CN111342008A - A kind of potassium fluoride doped lithium-rich manganese-based material and preparation method and application thereof - Google Patents

Abstract

The invention discloses a potassium fluoride doped lithium-rich manganese-based material and a preparation method and application thereof. The preparation method includes the following steps: preparing a precipitant solution composed of sodium carbonate and ammonia water, preparing a transition metal salt solution, preparing a transition metal carbonate precursor by a co-precipitation method, compounding the precursor with lithium and then calcining at high temperature, and preparing a transition metal carbonate precursor by co-precipitation. In the process, potassium fluoride is added to prepare potassium fluoride-doped lithium-rich manganese-based cathode material. In the present invention, potassium fluoride is used for doping and modification of positive electrode materials of lithium ion batteries, the doping method used is simple, and the obtained potassium fluoride doped lithium-rich manganese-based material is used for positive electrode materials of lithium ion batteries, and the electrochemical performance is obviously improved , under the current density of 10C (1C=200mA g ^-1 ), it has a high specific capacity of 131.57mAh g ^-1 , and after 1500 cycles, the capacity retention rate reaches 93.37%.

Description

A kind of potassium fluoride doped lithium-rich manganese-based material and preparation method and application thereof

technical field

The invention belongs to the technical field of lithium ion battery materials, in particular to a potassium fluoride doped lithium-rich manganese-based material and a preparation method and application thereof.

Background technique

As the most conventional green high-energy battery, lithium-ion batteries are widely used in mobile phones, notebook computers and other portable devices due to their high energy density, high specific capacity, no memory effect and environmental friendliness. In recent years, with the widespread use of electric vehicles, in addition to higher requirements for the cycle performance and energy density of lithium-ion batteries, higher requirements are also placed on the cost. As one of the very important components of lithium-ion batteries, cathode materials have a profound impact on the performance, service life and cost of use of lithium-ion batteries, so the design and synthesis of lithium-ion batteries with high capacity, good rate performance, long cycle life and cheap lithium-ion batteries Cathode materials are one of the important development directions of lithium-ion batteries, and how to improve the performance of cathode materials for lithium-ion batteries has attracted extensive attention.

Li-rich manganese-based cathode materials, also known as Li-rich ternary cathode materials, have attracted great attention due to their extremely high capacity (over 250mAh g ^-1 ) and energy density (over 900Wh kg ^-1 ), and are the most One of the promising cathode materials for lithium-ion batteries. However, the disadvantages of lithium-rich manganese-based cathode materials, such as poor rate performance and cycle stability, limit their industrial application. In order to improve the electrochemical performance of Li-rich manganese-based cathode materials, many modification strategies have been studied, and the common methods mainly include element doping, surface modification, and morphological design.

Ion doping is an effective method to improve the performance of lithium ion cathode materials. In doping research, anions and cations with similar physical and chemical properties to the replaced elements are usually selected for doping. Existing ion doping includes both anion and cation doping methods. Commonly used cation doping mainly include: K ⁺ , Na ⁺ , Rb ⁺ , Mg ²⁺ , Al ³⁺ , Ti ⁴⁺ and Nb ⁵⁺ , etc. The common anion doping mainly includes: F ^- . However, the existing co-doping methods are relatively complicated and still have shortcomings. For example, the literature (Nano Energy 58 (2019) 786–796) reported that Na ⁺ and F ^- were used to co-modify lithium-rich manganese-based cathode materials, and sodium acetate was used to co-modify lithium-rich manganese-based cathode materials. As a sodium source, polyvinylidene fluoride (PVDF) is used as a fluorine source. The sources of anion and cation doping ions are different, so more raw materials are consumed, and the production process is more complicated. The prepared materials are discharged at a current density of 1C (1C=200mA g ^-1 ) The capacity is only 202mAh g ^-1 , the capacity retention rate is only 93% after 100 cycles, and the specific discharge capacity is only 130mAh g ^-1 at a high current density of 5C, which still cannot solve the problem of poor long-cycle cycle stability and poor rate performance. Shortcomings.

