Lithium ion battery electrode material and preparation method thereof

Abstract

According to the lithium ion battery electrode material and the preparation method thereof, a composite material with molybdenum sulfide nanoparticles loaded on the surfaces of porous microspheres Ce-lambda-MnO2 is prepared through a two-step hydrothermal method, the porous structure provides a large number of active sites, the reversible capacity is improved, electrolyte permeation is promoted, and the performance of the lithium ion battery electrode material is improved. The wettability of the electrolyte on an electrode material is improved, and the lithium ion transmission rate is increased; by doping manganese dioxide with Ce, additional free electrons can be introduced, the band gap of MnO2 can be reduced, the electron mobility can be enhanced, lambda-MnO2 and MoS2 are compounded, and after a heterojunction structure is formed by the lambda-MnO2 and the MoS2, the conductivity and the capacity performance are further improved, the preparation process is simple, the price is low, and the preparation method has an industrialization prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular to a lithium ion battery electrode material and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries are widely used in consumer electronics, electric vehicles and energy storage systems due to their high energy density, long cycle life and other advantages. However, as the industry demand continues to upgrade, the requirements for lithium ion batteries are constantly increasing, and developing high-energy, high-power-density lithium ion batteries has always been the focus and difficulty of researchers. Lithium ion batteries are mainly composed of four parts: negative electrode, positive electrode, separator and electrolyte. The negative electrode material is one of the core components, and its performance directly determines the capacity, rate characteristic and rate performance of the battery. Currently, the commercialized graphite material for lithium ion battery negative electrode has the disadvantages of low theoretical specific capacity (372 mAh / g) and poor rate performance, which cannot meet the actual commercialization demand. Therefore, it is of great practical significance to develop lithium ion battery negative electrode materials with large capacity, long life and high safety. Transition metal oxides, such as manganese dioxide, have attracted widespread attention from researchers due to their high capacity.

[0003] The prior art CN115064683A discloses that by adjusting the carbon coating, annealing atmosphere and annealing temperature, a variety of manganese oxide nanotube negative electrode materials are synthesized. Compared with single-phase manganese oxide nanotubes (β-MnO2, Mn3O4, MnO), the nanoscale composite nanotubes (MnO / Mn3O4, MnO2 / Mn3O4) containing two phases have more excellent electrochemical performance. Due to the presence of manganese ions with multiple valence states, the unique synergistic effect between manganese ions with different valence states can be achieved through electron transition, significantly improving the electrical conductivity of the manganese oxide electrode material and further improving its electrochemical performance. However, the product obtained by this technology has poor thermodynamic stability and unstable structure.

[0004] CN115385381A discloses that manganese dioxide is coated by co-precipitation of metal copper salt, molybdate and folic acid, and an oxidation molybdenum, elemental copper and nitrogen-doped carbon coating layer are generated during high-temperature calcination. For the first time, nitrogen-doped carbon is obtained by one-step calcination using nitrogen-containing folic acid, and the reduction gas from the decomposition of organic acid further reduces copper ions to elemental copper, further enhancing the electrical conductivity of manganese dioxide. However, the preparation process of the above prior art is complex and costly. Therefore, it is necessary to find a lithium ion battery negative electrode material with simple synthesis process, low price and excellent electrochemical performance. SUMMARY

[0005] Based on the problems in the prior art, the purpose of the present application is to provide an electrode material with simple synthesis process, low price and excellent electrochemical performance and a preparation method thereof, the preparation method of the electrode material comprising the following steps:

[0006] (1) The reaction raw materials manganese acetate and cerium source are weighed according to a molar ratio of 1:(0.02-0.2), dissolved in deionized water, stirred for 20-30 min to form a uniformly mixed solution, tartaric acid is added to the uniformly mixed solution and stirred uniformly, the obtained solution is transferred into a polytetrafluoroethylene high-pressure reaction kettle, and hydrothermal reaction is carried out to obtain Ce-λ-MnO2; the product obtained by the above hydrothermal reaction is washed with deionized water and ethanol, and dried in a vacuum drying box at 80-100 DEG C; (2) the Ce-λ-MnO2 is further dissolved in deionized water, Mo source, S source and polyethylene glycol are added and mixed uniformly, the solution is transferred into a polytetrafluoroethylene high-pressure reaction kettle, and hydrothermal reaction is further carried out to obtain a composite electrode material of Ce-λ-MnO2 / MoS2.

