CN105938899B - A kind of preparation method and application of fast ion conductor coating modified lithium ion battery positive electrode material - Google Patents

Abstract

The invention discloses a preparation method and application of a fast ion conductor-coated positive electrode material for a lithium ion battery; the method comprises the following steps: mixing nano-scale aluminum powder and positive electrode material by ball milling, stirring and reacting with a lithium-containing solution to obtain an aluminum hydroxide colloid package Coated cathode material precursor; the aluminum hydroxide colloid-coated cathode material precursor is calcined at high temperature to obtain a lithium ion battery cathode material with dense, uniform and stable fast ion conductor coating modification, which can be used for A lithium-ion battery cathode with high rate performance and high cycle performance is prepared, and the preparation method has the characteristics of low cost, simple operation, and environmental friendliness, and can be applied to large-scale industrial production.

Description

A kind of preparation method of fast ion conductor coating modified lithium ion battery positive electrode material and application

technical field

The invention relates to a method for preparing a positive electrode material for a modified lithium ion battery, in particular to a method for preparing a positive electrode material for a modified lithium ion battery coated with a fast ion conductor, and its application in preparing a lithium ion battery with high cycle life, It belongs to the technical field of lithium ion batteries.

Background technique

Nowadays, the rapid development of mobile electronic devices, such as smart phones, digital cameras, notebook computers, and electric vehicles and hybrid vehicles, has contributed to the rapid advancement of lithium-ion secondary battery technology. However, the current cathode materials for lithium-ion batteries, such as lithium cobalt oxide, lithium spinel manganate, and lithium iron phosphate, all have the disadvantage of low cycle life and cannot meet the requirements of future pure electric devices. Therefore, research and development of a cathode material with high cycle life has become a common goal of researchers all over the world.

Coating modification is a protection method that uses a material with excellent physical and chemical properties to form a uniform coating layer on the surface of the target material particles. The researchers used the fast ion conductor to coat the cathode material. The results show that the cathode material modified by the fast ion conductor coating has better rate performance and cycle performance. However, in the traditional coating method, the preparation process of fast ion conductor has the disadvantages of complicated operation and high cost, and it is difficult to realize large-scale industrial production. Therefore, it is imperative to find a simple, low-cost and environmentally friendly preparation method.

SUMMARY OF THE INVENTION

Aiming at the defects of the prior art, the purpose of the present invention is to provide a method for the fast ion conductor LiAlO ₂ coating layer to be dense and uniform, and the fast ion conductor to coat modified lithium ion battery positive electrode material with good stability. The operation is simple, the cost is low, the environment is friendly, and it is beneficial to industrial production.

Another object of the present invention is to provide an application of a fast ion conductor coating modified lithium ion battery positive electrode material in a lithium ion battery, which can obtain a lithium ion battery with high rate performance and long cycle life.

In order to achieve the above technical purpose, the present invention provides a method for preparing a positive electrode material of a fast ion conductor coated modified lithium ion battery. At a temperature of ℃～80℃, the reaction is stirred to obtain an aluminum hydroxide colloid-coated cathode material precursor; the fast ion conductor LiAlO ₂ coated cathode material precursor is calcined at a temperature of 500℃～900℃ to obtain.

In a preferred solution, the mass of the ultrafine (nanoscale) aluminum powder is 0.5% to 10.0% of the mass of the positive electrode material.

In a more preferred solution, the positive electrode material is LiM ₂ O ₄ with spinel structure, M=Ni and/or Mn; and/or LiMO ₂ with layered structure, M=at least one of Ni, Co, and Mn; and/or lithium-rich manganese positive electrode material xLi ₂ MnO ₃ ·(1-x)LiMO ₂ , 0.1<x<0.9, M=at least one of Ni, Co, and Mn.

In a preferred solution, the concentration of the lithium-containing solution is between 0.1 mol/L and 10 mol/L.

In a more preferred solution, the lithium-containing solution contains at least one lithium salt selected from LiCl, LiNO ₃ , LiOH, Li ₂ CO ₃ , and CH ₃ COOLi.

In a preferred solution, the ultra-fine (nano-scale) aluminum powder is pre-activated by an acid etching method.

