CN117223124A

CN117223124A - High-entropy oxide doped coated co-modified cathode material, preparation method and application

Info

Publication number: CN117223124A
Application number: CN202380009340.8A
Authority: CN
Inventors: 程江辉; 李长东; 阮丁山; 刘伟健; 汪乾; 黄耀良
Original assignee: Hunan Brunp Recycling Technology Co Ltd; Guangdong Brunp Recycling Technology Co Ltd
Current assignee: Hunan Brunp Recycling Technology Co Ltd; Guangdong Brunp Recycling Technology Co Ltd
Priority date: 2023-06-07
Filing date: 2023-06-07
Publication date: 2023-12-12

Abstract

The invention discloses a high-entropy oxide doped coating co-modified positive electrode material, a preparation method and application thereof, wherein the positive electrode material comprises a substrate and a high-entropy oxide, a part of the high-entropy oxide is coated on the surface of the substrate to form a coating layer, a part of the high-entropy oxide enters the surface layer of the substrate to form a doped layer, and the substrate is O3-shaped layered transition metal oxide. The high-entropy oxide coating substrate has excellent effect on multiplying power and cycle performance of the positive electrode material of the sodium ion battery.

Description

High-entropy oxide doped coated co-modified cathode material, preparation method and application

Technical Field

The disclosure relates to the technical field of sodium ion battery cathode materials, and in particular relates to a high-entropy oxide doped coating co-modified cathode material, a preparation method and application.

Background

Sodium Ion Batteries (SIB) are paid attention to in large-scale energy storage systems due to the advantages of low cost, abundant sodium resources and the like, and the O3-shaped layered transition metal oxide positive electrode material has high theoretical capacity and simple structure and becomes one of the best choices of the positive electrode materials of the sodium ion batteries. However, in the charge and discharge process, the transition metal layer is easy to relatively slide and distort, so that the structure rearranges and complex phase change is generated, and the problems of low energy efficiency, poor cycle stability and the like of the battery are caused.

In view of this, the present disclosure is specifically proposed.

Disclosure of Invention

The invention aims to provide a high-entropy oxide doped coating co-modified positive electrode material, a preparation method and application thereof, and solve the problems of low energy efficiency and poor cycling stability of a battery when an O3 type layered transition metal oxide positive electrode material is applied to a sodium ion battery.

The present disclosure is implemented as follows:

in a first aspect, the present disclosure provides a high entropy oxide doped coated co-modified cathode material, including a substrate and a high entropy oxide, wherein a part of the high entropy oxide is coated on the surface of the substrate to form a coating layer, and a part of the high entropy oxide enters the surface layer of the substrate to form a doped layer;

the base material is O3 type layered transition metal oxide, and the structural formula of the high entropy oxide is A _a B _b C _c D _d E _e (M) _m O ₂ Of which 0.15<a<0.25，0.15<b<0.25，0.15<c<0.25，0.15<d<0.25，0.15<e<0.25，m<0.1, a+b+c+d+e+m=1, said A, B, C, D, E being selected from five of Li, na, mg, ca, al, zn, sc, ti, V, cr, mn, fe, co, Y, zr, nb, mo, ga, te, sb, in, ce and Sn, M being selected from at least one of Li, na, mg, ca, al, zn, sc, ti, V, cr, mn, fe, co, Y, zr, nb, mo, ga, te, sb, in, ce and Sn.

In an alternative embodiment, m > 0.

In an alternative embodiment, the substrate is of the formula Na _x Ni _y Mn _z (T) _t O ₂ T is at least one of Cu, cr, fe, zn, ti and V, 0.8<x<Y is more than or equal to 1 and less than or equal to 0.5, z is more than or equal to 0 and less than or equal to 1.0, t is more than or equal to 0 and less than or equal to 0.2, and y+z+t=1.

In an alternative embodiment, T is Fe.

In an alternative embodiment, the high entropy oxide is a nanoscale high entropy oxide.

In an alternative embodiment, the high entropy oxide has a particle size of less than 200nm.

In an alternative embodiment, the mass fraction of high entropy oxide in the positive electrode material is less than 5%.

In an alternative embodiment, the positive electrode material D50 is 5um to 10um.

In a second aspect, the present disclosure provides a method for preparing a high entropy oxide doped coated co-modified cathode material according to any one of the foregoing embodiments, including sintering a substrate having a high entropy oxide attached to a surface thereof, to obtain the high entropy oxide doped coated co-modified cathode material.

In an alternative embodiment, further comprising the preparation of a substrate having a high entropy oxide attached to the surface: comprising heating a mixed solution of a substrate, a metal salt and a solvent to obtain a substrate having a high entropy oxide attached to the surface.

In an alternative embodiment, in the step of preparing the substrate with the high-entropy oxide attached to the surface, the mass fraction of the substrate in the mixed solution is 25% -35%, and the mass fraction of the metal salt is 3.5% -4.5%.

In an alternative embodiment, in the preparation step of the substrate with the high-entropy oxide attached to the surface, the heating temperature is 60-150 ℃ and the holding time is 1-6 h.

