Positive electrode material, preparation method therefor, and lithium-ion battery

Abstract

A positive electrode material, a preparation method therefor, and a lithium-ion battery. The composition of the positive electrode material is Li1+a(NixCoyMnzGb)TcO2, where 0.02 ≤ a ≤ 0.1, 0.6 ≤ x ≤ 1, 0 < y ≤ 0.5, 0 < z ≤ 0.5, 0 < b ≤ 0.02, and 0< c ≤ 0.02. At 45°C as measured by XRD, the (003) characteristic peak before and after 80 cycles satisfies 0°≤ △P = Pbefore - Pafter ≤ 0.2°, where Pbefore is the peak position of the (003) characteristic peak before cycling, and Pafter is the peak position of the (003) characteristic peak after 80 cycles. The positive electrode material has high particle strength and excellent crystal structure stability, resulting in a significant improvement in the cycling performance of the positive electrode material.

Description

Positive electrode material and preparation method thereof, and lithium ion battery

[0001] Priority information

[0002] This application claims priority to and the benefits of patent application 202410244850.X filed on March 4, 2024 with the State Intellectual Property Office of China, and incorporates the entire text of that application herein by reference. Technical Field

[0003] The present invention relates to the technical field of lithium ion batteries, and in particular to a positive electrode material and a preparation method thereof, and a lithium ion battery. Background Art

[0004] In recent years, with the development of the global new energy vehicle industry, lithium-ion batteries have become increasingly popular due to their high energy density and excellent cycle performance. Ternary materials are widely used due to their high energy density and excellent low-temperature performance. In pursuit of even higher energy density, high nickel content and high voltage have become the two main development directions. However, the main problem currently faced by both high nickel content and high voltage is the poor structural stability of the materials, which in turn leads to poor cycle stability and increased gas production.

[0005] In order to solve the problem of structural stability, the main means at present are to improve it by adjusting the internal structure of the material, bulk doping and surface coating. For example, CN108598379A discloses a lithium tungstate coated nickel cobalt aluminum oxide composite material and its preparation method and application. The nickel cobalt aluminum precursor is dispersed in a lithium-containing solution, and then tungsten trioxide is added. The lithium-containing solution will react with the tungsten trioxide to generate Li2WO4. During the evaporation and crystallization process, Li2WO4 will be directly deposited and coated on the nickel cobalt aluminum precursor, and then mixed lithium sintering is performed to obtain LiNi. 0.8 Co 0.15 Al 0.05 O2@Li2WO4, through this in-situ reaction, the deposited coating formed can form a very uniform coating layer. The positive electrode material prepared by this method has a good doping coating effect, but the process is complicated, the filtrate recovery process is complicated, and the cost is high.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to overcome the problems of low particle strength and poor crystal structure stability of the positive electrode material in the prior art, and to provide a positive electrode material, a preparation method thereof, and a lithium ion battery. The positive electrode material has a small peak position change value of the (003) characteristic peak after 80 cycles at 45°C, indicating that the positive electrode material has high particle strength and more excellent crystal structure stability, so that the cycle performance of the positive electrode material is significantly improved.

[0008] To achieve the above object, a first aspect of the present invention provides a cathode material, wherein the cathode material has a composition shown in Formula I: Li 1+a (Ni x Co y Mn z G b )T c O2 Formula I;

[0009] where 0.02 ≤ a ≤ 0.1, 0.6 ≤ x ≤ 1, 0 < y ≤ 0.5, 0 < z ≤ 0.5, 0 < b ≤ 0.02, 0 < c ≤ 0.02; G is selected from at least one of Al, Y, Zr, Ti, Ca, V, Nb, Ta, Co, W, Er, La, Sb, Mg, Sr, Sn, Mn, Mo, Ce, F, B and P; T is selected from at least one of Al, Sr, Si, Nb, Co, W, Ti, Zr, Ce, Mn, F, B and P;

[0010] where, at 45 °C measured by XRD, the (003) characteristic peaks before and after 80 - week cycling satisfy the following relationship:

[0011] 0° ≤ ΔP = P 前 - P 后 ≤ 0.2°, where P 前 is the peak position of the (003) characteristic peak before cycling, and P 后 is the peak position of the (003) characteristic peak after 8 weeks of cycling.

[0012] A second aspect of the present invention provides a preparation method of the above cathode material, wherein the preparation method includes the following steps:

[0013] (1) Physically mix a precursor, a lithium source, and optionally an additive containing a C1 element to obtain a uniform mixture Ι;

[0014] (2) Under an oxygen - containing atmosphere, perform the first sintering on the mixture Ι, with a constant - temperature of T1 and a constant - temperature time of t1. After sintering, perform crushing and sieving or directly sieving to obtain a first - sintered material II;

[0015] (3) Mix the first - sintered material II with an optionally C2 - element - containing additive to obtain a uniform mixture III;

[0016] (4) Under an oxygen - containing atmosphere, perform the second sintering on the mixture III, with a constant - temperature of T2 and a constant - temperature time of t2. After sintering, perform crushing and sieving or directly sieving to obtain a second - sintered material IV;

[0017] (5) Mix the second - sintered material IV with a T - element - containing additive to obtain a uniform mixture V;

[0018] (6) sintering the mixture V for a third time in an oxygen-containing atmosphere at a constant temperature of T3 and a constant temperature time of t3, and crushing and sieving or directly sieving after sintering to obtain the positive electrode material;

[0019] The precursor is selected from nickel-cobalt-manganese oxide and / or nickel-cobalt-manganese hydroxide; the lithium source and the precursor are used in an amount such that n(Li):[n(Ni)+n(Co)+n(Mn)+n(G)]=1.02-1.10:1;

[0020] Wherein, at least one of an additive containing a C1 element and an additive containing a C2 element is added.

