Battery pole piece, manufacturing method thereof and secondary battery

Abstract

The invention discloses a battery pole piece, a manufacturing method thereof and a secondary battery. The pole piece comprises a current collector and an active material layer arranged on at least one surface of the current collector, the middle part of the pole piece is provided with a pole lug groove, the pole lug groove is a non-through groove along the Y direction, the pole lug groove is provided with a pole lug, and the pole lug comprises a connecting section positioned in the pole piece and an exposed section positioned outside the pole piece. Compared with the prior art, the non-through tab groove is formed in the middle of the pole piece, and the tab is arranged in the tab groove, so that the surrounding area of the tab can be coated with the active material, the space utilization rate of the pole piece is remarkably improved, more active substances can be accommodated under the same volume, and the energy density of the battery is effectively improved; meanwhile, as the coating area of the active material is increased, the current distribution is more uniform, the internal resistance is further reduced, and the rate capability of the battery is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary batteries, and in particular relates to a battery pole piece and a manufacturing method thereof, and a secondary battery. Background Art

[0002] As a highly efficient energy storage device, lithium-ion batteries are widely used in portable electronic devices, electric vehicles, and renewable energy storage. As the market demand for batteries with high energy density, high rate performance, and low internal resistance continues to increase, battery manufacturers have been seeking ways to optimize battery structure and manufacturing processes.

[0003] In traditional wound lithium-ion batteries, the design and manufacture of the pole piece is one of the key factors affecting battery performance. Early designs usually set the pole lug at the head of the pole piece. This structure is simple and easy to manufacture, but in some applications it may cause uneven current distribution, affecting battery performance and life.

[0004] In order to improve current distribution and optimize battery performance, some manufacturers have begun to try to weld the tabs in the middle of the pole piece. This design can disperse the current more evenly, helping to improve the battery's rate performance and reduce internal resistance. However, this improvement also brings new challenges.

[0005] Limited by the existing production process, manufacturers usually use the method of directly jumping the gap to achieve the welding of the middle pole ear. This method will form an empty foil area that runs through the pole piece at the pole ear position, that is, an area without active material coating. Although this empty foil area facilitates the welding of the pole ear, it also causes waste of space inside the battery. This space waste not only reduces the energy density of the battery, but may also affect the overall performance of the battery.

[0006] In addition, the presence of empty foil areas may lead to uneven current distribution, increase the risk of local hot spots, and thus affect the safety and life of the battery. At the same time, due to the reduction of active material coating area, the actual capacity of the battery will also be reduced accordingly.

[0007] Therefore, there is a need for a solution that can maximize the use of the pole piece space while maintaining the advantages of the intermediate pole ear design, and can increase the coating area of ​​the active material as much as possible without affecting the welding of the pole ear, thereby increasing the energy density of the battery, improving the rate performance and reducing the internal resistance. Summary of the invention

[0008] The purpose of the present invention is to provide a battery pole piece with high space utilization rate in view of the shortcomings of the prior art, which can reduce the internal resistance, improve the rate performance and increase the energy density of the battery.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A battery pole piece, comprising a current collector and an active material layer arranged on at least one surface of the current collector; a pole lug groove is arranged in the middle of the pole piece, the pole lug groove is a non-through groove along the Y direction, the pole lug groove is provided with a pole lug, and the pole lug includes a connecting section located inside the pole piece and an exposed section located outside the pole piece.

[0011] Preferably, the tab groove is covered with heat-resistant insulating tape, and the heat-resistant insulating tape covers the connecting section of the tab; the area of ​​the heat-resistant insulating tape accounts for 30~200% of the forward projection area of ​​the tab groove; the heat-resistant insulating tape has a heat-resistant temperature of ≥130°C.

[0012] Preferably, the heat-resistant insulating adhesive tape comprises a substrate and an adhesive layer disposed on the surface of the substrate; the substrate is PET, PP, PEEK, PI, PTFE, PA or PPS, and the adhesive layer is an acrylic adhesive, a silicone adhesive, a vinyl acrylate adhesive, a nitrile rubber adhesive or a chloroprene rubber adhesive. The heat-resistant insulating adhesive tapes made of the above materials all have good high temperature resistance and insulation performance; in addition, it should be noted that heat-resistant insulating adhesive tapes made of other materials can also be used as long as they can meet the corresponding heat resistance and insulation requirements.

[0013] Preferably, the exposed section of the tab is provided with tab glue; along the Y direction, the absolute value of the distance between the upper edge of the heat-resistant insulating tape and the lower edge of the tab glue is 0.1-2 mm.

