Sodium ion battery positive electrode material, preparation method therefor, positive electrode and sodium ion battery

Abstract

A sodium ion battery positive electrode material, a preparation method therefor, a positive electrode and a sodium ion battery. The sodium ion battery positive electrode material comprises a positive electrode substrate and a wrapping layer, the wrapping layer being a tungsten-containing compound coating the surface of the positive electrode substrate, and the positive electrode substrate being doped with an M element. The preparation method comprises the following steps: mixing NixFeyMnzMn(OH)2 and a sodium-containing compound, and sintering same to obtain a NamNixFeyMnzMnO2 material; and, mixing the tungsten-containing compound and the NamNixFeyMnzMnO2 material, and calcining same to obtain a positive electrode material co-modified by tungsten-containing compound coating and M element doping. The coating of the tungsten-containing compound and the doped effective element can reduce a residual alkali amount on the surface of the positive electrode material, thus fully improving the air stability of O3 type sodium ion battery positive electrode materials, effectively reducing gas production, reducing side reactions with electrolytes, and improving the cycle performance of the materials.

Description

Sodium ion battery positive electrode material and preparation method, positive electrode and sodium ion battery

[0001] This application claims priority to Chinese patent application No. 202310756708.9 filed on June 25, 2023, entitled “A sodium ion battery positive electrode material and preparation method, positive electrode and sodium ion battery”. The entire contents of the above Chinese patent application are incorporated into this application by reference. Technical Field

[0002] The present invention belongs to the technical field of battery materials, and in particular relates to a sodium ion battery positive electrode material and a preparation method, a positive electrode and a sodium ion battery. Background Art

[0003] Against the backdrop of relatively low raw material costs for lithium-ion batteries, sodium-ion batteries, which share a similar electrochemical working principle as lithium-ion batteries, have attracted widespread attention due to their low raw material costs and widespread availability. Currently, layered oxides in sodium-ion battery cathode materials have the same synthesis process as the widely used layered oxide cathodes in lithium-ion batteries, such as lithium cobalt oxide and ternary materials, making them promising cathode materials for the fastest large-scale industrialization. However, the surface of the O3 layered oxide cathode material for sodium-ion batteries has a high level of residual alkali, which can lead to gas production during the cycle and react with the electrolyte to deteriorate the cycle. Furthermore, a high level of residual alkali can also cause process problems such as gelation of the slurry during the slurrying process. Therefore, it is necessary to reduce the residual alkali and improve the interfacial stability of the cathode material.

[0004] Summary of the Invention

[0005] In response to the above technical problems, the present invention provides a sodium ion battery positive electrode material and a preparation method thereof.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention includes:

[0007] A sodium ion battery positive electrode material comprises a positive electrode substrate and a coating layer, wherein the coating layer is a tungsten-containing compound coated on the surface of the positive electrode substrate, and the positive electrode substrate is doped with an M element, wherein the M element is one or more of Al, Mg, Ti, Zr, Y, La, Cu, Zn, Ca, Li or B.

[0008] The present invention reduces the amount of residual alkali on the surface of the positive electrode material through the coating layer and the doped effective elements, fully improves the air stability of the positive electrode material of the O3 type sodium ion battery, effectively reduces gas production, reduces side reactions with the electrolyte, and improves the cycle performance of the material. Specifically, the coated tungsten-containing compound and the doped effective element can not only reduce the irreversible phase change of the material during the cycle and improve the structural stability of the material, but also react with the residual alkali on the surface of the positive electrode, such as NaOH, Na2CO3, etc., to convert it into a low-alkalinity material such as sodium tungstate with high ionic conductivity, thereby improving the air stability and processability of the positive electrode material. The reduction of surface residual alkali can effectively reduce the gas production of the positive electrode material during the cycle and improve the cycle stability.

[0009] In the above-mentioned sodium ion battery positive electrode material, the chemical formula of the positive electrode substrate is Na m Ni x Fe y Mn z M n O2, wherein 0<m<1.3, 0<x<1, 0<y<1, 0<z<1, n=1-xyz.

[0010] In the above-mentioned sodium ion battery positive electrode material, the thickness of the positive electrode substrate is 3 to 10 mm, and the thickness of the wrapping layer is 2 to 10 nm.

[0011] A method for preparing a positive electrode material for a sodium ion battery, used for preparing the aforementioned positive electrode material for a sodium ion battery, comprises the following steps:

[0012] S1: Ni x Fe y Mn z M n (OH)2 and sodium-containing compounds are mixed, wherein Ni x Fe y Mn z M n The molar ratio of metal cations to Na ions in (OH)2 is 1:(1-2). After being fully mixed, the mixture is sintered in two stages in an air flow to obtain Na m Ni x Fe y Mn z M n O2 materials;

[0013] S2: Tungsten-containing compound and Na m Ni x Fe y Mn z M nThe O2 material is ball-milled and mixed in a mass ratio of (0.001-0.05):1, and then calcined at 300-600°C for 5-10 hours to obtain a battery positive electrode material coated with a tungsten compound and co-modified with an M element doping;

[0014] Among them, 0<m<1.3, 0<x<1, 0<y<1, 0<z<1, n=1-xyz.

