Sodium-ion battery positive electrode active material, positive electrode and preparation method and application thereof

Abstract

The application provides a sodium ion battery positive electrode active material, a positive electrode and a preparation method and application thereof, wherein the sodium ion battery positive electrode active material comprises a sodium ion layered transition metal oxide and a first material, and the first material comprises at least one of sodium carbonate and sodium bicarbonate. The sodium ion battery positive electrode active material provided by the application achieves the purposes of reducing residual alkali and pre-supplementing sodium when used in a positive electrode, and improves the use performance of the sodium ion battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a sodium-ion battery positive electrode active material, a positive electrode and a preparation method and application thereof. BACKGROUND

[0002] Sodium-ion batteries are considered an important potential technology for large-scale energy storage due to their advantages of wide distribution of raw materials, high abundance, low cost and good safety. When a sodium-ion battery is charged for the first time, the sodium ions released from the positive electrode will react at the negative electrode to form a solid electrolyte interface film (SEI film) or other side reactions, causing loss of active sodium ions, resulting in performance loss of the sodium-ion battery and affecting the use of the sodium-ion battery. SUMMARY

[0003] Therefore, the present application provides a sodium-ion battery positive electrode active material, a positive electrode and a preparation method and application thereof. The sodium-ion battery positive electrode active material provided by the present application achieves the purpose of pre-supplementing sodium and reducing residual alkali when used in a positive electrode, thereby improving the use performance of the sodium-ion battery.

[0004] In a first aspect, the present application provides a sodium-ion battery positive electrode active material, comprising a sodium-ion layered transition metal oxide and a first material, wherein the first material comprises at least one of sodium carbonate and sodium bicarbonate.

[0005] Optionally, the molar ratio of sodium elements in the sodium-ion layered transition metal oxide to sodium elements in the first material is 3.3-20.

[0006] Optionally, the first material further comprises at least one of sodium hydroxide and sodium oxide.

[0007] Optionally, the mass content of the sodium-ion layered transition metal oxide in the sodium-ion battery positive electrode active material is 81.49%-97.67%, and the mass content of the first material is 2.33%-18.51%.

[0008] Optionally, the sodium-ion layered transition metal oxide is Na x Tm y O2, wherein 0

[0009] In a second aspect, the present application provides a preparation method of a sodium-ion battery positive electrode active material, comprising:

[0010] The sodium-containing compound and the transition metal source are mixed, and after sintering, a sodium-ion battery positive electrode active material is obtained, the sodium-ion battery positive electrode active material comprising a sodium-ion layered transition metal oxide and the first material, the first material comprising at least one of sodium carbonate and sodium bicarbonate.

[0011] Optionally, the sodium-ion layered transition metal oxide is Na x Tm y O2, wherein 0 < x ≤ 1, 0 < y ≤ 1, Tm is a transition metal element, and when the sodium-containing compound and the transition metal source are mixed, the molar ratio of sodium elements in the sodium-containing compound to transition metal elements in the transition metal source is 1.05x:y to 1.3x:y.

[0012] Optionally, the sintering temperature is 200-1000℃, and the time is 4-36h.

[0013] Optionally, the transition metal source comprises at least one of a transition metal oxide and a transition metal hydroxide.

[0014] In a third aspect, the present application provides a preparation method of a positive electrode, comprising:

[0015] The sodium-ion battery positive electrode active material of the first aspect or the sodium-ion battery positive electrode active material prepared by the preparation method of the second aspect is mixed with a binder and an acid agent to obtain a positive electrode slurry.

[0016] The positive electrode slurry is coated on the surface of a positive electrode current collector, and after drying, a positive electrode is obtained.

[0017] Optionally, the mass ratio of the acid agent in the positive electrode slurry to the solid mass in the positive electrode slurry is 0.01%-10%.

[0018] Optionally, the acid agent comprises at least one of oxalic acid, acetic acid, boric acid, salicylic acid, citric acid, ascorbic acid, formic acid, propionic acid, and malonic acid.

[0019] In a fourth aspect, the present application provides a positive electrode, comprising a positive electrode current collector and a positive electrode active material layer arranged on the surface of the positive electrode current collector, wherein the positive electrode active material layer is made of the sodium-ion battery positive electrode active material of the first aspect.

[0020] In a fifth aspect, the present application provides a sodium-ion battery, comprising the positive electrode prepared by the preparation method of the third aspect or the positive electrode of the fourth aspect.

[0021] In a sixth aspect, the present application provides an electric device, comprising the sodium-ion battery of the fifth aspect.

[0022] The first material in the sodium ion battery positive electrode active material provided by the application can play a role of pre-supplementing sodium in the preparation process, make up for the loss of active sodium in the first charge-discharge process of the sodium ion battery, and at the same time, the sodium ion battery positive electrode active material can reduce the residual alkali content in the preparation process of the positive electrode, avoid the influence of residual alkali on the performance of the positive electrode and the sodium ion battery, so as to obtain a positive electrode and a sodium ion battery with excellent performance. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. The specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0024] Figure 1 The preparation method flow chart of the positive electrode provided by an embodiment of the present application.

[0025] Figure 2 The surface of the positive electrode prepared for Example 10 is subjected to electron microscope scanning, Figure 2 The scale in (a) is 5 μm, Figure 2 The scale in (b) is 20 μm.

[0026] Figure 3 The surface of the positive electrode prepared for Comparative Example 2 is subjected to electron microscope scanning, Figure 3 The scale in (a) is 1 μm, Figure 3 The scale in (b) is 10 μm. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0028] In the related art, sodium ions released from the positive electrode during the first charging of a sodium-ion battery will react at the negative electrode to form an SEI film or other side reactions, causing loss of active sodium ions, resulting in low first coulombic efficiency and capacity loss of the sodium-ion battery. Therefore, additional active sodium needs to be pre-supplemented in the battery, i.e., pre-supplementing sodium. Meanwhile, layered oxides have the advantages of simple preparation method, high specific capacity, high compaction density, and high working voltage, and are often used as positive active materials for sodium-ion batteries. However, high-temperature sintering is required in the preparation of layered oxides, and part of the sodium raw material does not enter the phase structure but remains on the surface of the material and reacts with water, carbon dioxide and other substances in the air to form alkaline sodium hydroxide, sodium carbonate and the like, i.e., residual alkali. During the coating process of the positive electrode slurry, the residual alkali will damage the binder, causing the positive electrode slurry to gel, making it difficult to coat, and even affecting the performance of the sodium-ion battery.

