Negative electrode structure, preparation method thereof and all-solid-state battery

Abstract

The invention discloses a negative electrode structure, a preparation method thereof and an all-solid-state battery, and relates to the technical field of solid-state batteries. The negative electrode structure comprises a negative electrode current collector, a first active material layer and a second active material layer which are sequentially stacked, the first active material layer or the second active material layer is provided with a hollow channel, and the hollow channel penetrates through the first active material layer or the second active material layer. By designing the negative electrode structure, the technical problems that the volume change is large and microcracks are easily generated in the circulation process of the all-solid-state battery are solved.

Description

Technical Field

[0001] This application relates to the field of solid-state battery technology, and more specifically, to a negative electrode structure and its preparation method, and an all-solid-state battery. Background Technology

[0002] Solid-state batteries have attracted widespread attention due to their inherent safety and high energy density, particularly in applications such as electric vehicles and energy storage systems. However, a key challenge for all-solid-state batteries is the volume change of the negative electrode material during charge and discharge. When all-solid-state batteries use active materials without lithium storage capabilities as the negative electrode, the uneven deposition and difficulty in complete stripping of lithium ions during charge and discharge become particularly prominent. Uneven deposition and stripping of lithium ions in the negative electrode material cause significant volume expansion and contraction. This volume change generates mechanical stress within the electrode, leading to the formation of microcracks, which in turn affects the contact between the electrode material and the electrolyte, reducing interface stability. With increasing cycle count, these microcracks may further propagate, eventually causing the electrode structure to collapse, severely impacting the battery's cycle life and overall performance. Furthermore, the instability of the electrode structure can accelerate internal side reactions, such as electrolyte decomposition, thereby reducing battery efficiency and safety. Therefore, achieving uniform deposition and effective stripping of lithium ions in all-solid-state batteries while maintaining the stability and integrity of the electrode structure has become a critical issue that urgently needs to be addressed in the development of all-solid-state battery technology. Summary of the Invention

[0003] The main objective of this application is to provide a negative electrode structure and its preparation method, as well as an all-solid-state battery, to solve the technical problems of large volume changes and easy generation of microcracks in existing all-solid-state batteries during cycling.

[0004] To achieve the above objectives, according to a first aspect of this application, a negative electrode structure is provided, the negative electrode structure comprising a negative electrode current collector, a first active material layer and a second active material layer stacked sequentially; and the first active material layer or the second active material layer has a hollow channel that penetrates the first active material layer or the second active material layer.

[0005] Furthermore, the hollow channel is a hollow column or a hollow grid.

[0006] Furthermore, the hollow channel is a hollow column, and the negative electrode structure includes several parallel hollow columns. The hollow columns are cylindrical or rectangular, and the axial or height direction of the hollow columns is parallel to the thickness direction of the negative electrode current collector. When the hollow column is cylindrical, the diameter of the column is 0.001μm to 1000μm, and the radial distance between adjacent columns is 0.01μm to 100μm. When the hollow column is rectangular, the length and width of the rectangular column are each independently 0.001μm to 1000μm, and the distance between adjacent rectangular columns is 0.01μm to 100μm.

[0007] Furthermore, the hollow channel is a hollow grid, which includes several hollow vertical bars and several hollow horizontal bars. The length direction of the hollow vertical bars and hollow horizontal bars is perpendicular to the thickness direction of the negative electrode current collector. The hollow vertical bars and hollow horizontal bars intersect each other to form several grids. The width of each hollow vertical bar and hollow horizontal bar is independently 0.001μm~1000μm, and the spacing between adjacent hollow horizontal bars or adjacent hollow vertical bars is independently 0.01μm~100μm.

[0008] Furthermore, the first active material layer has a hollow channel, and the thickness ratio of the first active material layer to the second active material layer is (1~100):1.

[0009] Furthermore, the first active material layer includes a first active material, and the second active material layer includes a second active material; the first active material and the second active material may be the same or different; the first active material and the second active material each independently include at least one of carbon material and metal material.

[0010] Furthermore, the carbon material is at least one of crystalline carbon, amorphous carbon, and modified carbon; wherein the modified carbon includes a doping element, and the doping element includes at least one of nitrogen, fluorine, boron, phosphorus, and sulfur.