[0015] By coating the material with tungsten-containing compounds and doping with effective elements, the present invention not only improves the structural stability of the material and reduces irreversible phase transitions during cycling, but also reacts with residual alkali on the cathode surface, such as NaOH and Na2CO3, to convert it into a low-alkalinity substance, such as sodium tungstate. This provides the material with high ionic conductivity, improving the air stability and processability of the cathode material. Reducing the residual alkali on the surface effectively reduces gas production during cycling and improves cycling stability.

[0016] In the above-mentioned method for preparing the positive electrode material of sodium ion battery, in step S1, Ni x Fe y Mn z M n (OH)2 and sodium carbonate are mixed, wherein Ni x Fe y Mn z M n The molar ratio of metal cations to Na ions in (OH)2 is 1: (1-1.4). After being fully mixed, the mixture is sintered in two stages in an air flow or an oxygen flow to obtain Na m Ni x Fe y Mn z M n O2 material.

[0017] In the above-mentioned method for preparing the positive electrode material of sodium ion battery, the Ni x Fe y Mn z M n The preparation method of (OH) 2 comprises the following steps:

[0018] S1-1: Mixing a nickel-containing compound, an iron-containing compound, and a manganese-containing compound with a M-containing compound in a molar ratio of Ni:Fe:Mn:M of x:y:z:n, and then neutralizing the solution after mixing evenly to obtain a ternary hydroxide precursor precipitate by a coprecipitation method;

[0019] S1-2: The obtained ternary hydroxide precursor precipitate is filtered, washed, and dried at 150-300°C for 3-6 hours to obtain Ni xFe y Mn z M n (OH)2.

[0020] In the above-mentioned method for preparing the positive electrode material of a sodium ion battery, in step S1-1, the M element in the M-containing compound is one or more of Al, Mg, Ti, Zr, Y, La, Cu, Zn, Ca, Li or B elements.

[0021] In the above-mentioned method for preparing the positive electrode material of a sodium ion battery, the M-containing compound is one of aluminum sulfate solution, titanium sulfate solution, and magnesium sulfate solution.

[0022] In the above-mentioned method for preparing the positive electrode material of a sodium ion battery, in step S1-1, a nickel sulfate compound, an iron sulfate solution, and a manganese sulfate are mixed with an M-containing compound according to a molar ratio of Ni:Fe:Mn:M of x:y:z:n. After mixing evenly, ammonia water and a NaOH solution are added to the solution for neutralization, and a ternary hydroxide precursor precipitate is obtained by a coprecipitation method.

[0023] In the above-mentioned method for preparing the positive electrode material of a sodium ion battery, the tungsten-containing compound is one or more of ammonium metatungstate, ammonium paratungstate, tungsten oxide and tungstic acid.

[0024] In the above-mentioned method for preparing the positive electrode material for a sodium ion battery, the two-stage sintering process in step S1 includes the following steps:

[0025] Ⅰ. Sintering under air flow conditions at 300-450℃ for 8-12 hours;

[0026] Ⅱ. Raise the sintering temperature to 800-1200℃, then sinter in oxygen flow for 8-15 hours. After sintering, cool the furnace to obtain Na m Ni x Fe y Mn z M n O2 material.

[0027] Another aspect of the present invention provides a positive electrode for a sodium ion battery, which uses the aforementioned positive electrode material for a sodium ion battery.

[0028] In another aspect of the present invention, a sodium ion battery is provided, comprising the positive electrode described above.

[0029] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0030] (1) The present invention reduces the residual alkali amount on the surface of the positive electrode material by coating the tungsten-containing compound and the doped effective element, fully improves the air stability of the O3 type sodium ion battery positive electrode material, effectively reduces gas production, reduces the side reaction with the electrolyte, and improves the cycle performance of the material.

[0031] Specifically, the encapsulated tungsten-containing compound and doped effective elements not only reduce the material's irreversible phase transition during cycling and improve its structural stability, but also react with residual alkali on the cathode surface, such as NaOH and Na2CO3, to convert it into low-alkalinity, high-ionic-conductivity materials like sodium tungstate, thereby improving the cathode material's air stability and processability. Reducing the residual alkali on the surface can effectively reduce gassing during cycling and improve cycle stability.

[0032] (2) The coating layer and the doped effective element in the present invention can play a synergistic role. Specifically, the doped elements can effectively inhibit the irreversible phase change during the sodium removal process, and the coated tungsten-containing compound can react with the residual alkali on the surface to form a low-alkalinity fast ion conductor such as sodium tungstate, thereby avoiding gas production caused by strong alkalinity, and also avoiding the instability of the slurry and processing problems caused by strong alkalinity. In addition, the tungsten-containing compound coated on the particle surface can prevent the continuation of the side reaction between the particle surface and the electrolyte, thereby improving the stability of the material during the cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a comparison diagram of the slurry stability of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described in detail below with reference to specific embodiments.