[0029] Therefore, the present application provides a sodium-ion battery positive active material, which comprises a sodium-ion layered transition metal oxide and a first material, the first material comprising at least one of sodium carbonate and sodium bicarbonate. The sodium-ion battery positive active material provided by the present application can be used to prepare a positive electrode of a sodium-ion battery, and can simultaneously achieve the effects of pre-supplementing sodium and reducing residual alkali, thereby improving the performance of the positive electrode and the sodium-ion battery. In the sodium-ion battery positive active material provided by the present application, the sodium-ion layered transition metal oxide and the first material are dispersed together.

[0030] In an embodiment of the present application, the sodium-ion layered transition metal oxide is Na x Tm y O2, and Tm is a transition metal element. In an embodiment of the present application, 0 < x ≤ 1 and 0 < y ≤ 1. The layered oxide has high specific capacity, high compaction density, and high working voltage. Specifically, x can be but is not limited to 0.1, 0.2, 0.3, 0.5, 0.67, 0.7, 0.8, 0.9 or 1, and y can be but is not limited to 0.1, 0.2, 0.3, 0.5, 0.67, 0.7, 0.8, 0.9 or 1. In an embodiment, x ≤ 0.5. In another embodiment, 0.5 < x < 0.67. In yet another embodiment, 0.67 ≤ x ≤ 1, which is conducive to further improving the reversible capacity of the sodium-ion layered transition metal oxide. In an embodiment of the present application, the transition metal element comprises at least one of Cu, Fe, Mn, Ni, Co, Cr, Zn, Ti, Al, Nb, Zr, Ca, Li and V, which is conducive to improving the performance of the sodium-ion layered transition metal oxide. In an embodiment, the transition metal element comprises at least one of Cu, Fe, Mn and Ni. Specifically, the transition metal element can comprise at least three of Cu, Fe, Mn and Ni. It can be understood that Na x Tm yThe element types and proportions in O2 satisfy charge balance.

[0031] In an embodiment of the present application, the sodium-ion layered transition metal oxide includes at least one of P2 phase, O3 phase and P3 phase. The sodium-ion layered transition metal oxide of O3 phase has a high initial sodium content, can release more sodium ions, and has a high specific capacity; the sodium-ion layered transition metal oxide of P2 phase has a large sodium layer spacing, can improve the transmission rate of sodium ions and maintain the integrity of the layered structure, and has excellent rate performance and cycle performance. The sodium-ion layered transition metal oxide of P3 phase provides an open prism channel for sodium ion diffusion, and the diffusion barrier is relatively low, which is beneficial to the deintercalation of sodium ions.

[0032] In the present application, the first material includes at least one of sodium carbonate and sodium bicarbonate, and the first material can react with the acid agent, thereby facilitating the reduction of residual alkali content and the realization of pre-sodium supplement in the preparation of the positive electrode. In an embodiment of the present application, the first material further includes at least one of sodium hydroxide and sodium oxide. In an embodiment of the present application, the first material includes at least one of sodium carbonate and sodium bicarbonate, and the mass content of carbon element in the sodium-ion battery positive electrode active material can be 0.1%-3%. Specifically, the mass content of carbon element in the sodium-ion battery positive electrode active material can be, but is not limited to, 0.2%, 0.5%, 1%, 1.5% or 2%, etc.

[0033] In an embodiment of the present application, the molar ratio of sodium element in the sodium-ion layered transition metal oxide to sodium element in the first material is 3.3-20, which can not only ensure the content of sodium-ion layered transition metal oxide in the sodium-ion battery positive electrode active material, thereby improving the performance of the positive electrode and the sodium-ion battery, but also achieve the effect of reducing residual alkali and pre-supplementing sodium. Specifically, the molar ratio of sodium element in the sodium-ion layered transition metal oxide to sodium element in the first material can be, but is not limited to, greater than or equal to 3.5, 5, 7, 10, 12, 15, 17 or 20, etc.

[0034] In an embodiment of the present application, the mass content of the sodium ion layered transition metal oxide in the sodium ion battery positive electrode active material is 81.49%-97.67%, and the mass content of the first material is 2.33%-18.51%, which is beneficial to improve the performance of the positive electrode active material, further reduce the residual alkali content in the preparation of the positive electrode, and has active sodium ions, which can play a role in pre-supplementing sodium in the use of the battery, and is beneficial to further improve the performance of the battery. Specifically, the mass content of the sodium ion layered transition metal oxide in the sodium ion battery positive electrode active material can be, but is not limited to, 81.6%, 82%, 82.3%, 82.5%, 83%, 83.8%, 84.5%, 85%, 86%, 87.6%, 88%, 88.3%, 88.5%, 89%, 89.74%, 90.05%, 90.23%, 91.7%, 92%, 93.5%, 95%, 96.5%, or 97%, etc., and the mass content of the first material in the sodium ion battery positive electrode active material can be, but is not limited to, 2.5%, 2.82%, 2.95%, 3%, 3.5%, 5%, 6.5%, 8%, 8.3%, 9.77%, 9.95%, 10.26%, 11%, 11.5%, 11.7%, 12%, 12.4%, 13%, 14.5%, 15%, 16.9%, 17%, 18%, or 18.2%, etc. In an embodiment of the present application, when the first material is sodium carbonate, the mass content of the sodium ion layered transition metal oxide in the sodium ion battery positive electrode active material is 87.47%-97.67%, and the mass content of the first material is 2.33%-12.53%. In another embodiment of the present application, when the first material is sodium bicarbonate, the mass content of the sodium ion layered transition metal oxide in the sodium ion battery positive electrode active material is 81.49%-96.35%, and the mass content of the first material is 3.65%-18.51%.

[0035] In an embodiment of the present application, the particle size D50 of the sodium ion battery positive electrode active material is 1-20 μm. Specifically, the particle size D50 of the sodium ion battery positive electrode active material can be, but is not limited to, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 13 μm, 15 μm, or 20 μm, etc. In an embodiment of the present application, the primary particles of the sodium ion battery positive electrode active material are at least one of spheres, sphere-like bodies, flakes, and rods.

[0036] The application further provides a preparation method of the sodium-ion battery positive electrode active material, comprising the following steps: mixing a sodium-containing compound and a transition metal source, and then sintering to obtain the sodium-ion battery positive electrode active material, wherein the sodium-ion battery positive electrode active material comprises a sodium-ion layered transition metal oxide and a first material, and the first material comprises at least one of sodium carbonate and sodium bicarbonate.

