In-situ borate-coated oxide composite positive electrode material, preparation method and use

Abstract

The present invention relates to an oxide composite positive electrode material in situ coated with borate, a preparation method and use thereof, the general chemical formula of which is: γA x B y O z ‑Na a Li b Ni c Cu d Mn e M f O 2+β In the material, Li, Ni, Cu, Mn, and the element M that replaces the transition metal position jointly occupy the transition metal ion position in the crystal structure; the space group of the layered oxide composite positive electrode material is P63 / mmc or P63 / mcm or #imgabs0#, and the corresponding structure is P2 phase or O3 phase; A x B y O z For Na a Li b Ni c Cu d Mn e M f O 2+β The needle-like structure coating layer is generated in situ on the surface by the coating material precursor and the Na a Li b Ni c Cu d Mn e M f O 2+β A layered oxide precursor is generated during the sintering process; γ is the mass fraction of the coating material precursor to the layered oxide precursor, 0.1wt%≤γ≤10wt%; and A is Li and / or Na. The composite cathode material of the present invention not only has a high capacity, but also, due to the presence of the needle-like coating layer, significantly reduces residual alkali on the material surface, significantly improves stability in air, achieves high initial charge and discharge efficiency, and has a long cycle life.

Description

Technical Field

[0001] The present invention relates to the field of material technology, and in particular to an oxide composite positive electrode material in situ coated with borate, a preparation method and use thereof. Background Art

[0002] The development of sustainable clean energy has long been a focus of global attention. However, the conversion of wind, solar, and tidal energy into electricity is subject to significant natural constraints, including significant temporal discontinuities and uneven spatial distribution. This results in poor controllability and stability of the electricity they provide, preventing direct input into the grid. Therefore, only by supporting high-performance, large-scale energy storage systems to address the time difference between power generation and consumption and regulate power quality can reliable power supply be ensured. my country's current sustainable energy development places an urgent need for large-scale energy storage technology, which is also a research hotspot worldwide.

[0003] Existing energy storage methods are categorized as physical and chemical. Pumped hydro is the most widely used and offers the largest storage capacity. However, pumped hydro is limited by geographical location and has a long construction period. Other physical energy storage methods, such as compressed air and flywheel storage, have yet to achieve widespread adoption. Electrochemical energy storage, which stores and releases electricity through reversible chemical reactions, has attracted widespread attention for its high energy conversion efficiency and power density, long cycle life, short construction period, and low maintenance costs.

[0004] Currently, electrochemical energy storage primarily encompasses high-temperature sodium-sulfur (Na-S) batteries, flow batteries, lead-acid batteries, and lithium-ion batteries. Na-S batteries operate at 300°C, with metallic sodium and elemental sulfur in a molten state. Failure of the materials at high temperatures can easily cause fires within the battery module, leading to significant safety concerns and preventing widespread adoption. Flow batteries have lower energy density and are bulky. Compared to Ni-Cd batteries, lead-acid batteries, lacking a memory effect and offering lower costs, currently account for the vast majority of the energy storage market and enjoy widespread application. However, they also have significant drawbacks, such as the environmental impact of lead, low battery energy density, heavy weight, and large size, leading to increased maintenance costs. Because energy storage systems must be low-cost, environmentally friendly, long-lasting, and safe, lithium-ion and sodium-ion secondary batteries have become increasingly important technologies among the numerous electrochemical energy storage materials used.

[0005] Currently, lithium-ion batteries, as electrochemical energy storage, have been widely used in daily life due to their high energy density, high cycle stability, long cycle life, small size, light weight and pollution-free. Considering that sodium and lithium are both alkali metal elements in the periodic table, they have similar physical and chemical properties. Sodium-ion batteries and lithium-ion batteries have similar charge-discharge storage mechanisms. More importantly, sodium is abundant and widely distributed in nature, and has a significant price advantage. In addition to the low price of sodium ions, aluminum foil can be used for both the positive and negative current collectors of sodium-ion batteries, while lithium-ion batteries can only use copper for the negative electrode. Obviously, copper is much more expensive than aluminum, so the raw material cost is low and easy to obtain. These advantages have made sodium-ion batteries increasingly popular around the world.

[0006] However, sodium ion batteries are still in the research stage, and there is no commercial sodium ion battery positive electrode material. Currently, researchers' research on sodium ion batteries mainly focuses on layered oxide positive electrode materials Na x MO2 (M represents 3d transition metal elements, which may include one or more, such as Ti, V, Cr, Fe, Mn, Co, Ni, Cu, Nb, Ru, Mo, Zn, etc.). The basis of the battery is redox reaction, and the essence of the reaction is the change in valence, that is, the transfer and displacement of electrons. The half-reaction of losing electrons is an oxidation reaction, and the valence of the positive electrode material increases; the half-reaction of gaining electrons is a reduction reaction, and the valence of the positive electrode material decreases. The layered oxide positive electrode materials of sodium ion batteries introduced above all contain transition metal materials that can undergo redox reactions, and the variable valence transition metals in the initial state of the materials are in a lower valence state. However, there are still many cases where the transition metal ions cannot completely change valence and the capacity cannot be fully utilized, and the air stability of these positive electrode materials is insufficient, resulting in poor consistency. Summary of the Invention

[0007] The embodiments of the present invention provide an oxide composite positive electrode material with in-situ borate coating, a preparation method, and an application. The positive electrode material is an air-stable, high-capacity, and high-cycle-stability material. The morphology of its coating layer is special and becomes needle-shaped after contact with air. The coating layer is smoothly attached to the surface of the material before contact with air. After contact with air, the morphology of the coating layer changes to a needle-like shape, which greatly reduces the residual alkali generated on the surface of the material due to contact with air, significantly improves the stability in air, and has higher electrical conductivity and sodium ion diffusion capacity of the material, lower charge transfer impedance, higher initial charge and discharge efficiency, better cycle capacity, and especially longer cycle life.

[0008] In the first aspect, the embodiment of the present invention provides an oxide composite positive electrode material with in-situ borate coating, the chemical formula of the material is: γA x B y O z -Naa Li b Ni c Cu d Mn e M f O 2+β ;

[0009] In the material, Li, Ni, Cu, Mn, and M jointly occupy the transition metal ion position in the crystal structure; wherein M is an element that dopes and replaces the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of the fourth period and the fifth period;

[0010] a, b, c, d, e, f, and 2+β are the molar percentages of the corresponding elements, and each component in the general chemical formula satisfies charge conservation and stoichiometric conservation; wherein b+c+d+e+f=1, and a+b+2c+2d+4e+mf=2(2+β); 0.67≤a≤1; 0<b≤0.2; 0<c≤0.65; 0<d≤0.28; 0<e≤0.65; -0.05≤β≤0.05; m is the valence state of M;

[0011] The space group of the layered oxide composite positive electrode material is P63 / mmc or P63 / mcm or The corresponding structure is P2 phase or O3 phase;

[0012] The A x B y O z For Na a Li b Ni c Cu d Mn e M f O 2+β The needle-like structure coating layer is generated in situ on the surface, and the coating material precursor is used to generate Na a Li b Ni c Cu d Mn e M f O 2+β A layered oxide precursor is generated during the sintering process; wherein γ is the mass fraction of the coating material precursor to the layered oxide precursor, 0.1wt%≤γ≤10wt%; A is Li and / or Na, 0<x≤3, 0<y≤10, 0<z≤15.

