CN118472231A - A micron silicon negative electrode and its application in sulfide all-solid-state batteries - Google Patents

Abstract

The invention discloses a micron silicon anode and application thereof in sulfide all-solid-state batteries, and belongs to the technical field of all-solid-state batteries. The preparation components of the micron silicon negative electrode are micron silicon negative electrode powder; the preparation method of the micron silicon negative electrode powder comprises the following steps: and standing and oxidizing the crystalline silicon powder in a water vapor atmosphere to obtain the micron silicon negative electrode powder. The micron silicon cathode is a silicon cathode material with crystalline silicon occupying the main body, and the material also contains a three-dimensional network silicon oxide (SiOx) structure, wherein the silicon oxide structure can form lithium silicate and lithium oxide in the lithiation process, and the volume expansion of the crystalline silicon is restrained, so that the serious volume expansion problem of the crystalline silicon is avoided, the rapid attenuation of the capacity of a full battery is effectively restrained, and the high-efficiency long cycle of the battery is ensured. The preparation cost of the invention is low, and the invention can be produced in large scale.

Description

A micron silicon negative electrode and its application in sulfide all-solid-state batteries

Technical Field

The present invention relates to the technical field of all-solid-state batteries, and in particular to a micron silicon negative electrode and application thereof in a sulfide all-solid-state battery.

Background Art

As a potential "post-lithium" energy storage technology, sulfide all-solid-state batteries (ASSBs) have attracted widespread attention due to their potential high energy density, enhanced safety, long cycle life and wide temperature operability, and have broad prospects in electric vehicle applications. In order to further improve the energy density of sulfide all-solid-state batteries and promote their application, silicon anode materials with a theoretical specific capacity close to 10 times that of graphite (3759mA·h/g) have excellent application prospects. However, silicon materials undergo huge volume changes and subsequent cracking and crushing during the cycle process, which will have a negative impact on the long-term cycle stability of sulfide all-solid-state batteries. In order to overcome the capacity decay caused by mechanical degradation of silicon, people have tried to avoid the rapid decay of the full battery capacity by nano-sizing silicon or constructing carbon-composite silicon anodes. However, nano-sizing of silicon and carbon-composite silicon anodes will greatly increase the cost and greatly reduce the energy density. Therefore, it is urgent to obtain a low-cost, large-scale producible silicon anode that can effectively inhibit volume expansion and avoid rapid battery capacity decay, so as to further promote the development and application of sulfide all-solid-state batteries.

Summary of the invention

The purpose of the present invention is to provide a micron silicon negative electrode and its application in a sulfide all-solid-state battery to solve the problems existing in the above-mentioned prior art.

To achieve the above object, the present invention provides the following solutions:

One of the technical solutions of the present invention: a novel micron silicon negative electrode, the components of which are novel micron silicon negative electrode powder;

The method for preparing the novel micron silicon negative electrode powder comprises the following steps: placing crystalline silicon powder in a water vapor atmosphere for static oxidation to obtain the novel micron silicon negative electrode powder.

Furthermore, the particle size of the crystalline silicon powder is 1 to 5 μm;

The static oxidation time is 7 to 30 days.

Furthermore, the crystalline silicon powder is obtained by crushing large-sized crystalline silicon (greater than 40 μm) as raw material.

Using large-sized crystalline silicon as raw material for pulverization to obtain crystalline silicon powder can reduce costs and avoid the problem that the crystalline silicon powder has formed an oxide layer before use, which is not conducive to the static oxidation reaction.

Furthermore, the main components of the novel micron silicon negative electrode powder are crystalline silicon and SiOx (0＜x＜2).

The second technical solution of the present invention: an application of the above-mentioned new type of micron silicon negative electrode in a sulfide all-solid-state battery.

Technical solution three of the present invention: a method for preparing a sulfide all-solid-state battery, comprising the following steps:

(1) Under an argon atmosphere, the positive electrode active material and the sulfide electrolyte are ground evenly to obtain a composite positive electrode powder;

(2) pressing the sulfide electrolyte powder into a sheet to obtain an electrolyte sheet;

(3) spreading the composite cathode powder on the surface of the electrolyte sheet and applying pressure to obtain a composite cathode/electrolyte sheet;

(4) Spreading the micron silicon negative electrode powder according to any one of claims 1 to 3 on the other side of the electrolyte sheet, applying pressure, and obtaining a composite positive electrode/electrolyte/silicon negative electrode sheet;

(5) placing the composite positive electrode/electrolyte/silicon negative electrode sheet in a mold frame, applying stack pressure externally, and tightening screws to obtain the sulfide all-solid-state battery.

