CN115954482B

CN115954482B - Layered oxide composite material, preparation method thereof, positive plate and sodium ion battery

Info

Publication number: CN115954482B
Application number: CN202310249455.6A
Authority: CN
Inventors: 董英男; 王迪; 张继宗; 蒋绮雯
Original assignee: Jiangsu Zenio New Energy Battery Technologies Co Ltd
Current assignee: Jiangsu Zenio New Energy Battery Technologies Co Ltd
Priority date: 2023-03-15
Filing date: 2023-03-15
Publication date: 2023-06-02
Anticipated expiration: 2043-03-15
Also published as: CN115954482A

Abstract

The invention discloses a layered oxide composite material, the molecular formula of which is Na _x Ni _i Fe _j Mn _k M _m O ₂ /KFeF ₃ Wherein: m is Li ⁺ 、B ³⁺ 、Mg ²⁺ 、Al ³⁺ 、K ⁺ 、Ca ²⁺ 、Ti ⁴⁺ 、Co ³⁺ 、V ³⁺ 、V ⁴⁺ 、Cr ³⁺ 、Cu ²⁺ 、Zn ²⁺ 、Zr ⁴⁺ 、Nb ⁵⁺ And Sn (Sn) ⁴⁺ One or more of the following; 0.8<x≤1，0<i≤0.4，0<j≤0.5，0<k≤0.6，0<m is less than or equal to 0.2, and i+j+k+m=1. The invention also discloses a preparation method of the layered oxide composite material, and a positive plate and a sodium ion battery prepared from the layered oxide composite material. The layered oxide composite material improves the structural stability of the existing O3 phase layered oxide and improves the cycle performance and the multiplying power performance of the sodium ion battery.

Description

Layered oxide composite material, preparation method thereof, positive plate and sodium ion battery

Technical Field

The invention relates to the technical field of sodium ion batteries, in particular to a layered oxide composite material and a preparation method thereof, an anode plate and a sodium ion battery.

Background

Among various positive electrode materials of sodium ion batteries, O3-phase layered oxides have received attention because they can provide sufficient sodium in a full battery, have high electrochemical activity, have high theoretical specific capacities, and are easy to synthesize. However, the structural stability of the O3-phase layered oxide material is poor, which results in that the cycle performance and the rate performance of the material are affected to some extent, and practical application of the O3-phase layered oxide is limited.

Therefore, how to improve the cycle performance and the rate performance of the O3 phase layered oxide cathode material becomes one of the key problems in the related art of sodium ion batteries.

Disclosure of Invention

The invention aims to provide a layered oxide composite material for improving the structural stability of layered oxide and further improving the cycle performance and the multiplying power performance of a sodium ion battery.

In order to solve the technical problems, the invention provides the following technical scheme:

the first aspect of the invention provides a layered oxide composite material having a molecular formula of Na _x Ni _i Fe _j Mn _k M _m O ₂ /KFeF ₃ Wherein: m is Li ⁺ 、B ³⁺ 、Mg ²⁺ 、Al ³⁺ 、K ⁺ 、Ca ²⁺ 、Ti ⁴⁺ 、Co ³⁺ 、V ³⁺ 、V ⁴⁺ 、Cr ³⁺ 、Cu ²⁺ 、Zn ²⁺ 、Zr ⁴⁺ 、Nb ⁵⁺ And Sn (Sn) ⁴⁺ One or more of the following; 0.8<x≤1，0<i≤0.4，0<j≤0.5，0<k≤0.6，0<m is less than or equal to 0.2, and i+j+k+m=1.

Further, in the layered oxide composite material, na _x Ni _i Fe _j Mn _k M _m O ₂ Is an O3 phase layered oxide.

The second aspect of the present invention provides a method for preparing a layered oxide composite material, comprising the steps of:

na is mixed with _x Ni _i Fe _j Mn _k M _m O ₂ Powder, KFEF ₃ After ball milling and mixing precursor powder, sintering is carried out in a protective atmosphere to obtain the layered oxide composite material Na _x Ni _i Fe _j Mn _k M _m O ₂ /KFeF ₃ ；

Wherein M is Li ⁺ 、B ³⁺ 、Mg ²⁺ 、Al ³⁺ 、K ⁺ 、Ca ²⁺ 、Ti ⁴⁺ 、Co ³⁺ 、V ³⁺ 、V ⁴⁺ 、Cr ³⁺ 、Cu ²⁺ 、Zn ²⁺ 、Zr ⁴⁺ 、Nb ⁵⁺ And Sn (Sn) ⁴⁺ One of the followingOr a plurality of; 0.8<x≤1，0<i≤0.4，0<j≤0.5，0<k≤0.6，0<m is less than or equal to 0.2, and i+j+k+m=1.

Further, na _x Ni _i Fe _j Mn _k M _m O ₂ Powder and KFEF F ₃ The mass ratio of the precursor powder is 9-9.5:1-0.5;

and/or the rotation speed of the ball milling is 250-500 r/min, and the ball milling time is 2-8 h;

and/or the protective atmosphere is selected from one or more of nitrogen and inert gases;

and/or sintering at the temperature of 350-650 ℃ for 2-6 hours.

