Modification method of layered transition metal oxide positive electrode material

Abstract

The invention discloses a modification method of a layered transition metal oxide positive electrode material, which comprises the following steps: (1) preparing nickel acetate tetrahydrate, ferric citrate, manganese acetate tetrahydrate, anhydrous citric acid and sodium acetate trihydrate into a mixed solution, and uniformly stirring in a water bath of 60 DEG C; (2) drying the solution obtained in the step (1) by using a spray dryer to obtain precursor powder, and drying the precursor powder in a 60 DEG C blast oven for one night to obtain powder 1; (3) putting the powder 1 obtained in the step (2) into a tabletting mold, and compacting the powder 1 for 1 minute under different pressures (0MPa, 10MPa, 15MPa and 20MPa) by a tabletting machine to obtain compacted powder 2; and (4) performing heat treatment on the powder 2 in the step (3) to finally obtain materials under different pressures (0MPa, 10MPa, 15MPa and 20MPa). The modification method of the layered transition metal oxide positive electrode material is simple, low in cost and environment-friendly, and meanwhile, the obtained referable modification method is applied to a sodium ion battery positive electrode and can provide excellent cycle stability.

Description

Technical Field

[0001] This invention discloses a method for modifying layered transition metal oxide cathode materials. More specifically, it relates to a method for modifying the compaction density of a composite material, namely the NFM523-900 precursor, used in the modification of sodium-ion battery cathode materials. Background Technology

[0002] With the rapid development of electric vehicles and the increasing market demand, the shortage of lithium resources has become a key problem restricting their sustainable development. Sodium resources are more abundant than lithium, and lithium / sodium ion batteries have almost the same working mode, so sodium ion batteries can become a substitute for lithium ion batteries.

[0003] Because layered oxides have advantages such as high energy density and good stability, they have gained favor among most researchers. However, layered cathode materials have disadvantages such as low cycle performance and low rate performance. In order to further develop sodium-ion battery cathode materials with more stable long-cycle performance, it is of great research and application significance to explore the synthesis process and modification of sodium-ion battery layered cathode materials.

[0004] To address these issues, researchers have improved the cycle life and performance stability of sodium-ion battery cathodes by modifying layered transition oxide cathode materials. This modification primarily involves coating, doping, and material compaction.

[0005] Compaction is a common process used to improve the performance of cathode materials in sodium-ion batteries. Compaction increases the density of the cathode material and the degree of contact between particles, thereby improving charge transport efficiency. Secondly, compaction improves the structural stability of the cathode material, reducing the peeling and fragmentation of loose particles, thus enhancing cycle stability and capacity retention.

[0006] Since the study of compaction density includes both electrode density and powder density, and the powder material is compressed into tablets, and the compaction strength of the material is measured using a tableting tool, thereby achieving stable and effective measurement of compaction density, we chose an efficient and safe method for directly measuring the compaction density of positive electrode powder. Summary of the Invention

[0007] The present invention aims to solve the cycle problem of the above-mentioned sodium-ion battery cathode material, so as to enable sodium-ion batteries to achieve true commercialization.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a method for modifying layered transition metal oxide cathode materials, specifically including the following steps:

[0009] (1) Prepare a mixed solution by mixing nickel acetate tetrahydrate, ferric citrate, manganese acetate tetrahydrate, anhydrous citric acid and sodium acetate trihydrate, and stir evenly in a water bath at 60°C (nickel acetate tetrahydrate, ferric citrate and manganese acetate tetrahydrate are in a stoichiometric ratio of 5:2:3).

[0010] (2) The solution obtained in step (1) is dried using a spray dryer to obtain precursor powder, and then dried overnight in a 60°C forced-air oven to obtain powder 1.

[0011] (3) Place the powder 1 obtained in step (2) into the tableting mold and compact it for 1 minute under different pressures (0MPa, 10MPa, 15MPa, 20MPa) using a tableting machine to obtain compacted powder 2.

[0012] (4) Place the powder 2 from step (3) into a corundum boat, transfer it to a tube furnace, pre-fire it at 500°C for 4 hours, then sinter it at 900°C for 15 hours, and then cool it down to room temperature (all in an oxygen atmosphere) to obtain materials under different pressures (0MPa, 10MPa, 15MPa, 20MPa).