[0021] A third aspect of the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises the above-mentioned positive electrode material.

[0022] Through the above technical solution, the positive electrode material and preparation method thereof, and the lithium-ion battery provided by the present invention achieve the following beneficial effects:

[0023] The peak position change value of the characteristic peak (003) of the positive electrode material of the present invention after 80 cycles at 45°C is small, indicating that the positive electrode material has high particle strength and more excellent crystal structure stability, which is beneficial to Li ion transmission and cycle performance. When used in lithium-ion batteries, it has a high discharge capacity while ensuring a high capacity retention rate.

[0024] Furthermore, the positive electrode material of the present invention has a low lattice volume change rate at different SOCs, which can further improve the particle strength and crystal structure stability of the positive electrode material, thereby further improving the discharge capacity and capacity retention rate of the lithium-ion battery.

[0025] The preparation method provided by the present invention, by adjusting the specific amount of lithium added and employing a three-step sintering process, ensures uniform reaction between the precursor and the lithium source while ensuring that the additive G element (C1 element and / or C2 element) and T element exert their respective effects at a specific temperature. The preparation method provided by the present invention can improve the effects of the elements while reducing the residual alkali content on the surface, thereby improving the particle strength and structural stability of the resulting positive electrode material.

[0026] Furthermore, controlling the temperature of the three sintering steps to meet specific conditions can allow different elements to enter different positions of the material. At high temperatures, they enter the core of the material, at sub-high temperatures, they enter the shallow layer of the material, and at low temperatures, they adhere to the surface. This improves the strength and structural stability of the particles in multiple dimensions from the inside to the surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments in conjunction with the accompanying drawings, in which:

[0028] FIG. 1 is a diagram of the position of the 003 peak measured by an XRD diffractometer for the positive electrode material before and after cycling in Example 1;

[0029] FIG. 2 is a diagram of the position of the 003 peak measured by an XRD diffractometer for the positive electrode material before and after cycling in Comparative Example 1;

[0030] FIG. 3 is an EDS analysis diagram of the cross-section of the positive electrode material in Example 4;

[0031] FIG. 4 is a comparison of the cycling performance of lithium-ion batteries assembled from the positive electrode materials of Example 1 and Comparative Example 1.

[0032] Detailed Description of the Invention

[0033] The endpoints and any values disclosed herein for a range are not limited to the exact range or value, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0034] The first aspect of the present invention provides a positive electrode material, characterized in that the positive electrode material has the composition shown in Formula I: Li 1+a (Ni x Co y Mn z G b )T c O2 Formula I;

[0035] Where, 0.02 ≤ a ≤ 0.1, 0.6 ≤ x ≤ 1, 0 < y ≤ 0.5, 0 < z ≤ 0.5, 0 < b ≤ 0.02, 0 < c ≤ 0.02; G is selected from at least one of Al, Y, Zr, Ti, Ca, V, Nb, Ta, Co, W, Er, La, Sb, Mg, Sr, Sn, Mn, Mo, Ce, F, B and P, and T is selected from at least one of Al, Sr, Si, Nb, Co, W, Ti, Zr, Ce, Mn, F, B and P;

[0036] Where, at 45°C measured by XRD, the (003) characteristic peaks before and after 80 weeks of cycling satisfy the following relationship:

[0037] 0° ≤ ΔP = P 前 -P 后 ≤ 0.2°, where, P 前 is the peak position of the (003) characteristic peak before cycling, P后 is the peak position of the characteristic peak (003) after 80 cycles.

[0038] In the present invention, the peak position change value of the characteristic peak (003) of the positive electrode material after 80 cycles at 45°C is small, indicating that the positive electrode material has high particle strength and more excellent crystal structure stability, which is beneficial to Li ion transport and cycle performance. In particular, the positive electrode material contains an appropriate Li content, which can ensure that when the positive electrode material is used in a lithium-ion battery, it has a high discharge capacity while ensuring a high capacity retention rate.

[0039] In the present invention, the peak position change value of the (003) characteristic peak of the positive electrode material after 80 cycles at 45°C is measured using the following method:

[0040] The positive electrode material is prepared into a lithium-ion battery according to conventional methods. Specifically, the lithium-ion battery includes a positive electrode sheet, a negative electrode sheet, a separator between the positive electrode sheet and the negative electrode sheet, and an electrolyte.

[0041] The positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer located on the positive electrode current collector. The positive electrode material layer comprises the positive electrode material, a binder and a conductive agent.

[0042] The binder of the positive electrode material layer is a conventional choice in the battery field, and its type and content are not specifically limited. It can be a combination of one or more of polyvinylidene fluoride (PVDF), vinylidene fluoride copolymers or their modified (for example, carboxylic acid, acrylic acid, acrylonitrile, etc.) derivatives.

[0043] The conductive agent of the positive electrode material layer is a conventional choice in the battery field, and its type and content are not specifically limited. It can be a combination of one or more of acetylene black, conductive carbon black, carbon fiber (VGCF), carbon nanotube (CNT), Ketjen black, etc., including but not limited to.

[0044] The positive electrode current collector can generally be a layer, and the positive electrode current collector is generally a structure or part that can collect current. The positive electrode current collector can be various materials in the art that are suitable for use as a positive electrode current collector for an electrochemical energy storage device. For example, the positive electrode current collector can include but is not limited to metal foil, and more specifically can include but is not limited to nickel foil and aluminum foil.

[0045] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on the surface of the negative electrode current collector. The negative electrode active material layer generally includes a negative electrode active material. The negative electrode active material is conventionally selected in the battery field, and the type and content are not specifically limited. It can include, but is not limited to, one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, lithium titanate, or other metals capable of forming alloys with lithium.

