Positive electrode material, and preparation method therefor and use thereof

Abstract

The present application relates to the technical field of positive electrode materials, and in particular to a positive electrode material, and a preparation method therefor and a use thereof. The molecular formula of the positive electrode material is K0.5MnxMgyOzF2-z, wherein x is greater than 0 and less than 1.0, y is greater than 0 and less than 1.0, z is greater than 0 and less than 2, and x+y=1. Substitution of O2- with F- can expand the interlayer spacing of K0.5MnO2(KMO) and inhibit release of lattice O, and this change facilitates rapid transformation of K+ ions without causing substantial damage to the structure. In addition, by increasing the average valence state of manganese, introduction of Mg2+ and F- ions can effectively inhibit Jahn-Teller distortion. The cation and anion doping method enables the reversible capacity of the KMMOF cathode to reach up to about 110 mAhg-1 (at a current of 100 mAg-1), and a prepared potassium-ion battery has good cycle performance and rate capability.

Description

A positive electrode material and a preparation method and application thereof TECHNICAL FIELD

[0001] The present application belongs to the technical field of positive electrode materials, and particularly relates to a positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries are widely used due to their high energy, high power density and long cycle life. However, the limited nature and uneven distribution of lithium resources in the earth crust inevitably increase the manufacturing cost of lithium batteries, especially in the commercial application of smart grids. In order to solve this problem, sodium ion batteries (NIB) and potassium ion batteries (KIB) have become two promising alternatives, not only because they have abundant reserves of raw materials, but also because they have the same intercalation chemical structure as lithium ion batteries, which helps to design and synthesize electrode materials applied to sodium ion batteries and potassium ion batteries. Compared with sodium ion batteries, potassium ion batteries have a lower standard redox potential (K / K + , -2.936 V relative to the standard hydrogen electrode), which can be converted into a higher working voltage to obtain a higher energy density and has good application potential.

[0003] Layered transition metal oxides have high theoretical energy density and high lithium and sodium diffusion rate, and are widely used as positive electrode materials for lithium ion battery packs and sodium ion battery packs. At present, although P3-type layered transition metal oxides as KIB positive electrode materials have good structural integrity and low diffusion barrier, they exhibit good cycle stability and high rate capability, but after extracting a certain amount of K + , it will cause serious irreversible phase transition and Jahn-Teller distortion, and the lattice O will be released seriously, resulting in serious structure contraction, the interlayer distance decreases, K + diffusion dynamics decreases, and finally leads to the decline of cycle performance and rate capability.

[0004] Therefore, it is urgent to provide a positive electrode material, and a potassium ion battery prepared from the positive electrode material has good cycle performance and rate capability.

[0005] SUMMARY

[0006] The present application aims to solve one or more technical problems in the prior art described above, and at least provide a beneficial alternative or create conditions. Specifically, the present application provides a positive electrode material, and a potassium ion battery prepared from the positive electrode material has good cycle performance and rate capability.

[0007] The inventive concept of the present application: the molecular formula of the positive electrode material of the present application is K 0.5 Mn x Mg y O zF 2-z (KMMOF), wherein 0 < x < 1.0, 0 < y < 1.0, 0 < z < 2, and x + y = 1. The present application adopts F - instead of O 2- The K 0.5 MnO2(KMO) interlayer spacing can be expanded, and the release of lattice O is inhibited. Such changes are conducive to the rapid conversion of K + ions without causing substantial damage to the structure. In addition, the present application can effectively inhibit Jahn-Teller distortion by increasing the average valence of manganese and introducing Mg 2+ and F - ions. This cation and anion doping method can make the reversible capacity of the KMMOF cathode as high as about 110 mAh g -1 (current is 100 mAg -1 ), and when applied to a potassium ion battery, the potassium ion battery has good cycle performance and rate capability.

[0008] Therefore, the first aspect of the present application provides a positive electrode material.

[0009] Specifically, the molecular formula of the positive electrode material is K 0.5 Mn x Mg y O z F 2-z ; wherein 0 < x < 1.0, 0 < y < 1.0, 0 < z < 2, and x + y = 1.

