Negative pole piece and solid-state lithium ion battery comprising same

Abstract

The invention provides a negative pole piece and a solid-state lithium ion battery comprising the same. The negative pole piece comprises a negative current collector; the negative electrode active layer is arranged on one side or two sides of the negative electrode current collector; the solid electrolyte layer is arranged on one side, far away from the negative current collector, of the negative active layer, and the size of the negative active layer is smaller than the sizes of the negative current collector and the solid electrolyte layer; and the insulating glue layer is arranged around the negative electrode active layer, and the negative electrode current collector and the solid electrolyte layer are bonded together through the insulating glue layer. The negative pole piece provided by the invention can prevent the problems of short circuit, self discharge and thermal runaway in the battery caused by falling of the negative active layer material; expansion of the negative electrode material in the charging and discharging process can be inhibited to a certain extent, and the problem of powder falling caused by expansion is relieved; and the energy density of the battery can be considered while lithium precipitation of the negative electrode is prevented.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a negative electrode plate and a solid-state lithium ion battery comprising the negative electrode plate. Background Art

[0002] The preparation process of lithium-ion batteries generally involves preparing positive and negative electrode sheets first. Usually, the electrode active material, conductive agent, binder and solvent are mixed to form a uniform slurry, which is then coated on the current collector and die-cut to form the electrode sheet after drying. During the die-cutting process, due to the force on the edge of the electrode sheet, the adhesion between the electrode material coating and the current collector deteriorates, and material shedding is prone to occur; during the use of the battery, the active layer at the edge of the battery often loses powder due to battery vibration. If the fallen active material powder adheres to the opposite electrode (for example, the negative active material powder falls on the positive electrode), it will cause an internal short circuit in the battery, causing self-discharge and thermal runaway, and causing safety hazards.

[0003] Moreover, the volume of the negative electrode active material will expand during the charging (lithium insertion) process. For example, the unit cell volume expansion rate of graphite after lithium insertion is about 10%, the volume expansion rate of silicon oxide is about 160%, and the volume expansion rate of silicon can reach about 300%. Since the negative electrode active material is prone to expansion during the charging process, and the inconsistent degree of lithium insertion in the edge and center areas will cause differences in the stress distribution of the negative electrode of the battery, the negative electrode is more prone to powder loss than the positive electrode.

[0004] In addition, lithium-ion batteries in the prior art usually adopt a negative electrode overhang design, that is, the area of ​​the negative electrode active layer is greater than the area of ​​the positive electrode active layer. This is because lithium-ion batteries rely on the embedding / de-embedding of lithium ions on the positive and negative electrodes to achieve normal operation. During the charging process, lithium ions are separated from the positive electrode material and embedded in the negative electrode material through the electrolyte or solid electrolyte. Since the negative electrode material has more micropores, the lithium ions reaching the negative electrode will be embedded in the micropores. The more lithium ions can be embedded in the negative electrode material, the higher the charging capacity of the battery. During the discharge process, lithium ions are separated from the negative electrode material and embedded in the positive electrode material through the electrolyte or solid electrolyte. The more lithium ions embedded in the positive electrode material, the higher the discharge capacity of the battery. If lithium ions move to a position that the negative electrode does not accept, lithium ions will precipitate on the surface of the negative electrode, forming lithium dendrites, piercing the diaphragm, causing a short circuit in the battery, and causing thermal runaway. Therefore, when designing lithium-ion batteries, the negative electrode often needs to be overdesigned to avoid such situations.

[0005] From the perspective of lithium plating safety, the larger the overhang design margin area of ​​the negative electrode, the better. However, if the margin area is too large, the battery energy density will be reduced. Moreover, during the charge and discharge process, under the action of the lithium ion concentration gradient, there is also a lateral diffusion redistribution process of lithium ions in the negative electrode, that is, the lithium ions diffuse from the central area to the overhang area. However, the overhang area does not have a positive electrode active layer opposite to it, so when the overhang area is too large, the lithium ions diffused into this area are prone to irreversible deposition, and lithium plating problems will still occur.

[0006] The above problems have hindered the development and application of lithium-ion batteries to a certain extent, and are issues that need to be urgently resolved in this field. Summary of the invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a negative electrode plate and a solid-state lithium-ion battery containing the same. The negative electrode plate can prevent the problems of short circuit, self-discharge and thermal runaway in the battery caused by the shedding of the negative electrode active layer material, can inhibit the expansion of the negative electrode material during the charging and discharging process to a certain extent, reduce the problem of powder loss caused by the expansion, and can prevent the lithium deposition of the negative electrode while taking into account the energy density of the battery.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a negative electrode plate, the negative electrode plate comprising:

[0010] Anode current collector;

[0011] A negative electrode active layer is disposed on one side or both sides of the negative electrode current collector;

[0012] A solid electrolyte layer is arranged on a side of the negative electrode active layer away from the negative electrode current collector, and the size of the negative electrode active layer is smaller than the size of the negative electrode current collector and the solid electrolyte layer;

[0013] The insulating adhesive layer is arranged around the negative electrode active layer, and the negative electrode current collector and the solid electrolyte layer are bonded together through the insulating adhesive layer.