[0035] Example 1

[0036] This embodiment provides a sodium ion battery positive electrode material that is coated with a tungsten compound and co-modified with an Al element doping, comprising a positive electrode substrate and a coating layer, wherein the coating layer is a tungsten compound coated on the surface of the positive electrode substrate, and the chemical formula of the positive electrode substrate is Na 0.99 Ni 0.4 Fe 0.2 Mn 0.35 Al 0.05 O2.

[0037] At the same time, this embodiment also provides a method for preparing the tungsten-containing compound-coated and Al-doped co-modified sodium ion battery positive electrode material, comprising the following steps:

[0038] S1: S1-1: Nickel sulfate solution, iron sulfate solution, manganese sulfate and aluminum sulfate solution were mixed evenly according to the molar ratio of Ni:Fe:Mn:Al of 40:20:35:5, and then 2 mol / L ammonia and NaOH solution were added to the solution for neutralization. The ternary hydroxide precursor Ni was precipitated by coprecipitation. 0.4 Fe 0.2 Mn 0.35 Al 0.05 (OH)2;

[0039] S1-2: The obtained ternary hydroxide precursor precipitate was filtered, washed, and then dried at 200° C. for 4 hours to obtain a dried product 1;

[0040] Subsequently, the obtained hydroxide precursor Ni 0.4 Fe 0.2 Mn 0.35 Al 0.05 (OH)2 and sodium carbonate were mixed in a molar ratio of 1:1.03 between the metal cations in the hydroxide precursor and the Na ions. After thorough mixing, the mixture was sintered in two stages in an air flow:

[0041] Ⅰ. Sintering at 450℃ under air flow conditions for 8 hours.

[0042] II. Raise the sintering temperature to 900°C, sinter in an oxygen flow for 10 hours, and cool the furnace after sintering to obtain Na0.99Ni0.4Fe0.2Mn0.35Al0.05O2 material;

[0043] S2: Put Na 0.99 Ni 0.4 Fe 0.2 Mn 0.35 Al 0.05 O2 and ammonium metatungstate were mixed in a mass ratio of 1:0.02 and calcined at 500°C for 8 hours to obtain a battery positive electrode material coated with tungsten compound and co-modified with Al element doping.

[0044] Example 2

[0045] This embodiment provides a sodium ion battery positive electrode material that is coated with a tungsten compound and co-modified with Mg element doping, including a positive electrode substrate and a coating layer, wherein the coating layer is a tungsten compound coated on the surface of the positive electrode substrate, and the chemical formula of the positive electrode substrate is NaNi 0.4 Fe 0.2 Mn 0.35 Mg 0.05 (OH)2.

[0046] The preparation method of the sodium ion battery positive electrode material coated with a tungsten compound and co-modified with Mg doping comprises the following steps:

[0047] S1: S1-1: Nickel sulfate solution, iron sulfate solution, manganese sulfate and aluminum sulfate solution were mixed evenly according to the molar ratio of Ni:Fe:Mn:Mg of 40:20:35:5, and then 2 mol / L ammonia and NaOH solution were added to the solution for neutralization. The ternary hydroxide precursor Ni was precipitated by coprecipitation. 0.4 Fe 0.2 Mn 0.35 Mg 0.05 (OH) 2; then the obtained precipitate was filtered, washed, and dried at 250 ° C for 3 hours to obtain a dried product 2;

[0048] S1-2: The obtained hydroxide precursor Ni 0.4 Fe 0.2 Mn 0.35 Mg 0.05 (OH)2 and sodium carbonate are mixed in a molar ratio of 1:1.03 between the metal cations in the hydroxide precursor and the Na ions. After being fully mixed, the mixture is sintered in two stages in an air flow or an oxygen flow:

[0049] Ⅰ. Sintering at 550℃ under air flow conditions for 8 hours.

[0050] Ⅱ. Raise the sintering temperature to 1000℃, sinter in oxygen flow for 10 hours, and cool with the furnace after sintering to obtain NaNi 0.4 Fe 0.2 Mn 0.35 Mg 0.05 (OH)2 materials;

[0051] S2: NaNi 0.4 Fe 0.2 Mn 0.35 Mg 0.05 (OH)2 and ammonium metatungstate were mixed in a mass ratio of 1:0.02 and calcined at 500°C for 8 hours to obtain a battery positive electrode material coated with a tungsten compound and co-modified with Mg element doping.

[0052] Example 3

[0053] This embodiment provides a sodium ion battery positive electrode material that is coated with a tungsten compound and co-modified with Mg element doping, including a positive electrode substrate and a coating layer, wherein the coating layer is a tungsten compound coated on the surface of the positive electrode substrate, and the chemical formula of the positive electrode substrate is Na 0.99 Ni 0.4 Fe 0.2 Mn 0.35 Mg 0.05 (OH)2.

