Battery pole piece and secondary battery

Abstract

The utility model discloses a battery pole piece 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 active material can be coated on the peripheral area of the tab, and the space utilization rate of the pole piece is remarkably improved, so that more active substances can be accommodated under the same volume; the battery energy density 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 utility model belongs to secondary battery technical field, especially relate to a battery pole piece and secondary battery. BACKGROUND

[0002] Lithium-ion batteries, as a high-efficiency energy storage device, are widely used in portable electronic devices, electric vehicles, and renewable energy storage. With the increasing demand for high energy density, high rate performance, and low internal resistance batteries, battery manufacturers have been seeking ways to optimize battery structure and manufacturing processes.

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

[0004] To improve current distribution and optimize battery performance, some manufacturers have begun to try to weld the tab at the middle of the pole piece. This design can more evenly distribute the current, helping to improve the rate performance of the battery and reduce the internal resistance. However, this improvement also brings new challenges.

[0005] Limited by existing production processes, manufacturers usually use a direct jump gap method to achieve the welding of the middle tab. This method forms a through-foil area in the tab position, i.e., an area without active material coating. Although this through-foil area facilitates the welding of the tab, it also wastes internal space in the battery. This space waste not only reduces the energy density of the battery, but also may affect the overall performance of the battery.

[0006] In addition, the presence of the through-foil area may cause uneven current distribution, increasing the risk of local hot spots, thereby affecting 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, it is necessary to have a solution that can maximize the use of pole piece space while maintaining the advantages of the middle tab design, allowing for the maximum increase in active material coating area without affecting the welding of the tab, thereby increasing the energy density of the battery, improving the rate performance, and reducing the internal resistance. SUMMARY

[0008] The utility model discloses to solve the technical problem that the prior art has, and the purpose is: a battery pole piece with high space utilization, which can reduce internal resistance and improve rate performance while increasing the energy density of the battery.

[0009] To achieve the above-mentioned purpose, the utility model provides the following technical scheme:

[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 middle part of the pole piece is provided with a tab slot, the tab slot is a non-through slot along the Y direction, the tab slot is provided with a tab, the tab comprises a connecting section located in the pole piece and an exposed section located outside the pole piece.

[0011] Preferably, the tab slot is attached with a temperature-resistant insulating adhesive tape, and the temperature-resistant insulating adhesive tape covers the connecting section of the tab; the area of the temperature-resistant insulating adhesive tape accounts for 30-200% of the area of the normal projection of the tab slot; the heat-resistant temperature of the temperature-resistant insulating adhesive tape is ≥ 130℃.

[0012] Preferably, the temperature-resistant insulating adhesive tape comprises a substrate and an adhesive layer arranged 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 vinyl acetate adhesive, a nitrile rubber adhesive or a chloroprene rubber adhesive. Among them, the temperature-resistant insulating adhesive tapes of the above-mentioned materials all have good high-temperature resistance and insulation performance; in addition, it should be noted that other materials of temperature-resistant insulating adhesive tapes can also be used as long as they can meet the corresponding temperature resistance and insulation requirements.

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

[0014] Preferably, the connecting section of the tab is also attached with a layer of heat-conducting material. The heat-conducting material is at least one of heat-conducting silicone, graphene, carbon nanotube and phase change material, wherein the phase change material is preferably a solid-solid phase change material, such as polyethylene glycol. By arranging the layer of heat-conducting material, the heat-conducting and heat-dissipating performance of the tab can be improved.

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

[0016] Preferably, the width of the tab slot is 3-20mm, and more preferably 6-15mm.

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

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

[0019] Preferably, both ends of the pole piece are provided with empty foil areas, and the empty foil areas are attached with temperature-resistant insulating adhesive tapes.

[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 pole piece is a positive pole piece and / or a negative pole piece, a positive pole lug groove is arranged in the middle of the positive pole piece, the positive pole lug groove is a non-through groove along the Y direction, and the positive pole lug groove is provided with a positive pole lug; a negative pole lug groove is arranged in the middle of the negative pole piece, the negative pole lug groove is a non-through groove along the Y direction, and the negative pole lug groove is provided with a negative pole lug.

[0022] The positive pole piece is opposite to the negative pole lug, and a temperature-resistant insulating adhesive tape is attached to the position; and / or, the positive pole piece is opposite to the negative pole lug, and an empty foil area is arranged, and the empty foil area is attached with a temperature-resistant insulating adhesive tape.

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

[0024] Preferably, the two ends of the positive pole piece are provided with an empty foil area, and the empty foil area is attached with a temperature-resistant insulating adhesive tape; and / or, the two ends of the negative pole piece are provided with an empty foil area, and the empty foil area is attached with a temperature-resistant insulating adhesive tape.

[0025] In addition, the utility model also provides a secondary battery, including the battery pole piece of any one of the above.

[0026] Preferably, the outer surface of the secondary battery is attached with a heat-conducting material layer; the heat-conducting and heat-dissipating performance of the battery can be improved.