Further, the Na _x Ni _i Fe _j Mn _k M _m O ₂ The preparation method of the powder comprises the following steps:

a. ni is added with _i Fe _j Mn _k M _m (OH) ₂ Ball milling and mixing the precursor and a sodium source uniformly;

b. sintering the mixture obtained in the step a to obtain the Na _x Ni _i Fe _j Mn _k M _m O ₂ And (3) powder.

Further, in step a, the sodium source comprises one or more of sodium carbonate, sodium hydroxide, sodium acetate, sodium oxalate, and sodium nitrate;

and/or the sodium source and Ni _i Fe _j Mn _k M _m (OH) ₂ The mol ratio of the precursors is 0.01-1.25:0.01-1;

and/or the rotation speed of the ball milling is 300-800 r/min, and the ball milling time is 0.5-5 h;

in step b, the sintering comprises pre-sintering and high-temperature solid-phase sintering; the presintering temperature is 200-550 ℃, and the presintering time is 1-8 hours; the high-temperature solid-phase sintering temperature is 750-1100 ℃, and the high-temperature solid-phase sintering time is 4-20 h.

Further, the KFEF ₃ The preparation method of the precursor powder comprises the following steps:

c. dropwise adding the solution A and the solution B into the oil phase solvent containing the emulsifier under the condition of stirring to obtain microemulsion;

d. centrifugally separating the microemulsion, collecting precipitate, washing, drying and grinding to obtain the KFEF ₃ Precursor powder;

wherein the solution A contains K ⁺ And Fe (Fe) ²⁺ The solution B is an aqueous solution containing F ^- Is a solution of (a) and (b).

Further, in step c: the emulsifier comprises at least one of cetyl trimethyl ammonium bromide, N-dodecyl dimethylamine and polyoxyethylene ether;

and/or the oil phase solvent comprises at least one of isooctyl alcohol, n-butyl alcohol and octane;

and/or the mass ratio of the emulsifier to the oil phase solvent is 1-1.5:6-8;

and/or the solution A is KNO ₃ And FeCl ₂ Is dissolved in water, the solution B is prepared from NH ₄ F, dissolving in water to obtain the product;

and/or the volume ratio of the solution A to the solution B is 4-6.5:1.5-3;

and/or, in the microemulsion, the molar ratio of potassium nitrate, ferrous chloride and ammonium fluoride is 1:1:3;

and/or the centrifugal separation speed is 2000-3000 r/min, and the centrifugal time is 0.5-1.5 h;

and/or, the washing solution is absolute ethyl alcohol;

and/or the drying temperature is 80-120 ℃ and the drying time is 5-15 h.

In a third aspect, the present invention provides a positive electrode sheet comprising the layered oxide composite material described above or a layered oxide composite material prepared by the method described above.

According to a fourth aspect of the invention, there is provided a sodium ion battery comprising the positive electrode sheet described above.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention introduces KFEF of perovskite structure into the layered oxide material ₃ Calcium titaniumKFEF of ore structure ₃ The nail can be used as a nail to pin the layered structure, so that the layered oxide can maintain the structural stability in the process of removing sodium, and the harmful structural phase change is lightened, so that the structural stability of the layered oxide is improved.

2. In the layered oxide composite material of the invention, KFEF is introduced ₃ The device is also an extremely excellent sodium storage structure, has a three-dimensional rapid ion channel, is extremely convenient for ion transport, and therefore introduces KFEF ₃ The high-rate charge and discharge characteristics of the material are enhanced, and the rate performance of the material is greatly improved.

Drawings

FIG. 1 shows a layered oxide NaNi prepared in example 1 _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ Scanning Electron Microscope (SEM);

FIG. 2 is a KeFF produced in example 1 ₃ Scanning electron microscope images of (2);

FIG. 3 shows the NaNi prepared in example 1 _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ /KFeF ₃ Scanning electron microscope images of materials;

FIG. 4 shows NaNi prepared in example 1 _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ /KFeF ₃ X-ray diffraction pattern (XRD) of the material.

Detailed Description

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.

As one of important positive electrode materials of sodium ion batteries, the O3 phase layered oxide has a problem of poor structural stability, etc., so that the cycle performance and the rate performance are affected to some extent, which limits practical application. At present, the prior art adopts means such as element doping, coating and the like to modify the O3 phase layered oxide, and the means can improve the cycle performance and the multiplying power performance of the layered oxide to a certain extent, but can not solve the problem of poor structural stability of the layered oxide.

In order to solve the above problems of layered oxides, the present invention provides a method for modifying layered oxides by introducing KFEF of perovskite structure ₃ The compound improves the structural stability of the layered oxide, thereby improving the cycle performance and the rate performance of the battery.

Specifically, the molecular formula of the layered oxide composite material provided by the invention is Na _x Ni _i Fe _j Mn _k M _m O ₂ /KFeF ₃ Wherein: m is Li ⁺ 、B ³⁺ 、Mg ²⁺ 、Al ³⁺ 、K ⁺ 、Ca ²⁺ 、Ti ⁴⁺ 、Co ³⁺ 、V ³⁺ 、V ⁴⁺ 、Cr ³⁺ 、Cu ²⁺ 、Zn ²⁺ 、Zr ⁴⁺ 、Nb ⁵⁺ And Sn (Sn) ⁴⁺ One or more of the following; 0.8<x≤1，0<i≤0.4，0<j≤0.5，0<k≤0.6，0<m is less than or equal to 0.2, and i+j+k+m=1.