A more preferred solution, the acid etching method is to soak in hydrochloric acid, sulfuric acid or nitric acid with a concentration of 0.1 mol/L to 1.0 mol/L.

In a preferred solution, the ball milling is realized by a planetary ball mill or a roller ball mill, the ball mill rotating speed is 400-800p/min, and the ball-milling time is 1h-8h.

In a more preferred solution, the calcination time is 5h to 20h.

The particle size distribution of the ultrafine (nano-scale) aluminum powder used in the present invention is 50 nm to 500 nm. Ultrafine (nano-scale) aluminum powder is a common product available in the market.

The present invention also provides an application of the fast ion conductor coating modified lithium ion battery positive electrode material, and the fast ion conductor coating modified lithium ion battery positive electrode material is applied to prepare a lithium ion battery.

The method for preparing a fast ion conductor coating modified lithium ion battery positive electrode material of the present invention comprises the following specific steps:

1) Using a planetary ball mill to process ultrafine (nanoscale) aluminum powder with a particle size between 50nm and 500nm and LiM ₂ O ₄ (M=Ni, and/or Mn) having a spinel structure, and/or LiMO ₂ with layered structure (M=at least one of Ni, Co, Mn), and/or lithium-rich manganese positive electrode material xLi ₂ MnO ₃ ·(1-x)LiMO ₂ (0.1<x<0.9, M=Ni , at least one of Co, Mn), mixed by planetary ball mill or roller ball mill, the ball milling speed is controlled at 400 ~ 600 r/min, and the ball milling time is controlled between 1h ~ 5h; nanoscale aluminum powder and positive electrode material The mass percentage of aluminum powder is (0.5%～10.0%): 100%; the ball milling medium can choose at least one of agate balls, steel balls or ceramic balls; ultra-fine (nano-scale) aluminum powder can be activated by acid etching method for pretreatment ;

2) Use at least one of LiCl, LiNO ₃ , LiOH, Li ₂ CO ₃ , and CH ₃ COOLi as the lithium source to prepare a lithium-containing solution with a concentration ranging from 0.1 mol/L to 10 mol/L, and then step 1 ) was added to the lithium-containing solution, and was continuously stirred for 0.5 h to 5.0 h in a water bath at a temperature of 40 to 80 °C to obtain a cathode material coated with xLi ⁺ ·Al(OH) ₃ ·yH ₂ O ;

3) The product after the reaction in step 2) is subjected to suction filtration, and the precipitate obtained after washing is placed in a vacuum oven and dried at 80° C. for 12 hours to obtain a dried xLi ⁺ ·Al(OH) ₃ ·yH ₂ O coating Positive electrode material precursor.

4) Transfer the precursor obtained in step 3) into a muffle furnace, keep the temperature at 500°C to 900°C for 5 to 20 hours, and naturally cool to room temperature to obtain a fast ion conductor LiAlO ₂ modified and coated lithium ion positive electrode Material.

The method for preparing a lithium ion battery by coating the modified lithium ion positive electrode material with the fast ion conductor LiAlO ₂ in the present invention: coating the modified lithium ion positive electrode material with the fast ion conductor LiAlO ₂ with a conductive agent (conductive carbon black) and a viscose. The binding agent (PVDF) and a small amount of NMP were thoroughly mixed to form a uniform paste, which was coated on the aluminum foil substrate as a test electrode, and a coin cell was made with metal lithium as the counter electrode. The electrolyte was 1M LiPF ₆ / EC :DMC(V:V=1:1).

In the technical scheme of the present invention, the superfine aluminum powder is subjected to surface activation treatment by the ball milling method or acid etching method, and the activated nano-aluminum powder reacts with water under appropriate conditions to form aluminum hydroxide, and the surface of the generated hydroxide adsorbs Lithium ions are charged and can be uniformly adsorbed on the surface of the positive electrode material to form a coating layer of xLi ⁺ ·Al(OH) ₃ ·yH ₂ O, and the xLi ⁺ ·Al(OH) ₃ ·yH ₂ O is further dehydrated at high temperature LiAlO ₂ nanosheets are generated, and the generated LiAlO ₂ nanosheets are grown in situ on the surface of the positive electrode material to obtain a dense, uniform and stable LiAlO ₂ coating layer.