[0037] In an embodiment of the application, the sodium-containing compound comprises at least one of sodium carbonate and sodium bicarbonate. The excess sodium-containing compound is partially retained, i.e. the first material in the sodium-ion positive electrode active material. In the application, the first material comprises at least one of sodium carbonate and sodium bicarbonate, and when air and water vapor exist in the preparation process, side reactions will occur to produce sodium hydroxide and sodium oxide, so that the first material further comprises at least one of sodium hydroxide and sodium oxide; if the influence of air and water vapor is avoided in the preparation process, the generation of sodium hydroxide and sodium oxide can be avoided.

[0038] In an embodiment of the application, the sodium-ion layered transition metal oxide is Na x Tm y O2, wherein 0 < x ≤ 1, 0 < y ≤ 1, and Tm is a transition metal element; when the sodium-containing compound and the transition metal source are mixed, the molar ratio of sodium in the sodium-containing compound to the transition metal element in the transition metal source is 1.05x:y to 1.3x:y. That is, when the molar ratio of sodium in the sodium-containing compound to the transition metal element in the transition metal source is x:y, it is in accordance with the stoichiometric ratio of chemical reaction, and the sodium-ion layered transition metal oxide Na x Tm yO2; however, the sodium-containing compound in the present application not only contains the part reacting with the transition metal source, but also contains the remaining part to ensure that the sodium ion battery positive active material contains the first material. Therefore, the sodium element in the sodium-containing compound is added by 5%-30% according to the stoichiometric ratio of the chemical reaction. Specifically, when the sodium-containing compound and the transition metal source are mixed, the molar ratio of sodium element in the sodium-containing compound to transition metal element in the transition metal source can be, but is not limited to, 1.08x:y, 1.1x:y, 1.12x:y, 1.15x:y, 1.2x:y, 1.25x:y or 1.3x:y, etc. In an embodiment of the present application, when the sodium-containing compound and the transition metal source are mixed, the molar ratio of sodium element in the sodium-containing compound to transition metal element in the transition metal source can be 1.05x:y to 1.11x:y. In another embodiment of the present application, when the sodium-containing compound and the transition metal source are mixed, the molar ratio of sodium element in the sodium-containing compound to transition metal element in the transition metal source can be 1.28x:y to 1.3x:y.

[0039] In an embodiment of the present application, the sodium ion battery positive active material can be prepared by co-precipitation method, solid phase method and sol-gel method. In an embodiment of the present application, the transition metal source includes at least one of transition metal oxide and transition metal hydroxide. In an embodiment of the present application, the sodium ion battery positive active material is obtained by sintering after mixing the sodium-containing compound and the transition metal oxide. In an embodiment of the present application, the sodium ion battery positive active material is obtained by sintering after mixing the sodium-containing compound and the transition metal hydroxide. In an embodiment, the preparation of the transition metal hydroxide includes co-precipitation reaction of a solution containing transition metal salt, a precipitant, a complexing agent, and drying to obtain the transition metal hydroxide. Specifically, the transition metal salt includes at least one of transition metal sulfate, transition metal nitrate and transition metal chloride; the precipitant includes at least one of sodium hydroxide and sodium carbonate; and the complexing agent includes at least one of ammonia and ammonium bicarbonate. It can be understood that the transition metal salt is a soluble salt, thereby ensuring the co-precipitation reaction. In an embodiment, the preparation of the transition metal hydroxide includes co-precipitation reaction of a solution containing transition metal salt, a precipitant, a complexing agent, a surfactant, and drying to obtain the transition metal hydroxide. The addition of the surfactant is beneficial to improve the reaction between the components. Specifically, the surfactant can include, but is not limited to, sodium dodecyl sulfate.

[0040] In an embodiment of the present application, the sintering temperature is 200-1000°C, and the time is 4-36h, which is conducive to the formation of sodium-ion layered transition metal oxides. Specifically, the sintering temperature can be, but is not limited to, 200°C, 400°C, 500°C, 700°C, 800°C, 900°C, 950°C or 1000°C, etc., and the sintering time can be, but is not limited to, 5h, 10h, 12h, 15h, 20h, 25h, 27h, 30h, 33h or 36h, etc. In an embodiment of the present application, the sintering temperature can be 800-1000°C, and the time can be 12-30h, which is conducive to the rapid formation of sodium-ion layered transition metal oxides and the improvement of performance.

[0041] The present application also provides a preparation method of a positive electrode. Please refer to Figure 1 The flow chart of the preparation method of the positive electrode provided in an embodiment of the present application comprises:

[0042] S101: mixing the sodium-ion battery positive electrode active material in any of the above embodiments or the sodium-ion battery positive electrode active material prepared by any of the above embodiments with a binder and an acid agent to obtain a positive electrode slurry;

[0043] S102: coating the positive electrode slurry on the surface of a positive electrode current collector, and drying to obtain a positive electrode.

[0044] In the present application, the first material sodium carbonate and / or sodium bicarbonate in the sodium ion battery positive electrode active material in the positive electrode slurry reacts with the acid agent to generate a sodium salt containing the acid radical ion in the acid agent, thereby reducing the content of sodium carbonate and / or sodium bicarbonate in the positive electrode and also preventing sodium carbonate and / or sodium bicarbonate from reacting with moisture, carbon dioxide and the like in the air to continue to generate residual alkali, thereby avoiding the damage of residual alkali to the binder, ensuring the coating performance of the positive electrode slurry, and being beneficial to the improvement of the electrochemical performance of the positive electrode. At the same time, the sodium salt after the reaction of the first material in the sodium ion battery positive electrode active material with the acid agent can be used as a pre-sodium supplement in the positive electrode for the battery, providing additional active sodium for the sodium ion battery and improving the electrochemical performance of the sodium ion battery. Therefore, when the sodium ion battery positive electrode active material provided in the present application is used in the positive electrode and the sodium ion battery, it can not only solve the problem of high residual alkali content in the positive electrode, but also solve the problem of active sodium loss after the first charge and discharge, maximize the use of sodium ion battery positive electrode active material, and reduce the preparation cost of the positive electrode. In the related art, sodium carbonate and / or sodium bicarbonate is added as little as possible during the preparation of the sodium ion battery positive electrode active material to avoid the generation of residual alkali in the positive electrode, while the present application adds an excess of sodium-containing compounds, so that sodium carbonate and / or sodium bicarbonate exists in the sodium ion battery positive electrode active material, thereby reacting with the acid agent to generate a sodium salt during the preparation of the positive electrode. The sodium salt will not react with moisture, carbon dioxide and the like in the air to generate residual alkali. The sodium salt is in full contact with the sodium ion layered transition metal oxide and can provide additional active sodium for the sodium ion battery as a sodium supplement material, achieving the effect of pre-supplementing sodium. Therefore, the preparation method provided in the present application can reduce the residual alkali content in the positive electrode, reduce the requirements for product storage and processing environment, and be more conducive to the preparation of the positive electrode, while making up for the consumption of active sodium by the negative electrode and the positive electrode of the sodium ion battery during the first charge and discharge, which is beneficial to improving the first coulomb efficiency and capacity of the sodium ion battery.