In an alternative embodiment, the preparation step of the substrate with the high entropy oxide attached to the surface is performed in a closed reactor.

In an alternative embodiment, the process of preparing the substrate with the high entropy oxide attached to the surface is accompanied by agitation.

In an alternative embodiment, the stirring speed is 100rpm to 500rpm.

In an alternative embodiment, batch stirring is used for stirring.

In an alternative embodiment, in the preparation step of the substrate with the high entropy oxide attached to the surface, each stirring is performed for 50s to 70s, and each stirring is performed for 8min to 12 min.

In an alternative embodiment, in the preparation step of the substrate having the high-entropy oxide attached to the surface, the metal salt is 5 or more of Li salt, na salt, mg salt, ca salt, al salt, zn salt, sc salt, ti salt, V salt, cr salt, mn salt, fe salt, co salt, Y salt, zr salt, nb salt, mo salt, ga salt, te salt, sb salt, in salt, and Sn salt.

In an alternative embodiment, the metal salt is at least one of nitrate and chloride.

In an alternative embodiment, the solvent is ethanol, oleylamine, and hexane in a ratio of 1 (0.9-1.1): 2.5-3.5.

In an alternative embodiment, the reaction solution is further subjected to solid-liquid separation after the completion of heating, and the separated solid phase is dried.

In an alternative embodiment, the drying temperature is 75 ℃ to 85 ℃ and the drying time is more than 8 hours.

In an alternative embodiment, the sintering step is performed at a sintering temperature of 800-1100 ℃ for a period of 4-15 hours.

In an alternative embodiment, the sintering step is carried out at a temperature of 880 ℃ to 980 ℃ and for a holding time of 8h to 15h.

In an alternative embodiment, the sintering atmosphere is air or oxygen.

In an alternative embodiment, the method further comprises the step of preparing the substrate: comprising sintering a mixture of an oxide and a sodium source to obtain a substrate.

In an alternative embodiment, the oxide includes at least one of nickel oxide, manganese oxide, chromium oxide, iron oxide, vanadium oxide, and titanium oxide.

In alternative embodiments, the sodium source is one or more of sodium carbonate, sodium hydroxide, sodium oxide, sodium peroxide.

In an alternative embodiment, the substrate is prepared at a sintering temperature of 800 ℃ to 1000 ℃ for a sintering time of 6 hours to 24 hours.

In an alternative embodiment, the substrate is prepared at a sintering temperature of 850 ℃ to 950 ℃ and a holding time of 8 hours to 15 hours.

In a third aspect, the present disclosure provides a positive electrode material according to any one of the preceding embodiments or a positive electrode material obtained by a method according to any one of the preceding embodiments, for use in a sodium ion battery.

In a fourth aspect, the present disclosure provides an electrode comprising the positive electrode material of any one of the preceding embodiments or the positive electrode material obtained by the method of any one of the preceding embodiments.

In a fifth aspect, the present disclosure provides a sodium ion battery comprising an electrode as described in the previous embodiments.

In a sixth aspect, the present disclosure provides an electrical device, including a sodium ion battery according to the foregoing embodiment.

The present disclosure has the following beneficial effects:

the high-entropy oxide in the disclosure is used as a single-phase solid solution material with multiple metal elements sharing the same atomic site and cations in disordered distribution, and the metal elements tend to randomly generate oxidation-reduction reaction due to disordered metal layers, so that Na can be inhibited ⁺ Vacancy order and charge order, delay or inhibit phase change, and improve the rate capability and cycle stability of the electrode material.

The existence of the high-entropy oxide in the coating layer can react part of residual alkali, so that the conductivity is improved, and meanwhile, the coating has certain electrochemical activity, so that the capacity is not lost; the high-entropy oxide has good structural stability and ion conductivity, is beneficial to improving the stability of the anode material, reducing side reactions and improving the transmission capacity of sodium ions.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present disclosure and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person of ordinary skill in the art.

FIG. 1 is a flow chart of example 1;

FIG. 2 is an SEM of the dried material of example 1, step 3;

FIG. 3 is an SEM of the positive electrode substrate of example 1;

fig. 4 is a SEM of the high entropy oxide coated positive electrode substrate of example 1.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present disclosure more apparent, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Some embodiments of the present disclosure provide a high entropy oxide doped coated co-modified cathode material, including a substrate and a high entropy oxide, wherein a part of the high entropy oxide is coated on the surface of the substrate to form a coating layer, and a part of the high entropy oxide enters the surface layer of the substrate to form a doped layer;

The high entropy oxide in this embodiment is used as a single-phase solid solution material with multiple metal elements sharing the same atomic site and cations being disordered, and because of disordered metal layers, the metal elements tend to randomly generate oxidation-reduction reaction, so that Na can be inhibited ⁺ Vacancy order and charge order, delay or inhibit phase change, and improve the rate capability and cycle stability of the electrode material. In addition, the metal elements in the high-entropy oxide are five or more, wherein the doping amount of the elements except A, B, C, D, E is low, and a small amount of doping is more beneficial to inhibiting Na ⁺ Vacancy ordering and charge ordering.

