Lithium ion battery cathode material, preparation method and application thereof

Abstract

The application belongs to the technical field of lithium ion battery electrode materials, and discloses a lithium ion battery positive electrode material and a preparation method and application thereof. Nickel salt, cobalt salt, manganese salt and water are added into a complexing agent and a precipitating agent to co-precipitate under alkaline conditions to obtain an NCM precursor, which is ball milled with metal powder, reacted with water, and calcined to obtain a metal oxide coated precursor; then the metal oxide coated precursor is dispersed with carbon nanotubes and anhydrous ethanol, hydrothermally reacted with a lithium source and water, and calcined under a protective atmosphere to obtain the lithium ion battery positive electrode material. The metal oxide coating layer can effectively isolate the NCM core from the electrolyte, prevent the active ingredients from escaping, stabilize the surface structure of the NCM, reduce the surface phase change in the charging and discharging process, and prolong the cycle life of the battery. The outer carbon nanotube layer and the metal oxide layer form a three-dimensional conductive network, significantly reduce the electron transport resistance, and improve the rate performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery electrode materials technology, and in particular to a lithium-ion battery cathode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries, due to their high energy density, long cycle life, and lack of memory effect, have become the core energy storage device in the current new energy field. The cathode material, as a core component of lithium-ion batteries, directly determines the battery's energy density, cycle stability, and safety. Nickel-cobalt-manganese ternary materials (NCMs), with their high specific capacity and excellent electrochemical performance, have become one of the most widely used commercial cathode materials, especially high-nickel NCM materials, which are a key direction for achieving high-energy-density batteries.

[0003] However, NCM cathode materials still have significant drawbacks during long-term charge-discharge cycles: on the one hand, their high surface activity makes them prone to side reactions with the electrolyte, leading to the release of active components (nickel, cobalt, and manganese ions), which not only reduces battery capacity but also generates an unstable interfacial film, increasing the battery's internal resistance; on the other hand, traditional NCM materials have poor electronic conductivity, resulting in greater resistance to lithium-ion transport during charge and discharge, which affects the battery's rate performance.

[0004] Existing technologies often employ a single coating layer to modify NCM, but the effects are limited: while a single metal oxide coating can isolate the electrolyte to some extent, it suffers from poor conductivity, hindering electron transport; while a single carbon material coating can improve conductivity, the coating layer lacks density and cannot effectively prevent the extraction of active components. Therefore, developing a modification scheme for NCM cathode materials that combines excellent interfacial stability and high conductivity to address the aforementioned technical pain points is of great significance for promoting the performance upgrade of lithium-ion batteries and is currently a key research focus for those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a lithium-ion battery cathode material, its preparation method, and its application, thereby solving the aforementioned problems existing in current lithium-ion battery cathode materials.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a lithium-ion battery cathode material, comprising the following steps: Nickel salt, cobalt salt, manganese salt, and water are mixed, and then a complexing agent and a precipitating agent are added. The mixture is then subjected to a co-precipitation reaction under alkaline conditions to obtain the NCM precursor. The NCM precursor was ball-milled with metal powder, and then water was added to react and obtain a metal hydroxide-coated precursor. The metal hydroxide-coated precursor was then subjected to a first calcination to obtain a metal oxide-coated precursor. A precursor coated with metal oxide, carbon nanotubes, and anhydrous ethanol are ultrasonically dispersed to obtain a precursor coated with carbon nanotubes. The precursor coated with carbon nanotubes, lithium source, and water are mixed and subjected to a hydrothermal reaction. Then, a second calcination is carried out under a protective atmosphere to obtain a lithium-ion battery cathode material.

[0007] Preferably, the molar ratio of the nickel salt, cobalt salt, and manganese salt is 1:1:1, 5:3:2, or 8:1:1; the mass of the complexing agent is 1-5% of the total mass of the nickel salt, cobalt salt, and manganese salt; and the pH of the alkaline condition is 10-11.

[0008] Preferably, the temperature of the coprecipitation reaction is 40~70℃; and the time of the coprecipitation reaction is 6~9h.

[0009] Preferably, the metal powder is magnesium powder or aluminum powder; the mass of the metal powder is 0.5-2% of the mass of the NCM precursor; the ball milling speed is 300-500 rpm; and the ball milling time is 2-4 hours.