[0014] Preferably, the connecting section of the tab is also coated with a thermally conductive material layer. The thermally conductive material is at least one of thermally conductive silica gel, graphene, carbon nanotubes, and phase change materials, wherein the phase change material is preferably a solid-solid phase change material, such as polyethylene glycol. The thermal conductivity and heat dissipation performance of the tab can be improved by providing a thermally conductive material layer.

[0015] Preferably, the width of the tab accounts for 30-100% of the width of the tab groove.

[0016] Preferably, the width of the tab groove is 3 to 20 mm, more preferably 6 to 15 mm.

[0017] Preferably, the length of the pole lug groove accounts for 10-90% of the width of the pole piece.

[0018] Preferably, the length of the tab groove is 10-100 mm, more preferably 15-50 mm.

[0019] Preferably, empty foil areas are provided at both ends of the pole piece, and the empty foil areas are covered with heat-resistant insulating adhesive tape.

[0020] Preferably, the current collector is a positive electrode current collector and / or a negative electrode current collector, the active material layer is a positive electrode active material layer and / or a negative electrode active material layer, the positive electrode active material layer is arranged on at least one surface of the positive electrode current collector, and the negative electrode active material layer is arranged on at least one surface of the negative electrode current collector;

[0021] The electrode sheet is a positive electrode sheet and / or a negative electrode sheet, a positive electrode tab groove is provided in the middle of the positive electrode sheet, the positive electrode tab groove is a non-through groove along the Y direction, and the positive electrode tab groove is provided with a positive electrode tab; a negative electrode tab groove is provided in the middle of the negative electrode sheet, the negative electrode tab groove is a non-through groove along the Y direction, and the negative electrode tab groove is provided with a negative electrode tab;

[0022] The position where the positive electrode plate is opposite to the negative electrode tab is covered with heat-resistant insulating adhesive tape; and / or, the position where the positive electrode plate is opposite to the negative electrode tab is provided with an empty foil area, and the empty foil area is covered with heat-resistant insulating adhesive tape.

[0023] Preferably, the surface density of the positive electrode active material layer is 10-30 mg / cm 2 , more preferably 16 to 23 mg / cm 2 The surface density of the negative electrode active material layer is 5-15 mg / cm 2 , more preferably 5 to 12 mg / cm 2 .

[0024] Preferably, empty foil areas are provided at both ends of the positive electrode plate, and the empty foil areas are covered with heat-resistant insulating tape, and / or, empty foil areas are provided at both ends of the negative electrode plate, and the empty foil areas are covered with heat-resistant insulating tape.

[0025] In addition, the present invention also provides a method for manufacturing the above-mentioned battery electrode sheet, comprising the following steps:

[0026] 1) using a double-cavity coating die to coat the active material layer slurry on at least one surface of the current collector;

[0027] 2) One of the material chambers applies the active material layer slurry on the surface of the current collector by continuous coating to form a first coating layer with a complete coating area;

[0028] 3) another material chamber applies the active material layer slurry to the gap portion adjacent to the first coating layer by intermittent coating to form a second coating layer having alternating coating areas and blank areas;

[0029] 4) Cutting along the edge close to the blank area to obtain a single electrode having both the first coating layer and the second coating layer;

[0030] 5) Welding the electrode lugs in the blank area to obtain the battery electrode sheet.

[0031] Preferably, in step 4), the cutting line is located in the first coating layer, and the distance between the edge of the blank area and the cutting line is 1 to 10 mm. This coating process is prone to thinning of the coating thickness on both sides of the blank area. If the cutting is performed directly at the edge of the blank area, it is easy to cause lithium deposition in the thinned area at the edge of the pole piece. Therefore, when cutting, the thinned part of the second coating layer close to the blank area is cut 1 to 10 mm to the blank area, so as to avoid lithium deposition in the thin area of ​​the pole piece. In addition, it should be noted that the second coating layer cut to the blank area can be cut off and then the pole lugs can be welded, or the pole lugs can be directly welded without cutting.

[0032] In addition, the present invention also provides a secondary battery, comprising the battery electrode described in any of the above paragraphs or a battery electrode produced by the method for producing a battery electrode described in any of the above paragraphs.

[0033] Preferably, the outer surface of the secondary battery is covered with a thermal conductive material layer, which can improve the thermal conductivity and heat dissipation performance of the battery.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects:

[0035] 1) Can effectively improve battery energy density: Compared with the traditional design of penetrating empty foil area, the present invention sets a non-penetrating pole ear groove in the middle of the pole piece and sets the pole ear therein. This structural design can also coat the active material in the area around the pole ear, which significantly improves the space utilization of the pole piece, so that more active materials can be accommodated in the same volume, effectively improving the battery energy density.

