Method for improving cycle performance of manganese-based positive electrode material, manganese-based positive electrode material prepared by the method and application

Abstract

The application discloses a method for improving cycle performance of a manganese-based positive electrode material, a manganese-based positive electrode material prepared by the method and application, and belongs to the technical field of battery preparation. The specific process of improving cycle performance of the manganese-based positive electrode material and the manganese-based positive electrode material prepared by the method is as follows: the spin state of manganese ions in the manganese-based material is reduced, and then the manganese-based positive electrode material is prepared. The combination of different treatment modes in the magnetic field assistance, calcination and plasma treatment changes the electronic energy level structure of the manganese ions, makes the electrons of different spin states re-pair, obtains a new d-orbital electron filling state, changes the spin state of the manganese ions, and the manganese-based positive electrode material with low spin state is prepared. Meanwhile, due to the magnetostriction effect, the lattice constant is reduced, and the force of the TM-O bond is beneficial to be enhanced. In the manganese-based positive electrode material with low spin state, the lattice distortion caused by the Jahn-Teller effect can be significantly reduced, the cycle stability of the material is improved, and the service life of the material is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery preparation, and particularly relates to a method for improving the cycle performance of a manganese-based cathode material, the obtained manganese-based cathode material and its application. Background Art

[0002] Due to the characteristics of relatively rich manganese resources, relatively low cost, and relatively high voltage of manganese-based materials, manganese-based cathode materials have received extensive attention. Manganese-based cathode materials include, for example, lithium manganate, spinel nickel manganese manganate, layered manganese sodium material, lithium iron manganese phosphate, and lithium-rich manganese-based materials. Among them, the lithium-rich manganese-based layered material is based on the traditional layered material, increasing the lithium content, replacing the transition metal ions in the transition metal layer with lithium to obtain a lithium-rich manganese-based layered cathode material, whose chemical formula is xLi2MnO3·(1-x)LiTMO2(0<x<1, TM = Mn, Ni, Co, etc.), and can also be written as Li 1+x TM 1-x O2. Among many lithium-ion battery cathode materials, due to the high specific capacity (250mAh·g -1 ), high working voltage (>3.5V), low cost, and environmental friendliness of the lithium-rich manganese-based layered cathode material, it is considered to be the key cathode material for building lithium-ion batteries to break through 500Wh·kg -1 . However, the following problems also exist, which hinder its commercialization process:

[0003] (1) Irreversible oxygen release

[0004] When charging to 4.8V in the first cycle, the redox process of anions is difficult to control, and some O 2- undergoes a peroxidation reaction and is oxidized to O2. Some of the O2 is trapped in the bulk phase, and the other part is irreversibly released through the surface. The anion redox reaction is a double-edged sword. On the one hand, compared with ternary materials, it provides more capacity for the material. On the other hand, O2 can only be partially reduced to O 2- during the subsequent discharge process, resulting in a lower initial Coulomb efficiency and voltage hysteresis. At the same time, long-term cycling will also promote the loss of O2 from the bulk phase and the formation of microstructural defects, accelerating voltage decay.

[0005] (2) Transition metal ion migration

[0006] When charging to 4.8V, lithium ions in the transition metal layer are deintercalated, and at the same time, anions undergo an oxidation reaction as charge compensation. At this time, transition metal ions will undergo interlayer migration and intralayer migration. Interlayer migration causes irreversible transformation of the material. Intralayer migration makes it impossible for lithium ions to return to the same chemical environment as when deintercalating when they are re-embedded inside, ultimately resulting in voltage hysteresis.

[0007] (3) Transition metal ion dissolution

[0008] Transition metal ions first dissolve from the material surface, then migrate through the electrolyte, and finally deposit on the negative electrode. The dissolution process of transition metal ions leads to capacity and voltage decay. Furthermore, the reduction / deposition of transition metals on the negative electrode increases the thickness of the solid electrolyte interphase (SEI) layer, increasing battery impedance and thus hindering lithium-ion transport.

