Layered-perovskite biphase potassium ion battery positive electrode material as well as preparation method and application thereof

Abstract

The invention provides a layered-perovskite biphase potassium ion battery positive electrode material as well as a preparation method and application thereof, and belongs to the field of new energy materials. The preparation method of the material comprises the following steps: S1, weighing a proper amount of a potassium source, a manganese source and a praseodymium (or lanthanum and gadolinium) source in a ball milling tank; s2, ethanol is added for ball milling treatment, and a mixture is obtained; s3, drying the mixture; s4, the obtained dried product is subjected to heat treatment, the heat treatment temperature is 850-900 DEG C, the heat treatment time is 12-15 h, then the dried product is cooled to the room temperature, and a black product is obtained; and S5, grinding, sieving and drying the obtained product to obtain the positive electrode material of the potassium ion battery. According to the preparation method, a special sintering atmosphere is not needed, the layered-perovskite double-phase positive electrode material can be obtained only through one-time calcination, and the prepared positive electrode material has better circulation and rate performance compared with a layered single-phase positive electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of potassium ion battery positive electrode materials, and in particular to a layered-perovskite dual-phase potassium ion battery positive electrode material, a preparation method thereof, and applications thereof. Background Art

[0002] Due to its high reversible specific capacity, good cycle stability, and zero memory properties, lithium-ion batteries are the most popular portable energy storage devices in the energy storage field and one of the most important commercial energy storage systems. Among them, polyanion systems (mainly lithium iron phosphate) and layered cathode systems (ternary cathodes) are the current mainstream lithium-ion battery cathode materials. However, the high price of source materials makes the manufacturing cost of lithium-ion batteries high, and the reserves of exploitable lithium resources are limited. Therefore, finding alternatives to lithium batteries is one of the important tasks in the current industry.

[0003] Currently, potassium ion batteries have been developed as a low-cost alternative to lithium ion batteries due to the abundance of potassium resources. Among the many potassium ion battery cathode materials, manganese-based layered cathodes (K x MnO2, whose most stable structure is x=0.5) has received widespread attention due to its high reversible specific capacity. However, due to the large potassium ion radius, the material will undergo obvious layer slip during the insertion and extraction of potassium ions (Adv.Energy Mater.2019,9,1900568), which in turn shows slow kinetics and obvious volume changes, accompanied by obvious phase changes, resulting in poor cycle and rate performance. Hindering layer slip, reducing volume changes, and inhibiting phase changes are the main difficulties in improving the cycle and rate performance of layered positive electrode materials for manganese-based potassium ion batteries.

[0004] At present, researchers mainly use strategies such as metal cation doping and dual-phase composite to improve the cycle stability of the material and enhance its rate performance. Among them, the improvement brought by doping modification is relatively limited, while the dual-phase composite strategy can significantly improve the cycle stability and rate performance of the material. The dual-phase positive electrode usually forms a second phase at the crystal (phase) boundary of the positive electrode particles or forms a coating phase such as oxide / phosphate (coating modification). The second phase is mainly carbon, metal oxide, phosphate, spinel, etc. Its mechanism of action is usually to suppress the layer slip and the resulting phase change during the cycle, as well as the volume expansion of the particles, through the second phase with higher stability at the crystal (phase) boundary.

[0005] However, this strategy typically requires multiple sintering processes, which severely impacts its practical application value and may result in a reduction in the capacity of the raw materials. For example, for layered-carbon dual-phase cathodes, it is usually necessary to first coat the carbon source and then perform a secondary heat treatment to achieve carbonization. Some layered-metal oxide dual-phase cathodes require coating the surface of the prepared cathode particles, such as coating alumina particles. However, because the particles cannot be tightly bonded to each other, the coating is usually of limited effectiveness. In order to achieve a significant improvement, the application of costly atomic deposition technology is required (Energy Environ. Sci., 2025, 18, 1879-1900).

[0006] Currently, the preparation of dual-phase cathodes using a single sintering process is challenging, often affecting the composition of the cathode material and even preventing the desired layered cathode phase from being obtained, which in turn affects cycling and rate performance. Therefore, there is an urgent need to develop suitable processes for preparing composite materials and potassium-ion battery cathode materials with improved cycling stability and rate performance. Summary of the Invention

[0007] To address the aforementioned issues with existing technologies, the present invention provides a potassium-ion battery cathode material with layered-perovskite dual-phase characteristics, as well as its preparation method and application. This preparation method does not require a special sintering atmosphere and can produce a layered-perovskite composite material through a single calcination. The resulting cathode material exhibits excellent rate and cycle performance.

[0008] The technical solutions of the present invention are as follows:

[0009] The present invention first provides a layered-perovskite dual-phase potassium ion battery positive electrode material, the chemical formula of the positive electrode material is K 0.5 MnO2 / AMnO3, A=Pr, La or Gd; the positive electrode material is a two-phase composite structure of P phase and perovskite phase, wherein the P phase is layered grains with a diameter of 1-3 microns, and the perovskite phase is nanoparticles with a grain size of 100-300nm, which grow at the grain boundaries of the layered grains, forming a layered-perovskite two-phase structure.

