Electrochemical in-situ metal ion doping and coating method for auxiliary electrode material by external physical field

Abstract

The invention discloses an electrochemical in-situ metal ion doping and coating method of an external physical field auxiliary electrode material. The method comprises the following steps: preparing an electrolyte matched with the electrode material to be modified; coating the surface of a current collector with an electrode material, taking a metal simple substance consistent with metal ions contained in the electrode material as a negative electrode, taking the obtained solution as an electrolyte, and assembling into a battery; placing the battery in a constant-temperature box, and standing for a certain time at a specified temperature, so that the electrolyte fully wets the electrode material; and placing the battery after standing in an external physical field matched with the target material, and applying a specified current signal within a specified voltage range, so that the electrolyte and the electrode material fully react in an electrochemical environment, and the modification of the target material can be completed. According to the method, in-situ modification of the electrode material is assisted through an external physical field, the method does not depend on replacement of an upstream electrode material production enterprise production line, and the properties of the electrode material can be flexibly regulated and controlled according to requirements in a downstream battery assembly enterprise.

Description

Technical Field

[0001] The invention relates to the field of electrochemical technology, in particular to an electrochemical in-situ metal ion doping and coating method for an externally applied physical field-assisted electrode material. Background Art

[0002] Alkali metal batteries, represented by lithium-ion batteries, are widely used in daily life due to their advantages of high energy density, high output voltage and long cycle life. Electrode materials, as an important component of alkali metal batteries, determine the upper limit of battery energy density. As people have higher and higher requirements for the performance of alkali metal batteries, the modification of electrode materials has received widespread attention as one of the important ways to develop safe, reliable, green and environmentally friendly batteries with high specific energy and long life. Among them, ion doping and coating are common material modification methods to maintain the stability of electrode materials, improve the electronic conductivity of the electrode electrolyte interface phase and enhance the reversible capacity of the battery. These strategies can effectively inhibit ion mixing, prevent the dissolution of transition metals from the material, and improve the stability of the material's crystal structure.

[0003] At present, common doping and coating methods include solid phase method, hydrothermal method, coprecipitation method, sol-gel method and spray pyrolysis method. The solid phase method is easy to operate but the material dispersion is uneven. The hydrothermal method and coprecipitation method need to consider the selection of materials and solutions and the reaction conditions. Although the spray pyrolysis method has good effects, it has more control variables. There are many operational uncertainties in the modification methods of various electrode materials. How to reduce the operational risks of material synthesis, improve the success rate of material synthesis, and improve the battery performance after material modification are the key points worthy of attention in the process of positive electrode material modification. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention provides an electrochemical in-situ metal ion doping and coating method for an electrode material assisted by an external physical field.

[0005] In order to achieve the above purpose, the technical solutions provided are as follows:

[0006] An electrochemical in-situ metal ion doping and coating method for an electrode material with an external physical field auxiliary is characterized by comprising the following steps:

[0007] Step 1: preparing an electrolyte that matches the electrode material to be modified;

[0008] Step 2: coating the electrode material onto the surface of the current collector, using a metal element consistent with the metal ions contained in the electrode material as the negative electrode, and using the solution obtained in step 1 as the electrolyte to assemble into a battery;

[0009] Step 3: Place the battery in a constant temperature box and let it stand for a certain period of time at a specified temperature to allow the electrolyte to fully wet the electrode material;

[0010] Step 4: Place the static battery in an external physical field that matches the target material, and apply a specified current signal within a specified voltage range to allow the electrolyte and electrode material to fully react in the electrochemical environment to complete the modification of the target material.

[0011] Preferably, in step one, the electrolyte uses esters, ethers or ionic liquids as solvents, and the electrolyte uses soluble compounds formed by doping or coating elements as solutes.

[0012] Preferably, in step 2, the material of the current collector is copper or aluminum.

[0013] Preferably, in step 2, the negative electrode metal element is consistent with the element to be doped.

[0014] Preferably, in step 2, the battery refers to an electrochemical system having a positive electrode, a negative electrode, and an electrolyte.

[0015] Preferably, in step three, the temperature of the thermostat is 20°C to 50°C.

[0016] Preferably, in step three, the standing time is related to the rate of change of the open circuit voltage of the battery, and when the open circuit voltage changes by no more than 10 mV within 1 minute, it represents that the electrolyte has fully infiltrated the electrode material, and the standing time is ended.

[0017] Preferably, in step four, the external physical field includes a coupled field of one or more physical fields selected from the group consisting of a magnetic field, an electric field, an acoustic field, a temperature field, a force field, and a microwave field.

[0018] Specifically, the magnetohydrodynamics of the magnetic field will affect the diffusion behavior of charged particles in the fluid or solid-liquid interface, the magnetic field-induced magnetic dipole interaction will affect the directional assembly of nano-units, the repulsive force caused by the magnetic field gradient will change the structure and morphology of the material, and the magnetizing force will affect the particles and thus the morphology of the material; the frequency and direction of the alternating electric field will affect metal deposition, and the electrostatic induction effect will affect the deposition dynamics of deposits on the solid surface; the temperature field will affect the ion diffusion dynamics in the solid solution material; the electric polarization, induced polarization, and cavitation effects caused by the mechanical effect of the acoustic field will affect the uniformity of the deposition of the substance on the surface of the electrode material; the force field will change the lattice spacing and the creep velocity of the material and the charge distribution inside the material, thereby affecting the doping effect.

