Barium-doped oxide solid electrolyte for lithium batteries and method for preparing the same

Abstract

This invention discloses a barium-doped oxide solid electrolyte for lithium batteries and its preparation method, belonging to the field of lithium battery technology. The chemical formula of the solid electrolyte is Li. 3+x La 1‑x Ba x (PO4)2, where 0 < x ≤ 0.05, this solid electrolyte is a monoclinic phase with an ionic conductivity greater than 1 × 10⁻⁵ at room temperature. ‑4 S / cm. The preparation method includes: mixing sodium, lanthanum, phosphorus, and barium source compounds in a molar ratio of (3+x):(1-x):2:x, ball milling, drying, and calcining to obtain a sodium-based precursor, which is then subjected to an ion exchange reaction with a lithium salt to obtain the final product. This invention introduces oxygen vacancies through barium doping, optimizing the lithium-ion transport channel and significantly improving ionic conductivity, reaching a maximum of 7.1 × 10⁻⁶, while maintaining the stability of the monoclinic framework. ‑4 S / cm. This solid electrolyte is low in cost, exhibits excellent thermal and electrochemical stability, and is suitable for high-performance lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to a barium-doped oxide solid electrolyte for lithium batteries and its preparation method. Background Technology

[0002] With the rapid development of new energy vehicles, portable electronic devices, and other fields, the safety, energy density, and cycle life of lithium batteries have become key factors restricting their further development. Traditional liquid electrolyte lithium batteries have safety hazards such as leakage, combustion, and explosion, and their energy density improvement potential is limited, failing to meet the needs of high-end devices.

[0003] Solid-state electrolytes, as core components of next-generation lithium batteries, possess significant advantages such as good thermal stability, wide electrochemical window, and no risk of leakage. They can effectively solve the safety issues of liquid electrolytes and provide possibilities for the development of high-energy-density lithium batteries. Oxide solid-state electrolytes have become a research hotspot in the field of solid-state electrolytes due to their good chemical stability and mechanical strength. Among them, the novel oxide solid-state electrolyte lithium lanthanum phosphate (Li3La(PO4)2, abbreviated as LLPO) has broad application prospects due to its near-practical room-temperature ionic conductivity, low Young's modulus, and excellent thermal and electrochemical stability.

[0004] However, LLPO still has many shortcomings: on the one hand, its room temperature ionic conductivity has not yet met the ideal requirements of commercial lithium batteries, and the sintering temperature is high and the sintering time is long, resulting in high preparation costs; on the other hand, the doping elements selected in some doping modification schemes are scarce and expensive, which is not conducive to large-scale production, and the doping effect is limited, making it difficult to achieve the multiple goals of improving conductivity, optimizing preparation process and controlling cost at the same time.

[0005] Barium is widely available and inexpensive. Its ionic radius matches well with some ions in oxide solid electrolyte matrices, theoretically allowing for the manipulation of the electrolyte's crystal structure through doping. This could increase oxygen vacancy concentration, promote lithium-ion transport, and simultaneously lower sintering temperature and shorten sintering time. However, current research on barium-doped oxide solid electrolytes remains insufficient. A mature, stable, and scalable technology has not yet been developed. The doping ratio and preparation process parameters need further optimization to fully leverage the modifying effect of barium doping and improve the overall performance of the solid electrolyte. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of insufficient conductivity of oxide solid electrolytes in the prior art, and to provide a barium-doped oxide solid electrolyte for lithium batteries and its preparation method. Through reasonable barium doping ratio design and optimized preparation process, the room temperature ionic conductivity of the solid electrolyte is improved, meeting the practical application requirements of lithium batteries.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A barium-doped oxide solid electrolyte for lithium batteries, with the chemical formula Li 3+x La 1-x Ba x (PO4)2, where 0 < x ≤ 0.05, the solid electrolyte is a monoclinic phase and has a room temperature ionic conductivity greater than 1 × 10⁻⁵. -4 S / cm.

[0009] Preferably, the value of x is in the range of 0.03 ≤ x ≤ 0.05, and the room temperature ionic conductivity is 5.5 × 10⁻⁶. -4 ~7.1×10 -4 S / cm.

[0010] Preferably, the solid electrolyte has a particle size of 100-500 nm and a specific surface area of ​​10-30 m². 2 / g.