[0046] Among them, the graphite can be selected from a combination of one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be selected from a combination of one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, and silicon alloys; the tin-based material can be selected from a combination of one or more of elemental tin, tin oxide compounds, and tin alloys.

[0047] The negative electrode current collector is generally a structure or component that collects current. The negative electrode current collector can be any material suitable for use as a negative electrode current collector for lithium secondary batteries. For example, the negative electrode current collector can include but is not limited to metal foil, more specifically, copper foil. In addition, the negative electrode plate can also be a lithium plate.

[0048] The separator is a common choice in the battery field. The type and content are not specifically limited and can be a combination of one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fibers.

[0049] The electrolyte is a conventional choice in the battery field. The type and content are not specifically limited. It can be various electrolytes suitable for lithium secondary batteries in the field. For example, the electrolyte generally includes an electrolyte and a solvent. The electrolyte generally includes a lithium salt. More specifically, the lithium salt can be an inorganic lithium salt and / or an organic lithium salt, and can specifically include but is not limited to one or more combinations of LiPF6, LiBF4, LiN(SO2F)2 (abbreviated as LiFSI), LiN(CF3SO2)2 (abbreviated as LiTFSI), LiClO4, LiAsF6, LiB(C2O4)2 (abbreviated as LiBOB), and LiBF2C2O4 (abbreviated as LiDFOB).

[0050] The partially fabricated batteries were fully charged and discharged at 45°C with a current of 1C for 80 cycles. Finally, the uncycled and cycled electrodes were disassembled, cleaned, and tested with an XRD diffractometer. Due to the changes in the crystal structure before and after the cycle, the XRD peak position will move synchronously. The peak positions of the characteristic peaks (003) before and after the cycle are named P and P respectively. 前 and P 后 , peak position change value △P=P 前 -P 后 The larger the ΔP, the poorer the crystal structure stability of the cathode material during the cycle.

[0051] In the present invention, in addition to the Li element, Ni, Co, Mn and G elements are distributed inside and on the surface of the positive electrode material particles, while the T element is distributed on the surface of the positive electrode material particles.

[0052] In the present invention, the element T in the positive electrode material is the main element in the coating, and the coating includes an oxide containing the T element and may also include at least one element of Ni, Co, Mn, and G from the matrix.

[0053] In the present invention, in Formula I, a can be 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, and a range consisting of any two values; x can be 0.6, 0.7, 0.8, 0.9, 1, and a range consisting of any two values; y can be 0.01, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.4, 0.50, and a range consisting of any two values; z can be 0.01, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.4, 0.50, and a range consisting of any two values; b can be 0.001, 0.0015, 0.0020, 0.0025, 0.0030 ,0.0035,0.0040,0.0045,0.0050,0.0055,0.0060,0.0065,0.0070,0.0075,0.0080,0.0085,0.0090,0.0095,0.010,0.015,0.02, and the range of any two values; c can be 0.001, 0.0015, 0 0.0020,0.0025,0.0030,0.0035,0.0040,0.0045,0.005,0.0055,0.0060,0.0065,0.0070,0.0075,0.0080,0.0085,0.0090,0.0095,0.010,0.015,0.02, and any range consisting of any two values.

[0054] Furthermore, 0.03≤a≤0.07, 0.6≤x≤1, 0 <y≤0.5,0<z≤0.5,0.005≤b≤0.015,0.002≤c≤0.015。

[0055] Furthermore, G is selected from at least one of Al, Ti, Co, Sr, Ce, F, Y, Zr, W and La; T is selected from at least one of B, Al, Si, W and F;

[0056] In the present invention, ΔP can be 0°, 0.01°, 0.02°, 0.03°, 0.04°, 0.05°, 0.06°, 0.07°, 0.08°, 0.09°, 0.10°, 0.11°, 0.12°, 0.13°, 0.14°, 0.15°, 0.16°, 0.17°, 0.18°, 0.19°, 0.2°, and a range consisting of any two values.

[0057] Furthermore, 0°≤△P≤0.1°.

[0058] In the present invention, in Formula I, y and z represent only the content of Co or Mn in the cathode material from the precursor (nickel cobalt manganese oxide and / or nickel cobalt manganese hydroxide). When G contains Co and / or Mn, the sum of the content of Co or Mn as the G element and the content of other G elements is recorded as b.

[0059] Specifically, when G contains Co and / or Mn, the positive electrode material has a composition shown in Formula II: Li 1+a (Ni x Co' y Mn' z Co” d Mn” e G f )T c O2 Formula I;

[0060] Among them, 0.02≤a≤0.1, 0.6≤x≤1, 0 <y≤0.5,0<z≤0.5,0<d+e+f=b≤0.02,0<c≤0.02;

[0061] G is selected from at least one of Al, Y, Zr, Ti, Ca, V, Nb, Ta, W, Er, La, Sb, Mg, Sr, Sn, Mo, Ce, F, B and P, and T is selected from at least one of Al, Sr, Si, Nb, Co, W, Ti, Zr, Ce, Mn, F, B and P. Co' and Mn' are derived from the precursor, and Co" and Mn" are derived from the doping element. In the positive electrode material, the content of Co (or Mn) derived from the precursor and Co (or Mn) as the G element are calculated based on the feed amount during the preparation of the positive electrode material.

