CN114927658A - Device and method for modifying surface of anode material based on ion exchange membrane - Google Patents

Abstract

The invention relates to a device and a method for modifying the surface of a positive electrode material based on an ion exchange membrane. The device for modifying the surface of the positive electrode material based on the ion exchange membrane comprises: a cation chamber containing a cation solution therein; an anion chamber containing an anion solution therein; an ion exchange membrane for physical separation of an anion chamber and a cation chamber, the ion exchange membrane comprising a cation exchange membrane and an anion exchange membrane; and the stirring system is respectively arranged at the bottom of the cation chamber and the bottom of the anion chamber or/and the flowing system is respectively communicated and connected with the cation chamber and the anion chamber.

Description

A device for surface modification of positive electrode material based on ion exchange membrane and method for surface modification of positive electrode material

technical field

The invention relates to the surface modification of lithium ion electrode materials, in particular to a device for surface modification of lithium ion positive electrode materials and a method for surface modification of positive electrode materials, and belongs to the field of chemical energy storage batteries.

Background technique

The rapid development of new energy vehicles has put forward higher requirements for the specific capacity and safety of cathode materials used in power batteries. Among the current commercial spinel-type, olivine-type and layered-type cathode materials, ternary layered cathode materials have received extensive attention due to their excellent specific capacity, although the increase of nickel content can improve the specific capacity and However, with the increase of nickel content, the cycle performance, thermal stability and safety of ternary cathode materials will deteriorate sharply, which seriously restricts its practical application. The root cause of the above problems stems from the material properties of the high-nickel ternary cathode, including the dissolution of metal elements and the side reaction of Ni ⁴⁺ , which has strong oxidizing properties in the charged state, with the electrolyte and surface reconstruction, resulting in high impedance. NiO phase and release reactive oxygen species, resulting in gas production and thermal runaway of the battery. At present, scholars at home and abroad mainly solve the above shortcomings by coating the surface of ternary materials, inhibiting the dissolution of transition metals and isolating the direct contact of highly active Ni ⁴⁺ with the electrolyte.

At present, the surface coating methods of cathode materials mainly include co-precipitation method, sol-gel method, hydrothermal method, chemical vapor deposition method, atomic deposition method, solid-phase ball milling method, etc., but there are still high cost and poor coating. uniformity, etc. Sol-gel method and hydrothermal method have expensive precursor salts and low yield; chemical vapor deposition method and atomic deposition method have long processing time, strong toxicity and complicated process, and solid-phase ball milling method is difficult to obtain uniform coating layer. The key to uniform coating lies in the regulation of the coating layer. The key point of the regulation of the coating layer is the slow deposition of the coating material on the surface of the coated material, and the formation of separate two phases is avoided through diffusion control. At present, the uniform control strategies of the coating layer mainly include buffer solution, slow release of precipitation, catalyst assistance, and charge interaction. The above strategy can effectively realize the precise regulation of the coating layer, and can significantly improve the performance of the cathode material, but there are also problems such as low universality and complicated operation. Therefore, it is of great significance to develop a method that is easy to operate and uniformly coats the cathode material.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention provides an ion exchange membrane-based device for modifying the surface of a positive electrode material and a method for modifying the surface of the positive electrode material.

In a first aspect, the present invention provides a device for surface modification of a positive electrode material based on an ion exchange membrane, comprising:

a cation chamber containing a cation solution;

an anion chamber, the anion chamber contains an anion solution;

An ion-exchange membrane for physically separating an anion compartment and a cation compartment, the ion-exchange membrane including a cation-exchange membrane and an anion-exchange membrane;

and a stirring system or/and a flow system respectively connected to the cation chamber and the anion chamber respectively arranged at the bottom of the cation chamber and the anion chamber.

In the present invention, based on the ion exchange effect of the ion exchange membrane, the surface modification of the lithium ion positive electrode material is carried out to improve its electrochemical performance and safety, reduce the modification cost, and improve the coating uniformity. The method has the advantages of convenient operation, uniform coating and easy to enlarge production.

Preferably, the flow system includes:

The cationic solution storage tank, the flow pump and the flow pipeline connecting the cationic chamber and the cationic solution storage tank;

The anion solution storage tank is connected with the flow pump and the flow pipeline of the anion chamber and the anion solution storage tank.

Preferably, both the cation chamber and the anion chamber are provided with stirring devices, wherein the stirring devices include at least one of magnetic stirring devices, mechanical stirring devices, ultrasonic stirring devices and other stirring devices.

Preferably, the active group in the cation exchange membrane includes at least one of a sulfonic acid group, a phosphoric acid group, a carboxylic acid group, a phenolic group, an arsenic acid group and a selenic acid group; the active group in the anion exchange membrane includes a At least one of the amino group and the arylamino group of the primary, secondary, tertiary and quaternary amines.

Preferably, the positive electrode material includes a lithiated positive electrode material and a positive electrode precursor material;

The cathode material after lithiation includes LiNi _b Co _{c Mn 1-bc} O ₂ (wherein 0≤b≤1, 0≤c≤1); and LiNi _m Con Al _1-mn O ₂ (0≤m≤1) , 0≤n≤1);

The positive electrode precursor material includes Ni _(1-yz) Co _y Mn _z (OH) ₂ (wherein 0≤y≤1, 0≤z≤1) and Ni _(1-ad) Co _a Al _d (OH) ₂ (where 0≤a≤1, 0≤d≤1).