[0011] Furthermore, the metallic material is at least one of gold, silver, aluminum, magnesium, zinc, copper, nickel, titanium, iron, tungsten, scandium, tin, germanium, manganese, cobalt, and antimony.

[0012] Furthermore, both the first and second active materials include carbon materials and metal materials, and the mass ratio of carbon materials to metal materials is independently 1:(0.01~100).

[0013] Furthermore, both the first active material and the second active material include carbon materials and metal materials, and the average particle size of the carbon materials is 0.01 μm to 1 μm, the average particle size of the metal materials is 0.01 μm to 1 μm, and the ratio of the average particle size of the carbon materials to the metal materials is 1:(0.01 to 100).

[0014] According to a second aspect of this application, a method for preparing the negative electrode structure of the first aspect of this application is provided, comprising the following steps:

[0015] S1, preparing the first slurry and the second slurry;

[0016] S2, the first slurry is printed onto the surface of the negative electrode current collector according to the set morphology, and dried to obtain the first active material layer;

[0017] S3. The second slurry is printed onto the surface of the first active material layer according to the set morphology, and then dried to obtain the second active material layer, which is the negative electrode structure.

[0018] According to a third aspect of this application, an all-solid-state battery is provided, comprising a negative electrode, a solid electrolyte layer, and a positive electrode layer stacked sequentially, wherein the negative electrode comprises the negative electrode structure of the first aspect of this application or the negative electrode structure prepared by the preparation method of the second aspect of this application; the positive electrode comprises a positive current collector and a positive active material layer stacked sequentially, and the positive current collector is located away from the solid electrolyte layer.

[0019] Furthermore, the positive electrode active material layer includes a positive electrode active material, which includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide, and lithium nickel manganese oxide.

[0020] Furthermore, the solid electrolyte layer includes a solid electrolyte, which includes a sulfide solid electrolyte.

[0021] By applying the technical solution in this application, hollow channels are designed in the first active material layer or the second active material layer. Lithium ions can be uniformly deposited in these channels during charging, which helps to avoid the formation of lithium dendrites. Furthermore, the hollow channels help to slow down the volume change inside the negative electrode during charging and discharging, improve the structural stability of the negative electrode, and thus help to improve the cycle stability of the all-solid-state battery. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of an all-solid-state battery according to one embodiment of this application;

[0023] Figure 2 This is a schematic diagram of the hollow channel structure in one embodiment of this application;

[0024] Figure 3 This is a schematic diagram of the hollow channel structure in one embodiment of this application;

[0025] Figure 4 The electrochemical performance test diagram shows the all-solid-state battery prepared by the negative electrode structure in Example 1 of this application.

[0026] Figure 5The electrochemical performance test diagram shows the all-solid-state battery prepared by the negative electrode structure in Comparative Example 1 of this application.

[0027] Figure 6 The electrochemical performance test diagram shows the all-solid-state battery prepared by the negative electrode structure in Comparative Example 2 of this application.

[0028] Figure 7 The electrochemical performance test diagram shows the all-solid-state battery prepared by the negative electrode structure in Comparative Example 3 of this application.

[0029] The above figures contain the following reference numerals:

[0030] 10. Negative electrode sheet; 11. Negative electrode current collector; 12. First active material layer; 13. Second active material layer; 14. Hollow channel; 20. Solid electrolyte layer; 30. Positive electrode sheet; 31. Positive electrode current collector; 32. Positive electrode active material layer. Detailed Implementation

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0033] In this invention, unless otherwise stated, directional terms such as "up" and "down" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction; similarly, for ease of understanding and description, "left" and "right" are generally used in relation to the left and right shown in the accompanying drawings; "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0034] As described in the background section of this application, existing technologies suffer from poor structural stability during the cycling process of all-solid-state batteries. To address this issue, in a typical embodiment of this application, an all-solid-state battery is provided, the structural schematic of which is shown below. Figure 1 As shown, it includes a negative electrode 10, a solid electrolyte layer 20, and a positive electrode 30 stacked in sequence; wherein, the negative electrode 10 includes a special negative electrode structure, which includes a negative electrode current collector 11, a first active material layer 12, and a second active material layer 13 stacked in sequence; and the first active material layer 12 or the second active material layer 13 has a hollow channel 14, which penetrates the first active material layer 12 or the second active material layer 13.