SUMMARY OF THE INVENTION

In order to improve the performance of lithium-rich manganese-based cathode materials and simplify the existing doping technology, the primary purpose of the present invention is to provide a potassium fluoride-doped lithium-rich manganese-based material, where the potassium ions and fluoride ions used for doping are derived from the same compound Potassium Fluoride.

Another object of the present invention is to provide a method for preparing the above-mentioned potassium fluoride-doped lithium-rich manganese-based material.

Another object of the present invention is to provide the application of the potassium fluoride-doped lithium-rich manganese-based material, and the application of the potassium fluoride-doped lithium-rich manganese-based material in the preparation of a positive electrode material for a lithium ion battery.

The present invention adopts the co-doping of potassium ion and fluorine ion which has not been reported in literature at present, while maintaining the advantages of cation and anion doping. Potassium ions are doped into the lithium layer of the material. Since the radius of potassium ions is larger than that of lithium ions, but the properties are similar to those of lithium ions, the interlayer spacing of the lithium layer is increased, which is more conducive to the back and forth of lithium ions. Good rate capability; F ion doping can replace OM (M=Ni, Co, Mn) bond by FM (M=Ni, Co, Mn) bond with stronger bond energy, which makes the structure of the material more stable and improves the material's performance. cycle performance. In order to make up for the above deficiencies, the present invention adopts potassium fluoride as the source of potassium ions and fluorine ions, which is easy to operate, does not introduce impurities, saves energy and is environmentally friendly. Under the current density of 10C and the charge-discharge voltage range of 2.5-4.6V, it has a high specific capacity of 131.57mAhg ^-1 , and the capacity retention rate reaches 93.37% after 1500 cycles.

The object of the present invention is achieved through the following technical solutions:

A preparation method of potassium fluoride doped lithium-rich manganese-based material, comprising the following steps:

(1) adding precipitating agent and ammonia water to water and configuring into a solution, stirring until completely dissolved, to obtain a precipitating agent solution;

(2) dissolving nickel salt, cobalt salt and manganese salt in water, and configuring into mixed solution to obtain transition metal salt solution;

(3) adding the precipitant solution obtained in step (1) into the transition metal salt solution described in step (2), stirring while adding, and after the precipitation reaction is complete, the transition metal carbonate precursor is obtained after filtering, washing and drying body.

(4) uniformly mixing the transition metal carbonate precursor with the lithium source and potassium fluoride, and after grinding, pre-calcining and calcining, the potassium fluoride-doped lithium-rich manganese-based material is obtained, and the potassium fluoride-doped lithium-rich manganese-based material is obtained. The heterolithium-rich manganese-based material is marked as Li _{1.2- x} K _x Ni _0.2 Co _0.08 Mn _0.52 O _2-y F _y , 0.01≤x≤0.06, 0.01≤y≤0.06.

Preferably, the concentration of the precipitant in the water in step (1) is 0.05-2 mol/L.

Preferably, the volume ratio of ammonia water to water in step (1) is 1:100-3:100.

Preferably, the concentration of the ammonia water in step (1) is 10-25%.

Preferably, in the nickel salt, cobalt salt and manganese salt in step (2), the molar ratio of Ni:Co:Mn is 0.2:0.08:0.52.

Preferably, the concentration of the nickel salt in the mixed solution in step (2) is 0.05-2 mol/L.

Preferably, the volume ratio of the precipitant solution and the transition metal salt solution in step (3) is 3:1 to 1:1.

Preferably, the addition in step (3) is dropwise addition, and the dropwise addition time is 1-3h. The dropwise addition is to make the precipitation reaction more complete. In the case of ammonia water as a complexing agent, three metal ions can be precipitated simultaneously. Sufficient reaction time is given to the precipitation so that the particles can grow with good morphology, and the morphology of the precursor directly affects the electrochemical performance of the material.