[0007] In an optional embodiment, the hydrothermal reaction temperature of the above steps (1)-(2) is 160-200 DEG C, and the reaction time is 10-18 h; the reaction kettle is naturally cooled to room temperature, and the filling ratio in the reaction kettle is 65-80%.

[0008] In an optional embodiment, the molar ratio of manganese acetate / tartaric acid is 1:(2-3);

[0009] In an optional embodiment, the cerium source is selected from one of cerium sulfate, cerium nitrate and cerium acetate;

[0010] In an optional embodiment, the Mo source is selected from sodium molybdate dihydrate; and the S source is selected from thioacetamide or thiourea;

[0011] In an optional embodiment, the molar ratio of the Mo source and the S source is 1:2; and the mass ratio of sodium molybdate dihydrate and polyethylene glycol is 1:(1-2);

[0012] Compared with the prior art, the present application can achieve the following technical effects:

[0013] The composite material of porous microspherical Ce-λ-MnO2 surface loaded with nano-sized molybdenum sulfide nanoparticles is prepared by a two-step hydrothermal method, the porous structure provides a large number of active sites, improves the reversible capacity, promotes the penetration of the electrolyte, improves the wettability of the electrolyte to the electrode material, and improves the lithium ion transmission rate; by doping Ce to manganese dioxide, additional free electrons can be introduced, the band gap of MnO2 is reduced, and the electron mobility is enhanced. After λ-MnO2 and MoS2 are compounded, the heterojunction structure is formed, and the molybdenum sulfide can compensate for the poor intrinsic conductivity of MnO2 (10 -5The defects of the composite electrode material have a low charge transfer resistance (1.0*10-4S / cm) and a low electrode polarization, and on the other hand, the double active sites of the λ-MnO2 and the MoS2 improve the capacity performance. The raw materials used in the application are easy to obtain, the preparation and synthesis process is green, simple, low in cost and easy to realize large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 SEM image of the composite material obtained in the embodiment of the application;

[0015] Figure 2 TEM image of the composite material obtained in the embodiment of the application;

[0016] Figure 3 XRD image of the Ce-λ-MnO2 obtained in the embodiment of the application. DETAILED DESCRIPTION

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0018] Embodiment 1

[0019] The reaction raw materials, 10 mmol of manganese acetate and 1 mmol of cerium nitrate, were weighed and dissolved in 80 ml of deionized water, mixed and stirred for 20 min to form a uniform mixed solution. Then, 20 mmol of tartaric acid was added to the uniform mixed solution, and the stirring was continued for 20 min. The obtained solution was transferred into a 100 ml high-pressure reaction kettle for hydrothermal reaction, the hydrothermal temperature was 180℃, and the reaction time was 15 h. The Ce-λ-MnO2 was obtained. The product obtained by the above hydrothermal reaction was washed with deionized water and ethanol and dried. The obtained Ce-λ-MnO2 was further dissolved in 80 ml of deionized water, and 5 mmol of sodium molybdate dihydrate, 10 mmol of thioacetamide and polyethylene glycol were added, wherein the mass ratio of sodium molybdate dihydrate and polyethylene glycol was 1:1. The mixing was continued for 20 min, and the solution was transferred into a high-pressure reaction kettle for further hydrothermal reaction, the hydrothermal temperature was 180℃, and the reaction time was 15 h. The composite electrode material of Ce-λ-MnO2 / MoS2 was obtained.

