Cobalt-free lithium-rich manganese-based positive electrode material and preparation method thereof

Abstract

The application discloses a cobalt-free lithium-rich manganese-based positive electrode material and a preparation method thereof. 1+x Ni y Mn z O2 positive electrode material, wherein 0 The lithium ion battery prepared from the cobalt-free lithium-rich manganese-based positive electrode material has the advantages of large specific capacity, excellent rate performance, large cycle number and stable performance, and the defects of poor structural stability and poor rate performance of the cobalt-free lithium-rich manganese material are compensated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery cathode materials, and particularly relates to a cobalt-free lithium-rich manganese-based cathode material and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries are widely used in various fields from 3C electronic products to electric vehicles due to their light weight, high energy density, no memory effect, long cycle life and environmental friendliness. With the development of the times, people have increasingly high demand for lithium ion batteries with higher capacity and higher safety. Lithium-rich manganese-based cathode materials are considered as the most potential next-generation lithium ion battery cathode materials due to their advantages of >250 mAh / g of super-high discharge specific capacity, low cost, non-toxicity and high thermal stability. Due to the factors of resource shortage and high price of cobalt, cobalt-free lithium-rich manganese-based cathode materials have become a trend of lithium ion battery research. Cobalt can improve the structural stability of the material and improve the cycle and rate performance, so compared with conventional lithium-rich manganese-based cathode materials, the structural stability and rate performance of cobalt-free lithium-rich manganese-based cathode materials are deteriorated, and there are problems of high first irreversible capacity, serious cycle attenuation and poor rate performance. Therefore, it is of great significance to develop a cobalt-free lithium-rich manganese-based cathode material with high specific capacity, good cycle stability and rate performance. SUMMARY

[0003] Based on the technical problems existing in the background art, the present application provides a cobalt-free lithium-rich manganese-based cathode material and a preparation method thereof.

[0004] The preparation method of the cobalt-free lithium-rich manganese-based cathode material provided by the present application is a preparation method of TaS2-coated Li 1+x Ni y Mn z O2 cathode material, wherein 0

[0005] S1, dissolving a nickel salt and a manganese salt in deionized water to obtain a mixed salt solution; adding a complexing agent to the mixed salt solution under stirring, heating and reacting until a colloid is formed, then adding a stabilizer, aging, filtering, washing, heating and reacting to obtain a nickel-manganese mixed sol;

[0006] S2, mixing monolayer TaS2 nanosheets with a sub-nanopore structure, the nickel-manganese mixed sol and an excess of a lithium source, stirring uniformly, then removing the solvent and calcining to obtain the cobalt-free lithium-rich manganese-based cathode material.

[0007] Preferably, the method for preparing the monolayer TaS2 nanosheet with sub-nanopore structure comprises: mixing a halide of Ta and elemental sulfur, ball-milling, and then placing in a heating tube, heating and vaporizing under an inert atmosphere, collecting the solid product in a condensation zone to obtain TaS2; etching the TaS2 with an organic acid solution, and then centrifuging to obtain the monolayer TaS2 nanosheet with sub-nanopore structure.

[0008] Preferably, the step of heating and vaporizing comprises: first increasing the temperature to 450-550°C at a temperature increasing rate of 1-3°C / min, maintaining for 30-60 min, and then increasing the temperature to 950-1100°C at a temperature increasing rate of 5-8°C / min, maintaining for 10-30 min.

[0009] Preferably, the specific step of etching the TaS2 with an organic acid solution comprises: adding the TaS2 into an organic acid solution, stirring at 40-80°C for 30-90 min.

[0010] Preferably, the halide of Ta is TaCl5, TaF5, or a combination thereof.

[0011] Preferably, the organic acid is at least one of oxalic acid, formic acid, acetic acid, citric acid, and succinic acid; the concentration of the organic acid solution is 0.05-10 mol / L; preferably, the concentration of the organic acid solution is 0.1-1.5 mol / L.

[0012] Preferably, the lithium source is at least one of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium acetate; the nickel salt is at least one of nickel nitrate, nickel sulfate, nickel acetate, and nickel chloride; the manganese salt is at least one of manganese nitrate, manganese sulfate, manganese acetate, and manganese chloride.

[0013] Preferably, the complexing agent is at least one of sodium nitrilotriacetate, tartaric acid, diethanolamine, and triethanolamine; the number of moles of the complexing agent is 1%-50% of the sum of the number of moles of nickel ions and manganese ions; preferably, the number of moles of the complexing agent is 10%-30% of the sum of the number of moles of nickel ions and manganese ions.