[0010] The present invention also provides a method for preparing the layered-perovskite dual-phase composite potassium ion battery positive electrode material, comprising the following steps:

[0011] S1. Weigh potassium source, manganese source, and A source according to the molar ratio of K:Mn:A = 0.5:1:m, and place them in a ball mill, where m = 0.01-0.1;

[0012] S2, adding ethanol to the ball milling tank and performing ball milling to obtain a mixture;

[0013] S3, drying the mixture, and then heat-treating it at a temperature of 850-900° C. for 12-15 hours; then cooling it to room temperature to obtain a heat-treated product;

[0014] S4. Grinding, sieving, and drying the heat-treated product in sequence to obtain the potassium ion battery positive electrode material.

[0015] Preferably, in step S1, the potassium source is potassium carbonate; the manganese source is manganese trioxide; and the A source is praseodymium undecoxide, lanthanum trioxide or gadolinium trioxide.

[0016] Preferably, in step S2, during the ball milling treatment, the ball-to-material ratio is 1:1-2, the rotation speed of the ball mill is 250-300 r / min, and the ball milling time is 1-2 h.

[0017] Furthermore, in step S2, the ball milling beads used are alumina ball milling beads.

[0018] Preferably, in step S2, the amount of ethanol added is 1-3 times the total mass of the potassium source, the manganese source, and the A source.

[0019] Preferably, in step S3, the atmosphere of the heat treatment is an air atmosphere, and the heating rate during the heat treatment is 3-5°C / min.

[0020] Preferably, in step S3, the cooling rate is 2-3°C / min.

[0021] Preferably, in step S4, the drying is vacuum drying at 100-120° C. for 6-8 hours.

[0022] Preferably, in step S4, the dried heat-treated product is placed in a mortar, fully ground, and then passed through a 200-300 mesh standard sieve.

[0023] The present invention further provides an application of the layered-perovskite dual-phase composite potassium ion battery positive electrode material, and the potassium ion battery is prepared by mixing the positive electrode material with PVDF, conductive carbon black, and NMP.

[0024] Through extensive experiments, we found that only manganese-based layered and perovskite composite cathodes can be produced through a single sintering process. The chemical formula of perovskite material is ABO3. Among them, the A-site ions are usually metal elements with large ionic radius such as rare earth, while the B-site ions are usually transition metal elements. This type of material usually has excellent structural stability, thermal stability, and corrosion resistance. Depending on the elemental composition, it can exhibit various properties such as ion conduction, electron conduction, catalysis, and luminescence. For example, some rare earth perovskites have metal-semiconductor transition characteristics and can exhibit good electronic conductivity within a certain temperature range. Taking praseodymium as an example, we found that when praseodymium ions are present, a Pr-Mn perovskite phase appears at the crystal (phase) boundaries of the layered cathode particles. This second phase grown at the grain boundary can achieve second phase reinforcement, hinder the layer slip of the main phase, inhibit the volume expansion of the main phase, and significantly improve the stability of the main phase. At the same time, praseodymium-containing materials generally have good electrical conductivity, and so does praseodymium manganese perovskite, which can form regions with excellent electrical conductivity around the positive electrode material particles, further improving the performance of the positive electrode material. Under the above-mentioned multiple effects, the layered-perovskite dual-phase positive electrode material exhibits better cycle stability and rate performance than the single-phase layered positive electrode material. In addition, although the Pr-Mn perovskite phase does not have potassium storage capacity, it will not affect the capacity of the layered positive electrode under certain conditions. In summary, the present invention combines the elemental composition characteristics of manganese-based layered potassium ion battery positive electrode materials to design K 0.5 MnO2 / PrMnO3 dual-phase composite cathode, compared with K 0.5 The MnO2 positive electrode has better cycle and rate performance. The effect, distribution and performance of the lanthanum manganate and gadolinium manganate perovskite phase in the composite material are similar to those of praseodymium manganate.

[0025] The method of the present invention can prepare a layered-perovskite composite potassium ion battery cathode material through a single sintering step. Furthermore, by adjusting the Pr, La, or Gd content, the ratio of the layered phase to the perovskite phase can be controlled, thereby achieving customized synthesis of the target material.

[0026] Preferably, the chemical formula of the potassium ion battery positive electrode material is K 0.5 MnO2 / AMnO3. This design primarily utilizes octahedral coordination between Mn and O to form a transition metal layer, with potassium ions intercalating between the layers to form a potassium ion layer. This allows for the growth of a Pr, La, or Gd-Mn perovskite secondary phase at the crystal (phase) boundary, resulting in a low-cost, manganese-based, hierarchical cathode material. Potassium carbonate is inexpensive and readily available, while manganese trioxide is used as the manganese source, making it readily available.

[0027] The beneficial technical effects of the present invention are:

[0028] 1. The present invention prepared the layered-perovskite dual phase (K 0.5MnO2 / AMnO3) composite potassium ion battery positive electrode material is a new type of potassium ion battery positive electrode material. This material grows a perovskite phase at the crystal (phase) boundary of the layered positive electrode particles, which can significantly inhibit the layer slip of the layered positive electrode during the cycle, inhibit its volume expansion during the cycle, and significantly improve the stability of the layered positive electrode during the cycle. In addition, due to the excellent electrical conductivity of Pr, La or Gd-Mn perovskite, K 0.5 The dynamics of MnO2 solves the problem of slow kinetics of the layered cathode and significantly improves its rate performance. This dual-phase cathode material exhibits better cycle and rate performance than traditional layered potassium ion battery cathode materials; at the same time, it also has better cycle stability than doped and modified cathode materials.