Preferably, the solute in the cation solution is selected from Al(NO ₃ ) ₃ , Al ₂ (SO ₄ ) ₃ , AlCl ₃ , MnCl ₃ , Co(NO ₃ ) ₃ , Co ₂ (SO ₄ ) ₃ , Fe( NO ₃ ) ₃ , Fe ₂ (SO ₄ ) ₃ , FeCl ₃ , Cr(NO ₃ ) ₃ , Cr ₂ (SO ₄ ) ₃ , CrCl ₃ , Zr(NO ₃ ) ₄ , ZrCl ₄ , Zn(NO ₃ ) ₃ , at least one of TiBr ₄ .

Preferably, the solvent in the cationic solution includes at least one of distilled water, methanol, ethanol, isopropanol, n-butanol, isobutanol, cycloethanol, acetone, cyclohexanone, glycerol and ethyl acetate.

Preferably, the concentration of the cationic solution is 0.01 mol/L to 10 mol/L.

Preferably, the solute in the anion solution is selected from KOH, NaOH, LiOH, (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , H ₃ PO ₄ , NH ₃ ·H ₂ O, LiF, KF in NaF at least one of.

Preferably, the solvent in the anion solution includes at least one of distilled water, methanol, ethanol, isopropanol, n-butanol, isobutanol, cycloethanol, acetone, cyclohexanone, glycerol and ethyl acetate. The concentration of the anion solution is 0.01 mol/L to 10 mol/L.

Preferably, the device for surface modification of the positive electrode material based on the ion exchange membrane further comprises an external power supply connected to the cation chamber and the anion chamber.

In a second aspect, the present invention provides a method for surface modification of a positive electrode material, comprising:

(1) Disperse the positive electrode material in the cation solution or anion solution in the above-mentioned device for surface modification of the positive electrode material based on an ion exchange membrane, and combine the anion solution with the cation solution through a stirring system or a flow system to cause a precipitation reaction or a redox reaction Precipitation is formed to form a coating material on the surface of the positive electrode material or at the particle pores of the positive electrode material, and then after separation and drying, a positive electrode material with the coating material distributed on the surface is obtained;

(4) heat-treating the positive electrode material on which the coating substance is distributed on the surface to obtain a surface-modified positive electrode material.

In the present invention, with a unique device structure, an ion exchange membrane is used to isolate the anions and cations of the coating or filling material without external power supply, so that the anions and the cations are slowly combined to cause a precipitation reaction or a redox reaction to generate a precipitate, thereby obtaining coating substance. Of course, an external power supply can also be used, that is, the charge ions migrate faster under the concentration diffusion and electric field. Since the process of generating precipitation is controlled by the diffusion rate of ions in the ion exchange membrane, the supersaturation of the coating material in the mixed liquid system of the positive electrode material is always kept at a low level, which inhibits the process of the coating material and the positive electrode material forming separated particles , to promote its heterogeneous nucleation and growth on the surface of the positive electrode material, and realize its uniform coating or filling on the surface of the positive electrode material particle under the action of stirring. The surface coating of the positive electrode material, primary particle grain boundary filling, surface element doping and other multiple surface modifications are achieved through subsequent heat treatment to improve the stability of the positive electrode material.

Preferably, when the ion exchange membrane is a cation exchange membrane, the positive electrode material is dispersed in the anion chamber; when the ion exchange membrane is an anion exchange membrane, the positive electrode material is dispersed in the cation chamber; the particle size of the positive electrode material is 1- 100μm.

Preferably, a mixed solution is obtained by mixing a cation solution or an anion solution and a positive electrode material; the solid content of the positive electrode material in the mixed solution is 2wt%-20wt%.

Preferably, the temperature of the precipitation reaction or the redox reaction is 20-100°C, and the time is 0.5-36 hours.

Preferably, the coating material in the positive electrode material with the coating material distributed on the surface includes Mn(OH) ₂ , Co(OH) ₂ , AlPO ₄ , Mn ₃ (PO ₄ ) ₂ , FePO ₄ , Li ₃ PO ₄ One or more of , AlF ₃ , LiAlO ₂ , Li ₂ ZrO ₃ , Li ₄ Ti ₅ O1 ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ , ZnO, Al(OH) ₃ and Zr(OH) ₄ ; The mass of the coating material is 0.1% to 10% of the mass of the positive electrode material (before modification). Wherein, the drying is natural drying, drying and vacuum drying, the drying temperature is 20-150°C, and the drying time is 24-48h.

Preferably, when the positive electrode material is a lithiated positive electrode material, the heat treatment temperature is 600-800° C., the heat treatment time is 2-10 h, and the heat treatment atmosphere is pure oxygen or air. Alternatively, when the positive electrode material is a positive electrode precursor material, the obtained positive electrode material with a coating substance distributed on the surface and a lithium oxide are mixed and sintered to obtain a surface-modified positive electrode material; the lithium-containing oxide includes LiOH·H ₂ O , at least one of LiNO ₃ , Li ₂ CO ₃ , Li ₂ O and Li ₂ O ₂ , the molar ratio of the cathode material with the coating material distributed on the surface and the lithium-containing oxide is 1: (1.01-1.10) .

Preferably, the sintering treatment includes: one-step sintering or two-step sintering; the atmosphere of the sintering treatment is pure oxygen or air

Wherein, the one-step sintering includes: the sintering temperature is 600-850°C, the holding time is 10h-20h, and the heating rate of the one-step sintering is preferably 2-5°C/min;

The two-step sintering includes: the sintering temperature in the first step is 300-500°C, and the holding time is 2h-4h; the sintering temperature in the second step is 700-850°C, and the holding time is 10h-20h; preferably, the heating rate of the two-step sintering is It is 2～5℃/min.

In a third aspect, the present invention provides a surface-modified positive electrode material prepared according to the above-mentioned surface modification method.

