Method for stabilizing manganese-based potassium ion battery positive electrode material structure through multi-ion cooperation

Abstract

The invention discloses a method for synergistically stabilizing a manganese-based potassium ion battery positive electrode material structure through multiple ions, and belongs to the technical field of potassium ion battery positive electrode materials. The method comprises the following steps: weighing a potassium source, a manganese source, a source A, a source B, a source C, a source D and a source E, and putting into a ball milling tank; adding ethanol and carrying out ball milling to obtain a mixture; after drying, carrying out heat treatment at the temperature of 845-875 DEG C for 10-15 hours, cooling to room temperature, and grinding, drying and sieving a heat treatment product to obtain the manganese-based layered potassium ion battery positive electrode material with improved stability; wherein A and B are elements capable of forming strong metal-oxygen bonds with the bond energy larger than 500 kJ / mol, C and D are + 2 valence elements, and E is an ionic state with the radius close to that of manganese ions. According to the method provided by the invention, a special sintering atmosphere and an additional treatment process are not needed, ginger-Taylor distortion and structural evolution in the circulation process are effectively inhibited through the synergistic effect of various trace ions, and the prepared positive electrode material is low in cost and can realize excellent circulation and rate performance.

Description

Technical Field

[0001] The present invention relates to the technical field of potassium ion battery positive electrode materials, and in particular to a method for stabilizing the structure of a manganese-based potassium ion battery positive electrode material through multi-ion collaboration. Background Art

[0002] Since potassium and lithium have similar physical properties, potassium-ion batteries are considered to be possible substitutes for lithium-ion batteries. x MnO2, the most stable structure is x = 0.5) has a high reversible specific capacity and has therefore attracted widespread attention. This material is mainly composed of MnO6 octahedral layers and potassium ion layers. However, this material has poor cycle stability and rate performance. -1 The discharge capacity at this current density is only 38 mAh g -1 (Adv. Mater. 2017, 29, 1702480). The poor structural stability and rate performance of this material are key obstacles to the large-scale application of potassium-ion batteries.

[0003] Usually, K x One of the factors that cause the structural degradation of MnO2 series cathodes during cycling is the 3+ The first is the Jahn-Teller distortion caused by the first, and the second is the structural evolution during the cycle, such as the structural evolution of the transition metal layer caused by the change of the manganese valence state. This is because when there is asymmetric occupation of electrons in degenerate orbitals (orbitals with the same energy), the molecules or ions will undergo geometric distortion to reduce the system energy and eliminate the degeneracy. At this time, for Mn 3+ The axial Mn-O bonds will gradually stretch, resulting in axial elongation, which is usually manifested as an elongated Jahn-Teller distortion. The MnO6 formed at this time is an octahedron deformed by axial elongation, which is an unstable structure.

[0004] In this case, the structural stability of the manganese-based hierarchical structure cathode will deteriorate, and even transition metal ion dissolution will occur. In addition, manganese ions will participate in charge compensation during the cycle. When discharged to a lower potential, the average valence of manganese ions will decrease, further enhancing the Jahn-Taylor distortion and causing the transition metal layer to undergo structural evolution that affects the stability of the system. Therefore, the main purpose of modifying manganese-based hierarchical cathode materials is to adjust the valence of manganese ions to inhibit Jahn-Taylor distortion, further stabilize the transition metal layer during the cycle, and inhibit phase change during the cycle.

[0005] To improve the structural stability of the material, the current mainstream control method is to dope low-valent metal cations in the transition metal layer to partially replace the manganese ions. However, if the structural stability needs to be improved, the doping ions need to reach a higher concentration. Although the average valence of the manganese ions (Mn 3+content decreased), but for K 0.5 The improvement of the actual performance of MnO2 (cycle and rate performance of the positive electrode) is very limited. It may even be because the radius of the doped ions is smaller than that of manganese ions (Mn 3+ 0.64 angstroms, Mn 4+ When the doping concentration is high, a certain lattice distortion is introduced, which in turn leads to a decrease in structural stability.

[0006] For example, 0.1 mol of magnesium ions (Mg 2+ , ion radius is 0.73 angstroms) doping theoretically increases the average valence of manganese ions, but it causes the discharge curve of the material to have more platforms when discharged to low voltage conditions, resulting in poor structural stability of the material during the cycle; 0.1 mol zinc ions (Zn 2+ , ion radius is 0.74 angstroms) doping is also the case, and it does not significantly improve the cycle and rate performance of the material; 0.1 mol copper ions (Cu 2+ , ion radius is 0.73 angstroms) doping makes the charge and discharge platform of the material change significantly, but the cycle stability of the material also decreases after doping; 0.1 mol titanium ions (Ti 4+ Although the doping of 2-HgO2 (with an ionic radius of 0.605 angstroms) can significantly enhance the chemical bonding between metal and oxygen and stabilize the transition metal layer to a certain extent, it will also significantly enhance the Jahn-Teller distortion of the transition metal layer. Therefore, it is important to find a reasonable modification scheme for the transition metal layer to increase the K 0.5 The key to the performance of MnO2 positive electrode. Summary of the Invention

[0007] To address the aforementioned issues with existing technologies, the present invention provides a method for stabilizing the structure of manganese-based potassium-ion battery cathode materials through the synergistic action of multiple ions. This method, which requires no special sintering atmosphere or additional processing steps, effectively suppresses Jahn-Teller distortion and structural evolution during cycling through the synergistic action of multiple trace ions. The resulting cathode material is low-cost and achieves excellent cycle and rate performance.