[0029] 2. The present invention can prepare a layered-perovskite composite potassium ion battery positive electrode material by only one calcination, which greatly shortens the preparation process of the layered-perovskite composite material. Usually, under high temperature conditions, most metal cations will dissolve into the lattice of the layered positive electrode material to form the most thermodynamically stable phase, thereby playing a role in doping strengthening, but this strategy does not have a significant effect on inhibiting interlayer slip, and may even result in the most thermodynamically stable product obtained being a non-layered positive electrode material. Therefore, most other two-phase processes require secondary heat treatment, and the temperature and time of the previous and subsequent heat treatment processes are different. Praseodymium, lanthanum, and gadolinium ions are not easily dissolved into the layered positive electrode lattice, and Pr or La, Gd-Mn perovskite is a thermodynamically stable phase, and its thermodynamic stability is generally better than that of the layered phase. Therefore, after high-temperature heat treatment, the layered phase can coexist with the perovskite phase.

[0030] 3. The dual-phase composite manganese-based potassium ion battery positive electrode material prepared by the method of the present invention is a low-cost battery material with the characteristics of readily available raw materials, low cost, simple composition and easy preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The XRD diffraction pattern of the potassium ion battery positive electrode material prepared in Example 1;

[0032] Figure 2 This is a scanning electron microscope image of the potassium ion battery positive electrode material prepared in Example 1;

[0033] Figure 3 TEM test image of the potassium ion battery positive electrode material prepared in Example 1;

[0034] Figure 4 This is a graph showing the cycle performance test results of the potassium ion battery positive electrode material prepared in Example 1;

[0035] Figure 5 This is a graph showing the rate performance test results of the potassium ion battery positive electrode material prepared in Example 1;

[0036] Figure 6 This is the XRD test result diagram of the potassium ion battery positive electrode material prepared in Example 3;

[0037] Figure 7 This is a graph showing the cycle performance test results of the potassium ion battery positive electrode material prepared in Example 3;

[0038] Figure 8 This is a graph showing the rate performance test results of the potassium ion battery positive electrode material prepared in Example 3;

[0039] Figure 9 This is a graph showing the cycle performance test results of the potassium ion battery positive electrode material prepared in Comparative Example 1;

[0040] Figure 10 This is a graph showing the rate performance test results of the potassium ion battery positive electrode material prepared in Comparative Example 2;

[0041] Figure 11 This is a graph showing the rate performance test results of the potassium ion battery positive electrode material prepared in Comparative Example 3. DETAILED DESCRIPTION

[0042] The present invention is described in detail below with reference to the accompanying drawings and embodiments. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, rather than all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0043] Example 1:

[0044] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 MnO2 / PrMnO3, the preparation method comprises the following steps:

[0045] S1. Weigh appropriate amounts of potassium carbonate, manganese trioxide, and praseodymium undecoxide in a molar ratio of K:Mn:Pr = 0.5:1:0.02 and place them in a ball mill;

[0046] S2, adding ethanol twice the total mass of potassium carbonate, manganese trioxide, and hexapruleum undecoxide;

[0047] S3. Add alumina ball milling beads to a ball milling jar, and then perform ball milling to obtain a mixture; wherein the rotation speed of the ball milling jar is 300 r / min, the ball milling time is 1 hour, and the ball-to-material ratio is 1:1;

[0048] S4, placing the mixture in a drying oven at 60°C for drying, then placing it in a muffle furnace, heating it to 850°C at a heating rate of 5°C / min in an air atmosphere for heat treatment for 12 hours, and then cooling it to room temperature at a cooling rate of 2°C / min to obtain a heat-treated product;

[0049] S5, the heat-treated product was fully ground, then passed through a 300-mesh standard sieve, and vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K 0.5 MnO2 / PrMnO3.

[0050] The potassium ion battery cathode material K prepared in this embodiment 0.5 The XRD diffraction pattern of MnO2 / PrMnO3 is as follows Figure 1 As shown by Figure 1 It can be seen that the positive electrode material of the ion battery is a composite structure of P phase (R3m) and perovskite (PDF#54-1291, Pm-3m). The scanning electron microscope image of the potassium ion positive electrode material is as follows: Figure 2 The transmission electron microscope image and the corresponding energy spectrum are shown in Figure 3 As shown, from Figure 3 It can be observed that Pr element is enriched in several places at the crystal (phase) boundary, forming the perovskite phase. Figure 1-Figure 3 It can be seen that the positive electrode material prepared in this embodiment is a two-phase composite structure of P phase and perovskite phase, wherein the P phase is layered grains with a diameter of 1-3 microns, and the perovskite phase is nanoparticles with a grain size of 100-300 nm, which grow at the grain boundaries of the layered grains, forming a layered-perovskite two-phase structure.

[0051] The potassium ion battery cathode material K prepared in this example 0.5 MnO2 / PrMnO3 was mixed with PVDF, conductive carbon black, and NMP in a mass ratio of 8:1:1:20 to obtain a slurry with appropriate viscosity, which was then coated on aluminum foil. After drying, the battery positive electrode was obtained, which was then assembled into a 2032 button battery and tested.

