Modified cobalt-free positive electrode material and preparation method and application thereof

Abstract

This invention discloses a modified cobalt-free cathode material, its preparation method, and its applications, comprising a Li core. 1+x Ni 0.75 Mn 0.25 O2 and a coating layer attached to its surface; the coating layer material is lithium aluminum hydride and zirconium phosphotungstenate, wherein lithium aluminum hydride can participate in offsetting the irreversible capacity loss caused by the formation of the SEI film during the first charge and discharge of the lithium-ion battery, greatly improving the initial coulombic efficiency and charge-discharge cycle performance of the lithium-ion battery, and zirconium phosphotungstenate improves the conductivity of the material and the diffusion rate of lithium ions in this cobalt-free layered cathode material, significantly improving the rate performance and cycle stability of the lithium-ion battery. Compared with cobalt-free cathode materials without lithium aluminum hydride and zirconium phosphotungstenate coating, the modified cobalt-free cathode material prepared by coating lithium aluminum hydride and zirconium phosphotungstenate has an initial coulombic efficiency of 87.5% to 89.8%, an initial discharge specific capacity of 187.4 to 193.2 mAh / g at 0.1C, a 2C rate performance of 87.0% to 89.1%, and a capacity retention rate of 98% to 99.2% after 100 cycles. Moreover, the entire preparation process is simple and has good application prospects.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material technology, specifically relating to a modified cobalt-free cathode material, its preparation method, and its application. Background Technology

[0002] Cobalt, as a crucial element in the cathode materials of power batteries, not only stabilizes the material's structure but also improves its cycle and rate performance. However, the uneven distribution of global cobalt reserves, resource shortages, and rising prices have forced global battery material suppliers, battery manufacturers, and automakers to find ways to reduce the cobalt content in ternary batteries. This has led to the development of NCA, NCM ternary, and NCMA quaternary technologies, but these technologies still cannot eliminate the constraints of cobalt resources on global battery material suppliers and automakers.

[0003] Following this, cobalt-free layered cathode materials emerged. Cobalt-free nickel-based cathode materials have attracted much market attention due to their advantages such as low cost and high specific capacity, but they also have problems such as poor rate performance, short cycle life, and poor high-voltage cycle stability that need to be addressed. Currently, commonly used modification methods include particle size nanosizing and morphology control, surface coating, and ion doping. By combining these three aspects of modification, the electrical performance of cobalt-free layered cathode materials can be greatly improved.

[0004] However, improper selection of coating agents or dopants can also lead to increased resistance, affecting electron and ion transport and thus weakening electrical performance. Due to the lack of cobalt, cobalt-free layered cathode materials in related technologies still suffer from low initial efficiency, poor rate capability, and poor cycle performance. Therefore, further modification of cobalt-free layered cathode materials is key to solving these problems. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a modified cobalt-free cathode material, its preparation method and application, so as to solve the technical problems of low initial efficiency, poor rate performance and cycle performance of existing cobalt-free cathode materials.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a modified cobalt-free cathode material, comprising a cobalt-free cathode material and a coating layer; the coating layer is lithium aluminum hydride and zirconium phosphotungstate.

[0008] Preferably, the cobalt-free cathode material is Li. 1+x Ni 0.75 Mn 0.25 O2; where 1.06≤1+x≤1.08.

[0009] Preferably, the mass of lithium aluminum hydride is Li 1+x Ni0.75 Mn 0.25 O2 content: 0.05%–3% by mass; zirconium phosphotungstenate content: Li 1+x Ni 0.75 Mn 0.25 0.03% to 4% of the mass of O2.

[0010] This invention also discloses a method for preparing the above-mentioned modified cobalt-free cathode material, comprising the following steps:

[0011] S1, Lithium hydroxide and Ni 0.75 Mn 0.25 (OH)2 was uniformly dispersed by mixing to obtain a cobalt-free cathode material precursor.

[0012] S2. The cobalt-free cathode material precursor obtained in step S1 is sintered in an oxygen atmosphere, cooled to room temperature, crushed, and sieved to obtain Li. 1+x Ni 0.75 Mn 0.25 O2;

[0013] S3, the Li obtained in step S2 1+x Ni 0.75 Mn 0.25 After O2 is mixed evenly with lithium aluminum hydride and zirconium phosphotungstenate, it is sintered in air, cooled to room temperature, crushed and sieved to obtain a modified cobalt-free cathode material.