In the embodiment, the existence of the high-entropy oxide in the coating layer can react part of residual alkali, so that the conductivity is improved, and meanwhile, the coating has certain electrochemical activity, so that the capacity is not lost; the high-entropy oxide has good structural stability and ion conductivity, is beneficial to improving the stability of the anode material, reducing side reactions and improving the transmission capacity of sodium ions.

In some alternative embodiments, m > 0.

In some alternative embodiments, the substrate is of the formula Na _x Ni _y Mn _z (T) _t O ₂ T is at least one of Cu, cr, fe, zn, ti and V, 0.8<x<Y is more than or equal to 1 and less than or equal to 0.5, z is more than or equal to 0 and less than or equal to 1.0, t is more than or equal to 0 and less than or equal to 0.2, and y+z+t=1.

In some alternative embodiments, T is Fe.

In some alternative embodiments, the high entropy oxide is a nanoscale high entropy oxide. The nano-scale high-entropy oxide is easier to partially enter the crystal surface layer of the base material in the high-temperature reaction, is beneficial to improving the content of the high-entropy oxide nanocrystals in the doped layer, is beneficial to uniformly coating the high-entropy oxide on the surface of the positive electrode material, and is beneficial to improving the stability of the positive electrode material in the charging and discharging process when the high-entropy oxide nanocrystals are doped to the bulk at high temperature.

In alternative embodiments.

In some alternative embodiments, the high entropy oxide has a particle size of less than 200nm.

In some optional embodiments, the mass fraction of the high-entropy oxide in the positive electrode material is less than 5%, in the preparation process of the positive electrode material, the mass fraction of the high-entropy oxide is calculated according to the addition amount of the metal salt and the base material, the content of the high-entropy oxide is low, the improvement on the multiplying power and the cycling stability of the material is limited, but the capacity of the material is affected by the excessive content.

In some alternative embodiments, the positive electrode material D50 is 5um to 10um.

In some alternative embodiments, further comprising the preparation of a substrate having a high entropy oxide attached to the surface: comprising heating a mixed solution of a substrate, a metal salt and a solvent to obtain a substrate having a high entropy oxide attached to the surface. The substrate with the high-entropy oxide attached to the surface is difficult to realize in-situ generation and uniform coating of the high-entropy oxide by a solid phase method, so that the efficiency and the cycle stability of a finally obtained product are improved undesirably.

In some alternative embodiments, in the preparation step of the substrate with the high-entropy oxide attached to the surface, the mass fraction of the substrate in the mixed solution is 25% -35%, and the mass fraction of the metal salt is 3.5% -4.5%. The concentration of the base material and the metal salt in the mixed solution is too low, which is not beneficial to the improvement of the reaction efficiency, and the too high concentration can influence the chemical balance and the stable reaction, thereby influencing the uniformity of the dispersion of the high-entropy oxide, and further increasing the particle size of the high-entropy oxide or reducing the uniformity of the particle size distribution of the high-entropy oxide.

In some alternative embodiments, in the preparation step of the substrate with the high-entropy oxide attached to the surface, the heating temperature is 60 ℃ to 150 ℃, the heat preservation time is 1h to 6h, and the extension of the heat preservation time and the too high or too low heating temperature may cause the change of the crystal size of the high-entropy oxide, so that the uniform doping and cladding of the high-entropy oxide are not favored.

In some alternative embodiments, the preparation step of the substrate with the high-entropy oxide attached to the surface is performed in a closed reactor, and the substrate may have a certain pressure under the condition of heating, which is beneficial to the formation of the high-entropy oxide nanocrystalline.

In some alternative embodiments, the preparation process of the substrate with the high-entropy oxide attached to the surface is accompanied by stirring, and the stirring can prevent the substrate from sinking, so that the substrate is favorably and uniformly dispersed in the mixed solution, and the uniformly dispersed nano high-entropy oxide is cooperated, so that the generated high-entropy oxide is uniformly coated.

In some alternative embodiments, the stirring speed is 100rpm-500rpm, and too slow stirring speed can not be used for uniformly dispersing the substrate and the nano high-entropy oxide in the mixed solution, and too fast stirring speed can influence the chemical equilibrium state of the solution, so that the combination of the high-entropy oxide and the substrate is influenced, and the uniform coating of the high-entropy oxide on the surface of the substrate is further unfavorable.

In some alternative embodiments, intermittent stirring is adopted for stirring, and long-time stirring also affects the chemical equilibrium state of the solution, so that the combination of the high-entropy oxide and the substrate is affected, and even coating of the high-entropy oxide on the surface of the substrate is not facilitated.

In some alternative embodiments, the substrate having the high entropy oxide attached to the surface is prepared by stirring for 50s to 70s each time, at intervals of 8min to 12 min.

In some alternative embodiments, in the preparation step of the substrate having the high-entropy oxide attached to the surface, the metal salt is 5 or more of Li salt, na salt, mg salt, ca salt, al salt, zn salt, sc salt, ti salt, V salt, cr salt, mn salt, fe salt, co salt, Y salt, zr salt, nb salt, mo salt, ga salt, te salt, sb salt, in salt, sn salt.