In the present invention, na _x Ni _i Fe _j Mn _k M _m O ₂ M in (a) may be an element such as NaNi _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ 、NaNi _0.3 Fe _0.15 Mn _0.5 Ti _0.05 O ₂ 、NaNi _0.15 Fe _0.25 Mn _0.55 Cu _0.05 O ₂ May also be a plurality of elements, e.g. NaNi _0.22 Fe _0.18 Mn _0.56 Mg _0.02 Zr _0.02 O ₂ . When M is a plurality of elements, the resulting layered oxide composite has technical effects similar to those when M is an element. Further preferably, na _x Ni _i Fe _j Mn _k M _m O ₂ Is an O3 phase layered oxide.

Na _x Ni _i Fe _j Mn _k M _m O ₂ Is a typical layerThe metal oxide is accompanied by intercalation and deintercalation of sodium ions during charge and discharge of the battery. While local lattice distortion usually occurs during the embedding and extracting process, and the local structural distortion aggravates Na ⁺ And (3) irreversible phase change is caused, finally structural mechanical fatigue is caused, and cracks appear on the surface of the material when the mechanical fatigue is serious, so that the performance of the battery is seriously reduced. KFEF (KFEF-type electronic fuel cell) ₃ Is a compound with perovskite structure, and is prepared by using layered oxide Na _x Ni _i Fe _j Mn _k M _m O ₂ KFEF with perovskite structure introduced therein ₃ The structure can be used as a nail to pin the layered structure, so that the layered oxide can keep the stability of the structure in the process of removing sodium, thereby reducing the harmful structural phase change and forming a mechanically stable structure; second, the perovskite structure is a combination of the layered structure and the rock salt structure, and thus is compatible with Na of the layered structure _x Ni _i Fe _j Mn _k M _m O ₂ Has good adaptability and eliminates the introduction of KeFF ₃ The complexity of the additional structure arises; again, KFEF of perovskite structure ₃ The composite material has the structural characteristic of zero strain, and can avoid larger volume change in the circulation process by introducing the composite material into the layered oxide, so that the structure of the composite material is further stabilized; finally, KFEF ₃ The sodium storage structure is an extremely excellent sodium storage structure, has a three-dimensional rapid ion channel, is extremely convenient for ion transport, and therefore introduces KFEF ₃ The characteristic of high-rate charge and discharge of the composite material is enhanced, and the rate performance of the material is greatly improved.

The invention also discloses a preparation method of the layered oxide composite material, which comprises the following steps:

na is mixed with _x Ni _i Fe _j Mn _k M _m O ₂ Powder, KFEF ₃ Mixing the precursor powder, and sintering in a protective atmosphere to obtain the layered oxide composite material Na _x Ni _i Fe _j Mn _k M _m O ₂ /KFeF ₃ The method comprises the steps of carrying out a first treatment on the surface of the Wherein M is Li ⁺ 、B ³⁺ 、Mg ²⁺ 、Al ³⁺ 、K ⁺ 、Ca ²⁺ 、Ti ⁴⁺ 、Co ³ ⁺ 、V ³⁺ 、V ⁴⁺ 、Cr ³⁺ 、Cu ²⁺ 、Zn ²⁺ 、Zr ⁴⁺ 、Nb ⁵⁺ And Sn (Sn) ⁴⁺ One or more of the following; 0.8<x≤1，0<i≤0.4，0<j≤0.5，0<k≤0.6，0<m is less than or equal to 0.2, and i+j+k+m=1.

In the preparation method, na _x Ni _i Fe _j Mn _k M _m O ₂ Powder and KFEF F ₃ The mass ratio of the precursor powder is preferably 9 to 9.5:1 to 0.5, and may be, for example, 9:1, 9.1:0.9, 9.2:0.8, 9.3:0.7, 9.4:0.6, 9.5:0.5, etc. The mixing is preferably carried out in a ball milling mode, so that the uniformity of powder mixing can be improved. The rotation speed of ball milling is preferably 250-500 r/min, such as 250 r/min, 300r/min, 350 r/min, 400 r/min, 450 r/min, 500r/min and the like; the ball milling time is preferably 2-8 hours, such as 2 hours, 3h, 4h, 5h, 6h, 7h, 8h, etc.

After the powder is uniformly mixed, the mixture is placed in a sintering furnace (such as a tube furnace) and sintered in a protective atmosphere. The protective atmosphere can be one or a mixture of nitrogen and inert gases (such as He, ne and Ar). The same effect can be achieved when the protective atmosphere is one gas or a mixed gas composed of a plurality of gases. The sintering process can be performed at a lower temperature, and the heating rate of the sintering furnace can be 1-10 ℃/min, such as 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min, 10 ℃/min and the like. The sintering temperature is preferably 350 to 650 ℃, for example 350 ℃, 360 ℃, 380 ℃, 400 ℃, 420 ℃, 440 ℃, 450 ℃, 460 ℃, 480 ℃, 500 ℃, 520 ℃, 540 ℃, 550 ℃, 560 ℃, 5980 ℃, 600 ℃, 620 ℃, 640 ℃, 650 ℃, etc.; the sintering time is preferably 2 to 6 hours, for example, 2 hours, 3h, 4h, 5h, 6h, etc.