[0019] The beneficial effects of the present invention are:

[0020] The present invention uses an external physical field method to assist in the in-situ modification of electrode materials, and the physical fields involved include magnetic fields, electric fields, acoustic fields, temperature fields, force fields, and coupled fields of one or more physical fields in microwave fields. By using an external physical field to assist in the in-situ modification of electrode materials, it is not necessary to replace the production line of upstream electrode material manufacturers, and downstream battery assembly companies can flexibly adjust the properties of electrode materials according to demand, which has significant advantages in small-batch customized production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the XRD pattern of the original Si material in Example 1 of the present invention;

[0022] Figure 2 is the XRD pattern of the modified Si material in Example 1 of the present invention;

[0023] Figure 3 This is a comparative SEM image of the coating modification in Example 1 of the present invention;

[0024] Figure 4 This is a cycle performance diagram of the electrode material before and after coating and modification in Example 1 of the present invention;

[0025] Figure 5 This is an EDS image of the material coated on the Al current collector before doping and modification in Example 2 of the present invention;

[0026] Figure 6 This is an EDS image of the material coated on the Al current collector after doping and modification in Example 2 of the present invention;

[0027] Figure 7 This is a comparative TEM image of doping modification in Example 2 of the present invention;

[0028] Figure 8 This is a comparison chart of the cycle performance of the lithium nickel manganese oxide material before and after modification in Example 2 of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] An electrochemical in-situ metal ion doping and coating method for an external physical field-assisted electrode material comprises the following steps:

[0032] Step 1: Disperse 0.06 g of ferrocene in 20 mL of DMC solution and stir evenly to make sure there are no suspended particles in the solution;

[0033] Step 2: Mix Si particles and polyvinylidene fluoride binder in a mass ratio of 92:8, and use N-methylpyrrolidone as a dispersant to prepare a slurry, apply it on the surface of the copper current collector and use a forced air drying oven to dry at 90°C for 3 hours. Use single Fe as the negative electrode and a solution of ferrocene in DMC as the electrolyte to assemble a soft pack battery;

[0034] Step 3: Place the assembled soft-pack battery in a 30°C constant temperature box for more than 4 hours until the open circuit voltage changes by no more than 10mV within 1 minute;

[0035] Step 4: At a current density of 0.05 mA / cm 2 The battery is subjected to pulse discharge (external electric field) to oxidize the single substance Fe in the negative electrode to Fe 2+ , and migrate to the Si electrode surface for reduction. During the treatment process, 100W, 45kHz ultrasound was used to irradiate the battery, and the cavitation effect of ultrasound was used to accelerate the Fe 2+ The reduction deposition process on the Si electrode surface is continued until the voltage platform corresponding to the reaction ends, and finally Si particles coated with Fe elements are obtained, i.e., the modified Si electrode material.

[0036] Step 5: Conduct phase characterization test on the modified silicon negative electrode material, assemble button half-cells, and test cycle performance.

[0037] Figure 1 is the XRD pattern of Si material before modification, Figure 2 This is the XRD diagram of the modified Si material. It can be seen from the figure that the diffraction peak related to Fe obviously appears in the XRD spectrum of the modified Si material, which means that the surface of the material is coated with Fe element, which proves that the method described in this patent can be used for surface coating modification of electrode materials.

[0038] Figure 3 (a) is a scanning electron microscope image of a modified Si material synthesized by a solid phase method, and (b) is a modified Si material synthesized by in-situ electrochemical synthesis assisted by an alternating electric field and an ultrasonic coupling field. In contrast, the surface morphology of the material synthesized by electrochemical in-situ synthesis assisted by an alternating electric field and an ultrasonic coupling field is smoother, which means that the Fe element is deposited more evenly on the surface of the material, proving that the method described in this patent has significant advantages in coating uniformity compared to the traditional solid phase method.

[0039] Figure 4 The figure shows the cycle performance comparison of Si negative electrode half-cell before and after modification. It can be seen that the cycle stability of the modified material is also better than that of the traditional material synthesis method.

[0040] Example 2

[0041] An electrochemical in-situ metal ion doping and coating method for an external physical field-assisted electrode material comprises the following steps:

[0042] Step 1: preparing an electrolyte with aluminum hexafluorophosphate as a solute and a mixture of dimethyl carbonate and ethylene carbonate as a solvent;

[0043] Step 2: Mix lithium nickel manganese oxide particles and polyvinylidene fluoride binder in a mass ratio of 9:1, and use N-methylpyrrolidone as a dispersant to prepare a slurry, apply it on the surface of the aluminum current collector and use a vacuum drying oven to dry at 90°C for 3 hours. Use single Al as the negative electrode and the solution obtained in step 1 as the electrolyte to assemble the battery;

[0044] Step 3: Place the battery in a 25°C constant temperature box for more than 4 hours, until the open circuit voltage changes by no more than 10mV within 1 minute;

[0045] Step 4: At a current density of 0.05 mA / cm 2 The battery is charged under the condition of 0.3T magnetic field, the direction of magnetic flux lines is perpendicular to the plane where the electrode sheet is located, and the ambient temperature is controlled at 45℃, so that the electrolyte and electrode materials react fully in the electrochemical environment until the voltage platform corresponding to the reaction ends. That is, the Al-doped lithium nickel manganese oxide material is obtained;

[0046] Step 5: Conduct phase characterization tests on the modified lithium nickel manganese oxide material, assemble button half-cells, and test cycle performance.

