Positive electrode material and preparation method and application thereof

Abstract

The embodiment of the invention relates to a positive electrode material and a preparation method and application thereof, and the preparation method comprises the following steps: putting a first lithium salt and a transition metal oxide into a zirconium oxide ball milling tank for wet milling to obtain a metal salt precursor; and performing heat treatment on the metal salt precursor in an inert atmosphere to obtain the lithium-rich cation disordered rock salt, placing the lithium-cation-rich disordered rock salt and a second lithium salt in a zirconium oxide ball milling tank for ball milling, so that a non-metallic element in the second lithium salt is inserted into a transition metal gap of the lithium-cation-rich disordered rock salt, thereby forming anions between an oxygen element and the non-metallic element of the lithium-cation-rich disordered rock salt, and obtaining a positive electrode material; wherein non-metallic elements in the second lithium salt are in a cation valence state, and the ion radius is smaller than the lithium ion radius in the first lithium salt and the transition metal ion radius in the transition metal oxide.

Description

Technical Field

[0001] The present invention relates to the field of materials, and particularly to a cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] With the increasing demand for high-energy density, low-cost, and environmentally friendly cathode materials in lithium-ion batteries, improving the electrochemical performance of electrode materials has become a research hotspot.

[0003] Among the lithium-rich cathode materials, cation-disordered rock-salt structure materials have received extensive attention due to their high specific capacity and high cycle stability. Research shows that in the cation-disordered rock-salt structure, lithium ions and transition metal cations each occupy the cubic lattice in the octahedron, and the diffusion of lithium ions is completed through the transition between octahedral sites, which requires passing through a tetrahedral site in the middle. When the ratio of lithium ions to transition metals in the lithium-rich cation-disordered rock-salt exceeds a certain value, a 0-TM (oxygen-ion diffusion without coplanar transition metals) channel that is beneficial to lithium-ion transport will be formed in the material structure, making such materials show great potential in improving the specific capacity and energy density of lithium-ion batteries.

[0004] However, due to the generation of a linear Li-O-Li configuration in the lithium-rich cation-disordered structure, in this configuration, the O2p state is close to the Fermi level, making O more easily oxidized during charging and resulting in redox competition with transition metals. Excessive lithium ions will lead to a decrease in the content of transition metal ions, enabling more oxygen to participate in the redox reaction, which will cause oxygen loss, making the material structure unstable, thereby affecting its cycle performance and increasing the irreversible capacity. Therefore, regulating the degree of oxygen participation in the redox reaction and improving the reversible capacity and cycle performance of the material are the key to the development of lithium-rich cation-disordered rock-salt structure materials. Summary of the Invention

[0005] The object of the present invention is to address the deficiencies of the prior art and provide a cathode material, a preparation method thereof, and an application thereof. The preparation method realizes the doping of non-metal ions into the lithium-rich cation-disordered rock-salt through a solid-phase ball-milling method, and the preparation process is simple and controllable, which can improve the structural stability of the cathode material.

[0006] To achieve the above object, in the first aspect, the present invention provides a preparation method of a cathode material, and the preparation method includes:

[0007] Placing a first lithium salt and a transition metal oxide in a zirconia ball-milling tank for wet milling to obtain a metal salt precursor;

[0008] Performing heat treatment on the metal salt precursor under an inert atmosphere to obtain a lithium-rich cation-disordered rock-salt;

[0009] Place the lithium-rich cation-disordered rock salt and the second lithium salt in the zirconia ball-milling pot for ball milling, so that the non-metal elements in the second lithium salt are inserted into the transition metal interstices of the lithium-rich cation-disordered rock salt, thereby forming anions between the oxygen elements of the lithium-rich cation-disordered rock salt and the non-metal elements, and obtaining a cathode material; wherein, the non-metal elements in the second lithium salt are in a cation valence state and the ionic radius is smaller than the lithium ion radius in the first lithium salt and the transition metal ion radius in the transition metal oxide.

[0010] Preferably, the transition metal oxide includes one or more of TiO2, V2O5, Cr2O3, Mn2O3, Fe2O3, CoO, NiO2, CuO, ZnO, ZrO, Nb2O5, MoO3; the non-metal elements in the second lithium salt are one or more of B, C, N, Si, P, S.