Relative to the prior art, the beneficial technical effects brought by the technical solution of the present invention:

The fast ion conductor (LiAlO ₂ ) prepared by the technical scheme of the present invention covers the LiAlO ₂ coating layer in the positive electrode material of the lithium ion battery, which is dense, uniform and stable, and can effectively prevent electrolysis during the charging and discharging cycle of the lithium ion battery. The corrosive effect of the liquid on the positive electrode material greatly prolongs the cycle life of the lithium ion battery, as well as the rapid transport of lithium ions, and improves the electrochemical performance of the lithium ion battery.

The method for preparing the fast ion conductor (LiAlO ₂ ) to coat the positive electrode material of the lithium ion battery of the present invention fully utilizes the reaction of nano-scale aluminum powder with water to generate aluminum hydroxide sol, and the chlorine hydroxide sol has good adsorption performance and The principle of decomposition at high temperature to generate corresponding oxides. A dense, uniform and stable fast ion conductor layer is formed on the surface of the positive electrode material, which can effectively prevent the positive electrode active material from being dissolved and lost in contact with the electrolyte solution, greatly prolonging the cycle life of the battery; at the same time, greatly improving the ionic and electronic conductivity of the electrode , improving the electrochemical performance of lithium-ion batteries.

The fast ion conductor layer _- coated lithium ion battery positive electrode material of the present invention is prepared by a low-temperature synthesis of a precursor material combined with high-temperature sintering. In the coating modification method, there are disadvantages such as high cost of raw materials, complicated operation process and cumbersome process.

The method for preparing the fast ion conductor LiAlO ₂ coated lithium ion battery positive electrode material of the present invention activates the metal surface by ball milling or acid etching, greatly improves the reaction efficiency of metal and water, simplifies the process, and moderates the conditions.

The fast ion conductor (LiAlO ₂ ) of the present invention coats the positive electrode material of the lithium ion battery to prepare the positive electrode, and is applied to the lithium ion battery, showing excellent cycle performance and greatly prolonging the cycle life.

Description of drawings

[Fig. 1] is a scanning electron microscope (SEM) image of the LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode material before coating modification in Example 1.

[ FIG. 2 ] is a scanning electron microscope (SEM) image of the LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode material after LiAlO ₂ coating and modification in Example 1.

[Fig. 3] shows the LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode material without coating modification and the LiNi _0.5 Co _0.2 Mn _0.3 O ₂ cathode material obtained in Example ₁ after coating modification with LiNi _0.5 Co _0.2 Mn _0.3 O ₂ cathode material for 100 cycles Performance graph.

Detailed ways

The following examples are intended to further illustrate the content of the present invention; and the protection scope of the claims of the present invention is not limited by the examples.

Example 1

(1) According to the mass percentage of LiAlO ₂ relative to the positive electrode material of 1%, respectively weigh the ultra-fine (nano-scale) aluminum powder with a particle size of 300 nm and the LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode material, and add them to a container with a capacity of 250 mL. In a steel ball mill with agate balls, adjust the speed to 400p/min and grind for 2h.

(2) Add the aluminum powder after grinding and activation in step (1) and LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode material mixture into a three-necked flask containing 100 mL of LiCl solution with a concentration of 1 mol/L, and stir the reaction at 50° C. 1h.

(3) washing the precipitate obtained in step (2) with deionized water 3 times, then washing with absolute ethanol 3 times, then filtering, and keeping the filter cake in a blast oven at 80° C. for 12 hours to obtain xLi ⁺ ·Al (OH) ₃ ·yH ₂ O coats the precursor of the positive electrode material.

(4) The precursor obtained in step (3) is put into a crucible, and the temperature is kept at 450° C. for 5 hours to obtain a LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode material coated with LiAlO ₂ .

(5) Weigh 0.48g of the above-obtained LiAlO ₂ coated and modified LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode material, add 0.05g conductive carbon black as a conductive agent, 0.05g PVDF as a binder, add A small amount of NMP was ground and mixed thoroughly to form a uniform paste, which was coated on the aluminum foil substrate as a test electrode, and a button battery was made with metal lithium as the counter electrode. The electrolyte was 1M LiPF ₆ /EC:DMC (V:V =1:1), the test charge-discharge rate is 1C.