[0011] The present invention also provides a method for using a barium-doped oxide solid electrolyte for lithium batteries, comprising the following steps:

[0012] (1) Raw material pretreatment: Sodium source compound, lanthanum source compound, phosphorus source compound and barium source compound are mixed in a molar ratio of (3+x):(1-x):2:x and then dried, where 0<x≤0.05;

[0013] (2) Ball milling: The pretreated raw materials are ball milled and mixed to obtain a mixed powder;

[0014] (3) Drying: Dry the ball-milled mixed powder to remove the mixing medium;

[0015] (4) Calcination treatment: The dried powder is calcined in air atmosphere and cooled to obtain sodium-based precursor;

[0016] (5) Lithium-sodium exchange: The sodium-based precursor is subjected to an ion exchange reaction with lithium salt, and after separation and drying, the barium-doped oxide solid electrolyte is obtained.

[0017] Preferably, in step (1), the sodium source compound is selected from at least one of sodium carbonate, sodium hydroxide, and sodium nitrate; the lanthanum source compound is selected from at least one of lanthanum oxide, lanthanum nitrate, and lanthanum hydroxide; the phosphorus source compound is selected from at least one of sodium phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate; and the barium source compound is selected from at least one of barium carbonate, barium oxide, and barium nitrate.

[0018] Preferably, in step (1), the sodium source compound is sodium carbonate, the lanthanum source compound is lanthanum oxide, the phosphorus source compound is ammonium dihydrogen phosphate, and the barium source compound is barium carbonate.

[0019] Preferably, in step (1), the amount of sodium source compound added is 5% to 10% in excess of the theoretical molar amount.

[0020] Preferably, in step (2), the ball milling is performed using a planetary ball mill, the ball milling media is zirconia balls, the ball-to-material ratio is (5~10):1; the ball milling speed is 300~400 rpm, and the ball milling time is 6~24 hours; the mixing medium is an alcohol solvent, and the mass ratio of raw material to mixing medium is 1:(1~3); the alcohol solvent is selected from at least one of ethanol, isopropanol, and ethylene glycol.

[0021] Preferably, in step (4), the calcination temperature is 900~1200℃ and the time is 10~20 hours; the calcination adopts a gradient heating method with a heating rate of 5~10℃ / min.

[0022] Preferably, in step (5), the lithium salt is selected from at least one of lithium chloride, lithium sulfate, lithium hydroxide and lithium bis(trifluoromethanesulfonylimide); the ion exchange reaction is carried out in a reaction vessel at a reaction temperature of 100~200℃ and a holding time of 10~30 hours; the mass ratio of the sodium-based precursor to the lithium salt is 1:(1~10); the drying temperature is 60~90℃ and the time is 10~20 hours.

[0023] Beneficial effects

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. This invention uses barium as a dopant element. Barium is widely available and inexpensive, significantly reducing the preparation cost of solid-state electrolytes compared to rare dopant elements commonly used in existing technologies, which is beneficial for large-scale production. Simultaneously, the introduction of barium ions can effectively regulate the lattice parameters of the crystal structure, increase the oxygen vacancy concentration, promote rapid lithium ion transport, and increase the room-temperature ionic conductivity of the solid-state electrolyte to 1×10⁻⁶. -4 S / cm and above, reaching a maximum of 7.1×10 -4 S / cm, close to the practical requirements of commercial lithium batteries.

[0026] 2. By optimizing the barium doping ratio (0 < x ≤ 0.05), especially the preferred range of 0.03 ≤ x ≤ 0.05, this invention can maximize the modification effect of barium doping while ensuring the stability of the solid electrolyte crystal structure. It avoids ineffective modification due to too low doping amount or impurity phase and destruction of crystal structure due to too high doping amount, thus taking into account both the ionic conductivity and structural stability of the solid electrolyte.

[0027] 3. This invention optimizes the preparation process parameters of the solid-state reaction method. By reasonably controlling the ball milling time, calcination temperature, calcination time and sintering conditions, and by adopting gradient heating sintering, it can effectively reduce the agglomeration of raw materials, improve the density and dispersibility of solid electrolytes, and further optimize their ion transport performance.