[0011] Preferably, the liquid for wet milling is ethanol or acetone, the rotation speed of wet milling is 200 revolutions per minute - 600 revolutions per minute, and the time is 4 hours - 10 hours.

[0012] Preferably, the conditions for heat treatment are: heating to 800°C - 1000°C at a heating rate of 1°C / min - 5°C / min and holding for 4 hours - 10 hours.

[0013] Preferably, the chemical formula of the lithium-rich cation-disordered rock salt is: Li 1+x M y O2, 0 < x ≤ 0.4, 0.6 ≤ y ≤ 0.99; wherein, M represents a transition metal element.

[0014] Preferably, the weight percentage of the second lithium salt in the lithium-rich cation-disordered rock salt is 0.2wt% - 5wt%.

[0015] Preferably, the rotation speed of ball milling is 500 revolutions per minute - 1000 revolutions per minute, and the time is 6 hours - 24 hours.

[0016] In a second aspect, the present invention provides a cathode material, and the cathode material is prepared by the preparation method according to any one of the first aspects above.

[0017] In a third aspect, the present invention provides a positive electrode sheet, and the positive electrode sheet includes the cathode material according to the second aspect.

[0018] In a fourth aspect, the present invention provides a lithium-ion battery, and the lithium-ion battery includes the positive electrode sheet according to the third aspect.

[0019] A preparation method of a cathode material provided by an embodiment of the present invention obtains a metal salt precursor through a wet grinding method, then obtains a lithium-rich cation disordered rock salt by heat-treating the metal salt precursor, and finally realizes doping of non-metallic elements into the lithium-rich cation disordered rock salt through a ball milling method, so that the non-metallic elements and oxygen elements in the lithium-rich cation disordered rock salt can form anions, thereby obtaining a non-metallic element-doped lithium-rich cation disordered rock salt cathode material. When this cathode material is applied in a lithium-ion battery, the doping of non-metallic elements can weaken the oxidation-reduction competition between oxygen and transition metals, reduce oxygen loss, improve the structural stability of this cathode material, and thus improve the reversible capacity of the lithium-ion battery; moreover, the anions formed by non-metallic elements and surrounding oxygen elements can expand the diffusion path of lithium ions and improve the electron transport ability, can significantly reduce the charge transfer impedance, and improve the cycle stability of the lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a flowchart of the preparation method of the cathode material provided by the embodiment of the present invention;

[0021] Figure 2 It is an XRD diagram of the cathode materials provided by Example 1 and Comparative Example 1 of the present invention;

[0022] Figure 3 It is an SEM diagram of the cathode material provided by Example 1 of the present invention;

[0023] Figure 4 It is an SEM diagram of the cathode material provided by Comparative Example 1 of the present invention;

[0024] Figure 5 It is a charge-discharge curve diagram of a button-type half-cell assembled with the cathode material prepared in Example 1 of the present invention;

[0025] Figure 6 It is a charge-discharge curve diagram of a button-type half-cell assembled with the cathode material prepared in Comparative Example 1 of the present invention;

[0026] Figure 7 It is a cycle performance diagram of a button-type half-cell assembled with the cathode materials prepared in Example 1 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0029] An embodiment of the present invention provides a method for preparing a cathode material, and the process is as Figure 1 shown, including the following steps:

[0030] Step 110: Place the first lithium salt and the transition metal oxide in a zirconia ball milling jar for wet milling to obtain a metal salt precursor;

[0031] Specifically, the first lithium salt may specifically include one or more of lithium carbonate, lithium acetate, lithium oxalate, lithium nitrate, and lithium hydroxide. The transition metal oxide may specifically include one or more of TiO2, V2O5, Cr2O3, Mn2O3, Fe2O3, CoO, NiO2, CuO, ZnO, ZrO, Nb2O5, and MoO3. The liquid for wet milling is ethanol or acetone, the rotation speed of wet milling is 200 revolutions per minute - 600 revolutions per minute, preferably 350 revolutions per minute - 500 revolutions per minute, and the time is 4 hours - 10 hours, preferably 6 hours - 8 hours. Wet milling has the advantages of high grinding efficiency, low noise, and less environmental pollution to the working environment, and can make the particle size of the material fine and uniform.