[0013] The layered transition oxide NFM523 cathode materials prepared according to the preparation method under different compaction conditions were applied to the cathode of sodium-ion batteries.

[0014] Compared with existing technologies, the modification method of layered transition metal oxide cathode material described in this invention has the following advantages:

[0015] (1) The modification method of the layered transition metal oxide cathode material described in this invention is simple, conforms to the concept of sustainable development, is low in cost and easy to operate.

[0016] (2) By using different compaction intensities to change the structure of the cathode material, this invention increases the density of the cathode material and the degree of contact between particles, thereby improving the charge transfer efficiency. On the other hand, it improves the structural stability of the cathode material and reduces the peeling and fragmentation of loose particles, thereby improving cycle stability and capacity retention.

[0017] (3) The compaction modification method of the present invention has simple and readily available tools, is easy to operate, and has controllable production conditions, which improves the performance of the cathode material of sodium-ion batteries and enhances the cycle stability and capacity performance of the battery; this is of great significance for the sustainable development and commercial application of sodium-ion batteries. Attached Figure Description

[0018] Figure 1 This is a SEM image of the NFM523 precursor in Example 1 after compaction at 0 MPa.

[0019] Figure 2 The image shows the SEM image of the NFM523 precursor in Example 1 after compaction at 10 MPa.

[0020] Figure 3 The image shows the SEM image of the NFM523 precursor in Example 1 after compaction at 15 MPa.

[0021] Figure 4 The image shows the SEM image of the NFM523 precursor in Example 1 after compaction at 20 MPa.

[0022] Figure 5 The image shows the XRD patterns of the NFM523 precursor in Example 1 after different compaction processes.

[0023] Figure 6 This is a long-cycle diagram of the NFM523 precursor assembled into a half-cell after different compaction processes in Example 2. Detailed Implementation

[0024] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods unless otherwise specified.

[0025] The invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0026] The model and manufacturer information of the equipment used in the various embodiments of this invention are as follows:

[0027] Spray dryer, model B-290, BUCHI Laboratory Equipment Trading Co., Ltd.; Electronic balance, model FA2004, Shanghai Hengping Scientific Instruments Co., Ltd.; Thermostatic magnetic stirrer, model 85-2, Henan Gongyi Yuhua Co., Ltd.; CNC ultrasonic cleaner, model Ka2200DB, Kunshan Ultrasonic Instruments Co., Ltd.; Electric heating drying oven, model WG-136, Shanghai Yiheng Scientific Instruments Co., Ltd.; Vacuum drying oven, model DFZ, Beijing Kewei Yongxing Instruments Co., Ltd.; Low temperature tube furnace, model SX-GO6330, Tianjin Zhonghuan Experimental Electric Furnace Co., Ltd.; Stamping machine, model MRXCP60, Hefei Kejing Co., Ltd.; Glove box, model 168P12508A1NB, Shenzhen Yongxingye Precision Mold Co., Ltd.; Button battery sealing machine, model SY160, Shenzhen Yongxingye Precision Mold Co., Ltd.; LAND battery tester, model LAND. CT2001A, Wuhan Jinno Electronics Co., Ltd.; Autolab electrochemical workstation, model PGSTAT128N, Metrohm, Switzerland; scanning electron microscope, model Hitachi S4800, Hitachi, Japan; X-ray diffractometer, model D8 ADVANCE, BRUKER, Germany.

[0028] The raw material information used in the various embodiments of this invention is as follows:

[0029] Manganese acetate tetrahydrate, 99.0% specification, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; ferric citrate, 99.0% specification, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; nickel acetate tetrahydrate, 99.5% specification, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; sodium acetate trihydrate, 99.0% specification; anhydrous citric acid, 99.5% specification, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; sodium flakes, battery grade, purchased from Tianjin Zhongneng Lithium Industry Co., Ltd.; aluminum foil, battery grade, purchased from Hefei Kejing Materials Technology Co., Ltd.; oxygen. O2 (99.99%) was purchased from Tianjin Huanyu Gas Co., Ltd.; anhydrous ethanol (C2H6O) was purchased from Tianjin Fengchuan Chemical Reagent Technology Co., Ltd.; N-methylpyrrolidone was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; conductive carbon black Super-P was purchased from Temir High Graphite & Carbon Co., Ltd.; glass fiber separator was purchased from Whatman Ltd. (UK); battery casing was purchased from Shenzhen Yongxingye Precision Abrasives Co., Ltd.; NaClO4 in EC / DEC (1:1, w / w) was purchased from 1 mol L. -1 Battery grade, purchased from Guangdong Kelude New Energy Technology Co., Ltd.;

