CN117832404A - Lithium ion battery silicon nitride negative electrode film and preparation method thereof - Google Patents

Abstract

The application discloses a silicon nitride negative electrode film of a lithium ion battery and a preparation method thereof, belonging to the technical field of lithium ion film batteries. The method adopts the magnetron sputtering method to prepare the silicon nitride anode film with compact and uniform structure, high specific capacity and high cycle stability, and the first charge-discharge specific capacity can reach 1121 mAh.g ^‑1 Capacity retention rate of 100 cyclesUp to 82%. The silicon nitride negative electrode film prepared by the method has the advantages of high specific capacity and high cycle stability, and the preparation process has the characteristics of high deposition efficiency, low cost, low energy consumption, greenness, no pollution and the like, and is favorable for industrial popularization and application.

Description

A lithium ion battery silicon nitride negative electrode film and preparation method thereof

Technical Field

The invention belongs to the technical field of lithium ion thin film batteries, and in particular relates to a lithium ion battery silicon nitride negative electrode film and a preparation method thereof.

Background technique

With the rapid development of lithium-ion batteries and their wide application in many fields, high specific capacity and long cycle life lithium batteries are an important direction for battery development. At present, commercial lithium-ion batteries use graphite negative electrode materials, and their theoretical specific capacity is only 372mAh/g, which limits the further improvement of lithium-ion battery performance. Silicon-based negative electrode materials are considered to be negative electrode materials that can replace graphite due to their high specific capacity, low discharge potential, and high cost performance. However, the volume change of pure silicon materials during the charging and discharging process is huge. If the stress generated by this cannot be suppressed or released in time, it will cause the rupture of the silicon negative electrode, which will lead to a sudden decrease in capacity and have a great negative impact on the battery's cycle performance. Silicon nitride is a common silicon-based compound, in which the Si-N bond can relieve and release the stress generated in the electrochemical reaction, and has a good buffering effect on the volume expansion during the battery charging and discharging process, thereby obtaining high cycle stability performance. In addition, silicon nitride materials have the advantages of high specific capacity, high strength, oxidation resistance, and impact resistance, and are therefore considered to be a very promising negative electrode material for lithium-ion batteries.

The existing methods for preparing silicon nitride negative electrode materials mainly use ball milling and pulsed laser deposition. For example, CN114335520A discloses a nitride high energy storage density negative electrode material and its preparation method, which uses ball milling process to compound silicon nitride powder and graphite oxide, and uses graphite oxide to coat silicon nitride to solve the problem of volume expansion of silicon nitride powder during the cycle, slow down the capacity decay caused by surface oxidation and dissolution of nitride, and thus improve the cycle performance of the battery. Suzuki et al. (Journal of Power Sources, 2013, 231, 186.) prepared silicon nitride film by pulsed laser deposition, and used it as the negative electrode of lithium ion battery, and found that the first charge and discharge specific capacity of silicon nitride film negative electrode can reach 1800 mAh g ^-1 . However, the above-mentioned method for preparing silicon nitride film negative electrode has problems such as complex process, high energy consumption, and difficulty in large-scale preparation, which limits the industrialization and promotion of silicon nitride film negative electrode materials.

Summary of the invention

Technical problem to be solved: In order to overcome the deficiencies in the prior art, the present application proposes a lithium-ion battery silicon nitride negative electrode film and a preparation method thereof, so as to solve the technical problems in the prior art such as complex process, high energy consumption, and difficulty in large-scale preparation.

Technical solutions

A method for preparing a lithium-ion battery silicon nitride negative electrode film, the specific steps of the preparation method are:

Step a, cleaning treatment of the current collector substrate: placing the current collector substrate in isopropanol, deionized water, and anhydrous ethanol in turn for ultrasonic cleaning, and drying at 150°C; placing the cleaned and dried current collector substrate on a substrate table in a vacuum chamber of a coating equipment, vacuuming to 1×10 ^-4 Pa, using argon as the working gas, turning on the ion source, and performing plasma cleaning treatment on the surface of the current collector substrate;

Step b, depositing a copper thin film layer: using a planar copper target as a target material and argon as a working gas, a DC magnetron sputtering process is used to deposit a copper thin film layer on the surface of the cleaned current collector substrate;

Step c, depositing a silicon nitride negative electrode film: using a planar silicon target as the target material, argon and nitrogen as the working gas, and adopting a radio frequency magnetron sputtering process to deposit a silicon nitride negative electrode film on the surface of the current collector substrate on which the copper film layer is deposited.

As a preferred technical solution of the present application: the conditions for plasma cleaning treatment on the surface of the current collector substrate in step a are: argon gas flow rate is 100 sccm, plasma cleaning treatment sputtering power is 400 W, and cleaning time is 30 s; the current collector substrate is a copper foil current collector substrate, and Ar+ plasma cleaning is performed on the surface of the copper foil current collector substrate.

As a preferred technical solution of the present application: the thickness of the copper thin film layer deposited on the surface of the current collector substrate in the step b is 20-30nm, and the DC magnetron sputtering process conditions adopted are: argon gas flow rate is 30sccm, chamber working gas pressure is 0.1-0.5Pa, sputtering power is 180-250W, sputtering deposition time is 2-4min, and current collector substrate temperature is 100-150℃.