The modified LiNi _0.5 Co _0.2 Mn _0.3 O ₂ cathode material prepared by LiAlO ₂ in this example is used for coating, and its material characterization and electrochemical performance are shown in Figures 1 to 3:

It can be seen from Fig. 1 that the uncoated LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode material has a quasi-spherical structure composed of primary particles with a size of 500-800 nm, and the surface is smooth.

It can be seen from Fig. 2 that the LiNi _0.5 Co _0.2 Mn _0.3 O ₂ cathode material particle surface modified by LiAlO ₂ coating has a uniformly distributed flaky coating layer.

Figure 3 shows that the electrode made of the modified LiNi _0.5 Co _0.2 Mn _0.3 O ₂ cathode material coated with LiAlO ₂ has a constant current discharge at a rate of 1 C at room temperature, and the specific capacity can still be maintained at 100 cycles after 100 cycles. 180 mAh/g; showing good cycle performance.

Example 2

(1) According to the mass percentage of LiAlO ₂ relative to the positive electrode material of 0.5%, respectively weigh the ultra-fine aluminum powder (nano-scale) with a particle size of 100 nm and LiNi _0.85 Co _0.05 Mn _0.1 O ₂ positive electrode material, add them to a capacity of 250 mL containing Agate balls in a steel ball mill, and then adjust the speed to 500p/min and grind for 4h.

(2) Add the mixture of aluminum powder and LiNi _0.85 Co _0.05 Mn _0.1 O ₂ positive electrode material after grinding and activation in step (1) into a three-necked flask containing 100 mL of a 0.5 mol/L LiNO ₃ solution, and at 60° C. The reaction was stirred for 2h.

(3) washing the precipitate obtained in step (2) with deionized water 3 times, then washing with absolute ethanol 3 times, then filtering, and keeping the filter cake in a blast oven at 80° C. for 12 hours to obtain xLi ⁺ ·Al (OH) ₃ ·yH ₂ O coats the precursor of the positive electrode material.

(4) The precursor obtained in step (3) is put into a crucible and kept at 500° C. for 8 hours to obtain a LiNi _0.85 Co _0.05 Mn _0.1 O ₂ positive electrode material coated with LiAlO ₂ .

(5) Weigh 0.48g of the above-obtained LiAlO ₂ coated and modified LiNi _0.85 Co _0.05 Mn _0.1 O ₂ positive electrode material, add 0.05g conductive carbon black as a conductive agent, 0.05g PVDF as a binder, add A small amount of NMP was ground and mixed thoroughly to form a uniform paste, which was coated on the aluminum foil substrate as a test electrode, and a button battery was made with metal lithium as the counter electrode. The electrolyte was 1M LiPF ₆ /EC:DMC (V:V =1:1), the test charge-discharge rate is 1C.

The modified LiNi 0.85 Co 0.05 Mn 0.1 O ₂ positive electrode material prepared in this example was used to coat the modified LiNi _0.85 Co _0.05 Mn _0.1 O ₂ positive electrode material and assembled with metal lithium sheets to form a button battery. When discharged at a constant current of 1C at room temperature, after 100 cycles The specific capacity can still be maintained at 188mAh/g, showing good cycle performance.

Example 3

(1) According to the mass percentage of LiAlO ₂ relative to the positive electrode material of 2%, respectively weigh the ultrafine aluminum powder (nano-scale) with a particle size of 100 nm and the LiNi _0.333 Co _0.333 Mn _0.333 O ₂ positive electrode material, and add them to a 250mL capacity Agate balls in a steel ball mill, and then adjust the speed to 600p/min and grind for 5h.

(2) Add the mixture of the aluminum powder and LiNi _0.333 Co _0.333 Mn _0.333 O ₂ positive electrode material after grinding and activation in step (1) into a three-necked flask containing 100 mL of a 2mol/LLiOH solution, and stir and react at 80° C. for 5 h .

(3) washing the precipitate obtained in step (2) with deionized water 3 times, then washing with absolute ethanol 3 times, then filtering, and keeping the filter cake in a blast oven at 80° C. for 12 hours to obtain xLi ⁺ ·Al (OH) ₃ ·yH ₂ O coats the precursor of the positive electrode material.

