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

Abstract

The present invention discloses a micron silicon negative electrode and its application in a sulfide all-solid-state battery, belonging to the technical field of all-solid-state batteries. The preparation components of the micron silicon negative electrode of the present invention are micron silicon negative electrode powder; the preparation method of the micron silicon negative electrode powder comprises the following steps: placing crystalline silicon powder in a water vapor atmosphere and allowing it to oxidize to obtain micron silicon negative electrode powder. The micron silicon negative electrode of the present invention is a silicon negative electrode material with crystalline silicon as the main body. The material also contains a three-dimensional network of silicon oxygen (SiOx) structure. The silicon oxygen structure 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. In addition, the preparation cost of the present invention is low and can be mass-produced.

Description

Technical Field

[0001] The present invention relates to the technical field of all-solid-state batteries, and in particular to a micron silicon negative electrode and its application in sulfide all-solid-state batteries. Background Art

[0002] 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, holding great promise for electric vehicle applications. To further improve the energy density of sulfide all-solid-state batteries and promote their application, silicon anode materials with a theoretical specific capacity nearly 10 times that of graphite (3759 mA·h / g) hold great promise. However, silicon materials undergo significant volume changes and subsequent cracking and pulverization during cycling, which negatively impacts the long-term cycling stability of sulfide all-solid-state batteries. To overcome the capacity decay caused by mechanical degradation of silicon, attempts have been made to nanoscale silicon or construct carbon-composite silicon anodes to prevent rapid capacity decay. However, nanoscaling and carbon-composite silicon anodes significantly increase cost and reduce energy density. Therefore, a low-cost, scalable silicon anode with effective volume expansion suppression and rapid capacity decay is urgently needed to further promote the development and application of sulfide all-solid-state batteries. Summary of the Invention

[0003] 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.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] 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;

[0006] The preparation method of the novel micron silicon negative electrode powder comprises the following steps: placing crystalline silicon powder in a water vapor atmosphere and allowing it to stand for oxidation to obtain the novel micron silicon negative electrode powder.

[0007] Furthermore, the particle size of the crystalline silicon powder is 1 to 5 μm;

[0008] The static oxidation time is 7 to 30 days.

[0009] Furthermore, the crystalline silicon powder is obtained by crushing large-sized crystalline silicon (greater than 40 μm) as raw material.

[0010] Using large-sized crystalline silicon as raw material for crushing to obtain crystalline silicon powder can reduce costs and avoid the problem of crystalline silicon powder forming an oxide layer before use, which is not conducive to the static oxidation reaction.

[0011] Furthermore, the main components of the novel micron silicon negative electrode powder are crystalline silicon and SiOx (0<x<2).

[0012] 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.

[0013] Technical solution three of the present invention: A method for preparing a sulfide all-solid-state battery, comprising the following steps:

[0014] (1) Under an argon atmosphere, the positive electrode active material and the sulfide electrolyte are ground uniformly to obtain a composite positive electrode powder;

[0015] (2) pressing the sulfide electrolyte powder into a sheet to obtain an electrolyte sheet;

[0016] (3) Spreading the composite cathode powder on the surface of the electrolyte sheet and applying pressure to obtain a composite cathode / electrolyte sheet;

[0017] (4) Spreading the micron silicon negative electrode powder on the other side of the electrolyte sheet and applying pressure to obtain a composite positive electrode / electrolyte / silicon negative electrode sheet;

[0018] (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.

[0019] Furthermore, the raw materials for preparing the composite positive electrode powder include, by mass percentage: 60-80% positive electrode active material and 20-40% sulfide electrolyte;

[0020] The positive electrode active material includes NCM111, NCM424, NCM523, NCM622 or NCM811;

[0021] The sulfide electrolyte includes Li6PS5Cl, Li 5.5 PS 4.5 Cl 1.5 、Li6PS5Br、Li6PS5I、Li 11 Si2PS 12 、Li 10 Si 0.3 PS 6.7 Cl 1.8 、Li 10 SnP2S 12 、Li 10GeP2S 12 、Li 3.25 Ge 0.25 P 0.75 S4 and Li 6.6 Ge 0.6 P 0.4 One or more of S5I.

[0022] Furthermore, in step (2), the pressing pressure is 300-400 MPa;

[0023] In step (3), the pressure is 700-1000 MPa;

[0024] In step (4), the pressure is 300-400 MPa;

[0025] In step (5), the stack pressure is 400-500 MPa.

