Nickel-cobalt-manganese multi-element positive electrode material, preparation method and application thereof, and lithium ion battery

Abstract

The application relates to the technical field of lithium ion batteries, and discloses a nickel-cobalt-manganese multi-element positive electrode material, a preparation method and application thereof, and a lithium ion battery. The nickel-cobalt-manganese multi-element positive electrode material contains a doping element Ce, and the surface of the nickel-cobalt-manganese multi-element positive electrode material is coated with CeO2; the occupancy rate of Ce at the lattice 3b position obtained by XRD of the nickel-cobalt-manganese multi-element positive electrode material satisfies 2.1‰<=Ce<=6‰. 3b The occupancy rate of Ce at the lattice 3b position obtained by XRD of the nickel-cobalt-manganese multi-element positive electrode material satisfies 2.1‰<=Ce<=6‰. 3b The nickel-cobalt-manganese multi-element positive electrode material contains a doping element Ce, and the surface of the nickel-cobalt-manganese multi-element positive electrode material is coated with CeO2, and the occupancy rate of Ce at the lattice 3b position in the positive electrode material satisfies a specific range, so that the structural stability of the positive electrode material is remarkably improved, and further, the lithium ion battery containing the positive electrode material has the advantages of high energy density, good rate performance and high cycle capacity retention rate. Meanwhile, the preparation method of the positive electrode material is simple and easy for batch production.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a nickel-cobalt-manganese multi-element cathode material, its preparation method, and its application. Background Technology

[0002] With the escalating environmental pollution and energy crisis, non-fossil fuel-powered vehicles—pure electric vehicles (EVs), plug-in hybrid electric vehicles (PHEVs), and hybrid electric vehicles (HEVs)—have received considerable attention in recent years. Lithium-ion batteries for vehicles require high energy density, long cycle life, and good safety. Cathode materials, as the core and key materials for power lithium batteries, influence various performance aspects of automotive batteries. Their performance determines the battery's energy density, lifespan, and safety. Increasing the nickel content in multi-component cathode materials is currently the main method for achieving high energy density in batteries. However, as the nickel content increases, the structural and thermal stability of multi-component materials decreases, leading to a decline in the battery's cycle performance and safety indicators. Methods to improve the electrical properties of materials mainly include bulk doping and surface coating.

[0003] CN113258059A discloses a multi-modified lithium-ion battery cathode material. In the synthesis process of this cathode material, CeO2 is added to the reactor to synthesize a precursor. However, CeO2 is difficult to dissolve in water and alkaline solutions, making it difficult to introduce Ce into the precursor through liquid-phase reaction, and it is difficult to achieve a large amount of uniform doping. The patent then mixes the precursor, lithium source and cerium nitrate and sinters to obtain the cathode material. There is no post-treatment such as water washing. Nitrate ions will be directly introduced into the cathode material, affecting the capacity and electrical performance.

[0004] CN109301207A discloses a Ce-doped surface layer. 3+ Furthermore, the ternary material with CeO2 coating on the surface is subjected to ultrasonic treatment in ethanol with cerium nitrate and NCM cathode material for 1-2 hours, followed by grinding and sintering. This cathode material is only modified on the surface and is not doped in the bulk phase, which has limited effect on the internal structural stability. Moreover, this method is relatively complex, requires the use of ethanol, poses safety hazards, and is difficult to implement in industrial production. In addition, ultrasonic treatment of the cathode material in ethanol will damage the material structure and affect the electrical performance.

[0005] To improve the structural stability of cathode materials, rational design of doping and coating compounds and processing methods can enhance material performance while facilitating industrial production. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem that the structural stability, thermal stability, cycle performance, safety performance, and energy density of nickel-cobalt-manganese (NCM) ternary cathode materials cannot be improved simultaneously in the prior art. This invention provides a NCM ternary cathode material, its preparation method, its application, and a lithium-ion battery. The NCM ternary cathode material contains the dopant element Ce, and its surface is coated with CeO2. Furthermore, the Ce occupancy at the 3b positions in the lattice meets a specific range, significantly improving the structural stability of the cathode material. This results in lithium-ion batteries containing this cathode material exhibiting advantages such as high energy density, good rate performance, and high cycle capacity retention. Simultaneously, the preparation method of this cathode material is simple and easy to mass-produce.

[0007] To achieve the above objectives, the first aspect of the present invention provides a nickel-cobalt-manganese multi-element cathode material, characterized in that the nickel-cobalt-manganese multi-element cathode material contains the dopant element Ce, and the surface of the nickel-cobalt-manganese multi-element cathode material is coated with CeO2.

[0008] The Ce occupancy rate at 3b positions in the lattice obtained by XRD of the nickel-cobalt-manganese multi-element cathode material is Ce. 3b Satisfies: 2.1‰≤Ce 3b ≤6‰.

[0009] A second aspect of this invention provides a method for preparing a nickel-cobalt-manganese multi-element cathode material, characterized in that the preparation method includes the following steps:

[0010] (1) Prepare a mixed salt solution by preparing a nickel source, a cobalt source and a manganese source, prepare a precipitant solution, prepare a complexing agent solution, and prepare a cerium salt solution;

[0011] (2) Under nitrogen protection, a mixed salt solution, cerium compound I solution, complexing agent solution and precipitant solution are introduced into the reactor for co-precipitation reaction. After aging, filtration, washing and drying, nickel cobalt manganese hydroxide precursor is obtained.

[0012] (3) After mixing the nickel cobalt manganese hydroxide precursor, lithium source, and cerium compound II and performing a first sintering, the cathode material process product is obtained by crushing and sieving.

[0013] (4) After mixing the cathode material process product with cerium compound III and performing a second sintering, the nickel-cobalt-manganese multi-element cathode material is obtained by crushing and sieving.

[0014] The amounts of cerium compound I and cerium compound II added are based on a stoichiometric ratio of 0 < [n(Ce)1 + n(Ce)2] / [n(Ni) + n(Co) + n(Mn)] ≤ 0.03.