[0030] Example 1

[0031] A method for modifying a layered transition metal oxide cathode material includes the following steps:

[0032] (1) Weigh out 0.1 mol of nickel acetate tetrahydrate, ferric citrate, and manganese acetate tetrahydrate in a stoichiometric ratio of 5:2:3 and place them in a 500 ml beaker. Add 200 ml of deionized water to the beaker and stir for 30 minutes in a 60°C water bath to prepare a 0.5 mol L solution. -1 A mixed solution of acetate and citrate was prepared. 0.105 mol of sodium acetate trihydrate (Na / Me molar ratio of 1 to 1.05, Me = Ni, Fe, Mn) was weighed and added to the solution as the sodium source. Then, 0.5 mol of anhydrous citric acid (CA / Me molar ratio of 1:1) was weighed and added to the solution as an auxiliary agent. The solution was stirred and dissolved to synthesize the solution.

[0033] (2) The solution obtained in step (1) is dried using a spray dryer to obtain precursor powder, and then dried overnight in a 60°C forced-air oven to obtain powder 1;

[0034] (3) Place the powder 1 obtained in step (2) into the tableting mold and compact it for 1 minute under different pressures (0MPa, 10MPa, 15MPa, 20MPa) using a tableting machine to obtain compacted powder 2.

[0035] (4) Place the powder 2 from step (3) into a corundum boat, transfer it to a tube furnace, pre-fire it at 500°C for 4 hours, then sinter it at 900°C for 15 hours, and then cool it down to room temperature (all in an oxygen atmosphere) to obtain materials under different pressures (0MPa, 10MPa, 15MPa, 20MPa).

[0036] The electrode material prepared by the above method was tested, and the test results are shown in the figure. Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 .

[0037] Figure 1 This is a SEM image of the NFM523 precursor obtained in Example 1 after compaction at 0 MPa. Figure 2 , Figure 3 , Figure 4 The images are SEM images of the NFM523 precursor obtained in Example 1 after compaction at 10 MPa, 15 MPa, and 20 MPa. Figure 1The NFM523 precursor sample after being compacted at 0 MPa basically exhibits a hexagonal crystal structure. When the compaction strength is gradually increased to 20 MPa, the accumulation phenomenon of the sample at 20 MPa is more obvious, but it still exhibits a single crystal morphology and a relatively obvious hexagonal crystal structure. When the compaction is increased to 20 MPa, the compacted sample has smaller particles and smaller particle size compared to the uncompacted sample.

[0038] Figure 5 The XRD patterns of the NFM523 precursor in Example 1 after different compaction processes are shown. Apart from the NiO impurity phase, no other obvious impurity peaks appear, indicating good crystallinity. The (003) and (104) crystal plane peaks have shifted to the left. The reason for this phenomenon may be that as the compaction pressure of the precursor increases, there is a significant leftward shift, which increases the interlayer spacing.

[0039] Example 2

[0040] Electrochemical performance tests were performed on the half-cells assembled from the electrode materials prepared in the above steps. The positive electrode active material, conductive carbon black (super-p), and polyvinylidene fluoride (PVDF, 5%) from N-methylpyrrolidone (NMP) were weighed in a mass ratio of 8:1:1 and thoroughly ground to form a uniform slurry. The slurry was then uniformly coated onto aluminum foil using a coating machine to a thickness of approximately 80 μm. After coating, the electrode sheets were completely dried, compacted using a pressing machine, and punched into small discs with a diameter of 13 mm using a punching machine. These discs were then assembled with sodium metal discs of the same size in a glove box filled with argon atmosphere and with water and oxygen content below 0.15 ppm to form CR2032 button cells, which were then sealed using a button cell sealing machine. The separator was a battery-grade glass fiber separator purchased from Whatman Ltd., UK; the electrolyte was NaClO4 in EC / DEC (1:1, w / w), with a specification of 1 mol / L. -1 Battery grade, purchased from Guangdong Kelude New Energy Technology Co., Ltd.