[0027] Compared with the prior art, the utility model has at least the following beneficial effects:

[0028] 1) The battery energy density can be effectively improved: compared with the traditional through empty foil area design, the utility model sets a non-through lug groove in the middle of the pole piece, and sets the lug in it, which can also coat active material in the lug surrounding area, significantly improves the space utilization rate of the pole piece, and can accommodate more active substances under the same volume, effectively improves the battery energy density.

[0029] 2) reduce the battery resistance, improve the rate performance: the middle of the tab design itself is conducive to reducing the battery resistance, because it shortens the average transmission distance of the current in the pole piece; at the same time, because the utility model increases the coating area of active material, the current distribution is more uniform, further reduces the internal resistance, improves the rate performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is the structural schematic diagram of the battery pole piece of an embodiment of the utility model;

[0031] Figure 2 It is the top view of the positive pole piece of an embodiment of the utility model;

[0032] Figure 3 It is the sectional schematic view of the positive pole piece of an embodiment of the utility model;

[0033] Figure 4 It is the top view of the negative pole piece of an embodiment of the utility model;

[0034] Figure 5 It is the sectional schematic view of the negative pole piece of an embodiment of the utility model;

[0035] Figure 6 It is the structural schematic diagram of the battery pole piece before slitting of an embodiment of the utility model.

[0036] In the figure: 1, current collector; 2, active material layer; 3, tab slot; 4, tab; 5, tab glue; 6, temperature-resistant insulating rubber paper; 11, positive current collector; 12, negative current collector; 21, positive active material layer; 22, negative active material layer; 31, positive tab slot; 32, negative tab slot; 41, positive tab; 42, negative tab; 100, first coating layer; 200, second coating layer; 300, blank area. DETAILED DESCRIPTION

[0037] The technical scheme in the embodiments of the utility model will be described clearly and completely below in conjunction with the drawings in the embodiments of the utility model, obviously, the described embodiments are only part of the embodiments of the utility model, not all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by the person skilled in the art without creative labor are within the protection scope of the utility model.

[0038] In the description of the present application, unless otherwise explicitly specified and limited, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance; the term "multiple" refers to two or more than two; unless otherwise specified or stated, the terms "connection", "fixation" and the like should be broadly understood, for example, "connection" can be fixed connection, or detachable connection, or integrally connected, or electrically connected; "connection" can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0039] Please refer to the accompanying Figure 1 According to the first aspect of the present application, the battery pole piece provided by the present application comprises a current collector 1 and an active material layer 2 arranged on at least one surface of the current collector 1; the middle part of the pole piece is provided with a tab slot 3 which is a non-through slot along the Y direction, and the tab slot 3 is provided with a tab 4 which comprises a connecting section located in the pole piece and an exposed section located outside the pole piece.

[0040] Among them, the battery pole piece provided by the utility model, through setting non-through tab slot 3 in the middle part of the pole piece and setting tab 4 therein, can significantly improve the space utilization rate of the pole piece. Compared with the traditional pole piece with tabs arranged at the edge or in the middle part, the structural design of the non-through middle tab of the utility model avoids the waste of space outside the tab welding area of the pole piece, so that more active substances 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 tab can also shorten the electron transport path, reduce the in-plane resistance of the pole piece, and improve the large-rate charge and discharge performance.

[0041] In an embodiment according to the present application, the tab slot 3 is pasted with a temperature-resistant insulating adhesive tape 6, and the temperature-resistant insulating adhesive tape 6 covers the connecting section of the tab 4, thereby increasing the safety of the battery cell and preventing short circuit; the area of the temperature-resistant insulating adhesive tape 6 accounts for 30-200% of the normal projection area of the tab slot 3; the heat-resistant temperature of the temperature-resistant insulating adhesive tape 6 is greater than or equal to 130 DEG C. Preferably, the area of the temperature-resistant insulating adhesive tape 6 accounts for 100-150% of the normal projection area of the tab slot 3; the direct contact between the positive and negative electrodes caused by the thermal shrinkage of the isolation film can be effectively avoided, and the edge burrs of the current collector 1 and the tab 4 can also be effectively covered, thereby preventing the occurrence of short circuit of the battery cell and improving the safety of the battery cell. Preferably, the heat-resistant temperature of the temperature-resistant insulating adhesive tape 6 is 130 DEG C-500 DEG C; generally speaking, the higher the heat-resistant temperature of the temperature-resistant insulating adhesive tape 6, the better, and in order to improve the safety of the battery cell, the heat-resistant temperature of the temperature-resistant insulating adhesive tape 6 is generally higher than the thermal shrinkage temperature of the isolation film.

[0042] In an embodiment according to the application, the temperature-resistant insulating adhesive paper 6 comprises 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-vinyl acetate adhesive, a butyronitrile rubber adhesive or a chloroprene rubber adhesive. The temperature-resistant insulating adhesive paper 6 made of the above-mentioned materials has good high-temperature resistance and insulation performance. In addition, it should be noted that other materials can also be used for the temperature-resistant insulating adhesive paper 6 as long as the corresponding temperature resistance and insulation requirements are met.