Preferably, the stirring speed in step (3) is 200-600 rpm, more preferably 400 rpm; the reaction time of the precipitation reaction is 12-15 h.

Preferably, the ratio of the molar amount of Ni in the transition metal carbonate precursor in step (4) to the molar amount of Li in the lithium source is 0.2:1.14-1.19.

Preferably, the ratio of the molar amount of Ni in the transition metal carbonate precursor described in step (4) to the molar amount of K in the potassium fluoride is 0.2:0.01-0.06.

Preferably, the method of pre-calcination and calcination in step (4) is as follows: the temperature is raised to 400-600° C. at a heating rate of 3-5° C./min, and pre-calcined for 4-6 hours; The temperature is raised to 800-950 °C at a heating rate of min, and calcined at a high temperature for 10-20 h; more preferably, the temperature is raised to 450 °C at a heating rate of 5 °C/min and kept at this temperature for 5 hours, and then calcined at a temperature of 5 °C/min for 5 hours. The heating rate was increased to 900°C and calcined for 15h.

Preferably, the ratio of the molar amount of Ni in the transition metal carbonate precursor described in step (4) to the molar amount of Li in the lithium source is 0.2:1.17-1.19.

Preferably, the ratio of the molar amount of Ni in the transition metal carbonate precursor described in step (4) to the molar amount of K in the potassium fluoride is 0.2:0.01-0.03.

Preferably, the precipitating agent in step (1) is one or more of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide, more preferably sodium carbonate.

Preferably, the nickel salt in step (2) is one or more of nickel sulfate, nickel acetate and nickel nitrate, more preferably nickel acetate.

Preferably, the cobalt salt in step (2) is one or more of cobalt sulfate, cobalt acetate, cobalt nitrate and cobalt chloride, more preferably cobalt acetate.

Preferably, the manganese salt in step (2) is one or more of manganese sulfate, manganese acetate and manganese nitrate.

Preferably, the lithium source in step (4) is one or both of lithium carbonate and lithium hydroxide, more preferably lithium carbonate.

The potassium fluoride-doped lithium-rich manganese-based material prepared by the method for preparing a potassium fluoride-doped lithium-rich manganese-based material is obtained.

Application of the above potassium fluoride doped lithium-rich manganese-based material in the preparation of a positive electrode material for a lithium ion battery.

Preferably, the application of the potassium fluoride-doped lithium-rich manganese-based material in the preparation of a positive electrode material for lithium ion batteries includes the following steps: mixing the potassium fluoride-doped lithium-rich manganese-based material, acetylene black and PVDF to prepare The slurry is then coated on the aluminum foil to obtain the positive electrode of the lithium ion battery.

More preferably, it includes the following steps: mixing and slurrying potassium fluoride doped lithium-rich manganese-based positive electrode material, acetylene black and PVDF in a mass ratio of 80:10:10, and then coating on aluminum foil to obtain lithium ions positive battery.

Further preferably, the application includes the following steps: weighing 0.2 g of potassium fluoride doped lithium-rich manganese-based positive electrode material, 0.025 g of PVDF, and 0.025 g of acetylene black, uniformly mixing and grinding, and then transferring it into a small glass bottle, adding 1 mL of NMP. , magnetic stirring for 1 h, the material was coated on aluminum foil to make electrodes, and metal lithium was used as the counter electrode to assemble a CR2016 button battery in a glove box.

Compared with the existing doping technology, the present invention has the following advantages and beneficial effects:

(1) The present invention adopts a simple co-precipitation method to prepare the carbonate precursor. In the process of preparing lithium, potassium fluoride is used to co-dope potassium ions and fluorine ions in one step. The preparation process is simple and feasible, and the two kinds of ion doping share one source, without introducing other impurities, successfully synthesized potassium fluoride doped lithium-rich manganese-based cathode material Li _1.2-x K _x Ni _0.2 Co _0.08 Mn _0.52 O _2-y F _y (0.01≤x≤0.06, 0.01≤y ≤0.06) and applied to the positive electrode of lithium ion battery.