[0045] In an embodiment of the present application, the ratio of the mass of the acid agent in the positive electrode slurry to the mass of the solids in the positive electrode slurry is 0.01%-10%, which is conducive to ensuring the sufficient reaction of the acid agent with the first material in the sodium-ion battery positive electrode active material, reducing the content of the first material in the positive electrode as much as possible, avoiding the gelation of the positive electrode slurry, and avoiding the decomposition of sodium salt caused by excessive acidity, thereby further improving the performance of the positive electrode. Specifically, the ratio of the mass of the acid agent in the positive electrode slurry to the mass of the solids in the positive electrode slurry can be, but is not limited to, 0.01%, 0.05%, 0.1%, 0.2%, 0.5%, 1%, 3%, 5%, 6%, 8%, 9%, or 10%, etc. In an embodiment of the present application, the ratio of the mass of the acid agent in the positive electrode slurry to the mass of the solids in the positive electrode slurry can be 0.01%-3%. In another embodiment of the present application, the ratio of the mass of the acid agent in the positive electrode slurry to the mass of the solids in the positive electrode slurry can be 3%-6%. In another embodiment of the present application, the ratio of the mass of the acid agent in the positive electrode slurry to the mass of the solids in the positive electrode slurry can be 6%-10%. It can be understood that, in addition to the first material, the acid agent does not react with other components in the positive electrode slurry. In an embodiment of the present application, the positive electrode slurry further includes the first material. That is, the acid agent reacts with the first material, and there is still some first material remaining, but the content of the first material is small and does not affect the coating of the positive electrode slurry. Specifically, the molar ratio of sodium in the sodium salt in the positive electrode slurry to the sodium in the first material is greater than 9, greater than 15, greater than 20, or greater than 25, etc. In an embodiment of the present application, the acid agent includes at least one of oxalic acid, acetic acid, boric acid, salicylic acid, citric acid, ascorbic acid, formic acid, propionic acid, and malonic acid. Correspondingly, the sodium salt includes at least one of sodium oxalate, sodium acetate, sodium borate, sodium salicylate, sodium citrate, sodium ascorbate, sodium formate, sodium propionate, and sodium malonate.

[0046] In an embodiment of the present application, the positive electrode slurry includes 70-98 parts by weight of the sodium-ion battery positive electrode active material and 1-15 parts by weight of the binder. Specifically, the positive electrode slurry can include, but is not limited to, 70, 72, 75, 77, 80, 83, 85, 88, 90, 93, 95, or 98 parts by weight of the sodium-ion battery positive electrode active material, and can include, but is not limited to, 1, 3, 5, 6, 9, 10, 12, 13, or 15 parts by weight of the binder. Specifically, the binder can include, but is not limited to, at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyaniline, polypyrrole, styrene-butadiene copolymer, acrylic resin, and acrylic copolymer. In another embodiment of the present application, the positive electrode slurry includes 70-98 parts by weight of the sodium-ion battery positive electrode active material, 1-15 parts by weight of the binder, and 1-15 parts by weight of the conductive agent. Specifically, the positive electrode slurry can include, but is not limited to, 1, 3, 5, 6, 9, 10, 12, 13, or 15 parts by weight of the conductive agent. Specifically, the conductive agent can include, but is not limited to, at least one of carbon black, acetylene black, carbon nanowire, nanometer carbon tube, and graphite.

[0047] In an embodiment of the present application, the positive electrode slurry further includes a solvent. The solvent is used to dissolve or disperse the sodium-ion battery positive electrode active material, the binder, and the acid agent, etc. Specifically, the solvent can include, but is not limited to, at least one of N-methylpyrrolidone and acetone. In an embodiment of the present application, the sodium-ion battery positive electrode active material, the binder, the acid agent, and the solvent can be mixed in a blender mixing tank or a planetary mixer.

[0048] In the present application, the positive electrode slurry is coated on at least one surface of the positive electrode current collector. The material of the positive electrode current collector can include, but is not limited to, aluminum, specifically, such as ordinary aluminum foil, anti-ductile aluminum foil, carbon-coated aluminum foil, etc.

[0049] In an embodiment of the present application, the coating temperature is 15-30°C, and the dew point temperature is -50 to -20°C. Specifically, the coating temperature can include, but is not limited to, 15°C, 20°C, 25°C, or 30°C, and the dew point temperature can include, but is not limited to, -50°C, -40°C, -35°C, -30°C, -25°C, or -20°C. In an embodiment of the present application, the drying temperature is 90-120°C. Specifically, the drying temperature can include, but is not limited to, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, or 120°C. In an embodiment of the present application, the drying can also be followed by cold pressing and cutting, and the specific process can be selected as needed.

[0050] The application further provides a positive electrode, comprising a positive electrode current collector and a positive electrode active material layer arranged on the surface of the positive electrode current collector, wherein the positive electrode active material layer is made of the sodium ion battery positive electrode active material according to any one of the above embodiments.

[0051] In an embodiment of the application, the positive electrode active material layer comprises a sodium ion layered transition metal oxide and a sodium salt. In the sodium ion battery positive electrode active material, the first material reacts with an acid agent to form the sodium salt.

[0052] In an embodiment of the application, the mass content of carbon in the positive electrode is 5%-15%. Specifically, the mass content of carbon in the positive electrode can be, but is not limited to, 5%, 8%, 10%, 11%, 13% or 15%, etc. In the application, the source of carbon in the positive electrode includes the sodium salt and the conductive agent.

[0053] In an embodiment of the application, the sodium salt in the positive electrode is a cluster structure, and the cluster structure is formed by a plurality of needle-like agglomerates. In an embodiment of the application, the length of the needle-like structure can be 1-50 μm. In an embodiment of the application, the needle-like structure is connected by one or more rod-like structures, and the length of the rod-like structure can be 1-10 μm. In an embodiment of the application, the sodium ion layered transition metal oxide in the positive electrode is a spheroid structure, and the spheroid is formed by a plurality of stacked sheet-like structures.

[0054] The application further provides a sodium ion battery comprising the positive electrode prepared according to any one of the above embodiments or the positive electrode according to any one of the above embodiments. The sodium ion battery has high initial coulombic efficiency, good capacity and excellent cycle performance, which is beneficial to the application of the sodium ion battery. It can be understood that the sodium ion battery in the application comprises at least one of a button cell, a soft package battery, a square cell and a cylindrical cell.