[0032] Step 120: Under an inert atmosphere, heat-treat the metal salt precursor to obtain a lithium-rich cation disordered rock salt;

[0033] Specifically, the inert atmosphere may be nitrogen and / or argon. The heat treatment can be specifically carried out in a muffle furnace or a tube furnace. The specific conditions are: heating at a heating rate of 1 °C / min - 5 °C / min to 800 °C - 1000 °C, and holding for 4 hours - 10 hours, preferably heating at a heating rate of 2 °C / min - 4 °C / min to 850 °C - 950 °C, and holding for 6 hours - 8 hours. The chemical formula of the lithium-rich cation disordered rock salt is: Li 1+x M y O2, 0 < x ≤ 0.4, 0.6 ≤ y ≤ 0.99; where M represents transition metal elements such as Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, and Mo.

[0034] Step 130: Place the lithium-rich cation disordered rock salt and the second lithium salt in a zirconia ball milling jar for ball milling, so that the non-metal element in the second lithium salt is inserted into the transition metal gap of the lithium-rich cation disordered rock salt, so that an anion is formed between the oxygen element and the non-metal element of the lithium-rich cation disordered rock salt, and a cathode material is obtained;

[0035] Among them, the weight percentage of the added second lithium salt in the lithium-rich cation disordered rock salt is 0.2 wt% - 5 wt%. Among them, the non-metallic element in the second lithium salt can be one or more of B, C, N, Si, P, and S, and the non-metallic element is in a cation valence state. The rotation speed of ball milling is 500 revolutions per minute - 1000 revolutions per minute, preferably 600 revolutions per minute - 800 revolutions per minute, and the time is 6 hours - 24 hours, preferably 8 - 12 hours.

[0036] Since the non-metallic ion radii in the second lithium salt are all smaller than the lithium ion and transition metal ion radii in the lithium-rich cation disordered rock salt, and it is processed by solid-phase ball milling, during the ball milling of the solid material, due to the local heating and pressure effects generated when the ball impacts the powder, the lattice structure may change, resulting in the generation of lattice defects such as point defects and interstitial atoms. These defects can provide additional positions, making it easy for external elements to be inserted into the material through ball milling.

[0037] Combining the above two points, the non-metallic ions in the second lithium salt are more likely to be doped into the interstitial positions of the transition metal elements rather than replacing the transition metal elements. In this way, the non-metallic element and the oxygen element in the lithium-rich cation disordered rock salt can form anions without destroying the structure of the lithium-rich cation disordered rock salt.

[0038] When this cathode material is applied in a lithium-ion battery, the doping of the non-metallic element can weaken the redox competition between oxygen and the transition metal, reduce oxygen loss, improve the structural stability of the cathode material, and thus improve the reversible capacity of the lithium-ion battery; moreover, the anion formed by the non-metallic element and the surrounding oxygen element can expand the diffusion path of lithium ions and improve the electron transport ability, which can significantly reduce the charge transfer resistance and improve the cycle stability of the lithium-ion battery.

[0039] For example, when the lithium-rich cation disordered rock salt is Li 1.3 Mn 0.8 O2 and the non-metallic ion is P 5+ , because the electronegativity of phosphorus is stronger than that of manganese, the electron interaction between P and O is stronger than the Mn-O bond, and it is easy to form PO4 3- .

[0040] In summary, a method for preparing a cathode material provided by an embodiment of the present invention obtains a metal salt precursor through a wet grinding method, then obtains a lithium-rich cation disordered rock salt through heat treatment of the metal salt precursor, and finally realizes doping of non-metal elements into the lithium-rich cation disordered rock salt through a ball milling method, so that the non-metal elements and oxygen elements in the lithium-rich cation disordered rock salt can form anions, thereby obtaining a non-metal element-doped lithium-rich cation disordered rock salt cathode material. When this cathode material is applied in a lithium-ion battery, the doping of non-metal elements can weaken the oxidation-reduction competition between oxygen and transition metals, reduce oxygen loss, improve the structural stability of the cathode material, and thus improve the reversible capacity of the lithium-ion battery; moreover, the anions formed by non-metal elements and surrounding oxygen elements can expand the diffusion path of lithium ions and improve the electron transport ability, can significantly reduce the charge transfer impedance, and improve the cycle stability of the lithium-ion battery.