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

[0009] The present invention first provides a method for synergistically stabilizing the structure of a manganese-based potassium ion battery cathode material using multiple ions. The method utilizes the synergistic effect of five low-concentration ions to stabilize the structure of a manganese-based potassium ion battery cathode material. The method specifically comprises the following steps:

[0010] S1. Weigh potassium source, manganese source, source A, source B, source C, source D, and source E and place them in a ball mill;

[0011] S2, adding ethanol to the ball milling tank and ball milling to obtain a mixture;

[0012] S3, drying the mixture and then heat-treating it at a temperature of 845-875° C. for 10-15 hours, and then cooling it to room temperature to obtain a heat-treated product;

[0013] S4, grinding, drying, and sieving the heat-treated product in sequence to obtain a manganese-based potassium ion battery positive electrode material with improved stability;

[0014] In step S1, A and B are elements that can form a strong metal-oxygen bond with a bond energy greater than 500 kJ / mol, C and D are +2 valence elements, and E has an ionic radius similar to that of a manganese ion, satisfying the following formula:

[0015]

[0016] Among them, r host is the radius of the manganese ion, r doped is the dopant ion radius.

[0017] Furthermore, the chemical formula of the manganese-based potassium ion battery positive electrode material is K 0.5 Mn 1-y A 1 / 5y B 1 / 5y C 1 / 5y D 1 / 5y E 1 / 5y O2, wherein 0.05≤y≤0.2; A and B are titanium and aluminum; C and D are any one of copper, magnesium and zinc respectively; and E is any one of iron, chromium and vanadium.

[0018] Preferably, in step S1, the potassium source, manganese source, source A, source B, source C, source D, and source E are weighed and placed in a ball mill according to the molar ratio of K:Mn:A:B:C:D:E=0.5:1-y:1 / 5y:1 / 5y:1 / 5y:1 / 5y:1 / 5y.

[0019] Preferably, in step S1, the potassium source is potassium carbonate; the manganese source is manganese trioxide; the A and B sources are titanium oxide and aluminum oxide; the C and D sources are respectively any one of zinc oxide, copper oxide, and magnesium oxide; and the E source is any one of iron oxide, chromium oxide, and vanadium oxide.

[0020] Preferably, in step S2, during the ball milling treatment, the rotation speed of the ball mill is 250-300 r / min, the ball milling time is 1-2 h, and the ball-to-material ratio is 1:1-2.

[0021] Furthermore, in step S2, the ball milling beads used are alumina ball milling beads.

[0022] Preferably, in step S2, the amount of ethanol added is 2-3 times the total mass of the potassium source, manganese source, source A, source B, source C, source D, and source E.

[0023] Preferably, in step S3, the atmosphere of the heat treatment is an air atmosphere, the heating rate during the heat treatment is 3-5°C / min, and the cooling rate during the cooling is 2-3°C / min.

[0024] Preferably, in step S4, the drying condition is vacuum drying at 100-120° C. for 6-8 hours.

[0025] Preferably, in step S4, the product is sieved through a 200-300 mesh sieve.

[0026] Furthermore, in step S4, the obtained sample is fully ground in an agate mortar.

[0027] The present invention also provides a method for preparing a manganese-based layered potassium ion battery positive electrode material, which is prepared using the method described above.

[0028] In the above method, first, A and B can form a strong metal ion-oxygen bond. For example, AlO6 and TiO6 octahedra formed by doping with titanium and aluminum ions are pinning sites with extremely high stability. Aluminum ions can also inhibit the deformation of MnO6 caused by Jahn-Taylor distortion and inhibit the structural evolution of MnO6 due to valence changes during the cycle. Aluminum ions can also play a role in increasing the average valence of manganese ions. The introduction of two functional ions can increase the occupancy disorder in the lattice and avoid lattice distortion caused by excessive doping.

[0029] Secondly, the average valence of manganese ions can be increased by introducing low-valent elements. For example, zinc, copper or magnesium ions can be used to increase the average valence of manganese ions to further suppress the Jahn-Teller distortion. The introduction of two such functional ions can increase the occupancy disorder in the lattice and avoid lattice distortion caused by excessive doping.

