination. The thoroughly ground solid powder was transferred to a crucible and calcined in a temperature-programmed muffle furnace. The calcination procedure was as follows: aluminum acetate was added to the system, and the temperature was then increased from room temperature to 700°C at a rate of 3°C / min for 12 hours. The positive electrode active material was then cooled to room temperature and collected.

[0334] Examples 1-15

[0335] The positive electrode active material was prepared by a method similar to that of Example 1-1. The difference from Example 1-1 is that the steps for preparing the positive electrode active material are as follows:

[0336] First, nickel acetate, cobalt acetate, and manganese acetate were added to deionized water in a stoichiometric ratio of 92:7:1 and stirred to obtain a metal salt solution. Sodium carbonate solution was then poured into the metal salt solution and the reaction continued for 9 hours. The mixture was then allowed to stand for 4 hours to allow for primary particle growth. The product was then washed three times with deionized water, dried in a blast dryer, and vacuum-dried at 100°C for 12 hours. The dried solid was collected to form the transition metal precursor.

[0337] The transition metal precursor, lithium hydroxide and sodium acetate are mixed evenly in a molar ratio of 1:0.9975:0.0525 (after conversion, the molar ratio of lithium hydroxide to sodium acetate is 19), and ground into a solid powder. Excessive addition of lithium hydroxide can make up for the loss of lithium during high-temperature calcination. The fully ground solid powder is transferred to a crucible and placed in a programmed temperature muffle furnace for calcination. The calcination procedure is: pre-calcination from room temperature to 500°C at a heating rate of 3°C / min for 5h, then pre-calcination at a high temperature of 700°C at a heating rate of 3°C / min for 12h, then cooled to room temperature and collected. The lithium-containing transition metal oxide is washed with water to remove the surface coating layer and dried to obtain the final product. It is used as the positive electrode active material for lithium-ion batteries.

[0338] Comparative Example 1-1

[0339] A positive electrode active material was prepared using a method similar to that of Example 1-1. The difference from Example 1-1 was that no sodium source was added. The steps for preparing the positive electrode active material were as follows:

[0340] First, nickel acetate, cobalt acetate, and manganese acetate were added to deionized water in a stoichiometric ratio of 92:7:1 and stirred evenly to obtain a metal salt solution. Sodium carbonate solution was then poured into the metal salt solution and the reaction continued for 9 hours. The mixture was then allowed to stand for 4 hours to allow for primary particle growth. The product was then washed three times with deionized water, dried in a blast dryer, and vacuum-dried at 100°C for 12 hours. The dried solid was collected to form the metal precursor.

[0341] The metal precursor and lithium hydroxide were mixed uniformly in a molar ratio of 1:0.9975 and ground into a solid powder. Excess lithium hydroxide was added to compensate for lithium loss during high-temperature calcination. The thoroughly ground solid powder was transferred to a crucible and calcined in a programmed temperature muffle furnace. The calcination procedure was as follows: pre-calcination from room temperature to 500°C at a heating rate of 3°C / min for 5 hours, then calcination at 700°C at a heating rate of 3°C / min for 12 hours. After cooling to room temperature, the positive electrode active material was collected.

[0342] Comparative Example 1-2

[0343] A positive electrode active material was prepared using a method similar to that of Example 1-1. The difference from Example 1-1 was that the sodium source addition process was adjusted. The steps for preparing the positive electrode active material were as follows:

[0344] First, nickel acetate, cobalt acetate, and manganese acetate were added to deionized water in a stoichiometric ratio of 92:7:1 and stirred evenly to obtain a metal salt solution. Sodium carbonate solution was then poured into the metal salt solution and the reaction continued for 9 hours. The mixture was then allowed to stand for 4 hours to allow for primary particle growth. The product was then washed three times with deionized water, dried in a blast dryer, and vacuum-dried at 100°C for 12 hours. The dried solid was collected to form the metal precursor.

[0345] The metal precursor, lithium hydroxide, and sodium carbonate (melting point 851°C) were mixed evenly in a molar ratio of 1:0.9975:0.0525 and ground into a solid powder. Excessive addition of lithium hydroxide can 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. The calcination procedure was as follows: pre-calcination from room temperature to 600°C at a heating rate of 3°C / min for 6 hours, then calcination at a high temperature of 700°C at a heating rate of 3°C / min for 12 hours, and then the positive electrode active material was collected after cooling to room temperature.

