Multi-doped composite coated lithium cobalt oxide positive electrode material and preparation method and application thereof

Abstract

The present application relates to a multi-doped composite-coated lithium cobaltate cathode material, a preparation method thereof, and an application thereof. The multi-doped composite-coated lithium cobaltate cathode material includes a core, a first coating layer, and a second coating layer. The first coating layer covers the surface of the core, and the second coating layer covers the surface of the first coating layer; the core includes a material with the chemical formula Li 1+y Co 1‑x M1 x O2, where 0 < x ≤ 0.5, 0 ≤ y ≤ 0.2, and M1 includes at least two of Al, Mg, Ti, Zr, Ni, Mn, Y, La, V, Ce, W, Se, Ca, Pd, Ta, Bi, P, Na, Cu, Fe, Zn, Ba, Nb, Mo, Sb, Sn, and B; the first coating layer includes M2, and M2 includes Li and Co; the second coating layer includes a material with the chemical formula A 1‑w Ca w CoO 3‑v , where 0 < w < 1, 0 < v < 3, and A includes at least one of La series elements. The multi-doped composite-coated lithium cobaltate cathode material has good capacity and good cycle stability at a relatively high voltage.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a multi-doped composite coated lithium cobalt oxide positive electrode material and a preparation method and application thereof. Background Art

[0002] In recent years, lithium cobalt oxide cathode materials have attracted widespread attention due to their advantages such as high specific capacity, high compaction density and tap density, and high voltage. However, the actual gram capacity of lithium cobalt oxide is relatively low, which limits the further development of lithium cobalt oxide cathode materials. Increasing the working voltage is one of the effective ways to improve the energy density of lithium cobalt oxide cathode materials.

[0003] Traditional lithium cobalt oxide positive electrode materials are prone to problems such as lithium cobalt oxide phase change, metal ion dissolution, lattice oxygen evolution and increased interface side reactions when working at higher voltages, which makes it difficult to further increase the gram capacity of lithium cobalt oxide positive electrode materials. Summary of the invention

[0004] Based on this, it is necessary to provide a multi-doped composite coated lithium cobalt oxide positive electrode material and a preparation method and application thereof, wherein the multi-doped composite coated lithium cobalt oxide positive electrode material has a higher capacity and better cycle stability at a higher voltage.

[0005] In a first aspect, the present application provides a multi-doped composite coated lithium cobalt oxide positive electrode material, comprising a core, a first coating layer and a second coating layer, wherein the first coating layer is coated on the surface of the core, and the second coating layer is coated on the surface of the first coating layer;

[0006] The core comprises a chemical formula of Li 1+y Co 1-x M1 x O2 materials, wherein 0<x≤0.5, 0≤y≤0.2, M1 includes at least two of Al, Mg, Ti, Zr, Ni, Mn, Y, La, V, Ce, W, Se, Ca, Pd, Ta, Bi, P, Na, Cu, Fe, Zn, Ba, Nb, Mo, Sb, Sn and B;

[0007] The first coating layer includes M2, and M2 includes Li and Co;

[0008] The second coating layer comprises a chemical formula of A 1-w Ca w CoO 3-v A material, wherein 0<w<1, 0<v<3, and A includes at least one La series element.

[0009] In some embodiments, the M1 accounts for 0.03% to 0.5% of the mass of the core by mass percentage;

[0010] and / or, the mass of the first coating layer is 2% to 15% of the mass of the core;

[0011] And / or, the mass of the second coating layer is 0.1% to 1% of the mass of the core.

[0012] In some embodiments, the D50 particle size of the core is 1 μm to 10 μm or 10 μm to 30 μm.

[0013] In a second aspect, the present application provides a method for preparing a multi-doped composite coated lithium cobalt oxide positive electrode material, comprising:

[0014] The Li source, the Co source and the M1 source are sequentially mixed, first sintered and crushed to obtain a first powder;

[0015] The first powder and the M2 source are sequentially mixed, second sintered and crushed to obtain a second powder;

[0016] The second powder and the M3 source are sequentially mixed and sintered for a third time;

[0017] The M1 source includes at least two of Al, Mg, Ti, Zr, Ni, Mn, Y, La, V, Ce, W, Se, Ca, Pd, Ta, Bi, P, Na, Cu, Fe, Zn, Ba, Nb, Mo, Sb, Sn and B, the M2 source includes Li and Co, the M3 source includes Ca, and the M3 source also includes at least one of the La series elements.

