Coated modified high nickel positive electrode material and preparation method thereof, and lithium ion battery

Abstract

The present invention belongs to the technical field of lithium-ion battery materials, and discloses a coated and modified high-nickel positive electrode material and a preparation method thereof, and a lithium-ion battery. The coated and modified high-nickel positive electrode material comprises a positive electrode material matrix and a coating layer located on at least part of the surface of the positive electrode material matrix; the chemical formula of the positive electrode material matrix is ​​LiNi x Co y Mn z M p O 2 The material of the coating layer is Ca 2.4 Sr 0.6 Co 4 O 9 The coating layer material and the cathode material matrix are mixed and sintered to obtain the coated modified high nickel cathode material. The coating process is simple, and the coated modified high nickel cathode material improves the high temperature cycle performance of the battery.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion battery materials, and in particular relates to the coating modification of high-nickel positive electrode materials. Background Art

[0002] As an important energy storage device, lithium-ion batteries have great advantages over other batteries and have received widespread attention. In a high temperature environment, the chemical reaction rate inside the battery will accelerate, which may cause the battery to overheat or even become dangerous. With the development of battery technology, more and more manufacturers are paying attention to the high-temperature cycle performance of batteries. Modifying the positive electrode material of the battery is one of the main ways to improve the high-temperature cycle performance of the battery. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides a coated and modified high-nickel positive electrode material and a preparation method and application thereof.

[0004] To achieve the above objectives, the present invention provides the following specific technical solutions.

[0005] In a first aspect, the present invention provides a coated and modified high-nickel positive electrode material, comprising a positive electrode material substrate and a coating layer located on at least a portion of the surface of the positive electrode material substrate; the chemical formula of the positive electrode material substrate is LiNi x Co y Mn z M p O2, 0.7≤x<1, 0≤y≤0.3, 0<z≤0.3, 0≤p≤0.1, x+y+z+p =1; M is a doping element, wherein M is any one of W, Mg, Mo, Zr, Co, Ni, V, Cr, Ge, Nb, Al, Sr or Ti, or a combination of two or more thereof, and the material of the coating layer is Ca 2.4 Sr 0.6 Co4O9.

[0006] In a further preferred embodiment, the mass of the material of the coating layer is 0.6%-3% of the mass of the positive electrode material matrix.

[0007] In a second aspect, the present invention provides a method for preparing the above-mentioned coated modified high-nickel positive electrode material, comprising:

[0008] The coating layer material and the positive electrode material matrix are mixed and sintered to obtain the product.

[0009] In a further preferred embodiment, the sintering temperature is 500-800° C. and the sintering time is 5-8 hours.

[0010] In a third aspect, the present invention provides a lithium-ion battery comprising the above-mentioned coated and modified high-nickel positive electrode material.

[0011] The above one or more technical solutions of the present invention have at least one of the following beneficial effects:

[0012] The coating process is simple, easy to operate, and easy to industrialize and use on a large scale.

[0013] The coated and modified high-nickel positive electrode material improves the high-temperature cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 For Li 1.1 Ni 0.9 Co 0.06 Mn 0.04 SEM image of O2 positive electrode material.

[0015] Figure 2 This is the SEM image of the coated and modified positive electrode material obtained in Example 1.

[0016] Figure 3 The coated and modified positive electrode material obtained in Example 1-5, and Li 1.1 Ni 0.9 Co 0.06 Mn 0.04 O2 cathode material, Li 1.25 Ni 0.9 Mn 0.1 O2 cathode material, Li 1.01 Ni 0.83 Mn 0.17 Cycling performance diagram of batteries assembled with O2 positive electrode materials at 45°C.

[0017] Figure 4 The cycling performance diagram at 45°C of the battery assembled with the coated and modified positive electrode materials obtained in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0018] In order to improve the high temperature cycle performance of lithium ion batteries, the present invention studies the coating modification of high nickel positive electrode materials.