[0346] Preparation of Lithium-ion Batteries in Examples and Comparative Examples

[0347] 1. Preparation of positive electrode sheet

[0348] Aluminum foil was used as the positive electrode current collector.

[0349] The positive electrode active material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) were thoroughly stirred and mixed in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a weight ratio of 92:3:5 to form a uniform positive electrode slurry. The positive electrode slurry was evenly coated on the surface of the positive electrode current collector aluminum foil, dried, and cold pressed to obtain a positive electrode sheet. The positive electrode active materials used were those of Examples 1-1 to 1-11, Comparative Example 1-1, and Comparative Example 1-2, respectively.

[0350] 2. Preparation of negative electrode sheet

[0351] Copper foil was used as the negative electrode current collector.

[0352] The negative electrode active material artificial graphite, the binder styrene-butadiene rubber SBR, the thickener sodium carboxymethyl cellulose CMC-Na, and the conductive agent carbon black SuperP are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry; the negative electrode slurry is evenly coated on the surface of the negative electrode current collector copper foil, and after drying and cold pressing, the negative electrode sheet is obtained.

[0353] 3. Isolation film

[0354] A porous polyethylene (PE) film is used as the isolation membrane.

[0355] 4. Preparation of electrolyte

[0356] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate EC and diethyl carbonate DMC are mixed in a volume ratio of 1:1 to obtain an electrolyte solvent, and then lithium salt lithium hexafluorophosphate and the electrolyte solvent are mixed to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0357] 5. Preparation of lithium-ion batteries

[0358] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0359] The relevant parameters of the embodiment and comparative example are shown in Table 1 and Table 2 below.

[0360] Performance Testing

[0361] 1. Cycle performance test of lithium-ion batteries

[0362] At 45°C, the lithium ion batteries prepared in the examples and comparative examples were charged at a constant current rate of 0.5C to a charge cut-off voltage of 4.25V, then charged at a constant voltage to a current of ≤0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to a discharge cut-off voltage of 2.5V, allowed to stand for 5 minutes. This constituted one charge and discharge cycle.

[0363] The battery is cycled and discharged according to this method until the battery capacity decays to 80%. The number of cycles at this point is the cycle life of the lithium-ion battery at 45°C.

[0364] Test results

[0365] The test results are shown in Table 1.

[0366] Table 1

[0367] In Table 1, Comparative Example 2-1 corresponds to a lithium ion battery, which uses the positive electrode active material corresponding to Comparative Example 1-1.

[0368] For example, Example 2-1 corresponds to a lithium-ion battery, which uses the positive electrode active material corresponding to Example 1-1.

[0369] The corresponding relationships between the lithium-ion batteries and the positive electrode active materials in other embodiments are as described above and will not be repeated here.

[0370] Figure 7 is a scanning electron microscope (SEM) image of the positive electrode active material in Comparative Example 1-1, and the overall morphology of the positive electrode active material particles is uniform; Figure 8 is a scanning electron microscope (SEM) image of the positive electrode active material in Comparative Example 1-2, and the overall morphology of the positive electrode active material particles is uniform; Figure 9 is a scanning electron microscope (SEM) image of the positive electrode active material in Example 1-1, and the overall morphology of the positive electrode active material particles is uniform. Due to the fluxing effect of the low-melting-point sodium source, the primary particle gaps of the positive electrode active material are denser and the particle crystal surface crystallinity is better.

[0371] Figures 10 and 11 are XRD patterns of the positive electrode active materials in Comparative Example 1-1, Comparative Example 1-2, and Example 1-1. It can be seen from the patterns that the peak intensity I of the positive electrode active material in Example 1-1 is higher than that of the positive electrode active materials in Comparative Example 1-1 and Comparative Example 1-2. (003) With peak intensity I (104) The ratio is larger and has better crystallinity.

[0372] Figures 12 and 13 are schematic diagrams of the nickel element distribution of the positive electrode active material in Comparative Example 1-1; Figures 14 and 15 are schematic diagrams of the nickel element and sodium element distribution of the primary particles of the positive electrode active material in Example 1-1; the sodium ions of the positive electrode active material in Example 1-1 are mainly distributed inside the primary particles, and some sodium ions are also distributed in the coating layer. The thickness of the coating layer in Example 1-1 is about 0.5nm to 6.0nm; the mass concentration of sodium ions located in the peripheral area of ​​the primary particles is higher, and the mass concentration of sodium ions located in the central area of ​​the primary particles is lower, and the mass content of sodium ions located in the central area is 300ppm to 3000ppm.