[0014] Preferably, the stabilizer is at least one of cetyltrimethylammonium bromide, polyethylene glycol, sorbitol, aluminum trichloride, Span 20, Span 60, Tween 40, and Tween 80; the number of moles of the stabilizer is 1%-25% of the sum of the number of moles of nickel ions and manganese ions; preferably, the number of moles of the stabilizer is 5%-15% of the sum of the number of moles of nickel ions and manganese ions.

[0015] Preferably, in S1, the temperature of the heating reaction is 50-100°C, and the time is 20-80 h.

[0016] Preferably, in S1, the aging time is 1-8h; preferably, in S2, the aging time is 3-6h.

[0017] Preferably, the number of moles of the monolayer TaS2 nanosheet with sub-nanopore structure is 0.1%-1.5% of the sum of the number of moles of nickel ions and manganese ions; preferably, the number of moles of the monolayer TaS2 nanosheet with sub-nanopore structure is 0.5%-1.2% of the sum of the number of moles of nickel ions and manganese ions.

[0018] Preferably, in S2, the step of calcining comprises: first heating to 400-600℃, holding for 4-8h, and then heating to 800-1050℃, holding for 12-24h.

[0019] A cobalt-free lithium-rich manganese-based positive electrode material is prepared by the preparation method.

[0020] The beneficial effects of the present application are as follows:

[0021] The present application adopts a sol-gel method to prepare a nickel-manganese precursor sol under the synergistic action of a complexing agent and a stabilizer, mixes the sol, a lithium salt and a monolayer conductive TaS2 nanosheet with sub-nanopore structure, evaporates the solvent to obtain a mixture gel, and then performs high-temperature solid-phase calcination to obtain a monolayer conductive TaS2-coated cobalt-free lithium-rich manganese-based positive electrode material. Compared with existing lithium-rich manganese material preparation methods, the cobalt-free lithium-rich manganese material prepared by the present application has a complete crystal structure, a uniform shape and a uniform particle size distribution. The coated TaS2 material itself has conductivity, the original TaS2 material has a multilayer structure, atoms and some molecules can be inserted into the layers to form interlayer compounds, and the monolayer TaS2 separated by acid etching has a sub-nanopore structure and is coated on the surface of the cobalt-free lithium-rich manganese-based positive electrode material, which plays a supporting role and stabilizes the structure on the one hand, and increases the conductivity and improves the rate performance on the other hand, while the sub-nanopore structure does not affect the transmission of lithium ions. The lithium ion battery prepared from the material has a large specific capacity, excellent rate performance and a large number of cycle times, and stable performance, which makes up for the defects of poor structural stability and poor rate performance of the cobalt-free lithium-rich manganese material. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A scanning electron microscope photo of the cobalt-free lithium-rich manganese-based positive electrode material prepared in Example 1.

[0023] Figure 2 Cycle curves of lithium ion batteries respectively prepared from the cobalt-free lithium-rich manganese-based positive electrode materials in Comparative Examples 1-2 and Example 1. DETAILED DESCRIPTION

[0024] The technical solutions of the present application will be described in detail below through specific examples.

[0025] Example 1

[0026] A preparation method of a cobalt-free lithium-rich manganese-based positive electrode material, the cobalt-free lithium-rich manganese-based positive electrode material being TaS2-coated Li 1.2 Ni 0.2 Mn 0.6 O2 positive electrode material, a preparation method thereof comprising the following steps:

[0027] S1, 0.2 mol of nickel acetate and 0.6 mol of manganese acetate are dissolved in deionized water to obtain a mixed salt solution with a concentration of 1 mol / L; 0.15 mol of diethanolamine is added dropwise to the mixed salt solution under stirring, and the reaction is heated in a water bath at 45 DEG C until a colloid is formed, then 0.08 mol of Span 20 is added, aged for 4 h, filtered and washed, transferred to a sealed tank for sealing, and heated at 70 DEG C for 40 h to obtain a nickel-manganese mixed sol;

[0028] S2, 0.01 mol of single-layer TaS2 nanosheet with a sub-nanopore structure, the nickel-manganese mixed sol prepared in S1, and 1.3 mol of lithium carbonate are mixed and stirred uniformly, then the solvent is evaporated, and the temperature is first raised to 450 DEG C in an air atmosphere, and kept for 6 h, then raised to 900 DEG C, and kept for 16 h, and naturally cooled to obtain the product.