[0013] Preferably, the coating material precursor is boron oxide or boric acid; the molten coating material precursor forms an A with a portion of the sodium salt and / or lithium salt in the layered oxide precursor.x B y O z .

[0014] In a second aspect, an embodiment of the present invention provides a method for preparing the oxide composite positive electrode material having in-situ borate coating as described in the first aspect, wherein the method is a solid phase method, comprising:

[0015] A layered oxide precursor and a coating material precursor accounting for 0.1 wt% to 10 wt% of the total mass of the layered oxide precursor are mixed in proportion to form a positive electrode material precursor; wherein the coating material precursor is boron oxide or boric acid; the layered oxide precursor comprises: sodium carbonate in an amount of 100 wt% to 110 wt% of the stoichiometric amount of the required sodium, lithium carbonate in an amount of 100 wt% to 110 wt% of the stoichiometric amount of the required sodium, oxides of nickel, copper, and manganese, and an oxide or carbonate of M in an amount of the required stoichiometric amount; wherein M is an element for doping and replacing the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of Period IV and Period V;

[0016] The positive electrode material precursor is uniformly mixed by ball milling to obtain precursor powder;

[0017] The precursor powder is placed in a muffle furnace or a tube furnace and heat treated in an air or oxygen atmosphere at 600° C. to 1000° C. for 2 to 24 hours;

[0018] The powder obtained after the heat treatment is ground to obtain the oxide composite positive electrode material with the surface in-situ coated with borate.

[0019] In a third aspect, an embodiment of the present invention provides a method for preparing the oxide composite positive electrode material having in-situ borate coating as described in the first aspect, wherein the method is a spray drying method, comprising:

[0020] A layered oxide precursor and a coating material precursor accounting for 0.1 wt% to 10 wt% of the total mass of the layered oxide precursor are mixed in proportion to form a positive electrode material precursor; wherein the coating material precursor is boron oxide or boric acid; the layered oxide precursor comprises: sodium carbonate or sodium nitrate in an amount of 100 wt% to 110 wt% of the stoichiometric amount of the required sodium, lithium carbonate or lithium sodium nitrate in an amount of 100 wt% to 110 wt% of the stoichiometric amount of the required sodium, oxides or nitrates of nickel, copper, and manganese, and an oxide or carbonate of M in an amount of the required stoichiometric amount; wherein M is an element for doping and replacing the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of Period IV and Period V;

[0021] Adding ethanol or water to the cathode material precursor and stirring evenly to form a slurry;

[0022] spray drying the slurry to obtain a precursor powder;

[0023] The precursor powder is placed in a muffle furnace or a tube furnace and heat treated in an air or oxygen atmosphere at 600° C. to 1000° C. for 2 to 24 hours;

[0024] The powder obtained after the heat treatment is ground to obtain the oxide composite positive electrode material with the surface in-situ coated with borate.

[0025] In a fourth aspect, an embodiment of the present invention provides a method for preparing the oxide composite positive electrode material having in-situ borate coating according to the first aspect, wherein the method is a combustion method, comprising:

[0026] A layered oxide precursor and a coating material precursor accounting for 0.1 wt% to 10 wt% of the total mass of the layered oxide precursor are mixed in proportion to form a positive electrode material precursor; wherein the coating material precursor is boron oxide or boric acid; the layered oxide precursor comprises: sodium nitrate in an amount of 100 wt% to 110 wt% of the stoichiometric amount of the required sodium, lithium nitrate in an amount of 100 wt% to 110 wt% of the stoichiometric amount of the required sodium, nitrates of nickel, copper, and manganese, and nitrates of M in an amount of the required stoichiometric amount; wherein M is an element for doping and replacing the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of Period IV and Period V;

[0027] Adding acetylacetone to the cathode material precursor and stirring evenly to form a slurry;

[0028] Drying the slurry to obtain precursor powder;

[0029] The precursor powder is placed in a muffle furnace or a tube furnace and heat treated in an air or oxygen atmosphere at 600° C. to 1000° C. for 2 to 24 hours;

[0030] The powder obtained after the heat treatment is ground to obtain the oxide composite positive electrode material with the surface in-situ coated with borate.

[0031] In a fifth aspect, an embodiment of the present invention provides a method for preparing the oxide composite positive electrode material having in-situ borate coating according to the first aspect, wherein the method is a sol-gel method, comprising:

[0032] A layered oxide precursor and a coating material precursor accounting for 0.1wt% to 10wt% of the total mass of the layered oxide precursor are mixed in proportion to form a positive electrode material precursor; wherein the coating material precursor is boron oxide or boric acid; the layered oxide precursor includes: a sodium salt with a stoichiometric amount of 100wt% to 110wt% of the required sodium, a lithium salt with a stoichiometric amount of 100wt% to 110wt% of the required sodium, a nitrate or sulfate of nickel, copper, or manganese, and a nitrate or sulfate of a stoichiometric amount of M; the M is an element for doping and replacing the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of the fourth period and the fifth period; the sodium salt includes: one or more of sodium acetate, sodium nitrate, sodium carbonate, or sodium sulfate; the lithium salt includes: one or more of lithium acetate, lithium nitrate, lithium carbonate, or lithium sulfate;

[0033] Stirring at 50°C to 100°C, adding an appropriate amount of chelating agent, and evaporating to dryness to form a precursor gel;

[0034] The precursor gel is placed in a crucible and pre-fired in an air atmosphere at 200° C. to 500° C. for 2 hours;

[0035] The precursor powder is placed in a muffle furnace or a tube furnace and heat treated in an air or oxygen atmosphere at 600° C. to 1000° C. for 2 to 24 hours;

[0036] The powder obtained after the heat treatment is ground to obtain the oxide composite positive electrode material with the surface in-situ coated with borate.