[0010] Preferably, in the K 0.5 Mn x Mg y O z F 2-z , 0.6 < x < 0.8, 0.2 < y < 0.4, 0 < z < 2, and x + y = 1.

[0011] Preferably, the positive electrode material is spherical.

[0012] Preferably, the particle size of the positive electrode material is 0.9-2.2 μm; further preferably, the particle size of the positive electrode material is 1-2 μm.

[0013] Specifically, the positive electrode material is a layered oxide.

[0014] The second aspect of the present application provides a preparation method of the positive electrode material of the first aspect of the present application.

[0015] Specifically, the preparation method of the positive electrode material comprises the following steps:

[0016] The manganese-containing precursor, the magnesium-containing compound, the potassium-containing compound and the fluorine salt are mixed and calcined to obtain the cathode material.

[0017] Preferably, the manganese-containing precursor comprises at least one of MnCO3, Mn2O3, manganese acetate and manganese oxalate.

[0018] Further preferably, the manganese-containing precursor comprises Mn2O3.

[0019] Preferably, the magnesium-containing compound comprises at least one of MgO and Mg(OH)2.

[0020] Further preferably, the magnesium-containing compound comprises MgO.

[0021] Preferably, the potassium-containing compound comprises at least one of K2CO3, KOH and potassium oxalate.

[0022] Further preferably, the potassium-containing compound comprises K2CO3.

[0023] Preferably, the fluorine salt comprises at least one of NH4F and KF.

[0024] Further preferably, the fluorine salt comprises NH4F.

[0025] Preferably, the mixing is followed by grinding and then the calcination.

[0026] Specifically, the grinding can make the various substances mix sufficiently and the particle size of the components as small as possible, so that the substances can react uniformly and sufficiently during the calcination, and the chemical structure of the obtained cathode material is more stable and the performance of the material is better.

[0027] Preferably, the calcination temperature is 500-1000℃ and the calcination time is 1-8h.

[0028] Further preferably, the calcination temperature is 600-900℃ and the calcination time is 2-5h.

[0029] More preferably, the calcination temperature is 600℃ and the calcination time is 2h.

[0030] Preferably, the heating rate of the calcination is 3-6℃ / min; further preferably, the heating rate of the calcination is 4-5℃ / min; more preferably, the heating rate of the calcination is 5℃ / min.

[0031] Specifically, in order to obtain the positive electrode material with the expected chemical structure by calcining the multiple components, the calcination conditions need to be controlled to achieve a better calcination effect. For example, the temperature of calcination can be selected as 550℃, 560℃, 570℃, 580℃, 590℃, 800℃, 810℃, 820℃, 850℃, 870℃, 890℃, 920℃; the time of calcination can be selected as 2h, 3h, 4h, 5h, 6h, 7h; the heating rate of calcination can be selected as 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min.

[0032] Preferably, the calcination is performed under an oxygen-containing atmosphere.

[0033] Preferably, the oxygen-containing atmosphere comprises any one of an air atmosphere, an oxygen atmosphere.

[0034] Further preferably, the oxygen-containing atmosphere is an oxygen atmosphere.

[0035] Preferably, the method for preparing Mn2O3 in the manganese-containing precursor comprises the following steps:

[0036] The manganese salt, sodium bicarbonate and solvent are mixed, reacted, and calcined to obtain the Mn2O3.

[0037] Specifically, the manganese-containing precursor Mn2O3 is prepared by co-precipitation and calcination.

[0038] Preferably, the manganese salt comprises manganese chloride.

[0039] Preferably, the solvent comprises water.

[0040] Preferably, the reaction time is 2.7-9h; further preferably, the reaction time is 3-8h; more preferably, the reaction time is 5h.

[0041] Preferably, stirring is performed during the reaction.

[0042] Preferably, the stirring speed is 450-750rpm; further preferably, the stirring speed is 500-700rpm; more preferably, the stirring speed is 600rpm.

