A potassium-ion battery cathode material, its preparation method and application

Abstract

This invention discloses a potassium-ion battery cathode material, its preparation method, and its application. The general chemical formula of the cathode material is K. w [Mn x Fe y Cu z Mg a Zr b Al c O2, where 0.40≤w≤0.50, 0.75≤x≤0.85, 0.02≤y≤0.06, 0.02≤z≤0.06, 0.02≤a≤0.06, 0.02≤b≤0.06, 0.02≤c≤0.06; and satisfying x+y+z+a+b+c=1.

Description

Technical Field

[0001] This invention relates to the field of potassium-ion battery technology, specifically to a surface-bulk phase doped potassium-ion battery cathode material, its preparation method, and its application. Background Technology

[0002] With the rapid adoption of high-energy-density lithium-ion batteries in electric vehicles and energy storage, the scarcity and cost of lithium resources are becoming increasingly prominent, making potassium-ion batteries, which are abundant and inexpensive, a highly promising alternative technology. In potassium-ion battery cathode materials, layered metal oxides (especially manganese-based layered metal oxides K0) are... x MnO2 has attracted much attention due to its high specific capacity and simple preparation. However, this type of material, especially during high-voltage cycling, faces core technical bottlenecks such as rapid capacity decay and poor cycling stability caused by the Jahn-Teller effect of manganese ions, irreversible phase transitions, and repeated volume changes during potassium ion insertion / extraction. Traditional single-element doping strategies can improve its electrochemical performance to some extent, but they often come at the expense of other aspects. For example, elements used for stabilizing the bulk structure may hinder the rapid diffusion of potassium ions, while surface-modifying elements contribute little to the stability of the bulk structure. This results in the doping elements' functions not synergistically, or even conflicting with each other, making it difficult to achieve a synergistic improvement in both high specific capacity and ultra-long cycle life. Summary of the Invention

[0003] In view of this, the present invention proposes a potassium-ion battery cathode material based on surface-bulk phase doping, its preparation method and application, aiming to overcome the problems of poor cycle performance and rapid capacity decay caused by the structural instability of existing manganese-based solid metal oxide cathode materials, and to achieve a synergistic improvement in high specific capacity and long cycle life.

[0004] To achieve the above objectives, one aspect of the present invention proposes the following technical solution:

[0005] A potassium-ion battery cathode material with the general chemical formula K w [Mn x Fe y Cu z Mg a Zr b Al c O2, where 0.40≤w≤0.50, 0.75≤x≤0.85, 0.02≤y≤0.06, 0.02≤z≤0.06, 0.02≤a≤0.06, 0.02≤b≤0.06, 0.02≤c≤0.06; and satisfying x + y + z + a + b + c = 1.

[0006] Furthermore, its c-axis lattice constant is between 7.12 Å and 7.14 Å.

[0007] Furthermore, the interplanar spacing of its layered structure (003) is between 2.37 Å and 2.38 Å.

[0008] Furthermore, its bulk structure is a single layered structure.

[0009] Furthermore, the elements K, Mn, Fe, Cu, Mg, Zr, Al, and O are all uniformly distributed in the particles of this potassium-ion battery cathode material.

[0010] Another aspect of the present invention provides a method for preparing the aforementioned potassium-ion battery cathode material, comprising the following steps: S1, using K2CO3, Mn2O3, Fe2O3, CuO, MgO, ZrO2 and Al2O3 as raw materials and mixing them in a preset ratio; S2, calcining the mixed materials at a predetermined temperature range to obtain the potassium-ion battery cathode material.

[0011] Further, in step S1, the mixture is prepared according to the following molar ratio:

[0012] K2CO3 : Mn2O3 : Fe2O3 : CuO : MgO : ZrO2 : Al2O3 = (0.20~0.25) : (0.375~0.425) : (0.01~0.03) : (0.02~0.06) : (0.02~0.06) : (0.02~0.06) : (0.01~0.03).

[0013] Furthermore, the high-temperature calcination in step S2 is carried out at a temperature range of 750℃ to 850℃.

[0014] Furthermore, in step S2, the temperature is raised to the predetermined temperature at a heating rate of 1~5℃ / min and then calcined for 10~15 hours.

[0015] Another aspect of the present invention also proposes the application of the aforementioned potassium-ion battery cathode material, which is used as a cathode material for potassium-ion batteries.

