CN107507976A - Composite mixed manganate cathode material for lithium of a kind of lithium aluminium boron and preparation method thereof - Google Patents

Abstract

The invention discloses a lithium-aluminum-boron compound-doped lithium manganate positive electrode material and a preparation method thereof. The chemical formula of the lithium-aluminum-boron compound-doped lithium manganate is: Li _1+x Mn _2‑x Al _x O ₄ · 0.3xLiBO ₂ , where 0<x≦0.2. In the invention, the lithium-aluminum-boron compound-doped lithium manganate positive electrode material with regular appearance and uniform particle size is prepared by adopting the method of two-stage roasting after spray spheronization. By introducing lithium, aluminum, and boron into the lithium manganese oxide lattice, boron forms Li _1+x Mn _2‑x Al _x O ₄ ·0.3xLiBO ₂ solid solution with lithium manganate in the form of LiBO ₂ , effectively inhibiting The dissolution of manganese in the electrolyte is improved, the strength of the Mn-O bond is improved, the structural stability of the material is enhanced, and the high-temperature cycle performance of lithium manganate is significantly improved. The preparation process of the material is simple and easy to control, and the cost is low and it is easy to realize large-scale production.

Description

Lithium-aluminum-boron compound-doped lithium manganate cathode material and preparation method thereof

technical field

The invention belongs to the field of cathode material preparation, and in particular relates to a lithium-aluminum-boron compound-doped lithium manganate cathode material and a preparation method thereof.

Background technique

Lithium-ion battery is a new energy battery successfully developed from the late 1980s to the early 1990s. It is currently widely used in daily electronic products and is also the first choice for electric vehicle power batteries.

The choice of cathode material determines the performance of lithium-ion batteries. Spinel-type lithium manganese oxide has become the first choice for power battery cathode materials due to its low price, rich manganese resources, high safety, and environmental friendliness. However, the poor high-temperature cycle performance and structural stability of lithium manganate greatly limit the industrialization of lithium manganate for power batteries, and it is urgent to improve it.

The Chinese patent document with the publication number CN 102195042 A discloses a high-performance lithium ion battery cathode material lithium manganese oxide and its preparation method, which adopts a solid-phase method, after ball milling a lithium source, a manganese source, and a compound doped with a metal element. Calcination, cooling to room temperature, ball milling again, and finally high-temperature sintering, crushing, and classification to obtain high-performance lithium-ion battery positive electrode material lithium manganate.

The Chinese patent document with the publication number CN 105244492 A discloses a boron-containing lithium ion positive electrode material and a preparation method thereof, in which composite oxide particles are added to a boron-containing salt solution to form a slurry mixture, and then a doping metal element containing at least A kind of M salt solution is reacted to form a coating layer on the surface of the composite oxide particles, stirred and dried, and heat treated to obtain the final product.

The above processes adopt high-temperature solid-phase method and liquid-phase method respectively. The lithium manganate particles prepared by the solid-phase method are not uniform, the shape is irregular, and the product capacity decays quickly; the lithium manganate prepared by the liquid-phase method has a relatively consistent particle size distribution, but the liquid-phase method often uses expensive reagents, requires a long drying time, and is accompanied by a complicated reaction process. Therefore, the production process conditions of the liquid-phase method are not easy to control, the production cost is high, and it is not suitable for industrial production.

Contents of the invention

The purpose of the present invention is to provide a preparation method of a lithium manganate positive electrode material doped with lithium aluminum boron compound; aiming to prepare a positive electrode material with excellent high-temperature cycle performance and structural stability.

Another object of the present invention is to provide a lithium-aluminum-boron composite doped lithium manganate cathode material prepared by the preparation method.

A preparation method of lithium manganese oxide positive electrode material doped with lithium aluminum boron compound, according to the stoichiometric ratio of chemical formula Li _1+x Mn _2-x Al _x O ₄ 0.3xLiBO ₂ , lithium source, manganese source, aluminum source Place the boron source in the medium, ball mill and mix, where 0<x≤0.2;

The ball-milled material is spray-dried and pelletized to obtain raw mixture pellets;

The mixture green balls are calcined in one stage at 350-650° C., and then calcined in two stages at 650-890° C. to prepare the lithium-aluminum-boron compound-doped lithium manganate cathode material.