[0015] The amount of cerium compound III added is based on a stoichiometric ratio of 0 < n(Ce)3 / [n(Ni)+n(Co)+n(Mn)] ≤ 0.03.

[0016] A third aspect of the present invention provides a nickel-cobalt-manganese multi-element cathode material prepared by the above-described preparation method.

[0017] The fourth aspect of this invention provides an application of the above-mentioned nickel-cobalt-manganese multi-element cathode material in lithium-ion batteries.

[0018] The fifth aspect of the present invention provides a lithium-ion battery, characterized in that the lithium-ion battery comprises the above-mentioned nickel-cobalt-manganese multi-element cathode material.

[0019] Through the above technical solutions, the nickel-cobalt-manganese multi-element cathode material, its preparation method, and its application provided by the present invention achieve the following beneficial effects:

[0020] The nickel-cobalt-manganese (NCM) multi-element cathode material provided by this invention contains the dopant element Ce, and the surface of the NCM multi-element cathode material is coated with CeO2. Furthermore, the Ce occupancy rate at the 3b position of the NCM multi-element cathode material, as obtained by XRD, is Ce. 3b Meeting specific ranges enables the cathode material to possess a stable structure, thereby improving the rate performance and cycle performance of lithium-ion batteries containing this cathode material. In particular, the CeO2 coating on the surface of the cathode material can prevent side reactions between the electrolyte and the surface, and the F element in the crystal lattice can hinder the erosion of HF in the electrolyte, suppressing the damage of the material to the electrolyte during battery cycling, and further improving the structural stability of the cathode material during battery cycling.

[0021] Furthermore, the cathode material provided by this invention contains Ce 4+ Ce can be doped into the metal layer of ternary materials. The large radius of Ce ions can increase the interlayer spacing, making it easier for Li to insert and extract, thus improving rate performance; and Ce... 4+ The presence of this cathode material can improve the rate performance of lithium-ion batteries by introducing Li vacancies due to charge balance, thereby increasing Li ion mobility.

[0022] Furthermore, in the cathode material provided by this invention, the Ce-O bond strength in the crystal lattice is relatively strong, which can stabilize the O atoms in the crystal lattice, inhibit O extraction from the crystal lattice, and stabilize the material structure; the F element has a relatively strong bond strength with the metal, which can stabilize the metal element in the crystal lattice, inhibit the dissolution of the metal element, and further improve the structural stability and cycle performance. The Ce-doped crystal lattice... 4+ Based on charge balance, it can stabilize Ni in the cathode material. 2+ Since the average valence state of the metal layer is 3+, Ce 4+ Entering the metal layer allows Ni to... 2+The cathode material exists stably in the metal layer without migrating to the Li layer, thereby suppressing lithium-nickel mixing and improving the charge-discharge capacity, rate performance, and cycle performance of lithium-ion batteries containing this cathode material.

[0023] Furthermore, the nickel-cobalt-manganese multi-element cathode material provided by this invention is prepared through a two-step doping method. This preparation method is simple. Specifically, during the wet synthesis of the precursor, soluble cerium compound I is added to achieve uniform doping of the precursor. After sintering, it easily enters the crystal lattice. Furthermore, after a washing and filtration process, anions such as nitrate, sulfate, and chloride ions are removed and will not be introduced into the cathode material. Then, during the sintering stage, cerium compound II (preferably cerium fluoride) is introduced for doping. Some of it is introduced into the crystal lattice, while the excess remains between grain boundaries. Finally, cerium compound III (preferably cerium oxide) is used for coating to protect the material surface. By introducing Ce element through the precursor synthesis process and the two sintering processes, Ce can be uniformly doped into the crystal lattice, distributed between grain boundaries, and uniformly coated on the material surface, achieving the optimal doping and coating amount of Ce and avoiding segregation. This method is easily implemented industrially, has low cost, and is suitable for mass production. Attached Figure Description

[0024] Figure 1 Here is a SEM image of the cathode material prepared in Example 1;

[0025] Figure 2 The image shows the XRD pattern of the cathode material prepared in Example 1. The peaks marked with pentagrams are characteristic peaks of CeO2.

[0026] Figure 3 SEM image of the cathode material prepared in Comparative Example 1;

[0027] Figure 4 The graph shows the cycling performance of the cathode materials prepared in Example 1 and Comparative Example 1 at a 1C rate, where the test temperature was 45°C and the voltage range was 3.0-4.3V. Detailed Implementation

[0028] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0029] The first aspect of the present invention provides a nickel-cobalt-manganese ternary cathode material, characterized in that the nickel-cobalt-manganese ternary cathode material contains the dopant element Ce, and the surface of the nickel-cobalt-manganese ternary cathode material is coated with CeO2.

[0030] The Ce occupancy rate at the 3b position of the lattice was obtained by XRD for the nickel-cobalt-manganese multi-element cathode material. 3b Satisfies: 2.1‰≤Ce 3b ≤6‰.

[0031] In this invention, the nickel-cobalt-manganese multi-element cathode material contains the dopant element Ce, and the surface of the nickel-cobalt-manganese multi-element cathode material is coated with CeO2. 4+ It can be doped into the metal layer of ternary materials because Ce 4+ The larger ionic radius of Ce increases the interlayer spacing, making Li easier to insert and extract, thus improving rate performance; and Ce 4+ The presence of this cathode material can improve the rate performance of lithium-ion batteries by introducing Li vacancies due to charge balance, thereby increasing Li ion mobility.

[0032] Specifically, when the Ce occupancy rate at the 3b position of the nickel-cobalt-manganese multi-element cathode material is obtained by XRD, the Ce occupancy rate at the 3b position of the lattice is... 3b Meeting the aforementioned specific ranges enables the cathode material to possess a stable structure, thereby improving the rate performance and cycle performance of lithium-ion batteries containing this cathode material. Specifically, the CeO2 coating on the cathode material surface can prevent side reactions between the electrolyte and the surface, and the F element in the crystal lattice can hinder the erosion of HF in the electrolyte, suppressing electrolyte damage to the material during battery cycling, further improving the structural stability of the cathode material during battery cycling. Specifically, when the Ce occupancy at the 3b position of the crystal lattice is too low, it cannot play a role in charge balance and interlayer support; while when the occupancy is too high, the lack of electrochemical activity of Ce leads to a decrease in material capacity, and excessive Ce in the interlayer hinders lithium-ion channels, affecting rate performance.