[0016] The beneficial effects of this invention are as follows: By employing a magnesium, zirconium, and aluminum multi-component co-doping strategy, the c-axis lattice constant of the manganese-based layered metal oxide is increased to the range of 7.12-7.14 Å, expanding the potassium ion interlayer spacing and lowering the energy barrier for potassium ion insertion / extraction, thereby improving the potassium ion diffusion rate and enhancing the material's rate performance. Simultaneously, the multi-component doping of magnesium, zirconium, and aluminum effectively stabilizes the layered structure of the material, suppressing lattice distortion and phase transitions during charge and discharge, alleviating volume strain, and significantly improving the material's cycle stability. Furthermore, Mg, Zr, and Al doping forms a high-entropy material, which can suppress the occurrence of side reactions at the electrode-electrolyte interface, helping to form a stable interface layer on the material surface and reducing manganese ion dissolution. This achieves a synergistic improvement in both specific capacity and long cycle life, fundamentally solving the technical challenge of balancing high specific capacity and long cycle life in potassium-ion battery manganese-based layered metal oxide cathode materials.

[0017] By adjusting the chemical composition and crystal structure parameters, the potassium-ion cathode material provided by this invention exhibits excellent cycle stability and rate performance while maintaining high specific capacity.

[0018] By using a specific solid-state sintering preparation method, uniform doping of multiple elements and formation of a single layered structure are achieved. The process is simple and easy to scale up. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the preparation process of Example 1 and Comparative Example 1 of the present invention;

[0020] Figure 2 These are the XRD patterns of Embodiment 1 and Comparative Example 1 of the present invention;

[0021] Figure 3-1 and Figure 3-2 These are the refined XRD patterns of Embodiment 1 and Comparative Example 1 of the present invention;

[0022] Figure 4 This is a scanning electron microscope image of Comparative Example 1;

[0023] Figure 5 This is a scanning electron microscope image of Embodiment 1 of the present invention;

[0024] Figure 6 This is an EDS element distribution diagram of Embodiment 1 of the present invention;

[0025] Figure 7 This is the TEM image of Comparative Example 1;

[0026] Figure 8 This is the TEM image of Embodiment 1 of the present invention;

[0027] Figure 9These are charge-discharge curves of Embodiment 1 and Comparative Example 1 of the present invention;

[0028] Figure 10 These are long-cycle performance diagrams of Embodiment 1 and Comparative Example 1 of the present invention;

[0029] Figure 11 These are the rate performance diagrams for Embodiment 1 and Comparative Example 1 of the present invention;

[0030] Figure 12 These are the electrochemical impedance spectra of Example 1 and Comparative Example 1 of the present invention;

[0031] Figure 13-1 This is a diffusion coefficient diagram of potassium ions (intercalated with potassium) in Example 1 and Comparative Example 1 of the present invention;

[0032] Figure 13-2 This is a diagram of the (depotassium-free) potassium ion diffusion coefficient of Example 1 and Comparative Example 1 of the present invention;

[0033] Figure 14 These are TOF-SIMS analysis diagrams of Embodiment 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0034] This invention addresses the problems of structural instability, rapid capacity decay, and poor cycle performance of manganese-based layered metal oxide cathode materials in potassium-ion batteries. By employing a multi-component co-doping strategy with magnesium, zirconium, and aluminum, the crystal structure and chemical composition of the material are controlled, potassium ion diffusion channels are expanded, and the layered structure is stabilized, thereby achieving a synergistic improvement in high specific capacity and long cycle life.

[0035] To achieve the above objectives, a specific embodiment of the present invention proposes a potassium-ion battery cathode material based on surface-bulk phase doping, which has the chemical formula K w [Mn x Fe y Cu z Mg a Zr b Al c O2, where 0.40≤w≤0.50, 0.75≤x≤0.85, 0.02≤y≤0.06, 0.02≤z≤0.06, 0.02≤a≤0.06, 0.02≤b≤0.06, 0.02≤c≤0.06; and satisfying x + y + z + a + b + c = 1. The preparation method of this cathode material includes the following steps:

[0036] S1. Using K2CO3, Mn2O3, Fe2O3, CuO, MgO, ZrO2, and Al2O3 as raw materials, mix them according to the following molar ratio:

[0037] K2CO3 : Mn2O3 : Fe2O3 : CuO : MgO : ZrO2 : Al2O3 = (0.20~0.25) : (0.375~0.425) : (0.01~0.03) : (0.02~0.06) : (0.02~0.06) : (0.02~0.06) : (0.01~0.03);

[0038] S2. The mixed materials are subjected to solid-state sintering in air to obtain the aforementioned potassium-ion battery cathode material. The solid-state sintering is carried out at a temperature range of 750℃ to 850℃; the heating rate during solid-state sintering is 1 to 5℃ / min, and the sintering time is 10 to 15 hours.