[0014] Preferably, in step S1, the molar ratio of Li:Ni:Mn is (1.06~1.08):0.75:0.25.

[0015] Preferably, in step S2, sintering is divided into a pre-sintering stage and a solid-state reaction stage.

[0016] More preferably, the heating rate during the pre-firing stage is 3℃ / min, the pre-firing stage temperature is 550~750℃, and the holding time is 2~3h.

[0017] More preferably, the heating rate of the solid-phase reaction stage is 3℃ / min, the temperature of the solid-phase reaction stage is 880~910℃, and the holding time is 8~18h.

[0018] Preferably, in step S3, the sintering temperature is 200–600°C and the holding time is 6–12 h.

[0019] This invention also discloses the application of the above-mentioned modified cobalt-free cathode material in the preparation of lithium-ion battery cathode materials.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention discloses a modified cobalt-free cathode material, comprising a cobalt-free cathode material and a coating layer; the coating layer is lithium aluminum hydride and zirconium phosphotungsten oxide; lithium aluminum hydride can participate in offsetting the irreversible capacity loss caused by the formation of the SEI film during the first charge and discharge of the lithium-ion battery, greatly improving the first coulombic efficiency and charge-discharge cycle performance of the lithium-ion battery; zirconium phosphotungsten oxide improves the conductivity of the material and the diffusion rate of lithium ions in this cobalt-free layered cathode material, significantly improving the rate performance and cycle stability of the lithium-ion battery compared to materials without cobalt. The cobalt-free cathode material coated with lithium aluminum hydride and zirconium phosphotungsten oxide showed significant improvements in initial coulombic efficiency, rate performance, and cycle performance. The modified cobalt-free cathode material obtained had an initial coulombic efficiency of 87.5%–89.8%, an initial discharge specific capacity of 187.4–193.2 mAh / g at 0.1C, a rate performance of 87.0%–89.1% at 2C, and a capacity retention of 98%–99.2% after 100 cycles.

[0022] This invention also discloses a method for preparing the above-mentioned modified cobalt-free cathode material. First, a cobalt-free cathode material precursor is prepared by mixing. Then, pre-calcination and solid-state reaction are carried out to obtain the cobalt-free cathode material. Finally, the cobalt-free cathode material is mixed uniformly with lithium aluminum hydride and zirconium phosphotungstenate and sintered in air, so that lithium aluminum hydride and zirconium phosphotungstenate are coated on the outer layer of the cobalt-free cathode material to obtain the modified cobalt-free cathode material. The entire preparation process is simple and has good application prospects.

[0023] The present invention also discloses the application of the above-mentioned modified cobalt-free cathode material in the preparation of lithium-ion battery cathode materials. When the cobalt-free cathode material is coated with 0.3% lithium aluminum hydride and 0.25% zirconium phosphotungstenate, the modified cobalt-free cathode material obtained has an initial coulombic efficiency of 89.8%, an initial discharge specific capacity of 193.2 mAh / g at 0.1C, a 2C rate performance of 89.1%, and a capacity retention rate of 99.2% after 100 cycles at 0.1C. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0025] It should be noted that the terms "first," "second," etc., used in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] The present invention will be further described in detail below with reference to specific embodiments:

[0027] A method for preparing a modified cobalt-free cathode material includes the following steps:

[0028] S1, Lithium hydroxide and Ni 0.75 Mn 0.25 (OH)2 is uniformly dispersed in a certain proportion using a specific mixing method;

[0029] S2. The uniformly dispersed material is sintered under an oxygen-containing atmosphere, naturally cooled to room temperature, and then crushed and sieved to obtain the cobalt-free cathode material Li. 1+x Ni 0.75 Mn 0.25 O2;

[0030] S3, then Li 1+x Ni 0.75 Mn 0.25 O2 is mixed with lithium aluminum hydride and zirconium phosphotungsten in a certain proportion and sintered under air conditions. After crushing and passing through a 400-mesh sieve, a modified cobalt-free cathode material is obtained.

[0031] In step S1, the molar ratio of Li:Ni:Mn is (1.06~1.08):0.75:0.25, preferably 1.08.

[0032] In step S2, sintering is divided into a pre-sintering stage and a solid-state reaction stage;

[0033] The pre-firing stage involves raising the temperature from room temperature to 550–750°C, preferably 650°C, and holding the temperature for 2–3 hours, preferably 2.5 hours.