[0033] Furthermore, 2.3‰≤Ce 3b ≤4‰.

[0034] According to the present invention, the Ni occupancy at position 3a in the lattice of the nickel-cobalt-manganese multi-element cathode material is obtained by XRD. 3a Satisfy: Ni 3a ≤2%.

[0035] In this invention, when the Ni occupancy rate at position 3a in the lattice of the nickel-cobalt-manganese multi-element cathode material is obtained by XRD, the Ni occupancy rate at position 3a is... 3a When the above specific range is met, the Ni content in the Li layer is relatively low, which will not hinder the insertion and extraction of Li ions, thereby ensuring that the lithium-ion battery containing this cathode material maintains excellent rate performance.

[0036] Furthermore, Ni 3a It ranges from 0.2% to 1.5%.

[0037] According to the present invention, the XRD spectrum of the nickel-cobalt-manganese multi-element cathode material has a CeO2 (111) characteristic peak at 2θ of 28°-29°.

[0038] In this invention, the XRD spectrum of the nickel-cobalt-manganese multi-element cathode material shows a characteristic peak of CeO2 at 2θ of 28°-29°, indicating that the material surface is coated with CeO2. As a result, the cathode material can inhibit electrolyte erosion and stabilize the surface structure, thereby protecting the internal structure from damage and improving the cycle performance of lithium-ion batteries containing the cathode material.

[0039] In this invention, the XRD spectrum of the nickel-cobalt-manganese multi-element cathode material shows a (003) characteristic peak of the cathode material at a 2θ of 18.5°-19.4°.

[0040] According to the present invention, the peak area G of the CeO2(111) characteristic peak obtained by XRD of the nickel-cobalt-manganese multi-element cathode material is... (111) The peak area G of the characteristic peak of nickel-cobalt-manganese multi-element cathode material (003) (003) The following relationship must be satisfied:

[0041] 2≤G (003) / G (111) ≤15.

[0042] In this invention, when the peak area G of the characteristic peak of CeO2(111) is... (111) The peak area G of the characteristic peak of nickel-cobalt-manganese multi-element cathode material (003) (003) When the above specific relationship is satisfied, it indicates that the CeO2 coating amount on the surface of the cathode material is within a suitable range. If the surface coating of CeO2 is too small, only a small number of spots can be coated, and most of the surface is still exposed to the electrolyte without protection, so it cannot achieve a comprehensive and uniform coating of the material. If the surface coating of CeO2 is too large, the electrochemically inactive CeO2 will reduce the charge and discharge capacity of the lithium-ion battery containing the cathode material, and the excessive CeO2 coating amount will result in an excessively thick coating layer on the surface of the cathode material, which will affect the insertion and extraction of lithium ions.

[0043] Furthermore, 3≤G (003) / G (111) ≤10.

[0044] According to the present invention, the cell parameter a obtained by XRD of the nickel-cobalt-manganese multi-element cathode material satisfies: 2.85nm≤a≤2.90nm.

[0045] According to the present invention, the cell parameter c of the nickel-cobalt-manganese multi-element cathode material obtained by XRD satisfies: 14.15nm≤c≤14.25nm.

[0046] In this invention, due to Ce4+ The ionic radius (0.104 nm) is greater than that of Ni. 2+ (0.069nm), Co 3+ (0.054nm) and Mn 4+ (0.053nm), Ce 4+ The interlayer structure provides support and leads to an increase in cell parameters a and c. In particular, when cell parameters a and c meet the above-mentioned range, the interlayer spacing of the cathode material can be increased, the lithium-ion mobility can be improved, and the rate performance of lithium-ion batteries containing the cathode material can be improved.

[0047] According to the present invention, the nickel-cobalt-manganese multi-element cathode material has the composition shown in Formula I:

[0048] Li a Ni x Mn y Co z Ce b O 2-c / 2 F c ·mCeO2 Formula I;

[0049] Where, 0.9≤a≤1.1, 0.5≤x<1, 0 <y<0.5,0<z<0.5,0<b≤0.03,0<c<0.05,0<m≤0.03。

[0050] In this invention, when the nickel-cobalt-manganese multi-element cathode material has the composition shown in Formula I, that is, the multi-element cathode material contains a specific amount of doping element Ce and a specific amount of coating layer CeO2, the cathode material has a stable structure, thereby improving the rate performance and cycle performance of lithium-ion batteries containing the cathode material.

[0051] Furthermore, 1.02 ≤ a ≤ 1.06, 0.5 ≤ x < 1, 0 <y<0.5,0<z<0.5,,0<b≤0.02,0<c<0.02,0<m≤0.02。

[0052] A second aspect of this invention provides a method for preparing a nickel-cobalt-manganese multi-element cathode material, characterized in that the preparation method includes the following steps:

[0053] (1) Prepare a mixed salt solution by preparing a nickel source, a cobalt source and a manganese source, prepare a precipitant solution, prepare a complexing agent solution, and prepare a cerium salt solution;

[0054] (2) Under nitrogen protection, a mixed salt solution, cerium compound I solution, complexing agent solution and precipitant solution are introduced into the reactor for co-precipitation reaction. After aging, filtration, washing and drying, nickel cobalt manganese hydroxide precursor is obtained.

[0055] (3) After mixing the nickel cobalt manganese hydroxide precursor, lithium source, and cerium compound II and performing a first sintering, the cathode material process product is obtained by crushing and sieving.

[0056] (4) After mixing the cathode material process product with cerium compound III and performing a second sintering, the nickel-cobalt-manganese multi-element cathode material is obtained by crushing and sieving.