[0014] Unless otherwise specified, the “size” in the present invention refers to the size of the orthographic projection of the film layer on the plane where the current collector is located.

[0015] In the negative electrode sheet provided by the present invention, the negative electrode current collector and the solid electrolyte layer are bonded together by an insulating adhesive layer to form a closed structure, and the negative electrode active layer is enclosed therein.

[0016] First, the closed structure can prevent the negative electrode active layer material from falling off and entering the battery, causing problems such as short circuit, self-discharge, thermal runaway, etc., thereby improving the safety performance of solid-state lithium-ion batteries without introducing new components.

[0017] Secondly, the closed structure can exert stress on the negative electrode active layer, inhibiting the expansion of the negative electrode material during charging and discharging to a certain extent, and reducing the problem of powder loss caused by expansion;

[0018] In addition, taking silicon-based negative electrode materials as an example, the prior art often adopts a method of forming a coating layer on the surface of the negative electrode active material to inhibit its expansion, but this method has the problem that when the coating layer is too thin, it cannot inhibit expansion and powder loss, when the coating layer is too thick, the energy density of the battery decreases, and the introduced coating layer causes the internal resistance of the battery to increase. However, the negative electrode sheet provided by the present invention does not need to introduce an additional coating layer on the surface of the negative electrode active material, and a closed structure is formed by the negative electrode current collector, the solid electrolyte layer and the insulating glue layer, which can effectively inhibit the expansion of the negative electrode material, and the closed structure eliminates the possibility of the negative electrode material entering the battery.

[0019] Thirdly, the insulating layer replaces part or all of the original overhang area. The advantages of this improvement are:

[0020] 1) Lithium ions in solid-state lithium-ion batteries are transferred through the vacancy migration mechanism. During charging, lithium ions in the solid electrolyte near the negative electrode side move to the negative electrode, generating vacancies. Lithium ions in the solid electrolyte move in turn to fill the vacancies. Vacancies move toward the positive electrode side, and lithium ions from the positive electrode move to fill the vacancies generated on the positive electrode side of the solid electrolyte. The insulating rubber layer does not have the ability to transfer lithium ions or has poor transfer ability at room temperature. Lithium ions are not likely to diffuse to the edge, which can effectively reduce the risk of lithium precipitation in this area.

[0021] 2) The insulating rubber layer replaces part or all of the original overhang area, which can effectively reduce the reaction of the negative electrode to form SEI film (solid electrolyte interface film), thereby reducing the irreversible consumption of lithium ions and preventing the battery's discharge capacity from decreasing. The introduction of the insulating rubber layer will not increase the volume of the battery, thereby ensuring that the battery has a higher energy density;

[0022] 3) The negative electrode active material is generally an inorganic material, which is brittle and has poor toughness. When subjected to high pressure, the overhang area of ​​the negative electrode is easy to break. The insulating rubber layer has good adhesion and toughness. When subjected to pressure, on the one hand, it can withstand a greater limit pressure. On the other hand, due to the adhesion between the materials, it is not easy to break. Therefore, it can effectively prevent the negative electrode structure from being damaged. To put it another way, even if the insulating rubber layer is broken, it will not cause an internal short circuit in the battery.

[0023] In some embodiments of the present invention, the negative electrode plate further includes a conductive layer, the conductive layer is disposed between the negative electrode current collector and the negative electrode active layer, and the size of the conductive layer is smaller than the outer peripheral size of the insulating rubber layer.

[0024] Generally, the area of ​​the conductive layer is not much different from the size of the electrode material layer. The provision of the conductive layer is beneficial to improving the conductivity of the current collector and can also improve the adhesion between the current collector, the conductive layer and the negative electrode active layer.

[0025] In some embodiments of the present invention, the negative electrode plate further includes a bonding layer, and the bonding layer is disposed between the negative electrode current collector and the negative electrode active layer, or between the conductive layer and the negative electrode active layer.

[0026] In the present invention, the bonding layer helps to improve the adhesion of the negative electrode active layer on the current collector, or improves the adhesion of the negative electrode active layer on the conductive layer, and reduces the risk of the negative electrode active layer falling off. The material of the bonding layer can be the same as that of the insulating adhesive layer, or it can be different. When the bonding layer and the insulating adhesive layer are made of the same material, the two can be a connected whole or separated from each other. When the bonding layer and the insulating adhesive layer are made of the same material, the thickness of the bonding layer needs to be thin enough not to affect the electron transmission between the negative electrode active layer and the current collector.