[0043] Preferably, after the reaction, the solution after the reaction is subjected to solid-liquid separation, washing, drying, and then calcination.

[0044] Preferably, the solid-liquid separation method comprises any one of centrifugation and filtration.

[0045] Preferably, the washing is sequentially washing with water and ethanol for several times to remove unreacted substances in the material.

[0046] Preferably, the temperature of the calcination is 500-1000℃; further preferably, the temperature of the calcination is 500-700℃; more further preferably, the temperature of the calcination is 600℃.

[0047] Preferably, the time of the calcination is 1-7h; further preferably, the time of the calcination is 1-5h; more further preferably, the time of the calcination is 2h.

[0048] Preferably, the heating rate of the calcination is 3-6℃ / min, further preferably, the heating rate of the calcination is 4-5℃ / min, more further preferably, the heating rate of the calcination is 5℃ / min.

[0049] The third aspect of the present application provides a positive electrode.

[0050] Specifically, the positive electrode comprises a current collector and a positive electrode material layer on the surface of the current collector; the composition of the positive electrode material layer comprises the positive electrode material of the first aspect of the present application.

[0051] Preferably, the composition of the positive electrode material layer further comprises a conductive agent and a binder; the mass ratio of the positive electrode material, the binder and the conductive agent is 1:(0.08-0.18):(0.08-0.18).

[0052] Further preferably, the mass ratio of the positive electrode material, the binder and the conductive agent is 1:(0.09-0.16):(0.09-0.16).

[0053] More further preferably, the mass ratio of the positive electrode material, the binder and the conductive agent is 8:1:1.

[0054] Preferably, the conductive agent comprises at least one of acetylene black, carbon black, carbon fiber, carbon nanotube and graphite.

[0055] Preferably, the binder comprises at least one of polyvinylidene fluoride, carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyacrylamide (PAM) and polytetrafluoroethylene (PTFE).

[0056] The fourth aspect of the present application provides a battery.

[0057] Specifically, the battery comprises a negative electrode, an electrolyte and the positive electrode of the third aspect of the present application.

[0058] Preferably, the battery comprises a potassium ion battery.

[0059] Compared with the prior art, the technical scheme provided by the present application has the following beneficial effects:

[0060] (1) The molecular formula of the positive electrode material of the present application is K 0.5 Mn x Mg y O z F 2-z ; wherein 0 < x < 1.0, 0 < y < 1.0, 0 < z < 2, and x + y = 1. The present application uses F - to replace O 2- , which can expand the interlayer spacing of K 0.5 MnO2(KMO) and inhibit the release of lattice O. This change is conducive to the rapid conversion of K + ions without causing substantial damage to the structure. In addition, the present application can effectively inhibit Jahn-Teller distortion by increasing the average valence of manganese and introducing Mg 2+ and F - ions. This cation and anion doping method can make the reversible capacity of the KMMOF cathode as high as about 110 mAh g -1 (current is 100 mA g -1 ), and when it is applied to a potassium ion battery, the potassium ion battery has good cycle performance and rate capability.

[0061] (2) The preparation method of the present application is simple, low in cost, conducive to commercial application and popularization, and has good practical application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1 is a preparation flowchart of the positive electrode material K 0.5 Mn 0.8 Mg 0.2 O 1.9 F 0.1 of Example 1 of the present application;

[0063] Figure 2 is a scanning electron microscope image of the positive electrode material K 0.5 Mn 0.8 Mg 0.2 O 1.9 F 0.1 of Example 1 of the present application;

[0064] Figure 3 is a transmission electron microscope image of the positive electrode material K 0.5 Mn 0.8 Mg 0.2 O 1.9 F 0.1 of Example 1 of the present application;

[0065] Figure 4 is an X-ray diffraction pattern of the positive electrode material K 0.5 Mn 0.8 Mg 0.2 O 1.9 F 0.1 of Example 1 of the present application;

[0066] Figure 5 is an X-ray photoelectron spectroscopy diagram of the positive electrode material prepared in Example 1 and Comparative Example 1-2 of the present application;