[0039] The obtained potassium-ion battery cathode material K w [Mn x Fe y Cu z Mg a Zr b Al c O2 has a single layered structure with a c-axis lattice constant between 7.12 Å and 7.14 Å and an interlayer spacing (i.e., the (003) interplane spacing) between 2.37 Å and 2.38 Å.

[0040] Example 1

[0041] like Figure 1 As shown, K₂CO₃, Mn₂O₃, Fe₂O₃, CuO, MgO, ZrO₂, and Al₂O₃ were used as raw materials. These raw materials were mixed uniformly in a molar ratio of K₂CO₃:Mn₂O₃:Fe₂O₃:CuO:MgO:ZrO₂:Al₂O₃ = 0.225:0.4:0.02:0.04:0.04:0.04:0.02. The mixture was then heated to 850℃ at a rate of 2℃ / min and calcined for 10 hours. After cooling, the high-entropy cathode material K₂CO₃ was obtained. 0.45 Mn 0.8 Fe 0.04 Cu 0.04 MgO 0.04 Zr 0.04 Al 0.04 O2 (abbreviated as MZA-KMFCO).

[0042] Example 2

[0043] The only difference between this embodiment and Example 1 is that the molar ratio of the raw materials is adjusted. These raw materials are mixed evenly according to the molar ratio of K2CO3 : Mn2O3 : Fe2O3 : CuO : MgO : ZrO2 : Al2O3 = 0.3 : 0.375 : 0.025 : 0.02 : 0.06 : 0.06 : 0.03. Then, the temperature is raised to 800℃ at a heating rate of 3℃ / min, calcined for 12 hours, and cooled to obtain the high-entropy cathode material K. 0.6 Mn 0.75 Fe 0.05 Cu 0.02 MgO 0.06 Zr 0.06 Al 0.06 O2.

[0044] Example 3

[0045] The only difference between this embodiment and Example 1 is that the molar ratio of the raw materials is adjusted. These raw materials are mixed evenly according to the molar ratio of K2CO3 : Mn2O3 : Fe2O3 : CuO : MgO : ZrO2 : Al2O3 = 0.2 : 0.425 : 0.01 : 0.03 : 0.03 : 0.04 : 0.015. Then, the temperature is raised to 750℃ at a heating rate of 5℃ / min, calcined for 15 hours, and cooled to obtain the high-entropy cathode material K. 0.4 Mn 0.85 Fe 0.02 Cu 0.03 MgO 0.03 Zr 0.04 Al 0.03 O2.

[0046] Comparative Example 1

[0047] like Figure 1 As shown, K2CO3, Mn2O3, Fe2O3, and CuO were used as raw materials. These raw materials were mixed uniformly in a molar ratio of K2CO3 : Mn2O3 : Fe2O3 : CuO = 0.225 : 0.4 : 0.05 : 0.1. Then, following the same sintering process as in Example 1, the mixture was cooled to obtain the positive electrode material K. 0.45 Mn 0.8 Fe 0.1 Cu 0.1 O2 (abbreviated as KMFCO).

[0048] It should be understood that Embodiment 1 of the present invention can be regarded as being based on K 0.45 Mn 0.8 Fe 0.1 Cu 0.1O2 was used as the matrix material, and site-selective doping with Mg, Zr, and Al was performed, replacing some of the Fe and Cu sites.

[0049] The two sample materials MZA-KMFCO and KMFCO obtained in Example 1 and Comparative Example 1, respectively, were characterized:

[0050] The crystal structure of the samples was characterized by X-ray diffraction (XRD) using a Bruker D8 Advance diffractometer with CuKα rays (wavelength λ = 0.15406 nm) as the radiation source. The operating conditions were a tube voltage of 45 kV and a tube current of 40 mA. The angular range was 10°–80°, and the scan rate was 10° / min. The XRD patterns of the two samples are shown below. Figure 2 As shown, the results indicate that all samples exhibit the characteristics of a P3' type layered structure in the C2 / m space group, and no heterophase formation was found, indicating that the co-doping of Mg, Zr, and Al in this invention did not induce the formation of heterophase. Figure 2 In the text, PDF#16-0205 represents the XRD standard card number of the material as 16-0205.