[0036] 2) Reduce battery internal resistance and improve rate performance: The center-placed pole ear design itself is conducive to reducing battery internal resistance because it shortens the average transmission distance of current in the pole piece; at the same time, since the present invention increases the coating area of ​​the active material, the current distribution is more uniform, further reducing the internal resistance and improving the rate performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of the structure of a battery electrode sheet according to an embodiment of the present invention;

[0038] Figure 2 A top view of a positive electrode sheet according to an embodiment of the present invention;

[0039] Figure 3 is a cross-sectional schematic diagram of a positive electrode sheet according to an embodiment of the present invention;

[0040] Figure 4 A top view of a negative electrode sheet according to an embodiment of the present invention;

[0041] Figure 5 is a schematic cross-sectional view of a negative electrode sheet according to an embodiment of the present invention;

[0042] Figure 6 It is a schematic structural diagram of a battery electrode before cutting according to an embodiment of the present invention.

[0043] In the figure: 1. current collector; 2. active material layer; 3. pole ear groove; 4. pole ear; 5. pole ear glue; 6. heat-resistant insulating tape; 11. positive electrode current collector; 12. negative electrode current collector; 21. positive electrode active material layer; 22. negative electrode active material layer; 31. positive electrode ear groove; 32. negative electrode ear groove; 41. positive electrode ear; 42. negative electrode ear; 100. first coating layer; 200. second coating layer; 300. blank area. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] In the description of this application, unless otherwise clearly specified and limited, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance; the term "plurality" refers to two or more; unless otherwise specified or explained, the terms "connected", "fixed", etc. should be understood in a broad sense, for example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0046] Please see attached Figure 1 According to the first aspect of the present application, the present application provides a battery pole piece, comprising a current collector 1 and an active material layer 2 arranged on at least one surface of the current collector 1; a pole lug groove 3 is arranged in the middle of the pole piece, and the pole lug groove 3 is a non-through groove along the Y direction. The pole lug groove 3 is provided with a pole lug 4, and the pole lug 4 includes a connecting section located inside the pole piece and an exposed section located outside the pole piece.

[0047] Among them, the battery pole piece provided by the present invention can significantly improve the space utilization rate of the pole piece by setting a non-through pole ear groove 3 in the middle of the pole piece and setting a pole ear 4 therein. Compared with the traditional pole ear set at the edge or the pole ear set in the middle, the structural design of the non-through middle pole ear of the present invention avoids the waste of space outside the pole piece welding pole ear area, so that more active materials can be accommodated under the same volume, and the energy density of the battery is improved. At the same time, the design of the middle pole ear can also shorten the electron transmission path, reduce the in-plane internal resistance of the pole piece, and improve the high-rate charge and discharge performance.

[0048] In one embodiment of the present application, the tab slot 3 is covered with a heat-resistant insulating tape 6, and the heat-resistant insulating tape 6 covers the connecting section of the tab 4, which increases the safety of the battery cell and prevents short circuits; the area of ​​the heat-resistant insulating tape 6 accounts for 30-200% of the forward projection area of ​​the tab slot 3; the heat-resistant insulating tape 6 has a heat-resistant temperature of ≥130°C. Preferably, the area of ​​the heat-resistant insulating tape 6 accounts for 100-150% of the forward projection area of ​​the tab slot 3; it can effectively avoid direct contact between the positive and negative electrodes caused by thermal shrinkage of the isolation film, and can also effectively cover the burrs on the edges of the current collector 1 and the tab 4, prevent the occurrence of short circuits in the battery cell, and improve the safety of the battery cell. Preferably, the heat-resistant temperature of the heat-resistant insulating tape 6 is 130°C-500°C; generally speaking, the higher the heat-resistant temperature of the heat-resistant insulating tape 6, the better, and in order to improve the safety of the battery cell, it is generally necessary to be higher than the heat shrinkage temperature of the isolation film.

[0049] In one embodiment of the present application, the heat-resistant insulating adhesive tape 6 includes a substrate and an adhesive layer provided on the surface of the substrate; the substrate is PET, PP, PEEK, PI, PTFE, PA or PPS, and the adhesive layer is an acrylic adhesive, a silicone adhesive, a vinyl acrylate adhesive, a nitrile rubber adhesive or a chloroprene rubber adhesive. The heat-resistant insulating adhesive tape 6 made of the above materials has good high temperature resistance and insulation performance; in addition, it should be noted that other materials of heat-resistant insulating adhesive tape 6 can also be used as long as they can meet the corresponding heat resistance and insulation requirements.