[0067] Figure 6 is a graph of the electron paramagnetic resonance test results of the positive electrode material prepared in Example 1 and Comparative Example 1-2 of the present application;

[0068] Figure 7 is an in-situ differential electrochemical mass spectroscopy diagram of the positive electrode material prepared in Example 1 and Comparative Example 1-2 of the present application;

[0069] Figure 8 is a graph of the rate performance of the battery prepared from the positive electrode material of Example 1 and Comparative Example 1-2 of the present application;

[0070] Figure 9 is a graph of the cycle performance of the battery prepared from the positive electrode material of Example 1 and Comparative Example 1-2 of the present application. DETAILED DESCRIPTION

[0071] In order to make the skilled in the art more clearly understand the technical solutions described in the present application, the following examples are listed for illustration. It should be noted that the following examples do not constitute a limitation on the scope of protection required by the present application.

[0072] The raw materials, reagents or devices used in the following examples, if not specifically stated, can be obtained from conventional commercial channels, or can be obtained by existing known methods.

[0073] Example 1

[0074] A positive electrode material having a molecular formula of K 0.5 Mn 0.8 Mg 0.2 O 1.9 F 0.1 .

[0075] A method for preparing a positive electrode material, comprising the following steps:

[0076] (1) 5.17 g of MnCl2and 2.195 g of NaHCO3were respectively dissolved in 250 mL of aqueous solution, then the two were mixed to form a mixed solution; the mixed solution was then stirred at a rotation speed of 600 rpm for 5 h to react, after filtration, it was washed with water for 3 times and alcohol for 1 time, then it was placed in an oven at 80°C for drying to obtain MnCO3, which was then calcined in a muffle furnace at a temperature of 600°C for 2 h, with a heating rate of 5°C / min, to prepare a precursor Mn2O3;

[0077] (2) 0.088 g of Mn2O3 obtained in step (1) is mixed with 0.06 g of K2CO3, 0.006 g of MgO and 0.0025 g of NH4F by grinding, pressed into a sheet shape to obtain a sheet-shaped mixture, and then the sheet-shaped mixture is calcined at 600°C in an air atmosphere for 2 h, with a calcination temperature increasing rate of 5°C / min, cooled to room temperature, and finally the target product, i.e. a layered transition metal oxide P3-type of K 0.5 Mn 0.8 Mg 0.2 O 1.9 F 0.1 , is recorded as KMMOF.

[0078] Example 1 Positive electrode material K 0.5 Mn 0.8 Mg 0.2 O 1.9 F 0.1 Preparation process schematic diagram is shown in Figure 1, wherein, coprecipitation represents co-precipitation, 1 st calcination represents the first calcination, Air 600°C represents an air atmosphere of 600°C, 2 st calcination represents the second calcination.

[0079] Example 2

[0080] A positive electrode material, whose molecular formula is K 0.5 Mn 0.6 Mg 0.4 O 1.9 F 0.1 .

[0081] Example 2 and Example 1 preparation process only differ in that in step (2) of Example 2, the amount of Mn2O3, K2CO3, MgO and NH4F is 0.065 g, 0.06 g, 0.011 g and 0.0025 g respectively, and the others are the same as Example 1.

[0082] Comparative Example 1

[0083] The molecular formula of the positive electrode material of Comparative Example 1 is K 0.5 MnO2, and the difference between its preparation method and Example 1 is that no MgO and NH4F are added in step (2) of Comparative Example 1.

[0084] Step (2) of Comparative Example 1 is specifically:

[0085] Mn2O3 and 0.06 g of K2CO3 were mixed by grinding, pressed into a tablet, and the tablet was calcined in an air atmosphere at 600°C for 2 h, cooled to room temperature, and finally the target product, a P3-type layered transition metal oxide K 0.5 MnO2, denoted as KMO.

[0086] Comparative Example 2

[0087] The molecular formula of the positive electrode material of Comparative Example 2 is K 0.5 Mn 0.8 Mg 0.2 O2, the difference between the preparation method and Example 1 is that no NH4F is added in step (2) of Comparative Example 2.