In some alternative embodiments, the metal salt is at least one of a nitrate salt, a chloride salt.

In some alternative embodiments, the solvent is ethanol, oleylamine, and hexane in a ratio of 1 (0.9-1.1): 2.5-3.5.

Wherein the ethanol is used as a solvent; hexane is used as a solvent and a dispersing agent, so that other solvents, a base material and generated high-entropy oxide nano particles are uniformly dispersed in the solvent; the oil ammonia is used as a stabilizer, so that the reaction can be slowed down, the chemical balance can be kept, the agglomeration of nano particles can be prevented, and the nano particles can be uniformly and slowly generated; wherein ethanol, oleylamine and hexane are mixed according to a proportion, so that nano-level high-entropy oxide which is uniformly dispersed in a solvent can be obtained.

In some alternative embodiments, the reaction solution is further subjected to solid-liquid separation after the heating is completed, and the separated solid phase is dried.

In some alternative embodiments, the drying temperature is 75-85 ℃ and the drying time is greater than 8 hours, in some embodiments rotary vacuum drying or atmospheric drying is used, but the negative pressure is advantageous for rapid removal of moisture in preparation for subsequent sintering.

In some alternative embodiments, the sintering step is performed at a sintering temperature of 800 ℃ to 1100 ℃ for a holding time of 4 hours to 15 hours.

In some alternative embodiments, the sintering step is performed at a temperature of 880 ℃ to 980 ℃ and for a holding time of 8 hours to 15 hours.

In some alternative embodiments, the sintering atmosphere is air or oxygen.

In some alternative embodiments, the method further comprises the step of preparing the substrate: comprising sintering a mixture of an oxide and a sodium source to obtain a substrate.

In some alternative embodiments, the oxide includes at least one of nickel oxide, manganese oxide, chromium oxide, iron oxide, vanadium oxide, and titanium oxide.

In some alternative embodiments, the sodium source is one or more of sodium carbonate, sodium hydroxide, sodium oxide, sodium peroxide.

In some alternative embodiments, the substrate is prepared at a sintering temperature of 800 ℃ to 1000 ℃ for a sintering time of 6 hours to 24 hours.

In some alternative embodiments, the substrate is prepared at a sintering temperature of 850 ℃ to 950 ℃ and a holding time of 8 hours to 15 hours.

The features and capabilities of the present disclosure are described in further detail below in connection with the examples.

Example 1:

the embodiment provides a method for doping, coating and co-modifying a sodium ion positive electrode material by using a high-entropy oxide, as shown in fig. 1, comprising the following steps:

step 1: mixing nickel oxide, manganese oxide, zinc oxide and sodium carbonate according to the molar ratio of Ni, mn, zn, na elements of 0.20:0.7:0.1:0.95, and marking as a mixture A;

step 2: sintering and preserving heat for 12 hours at 880 ℃ in air atmosphere to obtain a substrate B, wherein the appearance of the substrate B is shown in figure 3.

Step 3: adding copper nitrate trihydrate, zinc nitrate hexahydrate, ferric nitrate nonahydrate, cerium nitrate hexahydrate and zirconium chloride into a conical flat-bottomed beaker, wherein the molar ratio of copper, zinc, iron, cerium and zirconium is about 1:1:1:1, adding 30g of base material B, enabling the theoretical maximum mass fraction of high-entropy oxide in the positive electrode material to be 5%, adding 100ml of ethanol, oleylamine and hexane with the volume ratio of 1:1:3, placing the materials into a magnet, sealing the beaker, placing the materials on a ceramic heating table, reacting at 100 ℃ for 120min, stirring at 150rpm for 1min at intervals of 10min, filtering after the reaction, carrying out rotary vacuum drying on the solid phase, wherein the drying temperature is 80 ℃, and the rotating speed is 200rpm, thus obtaining the material C with the appearance shown in figure 2.

Step 4: and sintering and preserving heat of the material C for 10 hours at 900 ℃ in an air atmosphere to obtain the anode material with high entropy coating, wherein the morphology of the anode material is shown in figure 4.

Example 2:

the embodiment provides a method for doping, coating and co-modifying a sodium ion positive electrode material by using a high-entropy oxide, which comprises the following steps:

step 2: sintering and preserving heat for 12 hours at 880 ℃ in air atmosphere to obtain the base material B.

Step 3: adding copper nitrate trihydrate, zinc nitrate hexahydrate, cerium nitrate hexahydrate, zirconium chloride and nickel chloride hexahydrate into a conical flat-bottomed beaker, wherein the molar ratio of copper, zinc, cerium, zirconium and nickel elements is about 1:1:1:1, adding 30g of base material B, enabling the theoretical maximum mass fraction of high-entropy oxide in the positive electrode material to be 5%, adding 100ml of ethanol, oleylamine and hexane with the volume ratio of 1:1:3, placing the mixture into a magnet, sealing the beaker, placing the beaker on a ceramic heating table, reacting at 100 ℃ for 120min, stirring at 150rpm for 1min at intervals of 10min, filtering after the reaction, and carrying out rotary vacuum drying on the solid phase at the drying temperature of 80 ℃ and the rotating speed of 200rpm to obtain a material C.