[0027] In the present invention, the inner periphery of the insulating rubber layer and the negative electrode active layer may be in contact with each other (i.e., there is no gap between the negative electrode active layer and the insulating rubber layer), or they may be separated from each other (i.e., there is a gap between the negative electrode active layer and the insulating rubber layer). However, when the two are in contact with each other, it helps to save the negative electrode plate space and improve the energy density of the lithium-ion battery. Therefore, the negative electrode plate in the present invention preferably adopts this structure.

[0028] In some embodiments of the present invention, the thickness of the negative electrode plate at the insulating glue layer is smaller than the thickness of the negative electrode plate at the negative electrode active layer.

[0029] In the present invention, the layers of the negative electrode sheet can be connected together by pressing. The pressing method can be hot pressing, rolling pressing or hot rolling pressing. Those skilled in the art can select a suitable process according to the composition of the materials of each layer.

[0030] By pressing the laminated structure of the current collector, the negative electrode active layer and the solid electrolyte layer, the compaction density of the negative electrode active layer can be further increased and the risk of the negative electrode active layer falling off can be reduced.

[0031] As a preferred embodiment, the pressing pressure is greater than the elastic deformation limit pressure of the insulating rubber layer. Exemplarily, the pressing pressure may be 200-800 MPa. The pressing temperature is lower than the decomposition temperature of the negative electrode active layer material.

[0032] It is understandable that the elasticity of the insulating glue layer is better than that of the negative electrode active layer. In order to ensure that the solid electrolyte layer and the current collector form a good sealing effect on the negative electrode active layer, a large pressure can be applied to the insulating glue layer during pressing so that the negative electrode pole piece presents an edge convergence structure at the insulating glue layer, that is, the thickness of the negative electrode pole piece at the insulating glue layer is less than the thickness of the negative electrode pole piece at the negative electrode active layer. Since the solid electrolyte layer at the insulating glue layer bends toward the current collector after pressing, the solid electrolyte layer should have a certain tensile strength to prevent cracking.

[0033] In some embodiments of the present invention, before pressing, the thickness d1 of the insulating glue layer is equal to the total thickness d0 of the conductive layer and the negative electrode active layer, and the thickness of the solid electrolyte layer is uniform.

[0034] In some embodiments of the present invention, before pressing, the thickness d1 of the insulating glue layer is greater than the total thickness d0 of the conductive layer and the negative electrode active layer, and the thickness d 21 Less than or equal to the thickness d of the solid electrolyte layer at the negative electrode active layer 20 .

[0035] In some embodiments of the present invention, before pressing, the thickness d1 of the insulating glue layer is less than the total thickness d0 of the conductive layer and the negative electrode active layer, and the thickness d1 of the solid electrolyte layer at the insulating glue layer is less than the total thickness d0 of the conductive layer and the negative electrode active layer. 21 Greater than the thickness d of the solid electrolyte layer at the negative electrode active layer 20 .

[0036] In the present invention, the above-mentioned several implementation modes can be adopted to ensure that the thickness of the negative electrode plate at the insulating glue layer is smaller than the thickness of the negative electrode plate at the negative electrode active layer.

[0037] In the present invention, there is no lower limit on the thickness of the insulating rubber layer, as long as it is ensured that after rolling, the current collector and the solid electrolyte layer can be bonded together, the stress in the negative electrode plate is moderate, and the negative active layer and the solid electrolyte layer will not crack.

[0038] In some embodiments of the present invention, the length of the negative electrode active layer in a direction passing through its center is 90-99% of the length of the periphery of the insulating rubber layer in this direction, for example, it can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%, etc.; preferably, it is 95-98%.

[0039] In the invention, the size of the outer periphery of the insulating rubber layer in any direction is larger than that of the negative electrode active layer, so as to cooperate with the solid electrolyte layer to form a sealing effect on the negative electrode active layer, prevent the negative electrode active layer from falling off, causing the negative electrode active material to enter the battery, causing capacity decay, cycle performance degradation and internal short circuit problems. Moreover, it is understandable that the size ratio of the negative electrode active layer to the outer periphery of the insulating rubber layer should not be too large, otherwise it is easy to cause insufficient bonding strength of the insulating rubber layer; the size ratio of the negative electrode active layer to the outer periphery of the insulating rubber layer should not be too small, otherwise it is easy to cause the inactive area on the electrode to be too large, and the battery energy density decreases.

[0040] In some embodiments of the present invention, when the negative electrode plate contains the conductive layer, the length of the negative electrode active layer in a direction passing through its center is 98-102% of the length of the conductive layer in this direction; for example, it can be 98%, 98.5%, 99%, 99.5%, 100%, 100.5%, 101%, 101.5% or 102%, etc.