[0037] In a sixth aspect, an embodiment of the present invention provides a method for preparing the oxide composite positive electrode material having in-situ borate coating according to the first aspect, wherein the method is a coprecipitation method, comprising:

[0038] The nitrate of nickel, copper, manganese, lithium and M in the required stoichiometric amounts is dissolved in water in proportion to form a precursor solution; M is an element that is used to dope and replace the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA or Group VIA, and one or more transition metal elements of the fourth period and the fifth period;

[0039] Using a peristaltic pump, the precursor solution is added dropwise to an ammonia solution to generate a precipitate;

[0040] The obtained precipitate is cleaned with deionized water, dried, and then uniformly mixed with sodium carbonate and a coating material precursor accounting for 0.1 wt% to 10 wt% of the total mass of the layered oxide precursor in a stoichiometric ratio to obtain a precursor; the layered oxide precursor includes the sodium carbonate and the nitrates of nickel, copper, manganese, lithium, and M;

[0041] The precursor is placed in a crucible or a porcelain boat and heat-treated in an air or oxygen atmosphere at 600° C. to 1000° C. for 2 to 24 hours;

[0042] The powder obtained after the heat treatment is ground to obtain the oxide composite positive electrode material with the surface in-situ coated with borate.

[0043] In a seventh aspect, an embodiment of the present invention provides a positive electrode sheet for a sodium ion secondary battery, the positive electrode sheet comprising:

[0044] A current collector, a conductive additive and a binder coated on the current collector, and the oxide composite positive electrode material with in-situ borate coating as described in the first aspect.

[0045] In an eighth aspect, an embodiment of the present invention provides a sodium ion secondary battery with the positive electrode sheet described in the seventh aspect.

[0046] In a ninth aspect, an embodiment of the present invention provides a use of a sodium ion secondary battery, wherein the sodium ion secondary battery is used in large-scale energy storage equipment for electric vehicles, solar power generation, wind power generation, smart grid peak regulation, distributed power stations, backup power supplies or communication base stations.

[0047] The oxide composite positive electrode material with in-situ borate coating proposed by the present invention is formed by melting boron oxide or boric acid at a lower temperature and reacting with part of the sodium salt and lithium salt in the positive electrode material precursor to form a chemical formula A x B y O z The lithium borate salt or sodium borate salt uniformly and completely wraps the lithium-containing layered oxide positive electrode. x B y O z After contact with air, it transforms into a needle-like structure, which greatly reduces the residual alkali produced on the surface of the material due to contact with air, significantly improves the stability in air, and the material's electrical conductivity and sodium ion diffusion capacity are higher, the charge transfer impedance is lower, the first charge and discharge efficiency is higher, and the cycle capacity is better. Therefore, the lithium oxide-containing composite positive electrode material with borate in situ coated on the surface has the characteristics of air stability, high capacity and high cycle stability. This material can remain structurally stable when placed in 45% RH-60% RH air for more than 48 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The technical solutions of the embodiments of the present invention are further described in detail below through the accompanying drawings and examples.

[0049] Figure 1 A flow chart of a method for preparing an oxide composite positive electrode material having an in-situ borate-coated surface by a solid-phase method according to an embodiment of the present invention;

[0050] Figure 2 A flow chart of a method for preparing an oxide composite positive electrode material having an in-situ borate-coated surface by a spray drying method according to an embodiment of the present invention;

[0051] Figure 3 A flow chart of a method for preparing an oxide composite positive electrode material having an in-situ borate-coated surface by a combustion method according to an embodiment of the present invention;

[0052] Figure 4 A flow chart of a method for preparing an oxide composite positive electrode material having an in-situ borate-coated surface by a sol-gel method according to an embodiment of the present invention;

[0053] Figure 5 A flow chart of a method for preparing an oxide composite positive electrode material having an in-situ borate-coated surface by a co-precipitation method according to an embodiment of the present invention;

[0054] Figure 6 XRD patterns of oxide composite cathode materials with multiple surfaces in situ coated with borates at different molar percentages of elements provided in an embodiment of the present invention;

[0055] Figure 7 The solid phase synthesis method provided in Example 1 of the present invention is used for the Na 1.0 Li 0.05 Ni 0.33 Cu 0.05 Mn 0.37 Fe 0.1 Ti 0.1 SEM images of O2 materials;

[0056] Figure 8 0.5wt% Li3BO3-Na synthesized by solid phase method provided in Example 1 of the present invention 1.0 Li 0.05 Ni 0.33 Cu 0.05 Mn 0.37 Fe 0.1 Ti 0.1 SEM images of O2 materials;

[0057] Figure 9 A comparison chart of the charge and discharge curves of sodium ion batteries prepared from the two materials described above at 2.0-4.3V provided in Example 1 of the present invention;

[0058] Figure 10 A comparison of the cycle curves of sodium ion batteries prepared from the two materials described above provided in Example 1 of the present invention;

[0059] Figure 11XRD spectra of the oxide composite positive electrode material with in-situ borate coating provided in Example 1 of the present invention before and after being placed in air with a humidity of 55% for 48 hours;

[0060] Figure 12 This is a comparison chart of the 2.0-4.3V charge and discharge curves of sodium ion batteries prepared from two materials of the oxide composite positive electrode material with the surface in situ coated with borate provided in Example 1 of the present invention before and after being placed in air with a humidity of 55% for 48 hours. DETAILED DESCRIPTION

[0061] The present invention will be further described below through the accompanying drawings and specific embodiments, but it should be understood that these embodiments are only used for more detailed description and should not be understood as limiting the present invention in any form, that is, they are not intended to limit the scope of protection of the present invention.

[0062] The embodiment of the present invention provides a layered lithium oxide composite positive electrode material with in-situ borate coating on the surface, air stability, high capacity, and high cycle stability. The chemical formula of the material is: γA x B y O z -Na a Li b Ni c Cu d Mn e M f O 2+β The space group of the layered oxide composite cathode material is P63 / mmc or P63 / mcm or The corresponding structure is P2 phase or O3 phase.

[0063] In the above materials, Li, Ni, Cu, Mn, and M jointly occupy the transition metal ion position in the crystal structure; wherein M is an element that dopes and replaces the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of the fourth period and the fifth period;

[0064] a, b, c, d, e, f, and 2+β are the molar percentages of the corresponding elements, and each component in the general chemical formula satisfies the conservation of charge and stoichiometry; wherein b+c+d+e+f=1, and a+b+2c+2d+4e+mf=2(2+β); 0.67≤a≤1; 0<b≤0.2; 0<c≤0.65; 0<d≤0.28; 0<e≤0.65; -0.05≤β≤0.05; m is the valence state of M;

[0065] A x B y O zFor Na a Li b Ni c Cu d Mn e M f O 2+β The coating layer is generated in situ on the surface by the coating material precursor and the Na a Li b Ni c Cu d Mn e M f O 2+β The layered oxide precursor is generated during the sintering process; the coating material precursor is boron oxide or boric acid; the molten coating material precursor forms an A with a portion of the sodium salt and / or lithium salt in the layered oxide precursor. x B y O z . γ is the mass fraction of the coating material precursor to the layered oxide precursor, 0.1wt%≤γ≤10wt%; A is Li and / or Na, 0<x≤3, 0<y≤10, 0<z≤15. The coating layer has a special morphology and is needle-shaped after contact with air. The coating layer is smoothly attached to the surface of the material before contact with air. Since the material will inevitably come into contact with air during the process of making the electrode, the morphology of the coating layer is transformed into a needle shape, the residual alkali on the surface of the material is greatly reduced, and the stability in the air is significantly improved. The material has higher electrical conductivity and sodium ion diffusion capacity, lower charge transfer impedance, higher first charge and discharge efficiency, better cycle capacity, and especially longer cycle life.