[0028] 4. The barium-doped oxide solid electrolyte prepared by this invention exhibits good thermal and electrochemical stability, and a wide electrochemical window (0~5V vs Li / Li). + It can effectively suppress side reactions inside lithium batteries, avoiding safety hazards such as leakage and combustion. At the same time, it has good compatibility with the positive and negative electrode materials of lithium batteries, which can significantly improve the cycle life and energy density of lithium batteries. It is suitable for various high-performance lithium batteries and has broad application prospects. Attached Figure Description

[0029] Figure 1 The images show the X-ray diffraction (XRD) patterns of LLPO materials before and after barium doping. The lower curve represents pure-phase LLPO, and the upper curve represents barium-doped LLPO. Figure 1 It can be seen that the positions of the diffraction peaks before and after doping are basically the same, and no obvious impurity peaks or peak position shifts are observed, indicating that barium doping has not changed the monoclinic crystal structure of LLPO.

[0030] Figure 2 The images show the electrochemical impedance spectroscopy (EIS) spectra of LLPO materials before and after barium doping, where the radius of the semicircle represents the ion transport resistance of the material. Figure 2 As can be seen, the semi-circular radius of the barium-doped LLPO (upper curve) is significantly smaller than that of the pure phase LLPO (lower curve), indicating that barium doping significantly reduces the resistance of the solid electrolyte, and the calculated ionic conductivity increases by about 1.6 times. Detailed Implementation Plan

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The described examples are merely 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.

[0032] Example 1

[0033] I. Preparation of Barium-Doped Oxide Solid Electrolytes

[0034] This embodiment prepares a barium-doped oxide solid electrolyte for lithium batteries, with the chemical formula Li. 3+x La 1-x Ba x (PO4)2, where x = 0.03. This solid electrolyte has a monoclinic phase structure.

[0035] The preparation method includes the following steps:

[0036] Raw material pretreatment: Sodium carbonate (Na₂CO₃), lanthanum oxide (La₂O₃), ammonium dihydrogen phosphate (NH₄H₂PO₄), and barium carbonate (BaCO₃) were selected as raw materials, with sodium carbonate in excess at 5% (to compensate for sodium volatilization during high-temperature calcination). The molar ratio of the four raw materials was 3.03:0.97:2:0.03. The four raw materials were each placed in a drying oven at 75℃ for 6 hours to remove moisture and impurities.

[0037] Mixing and ball milling: The pretreated raw materials were placed in a planetary ball mill, and ethanol was added as the mixing medium at a mass ratio of 1:1. Zirconia balls were used as the milling medium, with a ball-to-material ratio of 5:1. The milling speed was 300 rpm, and the milling time was 10 hours to obtain a uniform mixed powder.

[0038] Drying: The ball-milled mixed powder was placed in a drying oven at 75°C and dried for 6 hours to remove ethanol, resulting in the dried powder.

[0039] Calcination treatment: The dried powder was placed in a high-temperature furnace and heated to 1000°C at a heating rate of 5°C / min under air atmosphere. After calcination for 15 hours, the sodium-based precursor NLPO (Na3La(PO4)2) was obtained after cooling to room temperature.

[0040] Lithium-sodium exchange: The calcined product NLPO was placed in a reactor containing lithium sulfate and heat-treated at 150°C for 15 hours. The mass ratio of NLPO to lithium sulfate was 1:5. After the reaction, the product was centrifuged and washed three times, then dried at 80°C for 10 hours and cooled to room temperature to obtain the barium-doped oxide solid electrolyte product LLPO (Li₂PO₄). 3.03 La 0.97 Ba 0.03 (PO4)2).

[0041] II. Crystal Structure Characterization

[0042] The LLPO sample prepared in this embodiment was subjected to X-ray diffraction testing, and the results are as follows: Figure 1 The curve above shows this. Simultaneously, an undoped pure-phase LLPO sample was prepared as a control. Figure 1 (See the curve below). Comparing the two curves, it can be seen that the diffraction peak positions of barium-doped LLPO are basically consistent with those of pure-phase LLPO, with no obvious impurity diffraction peaks or peak position shifts. This indicates that the introduction of barium ions did not destroy the original monoclinic crystal structure of LLPO, and the dopant element uniformly entered the lattice positions.