In the preparation method, na _x Ni _i Fe _j Mn _k M _m O ₂ The preparation method of the powder comprises the following steps:

a. ni is added with _i Fe _j Mn _k M _m (OH) ₂ Uniformly mixing the precursor with a sodium source;

In the step a, the sodium source is one or more of various sodium-containing compounds including, but not limited to, sodium carbonate, sodium hydroxide, sodium acetate, sodium oxalate and sodium nitrate. Wherein, when the sodium source is one or more, the Na can be obtained by sintering _x Ni _i Fe _j Mn _k M _m O ₂ And (3) powder.

In the step a, the sodium source and Ni _i Fe _j Mn _k M _m (OH) ₂ The precursor is according to Na _x Ni _i Fe _j Mn _k M _m O ₂ （0.8<x≤1，0<i≤0.4，0<j≤0.5，0<k≤0.6，0<m.ltoreq.0.2, and i+j+k+m=1). In some embodiments, the sodium source is in combination with Ni _i Fe _j Mn _k M _m (OH) ₂ The mol ratio of the precursor is 0.01-1.25:0.01-1.

In the step a, ni _i Fe _j Mn _k M _m (OH) ₂ The precursor and the sodium source are preferably mixed by ball milling, and the rotational speed of the ball milling is preferably 300-800 r/min, for example 300r/min, 350 r/min, 400 r/min, 450 r/min, 500r/min, 550 r/min, 600 r/min, 650 r/min, 700 r/min, 750 r/min, 800r/min and the like; the ball milling time is preferably 0.5 to 5 hours, for example 0.5 hours, 1h, 2h, 3h, 4h, 5h, etc.

In the step b, the mixture after ball milling is placed in a sintering furnace (such as a muffle furnace), and the temperature is increased for sintering. The heating rate is preferably 1 to 10 ℃ per minute, for example, 1 ℃ per minute, 2 ℃ per minute, 3 ℃ per minute, 4 ℃ per minute, 5 ℃ per minute, 6 ℃ per minute, 7 ℃ per minute, 8 ℃ per minute, 9 ℃ per minute, 10 ℃ per minute, and the like. The sintering process preferably comprises two stages, pre-sintering and high temperature solid phase sintering. Wherein, the temperature of the pre-sintering is preferably 200-550 ℃, such as 200 ℃, 250 ℃, 300 ℃, 350 ℃, 400 ℃, 450 ℃, 500 ℃, 550 ℃ and the like; the pre-sintering time is preferably 1 to 8 hours, for example 1 hour, 2 hours, 3h, 4h, 5h, 6h, 7 hours, 8 hours, etc. The high-temperature solid phase sintering temperature is preferably 750-1100 ℃, such as 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃, 1000 ℃, 1050 ℃, 1100 ℃ and the like; the high temperature solid phase sintering time is preferably 4 to 20 hours, for example, 4 hours, 5h, 6 hours, 8h, 10h, 12h, 15h, 16 h, 18 h, 20h, etc.

In the preparation method, the KeFF ₃ The preparation method of the precursor powder comprises the following steps:

d. centrifugally separating the microemulsion, collecting precipitate, washing, drying and grinding to obtain the KFEF ₃ Precursor powder.

In the step c, the solution A contains K ⁺ And Fe (Fe) ²⁺ Solution B is an aqueous solution containing F ^- Is a solution of (a) and (b). Under the condition of continuous stirring, the solution A and the solution B (namely water phase) are dropwise added into an oil phase solvent (oil phase) containing an emulsifier to form uniform and transparent microemulsion; after forming the microemulsion, stirring continuously for a period of time to enable the droplets to be in contact with each other to generate chemical reaction to generate KFEF ₃ And (3) precipitate. Wherein the emulsifier comprises at least one of cetyl trimethyl ammonium bromide, N-dodecyl dimethylamine and polyoxyethylene ether; the oil phase solvent comprises at least one of isooctyl alcohol, n-butyl alcohol and octane. The mass ratio of the emulsifier to the oil phase solvent is 1-1.5:6-8, for example 1:4, 1:5, 1:6, 1:7, 1:8, preferably 1:6. The volume ratio of the solution A to the solution B is 4-6.5:1.5-3, such as 4:1, 4:2, 5:2, 4:3, etc., preferably 5:2.

Preferably, the solution A is KNO ₃ And FeCl ₂ Is dissolved in water, the solution B is prepared from NH ₄ F is dissolved in water. In the microemulsion, the molar ratio of potassium nitrate to ferrous chloride to ammonium fluoride is 1:1:3.

In the step d, the microemulsion is centrifuged to separate out a precipitate. The centrifugal separation speed is excellent2000-3000 r/min, such as 2000r/min, 2200 r/min, 2400 r/min, 2500 r/min, 2600 r/min, 2800 r/min, 3000r/min, etc.; the centrifugation time is preferably 0.5 to 1.5 hours, for example, 0.5 hours, 0.6 h, 0.8 h, 1.0 h, 1.2 h, 1.5h, and the like. After collecting the precipitate, washing is performed, and the solvent for washing is preferably absolute ethanol. In the drying, the materials are preferably dried in a forced air drying oven at a temperature of preferably 80-120 ℃, such as 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃ and the like; the drying time is preferably 5 to 15 hours, for example 5 hours, 6h, 7 hours, 8 hours, 9 hours, 10h, 11 h, 12h, 13 h, 14 h, 15h, etc. Grinding the dried precipitate to obtain KFEF ₃ Precursor powder.