[0018] In some embodiments, the Li source includes at least one of lithium carbonate, lithium hydroxide, lithium phosphate, lithium nitrate, lithium acetate, and lithium oxalate; and / or the Co source includes at least one of cobalt tetroxide, cobalt hydroxide, cobalt carbonate, and cobalt oxyhydroxide.

[0019] In some embodiments, the D50 particle size of the Co source is 2 μm to 6 μm or 10 μm to 20 μm.

[0020] In some embodiments, the M1 source is selected from at least one of oxides, carbonates, hydroxides, oxalates, and fluorides; and / or, the M3 source is selected from at least one of oxides, carbonates, hydroxides, oxalates, and fluorides.

[0021] In some embodiments, the first sintering temperature is 950° C. to 1100° C.; and / or, the first sintering time is 6 h to 15 h;

[0022] and / or, the temperature of the second sintering is 850° C. to 950° C.; and / or, the time of the second sintering is 6 h to 10 h;

[0023] And / or, the temperature of the third sintering is 750° C. to 850° C.; and / or, the time of the third sintering is 4 h to 8 h.

[0024] In a third aspect, the present application provides a positive electrode plate, comprising a current collector and an active layer located on at least one surface of the current collector, wherein the active layer comprises any of the multi-doped composite coated lithium cobalt oxide positive electrode materials described above or a multi-doped composite coated lithium cobalt oxide positive electrode material prepared by any of the preparation methods described above.

[0025] In a fourth aspect, the present application provides a lithium-ion battery, comprising the above-mentioned positive electrode plate.

[0026] The above-mentioned multi-doped composite coated lithium cobalt oxide positive electrode material has a core of multi-element doped lithium cobalt oxide, which stabilizes the lattice structure of the core, can inhibit irreversible phase change, improve the cycle stability of the positive electrode material at higher voltages and higher temperatures, and improve the rate performance of the battery. Li and Co elements are added to the first coating layer. The addition of Li can make up for the Li loss and Li vacancies in the positive electrode material. After the Co element is coated, it forms an "island-like" coating on the surface of the particle, increasing the roughness of the particle surface, and the epitaxial growth forms a layered structure solid solution with the doped elements on the surface of the core, which can inhibit the side reaction of the positive electrode material with the electrolyte at a higher voltage and reduce the loss of electrochemical capacity. The second coating layer generates a Co-containing perovskite structure coating layer A on the basis of the first coating layer at high temperature. 1-w Ca w CoO 3-v , stabilize the surface structure, alleviate the overflow of Co and O, and improve the cycle stability. The multi-doped composite coated lithium cobalt oxide positive electrode material has good capacity and good cycle stability at a higher voltage.

[0027] The method for preparing the multi-doped composite coated lithium cobalt oxide positive electrode material can prepare the multi-doped composite coated lithium cobalt oxide positive electrode material so that the material has good capacity and good cycle stability at a higher voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a scanning electron microscope image of the multi-doped composite-coated lithium cobalt oxide positive electrode material provided in Example 1 of the present application at a magnification of 1000;

[0029] Figure 2 The scanning electron microscope image of the multi-doped composite coated lithium cobalt oxide positive electrode material provided in Example 6 of the present application has a magnification of 3000;

[0030] Figure 3 XRD diagram of the positive electrode materials provided in Example 1, Example 6 and Comparative Example 1 of the present application;

[0031] Figure 4A schematic diagram of the discharge capacity test results of button cells provided in Example 1 and Comparative Examples 1 to 3 of the present application;

[0032] Figure 5 Schematic diagram of the test results of the cycle performance of button batteries provided in Example 1 and Comparative Examples 1 to 3 of the present application at a relatively high temperature. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0035] An embodiment of the present application provides a multi-doped composite coated lithium cobalt oxide positive electrode material, comprising a core, a first coating layer and a second coating layer, wherein the first coating layer is coated on the surface of the core, and the second coating layer is coated on the surface of the first coating layer;

[0036] The core includes a chemical formula of Li 1+y Co 1-x M1 x O2 materials, wherein 0<x≤0.5, 0≤y≤0.2, M1 includes at least two of Al, Mg, Ti, Zr, Ni, Mn, Y, La, V, Ce, W, Se, Ca, Pd, Ta, Bi, P, Na, Cu, Fe, Zn, Ba, Nb, Mo, Sb, Sn and B;

[0037] The first coating layer includes M2, and M2 includes Li and Co;

[0038] The second coating layer comprises a chemical formula of A 1-w Ca w CoO 3-v A material, wherein 0<w<1, 0<v<3, and A includes at least one La series element.