[0029] The preparation method of the single-layer TaS2 nanosheet with a sub-nanopore structure is as follows:

[0030] 0.1 mol of TaCl5 and 0.2 mol of sulfur are mixed and ball milled, then placed in a heating tube, and heated at a temperature increasing rate of 3 DEG C / min to 500 DEG C in an inert atmosphere, kept for 60 min, then heated at a temperature increasing rate of 6 DEG C / min to 1000 DEG C, kept for 15 min, and heated to gasification, and the solid product is collected in a condensation zone to obtain TaS2; the TaS2 is added to a 0.5 mol / L oxalic acid solution, stirred at 60 DEG C for 60 min, then centrifuged to obtain the single-layer TaS2 nanosheet with a sub-nanopore structure.

[0031] Example 2

[0032] A preparation method of a cobalt-free lithium-rich manganese-based positive electrode material, the cobalt-free lithium-rich manganese-based positive electrode material being TaS2-coated Li 1.2 Ni 0.2 Mn 0.6 O2 positive electrode material, a preparation method thereof comprising the following steps:

[0033] S1, 0.2 mol of nickel nitrate and 0.6 mol of manganese nitrate were dissolved in deionized water to obtain a mixed salt solution with a concentration of 1.5 mol / L; 0.2 mol of sodium nitrilotriacetate was added dropwise to the mixed salt solution under stirring, and the reaction was heated in a water bath at 45℃ until a colloid was formed, then 0.16 mol of cetyltrimethylammonium bromide was added, aged for 5 h, filtered and washed, transferred to a sealed tank for sealing, and heated at 70℃ for 40 h to obtain a nickel-manganese mixed sol;

[0034] S2, 0.012 mol of single-layer TaS2 nanosheets with sub-nanopore structure, the nickel-manganese mixed sol prepared in S1, and 1.5 mol of lithium hydroxide were mixed and stirred uniformly, then the solvent was evaporated, and the temperature was first raised to 400℃ in an air atmosphere, and kept for 4 h, then raised to 800℃, and kept for 12 h, and then naturally cooled to obtain the product.

[0035] The preparation method of the single-layer TaS2 nanosheets with sub-nanopore structure is as follows:

[0036] 0.1 mol of TaF5 and 0.2 mol of sulfur were mixed and ball milled, then placed in a heating tube, and heated to 550℃ at a rate of 3℃ / min in an inert atmosphere, kept for 60 min, then heated to 1100℃ at a rate of 6℃ / min, kept for 10 min, and then gasified, and the solid product was collected in a condensation zone to obtain TaS2; the TaS2 was added to a 1.5 mol / L formic acid solution, stirred at 40℃ for 90 min, and then centrifuged to obtain single-layer TaS2 nanosheets with sub-nanopore structure.

[0037] Example 3

[0038] A preparation method of a cobalt-free lithium-rich manganese-based positive electrode material, the cobalt-free lithium-rich manganese-based positive electrode material being a TaS2-coated Li 1.2 Ni 0.2 Mn 0.6 O2 positive electrode material, the preparation method comprising the following steps:

[0039] S1, 0.2 mol of nickel nitrate and 0.6 mol of manganese nitrate were dissolved in deionized water to obtain a mixed salt solution with a concentration of 1.5 mol / L; 0.2 mol of sodium nitrilotriacetate was added dropwise to the mixed salt solution under stirring, and the reaction was heated in a water bath at 45℃ until a colloid was formed, then 0.16 mol of cetyltrimethylammonium bromide was added, aged for 5 h, filtered and washed, transferred to a sealed tank for sealing, and heated at 70℃ for 40 h to obtain a nickel-manganese mixed sol;

[0040] S2, 0.012 mol of single-layer TaS2 nanosheets with sub-nanopore structure, the nickel-manganese mixed sol prepared in S1 and 1.5 mol of lithium carbonate were mixed and stirred uniformly, and then the solvent was evaporated. The mixture was first heated to 600 DEG C under an air atmosphere, and then naturally cooled after being kept at 600 DEG C for 8 h and being heated to 1050 DEG C for 24 h.

[0041] The preparation method of the single-layer TaS2 nanosheets with sub-nanopore structure is as follows:

[0042] 0.1 mol of TaCl5 and 0.2 mol of sulfur were mixed and ball-milled, and then placed in a heating tube. Under an inert atmosphere, the mixture was first heated to 450 DEG C at a heating rate of 3 DEG C / min, and then heated to 950 DEG C at a heating rate of 6 DEG C / min for 30 min. The solid product was collected in a condensation zone to obtain TaS2. The TaS2 was added to a 0.1 mol / L formic acid solution, stirred at 80 DEG C for 30 min, and then centrifuged to obtain single-layer TaS2 nanosheets with sub-nanopore structure.