[0019] In a first aspect, the present invention provides a coated and modified high-nickel positive electrode material, comprising a positive electrode material substrate and a coating layer located on at least a portion of the surface of the positive electrode material substrate; the chemical formula of the positive electrode material substrate is LiNi x Co y Mn z M p O2, 0.7≤x<1, 0≤y≤0.3, 0<z≤0.3, 0≤p≤0.1, x+y+z+p=1; M is a doping element, wherein M is any one of W, Mg, Mo, Zr, Co, Ni, V, Cr, Ge, Nb, Al, Sr or Ti, or a combination of two or more thereof, and the material of the coating layer is Ca2.4 Sr 0.6 Co4O9.

[0020] Preferably, the mass of the material of the coating layer is 0.6%-3% of the mass of the positive electrode material matrix.

[0021] Material of coating layer Ca 2.4 Sr 0.6 Co4O9 has high electronic conductivity, electrical properties and good thermal stability. At high temperatures, the material's composition and crystal structure are more stable, with fewer lattice defects and fewer microcracks caused by high temperatures. Coating this material on the surface of high-nickel positive electrode materials can improve the thermal stability of the positive electrode materials, effectively resist surface cracking and material deterioration caused by high temperatures, and make the battery have better high-temperature cycle stability; due to its high electronic conductivity and electrical properties, it also improves the electron transmission and lithium ion transmission performance of the positive electrode materials. At the same time, the coating layer material Ca 2.4 Sr 0.6 Co in Co4O9 participates in some electrochemical reactions, which can inhibit the mixing of nickel and lithium, improve the ion conductivity and stability of the material, and inhibit phase change; moreover, Sr and Ca in the coating layer work together to promote grain growth, reduce the lithiation temperature, alleviate the disordered state of Li / Ni and stabilize the lattice. In addition, the coating layer can also reduce the interface resistance and inhibit lithium dendrites, which is beneficial to Li + Ion transfer across the interface.

[0022] In a second aspect, the present invention provides a method for preparing the above-mentioned coated modified high-nickel positive electrode material, comprising:

[0023] The coating layer material and the positive electrode material matrix are mixed and sintered to obtain the product.

[0024] Preferably, the sintering temperature is 500-800°C, for example, 500°C, 600°C, 700°C, 800°C; the sintering time is 5-8h, for example, 5h, 6h, 7h, 8h, and the sintering time is adaptively adjusted according to the sintering temperature.

[0025] The positive electrode material matrix can be purchased through commercial channels, or prepared by the following method: after uniformly mixing the nickel-cobalt-manganese precursor material and lithium salt, calcine at 880-980°C for 4-7h, and then cool to 720-800°C and keep warm for 12-24h.

[0026] Material of coating layer Ca 2.4 Sr 0.6 Co4O9 is commercially available.

[0027] In addition, the currently disclosed coating material Ca 2.4 Sr0.6 The preparation method of Co4O9 includes: dispersing CaCO3, Co2O3 and SrCO3 in ethanol according to the designed molar ratio of Ca, Sr and Co in the material of the coating layer, and then ball milling to obtain a ball mill material; drying the ball mill material, and then sintering it for the first time to obtain a sintered material; grinding the sintered material, and then sintering it for the second time to obtain the material of the coating layer.

[0028] Preferably, the temperature of the first sintering is 840-880° C.; and the time of the first sintering is 5-7 hours.

[0029] The first sintered material obtained by the first sintering is easy to agglomerate. Before the second sintering, grinding the first sintered material into powder is conducive to sufficient sintering during the second sintering. In the actual experimental process, there is no obvious requirement for the grinding particle size, and the powder state is sufficient.

[0030] Preferably, the temperature of the second sintering is 860-900° C.; and the time of the second sintering is 6-10 h.

[0031] In the third aspect, the coated and modified high nickel cathode material is assembled into a lithium ion battery. The lithium ion battery has good thermal stability and good rate performance.

[0032] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0033] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0034] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0035] Example 1

[0036] (1) Preparation of coating materials

[0037] 2.28 g CaCO3, 3.14 g Co2O3, and 0.84 g SrCO3 were dispersed in 20 mL of ethanol and then ball milled in a ball mill at 300 r / min for 90 min;

[0038] The obtained ball mill was dried in a vacuum oven at 60 °C for 15 h;

[0039] The dried material was sintered in an oxygen environment at 860°C for 6 hours, ground, and then sintered in air at 880°C for 8 hours to obtain a coated material.