[0043] III. Ionic Conductivity Test

[0044] The LLPO sample prepared in this embodiment was pressed into a sheet, and gold electrodes were sputtered onto both sides. Its room-temperature ionic conductivity was measured using electrochemical impedance spectroscopy (EIS). The test frequency range was 1 Hz to 1 MHz, and the AC amplitude was 10 mV. The results are as follows: Figure 2 As shown by the curve above, its semicircular radius is significantly smaller than that of pure phase LLPO ( Figure 2 (See the curve below). Calculations show that the total ionic conductivity of LLPO in this embodiment at room temperature is 7.1 × 10⁻⁶. -4 The ionic conductivity of pure-phase LLPO is 4.4 × 10⁻⁶ S / cm, while that of pure-phase LLPO is 4.4 × 10⁻⁶. -4 S / cm (see comparative example), barium doping increased the ionic conductivity by approximately 61%.

[0045] Example 2

[0046] I. Preparation of Barium-Doped Oxide Solid Electrolytes

[0047] This embodiment prepares a barium-doped oxide solid electrolyte for lithium batteries, with the chemical formula Li. 3+x La 1-x Ba x (PO4)2, where x = 0.05. This solid electrolyte has a monoclinic phase structure.

[0048] The preparation method includes the following steps:

[0049] Raw material pretreatment: Sodium carbonate (Na₂CO₃), lanthanum oxide (La₂O₃), ammonium dihydrogen phosphate (NH₄H₂PO₄), and barium carbonate (BaCO₃) were selected as raw materials, with sodium carbonate in excess at 8%. The molar ratio of the four raw materials was 3.05:0.95:2:0.05. The four raw materials were each placed in a drying oven at 80℃ for 8 hours to remove moisture and impurities.

[0050] Mixing and ball milling: The pretreated raw material was placed in a planetary ball mill, and isopropanol was added as the mixing medium. The mass ratio of raw material to isopropanol was 1:2. The ball milling medium was zirconia balls, the ball-to-material ratio was 8:1, the ball milling speed was 350 rpm, and the ball milling time was 16 hours to obtain a uniform mixed powder.

[0051] Drying: The ball-milled mixed powder was placed in a drying oven at 80°C and dried for 8 hours to remove isopropanol, resulting in the dried powder.

[0052] Calcination treatment: The dried powder was placed in a high-temperature furnace and heated to 850°C at a heating rate of 8°C / min in an air atmosphere. After calcination for 12 hours, the sodium-based precursor NLPO was obtained after cooling to room temperature.

[0053] Lithium-sodium exchange: The calcined product NLPO was placed in a reactor containing lithium bis(trifluoromethanesulfonyl)imide and heat-treated at 100°C for 10 hours. The mass ratio of NLPO to lithium bis(trifluoromethanesulfonyl)imide was 1:8. After centrifugation and washing three times, it was dried at 70°C for 12 hours and cooled to room temperature to obtain the barium-doped oxide solid electrolyte product LLPO (Li 3.05 La 0.95 Ba 0.05 (PO4)2).

[0054] II. Crystal Structure Characterization

[0055] Using the same XRD testing method as in Example 1, the diffraction pattern of the LLPO sample prepared in this example also showed a monoclinic phase with no impurity peaks, indicating that the doping amount of x=0.05 is still within the lattice solid solubility range.

[0056] III. Ionic Conductivity Test

[0057] Using the same EIS testing method as in Example 1, the room temperature total ionic conductivity of LLPO in this example was measured to be 5.5 × 10⁻⁶. -4 S / cm. Compared with the comparative example pure phase LLPO (4.4 × 10⁻⁶). -4 Compared to (S / cm), the ionic conductivity is increased by about 25%.

[0058] Comparative Example

[0059] Using the same raw materials and preparation process as in Example 2, except that no barium source compound (barium carbonate) was added, a pure-phase Li3La(PO4)2 solid electrolyte was prepared. XRD analysis confirmed its monoclinic phase structure, and EIS analysis showed a room-temperature ionic conductivity of 4.4 × 10⁻⁶. -4 S / cm.

[0060] Summary of Results from Examples and Comparative Examples

[0061] sample x value Crystal structure Room temperature ionic conductivity (S / cm) Comparative Example 0 monoclinic phase <![CDATA[4.4×10 -4 <!-- 4 -->]]> Example 1 0.03 monoclinic phase <![CDATA[7.1×10 -4 ]]> Example 2 0.05 monoclinic phase <![CDATA[5.5×10 -4 ]]>

[0062] The results above show that, through barium doping modification, this invention significantly improves the room-temperature ionic conductivity of oxide solid electrolytes while maintaining the monoclinic crystal structure. The improvement is most significant when x=0.03, achieving a conductivity of 7.1×10⁻⁶. -4 The S / cm ratio was improved by approximately 61% compared to the undoped sample.