[0020] Embodiment 2

[0021] The reaction raw material manganese acetate 10 mmol and 1.2 mmol cerium nitrate were weighed, dissolved in 80 ml of deionized water, mixed and stirred for 20 min to form a uniformly mixed solution, then 20 mmol of tartaric acid was added to the uniformly mixed solution, and stirring was continued for 20 min; the obtained solution was transferred into a 100 ml high-pressure reaction kettle, and hydrothermal reaction was carried out, the hydrothermal temperature was 160°C, and the reaction time was 18 h; Ce-λ-MnO2 was obtained; the product obtained by the above hydrothermal reaction was washed with deionized water and ethanol, and dried; the obtained Ce-λ-MnO2 was further dissolved in 80 ml of deionized water, 5 mmol of sodium molybdate dihydrate, 10 mmol of thioacetamide and polyethylene glycol were added, and the mass ratio of sodium molybdate dihydrate to polyethylene glycol was 1:1.5; continue to mix for 20 min, and then transfer the solution to a polyvinylidene fluoride high-pressure reaction kettle for further hydrothermal reaction, the hydrothermal temperature is 160°C, and the reaction time is 18 h; a composite electrode material of Ce-λ-MnO2 / MoS2 is obtained.

[0022] Example 3

[0023] The reaction raw material manganese acetate 10 mmol and 1.2 mmol cerium nitrate were weighed, dissolved in 80 ml of deionized water, mixed and stirred for 20 min to form a uniformly mixed solution, then 20 mmol of tartaric acid was added to the uniformly mixed solution, and stirring was continued for 20 min; the obtained solution was transferred into a 100 ml high-pressure reaction kettle, and hydrothermal reaction was carried out, the hydrothermal temperature was 160°C, and the reaction time was 18 h; Ce-λ-MnO2 was obtained; the product obtained by the above hydrothermal reaction was washed with deionized water and ethanol, and dried; the obtained Ce-λ-MnO2 was further dissolved in 80 ml of deionized water, 5 mmol of sodium molybdate dihydrate, 10 mmol of thioacetamide and polyethylene glycol were added, and the mass ratio of sodium molybdate dihydrate to polyethylene glycol was 1:1.5; continue to mix for 20 min, and then transfer the solution to a polyvinylidene fluoride high-pressure reaction kettle for further hydrothermal reaction, the hydrothermal temperature is 160°C, and the reaction time is 18 h; a composite electrode material of Ce-λ-MnO2 / MoS2 is obtained.

[0024] Comparative Example 1

[0025] The reaction raw material manganese acetate 10 mmol and 1.2 mmol cerium nitrate were weighed, dissolved in 80 ml of deionized water, mixed and stirred for 20 min to form a uniformly mixed solution, then 20 mmol of tartaric acid was added to the uniformly mixed solution, and stirring was continued for 20 min; the obtained solution was transferred into a 100 ml high-pressure reaction kettle, and hydrothermal reaction was carried out, the hydrothermal temperature was 160°C, and the reaction time was 18 h; Ce-λ-MnO2 was obtained; the product obtained by the above hydrothermal reaction was washed with deionized water and ethanol, and dried; the obtained Ce-λ-MnO2 was further dissolved in 80 ml of deionized water, 5 mmol of sodium molybdate dihydrate, 10 mmol of thioacetamide and polyethylene glycol were added, and the mass ratio of sodium molybdate dihydrate to polyethylene glycol was 1:1.5; continue to mix for 20 min, and then transfer the solution to a polyvinylidene fluoride high-pressure reaction kettle for further hydrothermal reaction, the hydrothermal temperature is 160°C, and the reaction time is 18 h; a composite electrode material of Ce-λ-MnO2 / MoS2 is obtained.

[0026] Comparative Example 2

[0027] In 80 ml of deionized water, 5 mmol of sodium molybdate dihydrate, 10 mmol of thioacetamide and polyethylene glycol were added, and the mass ratio of sodium molybdate dihydrate and polyethylene glycol was 1:1; continue to mix for 20 min, transfer the solution to a high-pressure reaction kettle, continue to carry out hydrothermal reaction, the hydrothermal temperature is 180℃, the reaction time is 15h; obtain MoS2.