[0055] In an embodiment of the application, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector. The material of the negative electrode current collector can be, but is not limited to, copper. In an embodiment of the application, the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material comprises at least one of a carbon material, a metal element, an alloy and a metal compound. In an embodiment, the metal compound comprises at least one of a metal oxide, a metal sulfide and a metal phosphide.

[0056] In an embodiment of the application, the sodium ion battery further comprises a separator arranged between the positive electrode and the negative electrode. Specifically, the material of the separator can comprise at least one of polyethylene and polypropylene.

[0057] In an embodiment of the present application, the battery further comprises an electrolyte. At least part of the positive electrode and at least part of the negative electrode are soaked in the electrolyte. In an embodiment of the present application, the electrolyte comprises an electrolyte solvent and an electrolyte sodium salt. In an embodiment, the electrolyte sodium salt comprises at least one of sodium hexafluorophosphate, sodium bis(trifluoromethylsulfonyl)imide, sodium perchlorate, sodium triflate, sodium fluoroborate, sodium nitrate, and sodium chloride. In an embodiment, the concentration of the electrolyte sodium salt in the electrolyte is 0.1 mol / L-2.5 mol / L. Specifically, the concentration of the electrolyte sodium salt in the electrolyte can be, but is not limited to, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 1 mol / L, 1.4 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.3 mol / L, or 2.5 mol / L, etc. In an embodiment, the electrolyte solvent comprises at least one of carbonates, ethers, amides, sulfones, nitriles, and furans. Specifically, the carbonates comprise at least one of cyclic carbonates and chain carbonates, the cyclic carbonates comprise at least one of ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, 1,4-butyrolactone, and 1,3-propane sultone, the chain carbonates comprise at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, ethyl propyl carbonate, methyl propyl carbonate, ethyl acetate, ethyl propionate, ethyl butyrate, and propyl propionate; the ethers comprise at least one of diethyl ether, methyl tert-butyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and polyether; the amides comprise N,N-dimethylformamide; the sulfones comprise dimethyl sulfoxide; the nitriles comprise acetonitrile; and the furans comprise at least one of tetrahydrofuran and 2-methyltetrahydrofuran. In another embodiment of the present application, the electrolyte comprises an electrolyte solvent, an electrolyte sodium salt, and an electrolyte additive. In an embodiment, the mass content of the electrolyte additive in the electrolyte is 0.1%-50%. Specifically, the mass content of the electrolyte additive in the electrolyte can be, but is not limited to, 0.1%, 0.5%, 1%, 3%, 10%, 15%, 20%, 25%, 35%, 40%, or 50%, etc. Specifically, the electrolyte additive comprises at least one of fluoroethylene carbonate, chloroethylene carbonate, vinylene carbonate, dicarbonate, sulfite, and anisole.

[0058] In an embodiment of the present application, the positive electrode, the separator and the negative electrode can be stacked and then injected with electrolyte, and the sodium-ion battery can be obtained by packaging after formation. In the formation, the sodium salt in the positive electrode is decomposed to generate sodium ions and gas, and the gas is discharged before packaging. In an embodiment of the present application, the formation conditions are as follows: standing for 10 min in an environment of 45±2℃→ charging to 4.2V at a current of 0.1C→ standing for 10 min→ discharging to 2.0V at a current of 0.1C→ standing for 10 min→ charging for 2.5h at a current of 0.1C, and the first charge and discharge capacities are recorded as C1 and C2, respectively, and the first coulombic efficiency = C2 / C1 x 100%. The first coulombic efficiency of the sodium-ion battery provided in the present application is greater than 85%.

[0059] The present application provides an electric device comprising the sodium-ion battery in any of the above embodiments. The electric device provided in the present application has excellent performance and strong product competitiveness. The electric device of the present application can refer to a vehicle, an electronic device, an energy storage system, etc., and the above battery can be arranged in the electric device in the form of a single battery, a battery module, a battery pack, etc.

[0060] The effects of the technical solutions provided in the present application are further illustrated by specific examples below.

[0061] Example 1

[0062] A preparation method of a sodium-ion battery positive electrode active material, comprising:

[0063] 2M NiSO4·6H2O, FeSO4·7H2O and MnSO4·H2O aqueous solutions are added to a 2M NaOH solution according to the stoichiometric ratio, and an appropriate amount of ammonia water and sodium dodecyl sulfate are added as complexing agents and surfactants, and the mixture is heated to 50℃ and stirred for 2h to perform a coprecipitation reaction to obtain a precipitate. The precipitate is filtered, washed and dried to obtain (Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 )(OH)2. (Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 )(OH)2 is mixed with Na2CO3 at a molar ratio of 1:0.56, and then calcined at 850℃ for 15h to obtain a sodium-ion battery positive electrode active material, which comprises sodium-ion layered transition metal oxide NaNi 1 / 3 Fe 1 / 3Mn 1 / 3 O2 and the first material Na2CO3, and the sodium-ion battery positive electrode active material comprises sodium-ion layered transition metal oxide NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3The molar ratio of sodium element in O2 to sodium element in Na2CO3 is 10, and the content of NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 The mass content of O2 is 95.44%, and the mass content of the first material is 4.56%.

[0064] Example 2

[0065] A preparation method of a sodium ion battery positive electrode active material, comprising:

[0066] A 2M aqueous solution of NiSO4·6H2O, FeSO4·7H2O and MnSO4·H2O is added to a 2M NaOH solution according to the stoichiometric ratio, and an appropriate amount of ammonia water and sodium dodecyl sulfate are added as complexing agent and surfactant, heated to 50°C and fully stirred for 2h to carry out coprecipitation reaction to obtain precipitate. After filtering, washing and drying the precipitate, (Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 )(OH)2 is obtained. (Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 )(OH)2 is mixed with Na2CO3 according to a molar ratio of 1:0.58, and then calcined at 850°C for 15h to obtain a sodium ion battery positive electrode active material. The sodium ion battery positive electrode active material comprises sodium ion layered transition metal oxide NaNi 1 / 3 Fe 1 / 3Mn 1 / 3 O2 and the first material Na2CO3, and the content of NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 The molar ratio of sodium element in O2 to sodium element in Na2CO3 is 6.67, and the content of NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 The mass content of O2 is 93.32%, and the mass content of the first material is 6.68%.