[0062] According to the present invention, the lattice volume V of the positive electrode material at 0% SOC, 50% SOC and 100% SOC measured by XRD satisfies the following relationship:

[0063] 0%≤△V 50％ =(V 50 -V0) / V0≤10%, and / or, 0%≤△V 100％ =(V 100-V0) / V0≤15%,

[0064] Wherein, V0 is the lattice volume of the positive electrode material at 0% SOC; V 50 The lattice volume of the positive electrode material at 50% SOC; V 100 The lattice volume of the positive electrode material at 100% SOC.

[0065] In the present invention, when the lattice volume V of the positive electrode material satisfies the above relationship at different SOCs, it indicates that the positive electrode material has a low lattice volume change rate during the charging process, further indicating that the positive electrode material has high particle strength and excellent crystal structure stability, thereby further improving the discharge capacity and capacity retention rate of the lithium-ion battery containing the positive electrode material.

[0066] In the present invention, the lattice volume V of the positive electrode material at SOC is measured by the following method: the positive electrode material is made into a battery according to the corresponding formula, and then charged to the corresponding 0% SOC, 50% SOC, and 100% SOC respectively. Finally, the corresponding battery is disassembled, the electrode piece is cleaned, and then an XRD diffractometer test is performed.

[0067] In the present invention, ΔV 50％ It can be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any range of two values; △V 100％ It can be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or a range consisting of any two values.

[0068] Furthermore, 0%≤△V 50％ ≤5%.

[0069] Furthermore, 0%≤V 100％ ≤10%.

[0070] According to the present invention, the specific surface area SSA of the positive electrode material before and after compression satisfies the following relationship:

[0071] 0%≤△SSA%=(SSA4-SSA0) / SSA0≤80%, wherein SSA0 is the specific surface area of ​​the positive electrode material before being compressed, and SSA4 is the specific surface area of ​​the positive electrode material after being subjected to a pressure of 4.5 tons.

[0072] The change rate of the specific surface area of ​​the positive electrode material before and after compression can reflect the bulk particle strength of the positive electrode material, △SSA ％ The larger the value, the poorer the positive electrode material particle strength. In the present invention, the change rate of the specific surface area of ​​the positive electrode material before and after compression is low, indicating that the positive electrode material has high bulk particle strength.

[0073] In the present invention, the specific surface area of ​​the positive electrode material before and after compression is measured as follows: the positive electrode material is subjected to a pressure of 4.5 tons using an MCP-PD51 tester, then ground using a mortar and pestle, and passed through a 300-mesh sieve to obtain a powder under the pressure for specific surface area testing. The specific surface areas of the positive electrode material before and after compression are SSA0 and SSA4, respectively, and the specific surface area increase rate is ΔSSA%. The specific surface area increase rate is calculated as ΔSSA% = (SSA4 - SSA0) / SSA0.

[0074] In the present invention, ΔSSA% can be 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or a range consisting of any two values.

[0075] Further, 0≤ΔSSA%≤50%.

[0076] According to the present invention, the median particle size of the positive electrode material is 2-20 μm, for example, it can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, and a range consisting of any two values, preferably 3-18 μm.

[0077] According to the present invention, the residual alkali content of the positive electrode material is 0-10000ppm, for example, it can be 0ppm, 10ppm, 20ppm, 30ppm, 40ppm, 50ppm, 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1200ppm, 1400ppm, 1600ppm, 1800ppm, 2000ppm, 2500ppm, 3000ppm, 3500ppm, 4000ppm, 4500ppm, 5000ppm, 5500ppm, 6000ppm, 6500ppm, 7000ppm, 7500ppm, 8000ppm, 8500ppm, 9000ppm, 9500ppm, 10000ppm, and a range consisting of any two values, preferably 1000-8000ppm.

[0078] In the present invention, the residual lithium includes lithium carbonate and / or lithium hydroxide.

[0079] A second aspect of the present invention provides a method for preparing the above-mentioned positive electrode material, characterized in that the preparation method comprises the following steps:

[0080] (1) physically mixing the precursor, the lithium source, and optionally an additive containing a Cl element to obtain a uniform mixture I;

[0081] (2) In an oxygen-containing atmosphere, the mixture I is subjected to a first sintering process at a constant temperature of T1 and a constant temperature of time of t1. After sintering, the mixture is crushed and sieved or directly sieved to obtain a primary sintered material II;

[0082] (3) mixing the primary sintered material II with an additive optionally containing a C2 element to obtain a uniform mixture III;

[0083] (4) sintering the mixture III for a second time in an oxygen-containing atmosphere at a constant temperature of T2 and a constant temperature time of t2, and crushing and screening or directly screening after sintering to obtain a secondary sintered material IV;

[0084] (5) mixing the secondary sintered material IV with an additive containing the T element to obtain a uniform mixture V;

[0085] (6) sintering the mixture V for a third time in an oxygen-containing atmosphere at a constant temperature of T3 and a constant temperature time of t3, and crushing and sieving or directly sieving after sintering to obtain the positive electrode material;

[0086] The precursor is selected from nickel cobalt manganese oxide and / or nickel cobalt manganese hydroxide; the amount of the lithium source, the precursor, the additive containing the C1 element, and the additive containing the C2 element is such that n(Li):[n(Ni)+n(Co)+n(Mn)+n(G)] in the positive electrode material is 1.02-1.10:1;

[0087] Wherein, at least one of an additive containing a C1 element and an additive containing a C2 element is added.

[0088] In the present invention, the preparation method, by adjusting a specific amount of lithium addition and adopting a three-step sintering process, ensures that the precursor and lithium source react uniformly while ensuring that the additive G element (C1 element and / or C2 element) and T element play their corresponding roles at a specific temperature, and ensures that the positive electrode material has a high Li transmission rate. The preparation method provided by the present invention can reduce the surface residual alkali content while improving the role of the elements, improve the particle strength and structural stability of the prepared positive electrode material, and obtain the positive electrode material with a specific composition and structure as described in the first aspect of the present invention.