[0030] Third, introduce ions with a high lattice match to manganese ions. For example, by doping with iron ions (0.645 angstroms), which have a radius similar to that of manganese ions, further dilute the local manganese ion concentration, increase the occupancy disorder in the lattice, avoid lattice distortion, and increase the average valence of the manganese ions. Because the primary function is dilution, only one type is introduced. When the total number of dopant ions is five, it is easier to balance the proportions of the various dopant ions.

[0031] The synergistic effect of the five doping ions mentioned above suppresses Jahn-Teller distortion and enhances structural stability by both inhibiting structural distortion and increasing the average valence of manganese ions. This approach avoids the introduction of new lattice distortion caused by excessive concentration of a single doping ion or a large difference in radius between the ion and the manganese ion, significantly improving the electrochemical performance of the manganese-based layered cathode.

[0032] All doping ions are in equal proportions, and when the potassium ion content is 0.5 mol, the doping amount of each ion does not exceed 0.04 mol. This design utilizes the octahedral coordination structure between MO to form a transition metal layer, with potassium ions interspersed between the layers to form a potassium ion layer, resulting in a low-cost manganese-based layered cathode material.

[0033] Among the above raw materials, potassium carbonate is cheap and easy to obtain; metal oxide powder is used as the manganese source, A source, B source, C source, D source, and E source, and the raw materials are easy to obtain.

[0034] The beneficial technical effects of the present invention are:

[0035] 1. The present invention achieves the regulation of the Jan-Taylor distortion of the manganese-based potassium ion battery cathode material by the synergistic doping of five low-concentration ions and the synergistic effect of the five ions. The principle is as follows: first, by doping low concentrations of aluminum, titanium and other metal ions in the transition metal layer, a certain concentration of rigid sites (such as rigid metal ion-oxygen octahedron (MO6) structure, which is an octahedral structure with strong metal-oxygen bonds) is introduced, forming a pinning effect in the transition metal layer to limit the structural distortion of MnO6 and its structural evolution during the cycle; secondly, a variety of low-concentration low-valent transition metals and metals with radii similar to Mn ions (zinc, copper, iron ions, etc.) are introduced to increase the average valence of manganese ions, and finally form a multi-ion synergistic effect to more comprehensively suppress the Jan-Taylor distortion.

[0036] 2. The doping ion concentrations of the present invention are low and the proportions are equal, which can achieve uniform distribution of metal cations in the material lattice and effectively avoid the negative effects of excessive metal cation doping, such as avoiding the introduction of new distortions in the transition metal layer due to excessive concentration of a single ion. Finally, the general formula K 0.5 Mn 1-y A 1 / 5y B 1 / 5y C 1 / 5y D 1 / 5y E 1 / 5y O2, 0.05≤y≤0.2, a novel potassium ion battery cathode material. This invention, for the first time, employs five low-concentration ion doping methods to synergistically suppress the Jahn-Teller distortion in manganese-based hierarchical cathodes by suppressing the structural distortion of MnO6, which is affected by Jahn-Teller distortion, and increasing the average valence of manganese ions. This significantly improves the cycling stability and rate performance of the cathode material.

[0037] 3. The layered cathode material in the method of the present invention can be formed through a single heat treatment process without the need for a complex preparation process. Due to the low doping concentration of each ion, all ions can be perfectly dissolved in the crystal lattice of the layered cathode and are evenly distributed. No other lattice distortion or impurity phase formation will be introduced due to the local enrichment of dopant ions in the crystal lattice. The potassium ion battery cathode material prepared by this method is a low-cost battery material that does not contain expensive elements such as nickel, cobalt, and manganese. It has the characteristics of readily available raw materials, low cost, and easy preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The XRD diffraction pattern of the potassium ion battery positive electrode material prepared in Example 1;

[0039] Figure 2 This is a transmission electron micrograph of the potassium ion battery positive electrode material prepared in Example 1;

[0040] Figure 3 This is a graph showing the cycle performance test results of the potassium ion battery positive electrode material prepared in Example 1;

[0041] Figure 4 This is a graph showing the rate performance test results of the potassium ion battery positive electrode material prepared in Example 1;

[0042] Figure 5 This is a graph showing the Mn-2p XPS test results of the potassium ion battery positive electrode material prepared in Example 1;

[0043] Figure 6 The XRD diffraction pattern of the potassium ion battery positive electrode material prepared in Example 4;

[0044] Figure 7 This is a transmission electron micrograph of the potassium ion battery cathode material prepared in Example 4;

[0045] Figure 8 This is a graph showing the cycle performance test results of the potassium ion battery positive electrode material prepared in Comparative Example 4;

[0046] Figure 9 This is a graph showing the rate performance test results of the potassium ion battery positive electrode material prepared in Comparative Example 4;

[0047] Figure 10 This is a graph showing the Mn-2p XPS test results of the potassium ion battery cathode material prepared in Example 4;

[0048] Figure 11 This is the Mn-2p XPS test result diagram of the potassium ion battery positive electrode material prepared in Comparative Example 1. DETAILED DESCRIPTION

[0049] 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.

