A polycaprolactone-coated lithium manganate and a preparation method thereof

Abstract

The application provides a preparation method of lithium manganate coated with polycaprolactone and belongs to the technical field of lithium ion batteries. The lithium manganate coated with polycaprolactone is prepared, compared with traditional lithium manganate, under the same solid content, the viscosity of the positive electrode slurry of the lithium ion battery can be effectively reduced; in the positive electrode slurry with the same viscosity, the polycaprolactone coated lithium manganate provided by the application can effectively improve the solid content of the positive electrode slurry, so that the solvent consumption is saved, and the cost is reduced. At the same time, due to the increase of the solid content, the volatilization speed of the positive electrode slurry solvent can be accelerated, so that the coating speed of the positive electrode sheet is increased, and the production efficiency is improved; the polycaprolactone coated lithium manganate provided by the application has more uniform slurry dispersion and better fluidity, the coated electrode sheet is uniform and smooth, the areal density is unchanged, the electrode sheet thickness can be reduced, and the energy density of the lithium ion battery and the cycle performance and rate performance of the battery are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a polycaprolactone-coated lithium manganese oxide and its preparation method. Background Technology

[0002] Lithium-ion batteries (LIBs), as an energy storage device distinct from traditional energy sources, dominate the energy storage field. In the modern portable application product market, lithium-ion batteries are widely used in 3C digital products, power banks, power tools, and wearable electronic products. Lithium-ion batteries possess advantages such as high specific energy, low self-discharge, good cycle performance, no memory effect, and environmental friendliness, making them the most promising high-efficiency rechargeable battery and the fastest-growing chemical energy storage power source.

[0003] Lithium manganese oxide (LiMn2O4), as a cathode material used in lithium-ion batteries, has been widely adopted in recent years due to its good safety, cost-effectiveness, and environmental friendliness. Currently, industrially produced lithium manganese oxide consists of secondary particles formed from the agglomeration of small primary particles. When preparing lithium-ion battery cathode slurries, this results in defects such as high viscosity and poor slurry dispersion, leading to relatively low overall energy density, poor rate performance, and poor cycle performance in lithium manganese oxide batteries. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a polycaprolactone-coated lithium manganese oxide and its preparation method. The polycaprolactone-coated lithium manganese oxide obtained by this invention can reduce the viscosity of the positive electrode slurry of lithium-ion batteries, save battery manufacturing costs, and improve the electrochemical performance of lithium-ion batteries.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing polycaprolactone-coated lithium manganese oxide, comprising the following steps:

[0007] The polycaprolactone solution was mixed with the lithium manganese oxide in the form of a spray to obtain polycaprolactone-coated lithium manganese oxide.

[0008] Preferably, the molecular weight of the polycaprolactone is 80,000 to 100,000.

[0009] Preferably, the solvent of the polycaprolactone solution is N-methylpyrrolidone; the mass ratio of polycaprolactone to N-methylpyrrolidone in the polycaprolactone solution is 1:(8-15).

[0010] Preferably, the method for preparing the polycaprolactone solution includes the following steps:

[0011] Polycaprolactone and N-methylpyrrolidone are heated and mixed to obtain a polycaprolactone solution; the heating and mixing temperature is 50-60℃.

[0012] Preferably, in the polycaprolactone-coated lithium manganese oxide, the mass of polycaprolactone is 0.1 to 0.3% of the mass of lithium manganese oxide.

[0013] Preferably, the D50 particle size of the lithium manganese oxide is 8–20 μm.

[0014] Preferably, the method for preparing the lithium manganese oxide includes the following steps:

[0015] Manganese dioxide and lithium carbonate were ball-milled and sintered to obtain lithium manganate.

[0016] Preferably, the molar ratio of Mn to Li in the manganese dioxide and lithium carbonate is 2:1.05 to 1.12.

[0017] Preferably, the ball milling mixing time is 1.5 to 3 hours;

[0018] The sintering temperature is 750–900℃, and the holding time is 10–20 h.

[0019] This invention provides a method for preparing polycaprolactone-coated lithium manganese oxide, comprising the following steps: mixing a polycaprolactone solution with the lithium manganese oxide via spray to obtain polycaprolactone-coated lithium manganese oxide. In this invention, polycaprolactone (PCL) possesses good biocompatibility and good organic polymer compatibility. When preparing cathode slurry, it can rapidly dissolve in the cathode slurry solvent, effectively eliminating the polarity of the materials, resulting in more uniform mixing of the materials in the slurry, improving slurry fluidity, and significantly enhancing the processing performance and chemical properties of the cathode material. This invention coats the surface of lithium manganese oxide with a layer of polycaprolactone. Compared with traditional lithium manganese oxide, this effectively reduces the viscosity of lithium-ion battery cathode slurry at the same solid content. Furthermore, in cathode slurries of the same viscosity, the polycaprolactone-coated lithium manganese oxide provided by this invention effectively increases the solid content of the cathode slurry, thereby achieving solvent savings and cost reduction. Meanwhile, the increased solid content accelerates the evaporation rate of the positive electrode slurry solvent on the electrode surface, thereby increasing the coating speed of the positive electrode and improving production efficiency. At the same solid content, the lithium-ion battery positive electrode material prepared by this invention can reduce slurry viscosity by 10-60%; at the same viscosity, its slurry solid content can be increased by 5-15%, saving 15-35% of solvent.