[0089] In the present invention, the amounts of the lithium source, the precursor, the additive containing the C1 element, and the additive containing the C2 element are such that n(Li):[n(Ni)+n(Co)+n(Mn)+n(G)] is 1.02:1, 1.03:1, 1.04:1, 1.05:1, 1.06:1, 1.07:1, 1.08:1, 1.09:1, 1.10:1, and a range consisting of any two values.

[0090] Furthermore, the lithium source, the precursor, the additive containing the C1 element, and the additive containing the C2 element are used in amounts such that n(Li):[n(Ni)+n(Co)+n(Mn)+n(G)]=1.03-1.07:1.

[0091] According to the present invention, the amount of the precursor, the additive containing the C1 element and the additive containing the C2 element is such that the positive electrode material contains 0 <n(G):[n(Ni)+n(Co)+n(Mn)+n(G)]≤0.02。

[0092] In the present invention, when the total amount of the additive containing the C1 element and the additive containing the C2 element is controlled to meet the above range, it is beneficial to the differentiated distribution of elements inside the material and in the shallow layer, improve the structural stability and particle strength of the material, and make the battery assembled from the positive electrode material have good charge and discharge capacity and cycle performance.

[0093] In the present invention, there is no particular limitation on the amount of each of the additive containing a C1 element and the additive containing a C2 element, as long as the total amount of the additives satisfies the above range.

[0094] In the present invention, the amount of the precursor, the additive containing the C1 element and the additive containing the C2 element is such that n(G):[n(Ni)+n(Co)+n(Mn)+n(G)] in the positive electrode material is 0.001, 0.0015, 0.0020, 0.0025, 0.0030, 0.0035, 0.0040, 0.0045, 0.0050, 0.0055, 0.0060, 0.0065, 0.0070, 0.0075, 0.0080, 0.0085, 0.0090, 0.0095, 0.010, 0.015, 0.02, and a range consisting of any two values.

[0095] Furthermore, the amounts of the precursor, the additive containing the C1 element, and the additive containing the C2 element are such that 0.005≤n(G):[n(Ni)+n(Co)+n(Mn)+n(G)]≤0.015 in the positive electrode material.

[0096] According to the present invention, the amount of the secondary sintering material and the additive containing the T element is such that the positive electrode material contains 0 <n(T):[n(Ni)+n(Co)+n(Mn)+n(G)]≤0.02。

[0097] In the present invention, when the amount of the additive containing the T element is controlled to meet the above range, a protective layer is generated on the surface of the material, further improving the surface stability and particle strength of the material.

[0098] In the present invention, the amount of the secondary sintered material and the additive containing the T element is such that in the positive electrode material, n(T):[n(Ni)+n(Co)+n(Mn)+n(G)] is 0.001, 0.0015, 0.0020, 0.0025, 0.0030, 0.0035, 0.0040, 0.0045, 0.0050, 0.0055, 0.0060, 0.0065, 0.0070, 0.0075, 0.0080, 0.0085, 0.0090, 0.0095, 0.010, 0.015, 0.02, and a range consisting of any two values.

[0099] Furthermore, the amounts of the secondary sintered material and the additive containing the T element are such that 0.002≤n(T):[n(Ni)+n(Co)+n(Mn)+n(G)]≤0.015 in the positive electrode material.

[0100] According to the present invention, C1 and C2 are each independently selected from at least one of Al, Y, Zr, Ti, Ca, V, Nb, Ta, Co, W, Er, La, Sb, Mg, Sr, Sn, Mn, Mo, Ce, F, B and P.

[0101] In a preferred embodiment of the present invention, Cl is selected from at least one of Al, Y, Zr, W, La, Sr, and Ce. The specific Cl element helps to further improve the lattice stability of the positive electrode material.

[0102] In another preferred embodiment of the present invention, C2 is selected from at least one of Al, Ti, Co, Sr, Ce and F. The above specific type of C2 element can further reduce the residual alkali content on the surface of the positive electrode material and improve the particle strength of the positive electrode material.

[0103] According to the present invention, T is selected from at least one of Al, Sr, Si, Nb, Co, W, Ti, Zr, Ce, Mn, F, B and P, and is preferably selected from at least one of B, Al, Si, W and F.

[0104] In the present invention, there is no particular limitation on the type of lithium source, which may be lithium carbonate, hydrous lithium hydroxide or anhydrous lithium hydroxide.

[0105] In the present invention, there is no particular limitation on the types of additives containing C1 elements, C2 elements, and T elements, as long as they can provide C1 elements, C2 elements, or T elements, and they may be, for example, oxides, hydroxides, or carbonates.

[0106] According to the present invention, the constant temperature T1, the constant temperature T2 and the constant temperature T3 satisfy the following relationship:

[0107] 200℃≤T3<T2<T1≤1000℃;

[0108] In the present invention, when the temperature of the three sintering processes is controlled to satisfy the above relationship, the structural stability of the positive electrode material can be further improved. Specifically, the first sintering process is carried out at a higher temperature and a high lithium ratio, so that the precursor, the lithium salt and the additive containing the C1 element can fully react to form a primary sintered material with rich bulk doping, thereby improving the hardness and density of the positive electrode material and improving the structural stability of the positive electrode material; the second sintering process is carried out at a relatively high temperature, so that the primary sintered material and the additive containing the C2 element can form a secondary sintered material with further surface doping, thereby reducing the residual alkali on the surface and improving the particle strength of the positive electrode material; the third sintering process is carried out at a lower temperature, so that the additive containing the T element can be coated on the particle surface to further improve the particle strength of the positive electrode material.