[0050] In one embodiment of the present application, the exposed section of the tab 4 is provided with a tab glue 5; along the Y direction, the absolute value of the distance between the upper edge of the heat-resistant insulating adhesive tape 6 and the lower edge of the tab glue 5 is 0.1-2 mm. In this way, the heat-resistant insulating adhesive tape 6 can cover the burrs on the edge of the tab 4, and can avoid the oversized adhesive tape from affecting the top sealing of the aluminum-plastic film, and can also reduce the waste of adhesive tape.

[0051] In one embodiment of the present application, the connecting section of the pole ear 4 is also covered with a thermal conductive material layer. The thermal conductive material is at least one of thermal conductive silicone, graphene, carbon nanotubes, and phase change materials, wherein the phase change material is preferably a solid-solid phase change material, such as polyethylene glycol. By providing a thermal conductive material layer, the heat conduction at the pole ear 4 can be accelerated, the local temperature rise can be reduced, and the heat dissipation performance and safety of the pole piece can be improved. Thermal conductive silicone, graphene, carbon nanotubes and other materials have high thermal conductivity, and the phase change material can absorb excess heat at the pole ear 4, which can significantly improve the thermal conductivity and heat dissipation performance of the pole ear 4.

[0052] In one embodiment of the present application, the width of the pole tab 4 accounts for 30-100% of the width of the pole tab slot 3; more preferably, it is 85-100%. Optimizing the proportional relationship between the width of the pole tab 4 and the width of the pole tab slot 3 can minimize the occupation of the active material area by the pole tab slot 3 while ensuring the welding reliability of the pole tab 4, thereby improving the energy density while ensuring the mechanical strength and structural integrity of the pole piece.

[0053] In one embodiment of the present application, the width of the tab slot 3 is 3-20 mm, more preferably 6-15 mm, for example, 6 mm, 8 mm, 10 mm or 12 mm.

[0054] In one embodiment of the present application, the length of the tab slot 3 accounts for 20-60% of the width of the pole piece. Optimizing the proportional relationship between the length of the tab slot 3 and the width of the pole piece can minimize the occupation of the active material area by the tab slot 3 while ensuring the welding reliability of the tab 4, thereby improving the energy density while ensuring the mechanical strength and structural integrity of the pole piece.

[0055] In one embodiment of the present application, the length of the tab slot 3 is 10-100 mm, more preferably 15-50 mm, for example, 15 mm, 18 mm, 20 mm, 22 mm or 25 mm.

[0056] In one embodiment of the present application, empty foil areas are provided at both ends of the pole piece, and the empty foil areas are covered with heat-resistant insulating adhesive tape 6. When the battery cell is at high temperature, since the heat-resistant insulating adhesive tape 6 has good high temperature resistance, even if the isolation film undergoes thermal shrinkage, the empty foil areas of the positive pole piece and the negative pole piece will not directly contact each other, resulting in a short circuit of the battery, which effectively improves the safety performance of the battery; in addition, the provision of the heat-resistant insulating adhesive tape 6 is also conducive to preventing dust pollution and has anti-corrosion functions, which can effectively protect the stability and life of the battery cell.

[0057] In one embodiment according to the present application, Figures 2~5As shown, the current collector 1 is a positive electrode current collector 11 and / or a negative electrode current collector 12, the active material layer 2 is a positive electrode active material layer 21 and / or a negative electrode active material layer 22, the positive electrode active material layer 21 is arranged on at least one surface of the positive electrode current collector 11, and the negative electrode active material layer 22 is arranged on at least one surface of the negative electrode current collector 12;

[0058] The electrode sheet is a positive electrode sheet and / or a negative electrode sheet, a positive electrode ear slot 31 is provided in the middle of the positive electrode sheet, the positive electrode ear slot 31 is a non-through slot along the Y direction, and a positive electrode ear 41 is provided in the positive electrode ear slot 31; a negative electrode ear slot 32 is provided in the middle of the negative electrode sheet, the negative electrode ear slot 32 is a non-through slot along the Y direction, and a negative electrode ear 42 is provided in the negative electrode ear slot 32;

[0059] The position where the positive electrode sheet and the negative electrode tab 42 are opposite is covered with heat-resistant insulating adhesive tape 6; and / or, the position where the positive electrode sheet and the negative electrode tab 42 are opposite is provided with an empty foil area, and the empty foil area is covered with heat-resistant insulating adhesive tape 6. By covering the heat-resistant insulating adhesive tape 6 at the position where the positive electrode sheet and the negative electrode tab are opposite, it is possible to effectively prevent the edge burrs of the negative electrode tab from damaging the positive electrode sheet or lithium deposition on the negative electrode due to uneven thickness; in addition, when the battery cell is at high temperature, since the heat-resistant insulating adhesive tape 6 has good high temperature resistance, even if the separator shrinks thermally, the positive electrode sheet and the negative electrode sheet will not be in direct contact to cause a short circuit in the battery, which effectively improves the safety performance of the battery.