[0020] This invention uses polycaprolactone-coated lithium manganese oxide as the cathode material to prepare cathode slurry. The resulting cathode slurry has the advantages of uniform dispersion and good fluidity. The coated cathode sheet is uniform and smooth, which can effectively improve the energy density, cycle performance and rate performance of lithium-ion batteries. Moreover, the electrode thickness can be reduced by 5-10% while keeping the areal density unchanged. Detailed Implementation

[0021] This invention provides a method for preparing polycaprolactone-coated lithium manganese oxide, comprising the following steps:

[0022] The polycaprolactone solution was mixed with the lithium manganese oxide in the form of a spray to obtain polycaprolactone-coated lithium manganese oxide.

[0023] In this invention, the molecular weight of the polycaprolactone is preferably 80,000 to 100,000, and more preferably 90,000.

[0024] In this invention, the solvent of the polycaprolactone solution is preferably N-methylpyrrolidone; the mass ratio of polycaprolactone to N-methylpyrrolidone in the polycaprolactone solution is preferably 1:8 to 15, more preferably 1:10 to 12.

[0025] In this invention, the method for preparing the polycaprolactone solution preferably includes the following steps:

[0026] Polycaprolactone is heated and mixed with a dispersing solvent to obtain a polycaprolactone solution; the heating and mixing temperature is 50-60°C, preferably 55°C. This invention does not have special requirements for the mixing process; any mixing method well known to those skilled in the art can be used, such as stirring.

[0027] In this invention, the mass of polycaprolactone in the polycaprolactone-coated lithium manganese oxide is preferably 0.1 to 0.3% of the mass of lithium manganese oxide, more preferably 0.2%.

[0028] In this invention, the D50 particle size of the lithium manganese oxide is preferably 8-20 μm, more preferably 10-15 μm.

[0029] In this invention, the method for preparing the lithium manganese oxide preferably includes the following steps:

[0030] Manganese dioxide and lithium carbonate were sequentially ball-milled, mixed, and calcined to obtain lithium manganate.

[0031] In this invention, the manganese dioxide is preferably electrolytic manganese dioxide. In this invention, the molar ratio of Mn to Li in the manganese dioxide and lithium carbonate is preferably 2:1.05–1.12, more preferably 2:1.08–1.1.

[0032] In this invention, the ball milling is preferably carried out in an inclined mill. In this invention, the grinding media of the ball mill is preferably agate balls, and the ball-to-material ratio is preferably 1-2:1, more preferably 1.5:1.

[0033] In this invention, the ball milling mixing time is preferably 1.5 to 3 hours, more preferably 2 to 2.5 hours.

[0034] In this invention, the calcination is preferably carried out in a muffle furnace; the calcination atmosphere is preferably air. In this invention, the calcination temperature is preferably 750–900°C, more preferably 800–850°C, and the holding time is preferably 10–20 h, more preferably 15 h. In this invention, the heating rate to the calcination temperature is preferably 100–300°C / h, more preferably 200°C / h.

[0035] In this invention, a polycaprolactone solution is mixed with prepared lithium manganese oxide in the form of a spray to obtain polycaprolactone-coated lithium manganese oxide.

[0036] In this invention, the mixing is preferably carried out in a high-speed mixer.

[0037] After mixing, the present invention preferably dries the resulting mixture. The present invention does not have special requirements for the drying method, and any drying method known to those skilled in the art can be used.

[0038] The present invention provides a polycaprolactone-coated lithium manganese oxide prepared by the above preparation method.

[0039] This invention coats lithium manganese oxide with a layer of polycaprolactone. Compared with traditional lithium manganese oxide, this effectively reduces the viscosity of lithium-ion battery cathode slurry at the same solid content. Furthermore, in cathode slurries of the same viscosity, the polycaprolactone-coated lithium manganese oxide provided by this invention effectively increases the solid content, thereby saving solvent and reducing costs. Simultaneously, the increased solid content accelerates the evaporation rate of the cathode slurry on the electrode surface, thereby increasing the coating speed of the cathode sheet and improving production efficiency. At the same solid content, the lithium-ion battery cathode material prepared by this invention can reduce the slurry viscosity by 10-60%; at the same viscosity, the slurry can increase the solid content by 5-15%, saving 15-35% of solvent.