The present invention adopts spray drying and pelletizing technology, which can prepare porous spherical lithium manganate particles with regular shape and uniform particle size, avoiding the use of expensive reaction reagents, and using cheap materials such as lithium carbonate for spraying, while ensuring the regular shape of the material At the same time, the cost of materials is reduced. The preparation process is simple and easy to control, and the cost is low and it is easy to realize large-scale production. Therefore, the present invention will be beneficial to the mass production of the spinel lithium manganese oxide cathode material and improve its performance.

The use of spray-drying pelletization, combined with the above-mentioned two-stage calcination mechanism, helps to prepare porous spherical particles with regular appearance, uniform particle size, and lithium manganate cathode material with good electrochemical performance.

In the present invention, the lithium source is a water-soluble compound and/or oxide of Li.

Preferably, the lithium source is at least one of lithium nitrate, lithium carbonate, lithium acetate and lithium hydroxide.

In the present invention, the manganese source is manganese oxides, salts and the like.

Preferably, the manganese source is at least one of manganese dioxide, trimanganese tetraoxide, manganese carbonate, manganese nitrate or manganese acetate.

Preferably, the boron source is boron oxide and/or boric acid.

Preferably, the aluminum source is aluminum hydroxide.

In the present invention, the lithium source, manganese source, boron source, and aluminum source are mixed in the ball mill of the medium according to the stoichiometric ratio of the chemical formulas Li, Mn, B, and Al.

Preferably, x is 0.02-0.2; more preferably 0.05-0.15; still more preferably 0.05-0.1.

Preferably, the molar ratio of lithium in the lithium source to manganese in the manganese source exceeds the theoretical stoichiometric ratio. It can help to compensate for the volatilization of lithium at high temperature.

Preferably, the medium is at least one of acetone, deionized water, and absolute ethanol.

Preferably, the mass ratio of liquid to solid in the ball milling process is (8-10):1, the rotation speed is 250-450 r/min, and the ball milling time is 2-20 hours.

Further preferably, in the ball milling process, the mass ratio of liquid to solid is 10:1, the rotation speed is 300 r/min, and the ball milling time is 4 hours.

Preferably, in the process of spray drying and pelletizing, the inlet temperature is 200-400°C, and the outlet temperature is 60-150°C.

More preferably, the inlet temperature of the spray-drying pellets is 300°C, and the outlet temperature is 100°C.

Preferably, the particle size of the mixed material green pellets prepared by spray-drying and pelletizing is 10-20 microns.

Further preferably, the average particle diameter of the mixed material green pellets prepared by spray-drying and pelletizing is 15 μm.

Preferably, the heating rate of the one-stage calcination and the second-stage calcination process is less than or equal to 12°C/min; preferably 2-8°C/min.

If the heating rate is too fast, the reaction will be incomplete and impurities will be produced, resulting in a decrease in the electrochemical performance of the material. At the above heating rate, it is helpful to prepare positive electrode materials with high phase purity and excellent electrical properties.

Preferably, the temperature of one stage of calcination is 600-650°C.

Preferably, the one-stage calcination time is 3-20 hours; more preferably 3-15 hours; still more preferably 6-10 hours.

Preferably, the heating rate of one stage of calcination is 2°C/min, the calcination temperature is 650°C, and the calcination time is 6h.

Preferably, the temperature of the second-stage roasting process is 800-850°C.

At the above-mentioned two-stage sintering temperature, a suitable two-stage sintering time can produce a positive electrode material with excellent electrochemical performance. Excessive calcination time will lead to excessive growth of the primary particles of the material, resulting in a decrease in electrochemical performance.

Preferably, the calcination time of the two-stage calcination process is 3-30 hours; more preferably 3-24 hours; still more preferably 13-20 hours.

Further preferably, the heating rate of the second-stage calcination process is 2° C./min, the calcination temperature is 850° C., and the calcination time is 13 hours.

The invention also discloses a lithium-aluminum-boron composite doped lithium manganate cathode material prepared by the preparation method. Through the preparation method, lithium aluminum boron is in-situ doped in lithium manganese oxide, which helps to significantly improve the electrical performance of the positive electrode material.