[0010] Preferably, the reaction temperature is 50~70℃; the reaction time is 1~3h; the first calcination temperature is 400~600℃; and the first calcination time is 3~6h.

[0011] Preferably, the mass of the carbon nanotubes is 1 to 5% of the mass of the metal oxide-coated precursor; the molar ratio of the lithium source to the total molar ratio of the nickel salt, cobalt salt, and manganese salt is 1.05 to 1.1:1.

[0012] Preferably, the temperature of the hydrothermal reaction is 180~230℃; and the time of the hydrothermal reaction is 2~8h.

[0013] Preferably, the second calcination temperature is 700~900℃; the second calcination time is 5~8h.

[0014] The present invention also provides a method for preparing a lithium-ion battery cathode material, which yields a lithium-ion battery cathode material.

[0015] The present invention also provides an application of a lithium-ion battery cathode material in lithium-ion batteries.

[0016] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: (1) Significantly improved interface stability: The dense metal oxide (MgO or Al2O3) coating layer can effectively isolate the NCM core from the electrolyte, prevent the active ingredients from being released, suppress the occurrence of side reactions, stabilize the NCM surface structure, reduce surface phase transitions during charging and discharging, and extend the battery cycle life.

[0017] (2) Significantly improved conductivity: The outer carbon nanotube layer and the middle metal oxide layer form a three-dimensional conductive network. The high conductivity of carbon nanotubes can make up for the poor conductivity of metal oxides, significantly reduce electron transport resistance, and improve the rate performance of the battery.

[0018] (3) The preparation method is simple and controllable: the entire preparation process does not require complex equipment, the steps are clear, and the ball milling, calcination, hydrothermal and other processes are all mature industrial processes. The raw materials are readily available and the cost is controllable, which can realize large-scale mass production.

[0019] (4) Wide range of applications: This cathode material has high specific capacity, long cycle life and excellent rate performance, and can be adapted to different types of lithium-ion batteries to meet the diverse needs of new energy vehicles, energy storage systems and other fields. Detailed Implementation

[0020] This invention provides a method for preparing a lithium-ion battery cathode material, comprising the following steps: Nickel salt, cobalt salt, manganese salt, and water are mixed, and then a complexing agent and a precipitating agent are added. The mixture is then subjected to a co-precipitation reaction under alkaline conditions to obtain the NCM precursor. The NCM precursor was ball-milled with metal powder, and then water was added to react and obtain a metal hydroxide-coated precursor. The metal hydroxide-coated precursor was then subjected to a first calcination to obtain a metal oxide-coated precursor. A precursor coated with metal oxide, carbon nanotubes, and anhydrous ethanol are ultrasonically dispersed to obtain a precursor coated with carbon nanotubes. The precursor coated with carbon nanotubes, lithium source, and water are mixed and subjected to a hydrothermal reaction. Then, a second calcination is carried out under a protective atmosphere to obtain a lithium-ion battery cathode material.

[0021] In this invention, the nickel salt is preferably one of nickel nitrate, nickel chloride, and nickel sulfate, and more preferably nickel sulfate; the cobalt salt is preferably one of cobalt nitrate, cobalt chloride, and cobalt sulfate, and more preferably cobalt sulfate; the manganese salt is preferably one of manganese nitrate, manganese chloride, and manganese sulfate, and more preferably manganese sulfate.

[0022] In this invention, the complexing agent is preferably one of succinic acid, malonic acid, and malic acid, and more preferably succinic acid; the precipitant is preferably ammonia.

[0023] In this invention, the molar ratio of the nickel salt, cobalt salt, and manganese salt is preferably 1:1:1, 5:3:2, or 8:1:1, and more preferably 1:1:1.

[0024] In this invention, the mass of the complexing agent is preferably 1 to 5% of the total mass of nickel salt, cobalt salt, and manganese salt, and more preferably 2%.

[0025] In this invention, the pH of the alkaline condition is preferably 10-11, and more preferably 11.

[0026] In this invention, the temperature of the coprecipitation reaction is preferably 40~70℃, more preferably 50℃; the time of the coprecipitation reaction is preferably 6~9h, more preferably 8h.

[0027] In this invention, the metal powder is preferably magnesium powder or aluminum powder, more preferably magnesium powder; the particle size of the metal powder is preferably 0.5~10μm, more preferably 5μm.

[0028] In this invention, the mass of the metal powder is preferably 0.5 to 2% of the mass of the NCM precursor, and more preferably 1%.