[0041] It should be noted that the direction mentioned in the above “a direction passing through the center of the negative electrode active layer” is a direction parallel to the surface where the negative electrode active layer is located.

[0042] In some embodiments of the present invention, the size of the solid electrolyte layer is greater than or equal to the outer peripheral size of the insulating glue layer.

[0043] In the present invention, the negative electrode sheet can be rectangular, circular or any other shape permitted in the art. The following takes the shape of the negative electrode sheet as a rectangle as an example to further illustrate the size relationship of each layer in the negative electrode sheet.

[0044] The planar structure of the insulating rubber layer, conductive layer and negative electrode active layer in the negative electrode plate is as follows: Figure 1 As shown, the planar structure of the solid electrolyte layer is Figure 2 As shown, the length direction of the negative electrode sheet is the first direction, and the width direction is the second direction. The tab can be arranged in the first direction or in the second direction.

[0045] Wherein, in the first direction, the length of the outer periphery of the insulating rubber layer is l1, the length of the conductive layer is l2, the length of the negative electrode active layer is l3, and the length of the solid electrolyte layer is l4;

[0046] In the second direction, the length of the outer periphery of the insulating rubber layer is h1, the length of the conductive layer is h2, the length of the negative electrode active layer is h3, and the length of the solid electrolyte layer is h4.

[0047] The above lengths satisfy the following relationship:

[0048] l3 / l1=90-99%, preferably 95-98%; h3 / h1=90-99%, preferably 95-98%;

[0049] l3 / l2=98-102%, h3 / h2=98-102%;

[0050] l2<l1, h2

[0051] l4≥l1,h4≥h1.

[0052] In some embodiments of the present invention, the negative electrode current collector may be a conductive foil, such as copper foil.

[0053] In some embodiments of the present invention, the material of the negative electrode active layer includes a negative electrode active material, a conductive agent, and a binder. The present invention does not impose any particular restrictions on the type of the negative electrode active material. Exemplarily, the negative electrode active material can be one or a combination of graphite, a silicon-based material (such as elemental silicon, a silicon compound).

[0054] In some embodiments of the present invention, the material of the solid electrolyte layer includes one or more of a polymer solid electrolyte, an oxide solid electrolyte, a sulfide solid electrolyte, and a halide solid electrolyte.

[0055] In some embodiments of the present invention, the insulating adhesive layer includes an adhesive material, and the adhesive material is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyacrylic acid, sodium polyacrylate, polyethylene oxide and polyvinyl alcohol.

[0056] In some embodiments of the present invention, the insulating adhesive layer further includes insulating material.

[0057] In some embodiments of the present invention, the content of the insulating material in the insulating adhesive layer is ≥50wt%, preferably ≥80wt%.

[0058] In some embodiments of the present invention, the insulating material includes a ceramic material.

[0059] In some embodiments of the present invention, the ceramic material is selected from one or more of AT9, AT11 ceramics (a high-performance ceramic material composed of aluminum, titanium, oxygen and nitrogen), aluminum oxide, magnesium oxide, titanium oxide and boehmite. Among them, AT9 and AT11 ceramics are high-performance ceramic materials composed of aluminum, titanium, oxygen and nitrogen. Boehmite is also called soft water stone, and its molecular formula is γ-AlOOH (hydrated aluminum oxide).

[0060] ​In the present invention, in order to ensure that the closed structure formed by the current collector, the solid electrolyte layer and the insulating adhesive layer has a good sealing effect, the bonding strength of the insulating adhesive layer is preferably ≥ 2N / m. In order to ensure that the insulating adhesive layer has good insulation performance, the square resistance of the insulating adhesive layer is ≥ 1000mΩ / □.

[0061] In some embodiments of the present invention, the sheet resistance of the conductive layer is less than 50 mΩ / □.

[0062] In a second aspect, the present invention provides a solid-state lithium-ion battery, comprising a positive electrode plate and the negative electrode plate described in the first aspect.

[0063] In the solid-state lithium-ion battery, the negative electrode sheet and the positive electrode sheet are attached to each other, and the solid electrolyte layer of the negative electrode sheet is close to the positive active layer of the negative electrode sheet. When the negative electrode sheet and the positive electrode sheet are double-sided sheets, the solid-state lithium-ion battery may include multiple alternating stacked negative electrode sheets and positive electrode sheets.

[0064] In some embodiments of the present invention, the positive electrode plate includes a positive electrode collector and a positive electrode active layer disposed on one side or both sides of the positive electrode collector, and the positive electrode active layer and the negative electrode active layer in the negative electrode plate have the same size.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] In the negative electrode plate provided by the present invention, the negative electrode current collector, the solid electrolyte layer and the insulating rubber layer form a closed structure, which encloses the negative electrode active layer inside, and can prevent the negative electrode active layer material from falling off and entering the battery, causing problems such as short circuit, self-discharge, thermal runaway, etc. in the battery, thereby improving the safety performance of the solid-state lithium-ion battery without introducing new components.