In a fourth aspect, the present invention provides a lithium ion battery, comprising: a negative electrode material, the above-mentioned surface-modified positive electrode material, and a separator or a solid electrolyte separating the surface-modified positive electrode material and the negative electrode material; preferably, the separator comprises Polypropylene separator (PP), celgard separator, the solid electrolyte includes garnet type solid electrolyte, NASICON type solid electrolyte, sulfide solid electrolyte, perovskite type solid electrolyte; preferably, the negative electrode material is graphite, silicon carbon , silicon dioxide, silicon alloys, tin oxide, metallic lithium or lithium alloys.

Beneficial effects:

The invention uses an ion exchange membrane to selectively diffuse anions or cations, so that the anions and the cations are slowly combined to cause a precipitation reaction or a redox reaction to generate a precipitation, thereby obtaining a coating substance. The device and method keep the supersaturation of the coating material in the positive electrode material mixed liquid system at a low level, suppress the process of the coating material forming particles separated from the precursor material due to homogeneous nucleation and growth, and promote the The heterogeneous nucleation and growth of the coating material on the surface of the precursor material, so as to achieve uniform coating of the surface of the positive electrode material under the action of the solid-liquid phase shear force provided by the stirring action;

The present invention performs in-situ reaction on the surface of the precursor to achieve uniform coating, and can realize the surface coating of the positive electrode material through the heat treatment step, primary particle grain boundary filling, surface element doping and other multiple surface modifications, so that under various synergistic effects Further improve the stability of active materials;

The basic driving force of the coating of the present invention comes from ion diffusion, no additional energy supply is required, and the principle is simple, the required medicines and solvents are cheap and easy to obtain, and the environment is friendly. Therefore, the invention has strong versatility, convenient operation, environmental protection and high industrial application value.

Description of drawings

Fig. 1 is a device for surface modification of positive electrode material in the present invention, in the figure: 1- cation chamber, 2- anion chamber, 3- ion exchange membrane, 4- stirrer;

FIG. 2 is an X-ray diffraction (XRD) pattern of a positive electrode material, the positive electrode material including surface-modified Example 1 and non-surface-modified Comparative Example 1;

Fig. 3 is the dQ/dV curve of positive electrode material under different cycle number, and described material includes Example 1 (B) with surface modification and Comparative Example 1 (A) without surface modification;

FIG. 4A and FIG. 4B are comparative graphs of the cycle stability of Examples 1-3 with surface modification and Comparative Example 1 without surface modification;

Figure 5 is a rate performance comparison diagram of Example 1 with surface modification and Comparative Example 1 without surface modification;

6 is a scanning electron micrograph (SEM) of the cross-section of the positive electrode particles before and after the cycle of the positive electrode material, including the surface-modified Example 1 and the non-surface-modified Comparative Example 1 (the scales are all 5 μm). ).

Detailed ways

The present invention is further described below through the following embodiments, and it should be understood that the following embodiments are only used to illustrate the present invention, but not to limit the present invention.

In the present disclosure, the device for surface modification of positive electrode material based on ion exchange membrane: including a cation compartment and an anion compartment, and a cation exchange membrane separating the anion compartment and the cation compartment; wherein both the cation compartment and the anion compartment are equipped with stirring devices . When the device of the present invention is used, the positive electrode material mixture and the cationic substance solution are prepared first, and then the positive electrode material mixture and the cationic substance solution are injected into the anion chamber and the cation chamber respectively, and the stirring is always turned on during coating.

In the present invention, the anion substance solution and the cation substance solution are provided, the anions and cations constituting the coating substance are placed in the anion chamber and the cation chamber respectively, and the positive electrode material is optionally placed in the anion chamber or the cation chamber to obtain a positive electrode material mixed solution . The ion exchange membrane is used to isolate the anions and cations of the coating material, and the diffusion of anions or cations is controlled, so that the anions and cations are slowly combined, and a precipitation reaction or redox reaction occurs to form a precipitation, so as to obtain the coating material on the surface of the positive electrode material or at the pores of the particles. . The obtained modified positive electrode material is separated, dried and heat treated to obtain a surface modified positive electrode material. The surface modification method of the positive electrode material using the device will be described in detail below.

Prepare an anion solution. A soluble substance that can provide the anion of the coating substance is dissolved in a solvent to obtain an anion solution. Optionally, the positive electrode material is dispersed in an anion solution to obtain a positive electrode material mixed solution. More preferably, the positive electrode material mixture is injected into the anion chamber, and the cation solution is injected into the cation chamber. Then, the positive electrode material is coated, and after the coating is completed, the mixed solution of the anion chamber is centrifuged and dried to obtain the coated positive electrode material. During the coating process, the anion and cation compartments were always agitated. The centrifugal speed can be 3000～8000rpm, and the centrifugation time can be 3～5min. Drying or vacuum drying, drying temperature is 20 ~ 150 ℃, drying time is 24 ~ 48h.

Prepare a cationic solution. Dissolve the soluble substance that can provide the cation of the coating substance in the solvent, the anion solution. Optionally, the positive electrode material is dispersed in the cationic solution to obtain a positive electrode material mixed solution. More preferably, the positive electrode material mixture is injected into the cation chamber, and the anion solution is injected into the anion chamber. Then yes. The positive electrode material is coated, and after the coating is completed, the mixed solution of the anion chamber is centrifuged and dried to obtain the coated positive electrode material. During the coating process, the anion and cation compartments were always agitated. The centrifugal speed can be 3000～8000rpm, and the centrifugation time can be 3～5min. Drying or vacuum drying, drying temperature is 20 ~ 150 ℃, drying time is 24 ~ 48h.

When the coated material is the positive electrode material after lithiation, the obtained coated positive electrode material is subjected to heat treatment. After the heat treatment process, the positive electrode material recovers the electrochemical activity, and the coating material coated on the surface of the positive electrode material will be heat treated to realize the positive electrode material. surface coating and/or element doping.