[0051] Detailed crystal structure information for both samples was obtained through refinement using GSAS II software, such as... Figure 3-1 and Figure 3-2 As shown, the relevant refinement results are summarized in Table 1. XRD refinement results indicate that after site-selective doping with Mg, Zr, and Al, the c-axis lattice constant of the material increases, and the interlayer spacing, i.e., the (003) interplanar spacing, is expanded, which is beneficial for optimizing the potassium ion diffusion channels, thereby improving the electrochemical performance of the material. Compared with the undoped reference material KMFCO (c-axis lattice constant 7.01464 Å), the c-axis lattice constant of the material synthesized in Example 1 of this invention increases by approximately 0.115 Å, reaching 7.12981 Å, and the potassium ion interlayer spacing is approximately 2.377 Å, indicating that the multiple doped elements (Mg, Zr, Al) successfully enter the lattice, and the dopants with larger ionic radii (such as Zr) are more readily absorbed. 4+ It enters the transition metal layer, which expands the upper and lower oxygen layers, thus causing the c-axis to expand.

[0052] An increased c-axis means a wider potassium ion interlayer spacing, which lowers the energy barrier for potassium ion insertion / extraction, accelerates ion diffusion rate, and alleviates volume strain during charge and discharge, resulting in better rate performance and longer cycle life.

[0053] Table 1 XRD Refinement Data

[0054]

[0055] from Figure 2It can be seen that the strength of the material MZA-KMFCO obtained by doping with Mg, Zr and Al is improved. This is direct evidence of the improved crystal quality of the material, indicating that the doped material has larger grains, a more complete structure and fewer internal defects and stresses.

[0056] Through multi-element doping, this invention successfully broadened the width of the potassium ion diffusion channel from approximately 2.338 Å to approximately 2.377 Å, an increase of approximately 0.04 Å. This structural optimization is a key physical basis for improving the rate performance and cycling stability of the material.

[0057] The morphology of the material was characterized by field emission scanning electron microscopy (HITACHI S-4800, SU 8010) equipped with an energy dispersive spectroscopy (EDS, IXRF SYSTEM, 550i). The relevant results are as follows: Figure 4 and Figure 5 As shown, where Figure 4 The images show the microstructure of sample KMFCO from Comparative Example 1 at different magnifications. Figure 5 The images show the microstructure of the MZA-KMFCO sample from Example 1 at different magnifications. Scanning electron microscopy reveals that, compared to existing KMFCO materials, the MZA-KMFCO material synthesized in Example 1 exhibits a more uniformly distributed secondary particle structure. Microstructure comparison indicates that the dopant elements refined and homogenized the size of the primary particles. This is attributed to the segregation of dopants at grain boundaries, effectively suppressing the excessive growth of abnormal grains and ultimately forming a particle population with better monodispersity.

[0058] like Figure 6 The image shows the EDS elemental distribution map of the sample from Example 1 of this invention. The EDS elemental distribution map further demonstrates that K, Mn, Fe, Cu, Mg, Zr, Al, and O elements are uniformly distributed in the sample particles, indicating that the dopant elements were successfully introduced and well dispersed. This result confirms that the multi-element doping process was successfully carried out without inducing elemental segregation or forming impurity phases, effectively maintaining the structural integrity and compositional uniformity of the primary particles. Each dopant element is uniformly distributed in the host material and highly miscible with the host element. This indicates the successful construction of a multi-element doped cathode material with uniform composition and regular structure, exhibiting high phase purity in its microstructure.