(2) the present invention adopts potassium fluoride as raw material to realize the co-doping of potassium ions and fluorine ions, and the lithium layer of the material is doped with potassium ions, because the radius of potassium ions is larger than that of lithium ions, thereby increasing the interlayer spacing of the lithium layer , which is more conducive to the back-and-forth deintercalation of lithium ions, so that the material has good rate performance. F ion doping can replace the OM (M=Ni, Co, Mn) bond by the FM (M=Ni, Co, Mn) bond with stronger bond energy, which makes the structure of the material more stable and improves the cycle stability of the material. On the other hand, F is a negative one, and oxygen is a negative two. In order to maintain the electrical neutrality of the material, some metal ions are reduced (usually Ni ³⁺ is reduced to Ni ^{2 +} ). Since Ni ²⁺ has a larger ionic radius than Ni ³⁺ , the interlayer spacing can be increased to reduce the transfer resistance of lithium ions, which also improves the rate capability of the material. Therefore, the cycle performance and rate capability of potassium fluoride doped lithium-rich manganese-based cathode materials are better than those of lithium-rich manganese-based cathode materials synthesized by potassium ion or fluoride ion doping.

(3) The raw materials used in the present invention are cheap and easy to obtain. The preparation method used in the invention has simple process and no pollution, and is suitable for large-scale industrial production.

(4) The potassium fluoride-doped lithium-rich manganese-based material prepared by the present invention has high specific capacity, excellent cycle performance and rate performance when used in the positive electrode of lithium ion battery. Li _1.2-x K _x Ni _0.2 Co _0.08 Mn _0.52 O _2-y F _y where x and y are taken as 0.01, under the current density of 10C and the charge-discharge voltage range of 2.5-4.6V, it has 131.57mAh g ^-1 High specific capacity, cycle 1500 cycles, the capacity retention rate reaches 93.37%. Such excellent electrochemical performance is an effect that cannot be achieved by simple anion and cation doping (the sources of K and F are not co-doping of the same substance). At the same time, the potassium fluoride-doped lithium-rich manganese-based positive electrode material prepared by the invention has higher specific capacity and rate performance compared with the prior invention, excellent cycle performance under large current density, and long battery life.

Description of drawings

1 is a scanning electron microscope image of a potassium fluoride-doped lithium-rich manganese-based material prepared in Example 1 of the present invention.

FIG. 2 is an element distribution test diagram of the potassium fluoride-doped lithium-rich manganese-based material prepared in Example 1 of the present invention.

3 is an X-ray diffraction pattern of the potassium fluoride-doped lithium-rich manganese-based material prepared in Example 1 of the present invention.

4 is a graph showing the period cycle performance of potassium fluoride doped lithium-rich manganese-based materials prepared in Examples 1, 2 and 3 as lithium ion cathode materials at a current density of 1000 mA g ⁻¹ .

FIG. 5 is a long-cycle cycle performance diagram of the potassium fluoride-doped lithium-rich manganese-based material prepared in Example 1 of the present invention as a lithium ion positive electrode material at a current density of 2000 mA g ⁻¹ .

6 is a graph of the rate performance measured under different current densities of the potassium fluoride-doped lithium-rich manganese-based material prepared in Example 1 of the present invention as a lithium ion positive electrode material.

Detailed ways

The following describes the technical solutions of the present invention in further detail with reference to the embodiments of the present invention and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example 1

A method for preparing a potassium fluoride doped lithium-rich manganese-based material is based on a lithium-rich manganese-based positive electrode material as a matrix, potassium element is used to replace lithium element, fluorine element is used to replace oxygen element, and the replacement ratios of potassium element and oxygen element are both 1%.