[0067] The closed structure of the negative electrode plate provided by the present invention can apply stress to the negative electrode active layer, inhibit the expansion of the negative electrode material during the charge and discharge process to a certain extent, and reduce the problem of powder loss caused by the expansion.

[0068] The negative electrode plate provided by the present invention uses an insulating glue layer to replace part or all of the original overhang area. The insulating glue layer does not have the ability to transmit lithium ions or has poor transmission ability. Lithium ions are not easy to diffuse to the edge, which can effectively reduce the risk of lithium precipitation in this area. At the same time, using an insulating glue layer to replace part or all of the original overhang area can reduce the reaction of the negative electrode to generate SEI film, reduce the irreversible consumption of lithium ions, prevent the discharge capacity of the battery from decreasing, and the introduction of the insulating glue layer will not increase the volume of the battery, thereby ensuring that the battery has a higher energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 A schematic diagram of the planar structure of an insulating rubber layer, a conductive layer and a negative electrode active layer in a negative electrode plate provided in one embodiment of the present invention;

[0070] Figure 2 A schematic diagram of the planar structure of a solid electrolyte layer in a negative electrode plate provided in one embodiment of the present invention;

[0071] Figure 3 A schematic diagram of the cross-sectional structure of a negative electrode sheet provided in Example 1 of the present invention;

[0072] Figure 4 A schematic diagram of the cross-sectional structure of a negative electrode sheet provided in Example 2 of the present invention;

[0073] Figure 5 A schematic diagram of the cross-sectional structure of a negative electrode sheet provided in Example 3 of the present invention;

[0074] Figure 6 A schematic diagram of the cross-sectional structure of a negative electrode sheet provided in Example 4 of the present invention;

[0075] Figure 7 A schematic diagram of the cross-sectional structure of a negative electrode sheet provided in Example 5 of the present invention;

[0076] Figure 8 A schematic diagram of the cross-sectional structure of a negative electrode sheet provided in Example 6 of the present invention;

[0077] Fig. 9 This is a SEM image of the negative electrode sheet prepared in Application Example 1 of the present invention at the negative electrode active layer;

[0078] Fig.10 This is a SEM image of the negative electrode sheet prepared in Application Example 1 of the present invention at the insulating glue layer;

[0079] Fig.11 A physical picture of the negative electrode sheet of the solid-state lithium-ion battery prepared in Application Example 1 of the present invention after 500 cycles;

[0080] Fig.12 This is a physical picture of the negative electrode sheet of the solid-state lithium-ion battery prepared in Comparative Example 1 of the present invention after 500 cycles;

[0081] Among them, 1 is the negative electrode current collector, 2 is the negative electrode active layer, 3 is the solid electrolyte layer, 4 is the insulating glue layer, and 5 is the conductive layer. DETAILED DESCRIPTION

[0082] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementations. It should be understood by those skilled in the art that the specific implementations are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0083] Example 1

[0084] This embodiment provides a negative electrode sheet, the cross-sectional structure of which is as follows Figure 3 As shown, including:

[0085] Negative electrode current collector 1;

[0086] A negative electrode active layer 2 is arranged on one side of the negative electrode current collector 1;

[0087] A solid electrolyte layer 3 is arranged on a side of the negative electrode active layer 2 away from the negative electrode current collector 1, and the size of the negative electrode active layer 2 is smaller than the size of the negative electrode current collector 1 and the solid electrolyte layer 3;

[0088] An insulating adhesive layer 4 is closely arranged around the negative electrode active layer 2, and the negative electrode current collector 1 and the solid electrolyte layer 3 are bonded together through the insulating adhesive layer 4, and the outer peripheral size of the insulating adhesive layer 4 is the same as the size of the solid electrolyte layer 3;

[0089] The thickness of the negative electrode plate at the insulating glue layer 4 is smaller than the thickness of the negative electrode plate at the negative electrode active layer 2 .

[0090] Example 2

[0091] This embodiment provides a negative electrode sheet, the cross-sectional structure of which is as follows Figure 4 As shown, including:

[0092] Negative electrode current collector 1;

[0093] A negative electrode active layer 2 is arranged on both sides of the negative electrode current collector 1;

[0094] A solid electrolyte layer 3 is arranged on a side of the negative electrode active layer 2 away from the negative electrode current collector 1, and the size of the negative electrode active layer 2 is smaller than the size of the negative electrode current collector 1 and the solid electrolyte layer 3;

[0095] An insulating adhesive layer 4 is closely arranged around the negative electrode active layer 2, and the negative electrode current collector 1 and the solid electrolyte layer 3 are bonded together through the insulating adhesive layer 4, and the outer peripheral size of the insulating adhesive layer 4 is the same as the size of the solid electrolyte layer 3;

[0096] The thickness of the negative electrode plate at the insulating glue layer 4 is smaller than the thickness of the negative electrode plate at the negative electrode active layer 2 .