[0041] The cathode material provided by the embodiment of the present invention can be applied to the electrode material of a lithium-ion battery.

[0042] To better understand the technical solution provided by the present invention, the following uses multiple specific examples to separately illustrate the specific process of preparing the cathode material by applying the method provided by the above embodiment of the present invention, and the electrochemical characteristics of the prepared cathode material.

[0043] Example 1

[0044] Step 1: According to the stoichiometric ratio of Li 1.2 T i 0.4 Mn 0.4 O2, weigh 500 g of Li2CO3, TiO2, and Mn2O3 and place them in a zirconia ball milling jar, and add 500 mL of ethanol. Wet grind at a speed of 500 revolutions per minute for 4 hours to obtain a metal salt precursor.

[0045] Step 2: Under the protection of an argon atmosphere, place the metal salt precursor in a muffle furnace, and then heat the muffle furnace to 900 °C at a heating rate of 5 °C / min. Keep it at this temperature for 10 hours, and after natural cooling to room temperature, obtain Li 1.2 Ti 0.4 Mn 0.4 O2.

[0046] Step 3: Place Li 1.2 T i 0.4 Mn 0.4 O2 in a ball milling jar, add Li2B4O7 with a weight percentage of 2 wt%, and then ball mill at a speed of 600 revolutions per minute for 8 hours to obtain a boron-doped lithium-rich cation disordered rock salt cathode material.

[0047] After that, the prepared cathode material was used to prepare the electrode sheet of the lithium-ion battery, and the button-type half-cell was assembled with this electrode sheet for testing, as follows:

[0048] First, the cathode material, conductive carbon black, and binder polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP) in a mass ratio of 8:1:1 and mixed evenly. The slurry was prepared with a beater and coated on aluminum foil to obtain the electrode sheet, which was dried at 80 °C for 12 hours.

[0049] Secondly, the dried electrode sheet was cut into 12-mm circular pieces, and the loading of the active material on each circular piece was 2 mg / cm 2 .

[0050] Then, the above electrode sheet was assembled into a CR2032-type button-type half-cell in an argon-filled glove box. Among them, the electrolyte of the CR2032-type button-type half-cell was 1 mol / L lithium hexafluorophosphate LiPF6, the solvent of the electrolyte was ethylene carbonate (EC) and dimethyl carbonate (DMC), and the volume ratio of EC and DMC was 1:1. The counter electrode was a lithium sheet.

[0051] Finally, the CR2032-type button-type half-cell was left standing for 8 hours and then subjected to charge-discharge testing on a BlueTEC battery testing system (CT2001A) at room temperature. The testing conditions were: voltage 1.5 V - 4.8 V, and charge-discharge cycling testing was carried out at a current density of 0.1C.

[0052] Example 2

[0053] Step 1: According to the stoichiometric ratio of Li 1.1 Fe 0.35 Mn 0.62 O2, 500 g of Li2CO3, Fe2O3, and Mn2O3 were weighed and placed in a zirconia ball milling jar, and 500 mL of ethanol was added. It was wet milled at a speed of 400 revolutions per minute for 6 hours to obtain the metal salt precursor.

[0054] Step 2: Under the protection of an argon atmosphere, the metal salt precursor was placed in a muffle furnace, and then the muffle furnace was heated to 850 °C at a heating rate of 3 °C / min. It was kept at this temperature for 8 hours and then naturally cooled to room temperature to obtain Li 1.1 Fe 0.35 Mn 0.62 O2.

[0055] Step 3: Li 1.1 Fe 0.35 Mn 0.62O2 was placed in a ball milling jar, and then Li3PO4 with a weight percentage of 3 wt% was added. After that, it was ball milled at a speed of 700 revolutions per minute for 8 hours to obtain a phosphorus-doped lithium-rich cation disordered rock salt cathode material.

[0056] The process of assembling the coin-type half-cell and testing the electrochemical performance was the same as that in Example 1.