A preparation method of potassium fluoride doped lithium-rich manganese-based material, comprising the following steps:

Weigh 10.1750g of sodium carbonate and 3mL of 25wt% concentrated ammonia water and add it to 100mL of deionized water to configure a solution, stir until completely dissolved to obtain a precipitant solution; weigh 4.9772g of nickel acetate, 1.9928g of cobalt acetate and 12.7447g of manganese acetate in turn Dissolved in 100 mL of deionized water to form a transition metal salt solution, the precipitant solution was added dropwise to the transition metal salt solution with continuous stirring, and the dropwise addition was completed within 3 hours. The stirring speed was 400 rpm, and the reaction was performed for 15 hours. The obtained solution was filtered and washed , dried to obtain the transition metal carbonate precursor, and then weighed 2g of the transition metal carbonate precursor, 0.9924g of lithium carbonate and 0.0101g of potassium fluoride, mixed together, ground, and then heated at a rate of 5°C/min at 450 After pre-sintering at ℃ for 5 hours, the temperature was increased to 900 ℃ for 15 hours at a heating rate of 5 ℃/min, to obtain the potassium fluoride doped lithium-rich manganese-based material.

Battery assembly: Weigh 0.2 g of potassium fluoride doped lithium-rich manganese-based material, 0.025 g of PVDF, and 0.025 g of acetylene black prepared in this example, put them in a mortar and evenly mix and grind, and then transfer them into a small glass bottle. Add 1 mL of NMP, stir magnetically for 1 h, coat the material on aluminum foil to make an electrode, use metal lithium as the counter electrode to assemble a CR2016 button battery in a glove box, and conduct electrochemical performance tests.

Example 2

A method for preparing a potassium fluoride doped lithium-rich manganese-based material is based on a lithium-rich manganese-based positive electrode material as a matrix, potassium element is used to replace lithium element, fluorine element is used to replace oxygen element, and the replacement ratios of potassium element and oxygen element are both 2%.

A preparation method of potassium fluoride doped lithium-rich manganese-based material, comprising the following steps:

Weigh 10.1750g of sodium carbonate and 3mL of 25wt% concentrated ammonia water and add it to 100mL of deionized water to configure a solution, stir until completely dissolved to obtain a precipitant solution; weigh 4.9772g of nickel acetate, 1.9928g of cobalt acetate and 12.7447g of manganese acetate in turn Dissolved in 100 mL of deionized water to form a transition metal salt solution, the precipitant solution was added dropwise to the transition metal salt solution with continuous stirring, and the dropwise addition was completed within 3 hours. The stirring speed was 400 rpm, and the reaction was performed for 15 hours. The obtained solution was filtered and washed , dried to obtain the transition metal carbonate precursor, and then weighed 2g of the transition metal carbonate precursor, 0.9841g of lithium carbonate and 0.0202g of potassium fluoride, mixed together, ground, and then heated at a rate of 5°C/min at 450 After pre-sintering at ℃ for 5 hours, the temperature was increased to 900 ℃ for 15 hours at a heating rate of 5 ℃/min, to obtain the potassium fluoride doped lithium-rich manganese-based material.

Battery assembly: Weigh 0.2 g of potassium fluoride doped lithium-rich manganese-based material, 0.025 g of PVDF, and 0.025 g of acetylene black prepared in this example, put them in a mortar and evenly mix and grind, and then transfer them into a small glass bottle. Add 1 mL of NMP, stir magnetically for 1 h, coat the material on aluminum foil to make an electrode, use metal lithium as the counter electrode to assemble a CR2016 button battery in a glove box, and conduct electrochemical performance tests.

Example 3

A method for preparing a potassium fluoride doped lithium-rich manganese-based material is based on a lithium-rich manganese-based positive electrode material as a matrix, potassium element is used to replace lithium element, fluorine element is used to replace oxygen element, and the replacement ratios of potassium element and oxygen element are both 3%.