[0088] Step (2) of Comparative Example 2 is specifically:

[0089] 0.088 g of Mn2O3 was mixed with 0.06 g of K2CO3 and 0.006 g of MgO by grinding, pressed into a tablet. Then, the mixture was calcined in air at 600°C for 2 hours, cooled to room temperature. Finally, the target product, a P3-type layered transition metal oxide K 0.5 Mn 0.8 Mg 0.2 O2, denoted as KMMO.

[0090] Performance test

[0091] 1. Scanning electron microscope observation

[0092] The positive electrode material K 0.5 Mn 0.8 Mg 0.2 O 1.9 F 0.1 prepared in Example 1 was observed by scanning electron microscope, and the scanning electron microscope image is shown in Figure 2.

[0093] As can be seen from Figure 2, the positive electrode material K 0.5 Mn 0.8 Mg 0.2 O 1.9 F 0.1 prepared in Example 1 is relatively spherical, with an average diameter of 1-2 μm, and it is worth noting that the secondary particles are composed of tabular primary particles.

[0094] 2. Transmission electron microscope observation

[0095] The positive electrode material K 0.5 Mn 0.8 Mg 0.2 O 1.9 F 0.1Transmission electron microscope observation was carried out, and the transmission electron microscope image is shown in Figure 3.

[0096] As can be seen from Figure 3, the positive electrode material shows clear lattice fringes, and the interplanar spacing thereof is 0.259 nm, corresponding to the (101) plane, and has a typical P3-type layered structure.

[0097] 3. X-ray diffraction analysis

[0098] The positive electrode material K 0.5 Mn 0.8 Mg 0.2 O 1.9 F 0.1 X-ray diffraction analysis was carried out, and the results are shown in Figure 4, wherein the abscissa 2Theta (θ) represents the diffraction angle 2θ, the ordinate Intensity represents the diffraction intensity, Yobs represents the experimental value, Ycalc represents the calculated value, Yobs-Ycalc represents the deviation of the experimental value and the calculated value, and Bragg position represents the Bragg peak position.

[0099] As can be seen from Figure 4, the P3-type K 0.5 Mn 0.8 Mg 0.2 O 1.9 F 0.1 layered transition metal oxide of Example 1 was successfully synthesized, and the crystal structure of the P3-type P3-K 0.5 Mn x Mg y O z F 2-z layered transition metal oxide of Example 1 was further studied by Rietveld refinement, and Figure 4 shows the Rietveld refinement data of the P3-type P3-K 0.5 Mn x Mg y O z F 2-z layered transition metal oxide of Example 1, which is consistent with the lattice parameters of other typical P3-type layered K intercalation compounds, and the oxygen layer is ABBCCAA stacking.

[0100] 4. X-ray photoelectron spectroscopy analysis

[0101] X-ray photoelectron spectroscopy analysis was carried out on the positive electrode materials prepared in Example 1 and Comparative Examples 1-2, and the test results are shown in Figure 5, wherein the abscissa Binding energy represents the binding energy, and the ordinate Intensity represents the intensity.

[0102] As can be seen from Figure 5, the XPS results confirm that the Mg and F doping can reduce the Mn 3+The content of the oxygen vacancy can be controlled, and the content of the oxygen vacancy can be increased, so as to enhance the structural stability, electrochemical performance, thermal stability and safety of the material, and to inhibit the adverse side reactions, and the performance and service life of the potassium ion battery are greatly improved as a whole.

[0103] 5. Electron paramagnetic resonance test

[0104] The positive electrode materials prepared in Example 1 and Comparative Examples 1-2 were subjected to electron paramagnetic resonance test, and the test results are shown in FIG. 6, wherein the abscissa Field represents the strength of the applied magnetic field, and the ordinate Intensity represents the intensity.