[0050] Example 1:

[0051] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 Mn 0.9 Ti 0.02 Al 0.02 Fe 0.02 Cu 0.02 Zn 0.02 O2, the preparation method comprises the following steps:

[0052] S1. Weigh potassium source, manganese source, titanium source, iron source, copper source, zinc source, and aluminum source in a molar ratio of K:Mn:Al:Fe:Cu:Ti:Zn=0.5:0.9:0.02:0.02:0.02:0.02:0.02 and place them in a ball mill;

[0053] S2. Add ethanol twice the total mass of potassium carbonate, manganese trioxide, aluminum oxide, iron oxide, copper oxide, zinc oxide, and titanium oxide to the ball mill;

[0054] 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;

[0055] 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;

[0056] S5, the obtained product is fully ground, sieved through a 300 mesh sieve, and then vacuum dried at 120 ° C for 6 hours to obtain the potassium ion battery positive electrode material K 0.5 Mn 0.9 Ti 0.02 Al 0.02 Fe 0.02 Cu 0.02 Zn 0.02 O2.

[0057] The potassium ion battery cathode material K prepared in this embodiment 0.5 Mn 0.9 Ti 0.02 Al 0.02 Fe0.02 Cu 0.02 Zn 0.02 The XRD diffraction pattern of O2 is as follows Figure 1 As shown by Figure 1 It can be seen that the positive electrode material of the ion battery is P phase (R3m). The transmission electron microscope image of the potassium ion positive electrode material is as follows Figure 2 As shown, from Figure 2 It can be observed that the prepared material is layered grains with a diameter of 1-3 microns, and the scale bar in the figure is 1 micron.

[0058] The potassium ion battery cathode material K prepared in this example 0.5 Mn 0.9 Ti 0.02 Al 0.02 Fe 0.02 Cu 0.02 Zn 0.0 2O2 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 and dried to obtain the battery positive electrode sheet, which was then assembled into a 2032 button battery and tested.

[0059] The cycle performance test results and rate performance test results of potassium ion battery positive electrode materials are shown in the figure below. Figure 3 and Figure 4 As shown. Figure 3 and Figure 4 It can be seen that the first cycle discharge capacity of the potassium ion battery cathode material prepared in this embodiment reaches 100 mAh g -1 About (10mA·g -1 ), at 20 mA g -1 The capacity retention rate is as high as 81% after 30 cycles under the conditions of 300mA·g -1 Under the condition of current density, there is still 45mAh·g -1 The capacity is much higher than the 38 mAh g of pure KMO reported in the literature. -1 Around (Adv.Mater.2017,29,1702480).

[0060] In comparison, the first cycle discharge capacity of the potassium ion battery cathode material prepared by the traditional solid phase method in Comparative Example 1 is 90 mAh g -1 However, after 30 cycles, the capacity retention rate is only 70%, 300mA·g -1 The current density is only 37 mAh g -1 Obviously, the layered cathode has better cycle and rate performance, indicating that the structural stability of the cathode material has been significantly improved and the performance has been significantly improved.

[0061] The Mn-2p XPS analysis results of the positive electrode prepared in this example are as follows Figure 5 As shown. Figure 5 It can be seen that the average valence of manganese ions is 3.57, which is higher than Figure 11 The Mn-2p XPS analysis result (3.52) of Comparative Example 1 shown indicates that the Jahn-Teller distortion is significantly suppressed.

[0062] Example 2:

[0063] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 Mn 0.95 Ti 0.01 Al 0.01 Fe 0.01 Cu 0.01 Zn 0.01 O2, the preparation method comprises the following steps:

[0064] S1. Weigh potassium source, manganese source, titanium source, iron source, copper source, zinc source, and aluminum source in a molar ratio of K:Mn:Al:Fe:Cu:Ti:Zn=0.5:0.95:0.01:0.01:0.01:0.01 and place them in a ball mill;

[0065] S2. Add 2.5 times the total mass of potassium carbonate, manganese trioxide, aluminum oxide, iron oxide, copper oxide, zinc oxide, and titanium oxide into the ball mill;

[0066] 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 1.5 h, and the ball-to-material ratio is 1:2;

[0067] S4, placing the mixture in a drying oven at 60°C for drying, then placing it in a muffle furnace, heating it to 845°C at a heating rate of 3°C / min in an air atmosphere for heat treatment for 10 hours, and then cooling it to room temperature at a cooling rate of 2°C / min to obtain a heat-treated product;

[0068] S5, the obtained product is fully ground, sieved through a 200 mesh sieve, and then vacuum dried at 100 ° C for 8 hours to obtain the potassium ion battery positive electrode material K 0.5 Mn 0.95 Ti 0.01 Al 0.01 Fe 0.01 Cu 0.01 Zn 0.01 O2.