Preferably, the chemical formula of lithium manganese oxide doped with lithium aluminum boron compound is: Li _1+x Mn _2-x Al _x O ₄ ·0.3xLiBO ₂ ; wherein, 0<x≤0.2.

The compound-doped lithium aluminum boron lithium manganate material provided by the present invention is used as a positive electrode material, which can unexpectedly improve the cycle performance and structural stability of the lithium manganate positive electrode material.

It is found through research that, preferably, x is 0.05-0.15. Under this preferred condition, the electrical performance of the positive electrode material is better.

Compared with prior art, the beneficial effect of the present invention:

In the invention, the lithium-aluminum-boron compound-doped lithium manganate positive electrode material with regular appearance and uniform particle size is prepared by adopting the method of two-stage roasting after spray spheronization. By introducing lithium, aluminum, and boron into the lattice of lithium manganate, aluminum replaces manganese and enters the lattice of lithium manganate, while boron forms Li _1+x Mn ₂ with lithium manganate in the form of LiBO _{2 -x} Al _x O ₄ ·0.3xLiBO ₂ solid solution, which effectively inhibits the dissolution of manganese in the electrolyte, improves the strength of the Mn-O bond, thereby enhancing the structural stability of the material, and the high-temperature cycle performance of lithium manganate has been improved. Significantly increased.

Description of drawings

Fig. 1 is the XRD diagram of the lithium manganate cathode material doped with lithium aluminum boron composite in Example 1, it can be seen that the product fully complies with the lithium manganate standard card JCPDS: 71-3120 (the lower spectrum line in Fig. 1 ) .

Fig. 2 is the SEM image of the lithium manganate cathode material doped with lithium aluminum boron composite in Example 1, and the obtained lithium manganate material is a porous spherical particle with a particle size of 15 μm;

Fig. 3 is the high temperature (55 ℃) cycle life diagram of the lithium manganate cathode material doped with lithium aluminum boron compound in embodiment 1;

4 is a high-temperature (55° C.) cycle life diagram of the undoped modified lithium manganate positive electrode material in Comparative Example 1;

detailed description

The present invention will be further elaborated below in conjunction with specific embodiments.

The spray pelletizing method of following embodiment and comparative example is:

Raise the inlet temperature of the spray drying equipment to 200-400°C, use a peristaltic pump to feed deionized water to control the outlet temperature at 60-150°C, then replace the deionized water with a uniformly mixed slurry for spray drying.

Example 1

A lithium-aluminum-boron compound-doped lithium manganate cathode material, the preparation method of which is as follows:

Preparation of lithium manganate positive electrode material with general chemical formula Li _1.1 Mn _1.9 Al _0.1 O ₄ 0.03LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, the ball milling time is 4h, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried and pelletized to obtain a mixture green pellet (10～ 20 microns); heat the mixture green balls at 2°C/min to 650°C for 6h, continue to heat up to 850°C for 13h, and cool naturally to room temperature to obtain the lithium-aluminum-boron composite-doped lithium manganate The positive electrode material is Li _1.1 Mn _1.9 Al _0.1 O ₄ ·0.03LiBO ₂ .

The charge-discharge performance test of all embodiment and comparative example gained product is carried out according to the following methods:

Mix the obtained lithium manganate, acetylene black, and PVDF in a mass ratio of 8:1:1, add NMP, grind into a uniform slurry, coat it on an aluminum foil, place it in a vacuum drying phase at 120°C for 12 hours, and replace it with lithium metal The sheet is the negative electrode, and 1MLiPF ₆ is the electrolyte to make a CR2025 button battery. Electrochemical test voltage range is 3 ~ 4.3V, 0.2C (1C = 148mAh/g) cycle for 2 cycles, then 1C cycle, high temperature test, the temperature is 55 ° C (NMP: N-methyl-2-pyrrolidone; PVDF: polytetrafluoroethylene). As shown in Figure 2, the lithium manganate material obtained in Example 1 is a porous spherical particle with an average particle diameter of 15 μm. As shown in FIG. 3 , the first discharge specific capacity of the lithium manganate material obtained in Example 1 is 103 mAh/g, and the capacity retention rate after 200 high-temperature cycles is 95%.