[0066] The preparation method of the oxide composite positive electrode material with in-situ borate-coated surface of the present invention is compatible with a variety of process methods, which are described one by one below.

[0067] Oxide composite cathode materials with in-situ borate coating on the surface can be prepared by solid phase method. The main steps are as follows: Figure 1 Shown, including:

[0068] Step 110: mixing a layered oxide precursor and a coating material precursor accounting for 0.1 wt% to 10 wt% of the total mass of the layered oxide precursor in proportion to form a positive electrode material precursor;

[0069] The coating material precursor is boron oxide or boric acid; the layered oxide precursor includes: sodium carbonate in an amount of 100 wt% to 110 wt% of the required sodium, lithium carbonate in an amount of 100 wt% to 110 wt% of the required sodium, oxides of nickel, copper, and manganese, and an oxide or carbonate of M in an amount of stoichiometric amount; M is an element for doping and replacing the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of Period IV and Period V.

[0070] Step 120 , uniformly mixing the cathode material precursor by ball milling to obtain precursor powder;

[0071] Step 130 , placing the precursor powder in a muffle furnace or a tube furnace, and heat treating it in an air or oxygen atmosphere at 600° C. to 1000° C. for 2 to 24 hours;

[0072] Step 140 , grinding the powder obtained after the heat treatment to obtain an oxide composite positive electrode material with a surface in-situ coated borate.

[0073] Oxide composite cathode materials with in-situ borate coating on the surface can be prepared by spray drying. The main steps are as follows: Figure 2 Shown, including:

[0074] Step 210: Mixing the layered oxide precursor and the coating material precursor accounting for 0.1 wt% to 10 wt% of the total mass of the layered oxide precursor in proportion to form a positive electrode material precursor;

[0075] The coating material precursor is boron oxide or boric acid; the layered oxide precursor includes: sodium carbonate or sodium nitrate in an amount of 100wt% to 110wt% of the required sodium stoichiometry, lithium carbonate in an amount of 100wt% to 110wt% of the required sodium stoichiometry, oxides or nitrates of nickel, copper, and manganese, and oxides or carbonates of M in an amount of the required stoichiometry; M is an element that is doped to replace the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of the fourth and fifth periods;

[0076] Step 220 , adding ethanol or water to the cathode material precursor and stirring the mixture to form a slurry;

[0077] Step 230, spray drying the slurry to obtain a precursor powder;

[0078] Step 240 , placing the precursor powder in a muffle furnace or a tube furnace, and heat treating it in an air or oxygen atmosphere at 600° C. to 1000° C. for 2 to 24 hours;

[0079] Step 250 , grinding the powder obtained after the heat treatment to obtain an oxide composite positive electrode material with a surface in-situ coated borate.

[0080] Oxide composite cathode materials with in-situ borate coating on the surface can be prepared by combustion method. The main steps are as follows: Figure 3 Shown, including:

[0081] Step 310 , mixing a layered oxide precursor and a coating material precursor accounting for 0.1 wt % to 10 wt % of the total mass of the layered oxide precursor in proportion to form a positive electrode material precursor;

[0082] The coating material precursor is boron oxide or boric acid; the layered oxide precursor includes: sodium nitrate in an amount of 100wt% to 110wt% of the required sodium, lithium nitrate in an amount of 100wt% to 110wt% of the required sodium, and nitrates of nickel, copper, and manganese; M is an element for doping and replacing the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of Period IV and Period V.

[0083] Step 320 , adding acetylacetone to the cathode material precursor and stirring uniformly to form a slurry;

[0084] Step 330, drying the slurry to obtain a precursor powder;

[0085] Specifically, the drying is preferably performed at 80°C.

[0086] Step 340 , placing the precursor powder in a muffle furnace or a tube furnace, and heat treating it in an air or oxygen atmosphere at 600° C. to 1000° C. for 2 to 24 hours;

[0087] Step 350 , grinding the powder obtained after the heat treatment to obtain an oxide composite positive electrode material with a surface in-situ coated borate.

[0088] Oxide composite cathode materials with in-situ borate coating on the surface can be prepared by the sol-gel method. The main steps are as follows: Figure 4 Shown, including:

[0089] Step 410 , mixing a layered oxide precursor and a coating material precursor accounting for 0.1 wt % to 10 wt % of the total mass of the layered oxide precursor in proportion to form a positive electrode material precursor;

[0090] The coating material precursor is boron oxide or boric acid; the layered oxide precursor includes: a sodium salt having a stoichiometric ratio of 100wt% to 110wt% of the required sodium, a lithium salt having a stoichiometric ratio of 100wt% to 110wt% of the required sodium, and nitrates or sulfates of nickel, copper, and manganese; M is an element for doping and replacing the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of the fourth and fifth periods; the sodium salt includes: one or more of sodium acetate, sodium nitrate, sodium carbonate, or sodium sulfate; the lithium salt includes: one or more of lithium acetate, lithium nitrate, lithium carbonate, or lithium sulfate;

[0091] Step 420 , stirring at 50° C. to 100° C., adding an appropriate amount of a chelating agent, and evaporating to dryness to form a precursor gel;

[0092] Step 430 , placing the precursor gel in a crucible and pre-firing it in an air atmosphere at 200° C. to 500° C. for 2 hours;

[0093] Step 440 , placing the precursor powder in a muffle furnace or a tube furnace, and heat treating it in an air or oxygen atmosphere at 600° C. to 1000° C. for 2 to 24 hours;

[0094] Step 450 , grinding the powder obtained after the heat treatment to obtain an oxide composite positive electrode material with a surface in-situ coated borate.

[0095] Oxide composite cathode materials with in-situ borate coating on the surface can be prepared by co-precipitation method. The main steps are as follows: Figure 5 Shown, including:

[0096] Step 510 , dissolving nickel, copper, manganese, lithium and M nitrates in required stoichiometric amounts in water in proportion to form a precursor solution;

[0097] Wherein, M is an element that dopes and replaces the transition metal site, including one or more non-metallic elements of Group IIIA, Group IV, Group VA or Group VIA, and one or more transition metal elements of the fourth period and the fifth period;

[0098] Step 520 , using a peristaltic pump to dropwise add the precursor solution into the ammonia solution to generate a precipitate;

[0099] Step 530 , washing the obtained precipitate with deionized water, drying it, and then uniformly mixing the precipitate with sodium carbonate and a coating material precursor accounting for 0.1 wt % to 10 wt % of the total mass of the layered oxide precursor in a stoichiometric ratio to obtain a precursor;

[0100] The layered oxide precursors include sodium carbonate and nitrates of nickel, copper, manganese, lithium, and M;

[0101] Step 540 , placing the precursor in a crucible or a porcelain boat, and heat treating it in an air or oxygen atmosphere at 600° C. to 1000° C. for 2 to 24 hours;

[0102] Step 550 , grinding the powder obtained after the heat treatment to obtain an oxide composite positive electrode material with a surface in-situ coated borate.