Furthermore, the raw materials for preparing the composite positive electrode powder include, by mass percentage: 60-80% of positive electrode active material and 20-40% of sulfide electrolyte;

The positive electrode active material includes NCM111, NCM424, NCM523, NCM622 or NCM811;

The sulfide electrolyte includes one or more of Li ₆ PS ₅ Cl, Li _5.5 PS _4.5 Cl _1.5 , Li ₆ PS ₅ Br, Li ₆ PS ₅ I, Li ₁₁ Si ₂ PS ₁₂ , Li ₁₀ Si _0.3 PS _6.7 Cl _1.8 , Li ₁₀ SnP ₂ S ₁₂ , Li ₁₀ GeP ₂ S ₁₂ , Li _3.25 Ge _0.25 P _0.75 S ₄ and Li _6.6 Ge _0.6 P _0.4 S ₅ I.

Furthermore, in step (2), the pressing pressure is 300-400 MPa;

In step (3), the pressure is 700-1000 MPa;

In step (4), the pressure is 300-400 MPa;

In step (5), the stack pressure is 400-500 MPa.

Furthermore, when the diameter of the sleeve mold for preparing the electrolyte sheet is 10 mm, the amount of the sulfide electrolyte powder used is 60 to 80 mg.

Technical solution four of the present invention: a sulfide all-solid-state battery prepared by the above preparation method.

The present invention places crystalline silicon powder in a water vapor atmosphere for static oxidation (design of silicon's own structure), so that oxygen is effectively doped into the silicon structure to form a crystalline silicon-silicon oxygen (SiOx) mixed structure (through corresponding characterization, it is found that SiOx is dispersed around the crystalline silicon clusters), thereby preparing a new type of micron silicon negative electrode material. The new type of micron silicon negative electrode material (structural composition: Si (crystal) and SiOx (amorphous) is different from the crystalline silicon (including single crystal silicon and polycrystalline silicon) and silicon oxide material system, especially different from silicon oxide material (silicon oxide material is amorphous, and its structural composition includes: Si (amorphous), _SiO2 (amorphous) and SiOx (amorphous) structure). Therefore, the new type of micron silicon negative electrode material of the present invention is a new type of silicon negative electrode material different from crystalline silicon and silicon oxide.

And through acid washing, it is known that the new micron silicon negative electrode material is mainly composed of crystalline silicon. The three-dimensional network silicon-oxygen structure in the material will form lithium silicate and lithium oxide during the lithiation process, which inhibits the volume expansion of crystalline silicon, thereby avoiding the serious volume expansion problem of crystalline silicon, effectively inhibiting the rapid attenuation of the full battery capacity, and ensuring the high efficiency and long cycle of the battery. And the preparation cost of the present invention is low and can be mass-produced.

The present invention discloses the following technical effects:

(1) The novel micron silicon negative electrode of the present invention has a simple preparation process, low price, and can be mass-produced.

(2) The novel micron silicon negative electrode of the present invention is applied to a sulfide all-solid-state battery to obtain a sulfide all-solid-state battery with excellent electrochemical properties.

(3) The dispersed three-dimensional network silicon-oxygen structure in the new micron silicon of the present invention can effectively inhibit the volume expansion of silicon during cycling and form a stable structure on the negative electrode side. In particular, when no conductive agent and sulfide electrolyte are added to the negative electrode side, the sulfide all-solid-state battery can also exhibit excellent cycle performance. Compared with commercial micron crystalline silicon-based sulfide all-solid-state batteries, the sulfide all-solid-state batteries prepared using the new micron silicon of the present invention exhibit longer cycle stability and the ability to resist lithium dendrite growth. Compared with commercial silicon oxide-based sulfide all-solid-state batteries, the sulfide all-solid-state batteries prepared using the new micron silicon of the present invention exhibit higher reversible capacity and can therefore provide higher energy density.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a scanning electron microscope (SEM) image of the novel micron silicon negative electrode powder prepared in Example 1 of the present invention;

FIG2 is an XRD diagram of the novel micron silicon negative electrode powder prepared in Example 1 of the present invention;

FIG3 is an experimental diagram of the determination of the proportion of crystalline silicon and silicon-oxygen structure (SiOx) in the novel micron silicon negative electrode powder prepared in Example 1 of the present invention;

FIG4 is a physical picture of a kilogram-level product of the novel micron silicon negative electrode powder prepared in Example 1 of the present invention;