[0039] The above-mentioned multi-doped composite coated lithium cobalt oxide positive electrode material has a core of multi-element doped lithium cobalt oxide, which stabilizes the lattice structure of the core, can inhibit irreversible phase change, improve the cycle stability of the positive electrode material at higher voltages and higher temperatures, and can also improve the rate performance of the battery. Li and Co elements are added to the first coating layer. The addition of Li can make up for the Li loss and Li vacancies in the positive electrode material. After the Co element is coated, an "island-like" coating is formed on the surface of the particles, increasing the roughness of the particle surface. The epitaxial growth of Li and Co elements forms a layered structure solid solution with the doped elements on the surface of the core, which can inhibit the side reaction of the positive electrode material with the electrolyte at a higher voltage and reduce the loss of electrochemical capacity. The second coating layer generates a Co-containing perovskite structure coating layer A on the basis of the first coating layer at high temperature. 1-w Ca w CoO 3-v , stabilize the surface structure, alleviate the overflow of Co and O, and improve the cycle stability. The multi-doped composite coated lithium cobalt oxide positive electrode material has good capacity and good cycle stability at a higher voltage.

[0040] Optionally, x is 0.00001, 0.0001, 0.001, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4 or 0.5.

[0041] Optionally, y is 0, 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18 or 0.2.

[0042] Optionally, w is 0.00001, 0.0001, 0.001, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.99, 0.999 or 0.9999.

[0043] Optionally, v is 0.00001, 0.0001, 0.001, 0.01, 0.05, 0.1, 0.2, 0.5, 0.7, 1, 1.2, 1.5, 1.7, 2, 2.2, 2.5, 2.7, 2.9, 2.99, 2.999 or 2.9999.

[0044] In some embodiments, M1 accounts for 0.03% to 0.5% of the mass of the core by mass percentage. Within the range of the mass percentage of M1 to the mass of the core, M1 has a good doping effect on lithium cobalt oxide, stabilizes the lattice structure of the core, improves the cycle stability of the positive electrode material at higher voltages and higher temperatures, and can improve the rate performance of the battery. Optionally, M1 accounts for 0.03%, 0.05%, 0.08%, 0.1%, 0.13%, 0.15%, 0.18%, 0.2%, 0.23%, 0.25%, 0.28%, 0.3%, 0.33%, 0.35%, 0.38%, 0.4%, 0.43%, 0.45%, 0.48% or 0.5% of the mass of the core by mass percentage.

[0045] In some embodiments, the mass of the first coating layer is 2% to 15% of the mass of the core. Within the percentage range of the mass of the first coating layer to the mass of the core, the Li and Co in the first coating layer are better in forming a layered solid solution on the surface of the core, which can inhibit the side reaction of the positive electrode material with the electrolyte at a higher voltage, and at the same time can make up for the Li loss and Li vacancy in the positive electrode material, reducing the electrochemical capacity loss. Preferably, the mass of the first coating layer is 3% to 12% of the mass of the core. Further optionally, the mass of the first coating layer is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11% or 12% of the mass of the core.

[0046] In some embodiments, the mass of the second coating layer is 0.1% to 1% of the mass of the core. Within the range of the mass of the second coating layer to the mass of the core, a Co-containing perovskite structure coating layer A is generated on the basis of the first coating layer at high temperature. 1-w Ca w CoO 3-v , stabilize the surface structure, alleviate the overflow of Co and O, and improve the cycle stability. Preferably, the mass of the second coating layer is 0.1% to 0.5% of the mass of the core. Further optionally, the mass of the second coating layer is 0.1%, 0.2%, 0.3%, 0.4% or 0.5% of the mass of the core.

[0047] In one embodiment, M1 accounts for 0.03% to 0.5% of the mass of the core by mass percentage, the mass of the first coating layer is 3% to 12% of the mass of the core, and the mass of the second coating layer is 0.1% to 0.5% of the mass of the core.