[0103] The above preparation methods can be used to prepare the layered lithium-containing oxide composite cathode material with an in-situ borate surface coating as described in the above examples. The method provided in this example is simple and easy to implement, and the elements contained, such as sodium, lithium, nickel, copper, and manganese, are all non-toxic and safe elements with high abundance in the Earth's crust. Therefore, the manufacturing cost is low, the materials used are safe and non-toxic, and it is suitable for large-scale manufacturing applications.

[0104] The oxide composite positive electrode material with a surface in-situ coated borate of the present invention was found in a half-cell test to have not only high mass specific capacity and specific energy, with a specific capacity 1.5 to 2 times that of ordinary sodium ion battery positive electrode materials, but also good cycle life, and great practical value. Sodium ion batteries using the oxide composite positive electrode material with a surface in-situ coated borate of the present invention can be used in large-scale energy storage equipment for electric vehicles, solar power generation, wind power generation, smart grid peak regulation, distributed power stations, backup power supplies or communication base stations.

[0105] To better understand the technical solutions provided by the present invention, the following uses a number of specific examples to illustrate the specific process of preparing an oxide composite positive electrode material having an in-situ surface-coated borate by applying the several methods provided in the above embodiments of the present invention, as well as the method and battery characteristics of applying the same to sodium ion secondary batteries.

[0106] Example 1

[0107] In this embodiment, a lithium-containing layered oxide composite positive electrode material with in-situ surface-coated borate is prepared by a solid phase method, and a lithium-containing layered oxide material is prepared by the same method for comparison.

[0108] The preparation process of the lithium-containing layered oxide material of this example includes:

[0109] Na2CO3 (analytical pure), Li2CO3 (analytical pure), NiO (analytical pure), CuO (analytical pure), MnO2 (analytical pure), Fe2O3 (analytical pure), and TiO2 (analytical pure) were mixed in the required stoichiometric ratio; the mixture was ground in an agate mortar for half an hour to obtain a precursor; the precursor was transferred to an Al2O3 crucible and treated in an oxygen atmosphere at 900°C in a muffle furnace for 15 hours to obtain a black powder layered oxide material Na 1.0 Li 0.05 Ni 0.33Cu 0.05 Mn 0.37 Fe 0.1 Ti 0.1 O2, its XRD pattern is shown in Figure 6 . SEM images are shown in Figure 7 .

[0110] The preparation process of the lithium-containing layered oxide composite cathode material with in-situ borate coating on the surface includes:

[0111] Na2CO3 (analytical pure), Li2CO3 (analytical pure), NiO (analytical pure), CuO (analytical pure), MnO2 (analytical pure), Fe2O3 (analytical pure), TiO2 (analytical pure), and B2O3 (analytical pure) were mixed in the required stoichiometric ratio; the mixture was ground in an agate mortar for half an hour to obtain a precursor; the precursor was transferred to an Al2O3 crucible and treated in an oxygen atmosphere at 900°C in a muffle furnace for 15 hours to obtain a black powder layered oxide material 0.5wt% Li3BO3-Na 1.0 Li 0.05 Ni 0.33 Cu 0.05 Mn 0.37 Fe 0.1 Ti 0.1 O2,

[0112] Its XRD pattern can be found in Figure 6 . SEM images are shown in Figure 8 .

[0113] From the XRD pattern, Na 1.0 Li 0.05 Ni 0.33 Cu 0.05 Mn 0.37 Fe 0.1 Ti 0.1 O2 with 0.5wt%Li3BO3-Na 1.0 Li 0.05 Ni 0.33 Cu 0.05 Mn 0.37 Fe 0.1 Ti 0.1 The crystal structure of O2 is an oxide with an O3 phase layered structure.

[0114] from Figure 7 Figure 8 It can be seen from the two SEM images that the original material Na 1.0 Li 0.05 Ni 0.33 Cu 0.05 Mn 0.37 Fe 0.1 Ti 0.1O2 contains a lot of residual alkali in the form of blocks, which will cause the slurry to agglomerate, making it difficult to make subsequent batteries. It will also cause the conductivity and sodium ion diffusion capacity of the material to decrease, the charge transfer impedance to increase, the initial charge and discharge efficiency to decrease, and the cycle stability of the battery to a certain extent. The modified composite positive electrode material 0.5wt% Li3BO3-Na 1.0 Li 0.05 Ni 0.33 Cu 0.05 Mn 0.3 7Fe 0.1 Ti 0.1 The coating layer on the surface of O2 has a needle-like structure, which inhibits the formation of residual alkali on the surface. The slurry made with this material is smooth, which facilitates the production of batteries and greatly improves the cycle stability of the material.

[0115] The two layered oxide materials prepared above were used as active materials of battery positive electrode materials in the preparation of sodium ion batteries for further comparison. The specific steps were as follows: 1.0 Li 0.05 Ni 0.33 Cu 0.05 Mn 0.37 Fe 0.1 Ti 0.1 O2 with 0.5wt% A x B y O z -Na 1.0 Li 0.05 Ni 0.33 Cu 0.05 Mn 0.37 Fe 0.1 Ti 0.1 O2 powder was mixed with acetylene black and binder polyvinylidene fluoride (PVDF) in a mass ratio of 80:10:10, and an appropriate amount of N-methylpyrrolidone (NMP) solution was added. The mixture was ground in a dry environment at room temperature to form a slurry. The slurry was then evenly coated on the current collector aluminum foil and dried under an infrared lamp before being cut into (8×8) mm 2 The electrode was dried at 110°C under vacuum for 10 hours and then transferred to a glove box for later use.

[0116] The simulated battery was assembled in an Ar atmosphere glove box, using sodium metal as the counter electrode and 1M NaClO4 / diethyl carbonate (DEC) solution as the electrolyte to form a CR2032 button cell. The constant current charge and discharge mode was used, and the charge and discharge tests were conducted at C / 10 and C / 2 current densities. The discharge cut-off voltage was 2.0V and the charge cut-off voltage was 4.3V. The charge and discharge test results at 2.0-4.3V are shown in Figure 2. Figure 9 , the battery cycle curve is shown in Figure 10 , it can be seen that although the Na 1.0 Li 0.05 Ni 0.33 Cu 0.05 Mn 0.37 Fe 0.1 Ti 0.1 The first-cycle discharge capacity of the O2 material reached 178.2 mAh / g, while the positive electrode material in situ coated with borate (represented as in-situ coated material in the figure, the same below) achieved a higher first-cycle coulombic efficiency and higher cycle stability.