When the coated material is a positive electrode precursor material, the obtained coated positive electrode precursor material is mixed with a lithium-containing compound such as LiOH·H ₂ O according to a molar ratio of 1:x (1.01-1.10) (for example, ball milling is fully mixed), After the sintering process, during the sintering process, the positive electrode precursor material and the lithium-containing oxide undergo a high-temperature solid-phase reaction to form the positive electrode material, and the coating material coated on the surface of the positive electrode precursor material will be realized at high temperature. Surface coating and/or element doping of cathode materials.

In the present invention, the positive electrode material includes a lithiated positive electrode material and a positive electrode precursor material. The particle size of the positive electrode material is 1-100 μm. In an optional embodiment, the dispersion method of dispersing the positive electrode material into the cationic solution or the anionic solution to obtain the positive electrode material mixture is ultrasonic dispersion, the ultrasonic power is 100-500 W, and the ultrasonic time is 1-180 min.

In the present invention, the lithium ion battery includes: a positive electrode, a negative electrode, and a separator or a solid electrolyte for separating the positive and negative electrode materials. The positive electrode material of the battery is the surface modified positive electrode material based on the surface modification of the ion exchange membrane according to the present invention. The separator or solid electrolyte includes PP, celgard, garnet type solid electrolyte, NASICON type solid electrolyte, sulfide solid electrolyte, and perovskite type solid electrolyte. The negative electrode is graphite, silicon carbon, silicon dioxide, silicon alloy, tin oxide, metallic lithium or lithium alloy.

Specifically, the surface-modified positive electrode material is uniformly mixed with conductive carbon and a binder to form a slurry and coated on the aluminum foil, and the dried aluminum foil loaded with the slurry is cut into small discs with a cutting machine to be used as the positive electrode . A full cell was formed and tested for characterization.

The following further examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention, and should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art according to the above content of the present invention belong to the present invention. scope of protection. The specific process parameters and the like in the following examples are only an example of a suitable range, that is, those skilled in the art can make selections within the suitable range through the description herein, and are not intended to be limited to the specific numerical values exemplified below.

Example 1

Assemble the device diagram shown in Figure 1. The ion-exchange membrane used in the device is Nafion 117, a proton-exchange membrane produced by DuPont. Before use, the Nafion 117 membrane was boiled in a 5wt% H ₂ O ₂ aqueous solution at 80°C for 1 h to remove organic impurities in the membrane. Secondly, the membrane was repeatedly rinsed with deionized water, and then immersed in deionized water at 80°C and boiled for 1 h to completely remove the residual H ₂ O ₂ . The membranes were again soaked in 80°C, ₅ wt% _H2SO4 solution and boiled for 1 h. Finally, the membrane was rinsed repeatedly with deionized water, and then immersed in deionized water at 80°C for 1 h and heat-treated to completely remove the residual H ₂ SO ₄ in the membrane. The purpose of the proton exchange membrane Nafion 117 treatment is to activate the proton exchange membrane so that it has a cation exchange effect.

Step 1): Weigh NaOH and dissolve it in the aqueous solution, and prepare an aqueous NaOH solution with a concentration of 0.1 mol/L as an anion solution. Mix 4g of nickel-cobalt-manganese ternary precursor material (Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ ) with the obtained anion solution according to a mass ratio of 1:20, and disperse the mixed solution by ultrasonic, and the ultrasonic time is 10 min to obtain a positive electrode material mixture.

Step 2): Dissolve MnCl ₂ in water to prepare a 0.1 mol/L MnCl ₂ solution (80 mL) as a cation solution.

Step 3): inject the positive electrode material mixture obtained in step 1) and the cationic solution obtained in step 2) into the anion chamber and the cation chamber respectively, keep the stirring of the anion chamber and the cation chamber always on, and coat the surface of the precursor, and the coating time For 4h, the coating temperature is 25 ℃. After the coating is completed, the anion chamber mixed solution is centrifuged, the centrifugation speed is 3000rpm, and the centrifugation time is 3min. The solid material obtained by centrifugation was dried in a vacuum oven at a drying temperature of 80° C. and a drying time of 24 h. The ternary cathode precursor material with surface Mn(OH) ₂ coating was obtained.

Step 4): The coated ternary precursor material obtained in step 3) is fully mixed with LiOH·H ₂ O according to the molar ratio of 1:1.05 by ball milling, and then sintered in a pure oxygen atmosphere in two steps: the first sintering temperature The sintering temperature in the second step is 750°C, the holding time is 12h, and the heating rate is 3°C/min. A surface-modified positive electrode material is obtained.

The obtained surface-modified cathode material was used as a cathode active material to prepare an electrode and assemble a button battery. Assembly and testing of CR2025 coin cell: The surface-modified positive electrode material, conductive carbon (Super P:VGCF=1:1), and polyvinylidene fluoride (PVDF) were made into a slurry with a mass ratio of 8:1:1 Coated on the aluminum foil, the dried aluminum foil loaded with the slurry was cut into small discs with a diameter of 1.2 cm using a cutting machine as the positive electrode, the metal lithium sheet was used as the negative electrode, Celgard was used as the separator, and 1M carbonate solution was used as The electrolyte (wherein the solvent is a mixed solution of ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) in a volume ratio of 1:1:1, and the solute is LiPF ₆ ), in argon A CR2025 button battery is assembled in the gas glove box.