[0009] (4) Surface side reactions

[0010] The material surface is unstable, and side reactions occur at the interface where it comes into direct contact with the electrolyte, forming a thick positive electrode electrolyte interphase (CEI) layer. An excessively thick CEI layer will hinder lithium-ion diffusion, thereby reducing electrochemical performance.

[0011] Currently, the general approach to addressing the aforementioned problems is to modify manganese-based cathode materials, with common methods including doping and coating. However, doping and coating are not only complex processes but also have significant limitations, failing to effectively solve the problems encountered in the application of manganese-based cathode materials. Therefore, a more effective processing method needs to be developed. Summary of the Invention

[0012] To address the aforementioned shortcomings in existing technologies, this invention provides a method for improving the cycle performance of manganese-based cathode materials, the resulting manganese-based cathode materials, and their applications. This invention proposes a method for preparing manganese-based cathode materials using magnetic field and / or high-temperature plasma-assisted calcination. This method neither introduces other elements nor modifies the surface of the manganese-based cathode material, thus achieving true results without sacrificing the material's ultra-high specific capacity. The electrochemical performance is improved by regulating the material's structure.

[0013] To achieve the above objectives, the technical solution adopted by the present invention to solve its technical problem is as follows:

[0014] A method for improving the cycle performance of manganese-based cathode materials involves reducing the spin state of manganese ions in the manganese-based material and then using it to prepare the cathode material.

[0015] Furthermore, the spin state of manganese ions in manganese-based materials is reduced.

[0016] Furthermore, at least two of the following methods are employed to reduce the spin state of manganese ions in manganese-based materials: calcination, magnetic field-assisted treatment, and high-temperature plasma treatment.

[0017] Furthermore, calcination in a magnetic field and / or high-temperature plasma environment reduces the spin state of manganese ions in the manganese-based material.

[0018] Furthermore, calcination includes the entire process of heating, holding, and cooling, and magnetic field and / or high-temperature plasma treatment can be carried out throughout the entire calcination process.

[0019] Furthermore, the specific process for reducing the spin state of manganese ions in manganese-based materials is as follows:

[0020] The dried manganese-containing precursor material is mixed with a lithium source and then calcined at 300–500°C for 5–10 h in a magnetic field and / or high-temperature plasma environment, followed by calcination at 800–1000°C for 10–15 h.

[0021] Furthermore, when magnetic field-assisted treatment is used to reduce the spin state of manganese ions in manganese-based materials, the magnetic field strengths during the two calcination processes are 0.2–0.5 T, respectively.

[0022] Furthermore, the magnetic field strengths for the two calcinations were 0.25–0.40 T, respectively.

[0023] Furthermore, the first calcination temperature was 500℃ and the time was 5 hours, and the second calcination temperature was 800℃ and the time was 12 hours.

[0024] Furthermore, the process of reducing the spin state of manganese ions in manganese-based materials is as follows:

[0025] Manganese-containing precursor materials are mixed with lithium sources and then treated in a plasma environment with a magnetic field strength of 0.2–0.5T to reduce the spin state of manganese ions in the manganese-based materials.

[0026] Furthermore, the ratio of the molar number of lithium elements in the lithium-containing source material to the molar number of manganese elements in the manganese-containing precursor material is 0.5:1 to 5:1.

[0027] Furthermore, the ratio of the number of moles of lithium in the lithium-containing source material to the number of moles of manganese in the manganese-containing precursor material is 1.7:1 to 3:1.

[0028] Furthermore, the manganese-containing precursor material is a carbonate precursor or a hydroxide precursor.

[0029] Furthermore, the preparation method of the carbonate precursor is as follows: manganese sulfate monohydrate and one or two of cobalt sulfate heptahydrate and nickel sulfate hexahydrate are mixed and dissolved in deionized water according to the ratio of the molar number of manganese to the sum of the molar numbers of the two transition metals nickel and cobalt being 0.5:1 to 9:1. Then, co-precipitation is carried out using Na2CO3 as a precipitant and ammonia water as a complexing agent to obtain the carbonate precursor.