Example 2

Preparation of lithium manganese oxide positive electrode material with general chemical formula Li _1.05 Mn _1.95 Al _0.05 O ₄ 0.015LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, the ball milling time is 4h, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried and pelletized to obtain a mixture green pellet (10～ 20 microns); heat the mixture green balls at 2°C/min to 650°C for 6h, continue to heat up to 850°C for 13h, and cool naturally to room temperature to obtain the lithium-aluminum-boron composite-doped lithium manganate The positive electrode material is Li _1.05 Mn _1.95 Al _0.05 O ₄ ·0.015LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The initial discharge specific capacity of the material is 105mAh/g, and the capacity retention rate after 200 high-temperature cycles is 93%.

Example 3

Preparation of lithium manganese oxide positive electrode material with general chemical formula Li _1.15 Mn _1.85 Al _0.15 O ₄ 0.045LiBO ₂ , weighing manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mixing them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, the ball milling time is 4h, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried and pelletized to obtain a mixture green pellet (10～ 20 microns); heat the mixture green balls at 2°C/min to 650°C for 6h, continue to heat up to 850°C for 13h, and cool naturally to room temperature to obtain the lithium-aluminum-boron composite-doped lithium manganate The positive electrode material is Li _1.15 Mn _1.85 Al _0.15 O ₄ ·0.045LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The initial discharge specific capacity of the material is 102 mAh/g, and the capacity retention rate after 200 high-temperature cycles is 92%.

Example 4

Preparation of lithium manganate positive electrode material with general chemical formula Li _1.2 Mn _1.8 Al _0.2 O ₄ 0.06LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, the ball milling time is 4h, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried and pelletized to obtain a mixture green pellet (10～ 20 microns); heat the mixture green balls at 2°C/min to 650°C for 6h, continue to heat up to 850°C for 13h, and cool naturally to room temperature to obtain the lithium-aluminum-boron composite-doped lithium manganate The positive electrode material is Li _1.2 Mn _1.8 Al _0.2 O ₄ ·0.06LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The initial discharge specific capacity of the material is 99mAh/g, and the capacity retention rate after 200 high-temperature cycles is 91%.

Example 5

Preparation of lithium manganese oxide positive electrode material with general chemical formula Li _1.02 Mn _1.98 Al _0.02 O ₄ 0.006LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, the ball milling time is 4h, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried and pelletized to obtain a mixture green pellet (10～ 20 microns); heat the mixture green balls at 2°C/min to 650°C for 6h, continue to heat up to 850°C for 13h, and cool naturally to room temperature to obtain the lithium-aluminum-boron composite-doped lithium manganate The positive electrode material is Li _1.02 Mn _1.98 Al _0.02 O ₄ ·0.006LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The initial discharge specific capacity of the material is 109mAh/g, and the capacity retention rate after 200 high-temperature cycles is 90%.

Example 6

Preparation of lithium manganate positive electrode material with general chemical formula Li _1.1 Mn _1.9 Al _0.1 O ₄ 0.03LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, the ball milling time is 4h, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried and pelletized to obtain a mixture green pellet (10～ 20 microns); heat the mixture green balls at 8°C/min to 650°C for 6h, continue to heat up to 850°C for 13h, and cool naturally to room temperature to obtain the lithium-aluminum-boron composite-doped lithium manganate The positive electrode material is Li _1.1 Mn _1.9 Al _0.1 O ₄ ·0.03LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The initial discharge specific capacity of the material is 101mAh/g, and the capacity retention rate after 200 high-temperature cycles is 94%.

Example 7

Preparation of lithium manganate positive electrode material with general chemical formula Li _1.1 Mn _1.9 Al _0.1 O ₄ 0.03LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, the ball milling time is 4h, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried to make pellets to obtain raw mixture pellets (10～ 20 microns); heat the mixture green balls at 2°C/min to 650°C for 6h, continue to heat up to 850°C for 20h, and cool naturally to room temperature to obtain the lithium-aluminum-boron composite-doped lithium manganate The positive electrode material is Li _1.1 Mn _1.9 Al _0.1 O ₄ ·0.03LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The initial discharge specific capacity of the material is 102mAh/g, and the capacity retention rate after 200 high-temperature cycles is 92%.