[0117] In addition, we also compared the surface in-situ borate-coated oxide composite positive electrode material prepared in Example 1 before and after being placed in air with a humidity of 55% for 48 hours. Figure 11 To compare the XRD spectra before and after exposure to humid air, the layered oxide material obtained before and after exposure to humid air was used as the active material for the positive electrode material of a sodium ion battery and subjected to electrochemical charge and discharge tests. The preparation process and test method were the same as in Example 1, and the test voltage range was 2.0 to 4.3 V. Figure 12 According to the charge and discharge test results, judging from the charge and discharge curve and the reversible specific capacity, the effect of air with a humidity of 55% on the material is relatively small, which further proves that the presence of the coating layer can improve the air stability of the material.

[0118] Example 2

[0119] In this embodiment, a lithium-containing layered oxide composite positive electrode material with in-situ surface-coated borate is prepared by a solid phase method, and a lithium-containing layered oxide material is prepared by the same method for comparison.

[0120] The preparation process of the lithium-containing layered oxide material of this example includes:

[0121] Na2CO3 (analytical pure), Li2CO3 (analytical pure), NiO (analytical pure), CuO (analytical pure), MnO2 (analytical pure), and ZrO2 (analytical pure) were mixed in the required stoichiometric ratio; the mixture was ground in an agate mortar for half an hour to obtain a precursor; the precursor was transferred to an Al2O3 crucible and treated in an oxygen atmosphere at 900°C in a muffle furnace for 15 hours to obtain a black powder layered oxide material Na 0.67 Li 0.02 Ni 0.18 Cu 0.13 Mn 0.47 Zr 0.2 O2, its XRD pattern is shown in Figure 6 The preparation process of the lithium-containing layered oxide composite cathode material with in-situ borate coating on the surface includes:

[0122] Na2CO3 (analytical pure), Li2CO3 (analytical pure), NiO (analytical pure), CuO (analytical pure), MnO2 (analytical pure), ZrO2 (analytical pure), and B2O3 (analytical pure) were mixed in the required stoichiometric ratio; the mixture was ground in an agate mortar for half an hour to obtain a precursor; the precursor was transferred to an Al2O3 crucible and treated in an oxygen atmosphere at 900°C in a muffle furnace for 15 hours to obtain a black powder layered oxide material 0.1wt% Na3BO3-Na 0.67 Li 0.02 Ni 0.18 Cu 0.13 Mn 0.47 Zr 0.2 O2, its XRD pattern see Figure 6 .

[0123] From the XRD pattern, Na 0.67 Li 0.02 Ni 0.18 Cu 0.13 Mn 0.47 Zr 0.2 O2 with 0.1wt% Na3BO3-Na 0.67 Li 0.02 Ni 0.18 Cu 0.13 Mn 0.47 Zr 0.2 The crystal structure of O2 is a P2 phase layered oxide.

[0124] The layered oxide material prepared above was used as the active material for the positive electrode of a sodium-ion battery and subjected to electrochemical charge-discharge testing. The preparation process and testing methods were the same as in Example 1. The test voltage range was 2.0 to 4.3 V, and the reversible specific capacity of the material is shown in Table 1.

[0125] Example 3

[0126] In this embodiment, a lithium-containing layered oxide composite positive electrode material with in-situ surface-coated borate is prepared by a solid phase method, and a lithium-containing layered oxide material is prepared by the same method for comparison.

[0127] The preparation process of the lithium-containing layered oxide material of this example includes:

[0128] Na2CO3 (analytical pure), Li2CO3 (analytical pure), NiO (analytical pure), CuO (analytical pure), and MnO2 (analytical pure) were mixed in the required stoichiometric ratio; the mixture was ground in an agate mortar for half an hour to obtain a precursor; the precursor was transferred to an Al2O3 crucible and treated in an oxygen atmosphere at 900°C in a muffle furnace for 15 hours to obtain a black powder layered oxide material Na 0.76 Li0.03 Ni 0.15 Cu 0.18 Mn 0.64 O2, its XRD pattern is shown in Figure 6 .

[0129] The preparation process of the lithium-containing layered oxide composite positive electrode material with in-situ borate coating on the surface includes: mixing Na2CO3 (analytical grade), Li2CO3 (analytical grade), NiO (analytical grade), CuO (analytical grade), MnO2 (analytical grade), and B2O3 (analytical grade) in a desired stoichiometric ratio; grinding the mixture in an agate mortar for half an hour to obtain a precursor; transferring the precursor to an Al2O3 porcelain boat and treating the mixture in a tube furnace at 900°C in an air atmosphere for 15 hours to obtain a black powder layered oxide material 1.0 wt% LiNaB8O 13 -Na 0.76 Li 0.03 Ni 0.15 Cu 0.18 Mn 0.64 O2, its XRD pattern see Figure 6 .

[0130] From the XRD pattern, Na 0.76 Li 0.03 Ni 0.15 Cu 0.18 Mn 0.64 O2 with 1.0wt% LiNaB8O 13 -Na 0.76 Li 0.03 Ni 0.15 Cu 0.18 Mn 0.64 The crystal structure of O2 is a P2 phase layered oxide.

[0131] The layered oxide material prepared above was used as the active material for the positive electrode of a sodium-ion battery and subjected to electrochemical charge-discharge testing. The preparation process and testing methods were the same as in Example 1. The test voltage range was 2.0 to 4.3 V, and the reversible specific capacity of the material is shown in Table 1.

[0132] Example 4

[0133] In this embodiment, a lithium-containing layered oxide composite positive electrode material with in-situ surface-coated borate is prepared by a solid phase method, and a lithium-containing layered oxide material is prepared by the same method for comparison.

[0134] The preparation process of the lithium-containing layered oxide material of this example includes:

[0135] Na2CO3 (analytical pure), Li2CO3 (analytical pure), NiO (analytical pure), CuO (analytical pure), MnO2 (analytical pure), and titanium dioxide (analytical pure) were mixed in the required stoichiometric ratio; the mixture was ground in an agate mortar for half an hour to obtain a precursor; the precursor was transferred to an Al2O3 crucible and treated in an oxygen atmosphere at 900°C in a muffle furnace for 15 hours to obtain a black powder layered oxide material Na 0.83 Li 0.06 Ni 0.20 Cu 0.13 Mn 0.56 Ti 0.05 O2, its XRD pattern is shown in Figure 6 .