[0048] In some embodiments, the D50 particle size of the core is 1 μm to 10 μm or 10 μm to 30 μm. The core can be a large particle or a small particle. When the D50 particle size of the core is 1 μm to 10 μm, it is a small particle, and when the D50 particle size is 10 μm to 30 μm, it is a large particle. Optionally, the D50 particle size of the core is 1 μm, 3 μm, 5 μm, 7 μm, 10 μm, 15 μm, 20 μm, 25 μm or 30 μm.

[0049] Another embodiment of the present application provides a method for preparing a multi-doped composite-coated lithium cobalt oxide positive electrode material, comprising:

[0050] The Li source, the Co source and the M1 source are sequentially mixed, first sintered and crushed to obtain a first powder;

[0051] The first powder and the M2 source are sequentially mixed, second sintered and crushed to obtain a second powder;

[0052] The second powder and the M3 source are sequentially mixed and sintered for the third time;

[0053] The M1 source includes at least two of Al, Mg, Ti, Zr, Ni, Mn, Y, La, V, Ce, W, Se, Ca, Pd, Ta, Bi, P, Na, Cu, Fe, Zn, Ba, Nb, Mo, Sb, Sn and B, the M2 source includes Li and Co, the M3 source includes Ca, and the M3 source also includes at least one of the La series elements.

[0054] The method for preparing the multi-doped composite coated lithium cobalt oxide positive electrode material can prepare the multi-doped composite coated lithium cobalt oxide positive electrode material so that the material has good capacity and good cycle stability at a higher voltage.

[0055] In one embodiment, the Li source includes at least one of lithium carbonate, lithium hydroxide, lithium phosphate, lithium nitrate, lithium acetate, and lithium oxalate.

[0056] In one embodiment, the Co source includes at least one of cobalt tetroxide, cobalt hydroxide, cobalt carbonate, and cobalt oxyhydroxide.

[0057] In some embodiments, the D50 particle size of the Co source is 2μm to 6μm or 10μm to 20μm. The Co source can be large particles or small particles. The D50 particle size of the Co source is 2μm to 6μm for small particles, and the D50 particle size of the Co source is 10μm to 20μm for large particles. Within the D50 particle size range of the Co source, the Co source, the Li source and the M1 source are mixed more uniformly when sintered together, and the sintering effect is better. Optionally, the D50 particle size of the Co source is 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm or 20μm.

[0058] In some embodiments, the M1 source includes at least one of an oxide, a carbonate, a hydroxide, an oxalate, and a fluoride.

[0059] In some embodiments, the M3 source includes at least one of an oxide, a carbonate, a hydroxide, an oxalate, and a fluoride.

[0060] In some embodiments, the first sintering temperature is 950° C. to 1100° C.; and / or, the first sintering time is 6 h to 15 h;

[0061] and / or, the temperature of the second sintering is 850° C. to 950° C.; and / or, the time of the second sintering is 6 h to 10 h;

[0062] And / or, the temperature of the third sintering is 750° C. to 850° C.; and / or, the time of the third sintering is 4 h to 8 h.

[0063] In one embodiment, the first sintering temperature is 950°C to 1100°C. Optionally, the first sintering temperature is 950°C, 1000°C, 1050°C or 1100°C.

[0064] In one embodiment, the first sintering time is 6 hours to 15 hours. Optionally, the first sintering time is 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours.

[0065] In one embodiment, the first sintering temperature is 950° C. to 1100° C., and the first sintering time is 6 h to 15 h.

[0066] In one embodiment, the second sintering temperature is 850° C. to 950° C. Optionally, the second sintering temperature is 850° C., 870° C., 890° C., 900° C., 920° C. or 950° C.

[0067] In one embodiment, the second sintering time is 6 hours to 10 hours. Optionally, the second sintering time is 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours or 10 hours.

[0068] In one embodiment, the second sintering temperature is 850° C. to 950° C., and the second sintering time is 6 h to 10 h.

[0069] In one embodiment, the temperature of the third sintering is 750° C. to 850° C. Optionally, the temperature of the third sintering is 750° C., 770° C., 790° C., 800° C., 810° C., 830° C. or 850° C.

[0070] In one embodiment, the third sintering time is 4 hours to 8 hours. Optionally, the third sintering time is 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours.

[0071] In one embodiment, the temperature of the third sintering is 750° C. to 850° C., and the time of the third sintering is 4 h to 8 h.

[0072] In one embodiment, the first sintering temperature is 950℃~1100℃, and the first sintering time is 6h~15h; the second sintering temperature is 850℃~950℃, and the second sintering time is 6h~10h; the third sintering temperature is 750℃~850℃, and the third sintering time is 4h~8h.