[0026] 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 60-80 mg.

[0027] Technical solution four of the present invention: a sulfide all-solid-state battery prepared by the above preparation method.

[0028] The present invention prepares a novel micron silicon anode material by placing crystalline silicon powder in a water vapor atmosphere for static oxidation (design of the silicon's own structure), effectively doping oxygen into the silicon structure, forming a crystalline silicon-silicon oxygen (SiOx) blended structure (corresponding characterization revealed that SiOx is dispersed around crystalline silicon clusters). This novel micron silicon anode material (structurally composed of Si (crystalline) and SiOx (amorphous) is distinct from the crystalline silicon (including single crystal silicon and polycrystalline silicon) and silicon monoxide material systems, and is particularly different from silicon monoxide materials (silicon monoxide materials are amorphous, and their structural composition includes Si (amorphous), SiO2 (amorphous), and SiOx (amorphous) structures). Therefore, the novel micron silicon anode material of the present invention is a novel silicon anode material different from crystalline silicon and silicon monoxide.

[0029] Acid washing revealed that the new micron-silicon negative electrode material is primarily composed of crystalline silicon. The three-dimensional silicon-oxygen network in this material forms lithium silicate and lithium oxide during lithiation, suppressing the volume expansion of crystalline silicon. This prevents the severe volume expansion problem of crystalline silicon, effectively suppressing the rapid decay of the full battery capacity, and ensuring high efficiency and long battery cycle life. Furthermore, the present invention has low production costs and is suitable for large-scale production.

[0030] The present invention discloses the following technical effects:

[0031] (1) The preparation process of the novel micron silicon negative electrode of the present invention is simple, low-cost, and can be produced on a large scale.

[0032] (2) By applying the novel micron silicon negative electrode of the present invention to a sulfide all-solid-state battery, a sulfide all-solid-state battery with excellent electrochemical performance can be obtained.

[0033] (3) The dispersed three-dimensional network silicon-oxygen structure in the novel micron silicon of the present invention can effectively suppress the volume expansion of silicon during cycling, forming a stable structure on the negative electrode side. In particular, under the condition that no conductive agent and sulfide electrolyte are added to the negative electrode side, the sulfide all-solid-state battery can also show excellent cycling performance. Compared with commercial micron crystalline silicon-based sulfide all-solid-state batteries, the sulfide all-solid-state battery prepared by the novel micron silicon of the present invention shows longer cycling 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 battery prepared by the novel micron silicon of the present invention shows higher reversible capacity, and therefore can provide higher energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. 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 any creative work.

[0035] Figure 1 This is a scanning electron microscope (SEM) image of the novel micron silicon negative electrode powder prepared in Example 1 of the present invention;

[0036] Figure 2 This is the XRD pattern of the novel micron silicon negative electrode powder prepared in Example 1 of the present invention;

[0037] Figure 3 This is an experimental diagram for determining the proportions of crystalline silicon and silicon-oxygen structure (SiOx) in the novel micron silicon negative electrode powder prepared in Example 1 of the present invention;

[0038] Figure 4 This is a physical picture of a kilogram-level product of the new micron silicon negative electrode powder prepared in Example 1 of the present invention;

[0039] Figure 5 The results of measuring the theoretical specific capacity of the novel micron silicon negative electrode powder prepared in Example 1 of the present invention are as follows;

[0040] Figure 6 The cycle performance test results of the sulfide all-solid-state battery prepared in Example 1 of the present invention are as follows;

[0041] Figure 7This 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;

[0042] Figure 8 The cycle performance test results of the sulfide all-solid-state battery prepared in Example 2 of the present invention;

[0043] Figure 9 The cycle performance test results of the sulfide all-solid-state battery prepared in Comparative Example 1 of the present invention are as follows;

[0044] Figure 10 These are the cycle performance test results of the sulfide all-solid-state battery prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0045] 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 rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0046] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0047] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice 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 any conflict with any incorporated document, the contents of this specification shall prevail.

[0048] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0049] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0050] Example 1

[0051] A sulfide all-solid-state battery with a new micron-silicon anode:

[0052] (1) Crush large-sized crystalline silicon (greater than 40 μm) into crystalline silicon powder (micron silicon powder) of 1 to 2 μm.

[0053] (2) The crystalline silicon powder was 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.

[0054] (3) In an argon-filled glove box, 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.