[0054] The preparation method of the sodium ion battery positive electrode material coated with a tungsten compound and co-modified with Mg doping comprises the following steps:

[0055] S1: S1-1: Nickel sulfate solution, iron sulfate solution, manganese sulfate and titanium sulfate solution are mixed evenly according to the molar ratio of Ni:Fe:Mn:Ti of 40:20:35:5, and then NaOH solution is added to the solution for neutralization. The ternary hydroxide precursor Ni is precipitated by coprecipitation. 0.4 Fe 0.2 Mn 0.35 Ti 0.05 (OH)2. The obtained precipitate was then filtered, washed, and dried at 150°C for 6 hours to obtain dried product 3;

[0056] The remaining steps are similar to those in Example 1 to prepare a battery positive electrode material coated with a tungsten compound and co-modified with a Ti element doping.

[0057] Example 4

[0058] This embodiment provides a sodium ion battery positive electrode material that is coated with a tungsten compound and co-modified with an Al element doping, comprising a positive electrode substrate and a coating layer, wherein the coating layer is a tungsten compound coated on the surface of the positive electrode substrate, and the chemical formula of the positive electrode substrate is Na 0.99 Ni 0.4 Fe 0.2 Mn 0.35 Al 0.05 O2.

[0059] The method for preparing the positive electrode material of a sodium ion battery comprises the following steps:

[0060] Step S1 is the same as in Example 1;

[0061] Step S2: Na 0.99 Ni 0.4 Fe 0.2 Mn 0.35 Al 0.05 After O2 and tungsten trioxide were ball-milled in a mass ratio of 1:0.03, they were calcined at 550°C for 8 hours to obtain a battery positive electrode material coated with tungsten compound and co-modified with Al element doping.

[0062] Example 5

[0063] This embodiment provides a sodium ion battery positive electrode material that is coated with a tungsten compound and co-modified with an Al element doping, comprising a positive electrode substrate and a coating layer, wherein the coating layer is a tungsten compound coated on the surface of the positive electrode substrate, and the chemical formula of the positive electrode substrate is Na 0.99 Ni 0.4 Fe 0.2 Mn 0.35Al 0.05 O2.

[0064] The method for preparing the positive electrode material of a sodium ion battery comprises the following steps:

[0065] Step S1 is the same as in Example 1;

[0066] Step S2: Na 0.99 Ni 0.4 Fe 0.2 Mn 0.35 Al 0.05 O2 and ammonium paratungstate were mixed in a mass ratio of 1:0.03 and calcined at 550°C for 9 hours to obtain a battery positive electrode material coated with tungsten compound and co-modified with Al element doping.

[0067] Example 6

[0068] This embodiment provides a sodium ion battery positive electrode material that is coated with a tungsten compound and co-modified with Mg element doping, including a positive electrode substrate and a coating layer, wherein the coating layer is a tungsten compound coated on the surface of the positive electrode substrate, and the chemical formula of the positive electrode substrate is Na 0.99 Ni 0.4 Fe 0.2 Mn 0.35 Al 0.05 O2.

[0069] The method for preparing the positive electrode material of a sodium ion battery comprises the following steps:

[0070] Step S1 is the same as in Example 2;

[0071] Step S2: Obtained NaNi 0.4 Fe 0.2 Mn 0.35 Mg 0.05 O2 and ammonium paratungstate were mixed in a mass ratio of 1:0.03, ball-milled, and then calcined at 450°C for 8 hours to obtain a sodium ion battery positive electrode material coated with tungsten compound and co-modified with Mg element doping.

[0072] Example 7

[0073] This embodiment provides a sodium ion battery positive electrode material co-modified with a tungsten compound coating and Ti element doping, comprising a positive electrode substrate and a coating layer, wherein the coating layer is a tungsten compound coated on the surface of the positive electrode substrate, and the chemical formula of the positive electrode substrate is Na 0.99 Ni 0.4 Fe 0.2 Mn 0.35 Al 0.05 O2.

[0074] The method for preparing the positive electrode material of a sodium ion battery comprises the following steps:

[0075] Step S1 is the same as in Example 3;

[0076] Step S2: The obtained Ni 0.4 Fe 0.2 Mn 0.35 Ti 0.05 (OH)2 and tungstic acid were mixed in a mass ratio of 1:0.04 and calcined at 500°C for 10 hours to obtain a battery positive electrode material coated with tungsten compound and co-modified with Ti element doping.

[0077] Example 8

[0078] This embodiment provides a sodium ion battery positive electrode material that is coated with a tungsten compound and co-modified with an Al element doping, comprising a positive electrode substrate and a coating layer, wherein the coating layer is a tungsten compound coated on the surface of the positive electrode substrate, and the chemical formula of the positive electrode substrate is Na 0.97 Ni 0.32 Fe 0.32 Mn 0.32 Al 0.04 O2.