[0057] Example 3

[0058] Step 1. According to the stoichiometric ratio of Li 1.25 Nb 0.25 Mn 0.5 O2, 500 g of Li2CO3, Nb2O5, and Mn2O3 were weighed and placed in a zirconia ball milling jar, and 500 mL of ethanol was added. It was wet milled at a speed of 300 revolutions per minute for 5 hours to obtain a metal salt precursor.

[0059] Step 2. Under the protection of an argon atmosphere, the metal salt precursor was placed in a muffle furnace, and then the muffle furnace was heated to 950 °C at a heating rate of 5 °C / min. It was held at this temperature for 6 hours, and after natural cooling to room temperature, Li 1.25 Nb 0.25 Mn 0.5 O2 was obtained.

[0060] Step 3. Li 1.25 Nb 0.25 Mn 0.5 O2 was placed in a ball milling jar, and then LiNO3 with a weight percentage of 1.5 wt% was added. After that, it was ball milled at a speed of 550 revolutions per minute for 12 hours to obtain a nitrogen-doped lithium-rich cation disordered rock salt cathode material.

[0061] The process of assembling the coin-type half-cell and testing the electrochemical performance was the same as that in Example 1.

[0062] Comparative Example 1

[0063] Step 1. According to the stoichiometric ratio of Li 1.2 T i 0.4 Mn 0.4 O2, 500 g of Li2CO3, T iO2, and Mn2O3 were weighed and placed in a zirconia ball milling jar, and 500 mL of ethanol was added. It was wet milled at a speed of 500 revolutions per minute for 4 hours to obtain a metal salt precursor.

[0064] Step 2. Under the protection of an argon atmosphere, the metal salt precursor was placed in a muffle furnace, and then the muffle furnace was heated to 900 °C at a heating rate of 5 °C / min. It was held at this temperature for 10 hours, and after natural cooling to room temperature, Li 1.2 Ti 0.4 Mn 0.4 O2 was obtained.

[0065] The assembly of the coin-type half-cell and the testing process of the electrochemical performance were the same as those in Example 1.

[0066] Comparative Example 2

[0067] Step 1: According to the stoichiometric ratio of Li 1.1 Fe 0.35 Mn 0.62 O2, 500 g of Li2CO3, Fe2O3, and Mn2O3 were weighed and placed in a zirconia ball-milling jar, and 500 mL of ethanol was added. Wet milling was carried out at a speed of 400 revolutions per minute for 6 hours to obtain a metal salt precursor.

[0068] Step 2: Under the protection of an argon atmosphere, the metal salt precursor was placed in a muffle furnace, and then the muffle furnace was heated to 850 °C at a heating rate of 3 °C / min. After holding at this temperature for 8 hours and naturally cooling to room temperature, Li 1.1 Fe 0.35 Mn 0.62 O2 was obtained.

[0069] The assembly of the coin-type half-cell and the testing process of the electrochemical performance were the same as those in Example 1.

[0070] Comparative Example 3

[0071] Step 1: According to the stoichiometric ratio of Li 1.25 Nb 0.25 Mn 0.5 O2, 500 g of Li2CO3, Nb2O5, and Mn2O3 were weighed and placed in a zirconia ball-milling jar, and 500 mL of ethanol was added. Wet milling was carried out at a speed of 300 revolutions per minute for 5 hours to obtain a metal salt precursor.

[0072] Step 2: Under the protection of an argon atmosphere, the metal salt precursor was placed in a muffle furnace, and then the muffle furnace was heated to 950 °C at a heating rate of 5 °C / min. After holding at this temperature for 6 hours and naturally cooling to room temperature, Li 1.25 Nb 0.25 Mn 0.5 O2 was obtained.

[0073] The assembly of the coin-type half-cell and the testing process of the electrochemical performance were the same as those in Example 1.

[0074] Table 1 shows the constant current charge and discharge cycle test data of the coin-type half-cells assembled with the cathode materials prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention.

[0075]

[0076] Table 1

[0077] As can be seen from Table 1, the discharge specific capacity of the coin-type half-cells prepared in the embodiments of the present invention is greater than that of the comparative examples, and after 30 cycles, the capacity retention rate of the coin-type half-cells of the present application is above 96%. This is because non-metal ion doping is carried out in the cathode material of the present invention, which can weaken the redox competition between oxygen ions and transition metal ions in the lithium-rich cation disordered rock salt, improve the structural stability of the cathode material, and thus enhance the reversible capacity and cycling performance of the coin-type half-cells.