[0105] As can be seen from FIG. 6, the KMMOF and KMMO materials prepared in Example 1 and Comparative Example 2 show strong electron paramagnetic resonance (EPR) signals at a g-factor value of 2.003, which may be due to the trapping of electrons in oxygen vacancies. The above results further confirm the formation of oxygen vacancies in KMMOF and KMMO. The formation of oxygen vacancies has many positive effects on KMMOF and KMMO materials, including improving electrical conductivity, increasing potassium ion storage capacity, and improving performance. These advantages make oxygen vacancy-containing materials have wide application potential and prospect in the field of energy storage. As can be seen from FIG. 6, compared with KMMO, KMMOF has greater signal intensity, forms more oxygen vacancies, and has greater degree of oxygen vacancies, and has better performance of enhancing electron transport and reducing charge transfer impedance. It is shown that KMMOF is superior to KMMO in increasing potassium ion storage capacity and improving cycle stability.

[0106] 6. In-situ differential electrochemical mass spectrometry analysis

[0107] The positive electrode materials prepared in Example 1 and Comparative Examples 1-2 were subjected to in-situ differential electrochemical mass spectrometry test by using an in-situ differential electrochemical mass spectrometer (DEMS), and the test results are shown in FIG. 7, wherein FIG. 7(a), (b) and (c) are in-situ differential electrochemical mass spectra of the positive electrode materials of Comparative Example 1, Comparative Example 2 and Example 1, respectively, the abscissa Time (s) represents time (seconds), the left ordinate Voltage (V) represents voltage (volts), the right ordinate Gas evolution (umol g -1 m -1 ) represents the amount of gas produced per gram of sample per unit time (umol per gram of sample per minute), and Oxygen release in FIG. 7(a) represents oxygen release.

[0108] As can be seen from FIG. 7, KMMOF and KMMO have no O release, and KMO has obvious O release, which shows that the doping of Mg and F is conducive to inhibiting the release of O in the charging and discharging process. Although KMMOF and KMMO have no O release, in combination with other test means, such as electron paramagnetic resonance (EPR) signal, subsequent rate test, cycle test, it can be seen that the performance (specific capacity, energy density, cycle stability, oxygen vacancy formation, etc.) of KMMOF is superior to that of KMMO, and the doping of F can more promote stability and inhibit distortion.

[0109] 7. Rate performance test

[0110] The positive electrode material prepared in Example 1, Comparative Examples 1-2 is used as an active material, PVDF (polyvinylidene fluoride) is used as a binder, acetylene black is used as a conductive agent, and the mass ratio of the active material, the binder and the conductive agent is 8:1:1; aluminum foil is used as a current collector, potassium metal is used as a counter electrode, and the electrolyte is 2.5 mol / L of potassium bis(fluorosulfonyl)imide / triethyl phosphate (KFSI / TEP) (the mass ratio of KFSI and TEP is 0.461:1), each of which is assembled into a half battery, and the half battery is subjected to a rate test, and the voltage range of the rate performance test is 1.5-4.0V.

[0111] The rate performance curve of the battery prepared from the positive electrode material of Example 1, Comparative Examples 1-2 is shown in FIG. 8, wherein the abscissa Cycle represents the cycle number, the ordinate Discharge Capacity (mAh g -1 ) represents the discharge capacity, the current density: mA g -1 represents the current density, KMnO represents the positive electrode material of Comparative Example 1, KMnMgO represents the positive electrode material of Comparative Example 2, and KMnMgOF represents the positive electrode material of Example 1.

[0112] As can be seen from FIG. 8, the rate performance of the battery prepared from the positive electrode material of Example 1 is superior to that of Comparative Examples 1-2, which shows that the doping of Mg 2+ and F - in Example 1 makes the P3 type K 0.5 Mn x Mg y O z F 2-z (KMMOF) has improved rate performance, which proves the effectiveness of the cation and anion doping strategy.

[0113] 8. Cycle performance test

[0114] The cycle performance tests were carried out on the batteries prepared from the cathode materials of Example 1 and Comparative Examples 1-2. Among them, the preparation method of the battery was the same as that in the above rate performance test, and the test conditions were: constant current charge and discharge, the current density was 0.1 A·g -1 , the voltage range was 1.5 - 4.0 V, and 200 cycles were carried out.