Example 8

Preparation of lithium manganate positive electrode material with general chemical formula Li _1.1 Mn _1.9 Al _0.1 O ₄ 0.03LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, the ball milling time is 4h, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried and pelletized to obtain a mixture green pellet (10～ 20 microns); heat the mixture raw balls at 2°C/min to 650°C for 10 hours, continue to heat up to 850°C for 15 hours, and naturally cool to room temperature to obtain the lithium-aluminum-boron composite-doped lithium manganate The positive electrode material is Li _1.1 Mn _1.9 Al _0.1 O ₄ ·0.03LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The first discharge specific capacity of the material is 103mAh/g, and the capacity retention rate after 200 high-temperature cycles is 91%.

Example 9

Preparation of lithium manganate positive electrode material with general chemical formula Li _1.1 Mn _1.9 Al _0.1 O ₄ 0.03LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, the ball milling time is 4h, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried and pelletized to obtain a mixture green pellet (10～ 20 microns); heat the mixture green balls at 2°C/min to 620°C for 6h, continue to heat up to 800°C for 20h, and cool naturally to room temperature to obtain the lithium-aluminum-boron composite-doped lithium manganate The positive electrode material is Li _1.1 Mn _1.9 Al _0.1 O ₄ ·0.03LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The initial discharge specific capacity of the material is 102 mAh/g, and the capacity retention rate after 200 high-temperature cycles is 91%.

Example 10

This embodiment discusses the two-stage sintering time, specifically as follows:

Preparation of lithium manganate positive electrode material with general chemical formula Li _1.1 Mn _1.9 Al _0.1 O ₄ 0.03LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, the ball milling time is 4h, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried and pelletized to obtain green pellets of the mixture; The mixed material green balls were heated at 2°C/min to 650°C for 6 hours, continued to heat up to 850°C for 30 hours, and naturally cooled to room temperature to obtain the lithium manganate cathode material Li _1.1 Mn _1.9 Al _0.1 O ₄ ·0.03LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The initial discharge specific capacity of the material is 101mAh/g, and the capacity retention rate after 200 high-temperature cycles is 88%.

Example 11

This embodiment discusses a period of sintering time, specifically as follows:

Preparation of lithium manganate positive electrode material with general chemical formula Li _1.1 Mn _1.9 Al _0.1 O ₄ 0.03LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, the ball milling time is 4h, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried and pelletized to obtain green pellets of the mixture; The mixed material green balls were heated at 2°C/min to 650°C for 20 hours, continued to heat up to 850°C for 20 hours, and naturally cooled to room temperature to obtain the lithium-aluminum-boron compound-doped lithium manganate cathode material Li _1.1 Mn _1.9 Al _0.1 O ₄ ·0.03LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The initial discharge specific capacity of the material is 100mAh/g, and the capacity retention rate after 200 high-temperature cycles is 87%.

Comparative example 1

This comparative example discusses no doping and no spray granulation operation, as follows:

The general chemical formula is LiMn ₂ O ₄ lithium manganese oxide cathode material, weigh manganese tetraoxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water, the liquid-solid mass ratio is 10:1, and the ball milling speed is 300r/min , the ball milling time is 4h, ball milling to get a uniformly mixed slurry, after drying, heat up to 650°C at 2°C/min for 6h, continue to heat up to 850°C for 13h, cool naturally to room temperature, and get undoped modified manganese lithium acid cathode material LiMn ₂ O ₄ . The electrochemical test method of this product is the same as that of Example 1. As shown in Figure 4, the initial discharge specific capacity of the material is 112mAh/g, and the capacity retention rate after 200 high-temperature cycles is 74%.