[0063] The barium-doped oxide solid electrolyte Li provided by this invention 3+x La 1-x Ba x (PO4)2 (LLPO) is prepared by a two-step solid-state reaction method. Its reaction mechanism mainly includes two stages: precursor formation and ion exchange. The regulation mechanism of barium doping on crystal structure and ion transport performance is as follows.

[0064] I. Precursor Formation Stage (Solid-Phase Reaction)

[0065] Sodium source compound (sodium carbonate Na2CO3 as an example), lanthanum source compound (lanthanum oxide La2O3 as an example), phosphorus source compound (ammonium dihydrogen phosphate NH4H2PO4 as an example), and barium source compound (barium carbonate BaCO3 as an example) are mixed in stoichiometric ratio and subjected to solid-phase reaction by high-temperature calcination to generate sodium-based precursor Na3La. 1-x Ba x (PO4)2 (NLPO). During calcination, NH4H2PO4 decomposes to produce NH3 and H2O, while carbonates decompose to produce CO2, promoting the solid-phase diffusion reaction to proceed fully and forming a NASICON-type framework with a monoclinic phase structure.

[0066] II. Ion exchange stage (lithium-sodium exchange)

[0067] The sodium-based precursor NLPO is reacted with a lithium salt (lithium sulfate Li₂SO₄ as an example) in the liquid phase via an ion exchange reaction. + By Li + Replacement, and simultaneously barium ions (Ba) in the crystal lattice 2+ The product is stably retained, and the target product LLPO is finally obtained.

[0068] Due to Li + Radius smaller than Na + The radius and the unit cell volume shrink slightly after ion exchange, but the monoclinic phase framework structure is completely maintained, providing a continuous three-dimensional transport channel for lithium ions.

[0069] III. Mechanism of Barium Doping in Enhancing Ionic Conductivity

[0070] Lattice distortion and oxygen vacancy generation: Ba 2+ The ionic radius is larger than that of the substituted La. 3+ . Dangba2+ Occupy La 3+ At the site of lithium ion hopping, additional oxygen vacancies (VO··) are generated in the lattice to maintain charge balance. The introduction of oxygen vacancies lowers the activation energy barrier for lithium ion hopping migration, promoting lithium ion hopping. + Rapid diffusion within the skeletal structure.

[0071] Channel size optimization: Ba 2+ The large radius of the Li-ion crystal leads to local lattice expansion, increasing the channel size at the lithium-ion transport bottleneck. + Migration resistance is reduced. XRD pattern ( Figure 1 The results show that the diffraction peaks did not shift significantly after doping, indicating that the lattice expansion was compensated by the local relaxation of oxygen vacancies, and the overall structure remained stable.

[0072] Defect correlation effect: When doped to a suitable level (x≤0.05), Ba 2+ Uniformly dispersed in the crystal lattice, the oxygen vacancies formed are independent, creating efficient ion migration pathways. When the doping concentration exceeds 0.05%, excess Ba... 2+ This may lead to the aggregation of a second phase or disruption of the framework structure, resulting in a decrease in conductivity. The preferred range of the present invention (0.03 ≤ x ≤ 0.05) achieves an optimal balance between structural stability and ionic conductivity.

[0073] Synergistic effect of preparation process: The gradient temperature calcination process used in this invention promotes the calcination of Ba. 2+ Uniform solid solution treatment avoids localized segregation; ball milling refines raw material particles, shortening the diffusion distance for solid-phase reactions; lithium-sodium exchange is carried out under low-temperature liquid-phase conditions, preserving the monoclinic framework of the precursor. These process optimizations, combined with barium doping, result in a room-temperature ionic conductivity of 7.1 × 10⁻⁶. -4 S / cm, compared to the undoped sample (4.4×10⁻⁶). -4 The S / cm ratio increased by approximately 61%.

[0074] IV. Mechanism Diagram Explanation

[0075] Please refer to the attached diagram for further explanation:

[0076] Figure 1 (XRD pattern) confirms that the barium-doped sample still maintains a monoclinic phase structure with no impurity phase formation, indicating that Ba... 2+ It successfully entered the lattice site instead of forming a second phase.