[0057] The amounts of cerium compound I solution and cerium compound II added are in a stoichiometric ratio of 0 < [n(Ce)1 + n(Ce)2] / [n(Ni) + n(Co) + n(Mn)] ≤ 0.03.

[0058] The amount of cerium compound III added is based on a stoichiometric ratio of 0 < n(Ce)3 / [n(Ni)+n(Co)+n(Mn)] ≤ 0.03.

[0059] In this invention, the preparation method of the nickel-cobalt-manganese (NCM) multi-element cathode material involves a two-step doping process. First, soluble cerium compound I is added during the wet synthesis of the precursor to achieve uniform doping. After sintering, this doping easily penetrates the crystal lattice, and after washing and filtration, anions such as nitrate, sulfate, and chloride are removed and not introduced into the cathode material. Second, cerium compound II is introduced during the sintering stage. Some cerium is incorporated into the crystal lattice, while the excess remains between grain boundaries. Finally, cerium compound III is used for coating to protect the material surface.

[0060] That is, by introducing Ce element through precursor synthesis process and two sintering processes, Ce can be uniformly doped into the lattice, distributed between grain boundaries, and uniformly coated on the material surface. Furthermore, by controlling the amount of Ce element added in each step, the optimal doping and coating amount of Ce can be achieved, avoiding segregation, and finally obtaining the nickel-cobalt-manganese multi-element cathode material described in the first aspect of the present invention.

[0061] Furthermore, the above preparation method is relatively easy to implement industrially, has low cost, and is suitable for mass production.

[0062] Furthermore, when the amounts of cerium compound I and cerium compound II are added in a stoichiometric ratio of 0.001 < [n(Ce)1 + n(Ce)2] / [n(Ni) + n(Co) + n(Mn)] ≤ 0.02, the resulting cathode material exhibits a suitable occupancy of Ce at the 3b position of the crystal lattice, thereby suppressing lithium-nickel mixing and improving the structural stability of the cathode material.

[0063] Furthermore, when the amount of cerium compound III added is stoichiometric in the form of 0.001 < n(Ce)3 / [n(Ni) + n(Co) + n(Mn)] ≤ 0.02, the surface of the cathode material has a suitable amount of CeO2 coating, which can protect the internal structure of the cathode material and prevent it from being corroded by the electrolyte during battery cycling, without affecting the charge and discharge capacity of the lithium-ion battery or the insertion and extraction of lithium ions.

[0064] In one specific embodiment of the present invention, the amount of cerium compound I added is such that the stoichiometric ratio is 0 < n(Ce)1 / [n(Ni)+n(Co)+n(Mn)]≤0.02, and the amount of cerium compound II added is such that the stoichiometric ratio is 0 < n(Ce)2 / [n(Ni)+n(Co)+n(Mn)]≤0.02.

[0065] In this invention, by controlling the amount of Ce added in the nickel-cobalt-manganese hydroxide precursor and the cathode material process product to meet the above-mentioned range, Ce can be uniformly doped into the bulk phase of the material without segregation or local enrichment, thereby significantly improving the structural stability of the cathode material prepared therefrom.

[0066] Furthermore, the amount of cerium compound I added is such that the stoichiometric ratio is 0.0005 < n(Ce)1 / [n(Ni)+n(Co)+n(Mn)]≤0.01, and the amount of cerium compound II added is such that the stoichiometric ratio is 0.0005 < n(Ce)2 / [n(Ni)+n(Co)+n(Mn)]≤0.01.

[0067] According to the present invention, the cerium compound I is selected from at least one of cerium sulfate, cerium chloride, cerium nitrate, cerium acetate, cerium hydroxide, and cerium fluoride.

[0068] According to the present invention, the cerium compound II is selected from at least one of cerium acetate, cerium hydroxide and cerium fluoride.

[0069] According to the present invention, the cerium compound III is selected from at least one of cerium acetate, cerium hydroxide, cerium oxide and cerium fluoride.

[0070] In one specific embodiment of the present invention, the cerium compound II is cerium fluoride, and the cerium compound III is cerium oxide.

[0071] In this invention, the types of nickel, cobalt, and manganese sources are not particularly limited, and can be conventional types in the art. For example, the nickel, cobalt, and manganese sources are each independently selected from at least one of sulfate, chloride, nitrate, and acetate. The concentration of the mixed salt solution is also not particularly limited and can be adjusted according to conventional methods in the art; for example, the concentration of the mixed salt solution is 1-3 mol / L.

[0072] In this invention, there is no particular limitation on the type of precipitant; it can be any conventional precipitant in the art, for example, the precipitant is selected from sodium hydroxide and / or potassium hydroxide. There is also no particular limitation on the concentration of the precipitant solution; it can be adjusted according to conventional methods in the art.

[0073] In this invention, there is no particular limitation on the type of complexing agent; it can be a conventional complexing agent in the art, such as at least one selected from ammonia, disodium ethylenediaminetetraacetate, ammonium nitrate, ammonium chloride, and ammonium sulfate. There is also no particular limitation on the concentration of the complexing agent solution; it can be adjusted according to conventional methods in the art.

[0074] In this invention, there is no particular limitation on the type of lithium source, which can be a conventional type of lithium source in the art, such as the lithium source being selected from at least one of lithium carbonate, lithium hydroxide, lithium oxide and lithium acetate.

[0075] According to the present invention, the amount of lithium source added is 0.9≤n(Li) / [n(Ni)+n(Co)+n(Mn)]≤1.1 according to the stoichiometric ratio, preferably 1.02≤n(Li) / [n(Ni)+n(Co)+n(Mn)]≤1.06.

[0076] According to the present invention, the conditions for the coprecipitation reaction include: a reaction temperature of 40-70°C, a reaction time of 5-20 h, a pH of 11-13, and a stirring speed of 50-90 rpm.

[0077] Furthermore, the conditions for the coprecipitation reaction include: a reaction temperature of 50-65℃, a reaction time of 10-20h, a pH of 11.5-12.5, and a stirring speed of 60-80rpm.