FIG5 is a measurement result of the theoretical specific capacity of the novel micron silicon negative electrode powder prepared in Example 1 of the present invention;

FIG6 is a measurement result of the cycle performance of the sulfide all-solid-state battery prepared in Example 1 of the present invention;

FIG7 is a high resolution transmission electron microscope (HRTEM) image of the novel micron silicon negative electrode powder prepared in Example 2 of the present invention;

FIG8 is a measurement result of the cycle performance of the sulfide all-solid-state battery prepared in Example 2 of the present invention;

FIG9 is a cycle performance measurement result of the sulfide all-solid-state battery prepared in Comparative Example 1 of the present invention;

FIG10 is a graph showing the cycle performance measurement results of the sulfide all-solid-state battery prepared in Comparative Example 2 of the present invention.

DETAILED DESCRIPTION

Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

Example 1

A sulfide all-solid-state battery with a new micron silicon anode:

(1) Crush large-sized crystalline silicon (greater than 40 μm) into crystalline silicon powder (micron silicon powder) of 1 to 2 μm.

(2) The crystalline silicon powder is placed in a device filled with water vapor and allowed to oxidize for 15 days to obtain a new type of micron silicon negative electrode powder.

(3) In a glove box filled with argon, the positive electrode active material and the sulfide electrolyte (in terms of mass percentage, 70% of the positive electrode active material and 30% of the sulfide electrolyte) were ground evenly in a mortar to obtain a composite positive electrode powder.

Among them, the positive electrode active material is NCM811; the sulfide electrolyte is Li ₁₀ Si _0.3 PS _6.7 Cl _1.8 .

(4) 70 mg of the sulfide electrolyte powder was pressed into a tablet in a sleeve mold with a diameter of 10 mm (pressure of 350 MPa) to obtain a sulfide electrolyte tablet.

The sulfide electrolyte is Li ₁₀ Si _0.3 PS _6.7 Cl _1.8 .

(5) Spread 30 mg of the composite cathode powder on the surface of the pressed sulfide electrolyte sheet, apply a pressure of 900 MPa, and press it into a sheet to obtain a composite cathode/electrolyte sheet.

(6) 1.9 mg of the new micron silicon negative electrode powder was spread on the other side of the electrolyte sheet, and a pressure of 350 MPa was applied to press it into a sheet to obtain a composite positive electrode/electrolyte/silicon negative electrode sheet.

(7) Place the composite positive electrode/electrolyte/silicon negative electrode sheet in the mold frame, apply a stack pressure of 460 MPa on the outside, tighten the screws, and obtain a sulfide all-solid-state battery.

The scanning electron microscope (SEM) image of the novel micron silicon negative electrode powder prepared in this example is shown in FIG1 .

As can be seen from FIG. 1 , the novel micronized silicon prepared in this embodiment exhibits an irregular block morphology, and the particle size is about 1 to 2 μm.

The XRD pattern of the novel micron silicon negative electrode powder prepared in this example is shown in FIG2 .

As can be seen from Figure 2, compared with commercial silicon oxide materials and commercial crystalline silicon materials, the new micron silicon negative electrode is mainly crystalline silicon and also contains some amorphous silicon oxygen structure.

The ratio of crystalline silicon and silicon-oxygen structure (SiOx) in the new micron silicon negative electrode powder prepared in this embodiment was determined by weighing 1g of the new micron silicon negative electrode powder, removing the silicon-oxygen structure inside the material by HF pickling, and the mass of the remaining crystalline silicon after pickling was about 0.9g. The mass difference between the original powder and the remaining powder was the weight of the silicon-oxygen structure, which was about 0.1g. By calculation, the ratio of crystalline silicon to silicon-oxygen structure was 9:1, and the result is shown in Figure 3.

As can be seen from Figure 3, the main body of the new micron silicon negative electrode is crystalline silicon.

A physical picture of a kilogram-level product of the novel micron silicon negative electrode powder prepared in this embodiment is shown in FIG4 .

It can be seen from Figure 4 that the new micron silicon negative electrode powder can be produced on a large scale.

The novel micron silicon anode powder prepared in this example is assembled into a solid-state half-cell - silicon anode sheet/electrolyte/lithium sheet. The assembly method is the same as the assembly method of the above full cell. No assembly pressure is required on the lithium sheet side, and no stacking pressure is required for the entire half-cell. The theoretical specific capacity of the novel micron silicon anode is measured by fully discharging the half-cell at a low current. The results are shown in FIG5 .

It can be seen from Figure 5 that the theoretical specific capacity of the new micron silicon negative electrode is 2500mAh/g.