[0052] The cycle performance test results and rate performance test results of potassium ion battery positive electrode materials are shown in the figure below. Figure 4 and Figure 5 As shown. Figure 4 and Figure 5 It can be seen that the first cycle discharge capacity of the potassium ion battery cathode material prepared in this embodiment reaches 90 mAh g -1 Above, at 20mA·g -1 The capacity retention rate is as high as 86.6% after 50 cycles under the conditions of 300mA·g -1 Under the condition of current density, it still has 65mAh·g -1The capacity is much higher than the 38 mAh g of pure KMO reported in the literature. -1 (Adv.Mater.2017,29,1702480). In contrast, Figure 9 As shown in the figure, the first cycle discharge capacity of the potassium ion battery positive electrode material prepared by the traditional solid phase method in Comparative Example 1 is also 90 mAh g -1 However, after 50 cycles, the capacity retention rate is only 60%. Obviously, the layered-perovskite composite positive electrode has better cycle and rate performance.

[0053] Example 2:

[0054] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 MnO2 / PrMnO3, the preparation method comprises the following steps:

[0055] S1. Weigh appropriate amounts of potassium carbonate, manganese trioxide, and praseodymium undecoxide in a molar ratio of K:Mn:Pr = 0.5:1:0.04 and place them in a ball mill;

[0056] S2, adding ethanol twice the total mass of potassium carbonate, manganese trioxide, and hexapruleum undecoxide to the ball mill;

[0057] S3. Add alumina ball milling beads to a ball milling jar, and then perform ball milling to obtain a mixture; wherein the rotation speed of the ball milling jar is 300 r / min, the ball milling time is 1 hour, and the ball-to-material ratio is 1:1;

[0058] S4, placing the mixture in a drying oven at 60°C for drying, then placing it in a muffle furnace, heating it to 850°C at a heating rate of 5°C / min in an air atmosphere for heat treatment for 12 hours, and then cooling it to room temperature at a cooling rate of 2°C / min to obtain a heat-treated product;

[0059] S5, the heat-treated product was fully ground, passed through a 300-mesh standard sieve, and vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K 0.5 MnO2 / PrMnO3.

[0060] The battery cathode material prepared in this example is a composite structure of P phase (R3m) and perovskite (PDF#54-1291, Pm-3m) phases. Its basic crystal phase combination and material size are the same as those in Example 1. The first cycle discharge capacity of this potassium ion battery cathode material is about 90 mAh g -1 , with better cycle and rate performance than Comparative Example 1.

[0061] Example 3:

[0062] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5MnO2 / PrMnO3, the preparation method comprises the following steps:

[0063] S1. Weigh appropriate amounts of potassium carbonate, manganese trioxide, and praseodymium undecoxide in a molar ratio of K:Mn:Pr = 0.5:1:0.06 and place them in a ball mill;

[0064] S2, adding ethanol twice the total mass of potassium carbonate, manganese trioxide, and hexapruleum undecoxide to the ball mill;

[0065] S3. Add alumina ball milling beads to a ball milling jar, and then perform ball milling to obtain a mixture; wherein the rotation speed of the ball milling jar is 300 r / min, the ball milling time is 1 hour, and the ball-to-material ratio is 1:1;

[0066] S4, placing the mixture in a drying oven at 60°C for drying, then placing it in a muffle furnace, heating it to 850°C at a heating rate of 5°C / min in an air atmosphere for heat treatment for 12 hours, and then cooling it to room temperature at a cooling rate of 2°C / min to obtain a heat-treated product;

[0067] S5, the heat-treated product was fully ground, passed through a 300-mesh standard sieve, and vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K 0.5 MnO2 / PrMnO3.

[0068] The XRD pattern of the material prepared in this example is as follows: Figure 6 As shown in the figure, this material has a typical two-phase structure, with the same basic crystal phase composition and material dimensions as Example 1. The main peak (003) and secondary peak of the P3 phase are located at approximately 2θ≈13° and 2θ≈26°, respectively. Peaks corresponding to the perovskite phase of PDF#54-1291 are also observed. Furthermore, because the Pr content is increased in this example, the proportion of the perovskite phase in this material is significantly increased.

[0069] The potassium ion battery cathode material K prepared in this example 0.5 MnO2 was mixed with PVDF, conductive carbon black, and NMP in a mass ratio of 8:1:1:20 to obtain a slurry with appropriate viscosity, which was then coated on aluminum foil. After drying, the battery positive electrode was obtained, which was then assembled into a 2032 button battery and tested.

[0070] The cycle performance test results and rate performance test results of potassium ion battery positive electrode materials are shown in the figure below. Figure 7 and Figure 8 As shown. Figure 7 and Figure 8 It can be seen that the first cycle discharge capacity of the potassium ion battery cathode material prepared in this embodiment reaches 90 mAh g -1 About 20mA·g -1After 50 cycles under the conditions of -1 Under the condition of current density, there is still 45mAh·g -1 The capacity is still higher than the 38 mAh g of pure KMO reported in the literature. -1 In contrast, Figure 9 As shown in the figure, the first cycle discharge capacity of the potassium ion battery positive electrode material prepared by the traditional solid phase method in Comparative Example 1 is also 90 mAh g -1 However, after 50 cycles, the capacity retention rate is only 60%.