[0029] In this invention, the ball milling speed is preferably 300~500 rpm, more preferably 400 rpm; the ball milling time is preferably 2~4 hours, more preferably 3 hours.

[0030] In this invention, the reaction temperature is preferably 50~70℃, more preferably 70℃; the reaction time is preferably 1~3h, more preferably 2h.

[0031] In this invention, the temperature of the first calcination is preferably 400~600℃, more preferably 600℃; the time of the first calcination is preferably 3~6h, more preferably 4h.

[0032] In this invention, the mass of the carbon nanotube is preferably 1 to 5% of the mass of the metal oxide-coated precursor, and more preferably 3%.

[0033] In this invention, the carbon nanotubes are preferably carboxylated multi-arm carbon nanotubes, derived from XFM30 of Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0034] In this invention, the ultrasonic dispersion time is preferably 30-60 min, and more preferably 45 min.

[0035] In this invention, the ultrasonic dispersion process further includes evaporation to remove anhydrous ethanol.

[0036] In this invention, the ratio of the molar amount of the lithium source to the total molar amount of the nickel salt, cobalt salt, and manganese salt is preferably 1.05 to 1.1:1, and more preferably 1.08:1.

[0037] In this invention, the lithium source is preferably one of lithium chloride, lithium nitrate, and lithium hydroxide, and more preferably lithium nitrate.

[0038] In this invention, the temperature of the hydrothermal reaction is preferably 180~230℃, more preferably 200℃; the time of the hydrothermal reaction is preferably 2~8h, more preferably 6h.

[0039] In this invention, the second calcination temperature is preferably 700~900℃, more preferably 850℃; the second calcination time is preferably 5~8h, more preferably 5h; and the protective atmosphere is preferably argon.

[0040] The present invention also provides a method for preparing a lithium-ion battery cathode material, which yields a lithium-ion battery cathode material.

[0041] The present invention also provides an application of a lithium-ion battery cathode material in lithium-ion batteries.

[0042] In this invention, the lithium-ion battery cathode material adopts a three-layer composite structure of core-intermediate coating layer-outer coating layer, as detailed below: (1) Core: The core active component is nickel-cobalt-manganese ternary material (NCM), which serves as the core carrier for lithium-ion insertion / deintercalation during battery charging and discharging, providing a basis for high specific capacity.

[0043] (2) Intermediate coating layer: A dense metal oxide layer covering the outer layer of the NCM core. The metal oxide is selected as magnesium oxide (MgO) or aluminum oxide (Al2O3). This dense layer can form a physical isolation barrier, effectively preventing the active components of the NCM core from contacting the electrolyte, avoiding the release of active components and the occurrence of side reactions. At the same time, it stabilizes the NCM surface structure, inhibits the surface phase transition during charging and discharging, and improves the cycle stability of the material.

[0044] (3) Outer coating layer: Carbon nanotube (CNT) layer coated on the outside of the metal oxide layer. Multi-walled carbon nanotubes (MWCNTs) are selected, which have excellent intrinsic conductivity and high aspect ratio. They can construct a three-dimensional conductive network and form a conductive path with the middle metal oxide layer, significantly reducing electron transport resistance and improving the conductivity and rate performance of the material. In addition, the carbon nanotube layer can also buffer the volume strain during the NCM charging and discharging process, avoid particle cracking, and further improve the stability of the material.

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Example 1

[0047] (1) Take nickel sulfate, cobalt sulfate and manganese sulfate according to the molar ratio of Ni:Co:Mn=1:1:1, add water to prepare a mixed salt solution with a concentration of 1.8 mol / L; add succinic acid (2% of the total mass of nickel sulfate, cobalt sulfate and manganese sulfate) to the mixed salt solution, stir evenly, slowly add precipitant (5.0 mol / L ammonia water) to make the pH of the system 11, and carry out coprecipitation reaction at 50℃ and pH=11 for 8 h. Wash and dry the product to obtain NCM precursor.

[0048] (2) The NCM precursor and magnesium powder (particle size 2000 mesh, added at 1% of the mass of NCM precursor) were placed in a ball mill, anhydrous ethanol was used as the dispersant, the ball-to-particle ratio was 15:1, the speed was 400 rpm, and the mixture was ball-milled for 3 h to obtain a uniform mixed powder. The mixed powder was added to deionized water at 5 g / L and stirred at 70 °C for 2 h. After filtration and drying, the mixture was placed in a muffle furnace and heated to 600 °C at a heating rate of 3 °C / min under air atmosphere for 4 h. Then it was cooled to room temperature to obtain MgO coated precursor.