[0030] Furthermore, in preparing the precursor, manganese sulfate monohydrate is mixed with one or two of cobalt sulfate heptahydrate and nickel sulfate hexahydrate, with the ratio of the molar number of manganese to the sum of the molar numbers of nickel and / or cobalt being 1:1 to 7:1.

[0031] Furthermore, when preparing the hydroxide precursor, NaOH solution is used as a precipitant and NH3·H2O solution is used as a complexing agent.

[0032] Furthermore, the lithium source is LiOH·H2O or Li2CO3.

[0033] The manganese-based cathode material prepared by the above method.

[0034] The above-mentioned manganese-based cathode materials are used as cathodes in the preparation of lithium-ion batteries, lithium metal batteries, solid-state lithium batteries, and negative electrode-free lithium batteries.

[0035] The beneficial effects of this invention are:

[0036] This invention alters the original spin state of manganese ions in manganese-based cathode materials by applying a magnetic field of a certain intensity and / or high-temperature plasma treatment during calcination, causing a change in the spin of their electrons, thereby preparing manganese-based cathode materials with low-spin manganese ions. Compared with conventional methods for controlling the spin state of manganese ions such as ligand modulation and metal doping, the method of this invention is more efficient, more stable, and the process is simple, pollution-free, and can be applied on a large scale.

[0037] This invention reduces the spin state of manganese ions by applying an external magnetic field and / or high-temperature plasma treatment. In manganese-based cathode materials with low spin state, the lattice distortion caused by the Jan Taylor effect can be significantly reduced, allowing the material to maintain a well-symmetrical regular octahedral field, thereby improving the cycle stability of the material. At the same time, due to the magnetostrictive effect, the lattice constant is reduced, which is conducive to the enhancement of the TM-O bond force and extends the battery life. Attached Figure Description

[0038] Figure 1 Spin state characterization curves for the manganese-based cathode material prepared in Comparative Example 5 and the low-spin manganese-based cathode material prepared in Example 3;

[0039] Figure 2 The 1C discharge capacity curves of the manganese-based cathode material prepared in Comparative Example 5 and the low-spin manganese-based cathode material prepared in Example 3 are shown.

[0040] Figure 3 The 1C discharge capacity curves of the manganese-based cathode material prepared in Comparative Example 5 and the low-spin manganese-based cathode material prepared in Example 12 are shown.

[0041] Figure 4 The 1C discharge capacity curves are for the manganese-based cathode material prepared in Comparative Example 5 and the low-spin manganese-based cathode material prepared in Example 15. Detailed Implementation

[0042] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0043] Example 1

[0044] A low-spin manganese-based cathode material prepared by magnetic field-assisted calcination is described below:

[0045] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor is 1:1.

[0046] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 3:1. Then, it was placed in a high-temperature annealing furnace with a magnetic field strength of 0.25T and calcined at 300℃ for 10h. After maintaining the magnetic field strength at 0.2T, the temperature was raised to 1000℃ and calcined for 10h to obtain the final product.

[0047] Example 2

[0048] A low-spin manganese-based cathode material prepared by magnetic field-assisted calcination is described below:

[0049] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor is 2:1.

[0050] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 2.26:1. Then, it was placed in a high-temperature annealing furnace with a magnetic field strength of 0.25T and calcined at 400℃ for 9h. After maintaining the magnetic field strength at 0.25T, the temperature was raised to 900℃ and calcined for 11h to obtain the final product.

[0051] Example 3

[0052] A low-spin manganese-based cathode material prepared by magnetic field-assisted calcination is described below:

[0053] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor is 3:1.

[0054] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 2:1. Then, it was placed in a high-temperature annealing furnace with a magnetic field strength of 0.30T and calcined at 500℃ for 8h. After maintaining the magnetic field strength at 0.30T, the temperature was raised to 800℃ and calcined for 12h to obtain the final product.

[0055] Example 4

[0056] A low-spin manganese-based cathode material prepared by magnetic field-assisted calcination is described below:

[0057] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and NaOH is used as a precipitant and ammonia is used as a complexing agent to coprecipitate to obtain hydroxide precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor is 4:1.