(4) Put the precursor obtained in step (3) into a crucible, and keep the temperature at 600° C. for 10 hours to obtain a LiNi _0.333 Co _0.333 Mn _0.333 O ₂ positive electrode material coated with LiAlO ₂ .

(5) Weigh 0.48g of the above-obtained LiAlO ₂ coated and modified LiNi _0.333 Co _0.333 Mn _0.333 O ₂ positive electrode material, add 0.05g conductive carbon black as a conductive agent, 0.05g PVDF as a binder, add A small amount of NMP was ground and mixed thoroughly to form a uniform paste, which was coated on the aluminum foil substrate as a test electrode, and metal lithium was used as a counter electrode to make a button battery. The electrolyte was 1M LiPF ₆ /EC:DMC (V:V =1:1), the test charge-discharge rate is 1C.

The modified LiNi _0.333 Co _0.333 Mn _0.333 O ₂ positive electrode material prepared in this example is used to coat the LiAlO ₂ as a backup electrode and is assembled with a metal lithium sheet to form a button battery. When discharged at a constant current of 1C at room temperature, after 100 cycles The specific capacity can still be maintained at 175mAh/g, showing good cycle performance.

Example 4

(1) According to the mass percentage of LiAlO ₂ relative to the positive electrode material of 4%, respectively weigh ultrafine aluminum powder (nano-scale) with a particle size of 500 nm and 0.3Li ₂ MnO ₃ ·0.7LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode material, Add it to a steel ball mill jar with a capacity of 250mL containing agate balls, and then adjust the speed to 800p/min for grinding for 8h.

(2) Add the aluminum powder after grinding and activation in step (1) and 0.3Li ₂ MnO ₃ ·0.7LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode material mixture into a three-necked flask containing 100 mL of a 3mol/LCH ₃ COOLi solution , the reaction was stirred at 60 °C for 4 h.

(3) washing the precipitate obtained in step (2) with deionized water 3 times, then washing with absolute ethanol 3 times, then filtering, and keeping the filter cake in a blast oven at 80° C. for 12 hours to obtain xLi ⁺ ·Al (OH) ₃ ·yH ₂ O coats the precursor of the positive electrode material.

(4) The precursor obtained in step (3) was put into a crucible and kept at 800° C. for 18 hours to obtain a 0.3Li ₂ MnO ₃ ·0.7LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode material coated with LiAlO ₂ .

(5) Weigh 0.48g of the above-obtained LiAlO ₂ coated and modified 0.3Li ₂ MnO ₃ ·0.7LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode material, add 0.05g conductive carbon black as a conductive agent, 0.05g PVDF was used as a binder, a small amount of NMP was added, and a uniform paste was formed by grinding and mixing, which was coated on the aluminum foil substrate as a test electrode, and metal lithium was used as the counter electrode to make a button cell. The electrolyte was 1M LiPF ₆ / EC:DMC (V:V=1:1), the test charge and discharge rate is 1C.

The modified 0.3Li ₂ MnO ₃ ·0.7 LiNi _0.5 Co _0.2 Mn _0.3 O ₂ positive electrode material prepared in this example is used to coat the LiAlO ₂ as a backup electrode and is assembled with a metal lithium sheet to form a button battery, with a constant current of 1C at room temperature During discharge, the specific capacity can still be maintained at 255mAh/g after 100 cycles, showing good cycle performance.

Example 5

(1) According to the mass percentage of LiAlO ₂ relative to the positive electrode material of 10%, respectively weigh ultrafine aluminum powder (nano-scale) with a particle size of 300 nm and 0.5Li ₂ MnO ₃ · 0.5LiNi _0.333 Co _0.333 Mn _0.333 O ₂ positive electrode material, Add it to a steel ball mill jar with a capacity of 250mL filled with agate balls, then adjust the speed to 600p/min and grind for 5h.

(2) Add the aluminum powder after grinding and activation in step (1) and 0.5Li ₂ MnO ₃ ·0.5LiNi _0.333 Co _0.333 Mn _0.333 O ₂ positive electrode material mixture into a three-necked flask containing 100 mL of a 1mol/L LiNO ₃ solution , the reaction was stirred at 70 °C for 4 h.

