Pole piece with unfoamed rubber frame, preparation method thereof, and all-solid-state battery cell and preparation method thereof

Abstract

The application belongs to the technical field of batteries and relates to a pole piece with an unfoamed glue frame, a preparation method of the pole piece, and a full-solid-state battery cell and a preparation method thereof. The pole piece comprises a first pole piece and a glue frame compounded on the surface of the first pole piece. The glue frame raw material comprises a hot melt glue matrix and a thermal expansion type polymer microsphere. The melting point T1 of the hot melt glue matrix is less than the initial foaming temperature T2 of the microsphere, and the microsphere is in an initial unfoamed state. In the heating process after lamination, the heating temperature T5 is greater than T2, the microsphere is foamed by heat to make the glue frame volume expand, and the glue frame is self-adaptively filled into the edge gap between the pole pieces. According to the mechanism of forming the unfoamed glue frame and then foaming, the horizontal and thickness gaps in the Overhang region of the pole piece are self-adaptively filled, and the glue frame waste can be recycled. The application significantly improves the multi-layer lamination yield of the full-solid-state battery, inhibits micro-short circuit and self-discharge, and is suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and relates to an electrode sheet with an unfoamed frame, its preparation method, and an all-solid-state battery cell and its preparation method. Background Technology

[0002] In the manufacturing and processing of all-solid-state batteries, a dense solid-solid interface is crucial to ensure good ion conduction performance. Therefore, high-pressure densification processes such as isostatic pressing and planar pressing are typically used to improve the contact tightness between the electrode and the solid electrolyte layer.

[0003] However, unsupported sheet-like battery stacks are highly susceptible to serious problems such as excessive edge compression, interlayer misalignment, and even cracking under high pressure. To address this issue, a "frame" structure is typically placed around the battery cells. The main function of the frame is to provide edge support during the high-pressure densification process, forming a mechanical boundary with a certain rigidity and dimensional stability. This not only effectively disperses process pressure and maintains the overall geometric integrity of the cell, but also ensures a uniform and dense interface after pressing, thus providing fundamental structural support for the stable performance of subsequent electrochemical processes.

[0004] To construct the frame in all-solid-state batteries, the industry currently mainly uses the following existing technologies: Technology 1: Inkjet printing technology. Using piezoelectric or thermally foamed printheads, low-viscosity photocurable acrylate or siloxane adhesives are precisely sprayed onto the edge of the electrode according to a digital path, and then cured by ultraviolet (UV) or thermoforming.

[0005] Technology 2: Screen printing technology. High-solids-content epoxy resin or polyurethane paste is printed onto the electrode surface through a tensioned polyester or stainless steel screen, and then thermosetting to form a frame structure.

[0006] Technology 3: Dispensing technology. Using a precision screw valve or pneumatic valve, two-component epoxy adhesive, one-component thermosetting adhesive, or UV-curing adhesive is continuously extruded along a pre-programmed trajectory and cured in situ to form an adhesive frame.

[0007] Technology 4: Die-cut Adhesive Tape Lamination Technology. Pre-cut pressure-sensitive adhesive tape (such as acrylic or silicone-based tape) with a polyimide (PI) or polyethylene terephthalate (PET) substrate is directly adhered to the designated edge area of ​​the electrode using a vacuum adsorption and visual alignment system.

[0008] All four existing technologies mentioned above involve directly fabricating the adhesive frame on the electrode surface, but they have significant drawbacks in terms of actual large-scale production and ensuring cell performance, specifically in the following aspects: Inkjet printing technology (Technology 1) requires the simultaneous operation of a printing mechanism, a UV curing mechanism, and a vision positioning mechanism, resulting in extremely complex equipment structure, high procurement and maintenance costs, and limited overall production speed. Screen printing technology (Technology 2) is prone to uneven stress during processing, leading to low processing accuracy and poor consistency. Dispensing technology (Technology 3) is limited by the moving speed of the dispensing head and the dynamic stability of the dispensing process, resulting in low processing efficiency and unevenly shaped adhesive frames. Furthermore, all three technologies (Technology 1, 2, and 3) require the direct spraying or extrusion of liquid adhesives (such as liquid UV adhesives, thermosetting pastes, etc.) onto the electrode surface. During this process, the adhesive and its internal solvents can easily penetrate into the electrode, contaminating and severely affecting the physicochemical properties of the active material and solid electrolyte, posing significant safety hazards and performance degradation risks to the battery. When using die-cut tape bonding technology (Technology 4), in order to ensure the bonding is firm, the tape must cover a certain active area of ​​the positive electrode, which directly leads to the loss of the cell's effective capacity. At the same time, because the frame has a hollow special geometric structure, the central area is hollowed out during the die-cutting process of the tape, generating a large amount of non-recyclable waste and increasing the manufacturing cost of the frame.

[0009] Most critically, in the stacking process of all-solid-state batteries, to accommodate processing and alignment tolerances, the size of the bonding frame manufactured by existing technologies is typically slightly larger than the size of the positive electrode sheet, and its thickness is slightly less than that of the positive electrode sheet. This structural design results in unavoidable physical gaps between the positive electrode sheet and the bonding frame in both the horizontal and vertical directions after stacking. Existing bonding frames cannot adapt to the spatial dimensions of the overhang area formed when the electrode size is smaller than the electrolyte layer, and cannot fill all the gaps in the exposed edge areas. This not only easily leads to bonding frame misalignment, but also causes stress concentration or deformation in the edge areas due to the lack of uniform solid support during subsequent high-voltage densification processes.

[0010] In summary, existing solid-state battery frame fabrication technologies face numerous technical bottlenecks in terms of fabrication efficiency, cost control, safety, and adaptive space filling, necessitating a novel technical solution to address these issues. Summary of the Invention

[0011] To address the aforementioned problems in the prior art, the present invention aims to provide an electrode sheet with an unfoamed frame, its preparation method, and an all-solid-state battery cell and its preparation method, thereby overcoming the shortcomings of the prior art.