Step 4: and sintering and preserving heat of the material C for 10 hours at 900 ℃ in an air atmosphere to obtain the anode material with high entropy coating.

Example 3:

the difference between the method for doping and coating the co-modified sodium ion positive electrode material with the high entropy oxide and the method for coating the co-modified sodium ion positive electrode material with the high entropy oxide is that in the step 3, ethanol, oleylamine and hexane with the volume ratio of 1:0.9:2.5 are added.

Example 4:

the difference between the method for doping and coating the co-modified sodium ion positive electrode material with the high entropy oxide and the method for coating the co-modified sodium ion positive electrode material with the high entropy oxide is that in the step 3, ethanol, oleylamine and hexane with the volume ratio of 1:1.1:3.5 are added.

Example 5:

this example provides a method for doping coated co-modified sodium ion positive electrode material with high entropy oxide, which differs from example 1 only in that in step 3, stirring is continued at a speed of 150 rpm.

Example 6:

the present example provides a method for doping and coating a co-modified sodium ion cathode material with a high entropy oxide, which is different from example 1 only in that in step 3, the stirring speed is 500rpm during stirring.

Example 7:

the present example provides a method for doping and coating a co-modified sodium ion positive electrode material with a high entropy oxide, which is different from example 1 only in that in step 3, the stirring speed is 100rpm during stirring.

Example 8:

the present embodiment provides a method for doping, coating and co-modifying a sodium ion positive electrode material with a high entropy oxide, which is different from embodiment 1 only in that in step 3, stirring time is 50s, and stirring is performed once at intervals of 12 min.

Example 9:

the present embodiment provides a method for doping, coating and co-modifying a sodium ion positive electrode material with a high entropy oxide, which is different from embodiment 1 only in that in step 3, stirring time is 70s, and stirring is performed once at intervals of 8 min.

Example 10:

the present embodiment provides a method for doping, coating and co-modifying a sodium ion positive electrode material with a high entropy oxide, which is different from embodiment 1 only in that in step 3, a beaker is sealed, and the beaker is placed on a ceramic heating table to react for 120min at 60 ℃.

Example 11:

the present embodiment provides a method for doping, coating and co-modifying a sodium ion positive electrode material with a high entropy oxide, which is different from embodiment 1 only in that in step 3, a beaker is sealed, and the beaker is placed on a ceramic heating table to react for 120min at 150 ℃.

Example 12:

the present example provides a method for doping and coating co-modified sodium ion positive electrode material with high entropy oxide, which is different from example 1 only in that in step 3, the beaker is sealed and placed on a ceramic heating table to react for 6 hours at 100 ℃.

Example 13:

the present embodiment provides a method for doping, coating and co-modifying a sodium ion positive electrode material with a high entropy oxide, which is different from embodiment 1 only in that in step 3, copper nitrate, zinc nitrate, ferric nitrate, cerium nitrate, zirconium chloride and nickel chloride are added into a conical flat bottom beaker according to an element molar ratio of 1:1:1:1:1 (the molar total amount of metal elements is equal to that in embodiment 1).

Example 14:

the present embodiment provides a method for doping, coating and co-modifying a sodium ion positive electrode material with a high entropy oxide, which is different from embodiment 1 only in that in step 3, copper nitrate, zinc nitrate, ferric nitrate, cerium nitrate, zirconium chloride and nickel chloride are added into a conical flat-bottom beaker according to an element molar ratio of 1:1:1:1:0.015 (the molar total amount of metal elements is equal to that in embodiment 1).

Example 15:

the present example provides a method for doping and coating co-modified sodium ion positive electrode material with high entropy oxide, which is different from example 1 only in that in step 3, the beaker is sealed and placed on a ceramic heating table to react for 1h at 100 ℃.

Example 16:

the present embodiment provides a method for doping and coating a co-modified sodium ion positive electrode material with a high entropy oxide, which is different from embodiment 1 only in that in step 4, the sintering temperature is 1100 ℃.

Example 17:

the present embodiment provides a method for doping and coating a co-modified sodium ion positive electrode material with a high entropy oxide, which is different from embodiment 1 only in that in step 4, the sintering temperature is 800 ℃.

Example 18:

the present embodiment provides a method for doping, coating and co-modifying a sodium ion positive electrode material with a high entropy oxide, which is different from embodiment 1 only in that in step 3, copper nitrate, zinc nitrate, ferric nitrate, cerium nitrate and zirconium chloride are added into a conical flat-bottomed beaker according to an element molar ratio of 0.25:0.25:0.25:0.15:0.15 (the molar total amount of metal elements is equal to that in embodiment 1).

Example 19:

the present embodiment provides a method for doping, coating and co-modifying a sodium ion positive electrode material with a high entropy oxide, which is different from embodiment 1 only in that in step 3, copper nitrate, zinc nitrate, ferric nitrate, cerium nitrate and zirconium chloride are added into a conical flat-bottomed beaker according to an element molar ratio of 0.15:0.15:0.25:0.25:0.25 (the molar total amount of metal elements is equal to that in embodiment 1).