[0034] The solid-phase reaction stage is heated to 880–910°C, preferably 905°C, at a heating rate of 3°C / min; and held at this temperature for 8–18 hours, preferably 12 hours.

[0035] In step S3, the lithium aluminum hydride and zirconium phosphotungstenate used account for 0.05% to 3% and 0.03% to 4% of the mass of the cobalt-free cathode material, respectively, preferably 0.3% and 0.25%.

[0036] The sintering temperature in S3 is increased from room temperature to 200-600℃, preferably 500℃; the holding temperature is 6-12h, preferably 12h.

[0037] Example 1

[0038] A method for preparing a modified cobalt-free cathode material specifically includes the following steps:

[0039] S1, Lithium hydroxide and Ni 0.75 Mn 0.25 (OH)2 was weighed and uniformly dispersed at a molar ratio of 1.06:1;

[0040] S2. The uniformly dispersed material is sintered under an oxygen-containing atmosphere at a heating rate of 3℃ / min, in two stages. The first stage, the pre-sintering stage, is sintered at 550℃ for 2 hours, and the second stage, the solid-state reaction stage, is sintered at 880℃ for 8 hours. The sintered product is then naturally cooled to room temperature, crushed, and sieved to obtain the cobalt-free cathode material Li. 1.06 Ni 0.75 Mn 0.25 O2;

[0041] S3, Li 1.06 Ni 0.75 Mn 0.25 O2 is mixed with lithium aluminum hydride and zirconium phosphotungsten in a certain proportion, with lithium aluminum hydride and zirconium phosphotungsten accounting for 0.05% and 0.03% of the mass of the cobalt-free cathode material, respectively. After being mixed evenly, the mixture is sintered in air, heated from room temperature to 200°C, sintered for 6 hours, cooled to room temperature, crushed, and passed through a 400-mesh sieve to finally obtain the modified cobalt-free cathode material.

[0042] Example 2

[0043] A method for preparing a modified cobalt-free cathode material specifically includes the following steps:

[0044] S1, Lithium hydroxide and Ni 0.75 Mn 0.25 (OH)2 was weighed and uniformly dispersed at a molar ratio of 1.08:1;

[0045] S2. The uniformly dispersed material is sintered under an oxygen-containing atmosphere at a heating rate of 3℃ / min, in two stages. The first stage, the pre-sintering stage, is sintered at 650℃ for 2.5 hours, and the second stage, the solid-state reaction stage, is sintered at 905℃ for 12 hours. The sintered product is then naturally cooled to room temperature, crushed, and sieved to obtain the cobalt-free cathode material Li. 1.08 Ni 0.75 Mn 0.25 O2;

[0046] S3, Li 1.08 Ni 0.75 Mn 0.25 O2 is mixed with lithium aluminum hydride and zirconium phosphotungsten in a certain proportion, with lithium aluminum hydride and zirconium phosphotungsten accounting for 0.3% and 0.25% of the mass of the cobalt-free cathode material, respectively. After being mixed evenly, the mixture is sintered under air conditions, heated from room temperature to 500°C, sintered for 8 hours, cooled to room temperature, crushed, and passed through a 400-mesh sieve to finally obtain the modified cobalt-free cathode material.

[0047] Example 3

[0048] A method for preparing a modified cobalt-free cathode material specifically includes the following steps:

[0049] S1, Lithium hydroxide and Ni 0.75 Mn 0.25 (OH)2 was weighed and uniformly dispersed at a molar ratio of 1.07:1;

[0050] S2. The uniformly dispersed material is sintered under an oxygen-containing atmosphere at a heating rate of 3℃ / min, in two stages. The first stage, the pre-sintering stage, is sintered at 750℃ for 3 hours, and the second stage, the solid-state reaction stage, is sintered at 910℃ for 18 hours. The sintered product is then naturally cooled to room temperature, crushed, and sieved to obtain the cobalt-free cathode material Li. 1.07 Ni 0.75 Mn 0.25 O2;

[0051] S3, Li 1.07 Ni 0.75 Mn 0.25 O2 is mixed with lithium aluminum hydride and zirconium phosphotungsten in a certain proportion, with lithium aluminum hydride and zirconium phosphotungsten accounting for 3% and 4% of the mass of the cobalt-free cathode material, respectively. After being mixed evenly, the mixture is sintered under air conditions, heated from room temperature to 600°C, sintered for 12 hours, cooled to room temperature, crushed, and passed through a 400-mesh sieve to finally obtain the modified cobalt-free cathode material.