[0071] Example 4:

[0072] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 MnO2 / PrMnO3, the preparation method comprises the following steps:

[0073] S1. Weigh appropriate amounts of potassium carbonate, manganese trioxide, and praseodymium undecoxide in a molar ratio of K:Mn:Pr = 0.5:1:0.08 and place them in a ball mill;

[0074] S2, adding 1.5 times the total mass of potassium carbonate, manganese trioxide, and praseodymium undecoxide to the ball mill;

[0075] S3. Add alumina ball milling beads to a ball milling jar, and then perform ball milling to obtain a mixture; wherein the rotation speed of the ball milling jar is 280 r / min, the ball milling time is 1.5 h, and the ball-to-material ratio is 1:1.5;

[0076] S4, placing the mixture in a drying oven at 60°C for drying, then placing it in a muffle furnace, heating it to 870°C at a heating rate of 3°C / min in an air atmosphere for heat treatment for 13.5h, and then cooling it to room temperature at a cooling rate of 3°C / min to obtain a heat-treated product;

[0077] S5, the heat-treated product was fully ground, passed through a 200-mesh standard sieve, and vacuum-dried at 100° C. for 8 h to obtain the potassium ion battery positive electrode material K 0.5 MnO2 / PrMnO3.

[0078] The obtained battery positive electrode material is a composite structure of P phase (R3m) and perovskite (PDF#54-1291, Pm-3m). The basic crystal phase combination and material size are the same as those in Example 1. The performance as a potassium ion battery positive electrode is similar to that of Examples 1-3.

[0079] Example 5:

[0080] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5MnO2 / PrMnO3, the preparation method comprises the following steps:

[0081] S1. Weigh appropriate amounts of potassium carbonate, manganese trioxide, and praseodymium undecoxide in a molar ratio of K:Mn:Pr = 0.5:1:0.08 and place them in a ball mill;

[0082] S2, adding ethanol 2.5 times the total mass of potassium carbonate, manganese trioxide, and hexapruleum undecoxide to the ball mill;

[0083] S3. Add alumina ball milling beads to a ball milling jar, and then perform ball milling to obtain a mixture; wherein the rotation speed of the ball milling jar is 250 r / min, the ball milling time is 2 h, and the ball-to-material ratio is 1:2;

[0084] S4, placing the mixture in a drying oven at 60°C for drying, then placing it in a muffle furnace, heating it to 900°C at a heating rate of 4°C / min in an air atmosphere for heat treatment for 15 hours, and then cooling it to room temperature at a cooling rate of 3°C / min to obtain a heat-treated product;

[0085] S5, the heat-treated product was fully ground, passed through a 300-mesh standard sieve, and vacuum-dried at 110° C. for 7 h to obtain the potassium ion battery positive electrode material K 0.5 MnO2 / PrMnO3.

[0086] The obtained battery positive electrode material is a composite structure of P phase (R3m) and perovskite (PDF#54-1291, Pm-3m). The basic crystal phase combination and material size are the same as those in Example 1. The performance as a potassium ion battery positive electrode is similar to that of Examples 1-3.

[0087] Example 6:

[0088] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 MnO2 / LaMnO3, the preparation method comprises the following steps:

[0089] S1. Weigh appropriate amounts of potassium carbonate, manganese trioxide, and lanthanum trioxide according to the molar ratio of K:Mn:La = 0.5:1:0.02 and place them in a ball mill;

[0090] S2, adding ethanol twice the total mass of potassium carbonate, manganese trioxide, and lanthanum trioxide to the ball mill;

[0091] S3. Add alumina ball milling beads to a ball milling jar, and then perform ball milling to obtain a mixture; wherein the rotation speed of the ball milling jar is 300 r / min, the ball milling time is 1 hour, and the ball-to-material ratio is 1:1;

[0092] S4, placing the mixture in a drying oven at 60°C for drying, then placing it in a muffle furnace, heating it to 890°C at a heating rate of 5°C / min in an air atmosphere for heat treatment for 14 hours, and then cooling it to room temperature at a cooling rate of 2°C / min to obtain a heat-treated product;

[0093] S5, the heat-treated product was fully ground, then passed through a 300-mesh standard sieve, and vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K 0.5 MnO2 / LaMnO3.

[0094] The potassium ion battery positive electrode material K prepared in this embodiment 0.5 The XRD diffraction pattern of MnO2 / / LaMnO3 shows that the positive electrode material of the potassium ion battery is a composite structure of P phase (R3m) and perovskite (PDF#54-1291, Pm-3m). The transmission electron microscopy image and the corresponding energy spectrum results show that the La element is enriched in several places at the crystal (phase) boundaries, forming a perovskite phase. The positive electrode material prepared in this embodiment is a dual-phase composite structure of P phase and perovskite phase, wherein the P phase is layered grains with a diameter of 1-3 microns, and the perovskite phase is nanoparticles with a grain size of 100-300nm, which grow at the grain boundaries of the layered grains, forming a layered-perovskite dual-phase structure.