[0012] The objective of this invention is achieved through the following technical solution: One aspect of the present invention provides an electrode sheet having an unfoamed frame, comprising a first electrode sheet having a first tab and a frame located on one or both sides of the first electrode sheet; The frame has an opening area for placing the second electrode, and the frame has a non-closed ring structure surrounding the opening area. The break point of the non-closed ring structure is an electrode tab notch for the second electrode tab to extend out of the second electrode. The adhesive frame is made of a thin film material, and its raw materials include a hot melt adhesive matrix and thermally expandable polymer microspheres. The melting point temperature T1 of the hot melt adhesive matrix is ​​less than the initial foaming temperature T2 of the thermally expandable polymer microspheres, and the thermally expandable polymer microspheres are in the initial unfoamed state in the adhesive frame.

[0013] One of the first electrode and the second electrode is a positive electrode, and the other is a negative electrode; that is, when the first electrode is a positive electrode, the second electrode is a negative electrode; and when the first electrode is a negative electrode, the second electrode is a positive electrode. One of the first tabs and the second tab is a negative tab, and the other is a positive tab; when the first electrode is a positive electrode, the first tab is a positive tab, and the second tab is a negative tab; when the first electrode is a negative electrode, the first tab is a negative tab, and the second tab is a positive tab.

[0014] Preferably, the first electrode is a negative electrode, the second electrode is a positive electrode, the first tab is a negative tab, and the second tab is a positive tab.

[0015] The first electrode includes a coated area with an overhang region and an uncoated first electrode tab. The frame is disposed in the overhang region but does not cover the first electrode tab. The length and width of the first electrode are larger than the length and width of the second electrode, and the area of ​​the first electrode that is larger than the second electrode is the overhang region.

[0016] In this invention, to clearly define the dimensions of the electrode and its associated structures, the following definitions are made: "width direction" refers to the direction parallel to the side of the electrode body where the tab is located; "length direction" refers to the direction perpendicular to the width direction. The width of a structure is the dimension measured along the width direction, and the length is the dimension measured along the length direction.

[0017] Preferably, the length of the opening region is greater than the length of the second electrode, and the width of the opening region is greater than the width of the second electrode. More preferably, the length of the second electrode differs from the length of the opening region by 0.05~0.5cm, and the width of the second electrode differs from the width of the opening region by 0.05~0.5cm. The slightly larger size of the opening region allows for tolerance allowance during stacking assembly, preventing hard interference between the second electrode and the frame during installation and reducing the difficulty of stacking alignment. The reserved gap can be completely filled by the foam expansion of the frame during subsequent hot pressing, leaving no voids and balancing assembly convenience with final edge sealing.

[0018] Preferably, the thickness of the adhesive frame is less than the thickness of the second electrode. More preferably, the thickness of the adhesive frame is 30-90% of the thickness of the second electrode, for example, it can be any value among 30%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and 95%. Even more preferably, it is 50-90%.

[0019] More preferably, the thickness of the adhesive frame is 50~200μm.

[0020] Preferably, the width of the tab notch is greater than or equal to the width of the second tab. This ensures that the second tab can extend smoothly from the notch, preventing the rubber frame from obstructing the tab and affecting subsequent welding processes. Preferably, the width of the tab notch differs from the width of the second tab by 0~0.5cm.

[0021] Optionally, the adhesive frame is directly bonded to the surface of the active material coating of the first electrode to form an adhesive frame located on one or both sides of the first electrode.

[0022] The active material coating of the first electrode is distributed on one side or both sides of the first electrode. When the active material coating of the first electrode is distributed on one side of the first electrode, the adhesive frame is laminated on the surface of the active material coating to obtain an adhesive frame located on one side of the first electrode; when the active material coating of the first electrode is distributed on both sides of the first electrode, the adhesive frame is laminated on the surface of one active material coating to obtain an adhesive frame located on one side of the first electrode, or it is laminated on the surfaces of two active material coatings simultaneously to obtain an adhesive frame located on both sides of the first electrode.

[0023] Preferably, a solid electrolyte membrane is laminated on the surface of the active material coating of the first electrode, and the adhesive frame is laminated on the surface of the solid electrolyte membrane to form an adhesive frame located on one or both sides of the first electrode.

[0024] The active material coating of the first electrode is distributed on one side or both sides of the first electrode. When the active material coating of the first electrode is distributed on one side of the first electrode, the solid electrolyte membrane is laminated on the active material coating of the first electrode, and the adhesive frame is laminated on the surface of the solid electrolyte membrane to obtain an adhesive frame located on one side of the first electrode; when the active material coating of the first electrode is distributed on both sides of the first electrode, the solid electrolyte membrane is laminated on the active material coatings on both sides of the first electrode to form solid electrolyte membrane layers on both sides, and the adhesive frame is laminated on the surface of the solid electrolyte membrane on one side to obtain an adhesive frame located on one side of the first electrode, or simultaneously laminated on the surfaces of both solid electrolyte membranes to obtain adhesive frames located on both sides of the first electrode.

[0025] Preferably, the solid electrolyte membrane is made of a sulfide solid electrolyte and / or a halide solid electrolyte; the sulfide solid electrolyte is one or more of the following: thiophosphate as shown in Formula I, argyrophosphate as shown in Formula II, and Li2S-P2S5 binary system derivatives as shown in Formula III. Li 3+a P 1-r M r S 4-z X z Formula I, Where M is one or more of Ge, Si, and Sn, X is O or a halogen, 0≤a≤1, 0≤r<1, and 0≤z≤1.

[0026] Li 6±l P 1-e E e S 5-b R b X-type II, Wherein, 0≤l<1, 0≤e<1, 0≤b<1, E is one or more of Ge, Si, Sn, and Sb, R is O and / or Se, and X is one or more of F, Cl, Br, and I.

[0027] (100-xy)Li₂S·xP₂S₅·yM m N n Formulas I and II Where 0≤x<100, 0≤y<100, 0≤x+y<100, 0≤m<4, 0≤n<6, M is one or more of Li, Ge, Si, Sn, and Sb, and N is one or more of O, Cl, Br, and I.

[0028] The halide solid electrolyte is selected from at least one of the six-coordinate lithium halide salts with the general formula Li3MX6 and halides with the general formula Li2M'X6, wherein M is one or more of Y, In, Sc, and Er, M' is one or more of Zr, Ti, and Sn, and X is a halogen element.