[0043] Comparative Example 1

[0044] Comparative Example 1 is a conventional sol-gel method for preparing a cobalt-free lithium-rich manganese-based positive electrode material, which is as follows:

[0045] A preparation method of a cobalt-free lithium-rich manganese-based positive electrode material, the cobalt-free lithium-rich manganese-based positive electrode material being Li 1.2 Ni 0.2 Mn 0.6 O2 positive electrode material, the preparation method comprising the following steps:

[0046] S1, 0.2 mol of nickel acetate and 0.6 mol of manganese acetate were dissolved in deionized water to obtain a mixed salt solution with a concentration of 1 mol / L. While stirring, 0.15 mol of diethanolamine was added dropwise to the mixed salt solution, and the mixture was heated in a water bath at 45 DEG C until a colloid was formed. Then, 0.08 mol of Span 20 was added, and the mixture was aged for 4 h, filtered, washed, transferred to a sealed tank, and heated at 70 DEG C for 40 h to obtain a nickel-manganese mixed sol.

[0047] S2, the nickel-manganese mixed sol prepared in S1 and 1.3 mol of lithium carbonate were mixed and stirred uniformly, and then the solvent was evaporated. The mixture was first heated to 450 DEG C under an air atmosphere, and then naturally cooled after being kept at 450 DEG C for 6 h and being heated to 900 DEG C for 16 h.

[0048] Comparative Example 2

[0049] Comparative Example 2 is a conventional oxide, i.e., an alumina-coated cobalt-free lithium-rich manganese-based positive electrode material, which is as follows:

[0050] A preparation method of a cobalt-free lithium-rich manganese-based positive electrode material, the cobalt-free lithium-rich manganese-based positive electrode material being Li 1.2 Ni 0.2 Mn 0.6 O2 positive electrode material, the preparation method comprising the following steps:

[0051] S1, dissolving 0.2 mol of nickel acetate and 0.6 mol of manganese acetate in deionized water to obtain a mixed salt solution with a concentration of 1 mol / L; under stirring, adding 0.15 mol of diethanolamine dropwise into the mixed salt solution, heating the reaction under water bath at 45℃ until a colloid is formed, then adding 0.08 mol of Span 20, aging for 4 h, filtering, washing, transferring into a sealed tank for sealing, heating the reaction at 70℃ for 40 h, and obtaining a nickel-manganese mixed sol;

[0052] S2, mixing 0.01 mol of nano-Al2O3, the nickel-manganese mixed sol obtained in S1, and 1.3 mol of lithium carbonate, stirring uniformly, then evaporating the solvent, first increasing the temperature to 450℃ under air atmosphere, keeping the temperature for 6 h, then increasing the temperature to 900℃, keeping the temperature for 16 h, and naturally cooling, and obtaining the product.

[0053] Test examples

[0054] The cobalt-free lithium-rich manganese materials in Examples 1, 2, 3 and Comparative Examples 1-2 were respectively made into 3 Ah wound soft-pack batteries, and the 0.1C first discharge and first efficiency, 1C / 2C / 3C rate discharge performance and 25℃ cycle test were respectively tested under 2.0-4.6V voltage, and the test results are shown in Table 1 and Figure 2 .

[0055] Table 1 3 Ah soft-pack battery 0.1C charge-discharge and rate discharge test results

[0056] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 0.1C initial capacity / mAh / g 285.58 284.74 285.10 260.17 270.44 Initial efficiency 90.17％ 89.85％ 90.01％ 80.17％ 84.21％ 2C rate discharge capacity retention 99.08％ 99.03％ 99.15％ 92.57％ 94.21％ 3C rate discharge capacity retention 98.38％ 97.97％ 98.17％ 84.41％ 88.55％

[0057] The test results in Table 1 and Figure 2It can be seen from the test results that, compared with the cobalt-free lithium-rich manganese material in Comparative Example 1, the 0.1C first discharge, the initial efficiency, the 2C, 3C rate discharge and the cycle performance of the cobalt-free lithium-rich manganese material in Example 1 are obviously better than those of Comparative Example 1. This is because the cobalt-free lithium-rich manganese material prepared by the conventional preparation method has relatively dispersed particles, the crystal structure is relatively incomplete, the prepared battery has small specific capacity, less cycle times and poor performance; secondly, the structure of the uncoated cobalt-free lithium-rich manganese material is more unstable, and the performance is relatively poorer. Compared with the cobalt-free lithium-rich manganese material in Comparative Example 2, both are coated cobalt-free lithium-rich manganese materials, but the 0.1C first discharge, the initial efficiency, the 2C, 3C rate discharge and the cycle performance of the cobalt-free lithium-rich manganese material in Example 1 are obviously better than those of Comparative Example 2. This is mainly because TaS2 itself has good conductivity, and single-layer TaS2 not only retains strong conductivity, but also has sub-nanometer pore structure. As a coating, on the one hand, it plays a supporting role and stabilizes the structure; on the other hand, it increases the conductivity and improves the rate performance, and the sub-nanometer pore structure does not affect the transmission of lithium ions. Therefore, the lithium ion battery prepared from the material has large specific capacity, excellent rate performance, more cycle times, stable performance, and makes up for the defects of poor structural stability and poor rate performance of the cobalt-free lithium-rich manganese material.