[0035] By designing hollow channels 14 in the first active material layer 12 or the second active material layer 13, lithium ions can be uniformly deposited within these channels during charging, rather than just deposited on the material surface or in specific areas. This effectively avoids the formation of lithium dendrites, sharp lithium metal structures caused by uneven deposition of lithium ions on the negative electrode surface, which can pierce the electrolyte and cause internal short circuits in the battery. Simultaneously, the presence of hollow channels 14 provides a clear path for lithium ions during discharge, ensuring complete stripping of lithium ions and reducing the phenomenon of "dead lithium," where lithium ions cannot participate in subsequent charge-discharge cycles, thereby improving the overall cycle performance of the battery. Furthermore, the presence of hollow channels 14 helps to mitigate volume expansion and contraction during charging and discharging, reducing the mechanical stress generated internally during battery cycling. This stress relief effect helps maintain the integrity and stability of the negative electrode, preventing the formation of microcracks, thus improving the cycle performance of the all-solid-state battery.

[0036] In some implementations, the hollow channel 14 is a hollow column or a hollow grid.

[0037] Hollow pillars or hollow grids provide a three-dimensional distribution and storage platform for lithium ions. These structures guide lithium ions to deposit uniformly along their internal pathways, preventing localized high-concentration lithium deposition and thus reducing lithium dendrite formation, thereby improving battery safety and cycle stability. Furthermore, compared to solid structures, hollow structures offer higher structural toughness with the same material usage. This structure better accommodates volume changes during lithium deposition and stripping, reducing internal stress, preventing microcrack formation, and improving the structural stability of all-solid-state batteries during charge-discharge cycles, thereby extending battery life. In addition, hollow pillar or grid structures provide a larger specific surface area, facilitating rapid heat dissipation within the battery, which further enhances the safety of all-solid-state batteries.

[0038] In some embodiments, the hollow channel 14 is a hollow column, such as... Figure 2 As shown, the negative electrode structure includes several parallel hollow columns, which are cylindrical or rectangular, and the axial or height direction of the hollow columns is parallel to the thickness direction of the negative electrode current collector. When the hollow column is cylindrical, the diameter of the column is 0.001μm to 1000μm, preferably 0.01μm to 1000μm, and the radial distance between adjacent columns is 0.01μm to 100μm. When the hollow column is rectangular, the length and width of the rectangular column are each independently 0.001μm to 1000μm, preferably 0.01μm to 1000μm, and the distance between adjacent rectangular columns is 0.01μm to 100μm.

[0039] By incorporating several hollow pillars in the negative electrode structure, their regular geometry helps guide lithium ions to distribute and deposit uniformly along the pillar channels during charging and discharging. This uniformity reduces lithium dendrite formation and improves the battery's cycle stability and safety. Furthermore, lithium ions can be deposited and stripped through the sidewalls of these pillar channels, not just the top or bottom, further optimizing lithium ion storage and transport efficiency. Controlling the size and distribution of the hollow pillars helps balance the structural stability and lithium ion transport rate of the all-solid-state battery, improving its cycle stability and specific capacity.

[0040] In some embodiments, the hollow channel 14 is a hollow mesh, such as Figure 3 As shown, the hollow grid includes several hollow vertical bars and several hollow horizontal bars. The length direction of the hollow vertical bars and hollow horizontal bars is perpendicular to the thickness direction of the negative electrode current collector 11. The hollow vertical bars and hollow horizontal bars intersect each other to form several grids. The width of each hollow vertical bar and hollow horizontal bar is independently 0.001μm~1000μm, and the spacing between adjacent hollow horizontal bars or adjacent hollow vertical bars is independently 0.01μm~100μm.