The cycle performance measurement results of the sulfide all-solid-state battery prepared in this example are shown in FIG6 .

As can be seen from FIG6 , the sulfide all-solid-state battery prepared in this embodiment exhibits very excellent cycle stability and has long cycle performance.

Example 2

A sulfide all-solid-state battery with a new micron silicon anode:

(1) Crush large-sized crystalline silicon blocks (greater than 40 μm) into crystalline silicon powder (micron silicon powder) of 1 to 2 μm.

(2) The crystalline silicon powder is placed in a device filled with water vapor and allowed to oxidize for 20 days to obtain a new type of micron silicon negative electrode powder.

(3) In a glove box filled with argon, the positive electrode active material and the sulfide electrolyte (in terms of mass percentage, 70% of the positive electrode active material and 30% of the sulfide electrolyte) were ground evenly in a mortar to obtain a composite positive electrode powder.

Among them, the positive electrode active material is NCM811; the sulfide electrolyte is Li ₆ PS ₅ Cl.

(4) 75 mg of the sulfide electrolyte powder was pressed into a tablet in a sleeve mold with a diameter of 10 mm (pressure of 380 MPa) to obtain a sulfide electrolyte tablet.

Among them, the sulfide electrolyte is Li ₆ PS ₅ Cl.

(5) 40 mg of the composite cathode powder was spread on the surface of the pressed sulfide electrolyte sheet, and a pressure of 1000 MPa was applied to press the sheet to obtain a composite cathode/electrolyte sheet.

(6) Spread 2.5 mg of the new micron silicon negative electrode powder on the other side of the electrolyte sheet, apply a pressure of 380 MPa, and press it into a sheet to obtain a composite positive electrode/electrolyte/silicon negative electrode sheet.

(7) Place the composite cathode/electrolyte/silicon anode sheet in a mold frame, apply a 480 MPa stacking pressure externally, tighten the screws, and obtain a sulfide all-solid-state battery.

A high-resolution transmission electron microscope (HRTEM) image of the novel micron silicon negative electrode powder prepared in this example is shown in FIG7 .

As can be seen from FIG. 7 , in the novel micron silicon prepared in this embodiment, the silicon oxygen (SiOx) structure is dispersed around the crystalline silicon.

The cycle performance measurement results of the sulfide all-solid-state battery prepared in this example are shown in FIG8 .

As can be seen from FIG. 8 , the sulfide all-solid-state battery prepared in this example still exhibits excellent long cycle performance at a commercial high surface capacity (4 mAh/cm ² ), and has commercial application value.

Comparative Example 1

Preparation of sulfide all-solid-state batteries:

(1) Commercially available 1-2 μm micron crystalline silicon powder is selected as the raw material for preparing the negative electrode.

(2) In a glove box filled with argon, the positive electrode active material and the sulfide electrolyte (in terms of mass percentage, 70% of the positive electrode active material and 30% of the sulfide electrolyte) were ground evenly in a mortar to obtain a composite positive electrode powder.

Among them, the positive electrode active material is NCM811; the sulfide electrolyte is Li ₁₀ Si _0.3 PS _6.7 Cl _1.8 .

(3) 70 mg of the sulfide electrolyte powder was pressed into a tablet in a sleeve mold with a diameter of 10 mm (pressure of 350 MPa) to obtain a sulfide electrolyte tablet.

The sulfide electrolyte is Li ₁₀ Si _0.3 PS _6.7 Cl _1.8 .

(4) Spread 30 mg of the composite cathode powder on the surface of the pressed sulfide electrolyte sheet, apply a pressure of 900 MPa, and press it into a sheet to obtain a composite cathode/electrolyte sheet.

(5) Sprinkle 1.9 mg of micron silicon powder on the other side of the electrolyte sheet, apply a pressure of 350 MPa, and press it into a sheet to obtain a composite positive electrode/electrolyte/silicon negative electrode sheet.

(6) Place the composite cathode/electrolyte/silicon anode sheet in a mold frame, apply a 460 MPa stack pressure externally, tighten the screws, and obtain a sulfide all-solid-state battery.

The cycle performance measurement results of the sulfide all-solid-state battery prepared in this comparative example are shown in FIG9 .

As can be seen from Figure 9, the capacity of the commercial sulfide all-solid-state battery made of micron-crystalline silicon decays rapidly, and the coulombic efficiency decreases during the cycle, which is caused by the growth of lithium dendrites leading to micro-short circuits.

Comparative Example 2

Preparation of sulfide all-solid-state batteries:

(1) Commercial silicon dioxide powder with a particle size of 1 to 2 μm was selected as the raw material for preparing the negative electrode.