[0067] Example 3

[0068] A preparation method of a sodium ion battery positive electrode active material, comprising:

[0069] A 2M aqueous solution of NiSO4·6H2O, FeSO4·7H2O and MnSO4·H2O is added to a 2M NaOH solution according to the stoichiometric ratio, and an appropriate amount of ammonia water and sodium dodecyl sulfate are added as complexing agent and surfactant, heated to 50°C and fully stirred for 2h to carry out coprecipitation reaction to obtain precipitate. After filtering, washing and drying the precipitate, (Ni1 / 3 Fe 1 / 3 Mn 1 / 3 )(OH)2. 1 / 3 Fe 1 / 3 Mn 1 / 3 )(OH)2 and NaHCO3 are mixed in a molar ratio of 1:1.33 and calcined at 850°C for 15h to obtain a positive electrode active material for a sodium ion battery. The positive electrode active material for a sodium ion battery includes a sodium ion layered transition metal oxide NaNi 1 / 3 Fe 1 / 3Mn 1 / 3 O2 and the first material NaHCO3, NaNi in the positive electrode active material of sodium ion battery 1 / 3 Fe 1 / 3 Mn 1 / 3 The molar ratio of sodium in O2 to sodium in NaHCO3 is 3.125. 1 / 3 Fe 1 / 3 Mn 1 / 3 The mass content of O2 is 80.50%, and the mass content of the first material is 19.50%.

[0070] Example 4

[0071] A method for preparing a positive electrode active material for a sodium ion battery, comprising:

[0072] 2M NiSO4·6H2O, FeSO4·7H2O and MnSO4·H2O aqueous solutions were added to 2M NaOH solution in a stoichiometric ratio, and appropriate amounts of ammonia and sodium dodecyl sulfate were added as complexing agents and surfactants. The mixture was heated to 50°C and stirred for 2 hours to perform a coprecipitation reaction to obtain a precipitate. The precipitate was filtered, washed and dried to obtain (Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 )(OH)2. 1 / 3 Fe 1 / 3 Mn 1 / 3 )(OH)2 and Na2CO3 are mixed in a molar ratio of 1:0.52 and calcined at 850°C for 15h to obtain a sodium ion battery positive electrode active material. The sodium ion battery positive electrode active material includes a sodium ion layered transition metal oxide NaNi 1 / 3 Fe 1 / 3Mn 1 / 3 O2 and the first material Na2CO3, NaNi in the positive electrode active material of sodium ion battery 1 / 3 Fe 1 / 3 Mn 1 / 3 The molar ratio of sodium in O2 to sodium in Na2CO3 is 33.3. 1 / 3Fe 1 / 3 Mn 1 / 3 The mass content of O2 is 98.59%, and the mass content of the first material is 1.41%.

[0073] Example 5

[0074] A preparation method of a sodium-ion battery positive electrode active material, comprising:

[0075] 2M NiSO4·6H2O, FeSO4·7H2O and MnSO4·H2O aqueous solutions are added into a 2M NaOH solution according to the stoichiometric ratio, and an appropriate amount of ammonia water and sodium dodecyl sulfate are added as a complexing agent and a surfactant, and the mixture is heated to 50°C and fully stirred for 2h to perform a co-precipitation reaction to obtain a precipitate. After the precipitate is filtered, washed and dried, (Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 )(OH)2 is obtained. (Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 )(OH)2 is mixed with NaHCO3 according to a molar ratio of 1:1.12, and then calcined at 850°C for 15h to obtain a sodium-ion battery positive electrode active material. The sodium-ion battery positive electrode active material comprises a sodium-ion layered transition metal oxide NaNi 1 / 3 Fe 1 / 3Mn 1 / 3 O2 and a first material NaHCO3. The molar ratio of sodium elements in NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 to sodium elements in NaHCO3 in the sodium-ion battery positive electrode active material is 10. The mass content of NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 is 92.96%, and the mass content of the first material is 7.04%.

[0076] Example 6

[0077] A preparation method of a sodium-ion battery positive electrode active material, comprising:

[0078] 2M NiSO4·6H2O, FeSO4·7H2O and MnSO4·H2O aqueous solutions are added into a 2M NaOH solution according to the stoichiometric ratio, and an appropriate amount of ammonia water and sodium dodecyl sulfate are added as a complexing agent and a surfactant, and the mixture is heated to 50°C and fully stirred for 2h to perform a co-precipitation reaction to obtain a precipitate. After the precipitate is filtered, washed and dried, (Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 )(OH)2 is obtained. (Ni1 / 3 Fe 1 / 3 Mn 1 / 3 )(OH)2and Na2CO3 in a molar ratio of 1:0.53, and calcining the mixture at 850°C for 15h, to obtain a sodium-ion battery cathode active material, the sodium-ion battery cathode active material comprising a sodium-ion layered transition metal oxide NaNi 1 / 3 Fe 1 / 3Mn 1 / 3 O2and the first material Na2CO3, the sodium-ion battery cathode active material comprising a sodium-ion layered transition metal oxide NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, the molar ratio of sodium elements in Na2CO3 to sodium elements in NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2is 91.28%, and the mass content of the first material is 8.72%.

[0079] Example 7

[0080] A method for preparing a sodium-ion battery cathode active material, comprising:

[0081] A 2M CuSO4·6H2O, FeSO4·7H2O and MnSO4·H2O aqueous solution is added to a 2M NaOH solution in a stoichiometric ratio, an appropriate amount of ammonia water and sodium dodecyl sulfate are added as a complexing agent and a surfactant, and a coprecipitation reaction is carried out by heating to 50°C and stirring for 2h to obtain a precipitate. The precipitate is filtered, washed and dried to obtain (Cu 0.2 Fe 0.3 Mn 0.5 )(OH)2. (Cu 0.2 Fe 0.3 Mn 0.5 )(OH)2and Na2CO3 in a molar ratio of 1:0.56, and calcining the mixture at 850°C for 15h, to obtain a sodium-ion battery cathode active material, the sodium-ion battery cathode active material comprising a sodium-ion layered transition metal oxide NaCu 0.2 Fe 0.3 Mn 0.5 O2and the first material Na2CO3, the sodium-ion battery cathode active material comprising a sodium-ion layered transition metal oxide NaCu 0.2 Fe 0.3 Mn 0.5 O2, the molar ratio of sodium elements in Na2CO3 to sodium elements in NaCu 0.2 Fe 0.3 Mn 0.5The mass content of O2 is 94.63%, and the mass content of the first material is 4.52%.

[0082] Example 8

[0083] A preparation method of a positive electrode, comprising:

[0084] The sodium ion battery positive electrode active material prepared in Example 1, polyvinylidene fluoride, and conductive carbon black super P are added into N-methyl pyrrolidone in a weight ratio of 8:1:1 to perform slurry mixing, and oxalic acid is added into the positive electrode slurry, and the mass ratio of the oxalic acid in the positive electrode slurry to the solid mass in the positive electrode slurry is 2%. After the positive electrode slurry is sieved through a 150-mesh screen, the positive electrode slurry is coated on an aluminum foil, and then baking and drying are performed at 110°C, and after cooling and rolling, the positive electrode is obtained.