A preparation method of potassium fluoride doped lithium-rich manganese-based material, comprising the following steps:

Weigh 10.1750g of sodium carbonate and 3mL of 25wt% concentrated ammonia water and add it to 100mL of deionized water to configure a solution, stir until completely dissolved to obtain a precipitant solution; weigh 4.9772g of nickel acetate, 1.9928g of cobalt acetate and 12.7447g of manganese acetate in turn Dissolved in 100 mL of deionized water to form a transition metal salt solution, the precipitant solution was added dropwise to the transition metal salt solution with continuous stirring, and the dropwise addition was completed within 3 hours. The stirring speed was 400 rpm, and the reaction was performed for 15 hours. The obtained solution was filtered and washed , dried to obtain the transition metal carbonate precursor, and then weighed 2g of the transition metal carbonate precursor, 0.9758g of lithium carbonate and 0.0303g of potassium fluoride, mixed together, ground, and then heated at a rate of 5°C/min. After pre-sintering at 450°C for 5 hours, the temperature was raised to 900°C for 15 hours at a heating rate of 5°C/min to obtain the potassium fluoride doped lithium-rich manganese-based material.

Battery assembly: Weigh 0.2 g of potassium fluoride doped lithium-rich manganese-based material, 0.025 g of PVDF, and 0.025 g of acetylene black prepared in this example, put them in a mortar and evenly mix and grind, and then transfer them into a small glass bottle. Add 1 mL of NMP, stir magnetically for 1 h, coat the material on aluminum foil to make an electrode, use metal lithium as the counter electrode to assemble a CR2016 button battery in a glove box, and conduct electrochemical performance tests.

Performance Testing:

About the test of the potassium fluoride doped lithium-rich manganese-based material prepared in Example 1:

1. Scanning electron microscope (SEM) test was carried out on the potassium fluoride-doped lithium-rich manganese-based material prepared in the above-mentioned embodiment 1, and the results are shown in Figure 1; The material is subjected to scanning element distribution test, and the result is shown in Figure 2; the potassium fluoride-doped lithium-rich manganese-based material prepared in Example 1 is subjected to XRD test, and the result is shown in Figure 3.

It can be seen from FIG. 1 that the material particles prepared in Example 1 have a polyhedral shape, the crystal form of the material is perfect, and the particle size distribution range is between 0.3 and 1 μm. It can be seen from Figure 2 that K and F are uniformly distributed in the material, and the doping of potassium fluoride into the Li-rich manganese-based material is successfully achieved. It can be seen from Figure 3 that the main peak of the sample belongs to the typical ɑ-NaFeO ₂ structure, and some weaker peaks between 20 and 23° belong to the C2/m space group, which are characteristic peaks of the Li ₂ MnO ₃ component. The characteristic peaks originate from the ordered arrangement of Li ⁺ and Mn ⁴⁺ in the transition metal layer in the material. The two groups of peaks located in the 37.5-39.5° range and the 63-67° range are obviously split, indicating that the samples have a good ɑ-NaFeO ₂ layered structure.

2. Carry out rate performance and cycle performance tests on the potassium fluoride doped lithium-rich manganese-based material prepared in Example 1. After the battery prepared in Example 1 was put on hold for 12 hours, the battery tester (Shenzhen Xinwei) was used to test the battery charge and discharge, cycle performance and rate performance. The test temperature was room temperature, and the current density was 100mA g ^-1 ~ 2000mA g ^-1 In this case, the voltage range of constant current charge and discharge is 2.5 to 4.6V. The test results of Example 1 are shown in Figures 4-6.