[0060] In one embodiment of the present application, the positive electrode current collector 11 is aluminum foil or its alloy material, and the negative electrode current collector 12 is copper foil or its alloy material; the positive electrode active material layer 21 includes a positive electrode active material, a conductive agent and a binder; the negative electrode active material layer 22 includes a negative electrode active material, a conductive agent and a binder. Among them, the positive electrode active material may include but is not limited to lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium cobalt oxide, lithium iron phosphate, etc.; the negative electrode active material may include but is not limited to natural graphite, artificial graphite, mesophase micro carbon beads, hard carbon, soft carbon, silicon, silicon carbon material, etc., the conductive agent may include but is not limited to conductive carbon black, acetylene black, Ketjen black, carbon nanofibers, carbon nanotubes, graphene, etc.; the adhesive may include but is not limited to polyvinylidene fluoride, styrene butadiene rubber, polyvinyl alcohol, polyurethane, etc. Among them, the proportion and preparation of the active material layer slurry belong to the conventional technology in the field and will not be described in detail here.

[0061] In one embodiment of the present application, the surface density of the positive electrode active material layer 21 is 10-30 mg / cm 2 , more preferably 16~23mg / cm 2 The surface density of the negative electrode active material layer 22 is 5 to 15 mg / cm 2 , more preferably 5 to 12 mg / cm 2By reasonably matching the surface density of the positive electrode and the negative electrode active material layer 22, the energy density can be improved while taking into account the matching of the positive and negative electrode capacities, avoiding problems such as lithium dendrites during the battery charging and discharging process, and extending the cycle life.

[0062] In one embodiment of the present application, both ends of the positive electrode sheet are provided with empty foil areas, which are covered with heat-resistant insulating adhesive tape 6, and / or both ends of the negative electrode sheet are provided with empty foil areas, which are covered with heat-resistant insulating adhesive tape 6. When the battery cell is at high temperature, since the heat-resistant insulating adhesive tape 6 has good high temperature resistance, even if the isolation film undergoes thermal shrinkage, the empty foil areas of the positive electrode sheet and the negative electrode sheet will not directly contact each other, resulting in a short circuit of the battery, which effectively improves the safety performance of the battery; in addition, the provision of the heat-resistant insulating adhesive tape 6 is also conducive to preventing dust pollution and has an anti-corrosion function, which can effectively protect the stability and life of the battery cell.

[0063] like Figure 6 As shown, according to the second aspect of the present application, the present invention also provides a method for manufacturing the above-mentioned battery electrode sheet, comprising the following steps:

[0064] 1) using a double-cavity coating die head to coat the active material layer 2 slurry on at least one surface of the current collector 1;

[0065] 2) One of the material chambers applies the active material layer 2 slurry on the surface of the current collector 1 by continuous coating to form a first coating layer 100 having a complete coating area;

[0066] 3) another material chamber applies the active material layer 2 slurry to the gap portion adjacent to the first coating layer 100 by intermittent coating to form a second coating layer 200 having alternating coating areas and blank areas 300;

[0067] 4) Cutting along the edge close to the blank area 300 to obtain a single electrode piece containing both the first coating layer 100 and the second coating layer 200;

[0068] 5) Welding the pole ear 4 in the blank area 300 and covering it with heat-resistant insulating tape 6 to obtain the battery pole piece.

[0069] The manufacturing method of the pole piece provided by the present invention adopts a dual-cavity coating die head in combination with a continuous + intermittent coating method, and can prepare a pole piece containing both a complete coating area and a blank area 300 in a single coating process. The process is simple and efficient, and it is easy to realize the design of the pole lug groove 3 without the need for laser cleaning. In addition, by reserving a certain width at the edge of the blank area 300 for cutting, the thinning area of ​​the coating layer can be removed, thereby avoiding the problem of lithium deposition during the use of the pole piece and improving the pole piece quality and battery performance.