[0077] Figure 2 The EIS spectrum shows that the ion transport resistance is significantly reduced after barium doping, which directly confirms the promoting effect of the above mechanism on lithium ion migration.

[0078] In summary, this invention achieves a significant improvement in the room-temperature ionic conductivity of solid electrolytes by introducing oxygen vacancies and optimizing lithium-ion transport channels while maintaining the stability of the monoclinic phase framework through lattice doping of barium ions and an optimized two-step solid-state reaction process.

[0079] The above embodiments are merely preferred embodiments of the present invention, used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Any modifications, improvements, or equivalent substitutions made to the present invention by those skilled in the art without departing from the technical concept and solutions of the present invention should fall within the scope of protection of the present invention.

Claims

1. A barium-doped oxide solid electrolyte for lithium batteries, characterized in that, Li 3+x La 1-x Ba x (PO4)2, wherein 0 < x < 0.05, the solid state electrolyte is a monoclinic phase, and has a room temperature ionic conductivity greater than 1 x 10 -4 S / cm.

2. The barium-doped oxide solid electrolyte according to claim 1, characterized in that, said x has a value in the range of 0.03≤x≤0.05, and said room temperature ionic conductivity is 5.5 x 10 -4 -7.1 x 10 -4 S / cm.

3. The barium-doped oxide solid electrolyte according to claim 1 or 2, characterized in that, The solid electrolyte has a particle size of 100~500 nm and a specific surface area of ​​10~30 m². 2 / g.

4. A method for preparing a barium-doped oxide solid electrolyte for lithium batteries according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Raw material pretreatment: Sodium source compound, lanthanum source compound, phosphorus source compound and barium source compound are mixed in a molar ratio of (3+x):(1-x):2:x and then dried, where 0<x≤0.05; (2) Ball milling: The pretreated raw materials are ball milled and mixed to obtain a mixed powder; (3) Drying: Dry the ball-milled mixed powder to remove the mixing medium; (4) Calcination treatment: The dried powder is calcined in air atmosphere and cooled to obtain sodium-based precursor; (5) Lithium-sodium exchange: The sodium-based precursor is subjected to an ion exchange reaction with lithium salt, and after separation and drying, the barium-doped oxide solid electrolyte is obtained.

5. The method according to claim 4, characterized in that, In step (1), the sodium source compound is selected from at least one of sodium carbonate, sodium hydroxide, and sodium nitrate; the lanthanum source compound is selected from at least one of lanthanum oxide, lanthanum nitrate, and lanthanum hydroxide; the phosphorus source compound is selected from at least one of sodium phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate; and the barium source compound is selected from at least one of barium carbonate, barium oxide, and barium nitrate.

6. The method according to claim 5, characterized in that, In step (1), the sodium source compound is sodium carbonate, the lanthanum source compound is lanthanum oxide, the phosphorus source compound is ammonium dihydrogen phosphate, and the barium source compound is barium carbonate.

7. The method according to claim 4, characterized in that, In step (1), the amount of sodium source compound added is 5% to 10% in excess of the theoretical molar amount.

8. The method according to claim 4, characterized in that, In step (2), the ball milling is performed using a planetary ball mill, the ball milling media is zirconia balls, the ball-to-material ratio is (5~10):1; the ball milling speed is 300~400 rpm, and the ball milling time is 6~24 hours; the mixing medium is an alcohol solvent, and the mass ratio of raw material to mixing medium is 1:(1~3); the alcohol solvent is selected from at least one of ethanol, isopropanol, and ethylene glycol.

9. The method according to claim 4, characterized in that, In step (4), the calcination temperature is 900~1200℃ and the time is 10~20 hours; the calcination adopts a gradient heating method with a heating rate of 5~10℃ / min.

10. The method according to claim 4, characterized in that, In step (5), the lithium salt is selected from at least one of lithium chloride, lithium sulfate, lithium hydroxide and lithium bis(trifluoromethanesulfonylimide); the ion exchange reaction is carried out in a reaction vessel at a reaction temperature of 100~200℃ and a holding time of 10~30 hours; the mass ratio of the sodium-based precursor to the lithium salt is 1:(1~10); the drying temperature is 60~90℃ and the time is 10~20 hours.

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