[0078] According to the present invention, the conditions for the first sintering include: being carried out in the presence of air and / or oxygen, a sintering temperature of 700-1200°C, and a sintering time of 5-30 h.

[0079] Furthermore, the conditions for the first sintering include: being carried out in the presence of air and / or oxygen, a sintering temperature of 700-1100℃, and a sintering time of 10-30h.

[0080] According to the present invention, the conditions for the second sintering include: being carried out in the presence of air and / or oxygen, a sintering temperature of 500-900°C, and a sintering time of 3-15 h.

[0081] Furthermore, the conditions for the second sintering include: being carried out in the presence of air and / or oxygen, a sintering temperature of 500-800℃, and a sintering time of 6-10h.

[0082] In this invention, the mixing in step (3) is mechanical mixing, without the addition of solvent.

[0083] In this invention, the aging, filtration, washing, and drying in step (2) and the crushing and sieving in steps (3) and (4) can all be carried out in accordance with conventional methods known to those skilled in the art.

[0084] A third aspect of the present invention provides a nickel-cobalt-manganese multi-element cathode material prepared by the above-described preparation method.

[0085] The fourth aspect of this invention provides an application of the above-mentioned nickel-cobalt-manganese multi-element cathode material in lithium-ion batteries.

[0086] The fifth aspect of the present invention provides a lithium-ion battery, characterized in that the lithium-ion battery comprises the above-mentioned nickel-cobalt-manganese multi-element cathode material.

[0087] In the following examples, all raw materials are commercially available unless otherwise specified.

[0088] Unless otherwise specified, the room temperature referred to in this invention is 25±2℃.

[0089] In the following examples and comparative examples, the relevant parameters were obtained through testing using the following methods:

[0090] (1) Morphological test: obtained by scanning electron microscope of model S-4800 of Hitachi, Japan;

[0091] (2) XRD test: obtained by using a Smart Lab 9KW X-ray diffractometer from Rigaku Corporation, Japan;

[0092] (3) Electrochemical performance testing:

[0093] In the following examples and comparative examples, the electrochemical performance of the multi-element cathode material was tested using a 2025 coin cell.

[0094] The specific manufacturing process of the 2025 coin cell is as follows:

[0095] Electrode preparation: A homogeneous slurry is formed by thoroughly mixing a multi-element positive electrode material, acetylene black, and polyvinylidene fluoride (PVDF) at a mass ratio of 95:3:2 with an appropriate amount of N-methylpyrrolidone (NMP). The slurry is coated onto aluminum foil and dried at 120°C for 12 hours. Then, it is pressed into a positive electrode sheet with a diameter of 12 mm and a thickness of 120 μm using a pressure of 100 MPa. The loading of the multi-element positive electrode material is 15-16 mg / cm³. 2 .

[0096] Battery Assembly: In an argon-filled glove box with both water and oxygen content less than 5 ppm, the positive electrode, separator, negative electrode, and electrolyte were assembled into a 2025 coin cell and then left to stand for 6 hours. The negative electrode used a 17 mm diameter, 1 mm thick lithium metal sheet; the separator used a 25 μm thick polyethylene porous membrane (Celgard 2325); and the electrolyte used was a 1 mol / L mixture of equal parts LiPF6, ethylene carbonate (EC), and diethyl carbonate (DEC).

[0097] Electrochemical performance testing:

[0098] In the following examples and comparative examples, the electrochemical performance of the 2025 coin cell was tested using the Shenzhen Xinwei Battery Testing System, with a charge / discharge current density of 200 mA / g at 0.1C.

[0099] The charge / discharge voltage range was controlled between 3.0 and 4.3V. At room temperature, the coin cell was charged and discharged at 0.1C to evaluate the initial discharge specific capacity of the multi-element cathode material.

[0100] Cyclic performance test: The charge and discharge voltage range was controlled at 3.0-4.3V. At a constant temperature of 45℃, the coin cell was charged and discharged twice at 0.1C and then charged and discharged 80 times at 1C to evaluate the high-temperature capacity retention of the multi-element cathode material.

[0101] Rate performance testing: The charge / discharge voltage range was controlled at 3.0-4.3V. At room temperature, the coin cell was cycled twice at 0.1C, and then once each at 0.2C, 0.33C, 0.5C, and 1C. The rate performance of the multi-element cathode material was evaluated by the ratio of the initial discharge specific capacity at 0.1C to the discharge specific capacity at 1C. The initial discharge specific capacity at 0.1C is the discharge specific capacity of the coin cell in the first cycle, and the discharge specific capacity at 1C is the discharge specific capacity of the coin cell in the sixth cycle.

[0102] Example 1

[0103] (1) Using nickel sulfate, cobalt sulfate and manganese sulfate as raw materials, a homogeneous nickel, cobalt and manganese salt mixed solution of 2 mol / L was prepared according to the molar ratio Ni:Co:Mn=80:10:10. A 0.2 mol / L Ce2(SO4)3 solution was prepared, an 8 mol / L NaOH solution was prepared as a precipitant, and 25 wt% ammonia water was used directly as a complexing agent.

[0104] Under nitrogen protection, the above solution was introduced into the reactor in a parallel flow, with n(Ce)1:[n(Ni)+n(Co)+n(Mn)] = 0.004:1, stirring speed 70 rpm, reaction temperature maintained at 55℃, and pH value 12.3 for 20 h. After pressure filtration, washing, drying, and sieving, the nickel-cobalt-manganese hydroxide precursor was obtained. This precursor consisted of spherical or near-spherical single particles with a loose structure.

[0105] (2) Lithium hydroxide, cerium fluoride, and nickel cobalt manganese hydroxide precursors were uniformly mixed in a ratio of n(Li):n(Ce)2:[n(Ni)+n(Co)+n(Mn)]=1.04:0.002:1, sintered at 900℃ for 12h in an oxygen atmosphere, naturally cooled to room temperature, crushed and sieved to obtain the cathode material process product.