[0058] (2) After drying the hydroxide precursor at 120℃ for 12h, it was mixed with LiOH·H2O. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in LiOH·H2O, with a lithium:manganese molar ratio of 1.88:1. Then, it was placed in a high-temperature annealing furnace with a magnetic field strength of 0.35T and calcined at 500℃ for 7h. After maintaining the magnetic field strength at 0.35T, the temperature was raised to 800℃ and calcined for 12h to obtain the final product.

[0059] Example 5

[0060] A low-spin manganese-based cathode material prepared by magnetic field-assisted calcination is described below:

[0061] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and NaOH is used as a precipitant and ammonia is used as a complexing agent to coprecipitate to obtain hydroxide precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor is 5:1.

[0062] (2) After drying the hydroxide precursor at 120℃ for 12h, it was mixed with LiOH·H2O. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in LiOH·H2O, with a lithium:manganese molar ratio of 1.8:1. Then, it was placed in a high-temperature annealing furnace with a magnetic field strength of 0.40T and calcined at 500℃ for 6h. The magnetic field strength was then adjusted to 0.30T, and the temperature was raised to 800℃ and calcined for 11h to obtain the final product.

[0063] Example 6

[0064] A low-spin manganese-based cathode material prepared by magnetic field-assisted calcination is described below:

[0065] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia as complexing agent to obtain carbonate precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor is 6:1.

[0066] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 1.75:1. Then, it was placed in a high-temperature annealing furnace with a magnetic field strength of 0.40T and calcined at 500℃ for 5h. The magnetic field strength was then adjusted to 0.50T, and the temperature was raised to 800℃ and calcined for 10h to obtain the final product.

[0067] Example 7

[0068] A low-spin manganese-based cathode material prepared by magnetic field-assisted calcination is described below:

[0069] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 7:1.

[0070] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 1.70:1. Then, it was placed in a high-temperature annealing furnace with a magnetic field strength of 0.40T and calcined at 500℃ for 5h. The magnetic field strength was then adjusted to 0.40T, and the temperature was raised to 800℃ and calcined for 10h to obtain the final product.

[0071] Example 8

[0072] A low-spin manganese-based cathode material prepared by magnetic field-assisted calcination is described below:

[0073] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and NaOH is used as a precipitant and ammonia is used as a complexing agent to coprecipitate to obtain hydroxide precursors. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 5:1.

[0074] (2) After drying the hydroxide precursor at 120℃ for 12h, it was mixed with LiOH·H2O. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in LiOH·H2O, with a lithium:manganese molar ratio of 1.80:1. Then, it was placed in a high-temperature annealing furnace with a magnetic field strength of 0.5T and calcined at 500℃ for 5h. The magnetic field strength was then adjusted to 0.5T, and the temperature was raised to 800℃ and calcined for 13h to obtain the final product.

[0075] Example 9

[0076] A low-spin manganese-based cathode material prepared by magnetic field-assisted calcination is described below:

[0077] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and NaOH is used as a precipitant and ammonia is used as a complexing agent to coprecipitate to obtain hydroxide precursor. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 6:1.

[0078] (2) After drying the hydroxide precursor at 120℃ for 12h, it was mixed with LiOH·H2O. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in LiOH·H2O, with a lithium:manganese molar ratio of 1.75:1. Then, it was placed in a high-temperature annealing furnace with a magnetic field strength of 0.35T and calcined at 500℃ for 5h. The magnetic field strength was then adjusted to 0.35T, and the temperature was raised to 800℃ for calcination for 14h to obtain the final product.

[0079] Example 10

[0080] A low-spin manganese-based cathode material prepared by magnetic field-assisted calcination is described below:

[0081] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and NaOH is used as a precipitant and ammonia is used as a complexing agent to coprecipitate to obtain hydroxide precursor. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 7:1.