[0047] Figure 5 and Figure 6 The EDS spectra of the materials before and after modification are shown respectively. The data prove that the Al ions in aluminum hexafluorophosphate can be embedded in lithium nickel manganese oxide crystals in an electrochemical environment to obtain doped modified materials.

[0048] Figure 7 In the figure, (a) is a TEM image of the lithium nickel manganese oxide material after Al is doped by the traditional solvent thermal method. The image shows that the color of the material image is uneven, which means that the phase distribution in the material is uneven; (b) is a TEM image of the lithium nickel manganese oxide material after Al is electrochemically doped in a magnetic field. The image shows that the color of the material is uniform. This data proves that the scheme proposed in this patent through the external physical field assisted electrochemical in-situ doping can uniformly modify the material, reduce the stress concentration between the phases inside the material crystal, and improve the stability of the material.

[0049] Figure 8It is shown that the method of electrochemical in-situ metal ion doping of electrode materials with an external physical field as assisted by the patent can make the modified material have higher cycle stability.

[0050] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. An electrochemical in-situ metal ion doping and coating method for an electrode material with an external physical field, characterized in that: The steps include: Step 1: preparing an electrolyte that matches the electrode material to be modified; Step 2: coating the electrode material onto the surface of the current collector, using a metal element consistent with the metal ions contained in the electrode material as the negative electrode, and using the solution obtained in step 1 as the electrolyte to assemble into a battery; Step 3: Place the battery in a constant temperature box and let it stand for a certain period of time at a specified temperature to allow the electrolyte to fully wet the electrode material; Step 4: Place the static battery in an external physical field that matches the target material, and apply a specified current signal within a specified voltage range to allow the electrolyte and electrode material to fully react in the electrochemical environment to complete the modification of the target material.

2. The electrochemical in-situ metal ion doping and coating method of an externally applied physical field-assisted electrode material according to claim 1, characterized in that: In step 1, the electrolyte uses esters, ethers or ionic liquids as solvents, and the electrolyte uses soluble compounds formed by doping or coating elements as solutes.

3. The electrochemical in-situ metal ion doping and coating method of an external physical field-assisted electrode material according to claim 1, characterized in that: In step 2, the material of the current collector is copper or aluminum.

4. The electrochemical in-situ metal ion doping and coating method of an external physical field-assisted electrode material according to claim 1, characterized in that: In step 2, the negative electrode metal element is consistent with the element to be doped.

5. The electrochemical in-situ metal ion doping and coating method of an external physical field-assisted electrode material according to claim 1, characterized in that: In step 2, the battery refers to an electrochemical system having a positive electrode, a negative electrode, and an electrolyte.

6. The electrochemical in-situ metal ion doping and coating method of an external physical field-assisted electrode material according to claim 1, characterized in that: In step three, the temperature of the constant temperature box is 20°C to 50°C.

7. The electrochemical in-situ metal ion doping and coating method of an external physical field-assisted electrode material according to claim 1, characterized in that: In step three, the standing time is related to the rate of change of the open circuit voltage of the battery. When the open circuit voltage changes by no more than 10 mV within 1 minute, it means that the electrolyte has fully infiltrated the electrode material, and the standing time is ended.

8. The electrochemical in-situ metal ion doping and coating method of an external physical field-assisted electrode material according to claim 1, characterized in that: In step four, the external physical field includes a coupled field of one or more physical fields selected from the group consisting of a magnetic field, an alternating electric field, an acoustic field, a temperature field, a force field, and a microwave field.

9. The electrochemical in-situ metal ion doping and coating method of an externally applied physical field-assisted electrode material according to claim 8, characterized in that: The magnetohydrodynamics of the magnetic field will affect the diffusion behavior of charged particles in the fluid or solid-liquid interface, the magnetic field-induced magnetic dipole interaction will affect the directional assembly of nano-units, the repulsive force caused by the magnetic field gradient will change the structure and morphology of the material, and the magnetizing force will affect the particles and thus the morphology of the material; the frequency and direction of the alternating electric field will affect metal deposition, and the electrostatic induction effect will affect the deposition dynamics of deposits on the solid surface; the temperature field will affect the ion diffusion dynamics in the solid solution material; the electric polarization, induced polarization, and cavitation effects caused by the mechanical effect of the acoustic field will affect the uniformity of the deposition of the substance on the surface of the electrode material; the force field will change the lattice spacing and the creep speed of the material and the charge distribution inside the material, thereby affecting the doping effect.

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