[0040] (2) Coating modification

[0041] 3gLi 1.1 Ni 0.9 Co 0.06 Mn 0.04 The O2 positive electrode material was mixed evenly with 0.05 g of the coating material prepared in step (1), and then calcined at 700° C. for 6 h to obtain a coated modified positive electrode material.

[0042] Figure 1 For Li 1.1 Ni 0.9 Co 0.06 Mn 0.04 SEM image of O2 positive electrode material. Figure 2 This is the SEM image of the coated and modified positive electrode material obtained in Example 1. Figure 1 and Figure 2 It can be seen that there are obvious fine particles on the surface of the coated sample. Due to the small coating amount, a uniform coating layer cannot be formed on the surface of the core material. The fine particles shown in the SEM image are the coating materials.

[0043] Comparative Example 1

[0044] The difference between Comparative Example 1 and Example 1 is that the coating material does not contain Sr.

[0045] (1) Preparation of coating materials

[0046] A mixture of 11.64 g Co(NO3).6H2O and 3.00 g CaCO3 was weighed and stirred in deionized water for 40 minutes, and then dried at 70°C for 24 hours. Then, the dried powder was calcined in an air environment at 900°C for 24 hours to obtain a coated material.

[0047] (2) Coating modification

[0048] 3gLi 1.1 Ni 0.9 Co 0.06 Mn 0.04 The O2 positive electrode material was mixed evenly with 0.05 g of the coating material prepared in step (1), and then calcined at 700° C. for 6 h to obtain a coated modified positive electrode material.

[0049] Example 2

[0050] The step (1) of Example 2 is the same as the step (1) of Example 1.

[0051] (2) Coating modification

[0052] 3gLi 1.25 Ni 0.90 Mn 0.10 The O2 positive electrode material was mixed evenly with 0.02 g of the coating material prepared in step (1), and then calcined at 600° C. for 6 h to obtain a coated modified positive electrode material.

[0053] Example 3

[0054] The step (1) of Example 3 is the same as the step (1) of Example 1.

[0055] (2) Coating modification

[0056] 3gLi 1.01 Ni 0.83 Mn 0.17 The O2 positive electrode material was mixed evenly with 0.08 g of the coating material prepared in step (1), and then calcined at 800° C. for 6 h to obtain a coated modified positive electrode material.

[0057] Example 4

[0058] The step (1) of Example 4 is the same as the step (1) of Example 1.

[0059] (2) Coating modification

[0060] 3g Li 1.1 Ni 0.897 Co 0.06 Mn 0.04 Nb 0.003 The O2 positive electrode material was mixed evenly with 0.05 g of the coating material prepared in step (1), and then calcined at 700° C. for 6 h to obtain a coated modified positive electrode material.

[0061] Example 5

[0062] The step (1) of Example 5 is the same as the step (1) of Example 1.

[0063] (2) Coating modification

[0064] 3g Li 1.1 Ni 0.897 Co 0.06 Mn 0.04 Al 0.003 The O2 positive electrode material was mixed evenly with 0.05 g of the coating material prepared in step (1), and then calcined at 700° C. for 6 h to obtain a coated modified positive electrode material.

[0065] The coated and modified positive electrode materials obtained in Examples 1-5 and Comparative Example 1, and Li 1.1 Ni 0.9 Co0.06 Mn 0.04 O2 cathode material, Li 1.25 Ni 0.9 Mn 0.1 O2 cathode material, Li 1.01 Ni 0.83 Mn 0.17 O2 cathode materials are assembled into batteries in the following ways:

[0066] The positive electrode material, binder PVDF, and conductive agent are mixed in a ratio of 8:1:1. After dry grinding for 10 minutes, the solvent NMP is added and stirred evenly with a homogenizer to obtain the positive electrode slurry, which is evenly coated on the aluminum foil. The metal lithium sheet is used as the negative electrode. The lithium ion secondary electrolyte LB-037 (1M LiPF6in DEC:EC:EMC=1:1:1 Vol%) is used as the electrolyte, and Celgard2325 is used as the separator to assemble the LIR2032 button battery.