[0052] Comparative Example

[0053] A method for preparing a modified cobalt-free cathode material specifically includes the following steps:

[0054] S1, Lithium hydroxide and Ni 0.75 Mn 0.25 (OH)2 was weighed and uniformly dispersed at a molar ratio of 1.08:1;

[0055] S2. The uniformly dispersed material is sintered under an oxygen-containing atmosphere at a heating rate of 3℃ / min, in two stages. The first stage, the pre-sintering stage, is sintered at 650℃ for 2.5 hours, and the second stage, the solid-state reaction stage, is sintered at 905℃ for 12 hours. The sintered product is then naturally cooled to room temperature, crushed, and sieved to obtain the cobalt-free cathode material Li. 1.08 Ni 0.75 Mn 0.25 O2.

[0056] The samples from Examples 1-3 and the comparative example were fabricated using 2025 coin cells. Electrochemical performance was tested at room temperature under voltage conditions of 3.0–4.3V, sequentially performing charge-discharge tests at 0.1C, 0.5C, 1C, and 2C, and resistance was also measured. Rate performance was calculated as: 2C discharge capacity / 0.1C discharge capacity.

[0057] Table 1 compares the 0.1C first-discharge specific capacity, rate performance, cycle performance, and resistance data of the ternary cathode samples from Examples 1-3 of this invention with those of the comparative examples. The results in the table show that, compared to the comparative examples, the cobalt-free cathode material coated with lithium aluminum hydride and zirconium phosphotungstenate exhibits significantly improved first-discharge efficiency, rate performance, and cycle performance. When coated with 0.3% lithium aluminum hydride and 0.25% zirconium phosphotungstenate, the modified cobalt-free cathode material achieves an first-discharge specific capacity of 89.8%, a 0.1C first-discharge specific capacity of 193.2 mAh / g, a 2C rate performance of 89.1%, and a capacity retention of 99.2% after 100 cycles at 0.1C.

[0058] Table 1. First-out capacitance, rate performance, cycle performance, and resistance at 0.1C for the examples and comparative samples.

[0059]

[0060]

[0061] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a modified cobalt-free cathode material, characterized in that, Includes the following steps: S1, Lithium hydroxide and Ni 0.75 Mn 0.25 (OH)2 was uniformly dispersed by mixing to obtain a cobalt-free cathode material precursor. S2. The cobalt-free cathode material precursor obtained in step S1 is sintered in an oxygen atmosphere, cooled to room temperature, crushed, and sieved to obtain Li. 1+x Ni 0.75 Mn 0.25 O2; S3, the Li obtained in step S2 1+x Ni 0.75 Mn 0.25 O2 is mixed evenly with lithium aluminum hydride and zirconium phosphotungstenate, sintered in air, cooled to room temperature, crushed and sieved to obtain modified cobalt-free cathode material; the sintering temperature is 200~600℃, and the holding time is 6~12 h. The modified cobalt-free cathode material includes a cobalt-free cathode material and a coating layer; the coating layer is formed by sintering lithium aluminum hydride and zirconium phosphotungstenate. The cobalt-free cathode material is Li 1+x Ni 0.75 Mn 0.25 O2; where 1.06≤1+x≤1.08; The mass of lithium aluminum hydride is Li 1+x Ni 0.75 Mn 0.25 0.05%~3% of O2 by mass; zirconium phosphotungsten by mass of Li 1+ x Ni 0.75 Mn 0.25 0.03% to 4% of the mass of O2.

2. The method for preparing the modified cobalt-free cathode material according to claim 1, characterized in that, In step S1, the molar ratio of Li:Ni:Mn is (1.06~1.08):0.75:0.

25.

3. The method for preparing the modified cobalt-free cathode material according to claim 1, characterized in that, In step S2, sintering is divided into a pre-sintering stage and a solid-state reaction stage.

4. The method for preparing the modified cobalt-free cathode material according to claim 3, characterized in that, The heating rate during the pre-firing stage is 3℃ / min, the temperature during the pre-firing stage is 550~750℃, and the holding time is 2~3h.

5. The method for preparing the modified cobalt-free cathode material according to claim 3, characterized in that, The heating rate of the solid-phase reaction stage is 3℃ / min, the temperature of the solid-phase reaction stage is 880~910℃, and the holding time is 8~18 h.

6. The application of the modified cobalt-free cathode material prepared by the method of any one of claims 1 to 5 in the preparation of cathode materials for lithium-ion batteries.

Images