[0082] (2) After drying the hydroxide precursor at 120℃ for 12h, it was mixed with LiOH·H2O. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in LiOH·H2O, with a lithium:manganese molar ratio of 1.70:1. Then, it was placed in a high-temperature annealing furnace with a magnetic field strength of 0.45T and calcined at 500℃ for 5h. The magnetic field strength was then adjusted to 0.45T, and the temperature was raised to 800℃ for calcination for 15h to obtain the final product.

[0083] Example 11

[0084] A low-spin manganese-based cathode material prepared by plasma calcination is described below:

[0085] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and NaOH is used as a precipitant and ammonia is used as a complexing agent to co-precipitate to obtain hydroxide precursor. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 3:1.

[0086] (2) After drying the hydroxide precursor at 120℃ for 12h, it was mixed with LiOH·H2O. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in LiOH·H2O, with a lithium:manganese molar ratio of 5:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcination at 500℃ for 10min, the temperature was raised to 800℃ and calcined for 10min to obtain the final product.

[0087] Example 12

[0088] A low-spin manganese-based cathode material prepared by plasma calcination is described below:

[0089] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and NaOH is used as a precipitant and ammonia is used as a complexing agent to coprecipitate to obtain hydroxide precursor. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 4:1.

[0090] (2) After drying the hydroxide precursor at 120℃ for 12h, it was mixed with LiOH·H2O. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in LiOH·H2O, with a lithium:manganese molar ratio of 1.88:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcination at 500℃ for 10min, the temperature was raised to 800℃ and calcined for 10min to obtain the final product.

[0091] Example 13

[0092] A low-spin manganese-based cathode material prepared by plasma calcination is described below:

[0093] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and NaOH is used as a precipitant and ammonia is used as a complexing agent to coprecipitate to obtain hydroxide precursor. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 1:1.

[0094] (2) After drying the hydroxide precursor at 120℃ for 12h, it was mixed with LiOH·H2O. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in LiOH·H2O, with a lithium:manganese molar ratio of 3:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcination at 500℃ for 20min, the temperature was raised to 800℃ and calcined for 20min to obtain the final product.

[0095] Example 14

[0096] A low-spin manganese-based cathode material prepared by plasma and magnetic field-assisted calcination is described below:

[0097] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and NaOH is used as a precipitant and ammonia is used as a complexing agent to coprecipitate to obtain hydroxide precursor. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 2:1.

[0098] (2) After drying the hydroxide precursor at 120℃ for 12h, it was mixed with LiOH·H2O. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in LiOH·H2O, with a lithium:manganese molar ratio of 2.26:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcination at 500℃ for 20min, the temperature was raised to 800℃ for 20min, while a magnetic field of 0.20T was applied to obtain the final product.

[0099] Example 15

[0100] A low-spin manganese-based cathode material prepared by plasma and magnetic field-assisted calcination is described below:

[0101] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor material is 1:1.

[0102] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 3:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcining at 500℃ for 20min, the temperature was raised to 800℃ for 20min, while a magnetic field of 0.30T was applied to obtain the final product.

[0103] Example 16

[0104] A low-spin manganese-based cathode material prepared by plasma and magnetic field-assisted calcination is described below:

[0105] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 2:1.

[0106] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 2.26:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcining at 500℃ for 20min, the temperature was raised to 800℃ for 10min, while a magnetic field of 0.40T was applied to obtain the final product.

[0107] Example 17

[0108] A low-spin manganese-based cathode material prepared by plasma and magnetic field-assisted calcination is described below:

[0109] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 7:1.

[0110] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 1.7:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcining at 500℃ for 10min, the temperature was raised to 800℃ for 20min, while a magnetic field of 0.50T was applied to obtain the final product.

[0111] Example 18

[0112] A low-spin manganese-based cathode material prepared by plasma and magnetic field-assisted calcination is described below:

[0113] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and NaOH is used as a precipitant and ammonia is used as a complexing agent to coprecipitate to obtain hydroxide precursor. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 6:1.