Comparative example 2

This comparative example discusses not doping and carries out spray granulation operation, specifically as follows:

The general chemical formula is LiMn ₂ O ₄ lithium manganese oxide cathode material, weigh manganese tetraoxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water, the liquid-solid mass ratio is 10:1, and the ball milling speed is 300r/min , the ball milling time is 4 hours, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried and pelletized to obtain a mixture green pellet; the mixture raw pellet is heated at 2°C/min to 650°C for heat preservation After 6 hours, continue to heat up to 850° C. for 13 hours, and cool down to room temperature naturally to obtain undoped and modified lithium manganate cathode material LiMn ₂ O ₄ . The electrochemical test method of this product is the same as that of Example 1. As shown in Figure 4, the initial discharge specific capacity of the material is 111mAh/g, and the capacity retention rate after 200 high-temperature cycles is 78%.

Comparative example 3

This comparison does not discuss the spray granulation operation, as follows:

Preparation of lithium manganate positive electrode material with general chemical formula Li _1.1 Mn _1.9 Al _0.1 O ₄ 0.03LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, and the ball milling time is 4h. The ball milling is to obtain a uniformly mixed slurry. After drying, the temperature is raised to 650°C at 2°C/min and kept for 6h, and the temperature is continued to 850°C. Keeping it warm for 13 hours, cooling to room temperature naturally, and obtaining the doped and modified lithium manganate cathode material Li _1.1 Mn _1.9 Al _0.1 O ₄ ·0.03LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The initial discharge specific capacity of the material is 101mAh/g, and the capacity retention rate after 200 high-temperature cycles is 82%. Compared with Example 1, this comparative example did not carry out the spray-drying treatment, and the capacity retention rate of the prepared material decreased by nearly 10% compared with Example 1.

Comparative example 4

This comparative example discusses the case where x is greater than 0.2, as follows:

Preparation of lithium manganate positive electrode material with general chemical formula Li _1.3 Mn _1.7 Al _0.3 O ₄ 0.09LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, and the ball milling time is 4h. The ball milling is to obtain a uniformly mixed slurry. After drying, the temperature is raised to 650°C at 2°C/min and kept for 6h, and the temperature is continued to 850°C. Keeping it warm for 13 hours, cooling down to room temperature naturally, and obtaining a doped and modified lithium manganate positive electrode material Li _1.3 Mn _1.7 Al _0.3 O ₄ ·0.09LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The initial discharge specific capacity of the material is 95mAh/g, and the capacity retention rate after 200 high-temperature cycles is 73%.

Comparative example 5

This comparative study explores the influence of the heating rate during the sintering process, as follows:

Preparation of lithium manganate positive electrode material with general chemical formula Li _1.1 Mn _1.9 Al _0.1 O ₄ 0.03LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, the ball milling time is 4h, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried and pelletized to obtain green pellets of the mixture; The mixed material green balls were heated at 20°C/min to 650°C for 6 hours, continued to heat up to 850°C for 13 hours, and naturally cooled to room temperature to obtain the lithium-aluminum-boron composite doped lithium manganate cathode material Li _1.1 Mn _1.9 Al _0.1 O ₄ ·0.03LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The initial discharge specific capacity of the material is 80mAh/g, and the capacity retention rate after 200 high-temperature cycles is 65%.

Comparative example 6

This comparative example discusses the second-stage sintering temperature, which is as follows:

Preparation of lithium manganate positive electrode material with general chemical formula Li _1.1 Mn _1.9 Al _0.1 O ₄ 0.03LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, the ball milling time is 4h, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried and pelletized to obtain green pellets of the mixture; The mixed material green balls were heated at 2°C/min to 650°C for 6 hours, continued to heat up to 900°C for 20 hours, and naturally cooled to room temperature to obtain the lithium manganate cathode material Li _1.1 Mn _1.9 composite doped with lithium aluminum boron. Al _0.1 O ₄ ·0.03LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The initial discharge specific capacity of the material is 101 mAh/g, and the capacity retention rate after 200 high-temperature cycles is 68%.