[0029] Preferably, the thickness of the solid electrolyte membrane is 30~200μm.

[0030] The melting point temperature T1 of the hot melt adhesive matrix is ​​greater than the initial foaming temperature T2 of the thermally expandable polymer microspheres. Preferably, the difference between T1 and T2 is 10~100℃.

[0031] Preferably, the melting point of the hot melt adhesive matrix is ​​50~200℃, and the initial foaming temperature of the thermally expandable polymer microspheres is 100~220℃.

[0032] Preferably, the hot melt adhesive matrix is ​​selected from one or more of ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), polyolefin elastomer (POE), polyamide (PA), aliphatic polyester (such as polylactic acid PLA or polycaprolactone PCL), styrene-butadiene-styrene block copolymer (SBS), and styrene-ethylene-butene-styrene block copolymer (SEBS).

[0033] Preferably, the raw materials for preparation further include reinforcing fillers, which are selected from one or more of silica micro powder, titanium dioxide micro powder, boron nitride nanosheets, cellulose nanocrystals, silicon carbide micro powder, and aramid short fibers.

[0034] Preferably, the particle size D50 of the reinforcing filler is 100 nm to 15 μm.

[0035] Preferably, the amount of reinforcing filler added is 5-30 wt% of the total mass of the glue frame. This ensures that the glue does not clog or degrade during thermal processing such as twin-screw extrusion, and maintains the flowability and interfacial adhesion properties of the colloid.

[0036] More preferably, the reinforcing filler undergoes surface modification treatment before being added. Surface modification treatments may include silane coupling agent treatment, plasma treatment, etc.

[0037] Preferably, the thermally expandable polymer microspheres are core-shell structured microspheres with a cross-linked thermoplastic shell encapsulating a low-boiling-point physical foaming agent. The polymer monomers of the shell are selected from one or more of acrylonitrile, methacrylic acid, vinylidene chloride, and styrene monomers, and the low-boiling-point physical foaming agent is selected from one or more of isobutane, isopentane, and carbon dioxide. The core-shell structured foamed microspheres have controllable initial foaming temperature and expansion ratio, and no small molecules are released during the foaming process, so as not to pollute the internal environment of the battery. The cross-linked thermoplastic shell retains its structural integrity after foaming, which can maintain the supporting performance of the frame.

[0038] Preferably, the average particle size D50 of the thermally expandable polymer microspheres in the unfoamed state is 1~20μm, and the volume expands by 2~50 times after foaming.

[0039] Preferably, the amount of the thermally expandable polymer microspheres added is 1 to 20 wt% of the total mass of the frame.

[0040] During the heating process after stacking the electrode with the unfoamed frame and the second electrode, the heating temperature T5 is greater than the initial foaming temperature T2 of the thermally expandable polymer microspheres. The foaming of the thermally expandable polymer microspheres causes the frame volume to expand, adaptively filling the edge gaps between the electrodes.

[0041] A second aspect of the present invention provides a method for preparing an electrode sheet having an unfoamed frame, comprising the following steps: S1. The raw materials, including hot melt adhesive matrix and thermally expandable polymer microspheres, are mixed in a screw extruder, extruded, blow-molded or stretched to obtain an unfoamed film frame; the extrusion temperature T3 is between T1 and T2. S2. The frame film is die-cut for the first time to form the second electrode hollow area and the first electrode tab hollow area; the second electrode hollow area includes the opening area and the second electrode tab area connected to the side of the opening area; the first electrode tab hollow area and the second electrode hollow area are not connected to each other, and are used to expose the first electrode tab; the frame film after the first die-cut is stacked on one or both sides of the first electrode, or stacked on one or both sides of the first electrode with a solid electrolyte membrane, heated and laminated, and then die-cut for the second time to obtain the electrode with the unfoamed frame, and the heating and lamination temperature T4 is between T1 and T2.

[0042] Preferably, the screw extruder is a twin-screw extruder or a single-screw extruder.

[0043] Preferably, the hot melt adhesive matrix is ​​fed from the main feed port of the screw extruder, and the thermally expandable polymer microspheres are fed from the side feed port of the screw extruder. When the raw material includes reinforcing fillers, the reinforcing fillers are fed from the side feed port of the screw extruder. Adding the hot melt adhesive matrix to the main feed port allows it to melt prematurely, while adding the heat-sensitive foaming microspheres and fillers to the side feed port shortens the high-temperature residence time of the microspheres and minimizes premature foaming during extrusion.

[0044] The extrusion temperature T3 needs to be controlled between T1 and T2. Preferably, T3 = T2 - (10~55)℃ and T3 = T1 + (5~35)℃. A higher processing temperature helps the melt flow, shear, and mix evenly.

[0045] The adhesive frame is bonded to the first electrode using a heating mechanism such as an infrared lamp, hot air, or hot roller. The bonding temperature T4 needs to be controlled between T1 and T2. Preferably, T4 = T2 - (10~50)℃ and T4 = T1 + (5~35)℃. When the T4 temperature is closer to T1, the hot melt adhesive matrix softens and is easier to bond when it is above its melting point, avoiding deformation due to excessive fluidity.

[0046] Preferably, the process parameters of the screw extruder include: a screw length-to-diameter ratio of 18~40:1 and a screw speed of 50~200 rpm.

[0047] The width of the second tab region is the same as the width of the tab notch mentioned above. The length of the second tab region is not particularly limited, as long as it ensures that the tab notch can be formed after the second die-cutting, and the second tab can extend from the tab notch. Preferably, the length of the second tab region is greater than or equal to the length of the second tab.

[0048] The width of the cutout area of ​​the first electrode tab is greater than or equal to the width of the first electrode tab. The length of the cutout area of ​​the first electrode tab is not limited, as long as it is ensured that the film of the frame does not cover the first electrode tab after the second die-cutting. Preferably, the length of the cutout area of ​​the first electrode tab is greater than or equal to the length of the first electrode tab.

[0049] Preferably, the minimum distance between the hollowed-out area and the opening area of ​​the first electrode ear is 0.05~0.5 cm.