[0106] (3) The cathode material and cerium oxide were uniformly mixed in a ratio of n(Ce)3:[n(Ni)+n(Co)+n(Mn)]=0.01:1, sintered at 720℃ for 10h in an oxygen atmosphere, naturally cooled to room temperature, crushed and sieved to obtain the cathode material Li. 1.04 (Ni 0.8 Co 0.1 Mn 0.1 Ce 0.006 )O 1.994 F 0.012 • 0.01CeO2. Cell parameters

[0107] Examples 2-9

[0108] The method of Example 1 was followed, except that the formulation and process parameters were different, as shown in Table 1. All other aspects were the same as in Example 1, and a multi-element cathode material was prepared.

[0109] Comparative Examples 1-5

[0110] The method of Example 1 was followed, except that the formulation and process parameters were different, as shown in Table 1 (continued). All other aspects were the same as in Example 1, and a multi-element cathode material was prepared.

[0111] Comparative Example 6

[0112] The method of Example 1 is different in that: in step (1), cerium oxide is used instead of Ce2(SO4)3 solution, and cerium oxide is directly added to the reaction vessel;

[0113] In step (2), cerium nitrate is used instead of cerium fluoride. Other formulations and process parameters are shown in Table 1 (continued).

[0114] Comparative Example 7

[0115] The method is the same as in Example 1, except that Ce2(SO4)3 is not added in step (1);

[0116] No cerium fluoride is added in step (2);

[0117] In step (3), cerium nitrate is used instead of cerium oxide, and the uniformly mixed mixture is ultrasonicated in ethanol for 1.5 h, then ground, and sintered at 650 °C for 5 h to obtain the positive electrode material.

[0118] Other formulations and process parameters are shown in Table 1 (continued).

[0119] Table 1

[0120]

[0121] Table 1 (continued)

[0122]

[0123]

[0124] Table 1 (continued)

[0125]

[0126] The cathode material compositions of the embodiments and comparative examples are shown in Table 2.

[0127] Table 2

[0128]

[0129]

[0130] Test case

[0131] (1) Morphological test

[0132] The present invention tested scanning electron microscope images of the cathode materials prepared in the above embodiments and comparative examples, such as... Figure 1 , 3 As shown, from Figure 1 and Figure 3 It can be seen that the surface of the positive electrode material obtained in Example 1 is uniformly coated with CeO2; from Figure 3 It can be seen that the cathode material obtained in Comparative Example 1 has a smooth surface and no coating.

[0133] (2) XRD

[0134] The present invention tested the XRD of the cathode materials prepared in the above embodiments and comparative examples. Figure 2 The image shows the XRD pattern of the cathode material prepared in Example 1. Figure 2It can be seen that the XRD spectrum shows a CeO2 (111) characteristic peak at 2θ (28°-29°), indicating that the material surface has a CeO2 coating layer. Table 3 shows the peak positions of the (003) characteristic peaks of the cathode material at 2θ. (003) and peak integral area G (003) The peak position of the (111) characteristic peak of CeO2 is 2θ. (111) and peak integral area G (111) The integral area of ​​the characteristic peak of the cathode material (003) is G. (003) The integral area G of the (111) characteristic peak of CeO2 (111) The ratio of G (003) / G (111) The cell parameters a and c were determined, and the Ni occupancy at position 3a in the lattice was obtained by fine-tuning. 3a Ce occupancy at 3b position in the lattice 3b .

[0135] Table 3

[0136]

[0137]

[0138] (3) Electrochemical performance testing

[0139] The present invention tested the electrochemical performance of the cathode materials prepared in the above embodiments and comparative examples, including the 0.1C initial discharge specific capacity, 1C discharge specific capacity, rate performance and cycle performance. The specific test results are shown in Table 4. Figure 4 The graphs show the cycling performance of the cathode materials prepared in Example 1 and Comparative Example 1 at a 1C rate, where the test temperature was 45°C and the voltage range was 3-4.3V. Figure 4 It can be seen that Example 1 has significantly better cycle capacity and cycle performance than Comparative Example 1 at 45°C.

[0140] Table 4

[0141]

[0142] As can be seen from Tables 2, 3, and 4, compared to Comparative Examples 1-7, the cathode materials prepared by Examples 1-9 of the present invention contain the dopant element Ce, and the surface of the nickel-cobalt-manganese multi-element cathode material is coated with CeO2. Furthermore, the Ce occupancy rate at the 3b position of the nickel-cobalt-manganese multi-element cathode material obtained by XRD is Ce. 3b Within the scope defined by this invention, when the above-mentioned cathode material is used in lithium-ion batteries, it can significantly improve and enhance the first discharge specific capacity, rate performance, and cycle performance of lithium-ion batteries.

[0143] Furthermore, compared to Examples 7-9, the content of the doping element Ce and the coating amount of CeO2 in the cathode materials prepared in Examples 1-6 are within the preferred range. When this cathode material is used in lithium-ion batteries, the lithium-ion batteries can simultaneously possess high initial discharge specific capacity, rate performance and cycle performance, resulting in the best overall performance of the battery.

[0144] Furthermore, as can be seen from Examples 1-2, compared to doping Ce in the sintering stage, doping Ce in the precursor stage in a liquid phase makes it easier for Ce to enter the crystal lattice. When the doping amount is too large, Ce cannot completely enter the crystal lattice and remains between grain boundaries and on the surface.

[0145] Furthermore, compared to Example 1, Example 2 has less doping in the precursor stage and more doping during sintering, resulting in less Ce entering the crystal lattice, which reduces the rate performance of the lithium-ion battery containing this cathode material; in Example 3, the total Ce content of the doped and coated elements increases, and the first discharge specific capacity of the lithium-ion battery containing this cathode material decreases slightly, but the rate and cycle performance are slightly better; in Example 4, the Ce content of the doping element is high, and the CeO2 content of the coating layer is low, which results in slightly better rate performance but slightly worse cycle performance of the lithium-ion battery containing this cathode material.