[0079] The method for preparing the positive electrode material of a sodium ion battery comprises the following steps:

[0080] S1: S1-1: Nickel sulfate solution, iron sulfate solution, manganese sulfate and aluminum sulfate solution were mixed evenly according to the molar ratio of Ni:Fe:Mn:Al of 32:32:32:4, and then 2 mol / L ammonia and NaOH solution were added to the solution for neutralization. The ternary hydroxide precursor Ni was precipitated by coprecipitation. 0.32 Fe 0.32 Mn 0.32 Al 0.04 (OH) 2. The obtained precipitate was then filtered, washed, and dried at 200°C for 4 hours to obtain a dried product.

[0081] S1-2: The obtained hydroxide precursor Ni 0.32 Fe 0.32 Mn 0.32 Al 0.04 (OH)2 and sodium carbonate are mixed according to the molar ratio of the metal cation in the hydroxide precursor to the Na ion of 1:1.05. After being fully mixed, the mixture is sintered in two stages in an air flow or an oxygen flow:

[0082] Ⅰ. Sintering at 450℃ under air flow conditions for 8 hours.

[0083] Ⅱ. Raise the sintering temperature to 1000℃, sinter in oxygen flow for 10 hours, and cool in the furnace after sintering to obtain Na 0.97 Ni 0.32 Fe 0.32 Mn 0.32 Al 0.04 O2 materials;

[0084] S2: Put Na 0.97 Ni 0.32 Fe 0.32 Mn 0.32 Al 0.04 O2 and tungsten trioxide were mixed in a mass ratio of 1:0.03 and calcined at 500°C for 8 hours to obtain a sodium ion battery positive electrode material coated with tungsten compound and co-modified with Al element doping.

[0085] Example 9

[0086] This embodiment provides a sodium ion battery positive electrode material that is coated with a tungsten compound and co-modified with Mg element doping, including a positive electrode substrate and a coating layer, wherein the coating layer is a tungsten compound coated on the surface of the positive electrode substrate, and the chemical formula of the positive electrode substrate is Na 0.97 Ni 0.32 Fe 0.32 Mn 0.32 Mg 0.04 O 22 .

[0087] The method for preparing the positive electrode material of a sodium ion battery comprises the following steps:

[0088] S1: S1-1: Nickel sulfate solution, iron sulfate solution, manganese sulfate and aluminum sulfate solution were mixed evenly according to the molar ratio of Ni:Fe:Mn:Mg of 32:32:32:4, and then 2 mol of ammonia and NaOH solution were added to the solution for neutralization. The ternary hydroxide precursor Ni was precipitated by coprecipitation. 0.32 Fe 0.32 Mn 0.32 Mg 0.04 (OH) 2. The obtained precipitate was then filtered, washed, and dried at 200°C for 4 hours to obtain a dried product.

[0089] S1-2: The obtained hydroxide precursor Ni 0.32 Fe 0.32 Mn 0.32 Mg 0.04 (OH)2 and sodium carbonate are mixed according to the molar ratio of the metal cation in the hydroxide precursor to the Na ion of 1:1.05. After being fully mixed, the mixture is sintered in two stages in an air flow or an oxygen flow:

[0090] Ⅰ. Sintering at 450℃ under air flow conditions for 8 hours.

[0091] Ⅱ. Raise the sintering temperature to 1000℃ and sinter in oxygen flow for 10 hours. After sintering, cool the furnace to obtain Na 0.97 Ni 0.32 Fe 0.32 Mn 0.32 Mg 0.04 O2 materials;

[0092] S2: Put Na 0.97 Ni 0.32 Fe 0.32 Mn 0.32 Mg 0.04 After the O2 material and ammonium metatungstate were mixed in a mass ratio of 1:0.03, they were calcined at 550°C for 8 hours to obtain a battery positive electrode material coated with tungsten compound and co-modified with Mg element doping.

[0093] Example 10

[0094] This embodiment provides a sodium ion battery positive electrode material co-modified with a tungsten compound coating and Ti element doping, comprising a positive electrode substrate and a coating layer, wherein the coating layer is a tungsten compound coated on the surface of the positive electrode substrate, and the chemical formula of the positive electrode substrate is Na 0.97 Ni 0.32 Fe 0.32 Mn 0.32 Ti 0.04 O2.

[0095] The method for preparing the positive electrode material of a sodium ion battery comprises the following steps:

[0096] S1: S1-1: Nickel sulfate solution, iron sulfate solution, manganese sulfate and titanium sulfate solution were mixed evenly according to the molar ratio of Ni:Fe:Mn:Ti of 32:32:32:4, and then 2 mol / L ammonia and NaOH solution were added to the solution for neutralization. The ternary hydroxide precursor Ni was precipitated by coprecipitation. 0.32 Fe 0.32 Mn 0.32 Ti 0.04 (OH) 2. The obtained precipitate was then filtered, washed, and dried at 200°C for 4 hours to obtain dried product 10.