[0041] The hollow grid structure, through the intersection of hollow vertical and horizontal bars, provides multi-dimensional transport paths for lithium ions, enhancing their diffusion capabilities in the first and second active material layers 12 and 13. This multi-path transport mode reduces resistance to lithium ion transport, improves transport efficiency during charging and discharging, and thus enhances the battery's power density and fast-charging performance. The grid structure provides a uniform deposition site for lithium ions, preventing excessively high local concentrations on the surface of the active material layers and effectively suppressing lithium dendrite formation. Simultaneously, the presence of hollow horizontal and vertical bars facilitates uniform stripping of lithium ions during discharge, reducing the generation of "dead lithium" and improving the battery's cycle stability. Furthermore, this structural design significantly reduces internal stress caused by volume changes within the negative electrode during charging and discharging, effectively mitigating the formation of microcracks within the material and further enhancing the structural stability of the all-solid-state battery during cycling.

[0042] In some embodiments, the first active material layer 12 has a hollow channel 14, and the thickness ratio of the first active material layer 12 to the second active material layer 13 is (1~100):1.

[0043] By incorporating hollow channels 14 within the first active material layer 12, the lithium-ion storage performance is significantly improved, the uniformity of lithium deposition is enhanced, and the expansion stress during cycling is reduced, thereby contributing to improved cycle stability of the all-solid-state battery. Further adjustment of the thickness ratio between the first active material layer 12 and the second active material layer 13 helps promote uniform lithium-ion deposition and stripping, alleviates volume transformation, improves the stability of the negative electrode structure, and optimizes thermal management, thus contributing to improved overall electrochemical performance and lifespan of the all-solid-state battery.

[0044] In some embodiments, the first active material layer 12 includes a first active material, and the second active material layer 13 includes a second active material; the first active material and the second active material may be the same or different; the first active material and the second active material each independently include at least one of carbon material and metal material.

[0045] The types of primary and secondary active materials can be flexibly selected according to different operating conditions and performance requirements of all-solid-state batteries. For example, carbon materials usually have high conductivity and stable chemical properties, making them suitable as conductive frameworks in batteries, while metal materials can provide higher theoretical capacity or faster ion transport rates in certain situations. Therefore, they can be optimized and combined as needed to meet specific performance indicators.

[0046] Specifically, but not limitingly, the carbon materials include crystalline carbon and amorphous carbon (e.g., Kejen black, acetylene black, Asahi C, Super p-Li, Ensaco). TM The modified carbon comprises at least one of Cabot C45 and C65, etc.; wherein the modified carbon includes a doping element, and the doping element includes at least one of nitrogen, fluorine, boron, phosphorus and sulfur.

[0047] Specifically, but not limitingly, the metallic material is at least one of the following: gold, silver, aluminum, magnesium, zinc, copper, nickel, titanium, iron, tungsten, scandium, tin, germanium, manganese, cobalt, and antimony.

[0048] In some embodiments, both the first active material and the second active material include carbon materials and metal materials, and the mass ratio of carbon materials to metal materials in the first active material and the second active material is independently 1:(0.01~100).

[0049] Carbon materials, with their excellent electronic conductivity, good chemical stability, and porous structure, can serve as efficient conductive networks and platforms for lithium-ion transport, while also providing additional mechanical strength and toughness. Metallic materials typically possess higher theoretical capacities and faster ion diffusion coefficients, significantly improving the energy density and power characteristics of batteries. Combining the advantages of both materials allows for complementary electrode performance, enhancing the overall efficiency of the battery.

[0050] In some embodiments, both the first active material and the second active material include carbon material and metal material, and the average particle size of the carbon material is 0.01 μm to 1 μm, the average particle size of the metal material is 0.01 μm to 1 μm, and the ratio of the average particle size of the carbon material to the average particle size of the metal material is 1:(0.01 to 100).

[0051] Controlling the average particle size of carbon and metallic materials within the aforementioned range shortens the diffusion path of lithium ions in the negative electrode, accelerates the lithium ion diffusion process, and thus improves the battery's charge / discharge rate and power density. Furthermore, controlling the particle size within this range also helps increase the specific surface area of ​​the material, providing more active sites, promoting electrochemical reactions, and further improving the battery's capacity and energy density.

[0052] In another typical embodiment of this application, a method for preparing the negative electrode structure described above is provided, comprising the following steps:

[0053] S1, preparing the first slurry and the second slurry;

[0054] S2, the first slurry is printed onto the surface of the negative electrode current collector according to the set morphology, and dried to obtain the first active material layer;

[0055] S3. The second slurry is printed onto the surface of the first active material layer according to the set morphology, and then dried to obtain the second active material layer, which is the negative electrode structure.