[0070] In one embodiment of the present application, in step 4), the cutting line is located in the first coating layer, and the distance between the edge of the blank area 300 and the cutting line is 1 to 10 mm. This coating process is prone to thinning of the coating thickness on both sides of the blank area 300. If the cutting is performed directly at the edge of the blank area 300, it is easy to cause lithium deposition in the thinned area at the edge of the pole piece. Therefore, when cutting, the thinned part of the second coating layer 200 close to the blank area 300 is cut 1 to 10 mm to the blank area 300, so as to avoid lithium deposition in the thin area of ​​the pole piece. In addition, it should be noted that the second coating layer 200 cut to the blank area 300 can be cut off and then welded to the pole lug 4, or the pole lug 4 can be directly welded without cutting.

[0071] According to the third aspect of the present application, the present invention further provides a secondary battery, comprising the battery pole piece described in any of the above paragraphs or the battery pole piece made by the method for making the battery pole piece described in any of the above paragraphs. The battery pole piece of the present invention is applied to a secondary battery to obtain a battery product with high energy density, excellent rate performance and reliable safety performance.

[0072] In one embodiment of the present application, the secondary battery is a lithium-ion battery, including a winding core, an electrolyte, and a soft-pack shell, the winding core includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet, the separator, and the negative electrode sheet are sequentially stacked and wound to form a winding core, and the winding core and the electrolyte are sealed together inside the shell. Among them, the positive electrode sheet and the negative electrode sheet are both the above-mentioned electrode sheets.

[0073] In one embodiment of the present application, the outer surface of the secondary battery is covered with a thermally conductive material layer, which can further improve the thermal conductivity and heat dissipation performance of the battery, suppress the temperature rise of the battery, and improve the reliability of use.

[0074] In order to further illustrate the implementation and advantages of the technical solution of the present invention, specific embodiments and comparative examples are provided below.

[0075] Example 1

[0076] Preparation of positive electrode:

[0077] The positive electrode plate includes an aluminum foil current collector and a positive electrode active material layer arranged on both sides of the aluminum foil current collector; a pole ear groove with a width of 8mm and a length of 20mm is arranged in the middle of the pole plate, and the pole ear groove is a non-through groove along the Y direction (the width direction of the pole plate). An aluminum pole ear is arranged in the pole ear groove, and the pole ear width is 7mm, including a connecting section located inside the pole plate and an exposed section located outside the pole plate.

[0078] The tab slot is covered with heat-resistant insulating tape, covering the connection section of the tab. The heat-resistant insulating tape used is a polyimide (PI) substrate with an acrylic adhesive coated on the surface, and the heat-resistant temperature is 150°C. The area of ​​the heat-resistant insulating tape accounts for 100% of the forward projection area of ​​the tab slot.

[0079] The exposed section of the tab is provided with tab glue; along the Y direction, the distance between the upper edge of the heat-resistant insulating tape and the lower edge of the tab glue is 0.5 mm. The connecting section of the tab is also covered with a thermally conductive silicone layer to improve the thermal conductivity and heat dissipation performance of the tab.

[0080] Among them, the positive electrode active material layer is a mixture of positive electrode active material lithium nickel cobalt manganese oxide, conductive agent conductive carbon black, and binder polyvinylidene fluoride in a mass ratio of 95:2:3; the surface density of the positive electrode active material layer is 22mg / cm².

[0081] Empty foil areas with a width of 15 mm are provided at both ends of the pole piece, and the empty foil areas are covered with heat-resistant insulating adhesive tape.

[0082] The preparation method of the positive electrode sheet is as follows:

[0083] 1) A double-cavity coating die is used to coat the positive electrode active material layer slurry on both surfaces of the aluminum foil current collector;

[0084] 2) One of the material chambers applies the positive electrode active material layer slurry on the surface of the current collector by continuous coating to form a first coating layer with a complete coating area;

[0085] 3) another material chamber applies the positive electrode active material layer slurry to the gap portion adjacent to the first coating layer by intermittent coating to form a second coating layer having alternating coating areas and blank areas;

[0086] 4) After drying, cutting is performed along the edge close to the blank area, and the cutting line is located in the first coating layer, wherein the distance between the edge of the blank area and the cutting line is 5 mm, to obtain a single electrode sheet containing both the first coating layer and the second coating layer;

[0087] 5) Welding the positive electrode tabs in the blank area and covering them with heat-resistant insulating tape to obtain the positive electrode sheet.