[0097] S1-2: The obtained hydroxide precursor Ni 0.32 Fe 0.32 Mn 0.32 Ti 0.04(OH)2 and sodium carbonate are mixed according to the molar ratio of the metal cation in the hydroxide precursor to the Na ion of 1:1.05. After being fully mixed, the mixture is sintered in two stages in an air flow or an oxygen flow:

[0098] Ⅰ. Sintering at 450℃ under air flow conditions for 8 hours.

[0099] Ⅱ. Raise the sintering temperature to 1000℃ and sinter in oxygen flow for 10 hours. After sintering, cool the furnace. 0.97 Ni 0.32 Fe 0.32 Mn 0.32 Ti 0.04 O2 materials;

[0100] S2: Put Na 0.97 Ni 0.32 Fe 0.32 Mn 0.32 Ti 0.04 O2 and ammonium metatungstate were mixed in a mass ratio of 1:0.03 and calcined at 550°C for 8 hours to obtain a sodium ion battery positive electrode material coated with tungsten compound and co-modified with Ti element doping.

[0101] Example 11

[0102] This embodiment provides a positive electrode for a sodium ion battery, using any of the sodium ion battery positive electrode materials of embodiments 1-10.

[0103] Example 12

[0104] This embodiment provides a sodium ion battery, which includes the positive electrode described in Example 11.

[0105] Comparative Example 1

[0106] The method for preparing the positive electrode material of a sodium ion battery comprises the following steps:

[0107] (1) Nickel sulfate solution, ferric sulfate solution, manganese sulfate and aluminum sulfate solution were mixed uniformly according to the molar ratio of Ni:Fe:Mn:Al of 40:20:35:5, and then 2 mL / L ammonia and NaOH solution were added to the solution for neutralization. The ternary hydroxide precursor Ni was precipitated by coprecipitation. 0.4 Fe 0.2 Mn 0.35 Al 0.05 (OH) 2. The obtained precipitate was then filtered, washed, and dried at 200°C for 4 hours to obtain a dried product.

[0108] (2) Ni hydroxide precursor obtained in step (1) 0.4 Fe 0.2Mn 0.35 Al 0.05 (OH)2 and sodium carbonate are mixed according to the molar ratio of metal cations in the hydroxide precursor to Na ions of 1:1.03. After being fully mixed, the mixture is sintered in two stages in air flow or oxygen flow: first, sintering at 450 ° C for 8 hours under air flow conditions, then raising the sintering temperature to 900 ° C, and sintering in oxygen flow for 10 hours. After sintering, the mixture is cooled in the furnace to obtain Na 0.99 Ni 0.4 Fe 0.2 Mn 0.35 Al 0.05 O2 material.

[0109] Comparative Example 2

[0110] (1) Nickel sulfate solution, ferric sulfate solution, manganese sulfate and magnesium sulfate solution were mixed uniformly according to the molar ratio of Ni:Fe:Mn:Mg of 40:20:35:5, and then 2 mol / L ammonia water and NaOH solution were added to the solution for neutralization. The ternary hydroxide precursor Ni was precipitated by coprecipitation. 0.4 Fe 0.2 Mn 0.35 Mg 0.05 (OH) 2. The obtained precipitate was then filtered, washed, and dried at 200°C for 4 hours to obtain dried product 2.

[0111] (2) Ni hydroxide precursor obtained in step (1) 0.4 Fe 0.2 Mn 0.35 Mg 0.05 (OH)2 and sodium carbonate are mixed according to the molar ratio of metal cations in the hydroxide precursor to Na ions of 1:1.03. After being fully mixed, the mixture is sintered in two stages in air flow or oxygen flow: first, sintering at 550 ° C for 8 hours under air flow conditions, then raising the sintering temperature to 1000 ° C, and sintering in oxygen flow for 10 hours. After sintering, the mixture is cooled in the furnace to obtain NaNi 0.4 Fe 0.2 Mn 0.35 Mg 0.05 O2 material.

[0112] Comparative Example 3

[0113] (1) Nickel sulfate solution, ferric sulfate solution and manganese sulfate solution were mixed uniformly according to the molar ratio of Ni:Fe:Mn of 40:20:40, and then NaOH solution was added to the solution for neutralization. The ternary hydroxide precursor Ni was precipitated by coprecipitation. 0.4 Fe 0.2 Mn 0.4(OH) 2. The obtained precipitate was then filtered, washed, and dried at 200°C for 4 hours to obtain a dried product.

[0114] (2) Ni hydroxide precursor obtained in step (1) 0.4 Fe 0.2 Mn 0.4 (OH)2 and sodium carbonate were mixed in a molar ratio of 1:1.03 between the metal cations in the hydroxide precursor and the Na ions. After being fully mixed, the mixture was sintered in an oxygen flow in two stages: first, sintering at 450°C for 8 hours under air flow conditions, then raising the sintering temperature to 900°C and sintering in an oxygen flow for 10 hours. After sintering, the mixture was cooled in the furnace to obtain Na 0.99 Ni 0.4 Fe 0.2 Mn 0.4 O2 material.