[0058] The above description is only the preferred embodiment of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art can make equivalent replacement, change or modification according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A method for preparing a cobalt-free, lithium-rich manganese-based cathode material, characterized in that, The cobalt-free lithium-rich manganese-based cathode material is TaS2-coated Li. 1+x Ni y Mn z The O2 cathode material, wherein 0 < x < 0.5, 0 < y < 0.4, 0 < z < 0.7, and x + y + z = 1, is prepared by the following steps: S1. Dissolve nickel salt and manganese salt in deionized water to obtain a mixed salt solution; add a complexing agent to the mixed salt solution under stirring, heat the reaction until a colloid is formed, then add a stabilizer, age, filter, wash, heat the reaction to obtain a nickel-manganese mixed sol; S2. Mix monolayer TaS2 nanosheets with sub-nanoporous structure, nickel-manganese mixed sol and excess lithium source, stir evenly, remove solvent and calcine to obtain the product; The method for preparing the monolayer TaS2 nanosheets with sub-nanoporous structure includes: mixing and ball-milling Ta halides and elemental sulfur, placing the mixture in a heating tube, heating and vaporizing it under an inert atmosphere, collecting the solid product in the condensation zone to obtain TaS2; adding TaS2 to an organic acid solution, stirring at 40~80℃ for 30~90 min, and then centrifuging to obtain monolayer TaS2 nanosheets with sub-nanoporous structure.

2. The method for preparing the cobalt-free lithium-rich manganese-based cathode material according to claim 1, characterized in that, The heating and vaporization steps include: first heating to 450~550℃ and holding for 30~60 minutes, then heating to 950~1100℃ and holding for 10~30 minutes.

3. The method for preparing the cobalt-free lithium-rich manganese-based cathode material according to claim 1, characterized in that, The organic acid is at least one of oxalic acid, formic acid, acetic acid, citric acid, and succinic acid; the concentration of the organic acid solution is 0.05~10 mol / L.

4. The method for preparing the cobalt-free lithium-rich manganese-based cathode material according to claim 1, characterized in that, The lithium source is at least one of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium acetate; the nickel salt is at least one of nickel nitrate, nickel sulfate, nickel acetate, and nickel chloride; and the manganese salt is at least one of manganese nitrate, manganese sulfate, manganese acetate, and manganese chloride.

5. The method for preparing the cobalt-free lithium-rich manganese-based cathode material according to claim 1, characterized in that, The complexing agent is at least one selected from sodium nitrilotriacetate, tartaric acid, diethanolamine, and triethanolamine; the molar amount of the complexing agent is 1% to 50% of the sum of the molar amounts of nickel ions and manganese ions. The stabilizer is at least one of cetyltrimethylammonium bromide, polyethylene glycol, sorbitol, aluminum trichloride, Span 20, Span 60, Tween 40, and Tween 80; the molar amount of the stabilizer is 1% to 25% of the sum of the molar amounts of nickel ions and manganese ions.

6. The method for preparing the cobalt-free lithium-rich manganese-based cathode material according to claim 1, characterized in that, In S1, the heating reaction temperature is 50~100℃ and the time is 20~80h; In S1, the aging time is 1 to 8 hours.

7. The method for preparing the cobalt-free lithium-rich manganese-based cathode material according to claim 1, characterized in that, The molar number of the monolayer TaS2 nanosheets with sub-nanoporous structure is 0.1% to 1.5% of the sum of the molar numbers of nickel ions and manganese ions.

8. The method for preparing the cobalt-free lithium-rich manganese-based cathode material according to claim 1, characterized in that, In S2, the calcination steps include: first heating to 400~600℃ and holding for 4~8 hours, then heating to 800~1050℃ and holding for 12~24 hours.

9. A cobalt-free, lithium-rich manganese-based cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

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