[0136] The preparation process of the lithium-containing layered oxide composite positive electrode material with surface in-situ borate coating includes: mixing Na2CO3 (analytical pure), Li2CO3 (analytical pure), NiO (analytical pure), CuO (analytical pure), MnO2 (analytical pure), titanium dioxide (analytical pure), and B2O3 (analytical pure) in a desired stoichiometric ratio; grinding the mixture in an agate mortar for half an hour to obtain a precursor; transferring the precursor to an Al2O3 porcelain boat, and treating the mixture in an oxygen atmosphere at 900°C in a tube furnace for 15 hours to obtain a black powder layered oxide material 5.0wt% Li 1.5 Na 0.5 B4O7-Na 0.83 Li 0.06 Ni 0.20 Cu 0.13 Mn 0.56 Ti 0.05 O2, its XRD pattern see Figure 6 .

[0137] From the XRD pattern, Na 0.83 Li 0.06 Ni 0.20 Cu 0.13 Mn 0.56 Ti 0.05 O2 with 5.0wt%Li 1.5 Na 0.5 B4O7-Na 0.83 Li 0.06 Ni 0.20 Cu 0.13 Mn 0.56 Ti 0.05 The crystal structure of O2 is an oxide with an O3-like structure.

[0138] The layered oxide material prepared above was used as the active material for the positive electrode of a sodium-ion battery and subjected to electrochemical charge-discharge testing. The preparation process and testing methods were the same as in Example 1. The test voltage range was 2.0 to 4.3 V, and the reversible specific capacity of the material is shown in Table 1.

[0139] Example 5

[0140] In this embodiment, a lithium-containing layered oxide composite positive electrode material with in-situ surface-coated borate is prepared by a solid phase method, and a lithium-containing layered oxide material is prepared by the same method for comparison.

[0141] The preparation process of the lithium-containing layered oxide material of this example includes:

[0142] Na2CO3 (analytical pure), Li2CO3 (analytical pure), NiO (analytical pure), CuO (analytical pure), MnO2 (analytical pure), and TiO2 (analytical pure) were mixed in the required stoichiometric ratio; the mixture was ground in an agate mortar for half an hour to obtain a precursor; the precursor was transferred to an Al2O3 crucible and treated in an oxygen atmosphere at 900°C in a muffle furnace for 15 hours to obtain a black powder layered oxide material Na 1.0 Li 0.02 Ni 0.4 Cu 0.05 Mn 0.4 Ti 0.09 Fe 0.04 O2, its XRD pattern is shown in Figure 6 .

[0143] The preparation process of the lithium-containing layered oxide composite cathode material with in-situ borate coating on the surface includes:

[0144] Na2CO3 (analytical pure), Li2CO3 (analytical pure), NiO (analytical pure), CuO (analytical pure), MnO2 (analytical pure), alumina (analytical pure), and B2O3 (analytical pure) were mixed in the required stoichiometric ratio; the mixture was ground in an agate mortar for half an hour to obtain a precursor; the precursor was transferred to an Al2O3 porcelain boat and treated in an oxygen atmosphere at 900°C in a tube furnace for 15 hours to obtain a black powder layered oxide material 10wt% Li 0.2 Na 0.8 BO2-Na 1.0 Li 0.02 Ni 0.4 Cu 0.05 Mn 0.4 Ti 0.09 Fe 0.04 O2, its XRD pattern see Figure 6 .

[0145] From the XRD pattern, Na 1.0 Li 0.02 Ni 0.4 Cu 0.05 Mn 0.4 Ti 0.09 Fe 0.04 O2 with 10wt%Li 0.2 Na 0.8 BO2-Na 1.0 Li 0.02 Ni 0.4 Cu 0.05 Mn 0.4 Ti 0.09 Fe 0.04 The crystal structure of O2 is an oxide with an O3-like structure.

[0146] The layered oxide material prepared above was used as the active material for the positive electrode of a sodium-ion battery and subjected to electrochemical charge-discharge testing. The preparation process and testing methods were the same as in Example 1. The test voltage range was 2.0 to 4.3 V, and the reversible specific capacity of the material is shown in Table 1.

[0147]

[0148]

[0149] Table 1

[0150] By comparison, it can be seen that the composite positive electrode material with an in-situ borate coating structure obtained by the in-situ coating method of the present invention not only has high capacity, but also significantly improved cycle capacity retention. Because the coating layer morphology changes from the original smooth surface to needle-shaped after the material comes into contact with air, the residual alkali on the surface of the material is greatly reduced, and the stability in air is significantly improved. The material has higher electrical conductivity and sodium ion diffusion capacity, lower charge transfer impedance, higher initial charge and discharge efficiency, more cycle capacity, and especially longer cycle life.

[0151] Although the above embodiments only describe the specific implementation of the present invention in detail using the solid-phase method as an example, the preparation methods of the spray drying method, combustion method, sol-gel method and co-precipitation method provided above are all methods well known to those skilled in the art. Those skilled in the art can implement the technical solution of the present invention without any creative work based on the preparation process steps of the above preparation methods provided by the present invention.

[0152] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An oxide composite positive electrode material with in-situ borate coating, characterized in that: The general chemical formula of the material is: γA x B y O z -Na a Li b Ni c Cu d Mn e M f O 2+β ; In the material, Li, Ni, Cu, Mn, and M jointly occupy the transition metal ion position in the crystal structure; wherein M is an element that dopes and replaces the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of the fourth period and the fifth period; a, b, c, d, e, f, and 2+β are the molar percentages of the corresponding elements, and each component in the general chemical formula satisfies charge conservation and stoichiometric conservation; wherein b+c+d+e+f=1, and a+b+2c+2d+4e+mf=2(2+β); 0.67≤a≤1; 0<b≤0.2; 0<c≤0.65; 0<d≤0.28; 0<e≤0.65; -0.05≤β≤0.05; m is the valence state of M; The space group of the layered oxide composite cathode material is P63 / mmc or P63 / mcm or The corresponding structure is P2 phase or O3 phase; The A x B y O z For Na a Li b Ni c Cu d Mn e M f O 2+β The needle-like structure coating layer is generated in situ on the surface by the coating material precursor and the Na a Li b Ni c Cu d Mn e M f O 2+β The layered oxide precursor is generated during the sintering process; wherein γ is the mass fraction of the coating material precursor to the layered oxide precursor, 0.1wt%≤γ≤10wt%; A is Li and / or Na, 0<x≤3, 0<y≤10, 0<z≤15.

2. The oxide composite positive electrode material with in-situ borate coating according to claim 1, characterized in that: The coating material precursor is boron oxide or boric acid; the molten coating material precursor forms an A with a portion of the sodium salt and / or lithium salt in the layered oxide precursor. x B y O z .