[0097] Example 3

[0098] This embodiment provides a negative electrode sheet, the cross-sectional structure of which is as follows Figure 5 As shown, including:

[0099] Negative electrode current collector 1;

[0100] A conductive layer 5 is arranged on one side of the negative electrode current collector 1;

[0101] A negative electrode active layer 2 is arranged on a side of the conductive layer 5 away from the negative electrode current collector 1, and the size of the negative electrode active layer 2 is smaller than the size of the conductive layer 5;

[0102] A solid electrolyte layer 3 is arranged on a side of the negative electrode active layer 2 away from the negative electrode current collector 1, and the size of the negative electrode active layer 2 is smaller than the size of the negative electrode current collector 1 and the solid electrolyte layer 3;

[0103] An insulating rubber layer 4 is closely arranged around the conductive layer 5 and the negative electrode active layer 2, and the negative electrode current collector 1 and the solid electrolyte layer 3 are bonded together through the insulating rubber layer 4, and the outer peripheral size of the insulating rubber layer 4 is the same as the size of the solid electrolyte layer 3;

[0104] The thickness of the negative electrode plate at the insulating glue layer 4 is smaller than the thickness of the negative electrode plate at the negative electrode active layer 2 .

[0105] Example 4

[0106] This embodiment provides a negative electrode sheet, the cross-sectional structure of which is as follows Figure 6 As shown, including:

[0107] Negative electrode current collector 1;

[0108] Conductive layer 5, arranged on both sides of the negative electrode current collector 1;

[0109] A negative electrode active layer 2 is arranged on a side of the conductive layer 5 away from the negative electrode current collector 1, and the size of the negative electrode active layer 2 is smaller than the size of the conductive layer 5;

[0110] A solid electrolyte layer 3 is arranged on a side of the negative electrode active layer 2 away from the negative electrode current collector 1, and the size of the negative electrode active layer 2 is smaller than the size of the negative electrode current collector 1 and the solid electrolyte layer 3;

[0111] An insulating rubber layer 4 is closely arranged around the conductive layer 5 and the negative electrode active layer 2, and the negative electrode current collector 1 and the solid electrolyte layer 3 are bonded together through the insulating rubber layer 4, and the outer peripheral size of the insulating rubber layer 4 is the same as the size of the solid electrolyte layer 3;

[0112] The thickness of the negative electrode plate at the insulating glue layer 4 is smaller than the thickness of the negative electrode plate at the negative electrode active layer 2 .

[0113] Example 5

[0114] This embodiment provides a negative electrode sheet, the cross-sectional structure of which is as follows Figure 7 As shown, including:

[0115] Negative electrode current collector 1;

[0116] A conductive layer 5 is arranged on one side of the negative electrode current collector 1;

[0117] A negative electrode active layer 2 is arranged on a side of the conductive layer 5 away from the negative electrode current collector 1, and the size of the negative electrode active layer 2 is larger than the size of the conductive layer 5;

[0118] A solid electrolyte layer 3 is arranged on a side of the negative electrode active layer 2 away from the negative electrode current collector 1, and the size of the negative electrode active layer 2 is smaller than the size of the negative electrode current collector 1 and the solid electrolyte layer 3;

[0119] An insulating rubber layer 4 is closely arranged around the conductive layer 5 and the negative electrode active layer 2, and the negative electrode current collector 1 and the solid electrolyte layer 3 are bonded together through the insulating rubber layer 4, and the outer peripheral size of the insulating rubber layer 4 is the same as the size of the solid electrolyte layer 3;

[0120] The thickness of the negative electrode plate at the insulating glue layer 4 is smaller than the thickness of the negative electrode plate at the negative electrode active layer 2 .

[0121] Example 6

[0122] This embodiment provides a negative electrode sheet, the cross-sectional structure of which is as follows Figure 8 As shown, including:

[0123] Negative electrode current collector 1;

[0124] Conductive layer 5, arranged on both sides of the negative electrode current collector 1;

[0125] A negative electrode active layer 2 is arranged on a side of the conductive layer 5 away from the negative electrode current collector 1, and the size of the negative electrode active layer 2 is larger than the size of the conductive layer 5;

[0126] A solid electrolyte layer 3 is arranged on a side of the negative electrode active layer 2 away from the negative electrode current collector 1, and the size of the negative electrode active layer 2 is smaller than the size of the negative electrode current collector 1 and the solid electrolyte layer 3;

[0127] An insulating rubber layer 4 is closely arranged around the conductive layer 5 and the negative electrode active layer 2, and the negative electrode current collector 1 and the solid electrolyte layer 3 are bonded together through the insulating rubber layer 4, and the outer peripheral size of the insulating rubber layer 4 is the same as the size of the solid electrolyte layer 3;

[0128] The thickness of the negative electrode plate at the insulating glue layer 4 is smaller than the thickness of the negative electrode plate at the negative electrode active layer 2 .