[0056] The above preparation method is simple and can be used to print the paste using methods such as 3D printing, inkjet printing, and screen printing.

[0057] In some embodiments, the first slurry includes a first active material and a first binder; the second slurry includes a second active material and a second binder. The first and second active materials are each independently at least one of a carbon material and a metallic material; the first and second binders are each independently at least one of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), and polyacrylic acid (PAA); and the mass ratio of the first active material to the first binder and the mass ratio of the second active material to the second binder are each independently (1~100):1. Using the above-described first and second slurries helps to prepare a first and second active material layer with high structural stability.

[0058] In some embodiments of this application, the negative electrode current collector 11 includes common negative electrode current collectors such as copper foil and stainless steel foil.

[0059] In some embodiments of this application, the positive electrode 30 includes a positive current collector 31 and a positive active material layer 32 stacked sequentially, wherein the positive current collector 31 is located away from the solid electrolyte layer 20; in addition, the negative current collector 11 in the negative electrode 10 is located away from the solid electrolyte layer 20.

[0060] In some embodiments, the positive electrode active material layer 32 includes a positive electrode active material, which includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide, and lithium nickel manganese oxide.

[0061] Lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium nickel manganese oxide, due to their high potential and high capacity characteristics, can significantly improve the overall energy density of batteries, thus making them suitable for applications requiring high energy output, such as electric vehicles; lithium iron phosphate has good cycle stability due to its stable olivine structure; lithium manganese oxide has a high operating potential and good thermal stability, which helps to improve battery safety.

[0062] In some embodiments, the solid electrolyte layer 20 includes a solid electrolyte, which includes a sulfide solid electrolyte; specifically, but not limitingly, the sulfide solid electrolyte includes Li 3.25 Ge 0.25 P 0.7 S4, Li 10 GeP2S 12 It is at least one of Li6PS5X, and X is at least one of Cl, Br, and I.

[0063] Sulfide solid electrolytes possess a wide electrochemical window, enabling them to operate stably at higher voltages without decomposition. This is crucial for improving the energy density and cycle stability of all-solid-state batteries. Furthermore, sulfide solid electrolytes exhibit good ionic conductivity, which contributes to increasing the battery's power density.

[0064] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0065] Example 1

[0066] One embodiment of the negative electrode structure of this application, the preparation method of the negative electrode structure described in this embodiment is as follows:

[0067] S1, weigh Cabot C45 (average particle size 0.05 μm), silver (average particle size 0.06 μm), PVDF and N-methylpyrrolidone (NMP) in a mass ratio of 4:1:1:45 to prepare a slurry;

[0068] S2, Take a portion of the slurry and use 3D printing technology to print a first negative electrode active material region with a columnar structure on the copper foil (10μm thick) of the negative electrode current collector 11. The linear distance between the columns is 3μm, and the columns are rectangular with a length and width of 0.5μm and 0.4μm, respectively. After drying, a first active material layer 12 with hollow mesh-type hollow channels 14 is formed. Its structural schematic diagram is shown below. Figure 3 As shown;

[0069] S3, take a portion of the slurry, use 3D printing technology to form a second active material region on the surface of the first active material layer, dry it, and obtain the second active material layer 13, thereby obtaining the negative electrode structure described in this embodiment;

[0070] In this embodiment, the thickness ratio of the first active material layer 12 to the second active material layer 13 in the negative electrode structure is 4:1, and the thickness of the negative electrode structure is 25 μm.