On the basis of the layered oxide composite material, the invention also provides a sodium ion battery, which comprises a positive plate, a negative plate, a diaphragm and electrolyte, wherein the diaphragm is arranged to isolate the positive plate from the negative plate.

In the sodium ion battery, the positive plate can be prepared by adopting a common plate preparation process in the field. The preparation method is as follows: and mixing the layered oxide composite material, the conductive agent and the binder to prepare slurry, coating the slurry on at least one side surface of the positive electrode current collector, and drying and tabletting to obtain the positive electrode plate.

In the preparation method of the positive plate, the type and the content of the conductive agent are not particularly limited, and can be selected according to actual requirements. In some embodiments, the conductive agent includes at least one of conductive carbon black, carbon nanotubes, acetylene black, graphene, ketjen black, carbon nanofibers, and the like. It will be appreciated that other conductive agents capable of performing the functions of the present application may be selected as desired without limitation without departing from the spirit of the present application.

In the preparation method of the positive plate, the types and the content of the binder are not particularly limited, and can be selected according to actual requirements. In some embodiments, the binder includes at least one of polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, sodium carboxymethyl cellulose, polymethacrylate, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyamide, polyimide, polyacrylate, styrene butadiene rubber, sodium alginate, chitosan, polyethylene glycol, guar gum, and the like.

The type of the positive electrode current collector is not particularly limited, and may be selected according to practical requirements, for example, the positive electrode current collector may be an aluminum foil, a nickel foil or a polymer conductive film, and preferably the positive electrode current collector is an aluminum foil.

In the sodium ion battery, the type of separator is not particularly limited, and any separator material used in conventional batteries, such as polyethylene, polypropylene, polyvinylidene fluoride, nonwoven fabric, multilayer composite films thereof, and modified separators such as ceramic modification and PVDF modification of the separator may be used.

In the sodium ion battery, the electrolyte can be one or more of organic liquid electrolyte, organic solid electrolyte, solid ceramic electrolyte and gel electrolyte. Preferably, the electrolyte is an organic liquid electrolyte obtained by dissolving sodium salt in a nonaqueous organic solvent; wherein the sodium salt may comprise sodium difluorophosphate (NaPO) ₂ F ₂ ) Sodium hexafluorophosphate (NaPF) ₆ ) One or more of sodium bis (fluorosulfonyl) imide (NaFSI), sodium bis (trifluoromethanesulfonyl) imide (naftsi), and sodium difluoro (NaDFOB) oxalato borate (NaDFOB). The nonaqueous organic solvent may include one or more of cyclic carbonate, chain carbonate, and carboxylate. Wherein the cyclic carbonate can be selected from one or more of Ethylene Carbonate (EC), propylene Carbonate (PC), butylene carbonate and gamma-butyrolactone; the chain carbonate may be selected from one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl Propyl Carbonate (MPC), methyl Acetate (MA), ethyl Acetate (EA), and Ethyl Propionate (EP).

In some embodiments, a certain amount of additives may also be added to the organic liquid electrolyte. The additive may include one or more of Vinylene Carbonate (VC), vinyl carbonate (VEC), vinyl sulfate (DTD), ethylene Sulfite (ES), methylene Methane Disulfonate (MMDS), 1, 3-Propane Sultone (PS), propylene sultone (PES), propylene sulfate (TMS), trimethylsilyl phosphate (TMSP), trimethylsilyl borate (TMSB), fluoroethylene carbonate (FEC).

The present invention will be further described with reference to the accompanying drawings and specific examples, which are not intended to be limiting, so that those skilled in the art will better understand the invention and practice it.

The experimental methods used in the following examples are conventional methods unless otherwise specified, and materials, reagents, etc. used, unless otherwise specified, are commercially available.

1. XRD test method

Grinding the prepared powder material, transferring to a glass sheet object stage, and transferring to an X-ray diffractometer for scanning test, wherein the scanning range is 10-80 degrees, and the scanning speed is 5 degrees/min.

2. Assembly and testing of sodium ion batteries

Grinding the anode material, the conductive agent Super P and the binder PVDF uniformly according to the mass ratio of 8:1:1, adding a proper amount of NMP to prepare slurry, uniformly coating the slurry on the pretreated aluminum foil, drying the aluminum foil for 1h at 80 ℃ in a blast drying box, and drying the aluminum foil for 12h at 120 ℃ in a vacuum drying box; then cutting into 14mm round positive plates by a cutting machine. Sodium metal sheet with the diameter of 14mm and the thickness of 0.2mm is taken as a negative electrode, sodium perchlorate solution with the concentration of 0.1mol/L is taken as electrolyte (the solvent is ethylene carbonate and dimethyl carbonate with the volume ratio of 1:1), whatman GF/F glass fiber with the diameter of 16mm is taken as a diaphragm, and the CR2032 button cell is assembled in a glove box filled with high-purity argon.

The assembled CR2032 coin cell was tested for charge and discharge at a current density of 0.1C using a constant current charge and discharge mode. The test items include: first charge and discharge, rate capability, and capacity retention rate of 100 cycles of 1C charge and discharge.