[0040] This invention uses polycaprolactone-coated lithium manganese oxide as the cathode material to prepare cathode slurry. The resulting cathode slurry has the advantages of uniform dispersion and good fluidity. The coated cathode sheet is uniform and smooth, which can effectively improve the energy density, cycle performance and rate performance of lithium-ion batteries. Moreover, the electrode thickness can be reduced by 5-10% while keeping the areal density unchanged.

[0041] The following detailed description, in conjunction with embodiments, illustrates a polycaprolactone-coated lithium manganese oxide and its preparation method provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] (1) Preparation of lithium manganese oxide

[0044] Electrolytic manganese dioxide and lithium carbonate were weighed according to a molar ratio of Mn:Li = 2:1.1 and placed in an inclined mill. Agate balls were added at a ball-to-material ratio of 2:1, and the mixture was ball-milled for 3 hours. The mixture was then sintered at 800°C for 15 hours in an air atmosphere in a muffle furnace. After cooling, lithium manganese oxide was obtained with a D50 particle size of 10 μm.

[0045] (2) Preparation of polycaprolactone (PCL) solution

[0046] Weigh NMP and heat it to 50°C. Weigh PCL with a molecular weight of 80,000 to 100,000 according to the mass ratio of PCL:NMP = 1:10. Add the PCL to NMP while stirring. Once the PCL is completely dissolved, you will have a PCL solution.

[0047] (3) Preparation of polycaprolactone-coated lithium manganese oxide

[0048] Lithium manganese oxide is placed in a high-speed mixer, and a PCL solution is weighed out at 0.15% of the weight of lithium manganese oxide. The solution is then uniformly sprayed onto the surface of lithium manganese oxide in the form of a spray under high-speed dispersion. After all the solution is sprayed, it is spray-dried to obtain polycaprolactone-coated lithium manganese oxide.

[0049] Example 2

[0050] The difference from Example 1 is that in the polycaprolactone-coated lithium manganese oxide, the weight of PCL is 0.2% of the weight of lithium manganese oxide.

[0051] Example 3

[0052] The difference from Example 1 is that in the polycaprolactone-coated lithium manganese oxide, the weight of PCL is 0.25% of the weight of lithium manganese oxide.

[0053] Test case

[0054] The polycaprolactone-coated lithium manganese oxide obtained in Examples 1-3 was mixed with NMP solvent to prepare a lithium-ion battery cathode slurry. Lithium manganese oxide without polycaprolactone coating was used as a comparative example to prepare a lithium-ion electrode cathode slurry. Its solid content and electrochemical performance are shown in Table 1.

[0055] Table 1. Solid content and electrochemical performance of the cathode slurries prepared in Examples 1-3 and Comparative Example 1

[0056]

[0057] As can be seen from Table 1, the polycaprolactone-coated lithium manganese oxide obtained by the present invention can reduce the viscosity of the positive electrode slurry of lithium-ion batteries, increase the solid content, and improve the electrochemical performance of lithium-ion batteries.

[0058] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing polycaprolactone-coated lithium manganese oxide, comprising the following steps: The polycaprolactone solution was mixed with the lithium manganate in the form of a spray to obtain polycaprolactone-coated lithium manganate. The molecular weight of the polycaprolactone is 80,000 to 100,000; The solvent for the polycaprolactone solution is N-methylpyrrolidone; the mass ratio of polycaprolactone to N-methylpyrrolidone in the polycaprolactone solution is 1:(8~15). In the polycaprolactone-coated lithium manganese oxide, the mass of polycaprolactone is 0.1~0.3% of the mass of lithium manganese oxide; The D50 particle size of the lithium manganese oxide is 8~20 μm; The method for preparing the polycaprolactone solution includes the following steps: Polycaprolactone and N-methylpyrrolidone were heated and mixed to obtain a polycaprolactone solution; the heating and mixing temperature was 50~60 °C. The polycaprolactone-coated lithium manganese oxide is used to mix with NMP solvent to obtain a lithium-ion battery cathode slurry.

2. The preparation method according to claim 1, characterized in that, The method for preparing the lithium manganese oxide includes the following steps: Manganese dioxide and lithium carbonate were ball-milled and sintered to obtain lithium manganate.

3. The preparation method according to claim 2, characterized in that, The molar ratio of Mn to Li in the manganese dioxide and lithium carbonate is 2:1.05~1.

12.

4. The preparation method according to claim 2, characterized in that, The ball milling mixing time is 1.5~3 h; The sintering temperature is 750~900 ℃, and the holding time is 10~20 h.

5. The polycaprolactone-coated lithium manganese oxide prepared by the preparation method according to any one of claims 1 to 4.

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