[0073] Another embodiment of the present application provides a positive electrode plate, including a current collector and an active layer located on at least one surface of the current collector, the active layer including any of the above-mentioned multi-doped composite coated lithium cobalt oxide positive electrode materials or a multi-doped composite coated lithium cobalt oxide positive electrode material prepared by any of the above-mentioned preparation methods.

[0074] Another embodiment of the present application provides a lithium-ion battery, comprising the above-mentioned positive electrode plate.

[0075] The following are specific embodiments

[0076] Example 1

[0077] Preparation of multi-doped composite coated lithium cobalt oxide positive electrode materials:

[0078] (1) Co3O4, Li2CO3, Al2O3 and MgO with a D50 particle size of 10 μm to 20 μm were weighed and mixed evenly at a molar ratio of Li / Co=1.060 to obtain a mixed powder, wherein the mass of Al2O3 was 0.3% of the mass of Co3O4, and the mass of MgO was 0.1% of the mass of Co3O4. The mixed powder was placed in a box furnace for sintering at a sintering temperature of 1000°C for 10 hours, and the first powder of aluminum-magnesium-doped lithium cobalt oxide was obtained after crushing.

[0079] (2) Weigh a certain amount of the first powder, and then weigh 1.3% of Li2CO3 and 6% of Co(OH)2 in a mass ratio according to the mass percentage of the first powder. After mixing evenly, sinter them in a bell-type furnace at a sintering temperature of 870°C for 8 hours, and then crush them to obtain the second powder.

[0080] (3) Weigh a certain amount of the second powder, and then weigh the M3 compound. According to the percentage of the mass of the second powder, the M3 compound is 0.1% CaO and 0.3% La2O3. After mixing evenly, sinter in a bell furnace at a sintering temperature of 830°C for 7 hours. After crushing, a multi-doped composite coated lithium cobalt oxide positive electrode material is obtained, and its D50 is 18μm to 19μm. The obtained positive electrode material is characterized by scanning electron microscopy. The SEM image is shown in Figure 1 .

[0081] Example 2

[0082] The difference between Example 2 and Example 1 is that in step (1), Co3O4, Li2CO3, Y2O, ZrO2 and Al2O3 with a D50 particle size of 10μm to 20μm are weighed at a molar ratio of Li / Co=1.060, wherein the mass of Y2O is 0.1% of the mass of Co3O4, the mass of ZrO2 is 0.05% of the mass of Co3O4, and the mass of Al2O3 is 0.5% of the mass of Co3O4. After mixing, the sintering temperature is 1050℃ and the holding time is 12h.

[0083] Example 3

[0084] The difference between Example 3 and Example 1 is that in step (2), 1.8% of the mass of Li2CO3 and 8% of Co(OH)2 are weighed based on the mass of the first powder, and after mixing, the sintering temperature is 900°C and the holding time is 8 hours.

[0085] Example 4

[0086] The difference between Example 4 and Example 1 is that in step (3), M3 compound is weighed again, and the percentage of M3 compound to the mass of the second powder is 0.1% CaCO3 and 0.2% Gd2O3. After mixing, the sintering temperature is 800°C and the insulation time is 8h.

[0087] Example 5

[0088] Preparation of multi-doped composite coated lithium cobalt oxide positive electrode materials:

[0089] (1) Co3O4, Li2CO3, Al2O3, WO3 and Y2O3 with a D50 particle size of 10 μm to 20 μm were weighed and mixed uniformly to obtain a mixed powder, wherein the mass of Al2O3 was 0.3% of the mass of the mixed powder, the mass of WO3 was 0.1% of the mass of the mixed powder, and the mass of Y2O3 was 0.05% of the mass of the mixed powder. The mixed powder was placed in a box furnace for sintering at a sintering temperature of 1060° C. and a sintering time of 8 h, and then crushed to obtain a first powder.

[0090] (2) Weigh a certain amount of the first powder, then weigh 1% of the mass of the first powder in LiOH and 5% of CoOOH, mix them evenly, and sinter them in a bell-type furnace at a sintering temperature of 850° C. for 9 hours. After crushing, the second powder is obtained.

[0091] (3) Weigh a certain amount of the second powder and then weigh the M3 compound, which is 0.1% CaO and 0.1% CeO2 in terms of percentage of the mass of the second powder. After mixing evenly, sinter them in a bell-type furnace at a sintering temperature of 800°C for 8 hours. After crushing, a multi-doped composite coated lithium cobalt oxide positive electrode material is obtained, and its D50 is 18μm to 19μm.