[0078] Figure 2 XRD patterns of the cathode materials provided in Example 1 and Comparative Example 1 of the present invention are as Figure 2 shown. Boron doping has no effect on the structure of the lithium-rich cation disordered rock salt and still retains the structure of the disordered rock salt.

[0079] Figure 3 SEM image of the cathode material provided in Example 1 of the present invention, Figure 4 SEM image of the cathode material provided in Comparative Example 1 of the present invention. By comparing Figure 3 and Figure 4 it can be seen that boron doping has no effect on the morphology of the lithium-rich cation disordered rock salt.

[0080] Combining Figure 2 、 3 、4, it can be concluded that the doping of non-metal ions in the present invention does not damage the structure and morphology of the lithium-rich cation disordered rock salt. Therefore, the cathode material of the present invention still retains the advantages of the lithium-rich cation disordered rock salt, such as high specific capacity and energy density.

[0081] Figure 5 Charge-discharge curve of the coin-type half-cell assembled with the cathode material prepared in Example 1 of the present invention; Figure 6 Charge-discharge curve of the coin-type half-cell assembled with the cathode material prepared in Comparative Example 1 of the present invention. By comparing Figure 5 and Figure 6 , at a current density of 0.1C and cycling for different numbers of times, the charge-discharge curves of the coin-type half-cells of Example 1 and Comparative Example 1 have similar shapes, indicating that after non-metal ion doping, the cathode material still retains the structure of the cation disordered rock salt. After 30 cycles, the attenuation rates of the discharge specific capacity and discharge voltage of the coin-type half-cell of Example 1 are significantly less than those of Comparative Example 1, indicating that the coin-type half-cell assembled with the cathode material of Example 1 of the present invention has a higher reversible capacity and better cycling stability.

[0082] Figure 7 Cycling performance diagrams of the coin-type half-cells assembled with the cathode materials prepared in Example 1 and Comparative Example 1 of the present invention are as Figure 7As shown, after 30 cycles, the coin-type half-cell of Example 1 of the present invention still maintains a high discharge specific capacity, while the coin-type half-cell of Comparative Example 1 starts to decay in discharge specific capacity after 11 cycles.

[0083] In summary, the positive electrode material of the present invention has good structural stability, so that the coin-type half-cell prepared with this positive electrode material has high reversible capacity and cycle stability.

[0084] Example 4

[0085] Step 1: According to the stoichiometric ratio of Li 1.3 Nb 0.3 Mn 0.4 O2, weigh 500 g of CH3COOLi, Nb2O5, and Mn2O3 and place them in a zirconia ball milling jar. Then add 500 mL of acetone and wet mill at a speed of 500 revolutions per minute for 8 hours to obtain a metal salt precursor.

[0086] Step 2: Under the protection of an argon atmosphere, place the metal salt precursor in a muffle furnace. Then heat the muffle furnace at a heating rate of 3 °C / min to 930 °C, keep it at this temperature for 10 hours, and naturally cool to room temperature to obtain Li 1.3 Nb 0.3 Mn 0.4 O2.

[0087] Step 3: Place Li 1.3 Nb 0.3 Mn 0.4 O2 in a ball milling jar, add Li3CO3 with a weight percentage of 1 wt%, and then ball mill at a speed of 800 revolutions per minute for 8 hours to obtain a carbon-doped lithium-rich cation disordered rock salt positive electrode material.

[0088] Example 5

[0089] Step 1: According to the stoichiometric ratio of Li 1.2 Cr 0.4 Ti 0.4 O2, weigh 500 g of Li2CO3, Cr2O3, and TiO2 and place them in a zirconia ball milling jar. Then add 500 mL of ethanol and wet mill at a speed of 600 revolutions per minute for 10 hours to obtain a metal salt precursor.

[0090] Step 2: Under the protection of an argon atmosphere, place the metal salt precursor in a muffle furnace. Then heat the muffle furnace at a heating rate of 2 °C / min to 850 °C, keep it at this temperature for 9 hours, and naturally cool to room temperature to obtain Li 1.2 Cr 0.4 Ti 0.4 O2.