[0115] The cycle performance test results of the batteries prepared from the cathode materials of Example 1 and Comparative Examples 1-2 are shown in Figure 9. Among them, the abscissa Cycle represents the number of cycles, and the left ordinate Discharge Capacity (mAh g -1 ) represents the discharge capacity; the right ordinate Coulombic efficiency (%) represents the Coulomb efficiency.

[0116] As can be seen from Figure 9, the initial specific capacity of the battery prepared from the P3-type K 0.5 Mn 0.8 Mg 0.2 O 1.9 F 0.1 (KMMOF) layered transition metal oxide of Example 1 was about 110 mA·h·g -1 . After 200 cycles, it had a capacity retention rate of 87%. The initial specific capacity of the battery prepared from the KMMO cathode material of Comparative Example 2 was 80 mA·h·g -1 . After 200 cycles, it had a capacity retention rate of 80%. While the initial capacity of the battery prepared from the KMnO cathode material of Comparative Example 1 was only about 60 mA·h·g -1 . After 150 cycles, the battery was damaged. At the same time, since the first cycle, the Coulomb efficiency of the P3-type KMMOF layered transition metal oxide of Example 1 was as high as 100%, further showing good electrochemical reversibility.

[0117] The performance of the cathode material prepared in Example 2 was equivalent to that of Example 1. And after applying the cathode material of Example 2 to the potassium battery, the rate performance and cycle performance of the potassium battery were equivalent to those of the potassium battery prepared from the cathode material of Example 1.

[0118] To sum up, the molecular formula of the cathode material of the present invention is K 0.5 Mn x Mg y O z F 2-z , where 0 < x < 1.0, 0 < y < 1.0, 0 < z < 2, and x + y = 1. The present invention uses F - to replace O 2- which can expand the layer spacing of K 0.5 MnO2 (KMO), inhibit the release of lattice O, and this change is beneficial to K+ rapid conversion of ions without substantial structural damage. In addition, the present application introduces Mg 2+ and F - ions can effectively suppress Jahn-Teller distortion. This cation and anion doping method makes the reversible capacity of the KMMOF cathode as high as about 110 mAh g -1 (current is 100 mAg -1 ), which can be applied to potassium ion batteries to make the potassium ion batteries have good cycle performance and rate capability.

[0119] The above examples are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

A positive electrode material, characterized in that, The molecular formula is K 0.5 Mn x Mg y O z F 2-z ; wherein, 0 < x < 1.0, 0 < y < 1.0, 0 < z < 2, x + y = 1. The positive electrode material according to claim 1, characterized in that The positive electrode material is spherical. The positive electrode material according to claim 1, characterized in that The particle size of the positive electrode material is 0.9-2.2 μm. Process for the production of a cathode material according to any one of claims 1 to 3, characterized in that The method comprises the following steps: The positive electrode material is prepared by mixing a manganese-containing precursor, a magnesium-containing compound, a potassium-containing compound and a fluorine salt, and calcining. The production method according to claim 4, characterized in that The manganese-containing precursor comprises at least one of MnCO3, Mn2O3, manganese acetate and manganese oxalate; and / or, the magnesium-containing compound comprises at least one of MgO and Mg(OH)2; and / or, the potassium-containing compound comprises at least one of K2CO3, KOH and potassium oxalate; and / or, the fluorine salt comprises at least one of NH4F and KF. The production method according to claim 4, characterized in that The mixing is followed by grinding, and then the calcining. The production method according to claim 4, characterized in that The calcining temperature is 500-1000 ℃, and the calcining time is 1-8 h. A positive electrode, characterized by The positive electrode material layer comprises the positive electrode material according to any one of claims 1-3. The positive electrode according to claim 8, characterized in that The positive electrode material layer further comprises a conductive agent and a binder; and the mass ratio of the positive electrode material, the binder and the conductive agent is 1:(0.08-0.18):(0.08-0.18). A battery characterized by The battery comprises a negative electrode, an electrolyte and the positive electrode according to any one of claims 8-9.

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