[0055] Among them, the positive electrode active material is NCM811; the sulfide electrolyte is Li 10 Si 0.3 PS 6.7 Cl 1.8 .

[0056] (4) 70 mg of sulfide electrolyte powder was pressed into a sheet in a sleeve mold with a diameter of 10 mm (pressure of 350 MPa) to obtain a sulfide electrolyte sheet.

[0057] Among them, the sulfide electrolyte is Li 10 Si 0.3 PS 6.7 Cl 1.8 .

[0058] (5) Sprinkle 30 mg of 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.

[0059] (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.

[0060] (7) Place the composite cathode / electrolyte / silicon anode 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.

[0061] The scanning electron microscope (SEM) image of the new micron silicon negative electrode powder prepared in this embodiment is shown in FIG. Figure 1 .

[0062] from Figure 1 It can be seen from the figure that the new type of micron silicon prepared in this embodiment presents an irregular block morphology with a particle size of about 1 to 2 μm.

[0063] The XRD pattern of the new micron silicon negative electrode powder prepared in this embodiment is shown in FIG. Figure 2 .

[0064] from Figure 2 It can be seen that 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.

[0065] The ratio of crystalline silicon to 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 and removing the silicon-oxygen structure inside the material by HF pickling. The mass of the remaining crystalline silicon after pickling was approximately 0.9g. The mass difference between the original powder and the remaining powder was the weight of the silicon-oxygen structure, which was approximately 0.1g. By calculation, the ratio of crystalline silicon to silicon-oxygen structure was 9:1. The results are shown in Figure 2. Figure 3 .

[0066] from Figure 3 It can be seen that the main body of the new micron silicon negative electrode is crystalline silicon.

[0067] The physical picture of the kilogram-level product of the new micron silicon negative electrode powder prepared in this embodiment is shown in Figure 4 .

[0068] from Figure 4 It can be seen that the new micron silicon negative electrode powder can be produced on a large scale.

[0069] The new 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 full cell above. No assembly pressure is required on the lithium sheet side, and the entire half-cell does not need to be stacked. The theoretical specific capacity of the new micron silicon anode is measured by fully discharging the half-cell at a low current. The results are shown in Figure 2. Figure 5 .

[0070] from Figure 5 It can be seen that the theoretical specific capacity of the new micron silicon negative electrode is 2500mAh / g.

[0071] The cycle performance test results of the sulfide all-solid-state battery prepared in this example are shown in Figure 6 .

[0072] from Figure 6 It can be seen that the sulfide all-solid-state battery prepared in this embodiment exhibits very excellent cycle stability and has long cycle performance.

[0073] Example 2

[0074] A sulfide all-solid-state battery with a new micron-silicon anode:

[0075] (1) Crush large-sized crystalline silicon (greater than 40 μm) blocks into 1-2 μm crystalline silicon powder (micron silicon powder).

[0076] (2) The crystalline silicon powder was 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.

[0077] (3) In an argon-filled glove box, 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.

[0078] Among them, the positive electrode active material is NCM811; the sulfide electrolyte is Li6PS5Cl.

[0079] (4) 75 mg of 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.

[0080] Among them, the sulfide electrolyte is Li6PS5Cl.

[0081] (5) Sprinkle 40 mg of composite cathode powder on the surface of the pressed sulfide electrolyte sheet, apply a pressure of 1000 MPa, and press it into a sheet to obtain a composite cathode / electrolyte sheet.

[0082] (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.

[0083] (7) Place the composite cathode / electrolyte / silicon anode sheet in the mold frame, apply a 480 MPa stack pressure externally, and tighten the screws to obtain a sulfide all-solid-state battery.

[0084] The high resolution transmission electron microscope (HRTEM) image of the new micron silicon negative electrode powder prepared in this example is shown in FIG. Figure 7 .

[0085] from Figure 7 It can be seen from the figure that the silicon-oxygen (SiOx) structure in the novel micron silicon prepared in this embodiment is dispersed around the crystalline silicon.

[0086] The cycle performance test results of the sulfide all-solid-state battery prepared in this example are shown in Figure 8 .

[0087] from Figure 8 It can be seen that the sulfide all-solid-state battery prepared in this embodiment has a commercial high surface capacity (4 mAh / cm 2 ) still shows excellent long cycle performance and has commercial application value.