[0085] Example 9

[0086] A preparation method of a positive electrode, comprising:

[0087] The sodium ion battery positive electrode active material prepared in Example 1, polyvinylidene fluoride, and conductive carbon black super P are added into N-methyl pyrrolidone in a weight ratio of 8:1:1 to perform slurry mixing, and oxalic acid is added into the positive electrode slurry, and the mass ratio of the oxalic acid in the positive electrode slurry to the solid mass in the positive electrode slurry is 1%. After the positive electrode slurry is sieved through a 150-mesh screen, the positive electrode slurry is coated on an aluminum foil, and then baking and drying are performed at 110°C, and after cooling and rolling, the positive electrode is obtained.

[0088] Examples 10-15

[0089] A preparation method of a positive electrode, comprising:

[0090] The sodium ion battery positive electrode active materials prepared in Examples 2-7, polyvinylidene fluoride, and conductive carbon black super P are added into N-methyl pyrrolidone in a weight ratio of 8:1:1 to perform slurry mixing, and oxalic acid is added into the positive electrode slurry, and the mass ratio of the oxalic acid in the positive electrode slurry to the solid mass in the positive electrode slurry is 2%. After the positive electrode slurry is sieved through a 150-mesh screen, the positive electrode slurry is coated on an aluminum foil, and then baking and drying are performed at 110°C, and after cooling and rolling, the positive electrode is obtained.

[0091] Comparative Example 1

[0092] 2M aqueous solutions of NiSO4·6H2O, FeSO4·7H2O, and MnSO4·H2O are added into a 2M NaOH solution in a stoichiometric ratio, and an appropriate amount of ammonia water and sodium dodecyl sulfate are added as a complexing agent and a surfactant, and the mixture is heated to 50°C and stirred for 2h to perform a coprecipitation reaction to obtain a precipitate. After the precipitate is filtered, washed, and dried, (Ni 1 / 3 Fe 1 / 3 Mn1 / 3 )(OH)2. The (Cu 1 / 3 Fe 1 / 3 Mn 1 / 3 )(OH)2was mixed with Na2CO3in a molar ratio of 1:0.51 and calcined at 850°C for 15h to obtain the sodium-ion battery cathode active material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, without sodium carbonate.

[0093] Comparative Example 2

[0094] A 2M aqueous solution of CuSO4·6H2O, FeSO4·7H2O and MnSO4·H2O was added to a 2M NaOH solution in stoichiometric ratio, and an appropriate amount of ammonia water and sodium dodecyl sulfate were added as complexing agent and surfactant. The mixture was heated to 50°C and stirred for 2h to carry out the coprecipitation reaction to obtain a precipitate. The precipitate was filtered, washed and dried to obtain (Cu 0.2 Fe 0.3 Mn 0.5 )(OH)2. The (Cu 0.2 Fe 0.3 Mn 0.5 )(OH)2was mixed with Na2CO3in a molar ratio of 1:0.51 and calcined at 850°C for 15h to obtain the sodium-ion battery cathode active material, which is a sodium-ion layered transition metal oxide NaCu 0.2 Fe 0.3 Mn 0.5 O2, without sodium carbonate.

[0095] Comparative Example 3

[0096] The NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2obtained in Comparative Example 1 was mixed with polyvinylidene fluoride and conductive carbon black super P in a weight ratio of 8:1:1 in N-methylpyrrolidone to obtain a cathode slurry. The cathode slurry was sieved through a 150-mesh screen and coated on an aluminum foil, followed by baking and drying at 110°C. After cooling and rolling, the cathode was obtained.

[0097] Comparative Example 4

[0098] The NaCu 0.2 Fe 0.3 Mn 0.5O2 and polyvinylidene fluoride, conductive carbon black super P were added into N-methyl pyrrolidone in a weight ratio of 8:1:1 to perform slurry mixing to obtain a positive electrode slurry. The positive electrode slurry was sieved through a 150 mesh screen and then coated on an aluminum foil, followed by baking and drying at 110°C, cooling and rolling to obtain a positive electrode.

[0099] Performance detection

[0100] The sodium ion battery positive electrode active material prepared in Example 1-7 or Comparative Example 1-2 was dispersed in deionized water, and after being stirred at a speed of 800 rpm for 5 min, the pH value of the aqueous solution was measured, and the CO3 2- content in the sodium ion battery positive electrode active material was measured by titration. The sodium ion battery positive electrode active material prepared in Example 1-7 or Comparative Example 1-2 was dispersed in an organic solvent (ethanol or ethylene glycol), and after being stirred at a speed of 800 rpm for 70 min, the OH - content in the sodium ion battery positive electrode active material was measured by diluting 10 times with deionized water. The carbon element content in the sodium ion battery positive electrode active material was measured by a carbon-sulfur analyzer. The above detection results are shown in Table 1, wherein the detection results of the CO3 2- content in Example 3 and 5 are HCO3 - and CO3 2- content. It can be seen that the content of carbonate in Comparative Example 1 is small, and the residual sodium carbonate is less, which cannot provide the effect of pre-supplementing sodium, while the CO3 2- content and the carbon element content in the sodium ion battery positive electrode active material prepared in Example 1-7 of the application are significantly increased, indicating that the sodium ion battery positive electrode active material contains sodium carbonate and sodium bicarbonate, so that it can react with the acid agent in the preparation of the positive electrode to reduce the residual alkali content in the positive electrode, and the generated sodium salt can provide sodium ions to achieve the effect of pre-supplementing sodium.

[0101] Table 1 Performance detection results of sodium ion battery positive electrode active material

[0102]

[0103]

[0104] The surface of the positive electrode prepared in Example 10 and Comparative Example 3 was scanned by electron microscopy, and the results are shown in Figure 2 and Figure 3 wherein, Figure 2 the surface of the positive electrode prepared in Example 10 was scanned by electron microscopy, Figure 2 the scale in (a) of the above is 5 μm, Figure 2 the scale in (b) of the above is 20 μm, Figure 2 (a) of the above is Figure 2Enlarged view of the red boxed area in the center of (b); Figure 3 The surface of the positive electrode prepared for Comparative Example 2 was scanned by electron microscope, Figure 3 The scale in (a) is 1 μm, Figure 3 The scale in (b) is 10 μm, Figure 3 (a) is Figure 3 Enlarged view of a certain area in (b). It can be seen that no acid agent was added in Comparative Example 3, Figure 3 The morphology shown does not exist in the morphology, Figure 3 In (b), only the structure of spheroid composed of flaky stacking exists; in the positive electrode prepared in the present application, acid agent is added, not only the structure of spheroid composed of flaky stacking exists, Figure 2 In the morphology shown, there also exists obvious structure of cluster composed of needle-like structures, which is the structure of sodium salt in the positive electrode.