Example 2

Step 1): Weigh NaOH and dissolve it in an aqueous solution to prepare a 0.1 mol/L anion solution. Mix 4g of nickel-cobalt-manganese ternary precursor material (Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ ) with the obtained anion solution according to a mass ratio of 1:20, and disperse the mixed solution by ultrasonic, and the ultrasonic time is 10 min to obtain a positive electrode material mixture;

Step 2): dissolve Mn(C ₂ O ₂ H ₃ ) ₂ in water, and prepare a 0.2 mol/L Mn(C ₂ O ₂ H ₃ ) ₂ solution (80 mL) as a cationic solution;

Step 3): inject the precursor mixed solution obtained in step 1) and the cation solution obtained in step 2) into the anion chamber and the cation chamber respectively, keep the stirring of the anion chamber and the cation chamber always on, and coat the surface of the precursor, and the coating time is 4h, the coating temperature is 25 ℃. After the coating is completed, the anion chamber mixed solution is centrifuged, the centrifugation speed is 3000rpm, and the centrifugation time is 3min. The solid material obtained by centrifugation was dried in a vacuum oven at a drying temperature of 80° C. and a drying time of 24 h. A ternary cathode precursor material with surface Mn(OH) ₂ coating was obtained;

Step 4): The coated ternary precursor material obtained in step 3) is fully mixed with LiOH·H ₂ O according to the molar ratio of 1:1.05 by ball milling, and then sintered in a pure oxygen atmosphere in two steps: the first sintering temperature The sintering temperature in the second step is 750°C, the holding time is 12h, and the heating rate is 3°C/min. The surface-modified positive electrode material is obtained; the obtained surface-modified positive electrode material is prepared into an electrode and a button battery is assembled, and the preparation process is the same as that of Example 1.

Example 3

Step 1): Weigh NaOH and dissolve it in an aqueous solution to prepare a 0.1 mol/L anion solution. Mix 4g of nickel-cobalt-manganese ternary precursor material (Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ ) with the obtained anion solution according to a mass ratio of 1:20, and disperse the mixed solution by ultrasonic, and the ultrasonic time is 10 min to obtain a positive electrode material mixture;

Step 2): Dissolve Co(C ₂ O ₂ H ₃ ) ₂ in water to prepare a Co(C ₂ O ₂ H ₃ ) ₂ solution (80 mL) with a concentration of 0.2 mol/L as a cation solution;

Step 3): inject the precursor mixed solution obtained in step 1) and the cation solution obtained in step 2) into the anion chamber and the cation chamber respectively, keep the stirring of the anion chamber and the cation chamber always on, and coat the surface of the precursor, and the coating time is 4h, the coating temperature is 25 ℃. After the coating is completed, the anion chamber mixed solution is centrifuged, the centrifugation speed is 3000rpm, and the centrifugation time is 3min. The solid material obtained by centrifugation was dried in a vacuum oven at a drying temperature of 80° C. and a drying time of 24 h. A ternary cathode precursor material with surface Co(OH) ₂ coating was obtained;

Step 4): The coated ternary precursor material obtained in step 3) is fully mixed with LiOH·H ₂ O according to the molar ratio of 1:1.05 by ball milling, and then sintered in a pure oxygen atmosphere in two steps: the first sintering temperature The sintering temperature in the second step is 750°C, the holding time is 12h, and the heating rate is 3°C/min. The surface-modified positive electrode material is obtained; the obtained surface-modified positive electrode material is prepared into an electrode and a button battery is assembled, and the preparation process is the same as that of Example 1.

Example 4

Step 1): Weigh NaOH and dissolve it in an aqueous solution to prepare a 0.1 mol/L anion solution. Mix 4 g of nickel-cobalt-manganese ternary precursor material (Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ ) with the obtained anion salt solution according to a mass ratio of 1:20, and disperse the mixed solution by ultrasonic, and the ultrasonic time is 10 min to obtain Positive electrode material mixture.

Step 2): Dissolve MnCl ₂ and Co(NO ₃ ) ₂ in water at a molar amount of 1:1 to prepare a 0.1 mol/L cation solution (80 mL).

Step 3): inject the precursor mixed solution obtained in step 1) and the cation solution obtained in step 2) into the anion chamber and the cation chamber respectively, keep the stirring of the anion chamber and the cation chamber always on, and coat the surface of the precursor, and the coating time is 4h, the coating temperature is 25 ℃. After the coating is completed, the anion chamber mixed solution is centrifuged, the centrifugation speed is 3000rpm, and the centrifugation time is 3min. The solid material obtained by centrifugation was dried in a vacuum oven at a drying temperature of 80° C. and a drying time of 24 h. The ternary cathode precursor material with surface Mn _f Co _g (OH) ₂ (f+g=1) coating was obtained.

Step 4): The coated ternary precursor material obtained in step 3) is fully mixed with LiOH·H ₂ O according to the molar ratio of 1:1.05 by ball milling, and then sintered in a pure oxygen atmosphere in two steps: the first sintering temperature The sintering temperature in the second step is 750°C, the holding time is 12h, and the heating rate is 3°C/min. A surface-modified positive electrode material is obtained.

The obtained surface-modified positive electrode material was prepared into an electrode and a button battery was assembled, and the process was the same as that of Example 1.