[0050] The process of stacking the first die-cut film onto one or both sides of the first electrode sheet with the solid electrolyte membrane includes: laminating the solid electrolyte membrane onto one or both sides of the first electrode sheet, and then stacking the first die-cut film onto the surface of the solid electrolyte membrane. The solid electrolyte membrane is then laminated to one or both sides of the first electrode sheet by a transfer printing method.

[0051] A third aspect of this invention provides a method for preparing an all-solid-state battery cell, comprising the following steps: S1. The raw materials, including hot melt adhesive matrix and thermally expandable polymer microspheres, are mixed in a screw extruder, extruded, blow-molded or stretched to obtain an unfoamed film frame; the extrusion temperature T3 is between T1 and T2. S2. The frame film is die-cut for the first time to form the second electrode hollow area and the first electrode ear hollow area; the second electrode hollow area includes the opening area and the second electrode ear area connected to the side of the opening area; the first electrode ear hollow area and the second electrode hollow area are not connected to each other, and are used to expose the first electrode ear; the frame film after the first die-cut is stacked on one or both sides of the first electrode, heated and laminated, and then die-cut for the second time to obtain the electrode with the unfoamed frame, and the heating and laminating temperature T4 is between T1 and T2; S3. Stack the electrode sheet with the unfoamed frame, the solid electrolyte membrane, and the second electrode sheet in that order, with the first electrode sheet without the unfoamed frame placed on the outermost layer to obtain the battery cell. The solid electrolyte membrane and the second electrode sheet are located in the opening area of ​​the electrode sheet with the unfoamed frame. S4. The cell is heated to a temperature T5 greater than T2, causing the frame to expand and fill the gaps under heat, thus obtaining a solid-state battery cell.

[0052] A fourth aspect of this invention provides another method for preparing an all-solid-state battery cell, comprising the following steps: S1. The raw materials, including hot melt adhesive matrix and thermally expandable polymer microspheres, are mixed in a screw extruder, extruded, blow-molded or stretched to obtain an unfoamed film frame; the extrusion temperature T3 is between T1 and T2. S2. The frame film is die-cut for the first time to form the second electrode hollow area and the first electrode tab hollow area; the second electrode hollow area includes the opening area and the second electrode tab area connected to the side of the opening area; the first electrode tab hollow area and the second electrode hollow area are not connected to each other, and are used to expose the first electrode tab; a solid electrolyte membrane is laminated on one or both sides of the first electrode, and then the frame film after the first die-cutting is stacked on the surface of the solid electrolyte membrane, heated and laminated, and then die-cut for the second time to obtain the electrode with the unfoamed frame, and the heating and lamination temperature T4 is between T1 and T2; S3. Stack the electrodes in the order of the first electrode with the unfoamed frame and the second electrode, and place the first electrode without the unfoamed frame on the outermost layer to obtain the battery cell. The second electrode is located in the opening area of ​​the electrode with the unfoamed frame. S4. Heat the cell to a temperature T5 greater than T2, causing the frame to expand and fill the gaps under heat, thus obtaining a solid-state battery cell.

[0053] Preferably, the initial foaming temperature T2 of the thermally expandable polymer microspheres is less than the cell heating temperature T5, which is less than the maximum foaming temperature T6 of the thermally expandable polymer microspheres. The maximum foaming temperature is the temperature at which the thermally expandable polymer microspheres reach their maximum expansion ratio.

[0054] More preferably, T5 = T2 + (5~30)℃, and T5 = T6 - (5~30)℃.

[0055] The cell heating method is selected from at least one of infrared heating, laser heating, and hot pressing. Hot pressing is preferred. Furthermore, the hot pressing time is 100~600s, and the hot pressing pressure is 3~15MPa.

[0056] Preferably, the number of electrodes with unfoamed frames is N, the number of second electrodes is N, and the number of first electrodes without unfoamed frames is 1. N is an integer ≥ 1, and preferably N is 2 to 50.

[0057] The fifth aspect of the present invention provides an all-solid-state battery cell, which is prepared by the preparation method provided in the third or fourth aspect.

[0058] Compared with the prior art, the present invention has the following beneficial effects: 1. In this invention, the unfoamed rubber frame is first laminated and stacked with the electrode at a temperature below the foaming temperature; finally, the temperature is raised to a temperature above the foaming temperature during the hot pressing stage. By utilizing the thermal expansion characteristics of the microspheres, the horizontal gaps and thickness difference gaps in the overhang area of ​​the electrode are actively filled, thereby achieving adaptive sealing and stress buffering.

[0059] 2. This invention uses a hot melt adhesive-based dry film lamination process to replace the traditional liquid adhesive coating / printing process. The adhesive frame is laminated with the electrode in the form of a solid film, which avoids the risk of liquid adhesive solvent penetrating and contaminating the active material and solid electrolyte of the electrode, and eliminates the performance degradation and safety hazards caused by adhesive penetration. At the same time, it eliminates the need for complex inkjet, dispensing or screen printing equipment, which greatly reduces the production line investment cost and maintenance difficulty.

[0060] 3. This invention adopts a dual die-cutting process of "first die-cutting frame making + thermal bonding + visual inspection and correction + second die-cutting trimming". The first die-cutting can pre-produce the shape of the plastic frame in batches. The second die-cutting not only obtains the final negative electrode sheet with the plastic frame, but also marks and corrects defective products through visual inspection, ensuring high precision of electrode core assembly. At the same time, the unfoamed film waste generated by the first die-cutting can be directly returned to the twin-screw extrusion process for remelting and molding, realizing closed-loop material recycling and significantly reducing material loss and manufacturing costs.

[0061] 4. This invention constructs a ternary composite frame system consisting of a hot melt adhesive matrix, reinforcing filler, and thermally expanding microspheres. The hot melt adhesive matrix provides interfacial adhesion and molding processability, the reinforcing filler improves the structural rigidity and dimensional stability of the frame and avoids irregular deformation during foaming, and the thermally expanding microspheres provide controllable volume expansion capability. The three functions work synergistically, enabling the frame to simultaneously possess multiple functions such as edge support, stress buffering, and void filling. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the cross-section of the adhesive frame before and after foaming according to the present invention.

[0063] Figure 2 This is a schematic diagram of the first die-cutting process of the present invention.