[0146] Therefore, when the specific range defined by the present invention is met, the increase of the doping element Ce can play a supporting role between the lattice layers, making it easier for Li ions to insert and extract, thereby improving the rate performance of lithium-ion batteries containing the cathode material. The increase of the content of the coating layer CeO2 can improve the cycle performance of lithium-ion batteries containing the cathode material.

[0147] Furthermore, as can be seen from Examples 5 and 6, the same effect can be obtained for different NCM compositions, except that the characteristic peak positions of the cathode materials with different compositions are slightly different.

[0148] Furthermore, in Example 7, due to the relatively low content of the dopant element Ce and the relatively low coating amount of CeO2 in the cathode material, G (003) / G (111) Larger, Ce 3b The smaller size of the cathode material makes it less effective at suppressing lithium-nickel mixing, resulting in a decrease in the rate performance and cycle performance of lithium-ion batteries containing this cathode material.

[0149] Compared to Example 1, the cathode material prepared in Example 8 has a larger CeO2 coating, resulting in higher G content. (003) / G (111)The smaller and excessive CeO2 content leads to an increase in the number of inert elements introduced into the cathode material, resulting in a slight decrease in the initial discharge specific capacity of the lithium-ion battery containing this cathode material. Furthermore, due to the large amount of CeO2 coating and the thicker surface coating layer, the conduction of lithium ions on the surface of the cathode material is hindered, resulting in a slight decrease in the rate performance of the lithium-ion battery containing this cathode material.

[0150] Compared with Example 1, the cathode material prepared in Example 9 has a higher content of the dopant element Ce, which leads to an increase in the number of inert elements introduced into the cathode material. This results in a slight decrease in the first discharge specific capacity of the lithium-ion battery containing this cathode material. Furthermore, Ce has a higher occupancy rate at the 3b position of the crystal lattice, which hinders the conduction of lithium ions on the surface of the cathode material. This results in a slight decrease in the rate performance of the lithium-ion battery containing this cathode material.

[0151] Comparative Examples 1-3 prepared cathode materials that did not contain a CeO2 coating layer and lacked the (111) characteristic peak of CeO2, resulting in poor cycle performance of lithium-ion batteries containing the above cathode materials.

[0152] Specifically, compared with Example 1, the cathode material prepared in Comparative Example 1 does not contain the dopant element Ce and does not contain the coating layer CeO2. The lithium-nickel mixture is serious, which makes the rate performance and cycle performance of the lithium-ion battery containing this cathode material poor.

[0153] In Comparative Example 2, Ce element was introduced only in the precursor stage. The surface of the resulting cathode material was not coated with CeO2 and the Ce content at the 3b position in the lattice was low, making it impossible to achieve uniform doping. This resulted in poor rate performance and cycle performance of the lithium-ion battery containing this cathode material.

[0154] Comparative Example 3 introduced Ce element only in the first sintering stage. The surface of the obtained cathode material was not coated with CeO2 and the Ce occupancy of the 3b position in the lattice was small, which could not achieve uniform doping. As a result, the rate performance and cycle performance of the lithium-ion battery containing this cathode material were poor.

[0155] In Comparative Example 4, Ce element was introduced only in the secondary sintering stage. The resulting cathode material did not contain the dopant element Ce, and was only coated with CeO2. This could not suppress lithium-nickel mixing, resulting in poor rate performance of lithium-ion batteries containing this cathode material and poorer cycle performance than Example 1.

[0156] In Comparative Example 5, the content of the doping element Ce and the content of the coating layer CeO2 are excessive, G (003) / G (111)The small amount of Ce leads to a decrease in the first discharge specific capacity and a deterioration in the rate performance of lithium-ion batteries containing this cathode material. This indicates that a small amount of Ce doping supports the interlayer, making it easier for Li ions to insert and extract, and allowing the material capacity to be utilized more easily. However, excessive Ce doping into the material will hinder the Li ion channels, resulting in a decrease in the rate performance of the battery. Furthermore, Ce has no electrochemical activity, and adding too much Ce element to the doping coating will affect the first discharge specific capacity of the battery.

[0157] Comparative Example 6 added cerium oxide to the precursor. Cerium oxide is insoluble in water, so the cerium oxide introduced in the precursor stage cannot be doped into the crystal lattice. While adding a significant amount of cerium nitrate during the sintering stage allows for partial doping into the crystal lattice, it introduces inert nitrate ions into the material, resulting in lower capacity. Furthermore, Comparative Example 6 did not perform surface coating. Some of the cerium nitrate added during the sintering stage remained, but most remained at the grain boundaries. Excess cerium nitrate was converted to CeO2 and remained at the grain boundaries, making it difficult to uniformly coat the material surface. This led to poorer cycle performance of the battery containing this cathode material.

[0158] In Comparative Example 7, no cerium was doped during the preparation of the cathode material; only cerium nitrate was coated on the surface, with a small portion entering the surface lattice, failing to achieve bulk doping. Furthermore, severe lithium-nickel mixing occurred during the sintering process of the cathode material, which the coating could not effectively suppress, resulting in poor rate and cycle performance of the battery containing this cathode material. The introduction of inert nitrate ions into the material also led to a low initial discharge specific capacity. Moreover, grinding the cathode material in ethanol weakened the interparticle bonding, damaging the material structure and further reducing the battery's cycle retention rate.

[0159] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A nickel-cobalt-manganese multi-element cathode material, characterized in that, The nickel-cobalt-manganese multi-element cathode material contains the dopant element Ce, and the surface of the nickel-cobalt-manganese multi-element cathode material is coated with CeO2. The Ce occupancy rate at the 3b position of the lattice was obtained by XRD for the nickel-cobalt-manganese multi-element cathode material. 3b Satisfies: 2.1‰≤Ce 3b ≤6‰; The peak area G of the (111) characteristic peak of CeO2 obtained by XRD for the nickel-cobalt-manganese multi-element cathode material (111) The peak area G of the (003) characteristic peak of nickel-cobalt-manganese multi-element cathode material (003) The following relationship must be satisfied: 3≤G (003) / G (111) ≤10; The nickel-cobalt-manganese multi-element cathode material has the composition shown in Formula I: Li a Ni x Mn y Co z Ce b O 2-c / 2 F c ·mCeO2 of formula I; Where, 0.9≤ a ≤1.1, 0.7≤ x <1, 0< y <0.5, 0< z <0.5, 0< b ≤0.03, 0< c <0.05, 0< m ≤0.