[0105] The positive electrodes prepared in Examples 8-15 and Comparative Examples 3-4 were assembled into soft pack batteries together with negative electrodes, separators and electrolyte, the negative electrode active material was hard carbon, and the electrolyte was 1M sodium hexafluorophosphate, propylene carbonate, methyl ethyl carbonate and fluoroethylene carbonate. The assembled soft pack batteries were aged in 45°C environment for 48h, released gas after formation and were subjected to secondary packaging, wherein the formation included clamping the battery with a clamp and installing it on a formation cabinet, placing it in an environment of 45±2°C, setting the program: standing for 10 min→ constant current charging to 4.2V at a current of 0.1C→ standing for 10 min→ constant current discharging to 2.0V at a current of 0.1C→ standing for 10 min→ constant current charging for 2.5h at a current of 0.1C, recording the first charge and discharge capacity as C1 and C2 respectively, the first coulombic efficiency = C2 / C1 x 100%, the specific charge capacity = C1 / total mass of positive electrode active material in the whole battery, and the specific discharge capacity = C2 / total mass of positive electrode active material in the whole battery. The charge and discharge cycle test of the battery included: 1) 25°C battery cycle performance test: the whole battery was clamped with a clamp and installed on a test instrument, placed in a 25±2°C environment, standing for 10 min→ 1.0C constant current discharging to 1.5V→ standing for 10 min→ 1.0C constant current charging to 4.0V→ standing for 10 min→ 1.0C constant current discharging to 2.0V, the above steps were repeated 100 times as a repeating unit, and the battery capacity was tested to obtain the battery capacity after 100 cycles at 25°C, the capacity retention rate after 100 cycles at 25°C = battery capacity after 100 cycles at 25°C / first discharge capacity at 25°C x 100%; 2) 45°C battery cycle performance test: the difference from the 25°C battery cycle performance test method was that the battery was placed in a 45±2°C environment to obtain the battery capacity after 100 cycles at 45°C and the first discharge capacity at 45°C, and then the capacity retention rate after 100 cycles at 45°C was calculated, and the above test results are shown in Table 2.

[0106] Table 2 sodium ion battery performance test results

[0107]

[0108] It can be seen that compared with Comparative Example 3, the charge-discharge specific capacity of the sodium ion battery prepared by Examples 8-14 of the present application is increased, the first coulombic efficiency is improved, the first energy efficiency is improved, and the capacity retention rate of 100 cycles of Examples 8-10 and 13-14 is significantly increased. Compared with Comparative Example 4, the overall performance of the sodium ion battery prepared by Example 15 of the present application is improved, indicating that the first material in the positive electrode active material provided by the present application can react with the acid agent, which not only reduces the residual alkali content in the positive electrode, but also plays a pre-sodium supplement effect, thereby improving the performance of the sodium ion battery, which is conducive to the use of the sodium ion battery.

[0109] The above-described examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the patent of the present application. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A sodium-ion battery cathode active material, characterized in that, The sodium-ion battery positive electrode active material comprises a sodium-ion layered transition metal oxide and a first material, the first material comprises sodium carbonate, the mass content of the sodium-ion layered transition metal oxide in the sodium-ion battery positive electrode active material is 81.49%-97.67%, and the mass content of the first material is 2.33%-18.51%.

2. The sodium-ion battery cathode active material of claim 1, wherein, The molar ratio of sodium in the sodium-ion layered transition metal oxide to sodium in the first material is 3.3-20.

3. The sodium-ion battery cathode active material of claim 1, wherein The first material further comprises at least one of sodium bicarbonate, sodium hydroxide and sodium oxide.

4. The sodium-ion battery cathode active material of claim 1, wherein, The sodium-ion layered transition metal oxide is Na x Tm y O2, wherein 0 < x < 1, 0 < y < 1, Tm is a transition metal element, and the transition metal element includes at least one of Cu, Fe, Mn, Ni, Co, Cr, Zn, Ti, Al, Nb, Zr, Ca, Li, and V.

5. A method for preparing a sodium-ion battery cathode active material, characterized in that, The sodium-ion battery positive electrode active material comprises a sodium-ion layered transition metal oxide and a first material, the first material comprises sodium carbonate, the mass content of the sodium-ion layered transition metal oxide in the sodium-ion battery positive electrode active material is 81.49%-97.67%, and the mass content of the first material is 2.33%-18.51%. When the sodium-containing compound and the transition metal source are mixed, the molar ratio of sodium in the sodium-containing compound to transition metal in the transition metal source is 1.05x:y to 1.3x:y.

6. The production method according to claim 5, wherein The sodium-ion layered transition metal oxide is Na x Tm y O2, wherein 0 < x < 1, 0 < y < 1, and Tm is a transition metal element. The sintering temperature is 200-1000°C, and the time is 4-36h.

7. The production method according to claim 5, wherein The transition metal source comprises at least one of a transition metal oxide and a transition metal hydroxide.

8. The production method according to claim 5, wherein The sodium-ion battery positive electrode active material of any one of claims 1-4 or the sodium-ion battery positive electrode active material prepared by the preparation method of any one of claims 5-8 is mixed with a binder and an acid agent to obtain a positive electrode slurry, and the mass ratio of the acid agent to the solid mass in the positive electrode slurry is 0.01%-10%.

9. A method for producing a positive electrode, characterized by comprising the steps of, The positive electrode slurry is coated on the surface of a positive electrode current collector, and the positive electrode is obtained after drying. The acid agent comprises at least one of oxalic acid, acetic acid, boric acid, salicylic acid, citric acid, ascorbic acid, formic acid, propionic acid and malonic acid. The positive electrode comprises a positive electrode current collector and a positive electrode active material layer arranged on the surface of the positive electrode current collector, and the positive electrode active material layer is made of the sodium-ion battery positive electrode active material of any one of claims 1-4.

10. The production method according to claim 9, wherein The positive electrode prepared by the preparation method of any one of claims 9-10 or the positive electrode of claim 11.

11. A positive electrode, characterized by comprising: The sodium-ion battery of claim 12.

12. A sodium-ion battery, characterized in that, ​ 13. An electrical device, characterized by ​

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