[0059] Figure 7 , Figure 8 The images are TEM images of samples from Comparative Example 1 and Example 1 of the present invention, respectively. Figure 7 The microstructure of KMFCO material before doping is shown, in which Figure 7The left side (a) shows an HRTEM (High-Resolution Transmission Electron Microscopy) image of the KMFCO material, which shows that its bulk phase has a layered structure. Figure 7 The right side (b) is a magnified view, showing a uniform rock salt phase on the material surface. Figure I shows the layered structure, and Figure II shows the rock salt phase structure. In its original state, the material exhibits a mixed phase morphology of layered structure and rock salt phase, with the TMO-TMO interlayer spacing d of the layered structure approximately 0.64 nm and the rock salt phase region size approximately 3-5 nm. After doping with multiple elements such as Mg, Zr, and Al, the material transforms into the high-entropy material MZA-KMFCO. During this process, a significant structural transformation occurs: the rock salt phase completely disappears, and the material completely transforms into a single layered structure. Figure 8 This indicates that multi-element doping effectively promotes structural homogenization, inhibits the formation of the rock salt phase, and enhances the stability of the layered structure, thereby achieving structural purification from a mixed phase to a single layered phase. This structural evolution also suggests that high-entropy design plays an important role in regulating the crystal structure and phase composition of materials, which helps to improve the electrochemical performance of materials in applications such as potassium-ion battery cathode materials.

[0060] To verify the performance of the potassium-ion battery cathode material of the present invention in the application of potassium-ion battery cathodes, the embodiments of the present invention also prepared potassium-ion battery cathodes using the two samples of Example 1 and Comparative Example 1, respectively. The process is as follows:

[0061] First, the electrode slurry was prepared. The sample, used as the positive electrode active material, was mixed with acetylene black and polyvinylidene fluoride (PVDF, Solef 5130) at a mass ratio of 8:1:1 in N-methylpyrrolidone (NMP) solvent and stirred until homogeneous. The prepared electrode slurry was then uniformly coated onto an aluminum foil current collector, with a positive electrode active material mass loading of 1.5–2 mg·cm⁻¹. -2 The coated electrodes were dried in a vacuum oven at 120°C for 12 hours, then punched into circular electrode sheets with a diameter of 12 mm and transferred to an argon-filled glove box (LABstar MBRAUN, Germany).

[0062] Next, the batteries were assembled. The battery assembly adopted a CR2032 coin cell structure, using the electrode sheet prepared above as the positive electrode, potassium metal as the negative electrode, and a polyvinylidene fluoride (PVDF) membrane as the separator. Each battery was injected with 150 μL of electrolyte, specifically 2.5 mol / L potassium bis(fluorosulfonyl)imide (KFSI)-triethyl phosphate (TEP).

[0063] Finally, the electrochemical performance of the batteries was tested. The electrochemical performance of the coin cells was tested using a multi-channel battery testing system (LAND CT 2001 A, China), with a voltage range of 1.5–4.0 V (relative to K+ / K). Figure 9 As shown, the battery sample of the MZA-KMFCO material in this embodiment of the invention was tested at 20 mA g. -1 The initial discharge specific capacity at the current density reached 100 mAh / g, significantly higher than the 90 mAh / g of the undoped KMFCO battery sample, indicating that the high-entropy doping strategy of this invention effectively improved the reversible capacity and potassium-ion storage capacity of the material. Figure 10 As shown, after 10m Ag -1 After three activation cycles at current density, the battery reached 20010 mA g. -1 Long-term cycling tests were conducted under current density conditions. The results showed that the battery sample made of the MZA-KMFCO material of this invention maintained 83% capacity retention after 100 cycles, significantly better than the 58% retention of the undoped KMFCO battery sample. This demonstrates that the high-entropy doping strategy of this invention has significant advantages in improving structural stability and cycle life. Furthermore, as... Figure 11 As shown, the MZA-KMFCO battery sample at current density (mA g) -1 It exhibits excellent rate performance under all conditions, further verifying its good electrochemical kinetic characteristics and potassium ion diffusion ability.

[0064] Electrochemical impedance spectroscopy (EIS) measurements were performed on a multichannel electrochemical workstation (VMP3, Biologic), with a frequency range of 100 kHz to 10 mHz. Figure 12 As shown, compared with the battery sample of undoped KMFCO material, the battery sample of MZA-KMFCO material in this embodiment of the invention has a significantly reduced impedance, indicating that the high-entropy doping strategy of the present invention effectively reduces the interfacial resistance and enhances the migration ability of potassium ions in the electrode material, thereby helping to improve the electrochemical reaction kinetics performance of the material.