It can be seen from Figure 4 that when the potassium fluoride-doped lithium-rich manganese-based material prepared in Example 1 is used in a lithium-ion battery, the first discharge specific capacity is 136.1mAh g ^-1 at a current density of 1000mA g ^-1 (5C). , has a high specific capacity of 154.2mAh g ^-1 , and after 200 cycles, the specific capacity is still 130.3mAh g ^-1 , and the capacity retention rate reaches 95.8%. It can be seen from Fig. 5 that the potassium fluoride-doped lithium-rich manganese-based material prepared in Example 1 has high specific capacity and excellent cycle performance in lithium-ion batteries, and the current density is 2000mA g ^-1 (10C). The first discharge specific capacity is 100.57mAh g ^-1 , with a high specific capacity of 131.57mAhg ^-1 , and after 1500 cycles, the specific capacity is still 93.9mAh g ^-1 , and the capacity retention rate reaches 93.37%. Figure 6 shows the rate performance tested at different rates of 0.1C (1C=200mA g ^-1 ), 0.5C, 1C, 2C, 5C, and 10C. It can be seen that the rate performance is very good.

About the test of potassium fluoride doped lithium-rich manganese-based material prepared in Example 2:

The cycle performance test of the potassium fluoride-doped lithium-rich manganese-based material prepared in Example 2 was carried out. When the current density is 1000 mA g ^-1 , the operation or testing method is the same as that of Example 1. The test results of Example 2 are shown in FIG. 4 .

It can be seen from Figure 4 that when the potassium fluoride-doped lithium-rich manganese-based material prepared in Example 2 is used in a lithium-ion battery, the first discharge specific capacity is 128.1mAh g ^-1 at a current density of 1000mA g ^-1 (5C). , has a high specific capacity of 135.9mAh g ^-1 , and after 200 cycles, the specific capacity is still 117.8mAh g ^-1 , and the capacity retention rate reaches 91.9%.

About the test of potassium fluoride doped lithium-rich manganese-based material prepared in Example 3:

The cycle performance test of the potassium fluoride-doped lithium-rich manganese-based material prepared in Example 3 was carried out. When the current density is 1000 mA g ^-1 , the operation or testing method is the same as that of Example 1. The test results of Example 3 are shown in FIG. 4 .

It can be seen from Figure 4 that when the potassium fluoride-doped lithium-rich manganese-based material prepared in Example 3 is used in a lithium-ion battery, the first discharge specific capacity is 124.4mAh g ^-1 at a current density of 1000mA g ^-1 (5C). , has a high specific capacity of 128.9mAh g ^-1 , and after 200 cycles, the specific capacity is still 96.1mAh g ^-1 , and the capacity retention rate reaches 77.3%.

Table 1 shows the comparison results of the specific capacity and cycle performance of the battery when the potassium fluoride-doped lithium-rich manganese-based material prepared in Example 1 of the present invention and the material reported in the literature are used as the positive electrode material of the lithium ion battery. It can be drawn from Table 1: the potassium fluoride doped lithium-rich manganese-based cathode material prepared by the present invention has higher specific capacity and rate performance compared with the existing invention, excellent cycle performance under large current density, and long battery life .

Table 1 Comparison of specific capacity and cycle performance between the present invention and literature reports (1C=200mA g ^-1 )

Note: References

[1] Nano Energy 58 (2019) 786–796.

[2][2] Solid State Ionics 332 (2019) 47–54.

[3] J.Phys.Chem.C 2018, 122, 27836-27842.

The embodiment is the preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principle of the present invention. , all should be equivalent replacement modes, and all are included in the protection scope of the present invention.

Claims (10)

1. A preparation method of a potassium fluoride doped lithium-rich manganese-based material is characterized by comprising the following steps:

(1) adding a precipitant and ammonia water into water to prepare a solution, and stirring until the precipitant and the ammonia water are completely dissolved to obtain a precipitant solution;

(2) dissolving nickel salt, cobalt salt and manganese salt in water to prepare a mixed solution, thereby obtaining a transition metal salt solution;

(3) adding the precipitant solution obtained in the step (1) into the transition metal salt solution obtained in the step (2), stirring while adding, and filtering, washing and drying after complete precipitation reaction to obtain a transition metal carbonate precursor;