Example 1

(1) Ni was added in a molar ratio of 1:1.03 _0.15 Fe _0.15 Mn _0.65 Mg _0.05 (OH) ₂ Placing the precursor and sodium acetate into a ball milling tank with the rotating speed of 300r/min, and forming ballsGrinding for 2h to allow them to be thoroughly mixed. Placing the mixed powder in a muffle furnace, presintering for 3h at 200 ℃ at a heating rate of 5 ℃/min, then raising the temperature to 800 ℃ for high-temperature solid-phase sintering for 10h, naturally cooling and grinding to obtain the layered oxide material NaNi _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ Is a black powder of (a).

(2) Adding cetyl trimethyl ammonium bromide into isooctyl alcohol, and mixing to prepare solution C; adding potassium nitrate and ferrous chloride into deionized water, and mixing to prepare solution A; adding ammonium fluoride into deionized water, and mixing to prepare a solution B; wherein, in the solution C, the mass ratio of the cetyl trimethyl ammonium bromide to the isooctyl alcohol is 1:5.5; in the solution A, the molar ratio of potassium nitrate to ferrous chloride is 1:1. Then, under the condition of continuous stirring, the solution A and the solution B are sequentially added into the solution C drop by drop to form uniform and transparent microemulsion, and stirring is continued for a period of time. In the microemulsion, the molar ratio of potassium nitrate to ferrous chloride to ammonium fluoride is 1:1:3. Separating the obtained microemulsion for 0.5h at a centrifugal speed of 2000 r/min; washing the precipitate obtained by centrifugation with absolute ethanol, drying in a forced air drying oven at 120deg.C for 10 hr, and grinding to obtain KFEF ₃ Is a precursor powder of (a).

(3) According to the mass ratio of 9.3:0.7, the obtained NaNi is prepared _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ Black powder and kfefs ₃ The precursor powder of (2) is put into a ball mill with the rotating speed of 500r/min, and ball milling is carried out for 2 hours, so that the precursor powder and the ball mill are uniformly mixed. Then placing the mixed powder into a tube furnace, heating to 500 ℃ at a heating rate of 5 ℃/min, and sintering for 4 hours in an inert atmosphere to obtain NaNi _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ /KFeF ₃ A material.

Example 2

(1) Ni was added in a molar ratio of 1:1.03 _0.3 Fe _0.15 Mn _0.5 Ti _0.05 (OH) ₂ The precursor and sodium nitrate are placed in a ball milling tank with the rotating speed of 800r/min, and ball milling is carried out for 0.5h to fully mix the precursor and the sodium nitrate. Placing the mixed powder into a muffle furnace at a speed of 5 ℃/minPre-sintering for 5h at 400 ℃, then raising the temperature to 900 ℃ and sintering for 12h in a high-temperature solid phase, and naturally cooling and grinding to obtain the layered oxide material NaNi _0.3 Fe _0.15 Mn _0.5 Ti _0.05 O ₂ Is a black powder of (a).

(3) According to the mass ratio of 9.5:0.5, the obtained NaNi is prepared _0.3 Fe _0.15 Mn _0.5 Ti _0.05 O ₂ Black powder and kfefs ₃ The precursor powder of (2) is put into a ball mill with the rotating speed of 500r/min, and ball milling is carried out for 2 hours, so that the precursor powder and the ball mill are uniformly mixed. Then placing the mixed powder into a tube furnace, heating to 600 ℃ at a heating rate of 5 ℃/min, and sintering for 2 hours in an inert atmosphere to obtain NaNi _0.3 Fe _0.15 Mn _0.5 Ti _0.05 O ₂ /KFeF ₃ A material.

Example 3

(1) Ni was added in a molar ratio of 1:1.03 _0.15 Fe _0.25 Mn _0.55 Cu _0.05 (OH) ₂ The precursor and sodium nitrate are placed in a ball milling tank with the rotating speed of 500r/min, and ball milling is carried out for 1.5h to fully mix the precursor and the sodium nitrate. Placing the mixed powder into a muffle furnace, presintering at 400 ℃ for 5h at a heating rate of 5 ℃/min, and then increasing the temperature to 1100 ℃ for high-temperature solid-phase sinteringAfter bonding for 20 hours, naturally cooling and grinding to obtain a layered oxide material NaNi _0.15 Fe _0.25 Mn _0.55 Cu _0.05 O ₂ Is a black powder of (a).

(3) According to the mass ratio of 9.7:0.3, the obtained NaNi _0.15 Fe _0.25 Mn _0.55 Cu _0.05 O ₂ Black powder and kfefs ₃ The precursor powder of (2) is put into a ball mill with the rotating speed of 500r/min, and ball milling is carried out for 2 hours, so that the precursor powder and the ball mill are uniformly mixed. Then placing the mixed powder into a tube furnace, heating to 600 ℃ at a heating rate of 5 ℃/min, and sintering for 2 hours in an inert atmosphere to obtain NaNi _0.15 Fe _0.25 Mn _0.55 Cu _0.05 O ₂ /KFeF ₃ A material.