Example 20:

the embodiment provides a high entropy oxide doped cladding co-repairThe method for decorating the sodium ion positive electrode material is different from example 1 only in that in step 1, the composition of the mixture A is adjusted so that Na is obtained in step 2 respectively _0.9 Ni _0.2 Mn _0.6 Fe _0.2 O ₂ 、Na _0.73 Ni _0.6 Co _0.05 Mn _0.35 O ₂ The method comprises the steps of carrying out a first treatment on the surface of the Or, in step 3, cu is obtained _0.125 Zn _0.125 Fe _0.125 Ce _0.125 Zr _0.125 Ni _0.125 Co _0.125 Cr _0.125 O ₂ 、Mg _0.2 Al _0.2 Ni _0.2 Zn _0.2 Ti _0.2 O ₂ Compared with the base material, the 1C/0.1C of the coated high-entropy oxide has a certain improvement, and the capacity retention rate of the 1C circulation for 100 circles is increased by more than 5%.

Comparative example 1:

the comparative example provides a method for doping, coating and co-modifying a sodium ion positive electrode material by using high-entropy oxide, which comprises the following steps:

Step 3: adding 2.02g of zinc nitrate hexahydrate and 1.58g of zirconium chloride into a conical flat-bottomed beaker, adding 30g of base material B to enable the theoretical maximum mass fraction of high-entropy oxide in the positive electrode material to be 5%, adding 100ml of ethanol, oleylamine and hexane with volume ratio of 1:1:3, putting the mixture into a magnet, sealing the beaker, placing the beaker on a ceramic heating table to react for 120min at 100 ℃, stirring at 150rpm for 1min at intervals of 10min, filtering and drying after the reaction is finished, and obtaining a material C.

Comparative example 2:

the method for doping, coating and co-modifying the sodium ion positive electrode material by using the high-entropy oxide comprises the following steps of:

Step 3: uniformly mixing the materials B by using a mixer, sintering and preserving heat for 10 hours at 900 ℃ in an air atmosphere to obtain Na _0.95 Ni _0.2 Zn _0.1 Mn _0.7 O ₂ And a positive electrode material.

Comparative example 3:

Step 3: adding 30g of a base material B into a conical flat-bottomed beaker, adding the base material B, adding 100ml of ethanol, oleylamine and hexane in a volume ratio of 1:1:3, sealing the beaker, placing the beaker on a heating table to react at 100 ℃ for 120min, and filtering and drying after the reaction is finished to obtain a material C.

Step 4: and sintering and preserving heat of the material C for 10 hours at 900 ℃ in an air atmosphere to obtain the non-coated anode material.

Comparative example 4:

this comparative example provides a method for doping and coating co-modified sodium ion cathode material with high entropy oxide, which is different from example 1 only in that cerium nitrate, zirconium chloride and nickel chloride are added into a conical flat bottom beaker according to an element molar ratio of 1:1:1 (the molar total amount of metal elements is equal to that of example 1) in step 3.

Comparative example 5:

this comparative example provides a method for doping and coating co-modified sodium ion cathode material with high entropy oxide, which is different from example 1 only in that in step 3, copper nitrate, zinc nitrate, ferric nitrate, cerium nitrate are added into a conical flat bottom beaker according to an element molar ratio of 1:1:1:1 (the molar total amount of metal elements is equal to that of example 1).

Comparative example 6:

the comparative example provides a method for doping and coating a co-modified sodium ion positive electrode material with high entropy oxide, which is different from example 1 only in that ethanol, oleylamine and hexane are added in a volume ratio of 1:0.5:4 in step 3.

Comparative example 7:

the comparative example provides a method for doping and coating a co-modified sodium ion positive electrode material with high entropy oxide, which is different from the method in the embodiment 1 only in that in the step 3, ethanol, oleylamine and hexane with the volume ratio of 1:1.5:2 are added.

Comparative example 8:

this comparative example provides a method for doping and coating a co-modified sodium ion cathode material with a high entropy oxide, which is different from comparative example 1 only in that in step 3, the stirring speed is 1000rpm at the time of stirring.

Comparative example 9:

this comparative example provides a method for doping and coating co-modified sodium ion positive electrode material with high entropy oxide, which is different from comparative example 1 only in that in step 3, the beaker is sealed and placed on a ceramic heating table to react for 10 hours at 100 ℃.

Comparative example 10:

this comparative example provides a method for doping and coating co-modified sodium ion positive electrode material with high entropy oxide, which is different from comparative example 1 only in that in step 3, the beaker is sealed and placed on a ceramic heating table to react for 120min at 30 ℃.

Comparative example 11:

this comparative example provides a method for doping and coating co-modified sodium ion positive electrode material with high entropy oxide, which is different from comparative example 1 only in that in step 3, the beaker is sealed and placed on a ceramic heating table to react for 120min at 180 ℃.

Comparative example 12:

this comparative example provides a method for doping and coating co-modified sodium ion positive electrode material with high entropy oxide, which is different from example 1 only in that in step 3, stirring time is 30s and stirring is performed once at 15min intervals.