[0114] (2) After drying the hydroxide precursor at 120℃ for 12h, it was mixed with LiOH·H2O. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in LiOH·H2O, with a lithium:manganese molar ratio of 1.75:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcining at 500℃ for 10min, the temperature was raised to 900℃ for 10min, while a magnetic field of 0.50T was applied to obtain the final product.

[0115] Example 19

[0116] A low-spin manganese-based cathode material prepared by plasma and magnetic field-assisted calcination is described below:

[0117] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and NaOH is used as a precipitant and ammonia is used as a complexing agent to coprecipitate to obtain hydroxide precursors. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 9:1.

[0118] (2) After drying the hydroxide precursor at 120℃ for 12h, it was mixed with LiOH·H2O. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in LiOH·H2O, with a lithium:manganese molar ratio of 0.5:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcining at 300℃ for 10min, the temperature was raised to 800℃ for 10min, while a magnetic field of 0.50T was applied to obtain the final product.

[0119] Example 20

[0120] A low-spin manganese-based cathode material prepared by plasma and magnetic field-assisted calcination is described below:

[0121] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor material is 5:1.

[0122] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 1.80:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcining at 500℃ for 10min, the temperature was raised to 1000℃ for 20min, while a magnetic field of 0.40T was applied to obtain the final product.

[0123] Example 21

[0124] A low-spin manganese-based cathode material prepared by plasma and magnetic field-assisted calcination is described below:

[0125] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 6:1.

[0126] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 1.80:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcining at 300℃ for 10min, the temperature was raised to 900℃ for 20min, while a magnetic field of 0.40T was applied to obtain the final product.

[0127] Example 22

[0128] A low-spin manganese-based cathode material prepared by plasma and magnetic field-assisted calcination is described below:

[0129] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 7:1.

[0130] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 1.70:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcining at 400℃ for 10min, the temperature was raised to 1000℃ for 20min, while a magnetic field of 0.30T was applied to obtain the final product.

[0131] Example 23

[0132] A low-spin manganese-based cathode material prepared by plasma and magnetic field-assisted calcination is described below:

[0133] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor material is 5:1.

[0134] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 1.80:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcining at 500℃ for 10min, the temperature was raised to 800℃ for 20min, while a magnetic field of 0.3T was applied to obtain the final product.

[0135] Example 24

[0136] A low-spin manganese-based cathode material prepared by plasma and magnetic field-assisted calcination is described below:

[0137] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor material is 1:1.

[0138] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 3:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcining at 500℃ for 20min, the temperature was raised to 800℃ for 10min, while a magnetic field of 0.40T was applied to obtain the final product.

[0139] Example 25

[0140] A low-spin manganese-based cathode material prepared by plasma and magnetic field-assisted calcination is described below:

[0141] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 2:1.

[0142] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 2.26:1. Then, it was placed in a plasma environment and oxygen was introduced. It was calcined at 800℃ for 20min while a magnetic field of 0.40T was applied to obtain the final product.

[0143] Example 26

[0144] A low-spin manganese-based cathode material prepared using high-temperature plasma and magnetic field assistance is described in the following process:

[0145] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of manganese moles to the sum of the number of nickel and cobalt moles in the precursor material is 3:1.

[0146] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 2:1. Then, it was placed in a plasma environment and oxygen was introduced. It was treated at 800℃ for 10min while a magnetic field of 0.40T was applied to obtain the final product.

[0147] Comparative Example 1

[0148] A manganese-based cathode material prepared by magnetic field-assisted calcination is described below:

[0149] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor is 1:1.

[0150] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 3:1. Then, it was placed in a high-temperature annealing furnace with a magnetic field strength of 0.10T and calcined at 500℃ for 7h. After maintaining the magnetic field strength at 0.10T, the temperature was raised to 800℃ and calcined for 12h to obtain the final product.

[0151] Comparative Example 2

[0152] A manganese-based cathode material prepared by magnetic field-assisted calcination is described below:

[0153] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor is 1:1.