Example 4

(1) Ni was added in a molar ratio of 1:1.03 _0.22 Fe _0.18 Mn _0.56 Mg _0.02 Zr _0.02 (OH) ₂ The precursor and sodium nitrate are placed in a ball milling tank with the rotating speed of 500r/min, and ball milling is carried out for 2 hours to fully mix the precursor and the sodium nitrate. Placing the mixed powder in a muffle furnace, presintering for 4h at 300 ℃ at a heating rate of 5 ℃/min, then raising the temperature to 900 ℃ for high-temperature solid-phase sintering for 12h, naturally cooling and grinding to obtain the layered oxide materialMaterial NaNi _0.22 Fe _0.18 Mn _0.56 Mg _0.02 Zr _0.02 O ₂ Is a black powder of (a).

(3) According to the mass ratio of 9.5:0.5, the obtained NaNi is prepared _0.22 Fe _0.18 Mn _0.56 Mg _0.02 Zr _0.02 O ₂ Black powder and kfefs ₃ The precursor powder of (2) is put into a ball mill with the rotating speed of 500r/min, and ball milling is carried out for 2 hours, so that the precursor powder and the ball mill are uniformly mixed. Then placing the mixed powder into a tube furnace, heating to 600 ℃ at a heating rate of 5 ℃/min, and sintering for 2 hours in an inert atmosphere to obtain NaNi _0.22 Fe _0.18 Mn _0.56 Mg _0.02 Zr _0.02 O ₂ /KFeF ₃ A material.

Comparative example 1

Ni was added in a molar ratio of 1:1.03 _0.15 Fe _0.15 Mn _0.65 Mg _0.05 (OH) ₂ The precursor and sodium acetate are placed in a ball milling tank with the rotating speed of 300r/min, and ball milling is carried out for 2 hours to fully mix the precursor and the sodium acetate. Placing the mixed powder in a muffle furnace, presintering for 3h at 200 ℃ at a heating rate of 5 ℃/min, then raising the temperature to 800 ℃ for high-temperature solid-phase sintering for 10h, naturally cooling and grinding to obtain the layered oxide material NaNi _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ Is a black powder of (a).

Comparative example 2

Ni was added in a molar ratio of 1:1.03 _0.3 Fe _0.15 Mn _0.5 Ti _0.05 (OH) ₂ The precursor and sodium nitrate are placed in a ball milling tank with the rotating speed of 800r/min, and ball milling is carried out for 0.5h to fully mix the precursor and the sodium nitrate. Placing the mixed powder in a muffle furnace, presintering at 400 ℃ for 5h at a heating rate of 5 ℃/min, then raising the temperature to 900 ℃ for high-temperature solid-phase sintering for 12h, naturally cooling and grinding to obtain the layered oxide material NaNi _0.3 Fe _0.15 Mn _0.5 Ti _0.05 O ₂ Is a black powder of (a).

Comparative example 3

Ni was added in a molar ratio of 1:1.03 _0.15 Fe _0.25 Mn _0.55 Cu _0.05 (OH) ₂ The precursor and sodium nitrate are placed in a ball milling tank with the rotating speed of 500r/min, and ball milling is carried out for 1.5h to fully mix the precursor and the sodium nitrate. Placing the mixed powder in a muffle furnace, presintering at 400 ℃ for 5h at a heating rate of 5 ℃/min, then raising the temperature to 1100 ℃ for high-temperature solid-phase sintering for 20h, naturally cooling and grinding to obtain the layered oxide material NaNi _0.15 Fe _0.25 Mn _0.55 Cu _0.05 O ₂ Is a black powder of (a).

Comparative example 4

Ni was added in a molar ratio of 1:1.03 _0.22 Fe _0.18 Mn _0.56 Mg _0.02 Zr _0.02 (OH) ₂ The precursor and sodium nitrate are placed in a ball milling tank with the rotating speed of 500r/min, and ball milling is carried out for 2 hours to fully mix the precursor and the sodium nitrate. Placing the mixed powder in a muffle furnace, presintering for 4h at 300 ℃ at a heating rate of 5 ℃/min, then raising the temperature to 900 ℃ for high-temperature solid-phase sintering for 12h, naturally cooling and grinding to obtain the layered oxide material NaNi _0.22 Fe _0.18 Mn _0.56 Mg _0.02 Zr _0.02 O ₂ Is a black powder of (a).

The following is directed to NaNi prepared in example 1 _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ /KFeF ₃ The materials were subjected to characterization tests.

FIGS. 1-3 are NaNi respectively _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ 、KFeF ₃ And NaNi _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ /KFeF ₃ Scanning Electron Microscope (SEM) of the material. As can be seen from the figure, the layered oxide NaNi _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ The surface is smoother, and NaNi _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ /KFeF ₃ The surface of the material showed irregular shape of coating, and the surface became rough, which indicates that the layer oxide NaNi _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ KFEF F having perovskite structure introduced successfully ₃ 。

FIG. 4 is NaNi _0.15 Fe _0.15 Mn _0.65 Mg _0.05 O ₂ /KFeF ₃ XRD diffraction patterns of the material, as can be seen from the figures, are substantially identical to the standard peaks of the O3 phase layered oxide standard card; in addition, diffraction peaks at 31 degrees and 45 degrees appear in the diffraction pattern of the material, and the diffraction peaks are KFEF ₃ Is shown to successfully incorporate KFEF in the layered oxide ₃ 。

The electrochemical test results of the batteries of each example and comparative example under the condition that the discharge cut-off voltage was 2.0V and the charge cut-off voltage was 4.0V are shown in table 1.