[0069] The battery positive electrode material prepared in this example is P phase (R3m), and its basic lattice structure and material size are the same as those in Example 1. The first cycle discharge capacity of this potassium ion battery positive electrode material is about 100 mAh·g -1 The cycle and rate performance, capacitance and other performances are similar to those in Example 1.

[0070] Example 3:

[0071] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 Mn 0.85 Ti 0.03 Al 0.03 Fe 0.03 Cu 0.03 Zn 0.03 O2, the preparation method comprises the following steps:

[0072] S1. Weigh potassium source, manganese source, titanium source, iron source, copper source, zinc source, and aluminum source in a molar ratio of K:Mn:Al:Fe:Cu:Ti:Zn=0.5:0.85:0.03:0.03:0.03:0.03:0.03 and place them in a ball mill;

[0073] S2. Add ethanol three times the total mass of potassium carbonate, manganese trioxide, aluminum oxide, iron oxide, copper oxide, zinc oxide, and titanium oxide to the ball mill;

[0074] 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 2 h, and the ball-to-material ratio is 1:1.2;

[0075] 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 4°C / min in an air atmosphere for heat treatment for 14 hours, and then cooling it to room temperature at a cooling rate of 3°C / min to obtain a heat-treated product;

[0076] S5, the heat-treated product was fully ground, then passed through a 300-mesh standard sieve, and then vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K 0.5 Mn 0.85 Ti 0.03 Al 0.03 Fe 0.03 Cu 0.03 Zn 0.03 O2.

[0077] The battery positive electrode material prepared in this example is P phase (R3m), and its basic lattice structure and material size are the same as those in Example 1. The first cycle discharge capacity of this potassium ion battery positive electrode material is about 100 mAh·g -1The cycle and rate performance, capacitance and other performances are similar to those in Example 1.

[0078] Example 4:

[0079] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 Mn 0.8 Ti 0.04 Al 0.04 Fe 0.04 Cu 0.04 Zn 0.04 O2, the preparation method comprises the following steps:

[0080] S1. Weigh potassium source, manganese source, titanium source, iron source, copper source, zinc source, and aluminum source in a molar ratio of K:Mn:Al:Fe:Cu:Ti:Zn=0.5:0.8:0.04:0.04:0.04:0.04:0.04 and place them in a ball mill;

[0081] S2. Add ethanol twice the total mass of potassium carbonate, manganese trioxide, aluminum oxide, iron oxide, copper oxide, zinc oxide, and titanium oxide to the ball mill;

[0082] 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;

[0083] 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;

[0084] S5, the heat-treated product was fully ground, then passed through a 300-mesh standard sieve, and then vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K 0.5 Mn 0.8 Ti 0.04 Al 0.04 Fe 0.04 Cu 0.04 Zn 0.04 O2.

[0085] The potassium ion battery cathode material K prepared in this embodiment 0.5 Mn 0.8 Ti 0.04 Al 0.04 Fe 0.04 Cu 0.04 Zn 0.04 The XRD diffraction pattern of O2 is as follows Figure 6 As shown by Figure 6It can be seen that the positive electrode material of the ion battery is P phase (R3m). The transmission electron microscope image of the potassium ion positive electrode material is as follows Figure 7 As shown, from Figure 7 It can be observed that the prepared material is a layered grain with a diameter of 1-3 microns, and the scale bar in the figure is 200 nm.

[0086] The potassium ion battery cathode material K prepared in this example 0.5 Mn 0.8 Ti 0.04 Al 0.04 Fe 0.04 Cu 0.04 Zn 0.0 4O2 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 positive electrode of the battery was obtained, which was then assembled into a 2032 button battery and tested.

[0087] The cycle performance test results and rate performance test results of potassium ion battery positive electrode materials are shown in the figure below. Figure 8 and Figure 9 As shown. Figure 8 and Figure 9 It can be seen that the first cycle discharge capacity of the potassium ion battery cathode material prepared in this embodiment reaches 100 mAh g -1 About (10mA·g -1 ), at 20 mA g -1 The capacity retention rate is as high as 88% after 30 cycles under the conditions of 300mA·g -1 Under the condition of current density, it still has 56.4 mAh·g -1 The capacity of the CMOS image sensor indicates that the Chiang-Taylor distortion is effectively suppressed.

[0088] The Mn-2p XPS analysis results of the positive electrode prepared in this example are as follows Figure 10 As shown. Figure 10 It can be seen that the average valence of manganese ions is 3.61, which is higher than Figure 11 The Mn-2p XPS analysis result (3.52) of Comparative Example 1 shown above indicates that the average valence of manganese ions is increased and the Jahn-Taylor distortion is significantly suppressed.