[0373] As can be seen from Table 1, the positive electrode active material in Comparative Example 1-1 is not doped with sodium ions, and its cycle performance is relatively poor; Comparative Example 1-2 is doped with sodium ions relative to Comparative Example 1-1, but because the melting point of the sodium source is higher than the calcination temperature, the sodium source basically does not melt during the doping process, and the sodium ions diffuse in the solid-solid phase, the diffusion resistance is relatively large, and the content doped into the primary particles is relatively small, which can improve the cycle performance of the lithium-ion battery to a certain extent, but the improvement effect is limited.

[0374] In contrast, Examples 2-1 to 2-14 use a sodium source with a lower melting point. Different types of low-melting-point sodium sources are used. The sodium source melts during the calcination process, and the diffusion of sodium ions occurs mainly in the liquid-solid phase, which results in a faster diffusion. The content of sodium ions doped into the primary particles is relatively high, and the dispersion in the positive electrode active material is more uniform, and the distribution in the lithium layer is more uniform. Combined with the SEM images, it can be seen that the crystallinity of the material is better. (003) / I (104)The improvement reduces the mixing of lithium and nickel, and the cycle performance is significantly improved. Replacing the sodium source in the embodiment with a low-melting-point calcium source, magnesium source, etc. can also allow calcium ions and magnesium ions to diffuse in the liquid phase and enter the lithium layer, reducing the mixing of lithium and nickel and significantly improving the cycle performance.

[0375] Furthermore, this application is applicable to a variety of lithium-containing transition metal oxides, particularly those with relatively high nickel content. While increasing nickel content increases the specific capacity of the positive electrode active material, the higher nickel content increases the degree of lithium-nickel intermixing, resulting in relatively poor cycling performance of the lithium-ion battery. However, the introduction of the element L into the positive electrode active material can improve the cycling performance of the lithium-ion battery to a certain extent. For example, when the molar content of nickel relative to the total molar amount of transition metal elements is greater than or equal to 80%, lithium-nickel intermixing can be more effectively reduced, improving the cycling performance of the lithium-ion battery.

[0376] The lithium-containing transition metal oxide may further include a doping element M, which can also improve the cycle performance of the lithium-ion battery to a certain extent.

[0377] The embodiments of the present application can adjust the degree of improvement in the cycle performance of the lithium-ion battery by adjusting the type and content of the L source, the amount of nickel source added, the calcination process, etc., and can adjust the powder resistivity, gram capacity, tap density, etc. of the positive electrode active material. Compared with the comparative example, the tap density of the embodiment is improved.

[0378] The test results are shown in Table 2.

[0379] Table 2

[0380] As shown in Table 2, by adjusting the type of L source, the gram capacity and tap density of the positive electrode active material can be adjusted to a certain extent. For example, when a sodium source is used as the L source, the powder resistivity of the positive electrode active material is within an appropriate range, which helps increase the resistance of the positive electrode sheet, reduce the risk of thermal runaway, and improve the reliability of the lithium-ion battery. For example, when a magnesium source is used as the L source, the tap density of the positive electrode active material is relatively high, which helps to improve the energy density of the lithium-ion battery.

[0381] In the embodiment of the present application, by adjusting the amount of sodium source added, when Na in the molecular formula is 0<x≤0.200, can be selected as 0.005≤x≤0.100, and can be selected as 0.05≤x≤0.100, the gram capacity of the positive electrode active material is relatively higher.

[0382] As nickel content increases, the specific capacity of the positive electrode active material increases. Introducing the L element into the positive electrode active material can improve the cycling performance of lithium-ion batteries to a certain extent, thereby achieving a balanced improvement in both cycling performance and specific capacity. The content of transition metal elements may also affect powder resistivity. For example, a decrease in cobalt content may worsen powder resistivity. Therefore, the cobalt content needs to be kept within a certain range to improve powder resistivity.