As a preferred technical solution of the present application: the thickness of the silicon nitride negative electrode film prepared in the step c is 100-200nm, and the Si/N element ratio is 1:0.8-1:0.9; the RF magnetron sputtering process conditions adopted are: the argon flow rate is 40-60sccm, the nitrogen flow rate is 6-10sccm, the chamber working gas pressure is 0.5-2Pa, the sputtering power is 100-200W, the sputtering deposition time is 30-60min, and the collector substrate temperature for depositing the copper thin film layer is 100-150°C.

As a preferred technical solution of the present application: the step b is specifically as follows: fixing the planar copper target at the DC target position, adjusting the relative position of the target and the current collector substrate so that the target-substrate distance is 10 cm, starting the circulating water and power supply, heating the current collector substrate temperature to 100°C, evacuating to a vacuum degree of 1.6×10 ^-3 Pa, filling with 99.99% pure Ar at a flow rate of 30 sccm, the chamber working pressure is 0.35 Pa, and starting sputtering of the Cu transition layer. The copper target DC sputtering current is 0.5 A, the duty cycle is 50%, the substrate stage speed is 4 rpm, and the sputtering deposition time is 3 min to obtain a Cu transition layer with a thickness of 20 nm.

As a preferred technical solution of the present application: the parameters of step c are specifically set as: introducing 40 sccm of nitrogen and 8 sccm of nitrogen into the vacuum chamber, turning on the silicon target RF power supply, adjusting the target source power to 100 W, and sputtering deposition at 0.5 Pa for 40 minutes to obtain a silicon nitride negative electrode film with uniform surface morphology and dense structure.

The present application also discloses a lithium ion battery silicon nitride negative electrode film prepared by any of the above-mentioned methods for preparing the lithium ion battery silicon nitride negative electrode film.

Explanation of the principle of this application: The present invention adopts an industrially mature magnetron sputtering process to efficiently and low-temperature prepare silicon nitride negative electrode film, using silicon target as silicon source, argon as sputtering gas, and nitrogen as reaction gas. By adjusting parameters such as sputtering power, working gas pressure, atmosphere ratio, and deposition time, the structure and composition of the silicon nitride negative electrode film are optimized to prepare high-performance lithium-ion battery negative electrode film materials.

Beneficial effects: The silicon nitride negative electrode film prepared by the present invention has the advantages of high specific capacity and high cycle stability. Its preparation process has the characteristics of high deposition efficiency, low cost, low energy consumption, green and pollution-free, etc., which is conducive to industrial promotion and application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a SEM image of a lithium-ion battery silicon nitride negative electrode film of the present application;

FIG2 is a Si 2p XPS graph of the silicon nitride negative electrode film of the present application;

FIG3 is an N1s XPS graph of the silicon nitride negative electrode film of the present application;

FIG4 is a charge and discharge curve diagram of the silicon nitride negative electrode film of the present application under 0.5C condition;

FIG. 5 is a graph showing the cycle stability of the silicon nitride negative electrode film of the present application.

Detailed ways

The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and specific operation process are given, but the protection authority of the present invention is not limited to the following embodiments.

Embodiment 1:

A method for preparing a lithium-ion battery silicon nitride negative electrode film, the specific steps are:

Step a, cleaning treatment of the current collector substrate: placing the current collector substrate in isopropanol, deionized water, and anhydrous ethanol in turn for ultrasonic cleaning, and drying at 150°C; placing the cleaned and dried current collector substrate on a substrate table in a vacuum chamber of a coating device, vacuuming to 1×10 ^-4 Pa, using argon as the working gas, the argon flow rate is 100 sccm, the plasma cleaning treatment sputtering power is 400 W, and the cleaning time is 30 s; the current collector substrate is a copper foil current collector substrate, and the surface of the copper foil current collector substrate is cleaned by Ar+ plasma;

Step b, depositing a copper thin film layer: fixing a planar copper target at a DC target position, adjusting the relative position between the target and the current collector substrate so that the target-substrate distance is 10 cm, starting circulating water and power, heating the current collector substrate to 100°C, evacuating to a vacuum degree of 1.6×10 ^-3 Pa, and then charging Ar with a purity of 99.99% at a flow rate of 30 sccm. The chamber working pressure is 0.35 Pa, and sputtering of a Cu transition layer is started. The copper target DC sputtering current is 0.5 A, the duty cycle is 50%, the substrate stage speed is 4 rpm, and the sputtering deposition time is 3 min to obtain a Cu transition layer with a thickness of 20 nm.

Step c, depositing a silicon nitride negative electrode film: the Si/N element ratio is 1:0.8-1:0.9, and the temperature of the current collector substrate for depositing the copper thin film layer is 100-150°C; nitrogen gas with a flow rate of 40sccm and nitrogen gas of 8sccm are introduced into the vacuum chamber, the silicon target RF power supply is turned on, the target source power is adjusted to 100W, and sputtering deposition is performed at 0.5Pa for 40min. The thickness of the silicon nitride negative electrode film is 100-200nm, and a silicon nitride negative electrode film with uniform surface morphology and dense structure is obtained, as shown in Figure 1.