[0049] (3) Take carbon nanotubes (3% of the mass of MgO-coated precursor), anhydrous ethanol (the ratio of anhydrous ethanol to MgO-coated precursor is 100 mL: 1 g) and mix with MgO-coated precursor. Disperse by ultrasonication for 45 min and then heat to evaporate the anhydrous ethanol to obtain carbon nanotube-coated precursor. Mix carbon nanotube-coated precursor with lithium nitrate and deionized water (the total molar ratio of lithium nitrate to Ni, Co, and Mn is 1.08:1, and the ratio of lithium nitrate to deionized water is 1 mol: 1 L), transfer to a hydrothermal reactor, and hydrothermally react at 200 °C for 6 h. After filtration and drying, place in a tube furnace, and under argon protection, heat to 850 °C at a heating rate of 3 °C / min and calcine for 5 h. After cooling, crush and sieve to obtain lithium-ion battery cathode material.

[0050] Battery Assembly and Testing: The positive electrode material was mixed with acetylene black and PVDF at a mass ratio of 85:7:8, and NMP was added to prepare a positive electrode slurry. This slurry was coated onto aluminum foil, dried, and rolled to form a positive electrode sheet. The slurry was then assembled with a graphite negative electrode, a polyolefin separator, and a lithium hexafluorophosphate-carbonate electrolyte to form a lithium-ion battery, which was tested at room temperature. Test Results: The initial discharge specific capacity at 1C was 186.3 mAh / g, the capacity retention rate after 100 cycles at 1C was 95.4%, and the capacity retention rate at a high rate of 10C was 53.6%.

[0051] Example 2

[0052] (1) Take nickel nitrate, cobalt nitrate and manganese nitrate according to the molar ratio of Ni:Co:Mn=8:1:1, add water to prepare a mixed salt solution with a concentration of 2mol / L; add malic acid (3% of the total mass of nickel nitrate, cobalt nitrate and manganese nitrate) to the mixed salt solution, stir evenly, slowly add precipitant (5.0mol / L ammonia water) to make the pH of the system 10.5, and carry out coprecipitation reaction at 60℃ and pH=10.5 for 9h. Wash and dry the product to obtain NCM precursor.

[0053] (2) The NCM precursor and aluminum powder (particle size 5 μm, added at 0.5% of the mass of the NCM precursor) were placed in a ball mill, anhydrous ethanol was used as the dispersant, the ball-to-particle ratio was 15:1, the speed was 300 rpm, and the mixture was ball-milled for 4 h to obtain a uniform mixed powder. The mixed powder was added to deionized water at 5 g / L and stirred at 60 °C for 3 h. After filtration and drying, the mixture was placed in a muffle furnace and heated to 550 °C at a heating rate of 5 °C / min under air atmosphere for 5 h. Then it was cooled to room temperature to obtain the Al2O3 coated precursor.

[0054] (3) Take carbon nanotubes (1% of the mass of Al2O3 coated precursor), anhydrous ethanol (the ratio of anhydrous ethanol to Al2O3 coated precursor is 100mL:1g) and mix with Al2O3 coated precursor. Disperse ultrasonically for 50min and then heat to evaporate the anhydrous ethanol to obtain carbon nanotube coated precursor. Mix carbon nanotube coated precursor with lithium nitrate and deionized water (the total molar ratio of lithium nitrate to Ni, Co and Mn is 1.1:1, and the ratio of lithium nitrate to deionized water is 1mol:1L). Transfer to a hydrothermal reactor and hydrothermally react at 180℃ for 5h. After filtration and drying, place in a tube furnace and calcine at a heating rate of 5℃ / min to 900℃ under argon protection for 7h. After cooling, crush and sieve to obtain lithium-ion battery cathode material.

[0055] A lithium-ion battery was assembled according to the assembly method in Example 1 and tested at room temperature. Test results: The initial discharge specific capacity at 1C was 195.9 mAh / g, the capacity retention rate after 100 cycles at 1C was 93.7%, and the capacity retention rate at a high rate of 10C was 51.8%.