(3) washing the precipitate obtained in step (2) with deionized water 3 times, then washing with absolute ethanol 3 times, then filtering, and keeping the filter cake in a blast oven at 80° C. for 12 hours to obtain xLi ⁺ ·Al (OH) ₃ ·yH ₂ O coats the precursor of the positive electrode material.

(4) The precursor obtained in step (3) was put into a crucible and kept at 400° C. for 12 hours to obtain a 0.5Li ₂ MnO ₃ ·0.5LiNi _0.333 Co _0.333 Mn _0.333 O ₂ positive electrode material coated with LiAlO ₂ .

(5) Weigh 0.48g of the above-obtained LiAlO ₂ coated and modified 0.5Li ₂ MnO ₃ ·0.5LiNi _0.333 Co _0.333 Mn _0.333 O ₂ positive electrode material, add 0.05g conductive carbon black as a conductive agent, 0.05g PVDF was used as a binder, a small amount of NMP was added, and a uniform paste was formed by grinding and mixing, which was coated on the aluminum foil substrate as a test electrode, and metal lithium was used as the counter electrode to make a button cell. The electrolyte was 1M LiPF ₆ / EC: DMC (V:V=1:1), the test charge and discharge rate is 1C.

The modified 0.5Li ₂ MnO ₃ 0.5LiNi _0.333 Co _0.333 Mn _0.333 O ₂ positive electrode material prepared in this example was used to coat the LiAlO ₂ as a backup electrode and assembled with a metal lithium sheet to form a button battery, and the constant current was 1C at room temperature. During discharge, the specific capacity can still be maintained at 268mAh/g after 100 cycles, showing good cycle performance.

Example 6

(1) Add ultrafine aluminum powder (nano-scale) with a particle size of 300 nm into a three-necked flask with a capacity of 250 mL and a concentration of 0.1 mol/L hydrochloric acid for soaking and activation treatment.

(2) Weigh the activated aluminum powder and LiNi _0.5 Mn _1.5 O ₄ positive electrode material in step (1) according to the mass percentage of 2.0% relative to the positive electrode material, respectively, and add them to three wells containing 100 mL of a 2.5 mol/LLiCl solution. In the flask, the reaction was stirred at 80 °C for 4 h.

(3) washing the precipitate obtained in step (2) with deionized water 3 times, then washing with absolute ethanol 3 times, then filtering, and keeping the filter cake in a blast oven at 80° C. for 12 hours to obtain xLi ⁺ ·Al (OH) ₃ ·yH ₂ O coats the precursor of the positive electrode material.

(4) putting the precursor obtained in step (3) into a crucible, and keeping the temperature at 600° C. for 8 hours to obtain a LiNi _0.5 Mn _1.5 O ₄ positive electrode material coated with LiAlO ₂ .

(5) Weigh 0.48g of the above-obtained LiAlO ₂ coated and modified LiNi _0.5 Mn _1.5 O ₄ positive electrode material, add 0.05g conductive carbon black as a conductive agent, 0.05g PVDF as a binder, add a small amount of NMP After grinding and fully mixing to form a uniform paste, it was coated on the aluminum foil substrate as a test electrode, and the metal lithium was used as the counter electrode to make a button battery. The electrolyte was 1M LiPF ₆ /EC:DMC (V:V=1 :1), the test charge and discharge rate is 1C.

The modified LiNi _{0.5 Mn 1.5 O 4 positive electrode material prepared in this example was used to coat the modified LiNi 0.5 Mn 1.5} O ₄ positive electrode material and assembled with metal lithium sheets to form a button battery. When discharged at a constant current of 1C at room temperature, the specific capacity after 100 cycles It can still be maintained at 139mAh/g and the voltage is maintained at 4.5V, showing good cycle performance.

Example 7

(1) Add ultrafine aluminum powder (nano-scale) with a particle size of 300 nm into a three-necked flask with a capacity of 250 mL and a concentration of 0.8 mol/L hydrochloric acid for soaking and activation treatment.