Embodiment 2:

XPS characterization test shows that the Si/N element ratio in the silicon nitride negative electrode film is 1:0.8-1:0.9 (Figure 2, Figure 3). The silicon nitride negative electrode film was cut into a 12mm diameter disc working electrode, a metal lithium sheet was used as the counter electrode, 1mol/LLiPF ₆ +EC/DMC/EMC (volume ratio of 1:1:1) was used as the electrolyte and a polypropylene film was used as the diaphragm to assemble and prepare a button cell. The test showed that the discharge specific capacity of the silicon nitride negative electrode film under 0.5C conditions was 1121mAh·g ^-1 (Figure 4), and the capacity retention rate of the battery after 100 cycles was 82% (Figure 5), indicating that the prepared silicon nitride negative electrode film has a high specific capacity and good cycle stability.

In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims (7)

1. The preparation method of the silicon nitride negative electrode film of the lithium ion battery is characterized by comprising the following specific steps of:

step a, cleaning a current collector substrate: sequentially placing the current collector substrate into isopropanol, deionized water and absolute ethyl alcohol for ultrasonic cleaning, and drying at 150 ℃; placing the cleaned and dried current collector substrate on a substrate table in a vacuum chamber of a coating device, starting to vacuumize to 1X 10 ^-4 Pa, taking argon as working gas, opening an ion source, and performing plasma cleaning treatment on the surface of the current collector substrate;

step b, depositing a copper film layer: using a planar copper target as a target material and argon as a working gas, and adopting a direct current magnetron sputtering process to deposit a copper film layer on the surface of the cleaned collector substrate;

step c, depositing a silicon nitride anode film: and depositing a silicon nitride negative electrode film on the surface of the current collector substrate on which the copper film layer is deposited by adopting a radio frequency magnetron sputtering process by taking a planar silicon target as a target material and argon and nitrogen as working gases.

2. The method for preparing the silicon nitride negative electrode film of the lithium ion battery according to claim 1, wherein the conditions for plasma cleaning treatment of the surface of the current collector substrate in the step a are as follows: argon flow is 100sccm, sputtering power of plasma cleaning treatment is 400W, and cleaning time is 30s; the current collector substrate is a copper foil current collector substrate, and Ar+ plasma cleaning is carried out on the surface of the copper foil current collector substrate.

3. The method for preparing a silicon nitride anode film of a lithium ion battery according to claim 1, wherein the thickness of a copper film layer deposited on the surface of the current collector substrate in the step b is 20-30nm, and the adopted direct current magnetron sputtering process conditions are as follows: the argon flow is 30sccm, the working pressure of the chamber is 0.1-0.5Pa, the sputtering power is 180-250W, the sputtering deposition time is 2-4min, and the temperature of the current collector substrate is 100-150 ℃.

4. The method for preparing the silicon nitride negative electrode film of the lithium ion battery according to claim 1, which is characterized in that: the thickness of the silicon nitride anode film prepared in the step c is 100-200nm, and the Si/N element ratio is 1:0.8-1:0.9; the adopted radio frequency magnetron sputtering process conditions are as follows: the argon flow is 40-60sccm, the nitrogen flow is 6-10sccm, the working pressure of the chamber is 0.5-2Pa, the sputtering power is 100-200W, the sputtering deposition time is 30-60min, and the temperature of the current collector substrate for depositing the copper film layer is 100-150 ℃.

5. The method for preparing a silicon nitride negative electrode film for a lithium ion battery according to claim 3, wherein the step b specifically comprises: fixing planar copper target at DC target position, adjusting relative position of target material and current collector substrate to make target base distance be 10cm, starting circulating water and power supply, heating current collector substrate to 100deg.C, vacuumizing to vacuum degree of 1.6X10 ^-3 And during Pa, filling Ar with the purity of 99.99% at the flow rate of 30sccm, wherein the working pressure of a chamber is 0.35Pa, starting to sputter the Cu transition layer, the sputtering current of a copper target Direct Current (DC) is 0.5A, the duty ratio is 50%, the rotating speed of a substrate table is 4rpm, and the sputtering deposition time is 3min, so that the Cu transition layer with the thickness of 20nm is obtained.

6. The method for preparing a silicon nitride negative electrode film for a lithium ion battery according to claim 4, wherein the parameters in the step c are specifically set as follows: and (3) introducing nitrogen with the flow of 40sccm and nitrogen with the flow of 8sccm into the vacuum chamber, opening a silicon target radio frequency power supply, adjusting the power of the target source to 100W, and performing sputter deposition under 0.5Pa for 40min to obtain the silicon nitride negative electrode film with uniform surface morphology and compact structure.

7. A silicon nitride negative electrode film for a lithium ion battery prepared by the method for preparing a silicon nitride negative electrode film for a lithium ion battery according to any one of claims 1 to 6.