[0089] Example 5:

[0090] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 Mn 0.8 Ti 0.04 Al 0.04 Fe 0.04 Mg 0.04 Zn 0.04O2, the preparation method comprises the following steps:

[0091] S1. Weigh potassium source, manganese source, titanium source, iron source, magnesium source, zinc source, and aluminum source in a molar ratio of K:Mn:Al:Fe:Mg:Ti:Zn=0.5:0.8:0.04:0.04:0.04:0.04:0.04 and place them in a ball mill;

[0092] S2. Add ethanol twice the total mass of potassium carbonate, manganese trioxide, aluminum oxide, iron oxide, copper oxide, zinc oxide, and titanium oxide to the ball mill;

[0093] 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;

[0094] 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;

[0095] S5, the heat-treated product was fully ground, then passed through a 300-mesh standard sieve, and then vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K 0.5 Mn 0.8 Ti 0.04 Al 0.04 Fe 0.04 Mg 0.04 Zn 0.04 O2.

[0096] The battery positive electrode material prepared in this example is P phase (R3m), and its basic lattice structure and material size are the same as those in Example 1. The first cycle discharge capacity of this potassium ion battery positive electrode material is about 100 mAh·g -1 The cycle and rate performance, capacitance and other performances are similar to those of Example 4.

[0097] Comparative Example 1:

[0098] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 MnO2, the preparation method comprises the following steps:

[0099] S1. Weigh potassium carbonate and manganese trioxide in a molar ratio of K:Mn = 0.5:1 and place them in a ball mill;

[0100] S2, adding potassium carbonate and ethanol twice the total mass of manganese trioxide to the ball mill;

[0101] 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;

[0102] 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;

[0103] S5, the heat-treated product is fully ground, then passed through a 300-mesh standard sieve, and then vacuum-dried at 120° C. for 6 h; the potassium ion battery positive electrode material K is obtained. 0.5 MnO2.

[0104] The Mn-2p XPS analysis results of the positive electrode prepared in this comparative example are as follows Figure 11 As shown. Figure 11 It can be seen that the average valence of manganese ions is 3.52, which is relatively low, and the Jahn-Taylor distortion is not significantly suppressed. 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.

[0105] The potassium ion battery cathode material prepared in this comparative example has a capacity of 90 mAh·g -1 The discharge specific capacity is about 1000 nm, and the capacity retention rate after 30 cycles is only 73%, which shows poor battery performance compared with Example 4, indicating that the synergistic effect of multiple ions can better improve the positive electrode performance.

[0106] Comparative Example 2:

[0107] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 Mn 0.9 Mg 0.1 O2, the preparation method comprises the following steps:

[0108] S1. Weigh potassium carbonate, manganese trioxide, and magnesium oxide in a molar ratio of K:Mn:Mg = 0.5:0.9:0.1 and place them in a ball mill;

[0109] S2, adding ethanol twice the total mass of potassium carbonate, manganese trioxide, and magnesium oxide to the ball mill;

[0110] 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;

[0111] 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;

[0112] S5, the heat-treated product is fully ground, then passed through a 300-mesh standard sieve, and then vacuum-dried at 120° C. for 6 h; the potassium ion battery positive electrode material K is obtained. 0.5 Mn 0.9 Mg 0.1 O2.

[0113] 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.

[0114] The potassium ion battery cathode material prepared in this comparative example has a capacity of 100 mAh·g -1 The discharge specific capacity is about 200 nm, but the capacity retention rate after 30 cycles is only 72%, which shows poor battery performance compared with Example 4, indicating that the synergistic effect of multiple ions better improves the positive electrode performance.

[0115] Comparative Example 3:

[0116] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 Mn 0.9 Cu 0.1 O2, the preparation method comprises the following steps:

[0117] S1. Weigh potassium carbonate, manganese trioxide, and copper oxide in a molar ratio of K:Mn:Cu = 0.5:0.9:0.1 and place them in a ball mill;

[0118] S2, adding potassium carbonate, manganese trioxide, and ethanol twice the total mass of copper oxide to the ball mill;

[0119] 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;

[0120] 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;

[0121] S5, the heat-treated product is fully ground, then passed through a 300-mesh standard sieve, and then vacuum-dried at 120° C. for 6 h; the potassium ion battery positive electrode material K is obtained. 0.5 Mn 0.9 Cu 0.1 O2.

[0122] 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.

[0123] The potassium ion battery cathode material prepared in this comparative example has a capacity of 90 mAh·g -1 The discharge specific capacity is about 1000 nm, and the capacity retention rate after 30 cycles is only 74%, which shows poor battery performance compared with Example 4, indicating that the synergistic effect of multiple ions better improves the positive electrode performance.

[0124] Comparative Example 4:

[0125] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 Mn 0.9 Mg 0.2 O2, the preparation method comprises the following steps:

[0126] S1. Weigh potassium carbonate, manganese trioxide, and magnesium oxide in a molar ratio of K:Mn:Mg = 0.5:0.8:0.2 and place them in a ball mill;

[0127] S2, adding ethanol twice the total mass of potassium carbonate, manganese trioxide, and magnesium oxide to the ball mill;

[0128] 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;

[0129] 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;

[0130] S5, the heat-treated product is fully ground, then passed through a 300-mesh standard sieve, and then vacuum-dried at 120° C. for 6 h; the potassium ion battery positive electrode material K is obtained. 0.5 Mn 0.8 Mg 0.2 O2.