[0028] Comparative Example 3

[0029] The reaction raw material manganese acetate 10 mmol was weighed, dissolved in 80 ml of deionized water, mixed and stirred for 20 min to form a uniformly mixed solution, then 20 mmol of tartaric acid was added to the uniformly mixed solution, and stirred for 20 min; the obtained solution was transferred into a 100 ml high-pressure reaction kettle, and hydrothermal reaction was carried out, the hydrothermal temperature was 180℃, and the reaction time was 15h; λ-MnO2 was obtained; the product obtained by the above hydrothermal reaction was washed with deionized water and ethanol, and dried; the obtained λ-MnO2 was further dissolved in 80 ml of deionized water, 5 mmol of sodium molybdate dihydrate, 10 mmol of thioacetamide and polyethylene glycol were added, and the mass ratio of sodium molybdate dihydrate and polyethylene glycol was 1:1; continue to mix for 20 min, transfer the solution to a high-pressure reaction kettle, continue to carry out hydrothermal reaction, the hydrothermal temperature is 180℃, the reaction time is 15h; obtain MnO2 / MoS2 composite electrode material.

[0030] The composite material obtained in Example 1 was subjected to SEM test, and the results showed that the λ-MnO2 / MoS2 material presented a microporous spherical structure; the composite material obtained in Example 1 was subjected to TEM test, and the results showed that MoS2 nanoparticles were dispersed on the sheet structure of manganese dioxide.

[0031] Battery assembly: the product was dispersed in N-methyl pyrrolidone in a ratio of 8:1:1 with the binder polyvinylidene fluoride and conductive carbon black, stirred for 3h until mixed uniformly, then coated on the negative current collector and dried at 80℃ for 10h to obtain a negative electrode sheet. The lithium metal sheet was used as the counter / reference electrode, polypropylene was used as the separator, LiPF6 was used as the electrolyte, the solvent was EC: DMC: EMC in a volume ratio of 1:1:1, and a coin cell was assembled for electrochemical performance test. The discharge specific capacity test under different current densities is shown in Table 1 (unit: mAh / g); the capacity retention rate after stable cycling for 100 cycles at 0.1A / g is shown in Table 2.

[0032] Table 1

[0033] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 0.2 A / g 737 711 690 726 0.5 A / g 651 601 598 643 1 A / g 439 401 421 430 2 A / g 383 356 349 363 5 A / g 283 269 242 271

[0034] Table 2

[0035] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Capacity retention 98.6％ 94.1％ 90.3％ 94.8％

Claims

1. A lithium-ion battery electrode material, characterized in that It is composed of Ce-doped λ-MnO2 and MoS2. The Ce-doped λ-MnO2 is a porous microsphere of 10-30 μm, and the pores of the porous microsphere are loaded with nano-scale MoS2 particles.

2. The method for preparing a lithium ion battery electrode material according to claim 1, wherein: (1) Weighing the reaction raw materials manganese acetate and cerium source in a molar ratio of 1: (0.02-0.2), dissolving them in deionized water, and stirring them thoroughly to form a mixed solution. Adding tartaric acid to the mixed solution, and continuing to stir evenly; transferring the obtained solution into a polytetrafluoroethylene autoclave, and performing a hydrothermal reaction to obtain Ce-λ-MnO2; washing the product obtained by the above hydrothermal reaction with deionized water and ethanol, and drying; (2) continuing to dissolve Ce-λ-MnO2 in deionized water, adding Mo source, S source and polyethylene glycol, and continuing to mix evenly, transferring the solution into a polytetrafluoroethylene autoclave, and continuing to perform a hydrothermal reaction to obtain a Ce-λ-MnO2 / MoS2 composite electrode material.

3. The method for preparing a lithium-ion battery electrode material according to claim 2, wherein the hydrothermal reaction temperature of steps (1) to (2) is 160-200°C, the reaction time is 10-18 hours, and the filling ratio in the reactor is 65-80%.

4. The method for preparing a lithium-ion battery electrode material according to claim 1, wherein the molar ratio of manganese acetate to tartaric acid is 1:(2-3). 5 . The method for preparing a lithium-ion battery electrode material according to claim 1 , wherein the cerium source is selected from cerium sulfate, cerium nitrate or cerium acetate.

6. The method for preparing a lithium ion battery electrode material according to claim 1, wherein the Mo source is selected from sodium molybdate dihydrate.

7. The method for preparing a lithium-ion battery electrode material according to claim 1, wherein the S source is selected from thioacetamide or thiourea.

8. The method for preparing a lithium ion battery electrode material according to claim 1, wherein the molar ratio of the Mo source to the S source is 1:2.

Images