[0154] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 3:1. Then, it was placed in a high-temperature annealing furnace with a magnetic field strength of 0.20T and calcined at 200℃ for 7h. After maintaining the magnetic field strength at 0.20T, the temperature was raised to 1200℃ and calcined for 12h to obtain the final product.

[0155] Comparative Example 3

[0156] A manganese-based cathode material prepared using high-temperature plasma and magnetic field assistance is described below:

[0157] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor material is 1:1.

[0158] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 3:1. The mixture was placed in a plasma environment and oxygen was introduced. After calcining at 500℃ for 20min, the temperature was raised to 800℃ for 10min, while a magnetic field of 0.10T was applied to obtain the final product.

[0159] Comparative Example 4

[0160] A manganese-based cathode material prepared using high-temperature plasma and magnetic field assistance is described below:

[0161] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor material is 1:1.

[0162] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 3:1. Then, it was placed in a plasma environment and oxygen was introduced. After calcining at 200℃ for 20min, the temperature was raised to 500℃ for 10min, while a magnetic field of 0.30T was applied to obtain the final product.

[0163] Comparative Example 5

[0164] A manganese-based cathode material, the preparation method of which is as follows:

[0165] (1) Manganese sulfate monohydrate, cobalt sulfate heptahydrate and nickel sulfate hexahydrate are dissolved in deionized water, and co-precipitated with Na2CO3 as precipitant and ammonia water as complexing agent to obtain carbonate precursor. The ratio of the number of moles of manganese to the sum of the number of moles of nickel and cobalt in the precursor material is 1:1.

[0166] (2) After drying the carbonate precursor at 120℃ for 12h, it was mixed with Li2CO3. The amounts of both were calculated based on the manganese element in the precursor material and the lithium element in Li2CO3, with a lithium:manganese molar ratio of 2:1. Then, it was placed in a high-temperature annealing furnace and calcined at 500℃ for 6h, followed by calcination at 800℃ for 12h to obtain the final product.

[0167] The electrochemical performance of the manganese-based cathode materials prepared in Examples 1-26 and Comparative Examples 1-5 of this invention was tested, and the results are shown in Table 1. Then, the 1C discharge capacity of the low-spin-state manganese-based cathode materials prepared in Examples 3, 12, and 15 of this invention and Comparative Example 5 was tested, and the spin state of the manganese-based cathode materials prepared in Examples 3 and 5 was characterized. The results are shown in Table 1. Figures 1-4 .

[0168] Table 1 Electrochemical performance

[0169]

[0170]

[0171]

[0172] As shown in Table 1 and Figures 2-4 As shown, compared with Comparative Examples 1 to 5, the electrochemical performance of the manganese-based cathode material with low spin state prepared by the technical solution described in Examples 1 to 26 of the present invention is superior, indicating that only by using the technical solution of the present invention can a manganese-based cathode material with excellent electrochemical energy in the low spin state be prepared.

[0173] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for improving the cycling performance of a manganese-based cathode material, characterized in that, The manganese-containing precursor material is mixed with a lithium source, and a spin state of manganese ions in the manganese-based material is reduced by using calcination combined with magnetic field assistance and / or high-temperature plasma treatment, and then a cathode material is prepared therefrom; The calcination process is completed by calcining at 300-500 DEG C for 5-10 h and then calcining at 800-1000 DEG C for 10-15 h. When the spin state of manganese ions in the manganese-based material is reduced by using magnetic field assistance, the magnetic field strength in the two calcination processes is 0.2-0.5 T.

2. The method of claim 1, wherein, The ratio of the number of moles of lithium in the lithium source to the number of moles of manganese in the manganese-containing precursor material is 0.5:1-5:

1.

3. The method of claim 2, wherein, The manganese-containing precursor material is a carbonate precursor or a hydroxide precursor; and the lithium source is LiOH·H2O or Li2CO3.

4. A manganese-based cathode material prepared by the method of any one of claims 1-3.

5. Use of the manganese-based cathode material of claim 4 as a cathode in the preparation of lithium ion batteries, metal lithium batteries, solid-state lithium batteries and negative electrode-free lithium batteries.

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