[0088] Preparation of negative electrode sheet:

[0089] The negative electrode plate includes a copper foil current collector and a negative electrode active material layer arranged on both sides of the copper foil current collector. A pole ear groove with a width of 10 mm and a length of 22 mm is arranged in the middle of the pole plate, and the pole ear groove is a non-through groove along the Y direction. A nickel pole ear is arranged in the pole ear groove, and the pole ear width is 9 mm, including a connecting section located inside the pole plate and an exposed section located outside the pole plate.

[0090] The tab slot is covered with heat-resistant insulating tape, covering the connection section of the tab. The heat-resistant insulating tape used is a polyetheretherketone (PEEK) substrate, with a silicone adhesive coated on the surface, and a heat-resistant temperature of 180°C. The area of ​​the heat-resistant insulating tape accounts for 110% of the forward projection area of ​​the tab slot.

[0091] The exposed section of the pole ear is provided with pole ear glue. Along the Y direction, the distance between the upper edge of the heat-resistant insulating adhesive paper and the lower edge of the pole ear glue is 1 mm.

[0092] The connecting section of the tab is also covered with a graphene thermal conductive layer to improve the thermal conductivity and heat dissipation performance of the tab.

[0093] Among them, the negative electrode active material layer is a mixture of hard carbon, carbon black and carboxymethyl cellulose in a mass ratio of 95:2:3; the surface density of the negative electrode active material layer is 8 mg / cm².

[0094] Empty foil areas with a width of 12 mm are provided at both ends of the pole piece, and the empty foil areas are covered with heat-resistant insulating adhesive tape.

[0095] The preparation method of the negative electrode sheet is as follows:

[0096] 1) A double-cavity coating die is used to coat the negative electrode active material layer slurry on both surfaces of the copper foil current collector;

[0097] 2) One of the material chambers coats the negative electrode active material layer slurry on the surface of the current collector by continuous coating to form a first coating layer with a complete coating area;

[0098] 3) another material chamber applies the negative electrode active material layer slurry to the gap portion adjacent to the first coating layer by intermittent coating to form a second coating layer having alternating coating areas and blank areas;

[0099] 4) After drying, cutting is performed along the edge close to the blank area, and the cutting line is located in the first coating layer, wherein the distance between the edge of the blank area and the cutting line is 7 mm, to obtain a single electrode sheet containing both the first coating layer and the second coating layer;

[0100] 5) Welding the negative electrode tabs in the blank area and covering them with heat-resistant insulating tape to obtain the negative electrode sheet.

[0101] Preparation of lithium-ion batteries:

[0102] The above-mentioned positive electrode sheet, negative electrode sheet and PP separator are used to make a soft-pack battery; wherein, the position where the positive electrode sheet and the negative electrode ear are opposite to each other is covered with heat-resistant insulating tape, and the outer surface of the battery is covered with a thermal conductive silicone layer.

[0103] Comparative Example 1

[0104] Different from Example 1, the positive electrode sheet of this comparative example adopts the traditional through-hollow foil area (through-ear tab groove) design to make the positive electrode sheet, and the negative electrode sheet adopts the traditional through-hollow foil area (through-ear tab groove) design to make the negative electrode sheet.

[0105] The rest is the same as in Example 1 and will not be described again here.

[0106] The following electrochemical performance tests were performed on the lithium ion batteries prepared in the examples and comparative examples, respectively. The test results are shown in Table 1.

[0107] 1. Energy density test: The prepared battery was charged and discharged three times at 0.2C current at 25°C, and the discharge capacity of the battery was measured; the volume energy density (Wh / L) was calculated based on the volume of the battery.

[0108] 2. Internal resistance test: Use the AC impedance method to measure the AC impedance value at a frequency of 1kHz when the battery is in the 50% SOC state.

[0109] 3. Rate performance test: At 25°C, discharge at rates of 0.2C, 0.5C, 1C, 2C and 5C respectively, and record the discharge capacity retention rate at each rate (relative to 0.2C capacity).

[0110] Table 1

[0111] The test results of Table 1 above are analyzed as follows:

[0112] 1) Energy density: The energy density of Example 1 is higher than that of Comparative Example 1, which is mainly due to the non-through lug slot design adopted in the present invention, which increases the coating area of ​​the active material and improves the space utilization.

[0113] 2) Internal resistance: The internal resistance of Example 1 is lower than that of Comparative Example 1. This is because the middle pole ear design of the present invention shortens the average transmission distance of the current in the pole piece, and the more uniform current distribution further reduces the internal resistance.