[0071] Example 2

[0072] One embodiment of the negative electrode structure of this application, the preparation method of the negative electrode structure described in this embodiment is as follows:

[0073] S1, weigh Cabot C45 (average particle size 0.05μm), silver (average particle size 0.06μm), PVDF and NMP in a mass ratio of 4:1:1:45 to prepare a slurry;

[0074] S2, Take a portion of the slurry and use 3D printing technology to print a first negative electrode active material region with a grid structure on the copper foil (10μm thick) of the negative electrode current collector 11. This first negative electrode active material region includes horizontal and vertical strips, which intersect to form a grid. The width and length of the grid are 3μm and 5μm, respectively, and the width of the horizontal and vertical strips is 0.5μm. After drying, a first active material layer 12 with hollow columnar hollow channels 14 is formed. Its structural schematic diagram is shown below. Figure 2 As shown;

[0075] S3, take a portion of the slurry, use 3D printing technology to form a second active material region on the surface of the first active material layer, dry it, and obtain the second active material layer 13, thereby obtaining the negative electrode structure described in this embodiment;

[0076] In this embodiment, the thickness ratio of the first active material layer 12 to the second active material layer 13 in the negative electrode structure is 4:1, and the thickness of the negative electrode structure is 25 μm.

[0077] Example 3

[0078] One embodiment of the negative electrode structure of this application differs from that of Embodiment 1 only in that the thickness ratio of the first active material layer 12 and the second active material layer 13 is 1:1, and the thickness of the negative electrode structure is 40 μm.

[0079] Example 4

[0080] One embodiment of the negative electrode structure of this application differs from that of Embodiment 1 only in that the thickness ratio of the first active material layer 12 to the second active material layer 13 is 100:1, and the thickness of the negative electrode structure is 20.2 μm.

[0081] Example 5

[0082] One embodiment of the negative electrode structure of this application differs from that of Embodiment 1 only in that the thickness ratio of the first active material layer 12 to the second active material layer 13 is 0.5:1, and the thickness of the negative electrode structure is 60 μm.

[0083] Example 6

[0084] One embodiment of the negative electrode structure of this application differs from that of Embodiment 1 only in that the thickness ratio of the first active material layer 12 to the second active material layer 13 is 150:1, and the thickness of the negative electrode structure is 20.13 μm.

[0085] Example 7

[0086] One embodiment of the negative electrode structure of this application differs from that of embodiment 1 only in that, in S2, the straight-line distance between the columns is 1 μm.

[0087] Example 8

[0088] One embodiment of the negative electrode structure of this application differs from that of embodiment 1 only in that, in S2, the straight-line distance between the pillars is 5 μm.

[0089] Example 9

[0090] One embodiment of the negative electrode structure of this application differs from that of embodiment 1 only in that, in S2, the straight-line distance between the columns is 0.001 μm.

[0091] Example 10

[0092] One embodiment of the negative electrode structure of this application differs from that of embodiment 1 only in that, in S2, the straight-line distance between the columns is 150 μm.

[0093] Comparative Example 1

[0094] One comparative example of the negative electrode structure of this application, and the preparation method of the negative electrode structure described in this comparative example is as follows:

[0095] S1, weigh Cabot C45 (average particle size 0.05μm), silver (average particle size 0.06μm), PVDF and NMP in a mass ratio of 4:1:1:45 to prepare a slurry;

[0096] S2, take a portion of the slurry and use 3D printing technology to print a first negative electrode active material region with a grid structure on the copper foil (thickness of 10μm) of the negative electrode current collector 11. The first negative electrode active material region includes horizontal and vertical strips, which intersect to form a grid. The width and length of the grid are 3μm and 5μm, respectively, and the width of the horizontal and vertical strips is 0.5μm. After drying, a first active material layer 12 with hollow column-shaped hollow channels 14 is formed, which is the negative electrode structure. The thickness of the negative electrode structure is 20μm.

[0097] Comparative Example 2

[0098] One comparative example of the negative electrode structure of this application, and the preparation method of the negative electrode structure described in this comparative example is as follows:

[0099] S1, weigh Cabot C45 (average particle size 0.05 μm), silver (average particle size 0.06 μm), PVDF and N-methylpyrrolidone (NMP) in a mass ratio of 4:1:1:45 to prepare a slurry;

[0100] S2, take a portion of the slurry and use 3D printing technology to print a first negative electrode active material region with a columnar structure on the copper foil (thickness of 10μm) of the negative electrode current collector 11. The straight-line distance between the columns is 3μm, and the columns are rectangular columns with a length and width of 0.5μm and 0.4μm, respectively. After drying, a first active material layer 12 with hollow mesh-type hollow channels 14 is formed, which is the negative electrode structure. The thickness of the negative electrode structure is 20μm.