[0383] The positive electrode active materials prepared in the above embodiments have a wide particle size distribution of primary particles with an average particle size of 200 nm to 2000 nm, and a volume average particle size of secondary particles of D v50 The particle size is 4μm to 13μm, optionally 6μm to 13μm, or optionally 7.5μm to 11.5μm. By adjusting the secondary particles and primary particles, the active surface can be reduced, the interface side reactions can be reduced, and the cycle performance of the lithium-ion battery can be improved.

[0384] The pH value of the positive electrode active material prepared by the above-mentioned embodiments is suitable for lithium-ion batteries, which can reduce interfacial side reactions and improve the cycle performance of lithium-ion batteries. Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above-mentioned embodiments are not to be construed as limiting the present application, and that the embodiments may be changed, substituted, and modified without departing from the spirit, principles, and scope of the present application.

Claims

1. A lithium-ion battery comprising a positive electrode plate, the positive electrode plate comprising a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material, the positive electrode active material comprising a lithium-containing transition metal oxide, the lithium-containing transition metal oxide comprising an L element, wherein the L element comprises one or more elements selected from the group consisting of Na, K, Mg, Ca, Sr, Bi, Cu, and Y; The lithium-containing transition metal oxide includes secondary particles, and the secondary particles include a plurality of primary particles. The lithium-containing transition metal oxide satisfies: i / M0 is 30% to 100%, in, Based on the mass of the secondary particles, the mass content of the L element located in the secondary particles is M0; Based on the mass of the secondary particles, the doping content of the L element in the secondary particles is M i .

2. The lithium-ion battery according to claim 1, wherein The lithium-ion battery satisfies one or more of the following conditions: (1) Based on the mass of the secondary particles, the doping content M of the L element in the secondary particles i 300ppm to 15000ppm; (2) Based on the mass of the secondary particles, the doping content M of the L element in the secondary particles i 300ppm to 14000ppm; (3) Based on the mass of the secondary particles, the doping content M of the L element in the secondary particles i 400ppm to 5000ppm; (4) Based on the mass of the secondary particles, the doping content M of the L element in the secondary particles i 3400ppm to 4650ppm; (5) Based on the mass of the secondary particles, the mass content M0 of the L element located in the secondary particles is 300 ppm to 32000 ppm; (6) Based on the mass of the secondary particles, the mass content M0 of the L element located in the secondary particles is 800 ppm to 8000 ppm; (7)M i / M0 is 30% to 60%; (8)M i / M0 is 40% to 60%.

3. The lithium ion battery according to claim 1 or 2, wherein The primary particle includes a central region and a peripheral region surrounding the central region, wherein the peripheral region is a region extending from the outer surface of the primary particle to the interior of the primary particle within a distance of 5 nm. The average content per unit area of ​​the L element in the peripheral region is greater than the average content per unit area of ​​the L element in the central region. The mass content of the L element in the central region is greater than 0 ppm; or The mass content of the L element located in the central region is 300 ppm to 3000 ppm.

4. The lithium ion battery according to any one of claims 1 to 3, wherein There are multiple lithium layers containing lithium transition metal oxide, and the distance between two adjacent lithium layers is to or The distance between two adjacent lithium layers is to 5. The lithium ion battery according to any one of claims 1 to 4, wherein The lithium-containing transition metal oxide includes a lithium-nickel composite oxide.

6. The lithium ion battery according to any one of claims 1 to 5, wherein The lithium-containing transition metal oxide includes lithium-containing nickel-cobalt-manganese oxide.

7. The lithium ion battery according to any one of claims 1 to 6, wherein The transition metal element of the lithium-containing transition metal oxide includes nickel, and the molar content of the nickel element relative to the total molar amount of the transition metal element is 80% to 100%.

8. The lithium ion battery according to any one of claims 1 to 7, wherein The lithium-containing transition metal oxide includes a general formula of Li a L x Ni b Co c Mn d M (1-b-c-d) O e R f The material, M element includes one or more elements of Zr, Al, Cu, Mg, Zn, Ti, V, Ga, Sn, Ge, Ta, Mo, W, Nb, Sb and La, R element includes one or more elements of F, S, P and B, 0 <a<2,0<x≤0.8,0≤b≤1,0≤c≤1,0≤d≤1,0<b+c+d≤1,0<e≤2,0≤f<2。 9. The lithium ion battery according to claim 8, wherein The lithium-containing transition metal oxide satisfies one or more of the following conditions: (1)0.001≤x≤0.20； (2)0.05≤x≤0.10； (3)0.50≤b≤1.00； (4)0.80≤b≤0.99； (5) L elements include one or more elements selected from the group consisting of Na, K, and Ca.