Example 5

Step 1): Weigh (NH ₄ ) ₂ HPO ₄ and dissolve it in an aqueous solution to prepare a 0.1 mol/L anion solution. Mix 4g of nickel-cobalt-manganese ternary precursor material (Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ ) with the obtained anion solution according to a mass ratio of 1:20, and disperse the mixed solution by ultrasonic, and the ultrasonic time is 10 min to obtain a positive electrode material mixture;

Step 2): Dissolve Al(NO ₃ ) ₃ ·9H ₂ O in water to prepare a 0.1 mol/L cationic solution (80 mL);

Step 3): inject the precursor mixed solution obtained in step 1) and the cation solution obtained in step 2) into the anion chamber and the cation chamber respectively, keep the stirring of the anion chamber and the cation chamber always on, and coat the precursor, and the coating time is 4h , the coating temperature is 25℃. After the coating is completed, the anion chamber mixed solution is centrifuged, the centrifugation speed is 3000rpm, and the centrifugation time is 3min. The solid material obtained by centrifugation was dried in a vacuum oven at a drying temperature of 80° C. and a drying time of 24 h. A ternary cathode precursor material coated with AlPO ₄ was obtained;

Step 4): The coated ternary precursor material obtained in step 3) is fully mixed with LiOH·H ₂ O according to the molar ratio of 1:1.05 by ball milling, and then sintered in a pure oxygen atmosphere in two steps: the first sintering temperature The sintering temperature in the second step is 750°C, the holding time is 12h, and the heating rate is 3°C/min. A surface-modified positive electrode material is obtained.

The surface-modified positive electrode material was prepared into an electrode and a button battery was assembled, and the process was the same as that of Example 1.

Example 6

Step 1): Weigh LiOH·H ₂ O and dissolve it in an aqueous solution to prepare a 0.1 mol/L anion solution. Mix 4g of nickel-cobalt-manganese ternary precursor material (Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ ) with the obtained anion solution according to a mass ratio of 1:20, and disperse the mixed solution by ultrasonic, and the ultrasonic time is 10 min to obtain a positive electrode material mixture;

Step 2): Dissolve Al(NO ₃ ) ₃ ·9H ₂ O in water to prepare a 0.1 mol/L cationic solution (80 mL);

Step 3): inject the precursor mixed solution obtained in step 1) and the cation solution obtained in step 2) into the anion chamber and the cation chamber respectively, keep the stirring of the anion chamber and the cation chamber always on, and coat the precursor, and the coating time is 4h , the coating temperature is 25℃. After the coating time is over, the anion chamber mixed solution is centrifuged at 3000 rpm for a centrifugation time of 3 min. The solid material obtained by centrifugation was dried in a vacuum oven at a drying temperature of 80° C. and a drying time of 24 h. A LiAlO ₂ -coated ternary cathode precursor material was obtained;

Step 4): The coated ternary precursor material obtained in step 3) is fully mixed with LiOH·H ₂ O according to a molar ratio of 1:1.05 by ball milling, and then sintered in two steps in a pure oxygen atmosphere. The first sintering temperature The sintering temperature in the second step is 750°C, the holding time is 12h, and the heating rate is 3°C/min. A surface-modified positive electrode material is obtained.

The obtained surface-modified positive electrode material was prepared into an electrode and a button battery was assembled, and the process was the same as that of Example 1.

Example 7

Step 1): Weigh LiOH·H ₂ O and dissolve it in an aqueous solution to prepare a 0.1 mol/L anion solution. Mix 4g of nickel-cobalt-manganese ternary precursor material (Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ ) with the obtained anion solution according to a mass ratio of 1:20, and disperse the mixed solution by ultrasonic, and the ultrasonic time is 10 min to obtain a positive electrode material mixture;

Step 2): Dissolve 0.49 g of ZrO(NO ₃ ) ₂ ·5H ₂ O in water to prepare a 0.1 mol/L cationic solution (80 mL);

Step 3): inject the precursor mixed solution obtained in step 1) and the cation solution obtained in step 2) into the anion chamber and the cation chamber respectively, keep the stirring of the anion chamber and the cation chamber always on, and coat the precursor with ZrO ₂ , and the coating time For 4h, the coating temperature is 25 ℃. After the coating time is over, the anion chamber mixed solution is centrifuged at 3000 rpm for a centrifugation time of 3 min. The solid material obtained by centrifugation was dried in a vacuum oven at a drying temperature of 80° C. and a drying time of 24 h. A ZrO ₂ -coated ternary cathode precursor material was obtained;

Step 4): The coated ternary precursor material obtained in step 3) is fully mixed with LiOH·H ₂ O according to the molar ratio of 1:1.05 by ball milling, and then sintered in a pure oxygen atmosphere in two steps: the first sintering temperature The sintering temperature in the second step is 750°C, the holding time is 12h, and the heating rate is 3°C/min. A surface-modified positive electrode material is obtained.

The obtained surface-modified positive electrode material was prepared into an electrode and a button battery was assembled, and the process was the same as that of Example 1.

Comparative Example 1

The nickel-cobalt-manganese ternary precursor material (Ni _0.83 Co _0.12 Mn _0.05 (OH) ₂ ) was directly mixed with LiOH·H ₂ O according to the molar ratio of 1:1.05 by ball milling, and then sintered in two steps in a pure oxygen atmosphere. The sintering temperature in the first step was 400°C, and the holding time was 2h; the sintering temperature in the second step was 750°C, and the holding time was 12h; the heating rate was 3°C/min. A surface-modified positive electrode material is obtained.

The obtained surface-modified positive electrode material was prepared into an electrode and a button battery was assembled, and the process was the same as that of Example 1.

Figure 1 shows a device for surface modification of the positive electrode, respectively. The device is mainly divided into cation chamber, anion chamber, ion exchange membrane and stirring or flow system. When in use, the anions and cations constituting the coating material are placed in the anion chamber and the cation chamber respectively, and the positive electrode material is optionally placed in the anion chamber or the cation chamber according to the type of ion exchange membrane selected to obtain a positive electrode material mixture. The components in the figures are not drawn to scale, emphasis instead being placed upon presenting exemplary embodiments, embodiments, and principles of the apparatus. It is to be understood that the application is not limited to the details or methodology set forth in the specification or illustrated in the accompanying drawings. It is also to be understood that the terminology used in this disclosure is for the purpose of description only and should not be regarded as limiting.