[0101] Comparative Example 3

[0102] One comparative example of the negative electrode structure of this application, and the preparation method of the negative electrode structure described in this comparative example is as follows:

[0103] S1, weigh Cabot C45 (average particle size 0.05μm), silver (average particle size 0.06μm), PVDF and NMP in a mass ratio of 4:1:1:45 to prepare a slurry;

[0104] S2, the slurry is coated on copper foil (10 μm thick) to obtain a negative electrode structure with a thickness of 25 μm.

[0105] The negative electrode structure in the examples and comparative examples is used as the negative electrode sheet 10, which, together with the solid electrolyte layer 20 and the positive electrode sheet 30, forms an all-solid-state battery. The specific preparation process of the positive electrode sheet 30 is as follows: A ternary positive electrode material, lithium nickel cobalt manganese oxide (NCM811), is used as the positive electrode active material. It is mixed with conductive carbon black (a conductive agent), sulfide electrolyte Li6PS5Cl, and binder polyvinyl alcohol in a mass ratio of 85:2:10:3. Using NMP as a solvent, the mixture is coated onto aluminum foil to obtain a positive electrode sheet with a thickness of 600 μm. The solid electrolyte layer 20 has… The solid electrolyte preparation process includes: weighing Li6PS5Cl electrolyte (average particle size of 6μm), SEBS binder and p-xylene solvent in a mass ratio of 24:1:35 to prepare an electrolyte slurry, coating it with a thickness of 500μm on a polyethylene terephthalate (PET) plate to obtain a solid electrolyte layer 20; bonding the side of the positive electrode coated with the positive electrode active material to the solid electrolyte layer 20, and bonding the active material layer in the negative electrode sheet 10 to the surface of the solid electrolyte away from the positive electrode to obtain an all-solid-state battery.

[0106] Performance testing

[0107] The performance of all-solid-state batteries prepared using the negative electrode structures in the examples and comparative examples was tested. The test methods are as follows, and the test results are shown in Table 1. Figures 4-7 As shown.

[0108] Discharge specific capacity and capacity retention rate of all-solid-state batteries after 50 cycles at 0.5C: The batteries were placed in a stainless steel test fixture and tested at 0.5C rate with a voltage range of 2.5V-4.25V. The discharge specific capacity and capacity retention rate after 50 cycles were recorded.

[0109] Table 1

[0110]

[0111] From Table 1 and Figures 4-7 It can be seen that the all-solid-state battery including the negative electrode structure in the embodiments of this application has good cycle stability. Its capacity retention rate after 50 cycles is still above 62%, and the discharge specific capacity is higher than 121 mAh / g, demonstrating good comprehensive electrochemical performance. In Comparative Examples 1 and 2, when the second active material layer 13 is not included, during the charging process, the lithium deposited in the cavity of the first active material layer 12 comes into direct contact with the sulfide electrolyte at the negative electrode interface, which easily leads to electrolyte decomposition. Therefore, its cycle stability is poor. In Comparative Example 3, when the negative electrode structure does not include the hollow channel 14, the lack of a lithium storage space causes the battery volume to expand and contract, and the internal stress of the battery cannot be released. Therefore, its cycle performance is also significantly worse.

[0112] In addition, comparing the performance test results of Examples 1 to 6, it can be found that when the thickness ratio of the first active material layer 12 to the second active material layer 13 is (1 to 100): 1, the overall electrochemical performance is better.

[0113] In addition, comparing the performance test results of Examples 7 to 10, it can be found that when the active material is designed as rectangular pillars, and the spacing between adjacent rectangular pillars is 0.01μm to 100μm, the all-solid-state battery has better cycle performance, and its discharge specific capacity and capacity retention are significantly higher.

[0114] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A negative electrode structure characterized by comprising: The negative electrode structure comprises a negative electrode current collector (11), a first active material layer (12), and a second active material layer (13) which are sequentially stacked; and the first active material layer (12) or the second active material layer (13) has a hollow channel (14) which penetrates through the first active material layer (12) or the second active material layer (13).

2. The negative electrode structure according to claim 1, characterized by The hollow channel (14) is a hollow column or a hollow grid.