Comparative example 13:

this comparative example provides a method for doping and coating co-modified sodium ion positive electrode material with high entropy oxide, which is different from example 1 only in that in step 3, stirring time is 90s and stirring is performed once at intervals of 5 min.

The positive electrode materials obtained in the above examples and comparative examples were prepared into button cells, specifically comprising: (1) preparing slurry, weighing materials, mixing with a conductive agent and a binder, wherein the materials are as follows: conductive agent: the mass ratio of the binder is 8:1:1, the binder is PVDF, and the conductive agent is conductive carbon; (2) coating, namely coating the aluminum foil by using a scraper; (3) drying, namely drying the coated pole piece in a vacuum drying oven at the drying temperature of 120 ℃ for 4 hours; (4) tabletting, namely tabletting the dried pole piece by using a pair roller; (5) and assembling battery parts such as a positive pole piece, a negative pole piece, a diaphragm, electrolyte and the like into the button battery. The electrical properties of the cells were then tested at a voltage of 1.5-4.2V and a temperature of 25 ℃ to give table 1.

Table 1 electrical properties of the batteries using examples and comparative examples to obtain positive electrode materials

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Table 1 shows the electrical properties of the batteries of the examples and the comparative examples, and it can be seen from examples 1-2 and comparative example 2 that the high entropy oxide modified sodium ion cathode material has beneficial effects, especially for improving the rate performance and the cycle performance; from example 1 and comparative examples 1-2, the effect of the high entropy material on the performance improvement is more pronounced compared to the direct coating oxide, probably due to the more stable structure of the high entropy oxide and the better ionic conductivity; as can be seen from examples 1-2 and comparative example 3, the stirring process also has a great influence on the properties of the materials, and it can be seen from the comparison of other examples and comparative examples that the stirring rate, the stirring frequency and the stirring time each time have a great influence on the product, because the stirring process causes the positive electrode material to be dispersed in the solvent too, and the coating is more uniform in cooperation with the dispersed high-entropy material.

Industrial applicability

The substrate is coated and doped by the high-entropy oxide, part of residual alkali can be reacted by the high-entropy oxide, the conductivity is improved, and meanwhile, the coating also has certain electrochemical activity, so that capacity is not lost; the high-entropy oxide has good structural stability and ion conductivity, is beneficial to improving the stability of the positive electrode material and reducing side reactions, and simultaneously improves the transmission capacity of sodium ions, thereby improving the multiplying power and the cycle performance of the positive electrode material.

Claims

1. The high-entropy oxide doped coating co-modified cathode material is characterized by comprising a substrate and a high-entropy oxide, wherein part of the high-entropy oxide is coated on the surface of the substrate to form a coating layer, and part of the high-entropy oxide enters the surface layer of the substrate to form a doped layer;

the base material is O3 type layered transition metal oxide, and the structural formula of the high entropy oxide is A _a B _b C _c D _d E _e (M) _m O ₂ Of which 0.15<a<0.25，0.15<b<0.25，0.15<c<0.25，0.15<d<0.25，0.15<e<0.25，m<0.1, a+b+c+d+e+m=1, said A, B, C, D, E being selected from five of Li, na, mg, ca, al, zn, sc, ti, V, cr, mn, fe, co, Y, zr, nb, mo, ga, te, sb, in, ce and Sn, said M being selected from at least one of Li, na, mg, ca, al, zn, sc, ti, V, cr, mn, fe, co, Y, zr, nb, mo, ga, te, sb, in, ce and Sn.

2. The high entropy oxide doped coated co-modified positive electrode material according to claim 1, wherein the substrate has a structural formula of Na _x Ni _y Mn _z (T) _t O ₂ T is at least one of Cu, cr, fe, zn, ti and V, 0.8<x<Y is more than or equal to 1 and less than or equal to 0.5, z is more than or equal to 0 and less than or equal to 1.0, t is more than or equal to 0 and less than or equal to 0.2, and y+z+t=1.

3. The high entropy oxide doped coated co-modified cathode material according to claim 1 or 2, wherein T is Fe.

4. The high entropy oxide doped coated co-modified cathode material according to any one of claims 1 to 3, wherein the high entropy oxide is a nanoscale high entropy oxide.

5. The high entropy oxide doped coated co-modified cathode material according to any one of claims 1 to 4, wherein the high entropy oxide has a particle size of less than 200nm.

6. The high entropy oxide doped coated co-modified positive electrode material according to any one of claims 1 to 5, wherein the mass fraction of high entropy oxide in the positive electrode material is less than 5%.

7. The high entropy oxide doped coated co-modified positive electrode material according to any one of claims 1 to 6, wherein the positive electrode material D50 is 5um to 10um.

8. A method for preparing the high-entropy oxide doped coated co-modified cathode material according to any one of claims 1 to 7, comprising: sintering the base material with the high-entropy oxide attached to the surface to obtain the high-entropy oxide doped coating co-modified anode material.