[0064] Figure 3 This is a schematic diagram of the bonding of the unfoamed adhesive frame film with the negative electrode and the second die-cutting process of the present invention; Figure 4 This is a schematic diagram of the negative electrode with an unfoamed plastic frame obtained after the second die-cutting of the present invention.

[0065] Figure 5 This is a schematic diagram of the battery cell structure before and after hot pressing according to the present invention. Detailed Implementation

[0066] In the description of this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, and includes both a and b. "Multiple" includes two or more types, and can be two, three, four, five, or more.

[0067] In a preferred embodiment of the present invention, the method for preparing the all-solid-state battery cell specifically includes the following steps: S1. The hot melt adhesive matrix, thermally expandable polymer microspheres, and reinforcing fillers are mixed in a twin-screw extruder, extruded, and blow-molded to obtain an unfoamed film frame. The thickness of the film frame is less than the thickness of the positive electrode sheet. A cross-sectional view of the film frame before foaming is shown below. Figure 1 As shown in the left figure, the extrusion temperature T3 is located between the melting point temperature T1 of the hot melt adhesive matrix and the initial foaming temperature T2 of the thermally expandable polymer microspheres.

[0068] S2. The unfoamed film frame is die-cut for the first time to form non-interconnected positive electrode hollow areas and negative electrode tab hollow areas. The waste material from this die-cutting can be returned to the twin-screw extruder in step 1 for re-forming and reuse. The shape of the positive electrode hollow area is similar to the shape of the positive electrode sheet (the positive electrode sheet includes the main body and the tab part), such as... Figure 2 As shown, the device includes an opening area for accommodating the main body of the positive electrode sheet and a positive electrode tab area connected to the side of the opening area for accommodating the positive electrode tab. The length and width of the opening area are greater than the length and width of the main body of the positive electrode sheet. The width of the positive electrode tab area is greater than or equal to the width of the positive electrode tab. The length of the positive electrode tab area is not particularly limited, as long as it ensures that an electrode tab notch can be formed on the frame after the second die-cutting, and the positive electrode tab can protrude from the electrode tab notch. A negative electrode tab cutout area is used to expose the negative electrode tab. The width of the negative electrode tab cutout area is greater than or equal to the width of the negative electrode tab. The length of the negative electrode tab cutout area is not limited, as long as it ensures that the frame film does not cover the negative electrode tab after the second die-cutting. The minimum distance between the negative electrode tab cutout area and the opening area is 0.05~0.5 cm. A solid electrolyte membrane is laminated on both sides of the negative electrode sheet by a transfer method, and then... Figure 3 As shown, the film after the first die-cutting is stacked on one side of the negative electrode sheet loaded with a solid electrolyte membrane, heated for lamination, and then undergoes a second die-cutting. Figure 3 (The dashed line in the image represents the outline of the second die-cutting) to obtain the negative electrode sheet with the unfoamed frame. The heating and bonding temperature T4 is between T1 and T2; the negative electrode sheet with the unfoamed frame is as follows: Figure 4 As shown, it includes a negative electrode sheet and an unfoamed plastic frame located on one side of the negative electrode sheet; the plastic frame has an opening area for the positive electrode sheet to be placed opposite each other, the plastic frame is a non-closed ring structure surrounding the opening area, and the break of the non-closed ring structure forms a tab notch for the positive electrode tab of the positive electrode sheet to extend out.

[0069] S3. Stack the negative electrode sheets and positive electrode sheets in sequence according to the non-foamed frame, with the outermost layer being the negative electrode sheet without a non-foamed frame, to obtain a battery cell. The positive electrode sheet is located in the opening area of ​​the electrode sheet with the non-foamed frame. Inside the battery cell, there are N layers of negative electrode sheets with non-foamed frames, 1 layer of negative electrode sheets without non-foamed frames, and N layers of positive electrode sheets, where N is an integer ≥ 1. The stacked battery cell is as follows: Figure 5 As shown in the left figure, there are gaps between the positive electrode and the frame, and between the frame and the negative electrode.

[0070] S4. The cell undergoes hot pressing. The hot pressing temperature T5 is greater than T2, the hot pressing time is 100~600s, and the hot pressing pressure is 3~15MPa. This causes the casing to expand and fill the gaps under heat. After hot pressing, the cell passes the OCV and 3-hour voltage drop tests and then proceeds to subsequent processes to obtain an all-solid-state battery cell. Subsequent processes include isostatic pressing, tab welding, encapsulation, settling, formation, and capacity testing. Figure 5 As shown in the right figure, after being heated by hot pressing, the rubber frame expands under the action of heat to fill the gaps.

[0071] The technical solution of the present invention will be further described and illustrated below through specific embodiments. It should be understood that the specific embodiments described herein are only for the purpose of helping to understand the present invention and are not intended to limit the present invention. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0072] In the following examples and comparative examples, the sources of raw materials are as follows: Ethylene-vinyl acetate copolymer (EVA): containing 18wt% VA and a melting point T1 of approximately 80°C; Acrylonitrile-polystyrene foamed microspheres: foaming initiation temperature is 140°C, maximum foaming temperature (the temperature corresponding to the maximum expansion ratio) is 165°C, and particle size D50 in the unfoamed state is 16μm.

[0073] Silica micro powder: D50=5μm; surface has been treated with silane coupling agent.

[0074] Ternary lithium cathode sheets are prepared by the following method: LiNi 0.6 Co 0.2 Mn 0.2 O2 active material, combined with a sulfide-type Li6PS5Cl solid electrolyte, vapor-grown carbon fiber (VGCF) and hydrogenated styrene-butadiene rubber (HSBR) in isobutyl isobutyrate, forms a uniform slurry with a solid content of 45 wt%. This slurry is then subjected to double-sided extrusion coating and drying to obtain a uniform positive electrode sheet with a positive electrode active material loading of 17 mg / cm³. 2A positive electrode sheet with tabs was obtained by punching, and the areal capacity of the positive electrode sheet was measured to be 3 mAh / cm². 2 The main body of the positive electrode plate has a size of 14×10cm and a thickness of 190μm, while the tab size is 4×2cm.