[0092] Example 6

[0093] Preparation of multi-doped composite coated lithium cobalt oxide positive electrode materials:

[0094] (1) Co3O4, Li2CO3, Al2O3, MgO and ZrO2 with a D50 particle size of 2 μm to 6 μm were weighed at a molar ratio of Li / Co=1.050, and mixed evenly to obtain a mixed powder, wherein the mass of Al2O3 is 0.25% of the mass of the mixed powder, the mass of MgO is 0.1% of the mass of the mixed powder, and the mass of ZrO2 is 0.05% of the mass of the mixed powder. The mixed powder was placed in a box furnace for sintering at a sintering temperature of 980°C and a sintering time of 10 hours, and then crushed to obtain a first powder.

[0095] (2) Weigh a certain amount of the first powder, then weigh 1.5% of the mass of the first powder in Li2CO3 and 6% of Co(OH)2, mix them evenly and sinter them in a bell-type furnace at a sintering temperature of 900°C for 10 hours, and then crush them to obtain the second powder.

[0096] (3) Weigh a certain amount of the second powder, and then weigh the M3 compound. According to the percentage of the mass of the second powder, the M3 compound is 0.2% CaO and 0.2% La2O3. The sintering temperature is 830°C and the sintering time is 8h. After crushing, a multi-doped composite coated lithium cobalt oxide positive electrode material is obtained, and its D50 is 4μm~6μm.

[0097] Comparative Example 1

[0098] (1) Co3O4 and Li2CO3 with a D50 particle size of 10 μm to 20 μm were weighed and mixed evenly at a molar ratio of Li / Co = 1.060 to obtain a mixed powder. The mixed powder was placed in a box furnace for sintering at a sintering temperature of 1060°C for 8 hours and then crushed to obtain a positive electrode material.

[0099] Comparative Example 2

[0100] Comparative Example 2 differs from Example 1 in that step (2) is not performed.

[0101] Comparative Example 3

[0102] Comparative Example 3 differs from Example 1 in that step (3) is not performed.

[0103] Comparative Example 4

[0104] (1) Co3O4 and Li2CO3 with a D50 particle size of 2 μm to 6 μm were weighed and mixed evenly at a molar ratio of Li / Co=1.050 to obtain a mixed powder. The mixed powder was placed in a box furnace for sintering at a sintering temperature of 980°C for 10 h, and then crushed to obtain a positive electrode material.

[0105] Battery Assembly

[0106] The positive electrode materials prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were dispersed and added to the solvent NMP at a weight ratio of 90:5:5, respectively, and mixed evenly to obtain positive electrode slurry; the positive electrode slurry was evenly coated on the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained. The positive electrode sheet, polypropylene separator, graphite negative electrode sheet and electrolyte (Li PF6 propylene carbonate solution) were assembled into a button battery.

[0107] Performance Testing

[0108] The positive electrode materials of Example 1 and Example 6 were subjected to SEM testing. At room temperature, a JSM-IT100 electron scanning microscope was used to test and analyze the surface morphology of the prepared positive electrode active materials. The test results are shown in Table 1. Figure 1 and 2 .

[0109] XRD test was performed on the positive electrode materials of Example 1, Example 6 and Comparative Example 1. The physical phase of the prepared positive electrode active materials was tested and analyzed using a Japanese SmartLabSE model X-ray diffractometer under room temperature. The test results are shown in Table 1. Figure 3 ,It can be seen from the figure that the diffraction peak of the positive electrode material after multi-doped composite coating has not shifted and no impurity phase has appeared.

[0110] Capacity tests and cycle tests were performed on button-type batteries assembled from the positive electrode materials prepared in Examples 1 to 6 and Comparative Examples 1 to 4, respectively.

[0111] Capacity test: The button cells assembled from the positive electrode materials prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were tested using a Blue Electric charge and discharge instrument. The test format at room temperature was as follows: constant current charging to 4.55V at a current density of 0.1C, constant voltage charging to 50uA, and then discharging to 3V at 0.1C to test the discharge capacity.