[0114] 3) Rate performance: The capacity retention rate of Example 1 at each rate is better than that of Comparative Example 1, especially at high rates, the advantage is more obvious. This shows that the design of the present invention not only reduces the internal resistance, but also improves the current distribution, reduces the risk of local overload, and thus improves the performance at high rates.

[0115] In summary, the battery pole piece design provided by the present invention significantly improves the space utilization of the battery and improves the current distribution by adopting non-through pole ear grooves and middle pole ear settings. Experimental results show that this design not only improves the energy density of the battery, but also reduces the internal resistance and improves the rate performance. Especially under high-rate charge and discharge conditions, the advantages of the present invention are more obvious, which is of great significance for application scenarios that require fast charge and discharge (such as electric vehicles, portable electronic devices, etc.).

[0116] It should be noted that the contents not described in detail in this specification belong to the prior art known to professional and technical personnel in the field and will not be repeated here.

[0117] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs can also change and modify the above embodiment. Therefore, the present invention is not limited to the above specific embodiment, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention belongs to the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A battery pole piece, characterized in that: It includes a current collector and an active material layer arranged on at least one surface of the current collector; a pole lug groove is arranged in the middle of the pole piece, the pole lug groove is a non-through groove along the Y direction, the pole lug groove is provided with a pole lug, and the pole lug includes a connecting section located inside the pole piece and an exposed section located outside the pole piece.

2. The battery pole piece according to claim 1, characterized in that: The tab slot is covered with heat-resistant insulating tape, and the heat-resistant insulating tape covers the connecting section of the tab; the area of ​​the heat-resistant insulating tape accounts for 30-200% of the forward projection area of ​​the tab slot; the heat-resistant insulating tape has a heat-resistant temperature of ≥130°C.

3. The battery pole piece according to claim 2, characterized in that: The exposed section of the pole ear is provided with pole ear glue; along the Y direction, the absolute value of the distance between the upper edge of the heat-resistant insulating tape and the lower edge of the pole ear glue is 0.1-2 mm.

4. The battery pole piece according to claim 1, characterized in that: The connecting section of the tab is also covered with a heat conducting material layer.

5. The battery pole piece according to claim 1, characterized in that: The width of the pole ear accounts for 30-100% of the width of the pole ear groove.

6. The battery pole piece according to claim 1, characterized in that: The length of the pole lug groove accounts for 10-90% of the width of the pole piece.

7. The battery pole piece according to any one of claims 1 to 6, characterized in that: The current collector is a positive electrode current collector and / or a negative electrode current collector, the active material layer is a positive electrode active material layer and / or a negative electrode active material layer, the positive electrode active material layer is arranged on at least one surface of the positive electrode current collector, and the negative electrode active material layer is arranged on at least one surface of the negative electrode current collector; The electrode sheet is a positive electrode sheet and / or a negative electrode sheet, a positive electrode tab groove is provided in the middle of the positive electrode sheet, the positive electrode tab groove is a non-through groove along the Y direction, and the positive electrode tab groove is provided with a positive electrode tab; a negative electrode tab groove is provided in the middle of the negative electrode sheet, the negative electrode tab groove is a non-through groove along the Y direction, and the negative electrode tab groove is provided with a negative electrode tab; The position where the positive electrode plate is opposite to the negative electrode tab is covered with heat-resistant insulating adhesive tape; and / or, the position where the positive electrode plate is opposite to the negative electrode tab is provided with an empty foil area, and the empty foil area is covered with heat-resistant insulating adhesive tape.

8. A method for manufacturing a battery electrode according to any one of claims 1 to 7, characterized in that: The following steps are involved: 1) using a double-cavity coating die to coat the active material layer slurry on at least one surface of the current collector; 2) One of the material chambers applies the active material layer slurry on the surface of the current collector by continuous coating to form a first coating layer with a complete coating area; 3) another material chamber applies the active material layer slurry to the gap portion adjacent to the first coating layer by intermittent coating to form a second coating layer having alternating coating areas and blank areas; 4) Cutting along the edge close to the blank area to obtain a single electrode sheet containing both the first coating layer and the second coating layer; 5) Welding the electrode lugs in the blank area to obtain the battery electrode sheet.

9. The method for manufacturing a battery electrode according to claim 8, characterized in that: In step 4), the cutting line is located on the first coating layer, and the distance between the edge of the blank area and the cutting line is 1-10 mm.

10. A secondary battery, characterized in that: A battery pole sheet comprising the battery pole sheet as described in any one of claims 1 to 7 or a battery pole sheet manufactured by the manufacturing method of the battery pole sheet as described in any one of claims 8 to 9.

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