[0115] (3) The obtained Na 0.99 Ni 0.4 Fe 0.2 Mn 0.4 O2 and nano-alumina were mixed in a mass ratio of 1:0.03 and calcined at 500 degrees for 8 hours to obtain the product of Comparative Example 3.

[0116] Comparative Example 4

[0117] (1) Nickel sulfate solution, ferric sulfate solution and manganese sulfate were mixed evenly according to the molar ratio of Ni:Fe:Mn of 40:20:40, and then 2 mol / L NaOH solution was added to the solution for neutralization. The ternary hydroxide precursor Ni was precipitated by coprecipitation. 0.4 Fe 0.2 Mn 0.4 (OH)2. The obtained precipitate was then filtered, washed, and dried at 200°C for 4 hours to obtain a dried product 1;

[0118] The hydroxide precursor Ni obtained in step (1) 0.4 Fe 0.2 Mn 0.4 (OH)2 and sodium carbonate were mixed in a molar ratio of 1:1.03 between the metal cations in the hydroxide precursor and the Na ions. After thorough mixing, the mixture was sintered in an oxygen flow in two stages: first, sintering at 450°C for 8 hours under air flow conditions, then raising the sintering temperature to 900°C and sintering in an oxygen flow for 10 hours. After sintering, the mixture was cooled in the furnace to obtain Na 0.99 Ni 0.4 Fe 0.2 Mn 0.4 O2 material.

[0119] (3) Put Na0.99 Ni 0.4 Fe 0.2 Mn 0.4 O2 and nano-magnesium oxide were mixed in a mass ratio of 1:0.03 and calcined at 500 degrees for 8 hours to obtain the product of Comparative Example 4.

[0120] Comparative Example 5

[0121] Steps (1) and (2) are the same as those in Comparative Example 1.

[0122] (3) The obtained Na 0.99 Ni 0.4 Fe 0.2 Mn 0.35 Al 0.05 O2 and nano-alumina were mixed in a mass ratio of 1:0.03 and then calcined at 500°C for 10 hours to finally obtain the product of Comparative Example 5.

[0123] Application Examples

[0124] The method for preparing the products of Examples 1-10 and Comparative Examples 1-5 into soft-pack batteries is as follows:

[0125] (1) Weigh the products of Examples 1-10 and Comparative Examples 1-5, conductive carbon black, conductive carbon tubes, polyvinylidene fluoride, and nitrogen-methyl pyrrolidone in a mass ratio of 97.5:1:0.5:1:40, mix the conductive carbon black, conductive carbon tubes, polyvinylidene fluoride, and nitrogen-methyl pyrrolidone, and stir at 500 rpm for 2 h to obtain a conductive slurry; mix the obtained conductive slurry with the ternary positive electrode material, and stir at 500 rpm for 2 h to obtain a positive electrode slurry.

[0126] (2) The prepared positive electrode slurry was evenly coated on aluminum foil using a doctor blade, and placed in a forced air drying oven and dried at 120°C for 20 minutes. Finally, the dried electrode sheet was rolled and cut to produce a positive electrode sheet.

[0127] (3) The positive electrode sheet obtained by the above method and the negative electrode prepared by hard carbon are assembled into a 1Ah soft-pack battery cell after winding and packaging.

[0128] The soft-packed cells and intermediate products prepared in Examples 1-10 and Comparative Examples 1-5 were subjected to slurry stability tests, gas production tests, cycle retention rate tests, and positive electrode material pH tests, as follows:

[0129] Slurry stability test: The positive electrode slurry obtained by the above method was tested for slurry viscosity every 0.5 h, 1 h, 2 h, 4 h, 8 h, 12 h, 24 h and 48 h to obtain the stability of the slurry in the air.

[0130] pH test of positive electrode material: 10 g of positive electrode powder was soaked in 90 mL of deionized water and magnetically stirred for 5 min, and the pH of the leachate was tested.

[0131] Cycling performance test: The 1Ah soft-pack battery cell prepared by the above method was charged and discharged at a rate of 1C in the voltage range of 1.5-3.95V. When charged to 3.95V, constant voltage charging was performed with a cut-off current of 0.05C to test the cycle capacity retention rate.

[0132] Gas production test: The test battery with 100% SOC was stored at 60°C. The battery volume was measured every 7 days and recharged to 100% SOC. The rate of change in battery volume was the measured gas production rate.

[0133] The test results are shown in the following table.

[0134] Table 1: Test results of Examples 1-10 and Comparative Examples 1-5

[0135] It can be seen from Table 1 that in Examples 1-10, after element doping and coating with tungsten compounds, the pH of the sodium cathode material is effectively reduced, the gas production is also greatly reduced, and the cycle performance is improved.

[0136] FIG1 shows the slurry stability of Example 1 and Comparative Example 1. As shown in FIG1 , the sample coated with W compound and doped with elements in Example 1 has better slurry stability because the residual alkali on its surface is reduced and it is more stable when stored in air.