9. The method for preparing a high entropy oxide doped coated co-modified cathode material according to claim 8, further comprising preparing a substrate having a high entropy oxide attached to a surface thereof: comprising heating a mixed solution of a substrate, a metal salt and a solvent to obtain a substrate having a high entropy oxide attached to the surface.

10. The method for preparing a high-entropy oxide doped coated co-modified cathode material according to claim 9, wherein in the step of preparing the substrate with the high-entropy oxide attached to the surface, the mass fraction of the substrate in the mixed solution is 25% -35%, and the mass fraction of the metal salt is 3.5% -4.5%.

11. The method for preparing a high-entropy oxide doped coated co-modified cathode material according to claim 9 or 10, wherein in the preparation step of the substrate with the high-entropy oxide attached to the surface, the heating temperature is 60 ℃ to 150 ℃ and the heat preservation time is 1h to 6h.

12. The method for producing a high entropy oxide doped coated co-modified cathode material according to any one of claims 9 to 11, wherein the step of producing the substrate having the high entropy oxide attached to the surface is performed in a closed reactor.

13. The method for producing a high-entropy oxide doped coated co-modified positive electrode material according to any one of claims 9 to 12, wherein the process for producing the substrate having the high-entropy oxide attached to the surface is accompanied by stirring.

14. The method for preparing a high entropy oxide doped coated co-modified cathode material according to claim 13, wherein the stirring speed is 100rpm to 500rpm.

15. The method for preparing a high entropy oxide doped coated co-modified cathode material according to claim 13 or 14, wherein the stirring is intermittent stirring.

16. The method for preparing a co-modified cathode material with doped and coated high-entropy oxide according to claim 15, wherein in the step of preparing the substrate with the high-entropy oxide attached to the surface, stirring is performed for 50s-70s each time, and stirring is performed for 8min-12min each time.

17. The method for producing a Co-modified cathode material according to any one of claims 9 to 16, wherein In the step of producing a substrate having a high entropy oxide attached to the surface, the metal salt is 5 or more of Li salt, na salt, mg salt, ca salt, al salt, zn salt, sc salt, ti salt, V salt, cr salt, mn salt, fe salt, co salt, Y salt, zr salt, nb salt, mo salt, ga salt, te salt, sb salt, in salt, and Sn salt.

18. The method for preparing a high-entropy oxide doped coated co-modified cathode material according to any one of claims 9 to 17, wherein the metal salt is at least one of nitrate and chloride.

19. The method for preparing a high entropy oxide doped coated co-modified cathode material according to any one of claims 9 to 18, wherein the solvent is ethanol, oleylamine and hexane in a ratio of 1 (0.9 to 1.1): 2.5 to 3.5.

20. The method for producing a co-modified cathode material according to any one of claims 9 to 19, wherein the reaction solution is subjected to solid-liquid separation after the completion of heating, and the separated solid phase is dried.

21. The method for preparing a high entropy oxide doped coated co-modified cathode material according to claim 20, wherein the drying temperature is 75-85 ℃ and the drying time is more than 8h.

22. The method for preparing a high entropy oxide doped coated co-modified cathode material according to any one of claims 8 to 21, wherein the sintering step is performed at a sintering temperature of 800 ℃ to 1100 ℃ and a heat preservation time of 4h to 15h.

23. The method for preparing a high entropy oxide doped coated co-modified cathode material according to claim 22, wherein the sintering step is performed at a temperature of 880-980 ℃ and the heat preservation time is 8-15 h.

24. The method for preparing a high entropy oxide doped coated co-modified cathode material according to any one of claims 8 to 22, wherein the sintering atmosphere is air or oxygen.

25. The method for preparing a high entropy oxide doped coated co-modified cathode material according to any one of claims 8 to 24, further comprising the step of preparing a substrate: comprising sintering a mixture of an oxide and a sodium source to obtain a substrate.

26. The method for preparing a high entropy oxide doped coated co-modified cathode material according to claim 25, wherein the oxide comprises at least one of nickel oxide, manganese oxide, chromium oxide, iron oxide, vanadium oxide, and titanium oxide.

27. The method for preparing a co-modified cathode material with high entropy oxide doping coating according to claim 25 or 26, wherein the sodium source is one or more of sodium carbonate, sodium hydroxide, sodium oxide and sodium peroxide.

28. The method for preparing a co-modified cathode material with high entropy oxide doping coating according to any one of claims 25 to 27, wherein in the step of preparing the base material, the sintering temperature is 800 ℃ to 1000 ℃ and the sintering time is 6h to 24h.

29. The method for preparing a co-modified cathode material with high entropy oxide doping coating as set forth in any one of claims 25 to 28, wherein in the step of preparing the base material, the sintering temperature is 850 ℃ to 950 ℃ and the heat preservation time is 8h to 15h.

30. Use of a positive electrode material according to any one of claims 1 to 7 or a positive electrode material obtainable by a method according to any one of claims 8 to 29 in a sodium ion battery.

31. An electrode comprising the positive electrode material of any one of claims 1 to 7 or the positive electrode material obtained by the method of any one of claims 8 to 29.

32. A sodium ion battery comprising the electrode of claim 31.

33. A powered device comprising the sodium ion battery of claim 32.