(4) uniformly mixing a transition metal carbonate precursor with a lithium source and potassium fluoride, grinding, pre-calcining and calcining to obtain the potassium fluoride doped lithium-rich manganese-based material, wherein the label of the potassium fluoride doped lithium-rich manganese-based material is Li_{1.2- x}K_xNi_0.2Co_0.08Mn_0.52O_2-yF_y，0.01≤x≤0.06，0.01≤y≤0.06。

2. The method for preparing the potassium fluoride-doped lithium-rich manganese-based material according to claim 1, wherein the ratio of the molar amount of Ni in the transition metal carbonate precursor in the step (4) to the molar amount of Li in the lithium source is 0.2: 1.14-1.19; the molar weight ratio of Ni in the transition metal carbonate precursor to K in the potassium fluoride in the step (4) is 0.2: 0.01-0.06.

3. The method for preparing the potassium fluoride-doped lithium-rich manganese-based material according to claim 2, wherein the ratio of the molar amount of Ni in the transition metal carbonate precursor in the step (4) to the molar amount of Li in the lithium source is 0.2: 1.17-1.19; the molar weight ratio of Ni in the transition metal carbonate precursor to K in the potassium fluoride in the step (4) is 0.2: 0.01-0.03.

4. The method for preparing the potassium fluoride-doped lithium-rich manganese-based material according to any one of claims 1 to 3, wherein in the nickel salt, the cobalt salt and the manganese salt in the step (2), the ratio of Ni: co: the molar ratio of Mn is 0.2: 0.08: 0.52; and (4) dropwise adding, wherein the dropwise adding time is 1-3 h.

5. The method for preparing the potassium fluoride-doped lithium-rich manganese-based material according to claim 4, wherein the concentration of the precipitating agent in the step (1) in water is 0.05-2 mol/L; the volume ratio of the ammonia water to the water in the step (1) is 1: 100-3: 100, respectively; the concentration of the ammonia water in the step (1) is 10-25%.

6. The method for preparing the potassium fluoride-doped lithium-rich manganese-based material according to any one of claims 1 to 3, wherein the concentration of the nickel salt in the mixed solution in the step (2) is 0.05 to 2 mol/L;

the volume ratio of the precipitant solution to the transition metal salt solution in the step (3) is 3: 1-1: 1.

7. the method for preparing the potassium fluoride-doped lithium-rich manganese-based material according to any one of claims 1 to 3, wherein the stirring speed in the step (3) is 200 to 600 rpm; the reaction time of the precipitation reaction in the step (3) is 12-15 h; the precalcination and the calcination mode in the step (4) are as follows: heating to 400-600 ℃ at a heating rate of 3-5 ℃/min, and pre-sintering for 4-6 h; then, the temperature is raised to 800-950 ℃ at the heating rate of 3-5 ℃/min, and the high-temperature calcination is carried out for 10-20 h.

8. The method for preparing the potassium fluoride-doped lithium-rich manganese-based material according to any one of claims 1 to 3, wherein the precipitating agent in the step (1) is one or more of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide;

the nickel salt in the step (2) is one or more than two of nickel sulfate, nickel acetate and nickel nitrate;

the cobalt salt in the step (2) is one or more than two of cobalt sulfate, cobalt acetate, cobalt nitrate and cobalt chloride, and is more preferably cobalt acetate;

the manganese salt in the step (2) is one or more than two of manganese sulfate, manganese acetate and manganese nitrate;

and (4) the lithium source is one or two of lithium carbonate and lithium hydroxide.

9. The potassium fluoride-doped lithium-rich manganese-based material prepared by the preparation method of the potassium fluoride-doped lithium-rich manganese-based material according to any one of claims 1 to 8.

10. The use of the potassium fluoride-doped lithium-rich manganese-based material of claim 9 in the preparation of a positive electrode material for a lithium ion battery.

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