[0131] The potassium ion battery positive electrode material K prepared in this comparative example 0.5 Mn 0.8 Mg 0.2 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.

[0132] The potassium ion battery cathode material prepared in this comparative example has a capacity of 100 mAh·g -1 The discharge specific capacity is about 1000 nm, and the capacity retention rate after 30 cycles is only 50%, which shows poor battery performance compared with Example 4, indicating that the synergistic effect of multiple ions better improves the positive electrode performance.

[0133] Comparative Example 5:

[0134] The chemical formula of the potassium ion battery cathode material prepared in this embodiment is K 0.5 Mn 0.8 Cu 0.2 O2, the preparation method comprises the following steps:

[0135] S1. Weigh potassium carbonate, manganese trioxide, and magnesium oxide in a molar ratio of K:Mn:Cu = 0.5:0.8:0.2 and place them in a ball mill;

[0136] S2, adding ethanol twice the total mass of potassium carbonate, manganese trioxide, and magnesium oxide to the ball mill;

[0137] 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;

[0138] 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;

[0139] S5, the heat-treated product is fully ground, then passed through a 300-mesh standard sieve, and then vacuum-dried at 120° C. for 6 h; the potassium ion battery positive electrode material K is obtained. 0.5 Mn0.8 Cu 0.2 O2.

[0140] The potassium ion battery positive electrode material K prepared in this comparative example 0.5 Mn 0.8 Cu 0.2 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.

[0141] The potassium ion battery cathode prepared in this comparative example has a capacity of 80 mAh·g -1 The discharge specific capacity is about 200 nm, and the capacity retention rate of the material after 30 cycles is only 52%, which shows poor battery performance compared with Example 4, indicating that the synergistic effect of multiple ions better improves the positive electrode performance.

[0142] Comparative Example 6:

[0143] The chemical formula of the potassium ion battery cathode material prepared in this comparative example is K 0.5 Mn 0.8 Ni 0.04 Al 0.04 Fe 0.04 Cu 0.04 Zn 0.04 O2, the preparation method comprises the following steps:

[0144] S1. Weigh potassium source, manganese source, nickel source, iron source, copper source, zinc source, and aluminum source in a molar ratio of K:Mn:Al:Fe:Cu:Ni:Zn=0.5:0.8:0.04:0.04:0.04:0.04:0.04 and place them in a ball mill;

[0145] S2. Add ethanol twice the total mass of potassium carbonate, manganese trioxide, nickel oxide, iron oxide, copper oxide, zinc oxide, and aluminum oxide to the ball mill;

[0146] 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;

[0147] 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;

[0148] S5, the heat-treated product was fully ground, then passed through a 300-mesh standard sieve, and then vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K0.5 Mn 0.8 Ni 0.04 Al 0.04 Fe 0.04 Cu 0.04 Zn 0.04 O2.

[0149] The potassium ion battery cathode material prepared in this comparative example has a capacity of 100 mAh·g -1 The discharge specific capacity is about 1000 nm, and the capacity retention rate after 30 cycles is only 70%, showing poor battery performance compared with Example 4. After replacing titanium with nickel, the Ni-O bond energy is lower than that of Ti-O, and the transition metal layer structure cannot be well stabilized, indicating that the multi-ion synergy of Example 4 better improves the positive electrode performance.

[0150] Comparative Example 7:

[0151] The chemical formula of the potassium ion battery cathode material prepared in this comparative example is K 0.5 Mn 0.8 Ti 0.04 Al 0.04 Sc 0.04 Cu 0.04 Zn 0.04 O2, the preparation method comprises the following steps:

[0152] S1. Weigh potassium source, manganese source, titanium source, scandium source, copper source, zinc source, and aluminum source according to the molar ratio of K:Mn:Al:Sc:Cu:Ti:Zn=0.5:0.8:0.04:0.04:0.04:0.04:0.04 and place them in a ball mill;

[0153] S2. Add ethanol twice the total mass of potassium carbonate, manganese trioxide, titanium oxide, iron oxide, copper oxide, scandium oxide, and aluminum oxide to the ball mill;

[0154] 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;

[0155] 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;

[0156] S5, the heat-treated product was fully ground, then passed through a 300-mesh standard sieve, and then vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K 0.5 Mn 0.8 Ti 0.04 Al0.04 Sc 0.04 Cu 0.04 Zn 0.04 O2.