[0109] According to the present invention, 200°C ≤ T3 ≤ 500°C.

[0110] According to the present invention, 400°C ≤ T2 ≤ 900°C.

[0111] In the present invention, T3 can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, and a range consisting of any two values.

[0112] In the present invention, T2 can be 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, and a range consisting of any two values.

[0113] Further, 250℃≤T3<T2<T1≤980℃, 50℃≤T1-T2≤300℃, for example, T1-T2 is 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 150℃, 200℃, 250℃, 300℃, and a range consisting of any two values.

[0114] Furthermore, 250°C ≤ T3 ≤ 450°C.

[0115] Furthermore, 500°C ≤ T2 ≤ 800°C.

[0116] In the present invention, the constant temperature time t1 is 6-18h.

[0117] In the present invention, the constant temperature time t2 is 6-14h.

[0118] In the present invention, the constant temperature time t3 is 6-12h.

[0119] In the present invention, there is no special requirement for the equipment used for crushing, as long as it can achieve crushing, such as one or more of a soybean milk machine, a jaw crusher, a roller mill, a rotary mill, a colloid mill, a mechanical mill, and a jet mill.

[0120] In the present invention, the oxygen-containing atmosphere is oxygen and / or air.

[0121] In the present invention, the residual alkali content of the secondary sintered material IV is 3000ppm-15000ppm, for example, it can be 3000ppm, 3500ppm, 4000ppm, 4500ppm, 5000ppm, 5500ppm, 6000ppm, 6500ppm, 7000ppm, 7500ppm, 8000ppm, 8500ppm, 9000ppm, 9500ppm, 10000ppm, 11000ppm, 12000ppm, 13000ppm, 14000ppm, 15000ppm, and a range consisting of any two values, preferably 3000ppm-10000ppm.

[0122] A third aspect of the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises the above-mentioned positive electrode material.

[0123] The present invention will be described in detail below through examples.

[0124] The peak position of the (003) characteristic peak and the lattice volume of the positive electrode material were measured by XRD. The specific test conditions were: working temperature: 21±5°C, humidity: ≤65%; cooling water circulation machine: temperature: 23±1°, water pressure: 0.36MPa; refrigerant high pressure: 0.8-1.8MPa, refrigerant low pressure: 0.4-0.7MPa; scanning speed (Scanspeed) 5° / min; starting angle: 10.0000, ending angle: 90.0000; SamplingW: 0.0200; automatic rotation table speed: 60° / min.

[0125] The specific surface area of ​​the positive electrode material was measured using a Tri-star 3020 surface area analyzer from Micromeritics, USA. The specific test conditions were: sample weight: 5.0 g; equipment degassing time / temperature: 100°C / 120 min (ventilation purge); adsorbate: N2, 99.99%; liquid nitrogen temperature: -196°C; multi-point BET method: P / P0 0.060, 0.080, 0.120, 0.160, 0.200.

[0126] The median particle size of the positive electrode material was measured using a Malvern Mastersizer 3000 laser particle size analyzer. The specific test conditions were: dispersant: 650 ml + 20 ml 5% sodium pyrophosphate; particle refractive index: 1.741; particle absorptivity: 1; solvent refractive index: Water / 1.330; total amount of particles and dispersant: about 800 mL; test cycle: 1 time; background test time: 5 s; stirrer / pump speed: 2850 r / min; analysis mode: general purpose; light shielding: 14-16%.

[0127] The residual alkali content of the positive electrode material and the sintered material was measured using a Swiss Metrohm potentiometric titrator. The specific test conditions were as follows: take 5 g of sample, add 95 g of water, stir for 5 min, filter 80 mL, and test the residual alkali by potentiometric titration with 0.1 mol / L hydrochloric acid.

[0128] Electrochemical performance test of button cell:

[0129] Battery composition: 9.5g of the positive electrode active material sample, 0.25g of acetylene black, and 0.25g of polyvinylidene fluoride (PVDF) were mixed to form a positive electrode slurry. This slurry was coated on aluminum foil and dried. Then, it was pressed using a pressure of 100 MPa to form a 12mm diameter and 120μm thickness sheet. The sheet was then dried in a vacuum oven at 120°C for 12 hours to obtain a positive electrode sheet.

[0130] The negative electrode uses a Li metal sheet with a diameter of 17 mm and a thickness of 1 mm; the separator uses a polyethylene porous membrane with a thickness of 25 μm; a 1.0 mol / L LiPF6 solution is used as the electrolyte, in which an equal amount of a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) is used as the solvent.

[0131] The positive electrode sheet, separator, negative electrode sheet and electrolyte are assembled into a 2025 button battery.

[0132] Capacity test conditions: The prepared button cell samples were placed for 24 hours. The battery samples were charged at a current density of 20 mA / g to a cut-off voltage of 4.3 V. Constant voltage charging was performed at 4.3 V for 30 minutes. Subsequently, the samples were discharged at a current density of 20 mA / g to a cut-off voltage of 3.0 V. The discharge time was recorded.

[0133] The initial discharge specific capacity of the battery sample = current density × discharge time.

[0134] Testing at different SOCs: The prepared button cell samples were left to rest for 24 hours. Charged at a current density of 20 mA / g to a cutoff voltage of 4.3 V. Constant voltage charging was performed at 4.3 V for 30 minutes. Discharged at a current density of 20 mA / g to a cutoff voltage of 3.0 V, and the discharge time was recorded. The cells were then charged at a current density of 20 mA / g to 3.73 V and 4.30 V, corresponding to 50% and 100% SOC, respectively. Waiting for disassembly.