[0129] Application Example 1

[0130] This application example uses a negative electrode sheet having the structure shown in Example 2 to assemble a solid-state lithium-ion battery with a positive electrode sheet. The preparation method is as follows:

[0131] Preparation of negative electrode sheet: negative electrode active material (75wt% graphite + 25wt% SiO), conductive agent SWCNT (single-walled carbon nanotube) and SP (carbon black) are added to a certain amount of water at a mass ratio of 98.94:0.06:1, mixed evenly, and prepared into negative electrode slurry. The negative electrode slurry is coated on both sides of the negative electrode collector (copper foil) by double-sided coating technology, dried at 110°C for 30min, and roll-formed; then, the insulating glue layer material is coated at the designated position, and the solid electrolyte layer is coated on the surface of the negative electrode active layer and the surface of the insulating glue layer. After coating, it is dried at 100°C for 30min, and roll-formed again to obtain the negative electrode sheet.

[0132] Preparation of positive electrode sheet: Add lithium nickel cobalt manganese oxide NCM613 and conductive agent SP in a mass ratio of 98:2 to a certain amount of N-methylpyrrolidone, mix evenly, and prepare positive electrode slurry. Use double-sided coating technology to coat the positive electrode slurry on both sides of the positive electrode collector (aluminum foil), dry at 80°C for 30 minutes, and roll-form.

[0133] Preparation of solid-state lithium-ion battery: The prepared negative electrode sheet and positive electrode sheet are stacked to form a solid-state lithium-ion battery, and the number of stacking layers is 100.

[0134] Among them, the negative electrode active material is 75wt% graphite + 25wt% SiO, the thickness of the negative electrode active layer is 35μm, the length l3 is 71mm, and the width h3 is 56mm;

[0135] The solid electrolyte layer is a polymer / oxide composite electrolyte layer, the polymer is PVDF (polyvinylidene fluoride), the oxide is LLZO (lithium lanthanum zirconium oxide), the weight ratio of PVDF:LLZO is 1:9, the thickness is 30 μm, the length l4 is 73 mm, and the width h4 is 58 mm;

[0136] The insulating adhesive layer material is 15wt% polyvinylidene fluoride + 85wt% boehmite, the thickness of the insulating adhesive layer is 10μm, the outer perimeter length l1 is 73mm, and the outer perimeter width h1 is 58mm;

[0137] The thickness of the positive electrode active layer is 45 μm, which is the same size as the negative electrode active layer.

[0138] The morphology of the negative electrode sheet prepared in Example 1 was characterized by scanning electron microscopy (SEM). Fig. 9 (at the negative electrode active layer) and Fig.10 (Insulation layer) as shown.

[0139] Application Example 2

[0140] The difference from Application Example 1 is that the negative electrode active material is 70wt% graphite+25wt% SiO+5wt% Si, and the insulating adhesive layer material is 15wt% vinylidene fluoride-hexafluoropropylene copolymer+85wt% alumina.

[0141] Application Example 3

[0142] The difference from Application Example 1 is that the positive electrode active material is lithium cobalt oxide.

[0143] Application Example 4

[0144] The difference from Application Example 1 is that the negative electrode active material is graphite, and the insulating glue layer material is 10wt% polyethylene oxide+90wt% aluminum oxide.

[0145] Comparative Example 1

[0146] The difference from Application Example 1 is that there is no insulating glue layer in the negative electrode plate, and the solid electrolyte layer and the negative electrode active layer have the same size.

[0147] The performance of the prepared solid-state lithium-ion battery was tested, and the test method was as follows:

[0148] Acupuncture test: refer to GBT31485;

[0149] Extrusion test: refer to GB38031, the extrusion deformation is 60%;

[0150] Cycle performance: The solid-state lithium-ion battery was charged to 4.3V at 0.33C, and then discharged to 2.75V at 0.33C to test the initial discharge specific capacity; the battery was then cycled under the conditions of a charge and discharge voltage of 2.75-4.3V and a charge and discharge current of 1C to test the discharge specific capacity and calculate the capacity retention rate;

[0151] After the battery has been cycled for 500 times, disassemble the battery and observe whether the negative electrode has any powder falling off.