[0075] The graphite anode was prepared by the following method: graphite, sulfide solid electrolyte, VGCF, and hydrogenated styrene-butadiene rubber (HSBR) were mixed in a mass ratio of 83:12:3:2, and isobutyl isobutyrate was added to adjust the solid content to 50wt%. The stirred slurry was uniformly coated on both sides of a copper foil, dried, compacted, and slit to obtain continuous long strip graphite anodes. The areal capacity of the graphite anode was measured to be 3.6 mAh / cm³. 2 .

[0076] The wet-process sulfide electrolyte membrane preparation method includes: using Li6PS5Cl sulfide solid electrolyte powder of silver sulfide germanium type and styrene-ethylene-butene-styrene block copolymer (SEBS) at a mass ratio of 97:3 with isobutyl isobutyrate to prepare a uniform slurry (solid content 40wt%), which is then coated and dried by single-sided extrusion to form a uniform wet-process electrolyte membrane attached to the surface of aluminum foil. The dry film thickness is 100μm and the areal density is 10mg / cm³. 2 .

[0077] In the following examples and comparative examples, the pre-packaging processes were performed in a -60°C dew point dry environment.

[0078] Example 1

[0079] The method for preparing the all-solid-state battery cell in this embodiment is as follows: (1) Ethylene-vinyl acetate copolymer was added to the main feed port of a twin-screw extruder, while acrylonitrile-polystyrene foamed microspheres and silica powder were added from the side feed port. The mass ratio of the three (ethylene-vinyl acetate copolymer: acrylonitrile-polystyrene foamed microspheres: silica powder) was 80:10:10. The screw length-to-diameter ratio was 32:1, the extrusion processing temperature was 85~110°C, the screw speed was 200rpm, the feeding speed was 20kg / h, and the extruder vacuum was -75KPa. After extrusion through a ring die, the material was blow-molded with a blow-up ratio of 2.0, a traction ratio of 5, and a traction speed of 10m / min. The frost line was controlled within the height range of 20-40cm. After air cooling, a film with a thickness of 90μm was obtained.

[0080] (2) The film is die-cut for the first time to form a non-connected positive electrode hollow area and a negative electrode tab hollow area; the shape of the positive electrode hollow area is similar to that of the positive electrode sheet, including an opening area and a positive electrode tab area connected to the side of the opening area, which are used to accommodate the main body of the positive electrode sheet and the tab, respectively. The size of the opening area is 14.1×10.1cm, and the size of the positive electrode tab area is 4.2×2.2cm; the negative electrode tab hollow area is used to expose the negative electrode tab of the negative electrode sheet. The negative electrode tab hollow area is not connected to the positive electrode hollow area, and the minimum distance between the negative electrode tab hollow area and the opening area is 0.15cm. The size of the negative electrode tab hollow area is 4.2×2cm. A wet-process sulfide solid electrolyte membrane (Li6PS5Cl, 100μm thick) loaded on aluminum foil is transferred to both sides of a graphite anode using rollers. The aluminum foil is then peeled off to obtain a graphite anode loaded with the solid electrolyte membrane. A film with a frame, which has been die-cut in the first stage, is stacked on one side of the graphite anode loaded with the solid electrolyte membrane and laminated using hot rollers at a temperature of 100°C. After lamination, a second die-cut is performed to obtain a single anode sheet with an unfoamed frame. The second die-cut area includes the anode body area and the anode tab area. The dimensions of the anode body area are 14.3 cm × 10.3 cm, and the anode tab area matches the shape of the anode tab with dimensions of 4 cm × 2 cm. The two are cut into one piece.

[0081] (3) Stack the negative electrode sheet and positive electrode sheet in sequence with the non-foamed frame, and place the negative electrode sheet without the non-foamed frame on the outermost layer to obtain the cell. The positive electrode sheet is located in the opening area of ​​the electrode sheet with the non-foamed frame. Inside the cell, there are 10 layers of negative electrode sheet with the non-foamed frame, 1 layer of negative electrode sheet with the non-foamed frame (which is located on the outermost layer), and 10 layers of positive electrode sheet.

[0082] (4) After stacking, the bare cells are placed in the hot pressing station. The hot pressing temperature is 150°C, the hot pressing time is 300s, and the pressure is 8MPa. During the hot pressing process, the frame foams and fills the edges. After the hot-pressed cells pass the OCV and 3-hour voltage drop tests, they enter the subsequent processes for further processing to obtain all-solid-state battery cells. The subsequent processes include isostatic pressing, tab welding, packaging, settling, formation, and capacity testing.

[0083] Example 2

[0084] The difference between the all-solid-state battery manufacturing method in this embodiment and that in Embodiment 1 is that silica micropowder is not used in the frame manufacturing process. The frame formulation is ethylene-vinyl acetate copolymer and acrylonitrile-polystyrene foamed microspheres, with a mass ratio of 90:10.

[0085] Example 3

[0086] The method for preparing the all-solid-state battery cell in this embodiment is as follows: (1) Ethylene-vinyl acetate copolymer was added to the main feed port of a twin-screw extruder, while acrylonitrile-polystyrene foamed microspheres and silica powder were added from the side feed port, with a mass ratio of 80:12:8. The screw length-to-diameter ratio was 32:1, the extrusion processing temperature was 95~120°C, the screw speed was 200rpm, the feeding speed was 20kg / h, and the extruder vacuum was -75KPa. After extrusion through a ring die, the material was blow-molded with a blow-up ratio of 2.0, a traction ratio of 6, and a traction speed of 8m / min, while controlling the frost line within a height range of 20-40cm. After air cooling, a film with a thickness of 100μm was obtained.

[0087] (2) The film is die-cut for the first time to form a non-connected positive electrode hollow area and a negative electrode tab hollow area; the shape of the positive electrode hollow area is similar to that of the positive electrode sheet, including an opening area and a positive electrode tab area connected to the side of the opening area, which are used to accommodate the main body of the positive electrode sheet and the tab, respectively. The size of the opening area is 14.2×10.2 cm, and the size of the positive electrode tab area is 4.2×2.2 cm; the negative electrode tab hollow area is used to expose the negative electrode tab of the negative electrode sheet. The negative electrode tab hollow area is not connected to the positive electrode hollow area, and the minimum distance between the negative electrode tab hollow area and the opening area is 0.15 cm. The size of the negative electrode tab hollow area is 4.2×2 cm. The film after the first die-cutting is stacked on one side of the graphite negative electrode and laminated by hot roller at a temperature of 105°C. After lamination, a second die-cutting is performed to obtain a single negative electrode sheet with an unfoamed frame. The second die-cutting area includes the negative electrode body area and the negative electrode tab area. The negative electrode body area is 14.3 cm × 10.3 cm in size, and the negative electrode tab area matches the shape of the negative electrode tab with a size of 4 × 2 cm. The two are cut into one piece.