[0135] Cycle test conditions: The battery sample is charged and discharged twice at a current density of 20mA / g, with a cut-off voltage of 3.0-4.3V, and activation is completed. Using the activated battery sample, at a temperature of 45°C, a current density of 1C in the voltage range of 3.0-4.3V, a specified number of charge and discharge cycles, for example 80 times, are performed. As described above, the discharge specific capacity of each charge and discharge cycle is obtained by comparing the current density with the discharge time of each cycle. The cycle performance of the battery sample is characterized by the high-temperature capacity retention rate, and the cycle performance is shown in Figure 4.

[0136] Here, the high-temperature capacity retention rate, % = discharge specific capacity at a specified 80 cycles / initial discharge specific capacity×100%.

[0137] Battery disassembly: disassemble the battery in the glove box, remove the electrode, clean it with DMC for 1 minute, dry it, and wait for testing.

[0138] The raw materials used in the examples and comparative examples are all commercially available products.

[0139] Example 1

[0140] (1) The precursor (Ni 0.8 Co 0.1 Mn 0.1)(OH)2, lithium hydroxide, Al2O3 and ZrO2 are physically and uniformly mixed to obtain a mixture I, wherein the amounts of the precursor, lithium hydroxide, Al2O3 and ZrO2 are such that n(Li):[n(Ni)+n(Co')+n(Mn)+n(Al)+n(Zr)+n(Co")]=1.05, n(Al):[n(Ni)+n(Co')+n(Mn)+n(Al)+n(Zr)+n(Co")]=0.08, and n(Zr):[n(Ni)+n(Co')+n(Mn)+n(Al)+n(Zr)+n(Co")]=0.003 in the positive electrode material;

[0141] (2) The mixture I was subjected to a first sintering in an oxygen atmosphere at a constant temperature of 790°C for 9 hours. After sintering, the mixture was directly sieved to obtain a primary sintered material II.

[0142] (3) mixing the primary sintered material II with Co(OH)2 to obtain a uniform mixture III, wherein the amount of Co(OH)2 added is such that n(Co):[n(Ni)+n(Co')+n(Mn)+n(Al)+n(Zr)+n(Co")]=0.108 in the positive electrode material;

[0143] (4) The mixture III was sintered for the second time in an oxygen atmosphere at a constant temperature of 700°C for 8 hours. After sintering, the mixture was directly sieved to obtain a secondary sintered material IV.

[0144] (5) mixing the secondary sintered material IV with boric acid according to [n(Ni)+n(Co)+n(Mn)+n(Al)+n(Zr)]:n(B)=1:0.005 to obtain a uniform mixture V;

[0145] (6) The mixture V was sintered for the third time in air atmosphere at a constant temperature of 350°C for 8 hours. After sintering, it was directly sieved to obtain the final positive electrode material with a composition of Li 1.05 (Ni 0.783 Co' 0.098 Mn 0.098 Al 0.008 Zr 0.003 Co” 0.010 )B 0.005 O2, where Co' comes from the precursor and Co" comes from Co(OH)2, which is simplified to Li 1.05 (Ni 0.783 Co 0.108 Mn 0.098 Al 0.008 Zr 0.003 )B 0.005 O2.

[0146] Examples and Comparative Examples

[0147] The positive electrode material was prepared according to the method of Example 1. The specific preparation process parameters are shown in Table 1.

[0148] Table 1

[0149] Table 1 continued

[0150] Table 1 continued

[0151] Table 1 continued

[0152] The structural parameters of the positive electrode materials prepared in the examples and comparative examples and the performance indicators of the lithium ion batteries assembled from the positive electrode materials in the examples and comparative examples are shown in Table 2.

[0153] Table 2

[0154] Table 2 continued

[0155] As can be seen from Table 2, the positive electrode material prepared by the present invention has the characteristics of high particle strength, low lattice volume change rate, and small peak value change before and after cycling. The prepared lithium-ion battery not only has a high discharge capacity, but also can ensure a high capacity retention rate.

[0156] Figure 1 is a graph showing the position of the 003 peak of the positive electrode material of Example 1 before and after 80 cycles of XRD diffractometer testing, and Figure 2 is a graph showing the position of the 003 peak of the positive electrode material of Comparative Example 1 before and after 80 cycles of XRD diffractometer testing. It can be seen from Figures 1 and 2 that the degree of peak position displacement in Example 1 is smaller than that in Comparative Example 1.

[0157] FIG3 is an EDS analysis diagram of the cross section of the positive electrode material of Example 4. It can be seen from FIG3 that the Al element inside the material is uniform. After the secondary sintering, the Al and Co contents in the shallow layer increase, indicating that the elements have entered the shallow layer of the material.

[0158] FIG4 is a comparison of the cycle performance of lithium-ion batteries assembled from the positive electrode materials of Example 1 and Comparative Example 1. It can be seen from FIG4 that the cycle performance of Example 1 is significantly better than that of Comparative Example 1.

[0159] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A positive electrode material, characterized in that The positive electrode material has a composition shown in Formula I: Li 1+a (Ni x Co y Mn z G b )T c O2 Formula I; Among them, 0.02 ≤ a ≤ 0.1, 0.6 ≤ x ≤ 1, 0 < y ≤ 0.5, 0 < z ≤ 0.5, 0 < b ≤ 0.02, 0 < c ≤ 0.02; G is selected from at least one of Al, Y, Zr, Ti, Ca, V, Nb, Ta, Co, W, Er, La, Sb, Mg, Sr, Sn, Mn, Mo, Ce, F, B, and P; T is selected from at least one of Al, Sr, Si, Nb, Co, W, Ti, Zr, Ce, Mn, F, B, and P; Among them, the (003) characteristic peaks before and after 80 - week cycling at 45 °C measured by XRD satisfy the following relationship: 0°≤△P=P 前 -P 后 ≤0.2°, where P 前 is the peak position of the characteristic peak (003) before the cycle, P 后 is the peak position of the characteristic peak (003) after 80 cycles.