FIG. 2 shows the X-ray diffraction (XRD) pattern of the positive electrode, and the positive electrode material includes Example 1 with surface modification and Comparative Example 1 without surface modification. All diffraction peaks matched well with the typical hexagonal a-NaFeO ₂ structure (JCPDF card number 01-089-4533, space group R-3m), which represents the main phase of NCM. The a-NaFeO ₂ -type crystal structure is an ordered rock-salt type, with Li and Me ions occupying alternating (111) layers. The NCM has a layered _NaFeO2 structure with R-3m space group, with alternating layers formed by _LiO6 and _MO6 octahedra. From Fig. 1, it can be seen that the main diffraction peaks of all samples match well with the JCPDF card with R-3m space group. It shows that the surface modification of the method of the present invention does not change the layered structure of the NCM material.

Figure 3 shows the dQ/dV curves of cathode materials including surface-modified Example 1 (B) and non-surface-modified Comparative Example 1 (A) at different cycles. The dQ/dV curve shows that after cycling, the peak position of the dQ/dV curve of Comparative Example 1 has shifted severely, and the charging peak has shifted to the right, indicating that the material undergoes severe polarization during cycling; the phase transition peak at high voltage The H2-H3 gradually disappeared, indicating that the high-voltage cathode material had undergone a severe phase transition. In contrast, the position of the peak in Example 1 did not shift significantly, indicating that the polarization and phase transition of the cathode material during cycling were small. It is fully demonstrated that the surface modification method of nickel-cobalt-manganese ternary cathode materials based on the aminolysis reaction is beneficial to suppress the polarization and phase transition of cathode materials during cycling.

FIG. 4A and FIG. 4B compare the cycle performance of the cathode materials obtained by surface modification Example 1, Example 2 and Example 3, and Comparative Example 1 without surface modification. The results show that the cycle performance of the surface-modified cathode material using the method of the present invention is significantly improved. After cycling under the same conditions, the capacity retention rate of the surface-modified cathode material is significantly higher than that of the non-surface-modified cathode material, indicating that The surface modification implemented in the present invention can significantly improve the cycle stability of the cathode material. The effectiveness of the device and method for surface modification of cathode materials based on ion exchange membranes is fully demonstrated.

FIG. 5 shows a rate comparison chart of positive electrode materials, including surface-modified Example 1 and non-surface-modified Comparative Example 1. FIG. The results show that the device and method for surface modification of cathode materials based on ion-exchange membranes have significantly improved the rate performance of nickel-cobalt-manganese cathode materials after surface modification, and can release more capacity at high rates, which fully shows that the ion-based The device and method for surface modification of the positive electrode material of the exchange membrane can improve the rate performance of the positive electrode material.

FIG. 6 shows SEM images of cross-sections of cathode particles before and after cycling of cathode materials including surface-modified Example 1 and unmodified Comparative Example 1. FIG. The results show that both Example 1 and Comparative Example 1 are secondary particles formed by agglomeration of primary particles. Before the cycle, the primary particles are tightly bound, and there is no obvious crack between the secondary particles. After 1C rate and 150 cycles, Example 1 maintained the complete spherical secondary particle morphology, while the positive electrode particles of Comparative Example 1 had been significantly broken. It is shown that the device and method for surface modification of cathode materials based on ion exchange membranes can suppress particle breakage of cathode materials during cycling.

The above-mentioned embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention. The protection scope of the present invention is subject to the claims.

Claims (16)