[0088] (3) A battery cell is obtained by stacking a negative electrode with an unfoamed frame, a dry self-supporting sulfide solid electrolyte membrane (Li6PS5Cl, thickness 120μm, electrolyte membrane size 14.1×10.1cm) and a positive electrode in sequence. The Li6PS5Cl electrolyte membrane and the positive electrode are located in the opening area of ​​the electrode with an unfoamed frame. Inside the battery cell, there are 10 layers of negative electrode with an unfoamed frame, 1 layer of negative electrode without a frame (which is located on the outermost layer), and 10 layers of positive electrode.

[0089] (4) After stacking, the bare cells are placed in the hot pressing station. The hot pressing temperature is 155°C, the hot pressing time is 250s, and the pressure is 8MPa. During the hot pressing process, the frame foams and fills the edges. After the hot-pressed cells pass the OCV and 3-hour voltage drop tests, they enter the subsequent processes for further processing to obtain all-solid-state battery cells. The subsequent processes include isostatic pressing, tab welding, packaging, settling, formation, and capacity testing.

[0090] Example 4

[0091] The difference between Example 4 and Example 1 is that in step (3) of Example 2, the cell contains 30 layers of negative electrode sheets without foamed plastic frames, 1 layer of negative electrode sheets without plastic frames (located on the outermost layer), and 30 layers of positive electrode sheets. Everything else is the same as in Example 1.

[0092] Comparative Example 1 (1) The wet sulfide solid electrolyte membrane (Li6PS5Cl, thickness 100μm) loaded on aluminum foil is transferred to both sides of the graphite anode by rollers, and the aluminum foil is peeled off to obtain the graphite anode loaded with solid electrolyte membrane. The graphite anode sheet is then die-cut to obtain a single graphite anode sheet with a main body size of 14.3×10.3cm and a tab size of 4cm×2cm.

[0093] (2) A battery cell is obtained by stacking graphite negative electrode sheets and positive electrode sheets loaded with solid electrolyte membrane in sequence; the battery cell contains 11 layers of graphite negative electrode sheets and 10 layers of positive electrode sheets.

[0094] (3) After stacking, the bare cells are placed in the hot pressing station. The hot pressing temperature is 150°C, the hot pressing time is 300s, and the pressure is 8MPa. After the hot pressing, the electrode cores pass the OCV and 3-hour voltage drop tests and then proceed to the subsequent processes to obtain all-solid-state battery cells. The subsequent processes include isostatic pressing, tab welding, packaging, settling, formation, and capacity testing.

[0095] Comparative Example 2 The difference between Comparative Example 2 and Comparative Example 1 is that in step (2) of Comparative Example 2, there are 31 layers of graphite negative electrode and 30 layers of graphite positive electrode in the cell.

[0096] Table 1 Comparison of cell yield between the examples and comparative examples

[0097] Yield = Number of good products that pass the OCV test and 3-hour voltage drop test after hot pressing of the electrode core / Number of good products that pass the stacking process * 100%.

[0098] In the comparative examples, no protective structures such as frames were used, while the examples used the foamed frame technology of the present invention. Comparative Example 1 and Example 1 prepared cells with fewer stacked layers. A comparison between Example 1 and Comparative Example 1 shows that even without a frame structure, cells with fewer layers still have a certain yield, but using a frame achieves a higher yield. Example 1 and Example 2 compared frames with different formulations. Example 1 included silica micropowder as a reinforcing filler, significantly improving the structural stability of the frame. Example 2 used only ethylene-vinyl acetate copolymer substrate and foamed microspheres. Although both showed a significant improvement in battery yield compared to Comparative Example 1 without a frame structure, Example 2 was generally inferior to Example 1, indicating that the foamed frame containing reinforcing filler provides the best protection for the battery structure. Comparative Example 2 and Example 4 represent thicker multilayer cell structures, where the use of a foamed frame structure effectively improves the yield. Under low stack-up layer count (11 / 10 layers) conditions, the yield of Example 1 increased from 80% to 95%, the average open-circuit voltage (OCV) significantly increased from 0.53V to 0.89V, and the voltage drop after 3 hours of rest decreased dramatically from 0.17V to 0.01V, confirming that the process can suppress micro-short circuits. More importantly, under the harsh conditions of high stack-up layer count (31 / 30 layers), Comparative Example 2 experienced a sharp drop in yield to 20% and severe self-discharge (voltage drop of 0.22V) due to accumulated errors, while Example 1 still maintained a high yield of 90% and controlled the voltage drop at 0.09V, demonstrating excellent process robustness.

[0099] In summary, the volume expansion of microspheres during hot pressing effectively eliminates voids in the overhang region caused by multilayer stacking. Simultaneously, the introduction of the frame overcomes the misalignment and burr problems associated with multilayer stacking, significantly reducing short circuits caused by these issues. This invention's frame technology, through the coupling of material modification and precision process control, successfully solves the yield bottleneck faced by high-energy-density solid-state batteries in multilayer stacking manufacturing.

[0100] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0101] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0102] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. An electrode sheet with an unfoamed rubber frame, characterized in that, Includes a first electrode plate with a first electrode tab and a plastic frame located on one or both sides of the first electrode plate; The frame has an opening area for placing the second electrode, and the frame has a non-closed ring structure surrounding the opening area. The break point of the non-closed ring structure is an electrode tab notch for the second electrode tab to extend out of the second electrode. The adhesive frame is made of a thin film material, and its raw materials include a hot melt adhesive matrix and thermally expandable polymer microspheres. The melting point temperature T1 of the hot melt adhesive matrix is ​​less than the initial foaming temperature T2 of the thermally expandable polymer microspheres, and the thermally expandable polymer microspheres are in the initial unfoamed state in the adhesive frame.