(2) In a glove box filled with argon, the positive electrode active material and the sulfide electrolyte (in terms of mass percentage, 70% of the positive electrode active material and 30% of the sulfide electrolyte) were ground evenly in a mortar to obtain a composite positive electrode powder.

Among them, the positive electrode active material is NCM811; the sulfide electrolyte is Li ₁₀ Si _0.3 PS _6.7 Cl _1.8 .

(3) 70 mg of the sulfide electrolyte powder was pressed into a tablet in a sleeve mold with a diameter of 10 mm (pressure of 350 MPa) to obtain a sulfide electrolyte tablet.

The sulfide electrolyte is Li ₁₀ Si _0.3 PS _6.7 Cl _1.8 .

(4) Spread 30 mg of the composite cathode powder on the surface of the pressed sulfide electrolyte sheet, apply a pressure of 900 MPa, and press it into a sheet to obtain a composite cathode/electrolyte sheet.

(5) Sprinkle 1.9 mg of silicon dioxide powder on the other side of the electrolyte sheet, apply a pressure of 350 MPa, and press it into a sheet to obtain a composite positive electrode/electrolyte/silicon negative electrode sheet.

(6) Place the composite cathode/electrolyte/silicon anode sheet in a mold frame, apply a 460 MPa stack pressure externally, tighten the screws, and obtain a sulfide all-solid-state battery.

The cycle performance measurement results of the sulfide all-solid-state battery prepared in this comparative example are shown in FIG10 .

It can be seen from Figure 10 that compared with the sulfide all-solid-state battery assembled with the new micron silicon negative electrode, the sulfide all-solid-state battery prepared with silicon oxide negative electrode has lower capacity and worse performance.

The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims (8)

1. The micron silicon negative electrode is characterized by comprising the following components of micron silicon negative electrode powder;

The preparation method of the micron silicon negative electrode powder comprises the following steps: and standing and oxidizing the crystalline silicon powder in a water vapor atmosphere to obtain the micron silicon negative electrode powder.

2. The micron silicon negative electrode according to claim 1, wherein the particle diameter of the crystalline silicon powder is 1 to 5 μm;

the standing oxidation time is 7-30 days.

3. The micro silicon negative electrode according to claim 1, wherein the main components in the micro silicon negative electrode powder are crystalline silicon and SiOx.

4. Use of a microsilica anode as claimed in any one of claims 1 to 3 in a sulfide all-solid state battery.

5. A method for preparing an all-solid-state sulfide battery, comprising the steps of:

(1) Uniformly grinding the anode active material and sulfide electrolyte in an argon atmosphere to obtain composite anode powder;

(2) Pressing sulfide electrolyte powder into a tablet to obtain an electrolyte tablet;

(3) Spreading the composite anode powder on the surface of the electrolyte sheet, and applying pressure to obtain a composite anode/electrolyte sheet;

(4) Spreading the powder of the micron silicon negative electrode according to any one of claims 1-3 on the other side of the electrolyte sheet, and applying pressure to obtain a composite positive electrode/electrolyte/silicon negative electrode sheet;

(5) And placing the composite anode/electrolyte/silicon cathode sheet into a die frame, pressing outside Shi Jiadui, and screwing up a screw to obtain the sulfide all-solid-state battery.

6. The method for producing a sulfide all-solid state battery according to claim 5, wherein the raw materials for producing the composite positive electrode powder include, in mass percent: 60-80% of positive electrode active material and 20-40% of sulfide electrolyte;

the positive electrode active material includes NCM111, NCM424, NCM523, NCM622, or NCM811;

the sulfide electrolyte includes one or more of Li₆PS₅Cl、Li_5.5PS_4.5Cl_1.5、Li₆PS₅Br、Li₆PS₅I、Li₁₁Si₂PS₁₂、Li₁₀Si_0.3PS_6.7Cl_1.8、Li₁₀SnP₂S₁₂、Li₁₀GeP₂S₁₂、Li_3.25Ge_0.25P_0.75S₄ and Li _6.6Ge_0.6P_0.4S₅ I.

7. The method for producing a sulfide all-solid state battery according to claim 5, wherein in the step (2), the pressing pressure is 300 to 400MPa;

in the step (3), the pressure is 700-1000 MPa;

in the step (4), the pressure is 300-400 MPa;

In the step (5), the stacking pressure is 400-500 MPa.

8. An all-solid-state sulfide battery produced by the production method according to any one of claims 5 to 7.