[0112] Cycle test: The cycle test format is as follows: at 45°C, charge and discharge 50 times in the voltage range of 3.0V to 4.6V at a charge and discharge rate of 1C. Discharge specific capacity = first discharge capacity / mass of positive electrode active material. 50-cycle capacity retention rate = 50th discharge capacity / 1st discharge capacity. Figure 4 , 5 , the test results are shown in Table 1 below:

[0113] Table 1

[0114]

[0115]

[0116] It can be seen from the test results that the button-type batteries assembled from the multi-doped composite-coated lithium cobalt oxide positive electrode materials prepared in Examples 1 to 6 have a high discharge specific capacity and a capacity retention rate after 50 cycles at 45°C.

[0117] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0118] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims, and the description and drawings may be used to interpret the contents of the claims.

Claims

1. A multi-doped composite coated lithium cobalt oxide positive electrode material, characterized in that: It comprises a core, a first coating layer and a second coating layer, wherein the first coating layer is coated on the surface of the core, and the second coating layer is coated on the surface of the first coating layer; The core comprises a chemical formula of Li 1+y Co 1-x M1 x O2 material, wherein 0<x≤0.5, 0≤y≤0.2, M1 includes at least two of Al, Mg, Ti, Zr, Ni, Mn, Y, La, V, Ce, W, Se, Ca, Pd, Ta, Bi, P, Na, Cu, Fe, Zn, Ba, Nb, Mo, Sb, Sn and B; the M1 accounts for 0.03% to 0.5% of the mass of the core by mass percentage; The first coating layer includes M2, M2 includes Li and Co; the mass of the first coating layer is 2% to 15% of the mass of the core; The second coating layer comprises a chemical formula of A 1-w Ca w CoO 3-v A material, wherein 0<w<1, 0<v<3, A includes at least one La series element; the mass of the second coating layer is 0.1%~1% of the mass of the core.

2. The multi-doped composite coated lithium cobalt oxide positive electrode material according to claim 1, characterized in that: The D50 particle size of the core is 1 μm to 10 μm or 10 μm to 30 μm.

3. A method for preparing the multi-doped composite coated lithium cobalt oxide positive electrode material according to any one of claims 1 to 2, characterized in that: include: The Li source, the Co source and the M1 source are sequentially mixed, first sintered and crushed to obtain a first powder; The first powder and the M2 source are sequentially mixed, second sintered and crushed to obtain a second powder; The second powder and the M3 source are sequentially mixed and sintered for a third time; The M1 source includes at least two of Al, Mg, Ti, Zr, Ni, Mn, Y, La, V, Ce, W, Se, Ca, Pd, Ta, Bi, P, Na, Cu, Fe, Zn, Ba, Nb, Mo, Sb, Sn and B, the M2 source includes Li and Co, the M3 source includes Ca, and the M3 source also includes at least one of the La series elements; The first sintering temperature is 950° C. to 1100° C.; the first sintering time is 6 h to 15 h; The temperature of the second sintering is 850°C to 950°C; the time of the second sintering is 6h to 10h; The temperature of the third sintering is 750° C. to 850° C.; the time of the third sintering is 4 h to 8 h.

4. The method for preparing the multi-doped composite coated lithium cobalt oxide positive electrode material according to claim 3, characterized in that: The Li source includes at least one of lithium carbonate, lithium hydroxide, lithium phosphate, lithium nitrate, lithium acetate, and lithium oxalate; and / or the Co source includes at least one of cobalt tetroxide, cobalt hydroxide, cobalt carbonate, and cobalt oxyhydroxide.

5. The method for preparing the multi-doped composite coated lithium cobalt oxide positive electrode material according to claim 4, characterized in that: The D50 particle size of the Co source is 2 μm to 6 μm or 10 μm to 20 μm.

6. The method for preparing the multi-doped composite coated lithium cobalt oxide positive electrode material according to claim 3, characterized in that: The M1 source is selected from at least one of oxides, carbonates, hydroxides, oxalates and fluorides; the M3 source is selected from at least one of oxides, carbonates, hydroxides, oxalates and fluorides.

7. A positive electrode sheet, characterized in that: It comprises a current collector and an active layer located on at least one surface of the current collector, wherein the active layer comprises the multi-doped composite coated lithium cobalt oxide positive electrode material as described in any one of claims 1 to 2 or the multi-doped composite coated lithium cobalt oxide positive electrode material prepared by the preparation method as described in any one of claims 3 to 6.

8. A lithium ion battery, characterized in that: Including the positive electrode sheet as described in claim 7.

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