(2) Weigh the activated aluminum powder and LiNi _0.5 Mn _1.5 O ₄ positive electrode material in step (1) according to the mass percentage of 2.0% relative to the positive electrode material, respectively, and add them into a 2.5 mol/L LiCl solution containing 100 mL of the positive electrode material. In a three-necked flask, the reaction was stirred at 80 °C for 4 h.

(3) washing the precipitate obtained in step (2) with deionized water 3 times, then washing with absolute ethanol 3 times, then filtering, and keeping the filter cake in a blast oven at 80° C. for 12 hours to obtain xLi ⁺ ·Al (OH) ₃ ·yH ₂ O coats the precursor of the positive electrode material.

(4) putting the precursor obtained in step (3) into a crucible, and keeping the temperature at 600° C. for 8 hours to obtain a LiNi _0.5 Mn _1.5 O ₄ positive electrode material coated with LiAlO ₂ .

(5) Weigh 0.48g of the above-obtained LiAlO ₂ coated and modified LiNi _0.5 Mn _1.5 O ₄ positive electrode material, add 0.05g conductive carbon black as a conductive agent, 0.05g PVDF as a binder, add a small amount of NMP After grinding and fully mixing to form a uniform paste, it was coated on the aluminum foil substrate as a test electrode, and the metal lithium was used as the counter electrode to make a button battery. The electrolyte was 1M LiPF ₆ /EC:DMC (V:V=1 :1), the test charge and discharge rate is 1C.

The modified LiNi _{0.5 Mn 1.5 O 4 positive electrode material prepared in this example was used to coat the modified LiNi 0.5 Mn 1.5} O ₄ positive electrode material and assembled with metal lithium sheets to form a button battery. When discharged at a constant current of 1C at room temperature, the specific capacity after 100 cycles It can still be maintained at 139mAh/g and the voltage is maintained at 4.5V, showing good cycle performance.

Claims (6)

1. A preparation method of a fast ion conductor coated modified lithium ion battery anode material is characterized by comprising the following steps: after ball milling and mixing the nano-scale aluminum powder and the anode material, stirring and reacting the mixture with a lithium-containing solution at the temperature of 40-80 ℃ to obtain an aluminum hydroxide colloid-coated anode material precursor; calcining the precursor of the aluminum hydroxide colloid-coated positive electrode material at the temperature of 500-900 ℃ to obtain the aluminum hydroxide colloid-coated positive electrode material;

the nano-scale aluminum powder is subjected to pre-activation treatment by an acid corrosion method;

the acid corrosion method is to perform soaking treatment by hydrochloric acid, sulfuric acid or nitric acid with the concentration of 0.1-1.0 mol/L;

the ball milling is realized by a planetary ball mill or a roller ball mill, the rotating speed of the ball mill is 400-800 p/min, and the ball milling time is 1-8 h.

2. The preparation method of the fast ion conductor coated modified lithium ion battery positive electrode material according to claim 1, characterized in that: the mass of the nano-scale aluminum powder is 0.5-10.0% of that of the anode material.

3. The preparation method of the fast ion conductor coated modified lithium ion battery positive electrode material according to claim 1 or 2, characterized in that: the anode material is as follows: LiM having spinel structure₂O₄LiMO having a layered structure₂Lithium-rich manganese cathode material xLi₂MnO₃·(1-x)LiMO₂At least one of:

wherein,

LiM having spinel structure₂O₄Wherein M is at least one of Ni and Mn;

LiMO having a layered structure₂Wherein M is at least one of Ni, Co, and Mn;

lithium-manganese-rich cathode material xLi₂MnO₃·(1-x)LiMO₂Middle, 0.1<x<0.9, M ═ at least one of Ni, Co, and Mn.

4. The preparation method of the fast ion conductor coated modified lithium ion battery positive electrode material according to claim 1, characterized in that: the concentration of the lithium-containing solution is between 0.1mol/L and 10 mol/L.

5. The preparation method of the fast ion conductor coated modified lithium ion battery positive electrode material according to claim 4, characterized in that: the lithium-containing solution comprises LiCl and LiNO₃、LiOH、Li₂CO₃、CH₃At least one lithium salt of COOLi.

6. The preparation method of the fast ion conductor coated modified lithium ion battery positive electrode material according to any one of claims 1, 2, 4 and 5, characterized in that: the calcination time is 5-20 h.