3. The negative electrode structure according to claim 2, characterized by The hollow channel (14) is a hollow column, the negative electrode structure comprises a plurality of hollow columns which are arranged in parallel, the hollow column is a cylindrical column or a rectangular column, and the axial direction or the height direction of the hollow column is parallel to the thickness direction of the negative electrode current collector (11); when the hollow column is a cylindrical column, the diameter of the cylindrical column is 0.001 μm to 1000 μm, and the radial spacing between adjacent cylindrical columns is 0.01 μm to 100 μm; when the hollow column is a rectangular column, the length and the width of the rectangular column are each independently 0.001 μm to 1000 μm, and the spacing between adjacent rectangular columns is 0.01 μm to 100 μm.

4. The negative electrode structure according to claim 2, wherein The hollow channel (14) is a hollow grid, the hollow grid comprises a plurality of hollow vertical bars and a plurality of hollow horizontal bars, the length direction of the hollow vertical bars and the hollow horizontal bars is perpendicular to the thickness direction of the negative electrode current collector (11), and the hollow vertical bars and the hollow horizontal bars cross each other to form a plurality of grids; the width of the hollow vertical bars and the hollow horizontal bars is each independently 0.001 μm to 1000 μm, and the spacing between adjacent hollow horizontal bars or adjacent hollow vertical bars is each independently 0.01 μm to 100 μm.

5. The negative electrode structure according to any one of claims 1 to 4, wherein The first active material layer (12) has the hollow channel (14), and the thickness ratio of the first active material layer (12) to the second active material layer (13) is (1 to 100):

1.

6. The negative electrode structure according to claim 1, wherein The first active material layer (12) comprises a first active material, and the second active material layer (13) comprises a second active material; the first active material and the second active material are the same or different; and the first active material and the second active material each independently comprise at least one of a carbon material and a metal material.

7. The negative electrode structure according to claim 6, wherein At least one of the following conditions is met: (1) the carbon material is at least one of crystalline carbon, amorphous carbon, and modified carbon; wherein the modified carbon comprises a doping element, and the doping element comprises at least one of a nitrogen element, a fluorine element, a boron element, a phosphorus element, and a sulfur element; (2) the metal material is at least one of gold, silver, aluminum, magnesium, zinc, copper, nickel, titanium, iron, tungsten, scandium, tin, germanium, manganese, cobalt, and antimony; (3) the first active material and the second active material each independently comprise a carbon material and a metal material, and the mass ratio of the carbon material to the metal material is each independently 1: (0.01 to 100). (4) the first active material and the second active material each comprise a carbon material and a metal material, the average particle size of the carbon material is 0.01-1 μm, the average particle size of the metal material is 0.01-1 μm, and the ratio of the average particle sizes of the carbon material and the metal material is 1:(0.01-100).

8. A method for producing the negative electrode structure according to any one of claims 1 to 7, characterized by, The method comprises the following steps: S1, preparing a first slurry and a second slurry; S2, printing the first slurry onto the surface of the negative current collector according to a set morphology, and drying to obtain a first active material layer; S3, printing the second slurry onto the surface of the first active material layer according to a set morphology, and drying to obtain a second active material layer, i.e. to obtain the negative electrode structure.

9. An all-solid battery, characterized by, The all-solid-state battery comprises a negative electrode sheet (10), a solid-state electrolyte layer (20), and a positive electrode sheet (30) which are sequentially stacked, the negative electrode sheet (10) comprises the negative electrode structure according to any one of claims 1-7 or the negative electrode structure prepared by the preparation method according to claim 8; the positive electrode sheet (30) comprises a positive electrode current collector (31) and a positive electrode active material layer (32) which are sequentially stacked; and the positive electrode current collector (31) is away from the solid-state electrolyte layer (20).

10. The all-solid battery according to claim 9, characterized by, At least one of the following conditions is met: (1) the positive electrode active material layer (32) comprises a positive electrode active material, and the positive electrode active material comprises at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide, and lithium nickel manganese oxide; (2) the solid-state electrolyte layer (20) comprises a solid-state electrolyte, and the solid-state electrolyte comprises a sulfide solid-state electrolyte.

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