1. a device based on the surface modification of the positive electrode material of ion exchange membrane, is characterized in that, comprises: a cation chamber containing a cation solution; an anion chamber, the anion chamber contains an anion solution; An ion-exchange membrane for physically separating an anion compartment and a cation compartment, the ion-exchange membrane including a cation-exchange membrane and an anion-exchange membrane; and a stirring system or/and a flow system respectively connected to the cation chamber and the anion chamber respectively arranged at the bottom of the cation chamber and the anion chamber. 2. The device for surface modification of positive electrode material based on ion exchange membrane according to claim 1, wherein the flow system comprises: The cationic solution storage tank, the flow pump and the flow pipeline connecting the cationic chamber and the cationic solution storage tank; The anion solution storage tank is connected with the flow pump and the flow pipeline of the anion chamber and the anion solution storage tank. 3. the device based on the surface modification of the positive electrode material of ion exchange membrane according to claim 1, is characterized in that, described stirring system comprises at least one in magnetic stirring device, mechanical stirring device and ultrasonic stirring device, set respectively at the bottom of the anion compartment and the bottom of the anion compartment. 4. The device for surface modification of positive electrode material based on ion exchange membrane according to claim 1, wherein the active group in the cation exchange membrane comprises sulfonic acid group, phosphoric acid group, carboxylic acid group, phenolic group. At least one of arsenic acid group and selenic acid group; the active group in the anion exchange membrane includes at least one of the amino group and the aryl amino group of the primary, secondary, tertiary and quaternary amines. 5. The device for surface modification of a positive electrode material based on an ion exchange membrane according to claim 1, wherein the positive electrode material comprises a lithiated positive electrode material and a positive electrode precursor material; The cathode material after lithiation includes LiNi _b Co _{c Mn 1-bc} O ₂ (wherein 0≤b≤1, 0≤c≤1); and LiNi _m Con Al _1-mn O ₂ (0≤m≤1) , 0≤n≤1); The positive electrode precursor material includes Ni _(1-yz) Co _y Mn _z (OH) ₂ (wherein 0≤y≤1, 0≤z≤1) and Ni _(1-ad) Co _a Al _d (OH) ₂ (where 0≤a≤1, 0≤d≤1). 6. The device for surface modification of positive electrode material based on ion exchange membrane according to any one of claims 1-5, wherein the solute in the cationic solution is selected from Al(NO ₃ ) ₃ , Al ₂ ( SO ₄ ) ₃ , AlCl ₃ , MnCl ₃ , Co(NO ₃ ) ₃ , Co ₂ (SO ₄ ) ₃ , Fe(NO ₃ ) ₃ , Fe ₂ (SO ₄ ) ₃ , FeCl ₃ , Cr(NO ₃ ) ₃ At least one of , Cr ₂ (SO ₄ ) ₃ , CrCl ₃ , Zr(NO ₃ ) ₄ , ZrCl ₄ , Zn(NO ₃ ) ₃ , TiBr ₄ ; The solvent in the cationic solution includes at least one of distilled water, methanol, ethanol, isopropanol, n-butanol, isobutanol, cycloethanol, acetone, cyclohexanone, glycerol and ethyl acetate; The concentration of the cation solution is 0.01mol/L～10mol/L. 7. The device for surface modification of positive electrode material based on ion exchange membrane according to any one of claims 1-6, wherein the solute in the anion solution is selected from KOH, NaOH, LiOH, (NH ₄ ) At least one of KF among ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , H ₃ PO ₄ , NH ₃ ·H ₂ O, LiF, and NaF; The solvent in the anion solution includes at least one of distilled water, methanol, ethanol, isopropanol, n-butanol, isobutanol, cycloethanol, acetone, cyclohexanone, glycerol and ethyl acetate; The concentration of the anion solution is 0.01mol/L～10mol/L; Preferably, the device for surface modification of the positive electrode material based on the ion exchange membrane further comprises an external power supply connected to the cation chamber and the anion chamber. 8. a surface modification method of positive electrode material, is characterized in that, comprises: (1) Disperse the positive electrode material in the cation solution or the anion solution in the device for surface modification of the positive electrode material based on the ion exchange membrane according to claim 1, and combine the anion solution with the cation solution through a stirring system or a flow system and cause precipitation The reaction or redox reaction generates precipitation, thereby forming a coating material on the surface of the positive electrode material or at the particle pores of the positive electrode material, and then separating and drying to obtain a positive electrode material with the coating material distributed on the surface; (4) heat-treating the positive electrode material on which the coating substance is distributed on the surface to obtain a surface-modified positive electrode material. 9. The surface modification method according to claim 8, wherein when the ion exchange membrane is a cation exchange membrane, the positive electrode material is dispersed in the anion chamber; when the ion exchange membrane is an anion exchange membrane, the positive electrode material is dispersed In the cation chamber; the particle size of the positive electrode material is 1-100 μm. 10. The surface modification method according to claim 8, wherein a mixed solution is obtained by mixing a cationic solution or an anionic solution and a positive electrode material; the solid content of the positive electrode material in the mixed solution is 2wt%-20wt%; The temperature of the precipitation reaction or the redox reaction is 20-100°C, and the time is 0.5h-36 hours. 11 . The surface modification method according to claim 8 , wherein the coating material in the positive electrode material with the coating material distributed on the surface comprises Mn(OH) ₂ , Co(OH) ₂ , AlPO ₄ , Mn ₃ (PO ₄ ) ₂ , FePO ₄ , Li ₃ PO ₄ , AlF ₃ , LiAlO ₂ , Li ₂ ZrO ₃ , Li ₄ Ti ₅ O1 ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ , ZnO, Al(OH) ₃ and one or more of Zr(OH) ₄ ; the mass of the coating material is 0.1% to 10% of the mass of the positive electrode material. 12. The surface modification method according to any one of claims 8-11, wherein when the positive electrode material is a lithiated positive electrode material, the temperature of the heat treatment is 600-800°C, and the heat treatment time is 2 ~10h, the heat treatment atmosphere is pure oxygen or air. 13. The method for surface modification according to any one of claims 8-11, wherein, when the positive electrode material is a positive electrode precursor material, the obtained surface is distributed with a positive electrode material and a lithium oxide mixed with a coating material. Sintering treatment to obtain a surface-modified positive electrode material; the lithium-containing oxide includes at least one of LiOH·H ₂ O, LiNO ₃ , Li ₂ CO ₃ , Li ₂ O and Li ₂ O ₂ , and the surface is distributed with The molar ratio of the positive electrode material of the coating material and the lithium-containing oxide is 1:(1.01-1.10). 14 . The surface modification method according to claim 13 , wherein the sintering treatment comprises: one-step sintering or two-step sintering; the atmosphere of the sintering treatment is pure oxygen or air. 15 . Wherein, the one-step sintering includes: the sintering temperature is 600-850°C, the holding time is 10h-20h, and the heating rate of the one-step sintering is preferably 2-5°C/min; The two-step sintering includes: the sintering temperature in the first step is 300-500°C, and the holding time is 2h-4h; the sintering temperature in the second step is 700-850°C, and the holding time is 10h-20h; preferably, the heating rate of the two-step sintering is It is 2～5℃/min. 15. A surface-modified positive electrode material prepared according to the surface modification method of any one of claims 8-14. 16. A lithium ion battery, comprising: a negative electrode material, the surface-modified positive electrode material of claim 15, and a separator or a solid electrolyte separating the surface-modified positive electrode material and the negative electrode material; Preferably, the separator comprises polypropylene separator (PP) and celgard separator, and the solid electrolyte comprises garnet type solid electrolyte, NASICON type solid electrolyte, sulfide solid electrolyte and perovskite type solid electrolyte; Preferably, the negative electrode material is graphite, silicon carbon, silicon dioxide, silicon alloy, tin oxide, metallic lithium or lithium alloy.

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