[0041] Figure 6 The image shows a long-cycle diagram of the NFM523 precursor assembled into a half-cell after different compaction processes in Example 2. After 100 cycles, the capacity retention rates of the samples at 0 MPa, 10 MPa, 15 MPa, and 20 MPa were 30.4%, 47.8%, 57.3%, and 87.9%, respectively. The capacity retention rate increased with increasing compaction strength.

[0042] This invention investigates the effects of different compaction densities on the structure, morphology, and electrochemical performance of materials. Compaction methods can effectively improve the performance of cathode materials in sodium-ion batteries, enhancing cycle stability and capacity retention. This is significant for future research to further explore the changes in cathode material performance under different compaction conditions and the impact of compaction on the long-term stability of battery performance.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for modifying a layered transition metal oxide cathode material, characterized in that: Specifically, the steps include: (1) Weigh out 0.1 mol of nickel acetate tetrahydrate, ferric citrate, and manganese acetate tetrahydrate in a stoichiometric ratio of 5:2:3 and place them in a 500 ml beaker. Add 200 ml of deionized water to the beaker and stir for 30 minutes in a 60°C water bath to prepare a 0.5 mol L solution. -1 A mixed solution of acetate and citrate was prepared. 0.105 mol of sodium acetate trihydrate (Na / Me molar ratio of 1 to 1.05, Me = Ni, Fe, Mn) was weighed and added to the solution as the sodium source. Then, 0.5 mol of anhydrous citric acid (CA / Me molar ratio of 1:1) was weighed and added to the solution as an auxiliary agent. The solution was stirred and dissolved to synthesize the solution. (2) The solution obtained in step (1) is dried using a spray dryer to obtain precursor powder, and then dried overnight in a 60°C forced-air oven to obtain powder 1; (3) Place the powder 1 obtained in step (2) into the tableting mold and compact it for 1 minute under different pressures (0MPa, 10MPa, 15MPa, 20MPa) using a tableting machine to obtain compacted powder 2. (4) Place the powder 2 from step (3) into a corundum boat, transfer it to a tube furnace, pre-fire it at 500°C for 4 hours, then sinter it at 900°C for 15 hours, and then cool it down to room temperature (all in an oxygen atmosphere) to obtain materials under different pressures (0MPa, 10MPa, 15MPa, 20MPa).

2. The method for modifying a layered transition metal oxide cathode material according to claim 1, characterized in that: In step 1, the carbon sources selected are nickel acetate tetrahydrate, ferric citrate, and manganese acetate tetrahydrate; the sodium source is sodium acetate trihydrate; and the auxiliary agent is anhydrous citric acid.

3. The method for modifying a layered transition metal oxide cathode material according to claim 1, characterized in that: In step 1, nickel acetate tetrahydrate, ferric citrate, and manganese acetate tetrahydrate are in a stoichiometric ratio of 5:2:

3.

4. The method for modifying a layered transition metal oxide cathode material according to claim 1, characterized in that: In step 3, powder 1 is placed into a tableting mold and compacted for 1 minute by a tableting machine under different pressures (0MPa, 10MPa, 15MPa, 20MPa) to obtain compacted powder 2.

5. The method for modifying a layered transition metal oxide cathode material according to claim 1, characterized in that: The heat treatment process in step (4) includes the following steps: powder 2 is placed in a corundum boat, transferred to a tube furnace, pre-fired at 500°C for 4 hours, then sintered at high temperature at 900°C for 15 hours, and then naturally cooled to room temperature (all in an oxygen atmosphere).

6. Materials prepared by the preparation method according to any one of claims 1-5 under different pressures (0 MPa, 10 MPa, 15 MPa, 20 MPa).

7. The application of materials prepared by the preparation method according to any one of claims 1-5 at different pressures (0 MPa, 10 MPa, 15 MPa, 20 MPa) in sodium-ion batteries.

Images