[0152] The results of the above tests are shown in Table 1 below.

[0153] Table 1

[0154]

[0155]

[0156] The actual picture of the negative electrode sheet of the solid-state lithium-ion battery prepared in Example 1 after 500 cycles is as follows: Fig.11 As shown, the actual picture of the negative electrode sheet of the solid-state lithium-ion battery prepared in Comparative Example 1 after 500 cycles is as follows Fig.12 As shown in the figure, it can be seen that the solid-state lithium-ion battery prepared in Example 1 does not lose powder after cycling, while the solid-state lithium-ion battery prepared in Comparative Example 1 loses powder severely after cycling.

[0157] From the experimental results in Table 1, it can be seen that the solid-state lithium-ion battery (Comparative Example 1) using conventional negative electrode sheets caught fire in the puncture test and the extrusion test (the possible reason is that under strong impact or a large degree of extrusion, the battery electrode has a large degree of internal short circuit, causing thermal runaway fire), and the negative electrode sheet has powder loss after the cycle, and the 500-cycle capacity retention rate is less than 80%. However, the solid-state lithium-ion battery using the negative electrode sheet provided by the present invention did not catch fire in the puncture test and the extrusion test, and the negative electrode sheet did not fall off after the cycle, and the cycle performance was significantly improved, indicating that the negative electrode sheet provided by the present invention can effectively prevent the negative electrode material from falling off and entering the battery, causing problems such as internal short circuit, self-discharge, and thermal runaway of the battery; and can inhibit the expansion of the negative electrode material during the charge and discharge process to a certain extent, and improve the cycle performance of the battery.

[0158] The above description is only a specific embodiment of the present disclosure, so that those skilled in the art can understand or implement the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to the embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A negative electrode plate, characterized in that: The negative electrode plate comprises: Anode current collector; A negative electrode active layer is disposed on one side or both sides of the negative electrode current collector; A solid electrolyte layer is arranged on a side of the negative electrode active layer away from the negative electrode current collector, and the size of the negative electrode active layer is smaller than the size of the negative electrode current collector and the solid electrolyte layer; The insulating adhesive layer is arranged around the negative electrode active layer, and the negative electrode current collector and the solid electrolyte layer are bonded together through the insulating adhesive layer.

2. The negative electrode sheet according to claim 1, characterized in that: The negative electrode plate further includes a conductive layer, which is disposed between the negative electrode current collector and the negative electrode active layer, and the size of the conductive layer is smaller than the outer peripheral size of the insulating rubber layer.

3. The negative electrode sheet according to claim 2, characterized in that: The length of the negative electrode active layer in a direction passing through the center thereof is 98-102% of the length of the conductive layer in the direction.

4. The negative electrode sheet according to any one of claims 1 to 3, characterized in that: The negative electrode plate further includes a bonding layer, and the bonding layer is arranged between the negative electrode collector and the negative electrode active layer, or between the conductive layer and the negative electrode active layer.

5. The negative electrode sheet according to any one of claims 1 to 4, characterized in that: The thickness of the negative electrode plate at the insulating glue layer is smaller than the thickness of the negative electrode plate at the negative electrode active layer.

6. The negative electrode sheet according to any one of claims 1 to 5, characterized in that: The length of the negative electrode active layer in a direction passing through the center thereof is 90-99%, preferably 95-98%, of the length of the periphery of the insulating rubber layer in the direction.

7. The negative electrode sheet according to any one of claims 1 to 6, characterized in that: The size of the solid electrolyte layer is greater than or equal to the outer peripheral size of the insulating rubber layer.

8. The negative electrode sheet according to any one of claims 1 to 7, characterized in that: The sheet resistance of the insulating adhesive layer is ≥1000mΩ / □; Preferably, the insulating adhesive layer comprises a bonding material, and the bonding material is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyacrylic acid, sodium polyacrylate, polyethylene oxide and polyvinyl alcohol; Preferably, the insulating adhesive layer further comprises insulating material; Preferably, the content of the insulating material in the insulating adhesive layer is ≥50wt%, preferably ≥80wt%; Preferably, the insulating material comprises a ceramic material; Preferably, the ceramic material is selected from one or more of AT9 ceramic, AT11 ceramic, aluminum oxide, magnesium oxide, titanium oxide and boehmite.

9. A solid-state lithium-ion battery, characterized in that: The solid-state lithium-ion battery comprises a positive electrode sheet and a negative electrode sheet as described in any one of claims 1 to 8.

10. The solid-state lithium-ion battery according to claim 9, characterized in that: The positive electrode plate comprises a positive electrode current collector and a positive electrode active layer arranged on one side or both sides of the positive electrode current collector, and the positive electrode active layer has the same size as the negative electrode active layer in the negative electrode plate.

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