[0157] The potassium ion battery cathode material prepared in this comparative example has a capacity of 100 mAh·g -1 The discharge specific capacity is about 100 nm, and the capacity retention rate after 30 cycles is only 65%, which shows poor battery performance compared with Example 4. After iron is replaced by scandium, since the scandium ion radius is much larger than that of manganese, more cations with large ion radius are introduced into the transition metal layer, making it impossible for the five-element design to stabilize the transition metal layer structure well, indicating that the multi-ion synergistic effect of Example 4 better improves the positive electrode performance.

[0158] Comparative Example 8:

[0159] The chemical formula of the potassium ion battery cathode material prepared in this comparative example is K 0.5 Mn 0.8 Ti 0.04 Al 0.04 Fe 0.04 Cu 0.04 Sb 0.04 O2, the preparation method comprises the following steps:

[0160] S1. Weigh potassium source, manganese source, titanium source, iron source, copper source, antimony source, and aluminum source in a molar ratio of K:Mn:Al:Fe:Cu:Ti:Sb=0.5:0.8:0.04:0.04:0.04:0.04:0.04 and place them in a ball mill;

[0161] S2. Add ethanol twice the total mass of potassium carbonate, manganese trioxide, nickel oxide, iron oxide, copper oxide, antimony oxide, and aluminum oxide to the ball mill;

[0162] 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;

[0163] 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;

[0164] S5, the heat-treated product was fully ground, then passed through a 300-mesh standard sieve, and then vacuum-dried at 120° C. for 6 h to obtain the potassium ion battery positive electrode material K 0.5 Mn 0.8 Ni 0.04 Al 0.04 Fe0.04 Cu 0.04 Sb 0.04 O2.

[0165] The potassium ion battery cathode material prepared in this comparative example has a capacity of 100 mAh·g -1 The discharge specific capacity is about 1000 nm, and the capacity retention rate after 30 cycles is only 69%, which shows poor battery performance compared with Example 4. After zinc is replaced by antimony, the valence of antimony ions is much higher than that of manganese, resulting in an average valence of manganese lower than that in Example 4, and the Jiang-Taylor distortion is stronger, making it impossible for the five-element design to stabilize the transition metal layer structure well, indicating that the multi-ion synergistic effect of the embodiment 4 scheme better improves the positive electrode performance.

[0166] 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 method for synergistically stabilizing the structure of a manganese-based potassium ion battery cathode material by multiple ions, characterized in that: The method utilizes the synergistic effect of five low-concentration ions to stabilize the structure of a manganese-based layered potassium ion battery cathode material, comprising the following steps: S1. Weigh potassium source, manganese source, source A, source B, source C, source D, and source E and place them in a ball mill; S2, adding ethanol to the ball milling tank and ball milling to obtain a mixture; S3, drying the mixture and then heat-treating it at a temperature of 845-875° C. for 10-15 hours, and then cooling it to room temperature to obtain a heat-treated product; S4, grinding, drying, and sieving the heat-treated product in sequence to obtain a manganese-based potassium ion battery positive electrode material with improved stability; In step S1, A and B are elements that can form a strong metal-oxygen bond with a bond energy greater than 500 kJ / mol, C and D are +2 valence elements, and E has an ionic radius similar to that of a manganese ion, satisfying the following formula: Among them, r host is the radius of the manganese ion, r doped is the dopant ion radius.

2. The method according to claim 1, characterized in that The chemical formula of the manganese-based potassium ion battery positive electrode material is K 0.5 Mn 1-y A 1 / 5y B 1 / 5y C 1 / 5y D 1 / 5y E 1 / 5y O2, wherein 0.05≤y≤0.2; A and B are titanium and aluminum; C and D are any one of copper, magnesium and zinc respectively; and E is any one of iron, chromium and vanadium.

3. The method according to claim 2, characterized in that In step S1, potassium source, manganese source, source A, source B, source C, source D, and source E are weighed and placed in a ball mill according to the molar ratio of K:Mn:A:B:C:D:E=0.5:1-y:1 / 5y:1 / 5y:1 / 5y:1 / 5y:1 / 5y.

4. The method according to claim 3, characterized in that In step S1, the potassium source is potassium carbonate; the manganese source is manganese trioxide; the A and B sources are titanium oxide and aluminum oxide; the C and D sources are any one of zinc oxide, copper oxide, and magnesium oxide respectively; and the E source is any one of iron oxide, chromium oxide, and vanadium oxide.

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

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

7. The method according to claim 1, characterized in that In step S3, the atmosphere of the heat treatment is air atmosphere, the heating rate during the heat treatment is 3-5°C / min; and the cooling rate of the cooling is 2-3°C / min.

8. The method according to claim 1, characterized in that In step S4, the drying condition is vacuum drying at 100-120° C. for 6-8 hours.

9. The method according to claim 1, characterized in that In step S4, the product is sieved through a 200-300 mesh sieve.

10. A method for preparing a manganese-based layered potassium ion battery positive electrode material, characterized in that: The method according to any one of claims 1 to 9 is used for preparation.

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