Comparative example 7

This comparative example discusses one-stage sintering temperature, which is as follows:

Preparation of lithium manganate positive electrode material with general chemical formula Li _1.1 Mn _1.9 Al _0.1 O ₄ 0.03LiBO ₂ , weigh manganese tetraoxide, aluminum hydroxide, boron oxide and lithium carbonate according to the stoichiometric ratio and mix them with deionized water , the liquid-solid mass ratio is 10:1, the ball milling speed is 300r/min, the ball milling time is 4h, and the ball milling is to obtain a uniformly mixed slurry; the uniformly mixed slurry is spray-dried and pelletized to obtain green pellets of the mixture; The mixed material green balls were heated at 2°C/min to 200°C for 6 hours, continued to heat up to 850°C for 20 hours, and naturally cooled to room temperature to obtain the lithium manganate cathode material Li _1.1 Mn _1.9 composite doped with lithium aluminum boron. Al _0.1 O ₄ ·0.03LiBO ₂ . The electrochemical test method of this product is the same as that of Example 1. The initial discharge specific capacity of the material is 99mAh/g, and the capacity retention rate after 200 high-temperature cycles is 70%.

As can be seen from the above examples and comparative examples, as long as various parameters such as the amount of doping elements, the heating rate, etc. are within the specified range during the preparation process, the prepared modified lithium manganate positive electrode material will have Excellent high temperature cycle performance.

Claims (10)

1. the preparation method of the composite mixed manganate cathode material for lithium of a kind of lithium aluminium boron, it is characterised in that by chemical formula Li_{1+ x}Mn_2-xAl_xO₄·0.3xLiBO₂Stoichiometric proportion, lithium source, manganese source, silicon source and boron source are placed in medium, ball milling mixing, its In, 0 ＜ x≤0.2；

Material after ball milling is subjected to spray drying pelletizing, obtains compound green-ball；

By described compound green-ball after 350~650 DEG C of next section of roastings, then the two-stage calcination at 650~890 DEG C, it is made The composite mixed manganate cathode material for lithium of described lithium aluminium boron.

2. the preparation method of the composite mixed manganate cathode material for lithium of lithium aluminium boron as claimed in claim 1, it is characterised in that x For 0.02~0.2；Preferably 0.05~0.15.

3. the preparation method of the composite mixed manganate cathode material for lithium of lithium aluminium boron as claimed in claim 1, it is characterised in that be situated between Matter is at least one of acetone, deionized water, absolute ethyl alcohol；

The solid mass ratio of the liquid of mechanical milling process is (8~10): 1,250~450r/min of rotating speed, and Ball-milling Time is 2~20h.

4. the preparation method of the composite mixed manganate cathode material for lithium of lithium aluminium boron according to claim 1, it is characterised in that It is spray-dried in balling process, 200~400 DEG C of inlet temperature, 60~150 DEG C of outlet temperature.

5. the preparation method of the composite mixed manganate cathode material for lithium of lithium aluminium boron according to claim 1, it is characterised in that One section of roasting, the heating rate of two-stage calcination process are less than or equal to 12 DEG C/min；Preferably 2~8 DEG C/min.

6. the preparation method of the composite mixed manganate cathode material for lithium of lithium aluminium boron, its feature exist according to claim 1 or 5 In the temperature of one section of roasting process is 600~650 DEG C；One section of roasting time is 3~20h；Preferably 3~15h；It is further excellent Elect 6~10h as.

7. the preparation method of the composite mixed manganate cathode material for lithium of lithium aluminium boron according to claim 1, it is characterised in that The temperature of two-stage calcination process is 800~850 DEG C.

8. the preparation method of the composite mixed manganate cathode material for lithium of lithium aluminium boron according to claim 1 or 7, its feature exist In the roasting time of two-stage calcination process is 3~30h；Preferably 3~24h；More preferably 13~20h.

9. the preparation method of the composite mixed manganate cathode material for lithium of lithium aluminium boron according to claim 1, it is characterised in that Described lithium source is at least one of lithium nitrate, lithium carbonate, lithium acetate and lithium hydroxide；

Described manganese source is at least one of manganese dioxide, mangano-manganic oxide, manganese carbonate, manganese nitrate or manganese acetate；

Described boron source is boron oxide and/or boric acid；

Described silicon source is aluminium hydroxide.

10. the composite mixed manganate cathode material for lithium of a kind of lithium aluminium boron, it is characterised in that using any one of claim 1~9 institute The preparation method stated is made.