3. A method for preparing an oxide composite positive electrode material having in-situ borate coating according to claim 1 or 2, characterized in that: The method is a solid phase method, comprising: A layered oxide precursor and a coating material precursor accounting for 0.1 wt% to 10 wt% of the total mass of the layered oxide precursor are mixed in proportion to form a positive electrode material precursor; wherein the coating material precursor is boron oxide or boric acid; the layered oxide precursor comprises: sodium carbonate in an amount of 100 wt% to 110 wt% of the stoichiometric amount of the required sodium, lithium carbonate in an amount of 100 wt% to 110 wt% of the stoichiometric amount of the required sodium, oxides of nickel, copper, and manganese, and an oxide or carbonate of M in an amount of the required stoichiometric amount; wherein M is an element for doping and replacing the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of Period IV and Period V; The positive electrode material precursor is uniformly mixed by ball milling to obtain precursor powder; The precursor powder is placed in a muffle furnace or a tube furnace and heat treated in an air or oxygen atmosphere at 600° C. to 1000° C. for 2 to 24 hours; The powder obtained after the heat treatment is ground to obtain the oxide composite positive electrode material with in-situ borate coating.

4. A method for preparing an oxide composite positive electrode material having in-situ borate coating according to claim 1 or 2, characterized in that: The method is a spray drying method, comprising: A layered oxide precursor and a coating material precursor accounting for 0.1 wt% to 10 wt% of the total mass of the layered oxide precursor are mixed in proportion to form a positive electrode material precursor; wherein the coating material precursor is boron oxide or boric acid; the layered oxide precursor comprises: sodium carbonate or sodium nitrate in an amount of 100 wt% to 110 wt% of the stoichiometric amount of the required sodium, lithium carbonate in an amount of 100 wt% to 110 wt% of the stoichiometric amount of the required sodium, oxides or nitrates of nickel, copper, and manganese, and an oxide or carbonate of a stoichiometric amount of M; wherein M is an element for doping and replacing the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of Period IV and Period V; Adding ethanol or water to the cathode material precursor and stirring evenly to form a slurry; spray drying the slurry to obtain a precursor powder; The precursor powder is placed in a muffle furnace or a tube furnace and heat treated in an air or oxygen atmosphere at 600° C. to 1000° C. for 2 to 24 hours; The powder obtained after the heat treatment is ground to obtain the oxide composite positive electrode material with the surface in-situ coated with borate.

5. A method for preparing an oxide composite positive electrode material with in-situ borate coating according to claim 1 or 2, characterized in that: The method is a combustion method, comprising: A layered oxide precursor and a coating material precursor accounting for 0.1 wt% to 10 wt% of the total mass of the layered oxide precursor are mixed in proportion to form a positive electrode material precursor; wherein the coating material precursor is boron oxide or boric acid; the layered oxide precursor comprises: sodium nitrate in an amount of 100 wt% to 110 wt% of the stoichiometric amount of the required sodium, lithium nitrate in an amount of 100 wt% to 110 wt% of the stoichiometric amount of the required sodium, nitrates of nickel, copper, and manganese, and nitrates of M in an amount of the required stoichiometric amount; wherein M is an element for doping and replacing the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of Period IV and Period V; Adding acetylacetone to the cathode material precursor and stirring evenly to form a slurry; Drying the slurry to obtain precursor powder; The precursor powder is placed in a muffle furnace or a tube furnace and heat treated in an air or oxygen atmosphere at 600° C. to 1000° C. for 2 to 24 hours; The powder obtained after the heat treatment is ground to obtain the oxide composite positive electrode material with the surface in-situ coated with borate.

6. A method for preparing an oxide composite positive electrode material with in-situ borate coating according to claim 1 or 2, characterized in that: The method is a sol-gel method, comprising: A layered oxide precursor and a coating material precursor accounting for 0.1wt% to 10wt% of the total mass of the layered oxide precursor are mixed in proportion to form a positive electrode material precursor; wherein the coating material precursor is boron oxide or boric acid; the layered oxide precursor includes: a sodium salt with a stoichiometric amount of 100wt% to 110wt% of the required sodium, a lithium salt with a stoichiometric amount of 100wt% to 110wt% of the required sodium, a nitrate or sulfate of nickel, copper, or manganese, and a nitrate or sulfate of a stoichiometric amount of M; the M is an element for doping and replacing the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA, or Group VIA, and one or more transition metal elements of the fourth period and the fifth period; the sodium salt includes: one or more of sodium acetate, sodium nitrate, sodium carbonate, or sodium sulfate; the lithium salt includes: one or more of lithium acetate, lithium nitrate, lithium carbonate, or lithium sulfate; Stirring at 50°C to 100°C, adding an appropriate amount of chelating agent, and evaporating to dryness to form a precursor gel; The precursor gel is placed in a crucible and pre-fired in an air atmosphere at 200° C. to 500° C. for 2 hours; The precursor powder is placed in a muffle furnace or a tube furnace and heat treated in an air or oxygen atmosphere at 600°C to 1000°C for 2 to 24 hours; The powder obtained after the heat treatment is ground to obtain the oxide composite positive electrode material with the surface in-situ coated with borate.

7. A method for preparing an oxide composite positive electrode material with in-situ borate coating according to claim 1 or 2, characterized in that: The method is a co-precipitation method, comprising: The nitrate of nickel, copper, manganese, lithium and M in the required stoichiometric amounts is dissolved in water in proportion to form a precursor solution; M is an element that is used to dope and replace the transition metal position, including one or more non-metallic elements of Group IIIA, Group IV, Group VA or Group VIA, and one or more transition metal elements of the fourth period and the fifth period; Using a peristaltic pump, the precursor solution is added dropwise to an ammonia solution to generate a precipitate; The obtained precipitate is cleaned with deionized water, dried, and then uniformly mixed with sodium carbonate and a coating material precursor accounting for 0.1 wt% to 10 wt% of the total mass of the layered oxide precursor in a stoichiometric ratio to obtain a precursor; the layered oxide precursor includes the sodium carbonate and the nitrates of nickel, copper, manganese, lithium, and M; The precursor is placed in a crucible or a porcelain boat and heat-treated in an air or oxygen atmosphere at 600° C. to 1000° C. for 2 to 24 hours; The powder obtained after the heat treatment is ground to obtain the oxide composite positive electrode material with the surface in-situ coated with borate.

8. A positive electrode plate for a sodium ion secondary battery, characterized in that: The positive electrode plate comprises: A current collector, a conductive additive and a binder coated on the current collector, and the oxide composite positive electrode material with in-situ borate coating according to claim 1 or 2.

9. A sodium ion secondary battery comprising the positive electrode sheet according to claim 8.

10. Use of the sodium ion secondary battery according to claim 9, characterized in that: The sodium ion secondary battery is used for large-scale energy storage equipment in electric vehicles, solar power generation, wind power generation, smart grid peak regulation, distributed power stations, backup power supplies or communication base stations.

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