[0065] The lithium-ion diffusion coefficient (DK+) was determined by galvanostatic intermittent titration (GITT) at 10 mA g. -1 The test was conducted at a specific current density, with a voltage range of 1.5–4.0 V. During the test, the battery was charged at a constant current for 20 minutes, followed by a 2-hour resting period to achieve a quasi-equilibrium state. Figure 13-1 and Figure 13-2As shown, compared with the battery sample of undoped KMFCO material, the battery sample of MZA-KMFCO material exhibits a higher potassium ion diffusion coefficient, indicating that the high-entropy doping strategy effectively optimizes the crystal structure of the material, broadens the potassium ion migration channel and reduces the diffusion resistance, thereby helping to improve the rate performance and kinetic reactivity of the material.

[0066] Figure 14 These are time-of-flight secondary ion mass spectrometry (TOF-SIMS) images of the materials, where (a) is the TOF-SIMS image of KMFCO material and (b) is the TOF-SIMS image of the doped MZA-KMFCO material. Figure 14 The TOF-SIMS analysis results clearly reveal the crucial role of Mg, Zr, and Al doping in suppressing electrolyte decomposition and stabilizing the material structure of the high-entropy material MZA-KMFCO. Compared with undoped KMFCO material, the KMFCO on the electrode surface of the high-entropy material in this embodiment of the invention exhibits significantly higher KMFCO content. - C2HO - and CH3O - The signal intensity of secondary ion fragments was significantly reduced. These fragments are typical products of electrolyte solvent decomposition, and their signal reduction directly proves that the introduction of high-entropy materials effectively suppressed the occurrence of side reactions at the electrode-electrolyte interface, forming a more stable interface layer. Meanwhile, the MnF3 on the surface of the high-entropy material... - The signal strength is relatively enhanced. This enhancement does not stem from increased manganese dissolution, but rather indicates the formation of a more stable fluorine-containing protective layer at the interface. This protective layer effectively immobilizes manganese ions, preventing further dissolution, which directly corresponds to the observed reduction in manganese dissolution.

[0067] In summary, the embodiments of this invention, by constructing a Mg-Zr-Al multi-element high-entropy doped system, achieved a specific capacity of up to 100 mAh / g and a capacity retention rate of ≥83% after 100 cycles, significantly outperforming existing KMFCO single-doped systems. The advancement of this technology lies in proposing a synergistic enhancement mechanism of "surface interface protection - bulk structure stability," effectively overcoming the technical bottleneck of the single modification dimension of traditional doping strategies. It establishes a highly competitive new paradigm for surface-bulk phase partitioning functionalized material design, possessing significant technical barriers and promotional value.

Claims

1. A potassium-ion battery cathode material, characterized in that: Its general chemical formula is K w [Mn x Fe y Cu z Mg a Zr b Al c O2, wherein 0.40≤w≤0.50, 0.75≤x≤0.85, 0.02≤y≤0.06, 0.02≤z≤0.06, 0.02≤a≤0.06, 0.02≤b≤0.06, 0.02≤c≤0.06; and satisfying x+y+z+a+b+c=1; its c-axis lattice constant is between 7.12Å and 7.14Å; its layered structure (003) interplanar spacing is between 2.37Å and 2.38Å; its bulk structure is a single layered structure; K, Mn, Fe, Cu, Mg, Zr, Al and O elements are uniformly distributed in the particles of this potassium-ion battery cathode material.

2. The method for preparing the potassium-ion battery cathode material as described in claim 1, characterized in that, Includes the following steps: S1. K2CO3, Mn2O3, Fe2O3, CuO, MgO, ZrO2 and Al2O3 are used as raw materials and mixed in a predetermined ratio; S2. The mixed materials are calcined at high temperature within a predetermined temperature range to obtain the potassium-ion battery cathode material. In step S1, the mixture is prepared according to the following molar ratio: K2CO3 : Mn2O3 : Fe2O3 : CuO : MgO : ZrO2 : Al2O3 = (0.20~0.25) : (0.375~0.425) : (0.01~0.03) : (0.02~0.06) : (0.02~0.06) : (0.02~0.06) : (0.01~0.03); In step S2, the high-temperature calcination is carried out at a temperature range of 750℃ to 850℃.

3. The preparation method according to claim 2, characterized in that, In step S2, the temperature is raised to the predetermined temperature at a heating rate of 1~5℃ / min, and then calcined for 10~15 hours.

4. The application of the potassium-ion battery cathode material as described in claim 1, characterized in that, Used as a positive electrode material in potassium-ion batteries.

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