[0091] Step 3: Place Li 1.2 Cr 0.4 Ti 0.4 O2 into a ball milling jar, then add Li2B4O7 with a weight percentage of 3 wt%, and then ball mill at a speed of 650 revolutions per minute for 10 hours to obtain a boron-doped lithium-rich cation disordered rock salt cathode material.

[0092] Example 6

[0093] Step 1: According to the stoichiometric ratio of Li 1.15 Ti 0.34 V 0.3 O2, weigh 500 g of Li2C2O4, V2O5, and TiO2 and place them in a zirconia ball milling jar, and add 500 mL of ethanol, and wet mill at a speed of 400 revolutions per minute for 6 hours to obtain a metal salt precursor.

[0094] Step 2: Under the protection of an argon atmosphere, place the metal salt precursor in a muffle furnace, and then heat the muffle furnace at a heating rate of 5 °C / min to 950 °C, keep it at this temperature for 8 hours, and naturally cool to room temperature to obtain Li 1.15 Ti 0.34 V 0.3 O2.

[0095] Step 3: Place Li 1.15 Ti 0.34 V 0.3 O2 into a ball milling jar, then add Li4SiO4 with a weight percentage of 2.5 wt%, and then ball mill at a speed of 700 revolutions per minute for 10 hours to obtain a silicon-doped lithium-rich cation disordered rock salt cathode material.

[0096] Example 7

[0097] Step 1: According to the stoichiometric ratio of Li 1.2 Ti 0.2 Nb 0.1 Mn 0.5 O2, weigh 500 g of Li2CO3, TiO2, Nb2O5, and Mn2O3 and place them in a zirconia ball milling jar, and add 500 mL of ethanol, and wet mill at a speed of 350 revolutions per minute for 5 hours to obtain a metal salt precursor.

[0098] Step 2: Under the protection of a nitrogen atmosphere, place the metal salt precursor in a muffle furnace, and then heat the muffle furnace at a heating rate of 5 °C / min to 800 °C, keep it at this temperature for 10 hours, and naturally cool to room temperature to obtain Li 1.2 Ti 0.2 Nb 0.1 Mn 0.5 O2.

[0099] Step 3: Place Li 1.2 Ti 0.2 Nb 0.1 Mn 0.5 O2 in a ball milling jar, then add Li2SO4 with a weight percentage of 3 wt%, and then ball mill at a speed of 900 revolutions per minute for 6 hours to obtain a sulfur-doped lithium-rich cation disordered rock salt cathode material.

[0100] Example 8

[0101] Step 1: According to the stoichiometric ratio of Li 1.2 Nb 0.2 Mn 0.6 O2, weigh 500 g of Li2CO3, Nb2O5, and Mn2O3 and place them in a zirconia ball milling jar, and add 500 mL of acetone, and wet mill at a speed of 400 revolutions per minute for 4 hours to obtain a metal salt precursor.

[0102] Step 2: Under the protection of a nitrogen atmosphere, place the metal salt precursor in a muffle furnace, and then heat the muffle furnace to 850 °C at a heating rate of 3 °C / min, and keep it at this temperature for 5 hours. After natural cooling to room temperature, obtain Li 1.2 Nb 0.2 Mn 0.6 O2.

[0103] Step 3: Place Li 1.2 Nb 0.2 Mn 0.6 O2 in a ball milling jar, then add Li3PO4 with a weight percentage of 5 wt%, and then ball mill at a speed of 650 revolutions per minute for 12 hours to obtain a phosphorus-doped lithium-rich cation disordered rock salt cathode material.

[0104] Example 9

[0105] Step 1: According to the stoichiometric ratio of Li 1.4 Co 0.2 Ni 0.4 O2, weigh 500 g of LiNO3, CoO, and NiO2 and place them in a zirconia ball milling jar, and add 500 mL of acetone, and wet mill at a speed of 200 revolutions per minute for 9 hours to obtain a metal salt precursor.