[0056] Example 3

[0057] This embodiment is specifically referred to in Embodiment 1, except that the amount of magnesium powder added in step (2) is 2% of the mass of the NCM precursor, and the amount of carbon nanotubes added in step (3) is 5% of the mass of the MgO-coated precursor.

[0058] A lithium-ion battery was assembled according to the assembly method in Example 1 and tested at room temperature. Test results: The initial discharge specific capacity at 1C was 192.4 mAh / g, the capacity retention rate after 100 cycles at 1C was 97.8%, and the capacity retention rate at a high rate of 10C was 55.1%.

[0059] Comparative Example 1

[0060] For the specific comparative example, please refer to Example 1. The difference is that step (2) is not performed, that is, the metal oxide layer is not coated, and the amount of carbon nanotubes added in step (3) is 3% of the mass of the NCM precursor.

[0061] A lithium-ion battery was assembled according to the assembly method in Example 1 and tested at room temperature. Test results: The initial discharge specific capacity at 1C was 162.7 mAh / g, the capacity retention rate after 100 cycles at 1C was 78.4%, and the capacity retention rate at a high rate of 10C was 30.8%.

[0062] Comparative Example 2

[0063] For the specific comparison example, please refer to Example 1. The difference is that step (3) is not performed, that is, the carbon nanotube layer is not coated.

[0064] A lithium-ion battery was assembled according to the assembly method in Example 1 and tested at room temperature. Test results: The initial discharge specific capacity at 1C was 154.2 mAh / g, the capacity retention rate after 100 cycles at 1C was 76.8%, and the capacity retention rate at a high rate of 10C was 34.5%.

[0065] 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 a lithium-ion battery cathode material, characterized in that, Includes the following steps: Nickel salt, cobalt salt, manganese salt, and water are mixed, and then a complexing agent and a precipitating agent are added. The mixture is then subjected to a co-precipitation reaction under alkaline conditions to obtain the NCM precursor. The NCM precursor was ball-milled with metal powder, and then water was added to react and obtain a metal hydroxide-coated precursor. The metal hydroxide-coated precursor was first calcined to obtain the metal oxide-coated precursor. A carbon nanotube-coated precursor was obtained by ultrasonically dispersing a metal oxide-coated precursor, carbon nanotubes, and anhydrous ethanol. A carbon nanotube-coated precursor, a lithium source, and water are mixed and subjected to a hydrothermal reaction. Then, a second calcination is carried out under a protective atmosphere to obtain a lithium-ion battery cathode material.

2. The method for preparing a lithium-ion battery cathode material according to claim 1, characterized in that, The molar ratio of the nickel salt, cobalt salt, and manganese salt is 1:1:1, 5:3:2, or 8:1:1; the mass of the complexing agent is 1-5% of the total mass of the nickel salt, cobalt salt, and manganese salt; and the pH of the alkaline conditions is 10-11.

3. The method for preparing a lithium-ion battery cathode material according to claim 1, characterized in that, The temperature of the coprecipitation reaction is 40~70℃; the time of the coprecipitation reaction is 6~9h.

4. The method for preparing a lithium-ion battery cathode material according to claim 1, characterized in that, The metal powder is magnesium powder or aluminum powder; the mass of the metal powder is 0.5-2% of the mass of the NCM precursor; the ball milling speed is 300-500 rpm; and the ball milling time is 2-4 hours.

5. The method for preparing a lithium-ion battery cathode material according to claim 1, characterized in that, The reaction temperature is 50~70℃; the reaction time is 1~3h; the first calcination temperature is 400~600℃; the first calcination time is 3~6h.

6. The method for preparing a lithium-ion battery cathode material according to claim 1, characterized in that, The mass of the carbon nanotubes is 1 to 5% of the mass of the metal oxide-coated precursor; the molar ratio of the lithium source to the total molar ratio of nickel salt, cobalt salt, and manganese salt is 1.05 to 1.1:

1.

7. The method for preparing a lithium-ion battery cathode material according to claim 1, characterized in that, The hydrothermal reaction temperature is 180~230℃; the hydrothermal reaction time is 2~8h.

8. The method for preparing a lithium-ion battery cathode material according to claim 1, characterized in that, The second calcination temperature is 700~900℃; the second calcination time is 5~8h.

9. A lithium-ion battery cathode material prepared by the method for preparing a lithium-ion battery cathode material according to any one of claims 1 to 8.

10. The application of the lithium-ion battery cathode material according to claim 9 in lithium-ion batteries.