2. The positive electrode material according to claim 1, wherein 0.03 ≤ a ≤ 0.07, 0.6 ≤ x ≤ 1, 0 < y ≤ 0.5, 0 < z ≤ 0.5, 0.005 ≤ b ≤ 0.015, 0.002 ≤ c ≤ 0.015; and / or, G is selected from at least one of Al, Ti, Co, Sr, Ce, F, Y, Zr, W, and La; T is selected from at least one of B, Al, Si, W, and F; and / or, 0° ≤ ΔP ≤ 0.1°.

3. The positive electrode material according to claim 1 or 2, wherein The lattice volume V of the cathode material at 0% SOC, 50% SOC, and 100% SOC measured by XRD satisfies the following relationship: 0%≤△V 50％ =(V 50 -V0) / V0≤10%, and / or, 0%≤△V 100％ =(V 100 -V0) / V0≤15%, Wherein, V0 is the lattice volume of the positive electrode material at 0% SOC; V 50 The lattice volume of the positive electrode material at 50% SOC; V 100 The lattice volume of the positive electrode material at 100% SOC.

4. The positive electrode material according to any one of claims 1 to 3, wherein The specific surface area SSA of the cathode material before and after being compressed satisfies the following relationship: 0% ≤ ΔSSA% = (SSA4 - SSA0) / SSA0 ≤ 80%, preferably, 0% ≤ ΔSSA% ≤ 50%, where SSA0 is the specific surface area of the cathode material before being compressed, and SSA4 is the specific surface area of the cathode material after being under a pressure of 4.5 tons.

5. The positive electrode material according to any one of claims 1 to 4, wherein The median particle size of the cathode material is 2 - 20 μm, preferably 3 - 18 μm; and / or, the residual alkali content of the cathode material is 0 - 10000 ppm, preferably 1000 - 8000 ppm.

6. A method for preparing the positive electrode material according to any one of claims 1 to 5, characterized in that: The preparation method includes the following steps: (1) Physically mix the precursor, lithium source, and optionally an additive containing C1 element to obtain a homogeneous mixture Ι; (2) Under an oxygen - containing atmosphere, perform the first sintering on the mixture Ι, with a constant - temperature of T1 and a constant - temperature time of t1. After sintering, perform crushing and sieving or directly sieve to obtain the first - sintered material II; (3) Mix the first - sintered material II with an optionally C2 - element - containing additive to obtain a homogeneous mixture III; (4) Under an oxygen - containing atmosphere, perform the second sintering on the mixture III, with a constant - temperature of T2 and a constant - temperature time of t2. After sintering, perform crushing and sieving or directly sieve to obtain the second - sintered material IV; (5) Mix the second - sintered material IV with a T - element - containing additive to obtain a homogeneous mixture V; (6) Under an oxygen - containing atmosphere, perform the third sintering on the mixture V, with a constant - temperature of T3 and a constant - temperature time of t3. After sintering, perform crushing and sieving or directly sieve to obtain the cathode material; Among them, the precursor is selected from nickel cobalt manganese oxide and / or nickel cobalt manganese hydroxide; the amounts of the lithium source, the precursor, the additive containing C1 element, and the additive containing C2 element are such that n(Li):[n(Ni)+n(Co)+n(Mn)+n(G)] = 1.02 - 1.10:1; Among them, at least one of the additive containing C1 element and the additive containing C2 element is added.

7. The preparation method according to claim 6, wherein The amounts of the lithium source, the precursor, the additive containing C1 element, and the additive containing C2 element are such that n(Li):[n(Ni)+n(Co)+n(Mn)+n(G)] = 1.03 - 1.07:1; Preferably, the amounts of the precursor, the additive containing C1 element, and the additive containing C2 element are such that 0 < n(G):[n(Ni)+n(Co)+n(Mn)+n(G)] ≤ 0.02 in the cathode material, and preferably, 0.005 ≤ n(G):[n(Ni)+n(Co)+n(Mn)+n(G)] ≤ 0.015; Preferably, the amounts of the secondary sintered material and the additive containing T element are such that 0 < n(T):[n(Ni)+n(Co)+n(Mn)+n(G)] ≤ 0.02 in the cathode material, and preferably, 0.002 ≤ n(T):[n(Ni)+n(Co)+n(Mn)+n(G)] ≤ 0.

015.

8. The preparation method according to claim 6 or 7, wherein C1 and C2 are each independently selected from at least one of Al, Y, Zr, Ti, Ca, V, Nb, Ta, Co, W, Er, La, Sb, Mg, Sr, Sn, Mn, Mo, Ce, F, B, and P; And / or, T is selected from at least one of Al, Sr, Si, Nb, Co, W, Ti, Zr, Ce, Mn, F, B, and P, preferably selected from at least one of B, Al, Si, W, and F; Preferably, C1 is selected from at least one of Al, Y, Zr, W, La, Sr, and Ce; Preferably, C2 is selected from at least one of Al, Ti, Co, Sr, Ce, and F.

9. The preparation method according to any one of claims 6 to 8, wherein The constant temperature T1, the constant temperature T2, and the constant temperature T3 satisfy the following relationship: 200°C ≤ T3 < T2 < T1 ≤ 1000°C; Preferably, 200°C ≤ T3 ≤ 500°C; Preferably, 400°C ≤ T2 ≤ 900°C.

10. A lithium ion battery, characterized in that: The lithium ion battery includes the cathode material according to any one of claims 1 - 5.

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