03.

2. The nickel-cobalt-manganese multi-element cathode material according to claim 1, wherein, 2.3‰≤Ce 3b ≤4‰。 3. The nickel-cobalt-manganese multi-element cathode material according to claim 1 or 2, wherein, The Ni occupancy at position 3a in the lattice of the nickel-cobalt-manganese multi-element cathode material was obtained by XRD. 3a Satisfy: Ni 3a ≤2%.

4. The nickel-cobalt-manganese multi-element cathode material according to claim 3, wherein, The Ni occupancy at position 3a in the lattice of the nickel-cobalt-manganese multi-element cathode material was obtained by XRD. 3a Satisfy: Ni 3a It ranges from 0.2% to 1.5%.

5. The nickel-cobalt-manganese multi-element cathode material according to claim 1 or 2, wherein, The XRD spectrum of the nickel-cobalt-manganese multi-element cathode material shows a CeO2 (111) characteristic peak at 2θ, 28°-29°.

6. The nickel-cobalt-manganese multi-element cathode material according to claim 1 or 2, wherein, The cell parameter α of the nickel-cobalt-manganese multi-element cathode material obtained by XRD satisfies: 2.85nm ≤ α ≤ 2.90nm; And / or, the cell parameter c of the nickel-cobalt-manganese multi-element cathode material obtained by XRD satisfies: 14.15nm ≤ c ≤ 14.25nm.

7. A method for preparing a nickel-cobalt-manganese multi-element cathode material according to any one of claims 1-6, characterized in that, The preparation method includes the following steps: (1) Prepare a mixed salt solution by preparing the nickel source, cobalt source and manganese source, prepare a precipitant solution by preparing the precipitant solution, prepare a complexing agent solution by preparing the complexing agent solution, and prepare a cerium salt solution by preparing the cerium salt solution; (2) Under nitrogen protection, a mixed salt solution, cerium compound I solution, complexing agent solution and precipitant solution are introduced into a reaction vessel for co-precipitation reaction. After aging, filtration, washing and drying, nickel cobalt manganese hydroxide precursor is obtained. (3) After mixing the nickel cobalt manganese hydroxide precursor, lithium source, and cerium compound II and performing the first sintering, the cathode material process product is obtained after crushing and sieving. (4) After mixing the cathode material with cerium compound III and performing a second sintering, the cathode material is crushed and sieved to obtain a nickel-cobalt-manganese multi-element cathode material; The amounts of cerium compound I and cerium compound II added are in a stoichiometric ratio of 0 < [n(Ce)1 + n(Ce)2] / [n(Ni) + n(Co) + n(Mn)] ≤ 0.

03. The amount of cerium compound III added is based on a stoichiometric ratio of 0 < n(Ce)3 / [n(Ni)+n(Co)+n(Mn)] ≤ 0.03; The cerium compound II is cerium fluoride, and the cerium compound III is cerium oxide.

8. The preparation method according to claim 7, wherein, The amounts of cerium compound I and cerium compound II added are in a stoichiometric ratio of 0.001 < [n(Ce)1 + n(Ce)2] / [n(Ni) + n(Co) + n(Mn)] ≤ 0.

02. And / or, the amount of cerium compound III added is in the stoichiometric ratio of 0.001 < n(Ce)3 / [n(Ni)+n(Co)+n(Mn)] ≤ 0.

02.

9. The preparation method according to claim 7 or 8, wherein, The amount of cerium compound I added is such that the stoichiometric ratio is 0 < n(Ce)1 / [n(Ni)+n(Co)+n(Mn)]≤0.02; And / or, the amount of cerium compound II added is based on a stoichiometric ratio of 0 < n(Ce)2 / [n(Ni)+n(Co)+n(Mn)] ≤ 0.

02.

10. The preparation method according to claim 9, wherein, The amount of cerium compound I added is based on a stoichiometric ratio of 0.0005 < n(Ce)1 / [n(Ni)+n(Co)+n(Mn)] ≤ 0.01; And / or, the amount of cerium compound II added is in the stoichiometric ratio of 0.0005 < n(Ce)2 / [n(Ni)+n(Co)+n(Mn)] ≤ 0.

01.

11. The preparation method according to claim 7 or 8, wherein, The cerium compound I is selected from at least one of cerium sulfate, cerium chloride, cerium nitrate, cerium acetate, cerium hydroxide, and cerium fluoride; And / or, the amount of lithium source added is based on a stoichiometric ratio of 0.9≤n(Li) / [n(Ni)+n(Co)+n(Mn)]≤1.

1.

12. The preparation method according to claim 11, wherein, The amount of lithium source added is based on a stoichiometric ratio of 1.02≤n(Li) / [n(Ni)+n(Co)+n(Mn)]≤1.

06.

13. The preparation method according to claim 7 or 8, wherein, The conditions for the coprecipitation reaction include: a reaction temperature of 40-70℃, a reaction time of 5-20h, a pH of 11-13, and a stirring speed of 50-90rpm. And / or, the conditions for the first sintering include: being carried out in the presence of air and / or oxygen, a sintering temperature of 700-1200°C, and a sintering time of 5-30 h; And / or, the conditions for the second sintering include: being carried out in the presence of air and / or oxygen, a sintering temperature of 500-900°C, and a sintering time of 3-15 hours.

14. A nickel-cobalt-manganese multi-element cathode material prepared by the preparation method according to any one of claims 7-12.

15. The application of the nickel-cobalt-manganese multi-element cathode material according to any one of claims 1-6 and 14 in lithium-ion batteries.

16. A lithium-ion battery, characterized in that, The lithium-ion battery includes the nickel-cobalt-manganese multi-element cathode material as described in any one of claims 1-6 and 14.

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