[0088] Comparative Example 1

[0089] Preparation of sulfide all-solid-state batteries:

[0090] (1) Commercially available 1-2 μm micron crystalline silicon powder was selected as the raw material for preparing the negative electrode.

[0091] (2) In an argon-filled glove box, 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 uniformly in a mortar to obtain a composite positive electrode powder.

[0092] Among them, the positive electrode active material is NCM811; the sulfide electrolyte is Li 10 Si 0.3 PS 6.7 Cl 1.8 .

[0093] (3) 70 mg of sulfide electrolyte powder was pressed into a sheet in a sleeve mold with a diameter of 10 mm (pressure of 350 MPa) to obtain a sulfide electrolyte sheet.

[0094] Among them, the sulfide electrolyte is Li 10 Si 0.3 PS 6.7 Cl 1.8 .

[0095] (4) Sprinkle 30 mg of 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.

[0096] (5) 1.9 mg of micron silicon powder was spread on the other side of the electrolyte sheet, and a pressure of 350 MPa was applied to press the sheet to obtain a composite positive electrode / electrolyte / silicon negative electrode sheet.

[0097] (6) Place the composite cathode / electrolyte / silicon anode 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.

[0098] The cycle performance test results of the sulfide all-solid-state battery prepared in this comparative example are shown in Figure 9 .

[0099] from Figure 9 It can be seen that the capacity of the sulfide all-solid-state battery prepared from commercial micron-crystalline silicon decays rapidly, and the coulombic efficiency decreases during the cycle. This is because the growth of lithium dendrites causes micro-short circuits.

[0100] Comparative Example 2

[0101] Preparation of sulfide all-solid-state batteries:

[0102] (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.

[0103] (2) In an argon-filled glove box, 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 uniformly in a mortar to obtain a composite positive electrode powder.

[0104] Among them, the positive electrode active material is NCM811; the sulfide electrolyte is Li 10 Si 0.3 PS 6.7 Cl 1.8 .

[0105] (3) 70 mg of sulfide electrolyte powder was pressed into a sheet in a sleeve mold with a diameter of 10 mm (pressure of 350 MPa) to obtain a sulfide electrolyte sheet.

[0106] Among them, the sulfide electrolyte is Li 10 Si 0.3 PS 6.7 Cl 1.8 .

[0107] (4) Sprinkle 30 mg of 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.

[0108] (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 into a sheet to obtain a composite positive electrode / electrolyte / silicon negative electrode sheet.

[0109] (6) Place the composite cathode / electrolyte / silicon anode 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.

[0110] The cycle performance test results of the sulfide all-solid-state battery prepared in this comparative example are shown in Figure 10 .

[0111] from Figure 10 It can be seen 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.

[0112] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A micron silicon negative electrode, characterized in that: The components are micron silicon negative electrode powder; The method for preparing the micron silicon negative electrode powder comprises the following steps: crushing a crystalline silicon block into crystalline silicon powder of 1 to 5 μm; placing the crystalline silicon powder in a water vapor atmosphere for static oxidation to obtain the micron silicon negative electrode powder; The static oxidation time is 7 to 30 days; The main components of the micron silicon negative electrode powder are crystalline silicon clusters and three-dimensional network SiOx, 0<x<2; The mass ratio of crystalline silicon to SiOx in the micron silicon negative electrode powder is 9:

1.

2. Use of the micron silicon negative electrode according to claim 1 in a sulfide all-solid-state battery.

3. A method for preparing a sulfide all-solid-state battery, characterized in that: The following steps are involved: (1) Under an argon atmosphere, the positive electrode active material and the sulfide electrolyte are ground uniformly 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 claim 1 on the other side of the electrolyte sheet and applying pressure to obtain 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.

4. The method for preparing a sulfide all-solid-state battery according to claim 3, wherein: 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 Li6PS5Cl, Li 5.5 PS 4.5 Cl 1.5 、Li6PS5Br、Li6PS5I、Li 11 Si2PS 12 、Li 10 Si 0.3 PS 6.7 Cl 1.8 、Li 10 SnP2S 12 、Li 10 GeP2S 12 、Li 3.25 Ge 0.25 P 0.75 S4 and Li 6.6 Ge 0.6 P 0.4 One or more of S5I.

5. The method for preparing a sulfide all-solid-state battery according to claim 3, wherein: 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.

6. A sulfide all-solid-state battery prepared by the preparation method according to any one of claims 3 to 5.

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