[0137] The slurry stability test, gas production test, cycle retention rate test, and positive electrode material pH test showed that after element doping and W-containing compound coating, the pH of the material decreased, the cycle retention rate increased, the gas production decreased, and the slurry stability was also greatly improved, which is conducive to the coating of the slurry. This is because Examples 1-10, through element doping and tungsten-containing compound coating, can not only improve the structural stability of the material during the charge and discharge process, but also react with the residual alkali on the surface to form a fast ion conductor. This fast ion conductor coated on the surface of the material can reduce the impact of free residual alkali on the material performance, and can also improve the interface stability of the material, reduce side reactions with the electrolyte, and improve cycle stability.

[0138] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modification, equivalent change, and modification based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A sodium ion battery positive electrode material, characterized in that: It includes a positive electrode substrate and a wrapping layer, wherein the wrapping layer is a tungsten-containing compound coated on the surface of the positive electrode substrate, and the positive electrode substrate is doped with M element, wherein the M element is one or more of Al, Mg, Ti, Zr, Y, La, Cu, Zn, Ca, Li or B elements.

2. The sodium ion battery positive electrode material according to claim 1, characterized in that The chemical formula of the positive electrode substrate is Na m Ni x Fe y Mn z M n O2, wherein 0<m<1.3, 0<x<1, 0<y<1, 0<z<1, n=1-xyz.

3. The sodium ion battery positive electrode material according to claim 1, characterized in that The thickness of the positive electrode substrate is 3-10 μm, and the thickness of the wrapping layer is 2-10 nm.

4. A method for preparing a positive electrode material for a sodium ion battery, characterized in that: The following steps are involved: S1: Ni x Fe y Mn z M n (OH)2 and sodium-containing compounds are mixed, wherein Ni x Fe y Mn z M n The molar ratio of metal cations to Na ions in (OH)2 is 1:(1-2). After being fully mixed, the mixture is sintered in two stages in an air flow to obtain Na m Ni x Fe y Mn z M n O2 materials; S2: Tungsten-containing compounds and Na m Ni x Fe y Mn z M n The O2 material is ball-milled and mixed at a mass ratio of (0.001-0.05):1, and then calcined at 300-600°C for 5-10 hours to obtain a battery positive electrode material coated with a tungsten compound and co-modified with an M element doping; Among them, 0<m<1.3, 0<x<1, 0<y<1, 0<z<1, n=1-xyz.

5. The method for preparing a positive electrode material for a sodium ion battery according to claim 4, characterized in that: In step S1, Ni x Fe y Mn z M n (OH)2 and sodium carbonate are mixed, wherein Ni x Fe y Mn z M n The molar ratio of metal cations to Na ions in (OH)2 is 1:(1-1.4). After being fully mixed, the mixture is sintered in two stages in an air flow or an oxygen flow to obtain Na m Ni x Fe y Mn z M n O2 material.

6. The method for preparing a positive electrode material for a sodium ion battery according to claim 4, characterized in that: The tungsten-containing compound is one or more of ammonium metatungstate, ammonium paratungstate, tungsten oxide and tungstic acid.

7. The method for preparing a positive electrode material for a sodium ion battery according to claim 4, characterized in that: Ni in step S1 x Fe y Mn z M n The preparation method of (OH)2 comprises the following steps: S1-1: Compounds containing nickel, iron and manganese are mixed according to the formula Ni:Fe:Mn:M are mixed in a molar ratio of x:y:z:n, and after being uniformly mixed, the solution is neutralized to obtain a ternary hydroxide precursor precipitate by a coprecipitation method; S1-2: The obtained ternary hydroxide precursor precipitate is filtered, washed, and dried at 150-300°C for 3-6 hours to obtain Ni x Fe y Mn z M n (OH)2.

8. The method for preparing a positive electrode material for a sodium ion battery according to claim 7, characterized in that: In step S1-1, the M element in the M-containing compound is one or more of Al, Mg, Ti, Zr, Y, La, Cu, Zn, Ca, Li or B elements.

9. The method for preparing a positive electrode material for a sodium ion battery according to claim 7, characterized in that: In step S1-1, nickel sulfate compound, iron sulfate solution and manganese sulfate and M-containing compound are mixed according to the molar ratio of Ni:Fe:Mn:M of x:y:z:n. After mixing evenly, ammonia water and NaOH solution are added to the solution for neutralization, and a ternary hydroxide precursor precipitate is obtained by co-precipitation.

10. The method for preparing a positive electrode material for a sodium ion battery according to claim 4, characterized in that: The two-stage sintering process in step S1 includes the following steps: Ⅰ. Sintering for 8 to 12 hours under air flow conditions at 300 to 450°C; Ⅱ. Raise the sintering temperature to 800-1200℃, and then sinter in oxygen flow for 8-15 hours. After sintering, cool the furnace to obtain Na m Ni x Fe y Mn z M n O2 material.

11. A positive electrode of a sodium ion battery, characterized in that: The sodium ion battery positive electrode material according to any one of claims 1 to 3 is used.

12. A sodium ion battery, characterized in that: Comprising the positive electrode according to claim 11.

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