[0095] The potassium ion battery cathode material prepared in this example was assembled into a 2032 button cell according to the method provided in Example 1 and tested. The experimental results show that when the rare earth ion used is lanthanum, the first cycle discharge capacity of the prepared layered cathode-perovskite dual-phase cathode reaches 90 mAh g -1 Above, at 20mA·g -1 The capacity retention rate after 50 cycles under the conditions of 85.6% is 85.6%.

[0096] Example 7:

[0097] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 MnO2 / GdMnO3, the preparation method comprises the following steps:

[0098] S1. Weigh appropriate amounts of potassium carbonate, manganese trioxide, and gadolinium trioxide according to the molar ratio of K:Mn:Gd=Gd:1:0.02 and place them in a ball mill;

[0099] S2. Add ethanol twice the total mass of potassium carbonate, manganese trioxide, and gadolinium trioxide to the ball mill;

[0100] S3. Add alumina ball milling beads to a ball milling jar, and then perform ball milling to obtain a mixture; wherein the rotation speed of the ball milling jar is 285 r / min, the ball milling time is 1 h, and the ball-to-material ratio is 1:1;

[0101] S4, placing the mixture in a drying oven at 60°C for drying, then placing it in a muffle furnace, heating it to 875°C at a heating rate of 5°C / min in an air atmosphere for heat treatment for 13.5h, and then cooling it to room temperature at a cooling rate of 2°C / min to obtain a heat-treated product;

[0102] S5, the heat-treated product was fully ground, then passed through a 200-mesh standard sieve, and vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K 0.5 MnO2 / GdMnO3.

[0103] The potassium ion battery positive electrode material K prepared in this embodiment 0.5 The XRD diffraction pattern of MnO2 / / GdMnO3 shows that the positive electrode material of the potassium ion battery is a composite structure of P phase (R3m) and perovskite (PDF#54-1291, Pm-3m). The transmission electron microscopy image and the corresponding energy spectrum results show that the Gd element is enriched in several places at the crystal (phase) boundaries, forming a perovskite phase. The positive electrode material prepared in this embodiment is a dual-phase composite structure of P phase and perovskite phase, wherein the P phase is layered grains with a diameter of 1-3 microns, and the perovskite phase is nanoparticles with a grain size of 100-300nm, which grow at the grain boundaries of the layered grains, forming a layered-perovskite dual-phase structure.

[0104] The potassium ion battery cathode material prepared in this example was assembled into a 2032 button cell according to the method provided in Example 1 and tested. The experimental results show that when the rare earth ion used is gadolinium, the first cycle discharge capacity of the prepared layered cathode-perovskite dual-phase cathode reaches 90 mAh g -1 Above, at 20mA·g -1 The capacity retention rate after 50 cycles under the conditions of 80.6% was 80.6%.

[0105] Comparative Example 1:

[0106] The chemical formula of the potassium ion battery cathode material prepared in this comparative example is K 0.5 MnO2, its preparation method comprises the following steps:

[0107] S1. Weigh appropriate amounts of potassium carbonate and manganese trioxide according to the molar ratio of K:Mn = 0.5:1 and place them in a ball mill;

[0108] S2. Add alumina ball milling beads to a ball milling jar, and then perform ball milling to obtain a mixture; wherein the rotation speed of the ball milling jar is 300 r / min, the ball milling time is 1 hour, and the ball-to-material ratio is 1:1;

[0109] S3, placing the mixture in a drying oven at 60°C for drying, then placing it in a muffle furnace, heating it to 850°C at a heating rate of 5°C / min in an air atmosphere for heat treatment for 12 hours, and then cooling it to room temperature at a cooling rate of 2°C / min to obtain a heat-treated product;

[0110] S4, the obtained product was fully ground, then passed through a 300-mesh standard sieve, and vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K 0.5 MnO2.

[0111] The potassium ion battery positive electrode material K prepared in this comparative example 0.5 MnO2 was mixed with PVDF, conductive carbon black, and NMP in a mass ratio of 8:1:1:20 to obtain a slurry with appropriate viscosity, which was then coated on aluminum foil. After drying, the battery positive electrode was obtained, which was then assembled into a 2032 button battery and tested.

[0112] The cycle performance test results of potassium ion battery positive electrode materials Figure 9 As shown by Figure 9 It can be seen that the capacity retention rate of the potassium ion battery positive electrode material prepared in this comparative example is only 60% after 50 cycles, showing poor battery performance.

[0113] Comparative Example 2:

[0114] The chemical formula of the potassium ion battery cathode material prepared in this comparative example is K 0.5 Mn 0.9 Mg 0.1 O2, the preparation method comprises the following steps:

[0115] S1. Weigh appropriate amounts of potassium carbonate, manganese trioxide, and magnesium oxide according to the molar ratio of K:Mn:Mg = 0.5:0.9:0.1 and place them in a ball mill;

[0116] S2, adding ethanol twice the total mass of potassium carbonate, manganese trioxide, and magnesium oxide to the ball mill;

[0117] S3. Add alumina ball milling beads to a ball milling jar, and then perform ball milling to obtain a mixture; wherein the rotation speed of the ball milling jar is 300 r / min, the ball milling time is 1 hour, and the ball-to-material ratio is 1:1;

[0118] S4, placing the mixture in a drying oven at 60°C for drying, then placing it in a muffle furnace, heating it to 850°C at a heating rate of 5°C / min in an air atmosphere for heat treatment for 12 hours, and then cooling it to room temperature at a cooling rate of 2°C / min to obtain a heat-treated product;

[0119] S5, the heat-treated product was fully ground, then passed through a 300-mesh standard sieve, and vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K 0.5 Mn 0.9 Mg 0.1 O2.