[0067] The high temperature cycle performance of the battery was tested at 45°C. The specific test conditions were as follows: at 45°C, the battery was charged at a constant current rate of 0.1C to a voltage of 4.3V, then charged at a constant voltage rate of 0.01C and then discharged at 0.1C to 3V, and the cycle was repeated twice. The battery was then charged at a constant current rate of 0.5C to a voltage of 4.3V, then charged at a constant voltage rate of 0.05C and then discharged at 0.5C to 3V, and the charge and discharge capacity was recorded.

[0068] Figure 3 The results show that the high temperature cycle performance of the battery assembled with the uncoated modified positive electrode material is significantly lower than that of the battery assembled with the coated modified positive electrode material. For example, at a high temperature of 45°C, the capacity retention rate of the battery assembled with the coated modified positive electrode material obtained in Example 1 after 100 cycles under 0.5C charge and discharge conditions is 85.8%, while the capacity retention rate of the battery assembled with the coated modified positive electrode material is 85.8% after 100 cycles under 0.5C charge and discharge conditions. 1.1 Ni 0.9 Co 0.06 Mn 0.04 The cycle retention rate of the battery assembled with O2 positive electrode material is 73.3%; the capacity retention rate of Example 2 after 100 cycles under 0.5C charge and discharge conditions is 85.0%, and the capacity retention rate of the uncoated modified Li 1.25 Ni 0.90 Mn 0.10 The cycle retention rate of the battery assembled with O2 positive electrode material is 67.5%. 2.4 Sr 0.6 Co4O9 coated modified high nickel positive electrode material has great significance and practical application value for improving the high temperature cycle performance of batteries.

[0069] The effects of the coated modified positive electrode materials obtained in Example 1 and Comparative Example 1 on the high temperature performance of the battery are compared. Figure 4 As shown. It can be seen that the battery assembled with the coated modified positive electrode material obtained in Example 1 has a capacity retention rate of 85.8% after 100 cycles under 0.5C charge and discharge conditions at 45°C, and a 0.5C first cycle discharge capacity of 191.7 mAh / g. Compared with the battery assembled with the coated modified positive electrode material obtained in Comparative Example 1, the high temperature cycle performance is better. This shows that Sr plays an important role in the material of the coating layer.

[0070] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A coated and modified high nickel positive electrode material, characterized in that: It comprises a positive electrode material matrix and a coating layer located on at least a portion of the surface of the positive electrode material matrix; the chemical formula of the positive electrode material matrix is ​​LiNi x Co y Mn z M p O2, 0.7≤x<1, 0≤y≤0.3, 0<z≤0.3, 0≤p≤0.1, x+y+z+p=1; M is a doping element, wherein M is any one of W, Mg, Mo, Zr, V, Cr, Ge, Nb, Al, Sr or Ti or a combination of two or more thereof, and the material of the coating layer is Ca 2.4 Sr 0.6 Co4O9.

2. The coated and modified high-nickel positive electrode material according to claim 1, characterized in that: The mass of the material of the coating layer is 0.6%-3% of the mass of the positive electrode material matrix.

3. A method for preparing a coated and modified high-nickel positive electrode material, characterized in that: The coating material and the positive electrode material matrix are mixed and sintered to obtain the positive electrode material matrix; the chemical formula of the positive electrode material matrix is ​​LiNi x Co y Mn z M p O2, 0.7≤x<1, 0≤y≤0.3, 0<z≤0.3, 0≤p≤0.1, x+y+z+p=1; M is a doping element, wherein M is any one of W, Mg, Mo, Zr, V, Cr, Ge, Nb, Al, Sr or Ti or a combination of two or more thereof, and the material of the coating layer is Ca 2.4 Sr 0.6 Co4O9.

4. The preparation method according to claim 3, characterized in that: The sintering temperature is 500-800° C. and the sintering time is 5-8 hours.

5. A lithium ion battery, characterized in that: Including the coated and modified high-nickel positive electrode material as described in claim 1 or 2.

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