10. The lithium ion battery according to any one of claims 1 to 9, wherein L elements include Na element.

11. The lithium ion battery according to any one of claims 1 to 10, wherein The above-mentioned metal-carrying compound Li 0.99 Na 0.01 Ni 0.92 Co 0.07 Mn 0.01 O2, Li 0.95 Na 0.05 Ni 0.92 Co 0.07 Mn 0.01 O2, Li 0.995 Na 0.005 Ni 0.92 Co 0.07 Mn 0.01 O2, Li 0.90 Na 0.1 Ni 0.92 Co 0.07 Mn 0.01 O2, Li 0.8 Na 0.2 Ni 0.92 Co 0.07 Mn 0.01 O2, Li 0.95 Na 0.05 Ni 0.92 Co 0.06 Mn 0.01 Mg 0.01 O2, Li 0.95 Na 0.05 Ni 0.92 Co 0.06 Mn 0.01 Al 0.01 O2, Li 0.95 Na 0.05 Ni 0.915 Co 0.11 Mn 0.01 Al 0.01 O2, Li 0.95 Na 0.05 Ni 0.94 Co 0.085 Mn 0.01 Al 0.01 O2, Li 0.95 Na 0.05 Ni 0.94 Co 0.05 Mn 0.01 O2, Li 0.95 Na 0.05 Ni 0.90 Co 0.08 Mn 0.01 Al 0.01 O2 and Li 0.95 Na 0.05 Ni 0.55 Co 0.07 Mn 0.38 One or more materials in O2.

12. The lithium ion battery according to any one of claims 8 to 11, wherein The lithium-containing transition metal oxide includes a general formula of Li a L x Ni b Co c Mn d M (1-b-c-d) O e R f The material, L element includes Na element, 0.001≤x≤0.20, the X-ray diffraction spectrum of the lithium-containing transition metal oxide includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the peak intensity I of the diffraction peak of the (003) crystal plane is (003) The peak intensity I of the diffraction peak of the (104) crystal plane is (104) The ratio is R1; Li a Ni b Co c Mn d M (1-b-c-d) O e R f The X-ray diffraction pattern includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the peak intensity of the diffraction peak of the (003) crystal plane is I (003) The peak intensity I of the diffraction peak of the (104) crystal plane is (104) The ratio is R0; Among them, R1 / R0 satisfies: R1 / R0 is 1 to 1.7; or R1 / R0 is 1.1 to 1.

2.

13. The lithium ion battery according to any one of claims 5 to 12, wherein The X-ray diffraction spectrum of the lithium-containing transition metal oxide includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the peak intensity I of the diffraction peak of the (003) crystal plane is (003) The peak intensity I of the diffraction peak of the (104) crystal plane is (104) The ratio is 1.46 to 2.

00.

14. The lithium ion battery according to any one of claims 5 to 13, wherein The X-ray diffraction spectrum of the lithium-containing transition metal oxide includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the peak intensity I of the diffraction peak of the (003) crystal plane is (003) The peak intensity I of the diffraction peak of the (104) crystal plane is (104) The ratio is 1.46 to 1.

60.

15. The lithium ion battery according to any one of claims 1 to 14, wherein The surface of the secondary particles further includes a coating layer, Part of the L element is located in the primary particle, and another part of the L element is located in the coating layer.

16. The lithium ion battery according to claim 15, wherein The coating layer further comprises acid ions, and the acid ions comprise one or more of inorganic acid ions and organic acid ions.

17. The lithium ion battery according to claim 16, wherein The inorganic acid ions include one or more of hydroxide, carbonate, sulfate, nitrate and chloride; and / or The organic acid ions include one or more of acetate, formate, oxalate and sulfonate.

18. The lithium ion battery according to any one of claims 15 to 17, wherein The thickness of the coating layer is greater than 0 nm and less than or equal to 15 nm.

19. The lithium ion battery according to claim 18, wherein The coating layer has a thickness of 0.5 nm to 6.0 nm.

20. The lithium ion battery according to any one of claims 1 to 19, wherein The volume average particle size D of the secondary particles v50 4 μm to 13 μm; and / or The average particle diameter of the primary particles is 200 nm to 2000 nm.