TABLE 1

Group of	0.1C first-turn discharge capacity (mAh/g)	1C discharge capacity (mAh/g)	2C discharge capacity (mAh/g)	5C discharge capacity (mAh/g)	1C 100 cycle capacity retention (%)
						Example 1	128.6	122.4	112.1	98.4	95.6
Example 2	137.3	129.3	120.9	103.6	94.5
						Example 3	130.1	124.5	112.1	99.8	96.8
Example 4	133.5	127.1	115.6	100.5	94.6
						Comparative example 1	132.3	119.3	107.2	87.1	86.9
Comparative example 2	141.5	120.2	112.1	79.6	85.1
						Comparative example 3	133.6	120.6	109.1	90.2	88.9
Comparative example 4	137.2	122.4	110.4	78.8	83.6

The host materials of examples 1 to 4 and comparative examples 1 to 4 were layered metal oxides, and were the same type and preparation method. As can be seen from the results of Table 1, examples 1 to 4 are KFEF F having a perovskite structure ₃ Is introduced into the layered metal oxide, and has a perovskite structure KFEF ₃ Sodium ions are not present in the solution, and thus the gram capacity is slightly decreased. However, na _x Ni _i Fe _j Mn _k M _m O ₂ /KFeF ₃ The multiplying power performance and the cycle stability of the material are both goodThe gram capacity plays an advantage obviously under the condition of large-rate charge and discharge.

In summary, the perovskite structure is introduced into the layered oxide by low-temperature sintering, so that the structure of the material is stabilized, the ionic conductivity of the material is improved, and the cycle stability and the multiplying power performance of the material are greatly improved.

The above-described embodiments are merely preferred embodiments for fully explaining the present invention, and the scope of the present invention is not limited thereto. Equivalent substitutions and modifications will occur to those skilled in the art based on the present invention, and are intended to be within the scope of the present invention. The protection scope of the invention is subject to the claims.

Claims

1. A layered oxide composite material is characterized in that the molecular formula of the layered oxide composite material is Na _x Ni _i Fe _j Mn _k M _m O ₂ /KFeF ₃ It is prepared by mixing Na _x Ni _i Fe _j Mn _k M _m O ₂ Powder, KFEF ₃ The precursor powder is obtained by ball milling and mixing and then sintering in a protective atmosphere; wherein: m is Li ⁺ 、B ³⁺ 、Mg ²⁺ 、Al ³⁺ 、K ⁺ 、Ca ²⁺ 、Ti ⁴⁺ 、Co ³⁺ 、V ³⁺ 、V ⁴⁺ 、Cr ³⁺ 、Cu ²⁺ 、Zn ²⁺ 、Zr ⁴⁺ 、Nb ⁵⁺ And Sn (Sn) ⁴⁺ One or more of the following; 0.8<x≤1，0<i≤0.4，0<j≤0.5，0<k≤0.6，0<m is less than or equal to 0.2, and i+j+k+m=1.

2. A method for preparing a layered oxide composite material, comprising the steps of:

Wherein M is Li ⁺ 、B ³⁺ 、Mg ²⁺ 、Al ³⁺ 、K ⁺ 、Ca ²⁺ 、Ti ⁴⁺ 、Co ³⁺ 、V ³⁺ 、V ⁴⁺ 、Cr ³⁺ 、Cu ²⁺ 、Zn ²⁺ 、Zr ⁴⁺ 、Nb ⁵⁺ And Sn (Sn) ⁴⁺ One or more of the following; 0.8<x≤1，0<i≤0.4，0<j≤0.5，0<k≤0.6，0<m is less than or equal to 0.2, and i+j+k+m=1.

3. The method for producing a layered oxide composite material according to claim 2, wherein Na _x Ni _i Fe _j Mn _k M _m O ₂ Powder and KFEF F ₃ The mass ratio of the precursor powder is 9-9.5:1-0.5;

and/or sintering at the temperature of 350-650 ℃ for 2-6 hours.

4. The method for producing a layered oxide composite according to claim 2, wherein the Na _x Ni _i Fe _j Mn _k M _m O ₂ The preparation method of the powder comprises the following steps:

5. A process for producing a layered oxide composite as claimed in claim 4, wherein,

in the step a, the sodium source comprises one or more of sodium carbonate, sodium hydroxide, sodium acetate, sodium oxalate and sodium nitrate;

6. The method for producing a layered oxide composite according to claim 2, wherein the kfefs ₃ The preparation method of the precursor powder comprises the following steps:

7. The method for producing a layered oxide composite as claimed in claim 6, wherein in step c: the emulsifier comprises at least one of cetyl trimethyl ammonium bromide, N-dodecyl dimethylamine and polyoxyethylene ether;

and/or the mass ratio of the emulsifier to the oil phase solvent is 1-1.5:6-8;

and/or the volume ratio of the solution A to the solution B is 4-6.5:1.5-3;

and/or, the washing solution is absolute ethyl alcohol;

and/or the drying temperature is 80-120 ℃ and the drying time is 5-15 h.

8. A positive electrode sheet comprising the layered oxide composite material according to claim 1 or the layered oxide composite material produced by the production method according to any one of claims 2 to 7.

9. A sodium ion battery comprising the positive electrode sheet of claim 8.