[0120] The potassium ion battery positive electrode material K prepared in this comparative example 0.5 Mn 0.9 Mg 0.1 O2 was mixed with PVDF, conductive carbon black, and NMP in a mass ratio of 8:1:1:20 to obtain a slurry with appropriate viscosity, which was then coated on aluminum foil. After drying, the battery positive electrode was obtained, which was then assembled into a 2032 button battery and tested.

[0121] The structural characterization results show that it is impossible to form a magnesium oxide layer outside the layered cathode particles through a single heat treatment process, and magnesium ions will be dissolved into the lattice of the layered cathode. Figure 10 It can be seen that the cycling performance of the magnesium-doped material is worse than that of the positive electrode obtained in Example 1. After 50 cycles, the capacity retention rate is about 60%, indicating that the layered-perovskite composite positive electrode (Example 1) has better performance than the conventional doping modification scheme, and only 0.02 mol of Pr needs to be added.

[0122] Comparative Example 3:

[0123] The chemical formula of the potassium ion battery cathode material prepared in this comparative example is: K 0.5 Mn 0.9 Cu 0.05 Mg 0.025 Ti 0.025 O2, the preparation method comprises the following steps:

[0124] S1. Weigh appropriate amounts of potassium carbonate, manganese trioxide, copper oxide, magnesium oxide, and titanium oxide according to the molar ratio of K:Mn:Cu:Mg:Ti=0.5:0.9:0.05:0.025:0.025 and place them in a ball mill;

[0125] S2, adding ethanol twice the total mass of potassium carbonate, manganese trioxide, copper oxide, magnesium oxide, and titanium oxide to the ball mill;

[0126] S3. Add alumina ball milling beads to a ball milling jar, and then perform ball milling to obtain a mixture; wherein the rotation speed of the ball milling jar is 300 r / min, the ball milling time is 1 hour, and the ball-to-material ratio is 1:1;

[0127] S4, placing the mixture in a drying oven at 60°C for drying, then placing it in a muffle furnace, heating it to 850°C at a heating rate of 5°C / min in an air atmosphere for heat treatment for 12 hours, and then cooling it to room temperature at a cooling rate of 2°C / min to obtain a heat-treated product;

[0128] S5, after the heat treatment product is fully ground, it is passed through a 300-mesh standard sieve, and vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K 0.5 Mn 0.9 Cu 0.05 Mg 0.025 Ti 0.025 O2.

[0129] The potassium ion battery positive electrode material K prepared in this comparative example 0.5 Mn 0.9 Cu 0.05 Mg 0.025 Ti 0.025 O2 was mixed with PVDF, conductive carbon black, and NMP in a mass ratio of 8:1:1:20 to obtain a slurry with appropriate viscosity, which was then coated on aluminum foil. After drying, the battery positive electrode was obtained, which was then assembled into a 2032 button battery and tested.

[0130] The structural characterization results show that it is impossible to form an oxide coating layer on the outside of the layered cathode particles through a single heat treatment process, and the metal cations will dissolve into the layered cathode lattice. Figure 11 The test results show that the rate performance of the materials doped with various cations is worse than that of the positive electrode obtained in Example 1. -1 The current density is less than 40 mAh g -1 The capacity of the layered-perovskite composite cathode (Example 1) shows better performance and only requires the addition of 0.02 mol of Pr.

[0131] Comparative Example 4:

[0132] The chemical formula of the potassium ion battery cathode material prepared in this comparative example is K 0.5 Mn 0.9 Cu 0.1 O2, the preparation method thereof comprises the following steps:

[0133] S1. Weigh appropriate amounts of potassium carbonate, manganese trioxide, and copper oxide according to the molar ratio of K:Mn:Cu = 0.5:0.9:0.1 and place them in a ball mill;

[0134] S2, adding potassium carbonate, manganese trioxide, and ethanol twice the total mass of copper oxide to the ball mill;

[0135] S3. Add alumina ball milling beads to a ball milling jar, and then perform ball milling to obtain a mixture; wherein the rotation speed of the ball milling jar is 300 r / min, the ball milling time is 1 hour, and the ball-to-material ratio is 1:1;

[0136] S4, placing the mixture in a drying oven at 60°C for drying, then placing it in a muffle furnace, heating it to 850°C at a heating rate of 5°C / min in an air atmosphere for heat treatment for 6 hours, and then cooling it to room temperature at a cooling rate of 2°C / min to obtain a heat-treated product;

[0137] S5, the heat-treated product was fully ground, then passed through a 300-mesh standard sieve, and vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K 0.5 Mn 0.9 Cu 0.1 O2.

[0138] The potassium ion battery positive electrode material K prepared in this comparative example 0.5 Mn 0.9 Cu 0.1 O2 was mixed with PVDF, conductive carbon black, and NMP in a mass ratio of 8:1:1:20 to obtain a slurry with appropriate viscosity, which was then coated on aluminum foil. After drying, the battery positive electrode was obtained, which was then assembled into a 2032 button battery and tested.