21. The lithium ion battery according to claim 20, wherein The volume average particle size D of the secondary particles v50 7.5μm to 11.5μm.

22. The lithium ion battery according to any one of claims 1 to 21, wherein The lithium-containing transition metal oxide satisfies one or more of the following conditions: (1) The discharge capacity of the lithium-containing transition metal oxide is 180 mAh / g to 235 mAh / g; (2) The discharge capacity of the lithium-containing transition metal oxide is 215 mAh / g to 235 mAh / g; (3) The powder resistivity of the lithium-containing transition metal oxide is 100 Ω*cm to 2000 Ω*cm; (4) The tap density of the lithium-containing transition metal oxide is 1.5 g / cm 3 Up to 3.0g / cm 3 ; (5) The lithium-containing transition metal oxide satisfies the following conditions: the pH value of the lithium-containing transition metal oxide solution is 11 to 13, The lithium-containing transition metal oxide is dissolved in deionized water to form a lithium-containing transition metal oxide solution, wherein the mass content of the lithium-containing transition metal oxide in the lithium-containing transition metal oxide solution is 10%.

23. The lithium ion battery according to any one of claims 1 to 22, wherein The resistance of the positive electrode plate is 0.3Ω to 1.0Ω.

24. A lithium-containing transition metal oxide, wherein the lithium-containing transition metal oxide has a layered structure and comprises an L element, wherein the L element comprises one or more elements selected from the group consisting of Na, K, Mg, Ca, Sr, Bi, Cu, and Y; The lithium-containing transition metal oxide includes secondary particles, and the secondary particles include a plurality of primary particles. The lithium-containing transition metal oxide satisfies: i / M0 is 30% to 100%, in, Based on the mass of the secondary particles, the mass content of the L element located in the secondary particles is M0; Based on the mass of the secondary particles, the doping content of the L element in the secondary particles is M i .

25. The lithium-containing transition metal oxide according to claim 24, wherein The lithium-containing transition metal oxide satisfies one or more of the following conditions: (1) Based on the mass of the secondary particles, the doping content M of the L element in the secondary particles i 300ppm to 15000ppm; (2) Based on the mass of the secondary particles, the doping content M of the L element in the secondary particles i 300ppm to 14000ppm; (3) Based on the mass of the secondary particles, the doping content M of the L element in the secondary particles i 400ppm to 5000ppm; (4) Based on the mass of the secondary particles, the doping content M of the L element in the secondary particles i 3400ppm to 4650ppm; (5) Based on the mass of the secondary particles, the mass content M0 of the L element located in the secondary particles is 100 ppm to 32000 ppm; (6) Based on the mass of the secondary particles, the mass content M0 of the L element located in the secondary particles is 800 ppm to 8000 ppm; (7)M i / M0 is 30% to 60%; (8)M i / M0 is 40% to 60%.

26. The lithium-containing transition metal oxide according to claim 24 or 25, wherein The primary particle includes a central region and a peripheral region surrounding the central region, wherein the peripheral region is a region extending from the outer surface of the primary particle to the interior of the primary particle within a distance of 5 nm. The average unit area content of the L element in the peripheral region is greater than the average unit area content of the L element in the central region, and the mass content of the L element in the central region is greater than 0 ppm; or There are multiple lithium layers containing lithium transition metal oxide, and the distance between two adjacent lithium layers is to 27. The lithium-containing transition metal oxide according to any one of claims 24 to 26, wherein The lithium-containing transition metal oxide includes a lithium-nickel composite oxide.

28. The lithium-containing transition metal oxide according to any one of claims 24 to 27, wherein The transition metal element of the lithium-containing transition metal oxide includes nickel, and the molar content of the nickel element relative to the total molar amount of the transition metal element is 80% to 100%.

29. The lithium-containing transition metal oxide according to claim 27 or 28, wherein The lithium-containing transition metal oxide includes a general formula of Li a L x Ni b Co c Mn d M (1-b-c-d) O e R f The material, L element includes Na element, 0.001≤x≤0.20, the X-ray diffraction spectrum of the lithium-containing transition metal oxide includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the peak intensity I of the diffraction peak of the (003) crystal plane is (003) The peak intensity I of the diffraction peak of the (104) crystal plane is (104) The ratio is R1; Li a Ni b Co c Mn d M (1-b-c-d) O e R f The X-ray diffraction pattern includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the peak intensity of the diffraction peak of the (003) crystal plane is I (003) The peak intensity I of the diffraction peak of the (104) crystal plane is (104) The ratio is R0; Among them, R1 / R0 is 1 to 1.