[0106] Step 2: Under the protection of a nitrogen atmosphere, place the metal salt precursor in a tube furnace, and then heat the tube furnace to 1000 °C at a heating rate of 1 °C / min, and keep it at this temperature for 4 hours. After natural cooling to room temperature, obtain Li 1.4 Co 0.2 Ni 0.4 O2.

[0107] Step 3: Place Li 1.4 Co 0.2 Ni 0.4 O2 in a ball milling jar, then add Li2CO3 with a weight percentage of 0.2 wt%, and then ball mill at a speed of 1000 revolutions per minute for 6 hours to obtain a carbon-doped lithium-rich cation disordered rock salt cathode material.

[0108] Example 10

[0109] Step 1: According to the stoichiometric ratio of Li 1.1 Cu 0.5 Zn 0.4 O2, weigh 500 g of LiOH, CuO, and ZnO and place them in a zirconia ball milling jar, and add 500 mL of ethanol, and wet mill at a speed of 600 revolutions per minute for 7 hours to obtain a metal salt precursor.

[0110] Step 2: Under the protection of a nitrogen atmosphere, place the metal salt precursor in a muffle furnace, and then heat the muffle furnace at a heating rate of 4 °C / min to 900 °C, and keep it at this temperature for 8 hours. After naturally cooling to room temperature, obtain Li 1.1 Cu 0.5 Zn 0.4 O2.

[0111] Step 3: Place Li 1.1 Cu 0.5 Zn 0.4 O2 in a ball milling jar, then add LiNO3 with a weight percentage of 0.5 wt%, and then ball mill at a speed of 500 revolutions per minute for 24 hours to obtain a nitrogen-doped lithium-rich cation disordered rock salt cathode material.

[0112] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a cathode material, characterized in that, The preparation method includes the following steps: Placing a first lithium salt and a transition metal oxide in a zirconia ball milling jar for wet milling to obtain a metal salt precursor; Performing heat treatment on the metal salt precursor under an inert atmosphere to obtain a lithium-rich cation disordered rock salt; Placing the lithium-rich cation disordered rock salt and a second lithium salt in the zirconia ball milling jar for ball milling, so that the non-metal element in the second lithium salt is inserted into the transition metal gap of the lithium-rich cation disordered rock salt, thereby forming an anion between the oxygen element of the lithium-rich cation disordered rock salt and the non-metal element to obtain a cathode material; wherein, the non-metal element in the second lithium salt has a cation valence state and an ionic radius smaller than the lithium ion radius in the first lithium salt and the transition metal ion radius in the transition metal oxide.

2. The preparation method according to claim 1, characterized in that, The transition metal oxide includes one or more of TiO2, V2O5, Cr2O3, Mn2O3, Fe2O3, CoO, NiO2, CuO, ZnO, ZrO, Nb2O5, MoO3; the non-metal element in the second lithium salt is one or more of B, C, N, Si, P, S.

3. The preparation method according to claim 1, characterized in that, The liquid for wet milling is ethanol or acetone, the rotation speed of wet milling is 200 revolutions per minute - 600 revolutions per minute, and the time is 4 hours - 10 hours.

4. The preparation method according to claim 1, characterized in that, The conditions for heat treatment are: heating to 800°C - 1000°C at a heating rate of 1°C / min - 5°C / min, and holding for 4 hours - 10 hours.

5. The preparation method according to claim 1, characterized in that, The chemical formula of the lithium-rich cation disordered rock salt is: Li 1+x M y O2, where 0 < x ≤ 0.4 and 0.6 ≤ y ≤ 0.99; wherein, M represents a transition metal element.

6. The preparation method according to claim 1, characterized in that, The weight percentage of the second lithium salt in the lithium-rich cation disordered rock salt is 0.2wt% - 5wt%.

7. The preparation method according to claim 1, characterized in that, The rotation speed of ball milling is 500 revolutions per minute - 1000 revolutions per minute, and the time is 6 hours - 24 hours.

8. A cathode material, characterized in that, The cathode material is prepared by the preparation method according to any one of claims 1 - 7 above.

9. A positive electrode sheet, characterized in that, The cathode electrode sheet includes the cathode material according to claim 8.

10. A lithium-ion battery, characterized in that, The lithium ion battery includes the cathode electrode sheet according to claim 9.

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