[0139] The potassium ion battery positive electrode material K obtained in this comparative example 0.5 Mn 0.9 Cu 0.1 The capacity retention rate of O2 after 50 cycles was 66%, and it was impossible to form a copper oxide layer on the outer surface of the layered positive electrode particles through a single heat treatment process, and the copper ions would be dissolved into the layered phase lattice. The cycling performance of the material after 0.1 mol of Cu doping was worse than that of Example 1, indicating that Example 1 layered-perovskite composite positive electrode (Example 1) has better performance and only requires the addition of 0.02 mol of Pr.

[0140] Comparative Example 5:

[0141] The chemical formula of the potassium ion battery cathode material prepared in this comparative example is K 0.5 MnO2 / MgAl2O4, the preparation method comprises the following steps:

[0142] S1. Weigh appropriate amounts of potassium carbonate, manganese trioxide, magnesium oxide, and aluminum oxide according to the molar ratio of K:Mn:Mg:Al = 0.5:1:0.02:0.04 and place them in a ball mill;

[0143] S2, adding ethanol twice the total mass of potassium carbonate, manganese trioxide, magnesium oxide, and aluminum oxide to the ball mill;

[0144] S3. Add alumina ball milling beads to a ball milling jar, and then perform ball milling to obtain a mixture; wherein the rotation speed of the ball milling jar is 300 r / min, the ball milling time is 1 hour, and the ball-to-material ratio is 1:1;

[0145] S4, placing the mixture in a drying oven at 60°C for drying, then placing it in a muffle furnace, heating it to 850°C at a heating rate of 5°C / min in an air atmosphere for heat treatment for 12 hours, and then cooling it to room temperature at a cooling rate of 2°C / min to obtain a heat-treated product;

[0146] S5. Grind the heat-treated product thoroughly, then pass it through a 300-mesh standard sieve, and vacuum-dry it at 120° C. for 6 h to obtain the potassium ion battery positive electrode material.

[0147] The experimental results show that the prepared cathode is a single-phase P3 layered structure, with no MgAl2O4 spinel phase observed. Therefore, a layered-spinel dual-phase cathode cannot be formed through a single sintering step, and the battery performance improvement is limited.

[0148] From the above comparative examples 1-5, it can be seen that under the process conditions of only one heat treatment, conventional metal oxides will be dissolved in the layered phase, showing doping modification, and cannot form a second phase at the crystal (phase) boundary, and the performance improvement of the layered positive electrode is limited.

[0149] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, for those of ordinary skill in the art, various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A layered-perovskite dual-phase potassium ion battery cathode material, characterized in that: The chemical formula of the positive electrode material is K 0.5 MnO2 / AMnO3, A=Pr, La or Gd; the positive electrode material is a two-phase composite structure of P phase and perovskite phase, wherein the P phase is layered grains with a diameter of 1-3 microns, and the perovskite phase is nanoparticles with a grain size of 100-300nm, which grow at the grain boundaries of the layered grains, forming a layered-perovskite two-phase structure.

2. The method for preparing the layered-perovskite dual-phase composite potassium ion battery positive electrode material according to claim 1, characterized in that: The following steps are involved: S1. Weigh potassium source, manganese source, and A source according to the molar ratio of K:Mn:A = 0.5:1:m, and place them in a ball mill, where m = 0.01-0.1; S2, adding ethanol to the ball milling tank and performing ball milling to obtain a mixture; S3, drying the mixture, and then heat-treating it at a temperature of 850-900° C. for 12-15 hours; then cooling it to room temperature to obtain a heat-treated product; S4. Grinding, sieving, and drying the heat-treated product in sequence to obtain the potassium ion battery positive electrode material.

3. The preparation method according to claim 2, characterized in that In step S1, the potassium source is potassium carbonate; the manganese source is manganese trioxide; and the A source is praseodymium undecoxide, lanthanum trioxide, or gadolinium trioxide.

4. The preparation method according to claim 2, characterized in that In step S2, during the ball milling treatment, the ball-to-material ratio is 1:1-2, the rotation speed of the ball mill is 250-300 r / min, and the ball milling time is 1-2 h.

5. The preparation method according to claim 2, characterized in that In step S2, the amount of ethanol added is 1-3 times the total mass of the potassium source, the manganese source, and the A source.

6. The preparation method according to claim 2, characterized in that In step S3, the heat treatment is performed in an air atmosphere, and the heating rate during the heat treatment is 3-5°C / min.

7. The preparation method according to claim 2, characterized in that In step S3, the cooling rate is 2-3°C / min.

8. The preparation method according to claim 2, characterized in that In step S4, the drying is performed under vacuum at 100-120° C. for 6-8 hours.

9. The preparation method according to claim 2, characterized in that In step S4, the dried heat-treated product is placed in a mortar, fully ground, and then passed through a 200-300 mesh standard sieve.

10. The use of the layered-perovskite dual-phase composite potassium ion battery positive electrode material according to claim 1 or 2, characterized in that: The positive electrode material is mixed with PVDF, conductive carbon black and NMP to prepare a potassium ion battery.

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