7.

30. The lithium-containing transition metal oxide according to any one of claims 24 to 29, wherein The X-ray diffraction spectrum of the lithium-containing transition metal oxide includes a diffraction peak of the (003) crystal plane and a diffraction peak of the (104) crystal plane, and the peak intensity I of the diffraction peak of the (003) crystal plane is (003) The peak intensity I of the diffraction peak of the (104) crystal plane is (104) The ratio is 1.46 to 2.

00.

31. A method for preparing a lithium-containing transition metal oxide, comprising: providing transition metal precursors; The transition metal precursor, lithium source and L source are mixed and calcined to obtain a lithium-containing transition metal oxide, wherein the L ions in the L source include cations corresponding to one or more elements selected from the group consisting of Na, K, Mg, Ca, Sr, Bi, Cu and Y; Wherein, the lithium-containing transition metal oxide includes secondary particles, and the secondary particles include a plurality of primary particles, The lithium-containing transition metal oxide satisfies: i / M0 is 30% to 100%, in, Based on the mass of the secondary particles, the mass content of the L element located in the secondary particles is M0; Based on the mass of the secondary particles, the doping content of the L element in the secondary particles is M i .

32. The preparation method according to claim 31, wherein The molar ratio of the lithium source to the L source is 15 to 25.

33. The preparation method according to claim 31 or 32, wherein The step of mixing the transition metal precursor, the lithium source and the L source and then calcining to obtain the transition metal oxide comprises: mixing the transition metal precursor, the lithium source and the L source to form an intermediate; The intermediate is calcined at a temperature above the melting point of the L source to obtain a transition metal oxide.

34. The preparation method according to claim 33, wherein The step of calcining the intermediate above the melting point of the L source to obtain a transition metal oxide comprises: The intermediate is subjected to a first calcination treatment to melt the L source in the intermediate into a liquid phase, wherein the temperature of the first calcination treatment is greater than or equal to the melting point of the L source; The intermediate after the first calcination treatment is subjected to a second calcination treatment to obtain a transition metal oxide, wherein the temperature of the second calcination treatment is higher than the temperature of the first calcination treatment.

35. The preparation method according to any one of claims 31 to 34, wherein The L source satisfies one of the following conditions: (1) The melting point of the L source is 200°C to 600°C; (2) The melting point of the L source is 210°C to 400°C.

36. The preparation method according to any one of claims 31 to 35, wherein The L source includes one or more of an inorganic L source and an organic L source.

37. The preparation method according to claim 36, wherein The anions in the inorganic L source include one or more of hydroxide, carbonate, sulfate, nitrate and chloride; and / or The anions in the organic L source include one or more of acetate, formate, oxalate, and sulfonate.

38. The preparation method according to any one of claims 31 to 37, wherein The transition metal precursor includes at least one of a nickel source, a cobalt source, and a manganese source.

39. A positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector and containing a positive electrode active material, wherein the positive electrode active material comprises a lithium-containing transition metal oxide, wherein the lithium-containing transition metal oxide comprises an L element, and the L element comprises one or more elements selected from the group consisting of Na, K, Mg, Ca, Sr, Bi, Cu, and Y. The lithium-containing transition metal oxide includes secondary particles, and the secondary particles include a plurality of primary particles. The lithium-containing transition metal oxide satisfies: i / M0 is 30% to 100%, in, Based on the mass of the secondary particles, the mass content of the L element located in the secondary particles is M0; Based on the mass of the secondary particles, the doping content of the L element in the secondary particles is M i .

40. A battery device comprising one or more lithium-ion batteries according to any one of claims 1 to 23, or comprising a positive electrode plate, wherein the positive electrode plate comprises a positive electrode active material, the positive electrode active material comprises a lithium-containing transition metal oxide according to any one of claims 24 to 30 or a lithium-containing transition metal oxide prepared by the preparation method according to claims 31 to 38, or comprises the positive electrode plate according to claim 39.

41. An electrical device comprising the battery device according to claim 40.

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