2. The electrode sheet with an unfoamed frame according to claim 1, characterized in that, The length of the opening region is greater than the length of the second electrode, and the width of the opening region is greater than the width of the second electrode. And / or, the thickness of the adhesive frame is less than the thickness of the second electrode sheet; And / or, the width of the tab notch is greater than or equal to the width of the second tab.

3. The electrode sheet with an unfoamed frame according to claim 2, characterized in that, The length of the second electrode differs from the length of the opening region by 0.05~0.5cm, and the width of the second electrode differs from the width of the opening region by 0.05~0.5cm; And / or, the thickness of the adhesive frame is 30-90% of the thickness of the second electrode sheet; And / or, the width of the tab notch differs from the width of the second tab by 0~0.5cm.

4. The electrode sheet with an unfoamed frame according to claim 1, characterized in that, The adhesive frame is directly bonded to the surface of the active material coating of the first electrode, forming an adhesive frame located on one or both sides of the first electrode; or, A solid electrolyte membrane is laminated on the surface of the active material coating of the first electrode, and the adhesive frame is laminated on the surface of the solid electrolyte membrane to form an adhesive frame located on one or both sides of the first electrode.

5. The electrode sheet with an unfoamed frame according to claim 1, characterized in that, The hot melt adhesive matrix is ​​selected from one or more of the following: ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, polyolefin elastomer, polyamide, aliphatic polyester, styrene-butadiene-styrene block copolymer, and styrene-ethylene-butene-styrene block copolymer. And / or, the thermally expandable polymer microspheres are core-shell structured microspheres with a cross-linked thermoplastic shell encapsulating a low-boiling-point physical foaming agent, wherein the polymer monomer of the shell is selected from one or more of acrylonitrile, methacrylic acid, vinylidene chloride, and styrene monomer, and the low-boiling-point physical foaming agent is selected from one or more of isobutane, isopentane, and carbon dioxide; And / or, the raw materials for preparation further include reinforcing fillers, which are selected from one or more of silica micro powder, titanium dioxide micro powder, boron nitride nanosheets, cellulose nanocrystals, silicon carbide micro powder, and aramid short fibers.

6. The electrode sheet with an unfoamed frame according to claim 5, characterized in that, The particle size D50 of the reinforcing filler is 100nm~15μm; And / or, the average particle size D50 of the thermally expandable polymer microspheres in the unfoamed state is 1~20μm, and the volume expands by 2~50 times after foaming; And / or, the amount of the reinforcing filler added is 5-30 wt% of the total mass of the frame; And / or, the amount of the thermally expandable polymer microspheres added is 1 to 20 wt% of the total mass of the frame.

7. A method for preparing an electrode sheet with an unfoamed frame as described in claim 1, characterized in that, Includes the following steps: S1. The raw materials, including hot melt adhesive matrix and thermally expandable polymer microspheres, are mixed in a screw extruder, extruded, blow-molded or stretched to obtain an unfoamed film frame; the extrusion temperature T3 is between T1 and T2. S2. Perform the first die-cutting on the frame film to form the second electrode hollow area and the first electrode ear hollow area; The second electrode hollow area includes the opening area and the second electrode tab area connected to the side of the opening area; The first electrode tab cutout area and the second electrode cutout area are not connected to each other, and are used to expose the first electrode tab; the glue frame film after the first die-cutting is stacked on one or both sides of the first electrode, or stacked on one or both sides of the first electrode with the solid electrolyte film, heated and laminated, and then die-cut a second time to obtain the electrode with the unfoamed glue frame, and the heating and lamination temperature T4 is between T1 and T2.

8. The preparation method according to claim 7, characterized in that, The hot melt adhesive matrix is ​​fed from the main feed port of the screw extruder, and the thermally expandable polymer microspheres are fed from the side feed port of the screw extruder. And / or, the screw extruder is a twin-screw extruder or a single-screw extruder; And / or, the process parameters of the screw extruder include: a screw length-to-diameter ratio of 18~40:1 and a screw speed of 50~200 rpm; And / or, the width of the second electrode region is the width of the electrode notch; And / or, the width of the hollowed-out area of ​​the first electrode tab is greater than or equal to the width of the first electrode tab; And / or, the minimum distance between the hollowed-out area and the opening area of ​​the first pole ear is 0.05~0.5 cm.

9. The preparation method according to claim 7, characterized in that, The temperature difference between T1 and T2 is 10~100℃; And / or, T3 = T2 - (10~55)℃ and T3 = T1 + (5~35)℃; And / or, T4 = T2 - (10~50)℃ and T4 = T1 + (5~35)℃.

10. A method for preparing an all-solid-state battery cell, characterized in that, Includes the following steps: S1. Obtain the electrode sheet with the unfoamed frame by the preparation method described in claim 7; S2. Stack the electrodes in the order of the electrode sheet with the unfoamed frame, the solid electrolyte membrane, and the second electrode sheet, and place the first electrode sheet without the unfoamed frame on the outermost layer to obtain the battery cell. The solid electrolyte membrane and the second electrode sheet are located in the opening area of ​​the electrode sheet with the unfoamed frame. Alternatively, when the electrode with the unfoamed frame has been laminated with a solid electrolyte membrane, the electrodes are stacked in the order of the electrode with the unfoamed frame and the second electrode, and the outermost layer is a first electrode without the unfoamed frame, to obtain a battery cell, and the second electrode is located in the opening area of ​​the electrode with the unfoamed frame. S3. The cell is heated to a temperature T5 greater than T2, causing the frame to expand and fill the gaps under heat, thus obtaining a solid-state battery cell.

11. The preparation method according to claim 10, characterized in that, The initial foaming temperature T2 of the thermally expandable polymer microspheres is less than the cell heating temperature T5, which is less than the maximum foaming temperature T6 of the thermally expandable polymer microspheres.

12. The preparation method according to claim 11, characterized in that, T5 = T2 + (5~30)℃, and T5 = T6 - (5~30)℃.

13. A solid-state battery cell, characterized in that, It is prepared by the preparation method described in claim 10.

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