[0043] In an embodiment according to the application, the exposed section of the tab 4 is provided with a tab adhesive 5; the absolute value of the distance between the upper edge of the temperature-resistant insulating adhesive paper 6 and the lower edge of the tab adhesive 5 in the Y direction is 0.1-2 mm. In this way, the temperature-resistant insulating adhesive paper 6 can cover the burrs on the edges of the tab 4, avoid the size of the adhesive paper affecting the top sealing of the aluminum plastic film, and reduce the waste of the adhesive paper.

[0044] In an embodiment according to the application, the connecting section of the tab 4 is also coated with a layer of heat-conducting material. The heat-conducting material is at least one of heat-conducting silicone, graphene, carbon nanotube and phase change material, wherein the phase change material is preferably a solid-solid phase change material, such as polyethylene glycol. By providing a layer of heat-conducting material, the heat conduction at the tab 4 can be accelerated, the local temperature rise can be reduced, and the heat dissipation performance and safety of the tab can be improved. The heat-conducting coefficient of heat-conducting silicone, graphene and carbon nanotube is high, and the phase change material can absorb excess heat at the tab 4, which can significantly improve the heat conduction and dissipation performance of the tab 4.

[0045] In an embodiment according to the application, the width of the tab 4 accounts for 30-100% of the width of the tab slot 3; further preferably, 85-100%. Optimizing the ratio of the width of the tab 4 to the width of the tab slot 3 can minimize the occupation of the active material area by the tab slot 3 while ensuring the welding reliability of the tab 4, improve the energy density while ensuring the mechanical strength and structural integrity of the tab.

[0046] In an embodiment according to the application, the width of the tab slot 3 is 3-20 mm, and further preferably 6-15 mm. For example, it can be 6 mm, 8 mm, 10 mm or 12 mm, etc.

[0047] In an embodiment according to the application, the length of the tab slot 3 accounts for 20-60% of the width of the tab. Optimizing the ratio of the length of the tab slot 3 to the width of the tab can minimize the occupation of the active material area by the tab slot 3 while ensuring the welding reliability of the tab 4, improve the energy density while ensuring the mechanical strength and structural integrity of the tab.

[0048] In an embodiment according to the application, the length of the tab slot 3 is 10-100 mm, further preferably 15-50 mm. For example, it can be 15 mm, 18 mm, 20 mm, 22 mm or 25 mm, etc.

[0049] In an embodiment according to the application, the two ends of the tab are provided with a hollow foil area, and the hollow foil area is attached with a temperature-resistant insulating tape 6. When the battery cell is in a high-temperature condition, since the temperature-resistant insulating tape 6 has good high-temperature resistance, even if the isolation film shrinks due to heat, the phenomenon of direct contact between the hollow foil areas of the positive tab and the negative tab causing the battery to short circuit will not occur, effectively improving the safety performance of the battery; in addition, the setting of the temperature-resistant insulating tape 6 is also beneficial to prevent dust pollution and has a corrosion prevention function, which can effectively protect the stability and service life of the battery cell.

[0050] In an embodiment according to the application, as shown in Figures 2-5 the current collector 1 is a positive current collector 11 and / or a negative current collector 12, the active material layer 2 is a positive active material layer 21 and / or a negative active material layer 22, the positive active material layer 21 is arranged on at least one surface of the positive current collector 11, and the negative active material layer 22 is arranged on at least one surface of the negative current collector 12;

[0051] The tab is a positive tab and / or a negative tab, the middle part of the positive tab is provided with a positive tab slot 31, the positive tab slot 31 is a non-through slot along the Y direction, and the positive tab slot 31 is provided with a positive tab 41; the middle part of the negative tab is provided with a negative tab slot 32, the negative tab slot 32 is a non-through slot along the Y direction, and the negative tab slot 32 is provided with a negative tab 42;

[0052] The position opposite to the negative tab 42 of the positive tab is attached with a temperature-resistant insulating tape 6; and / or, the position opposite to the negative tab 42 of the positive tab is provided with a hollow foil area, and the hollow foil area is attached with a temperature-resistant insulating tape 6. By attaching the temperature-resistant insulating tape 6 at the position opposite to the negative tab of the positive tab, the edge burr of the negative tab can be effectively prevented from damaging the positive tab or causing negative lithium precipitation due to uneven thickness; in addition, when the battery cell is in a high-temperature condition, since the temperature-resistant insulating tape 6 has good high-temperature resistance, even if the isolation film shrinks due to heat, the phenomenon of direct contact between the positive tab and the negative tab causing the battery to short circuit will not occur, effectively improving the safety performance of the battery.

[0053] 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. 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 microcarbon beads, hard carbon, soft carbon, silicon, silicon-carbon materials, etc.; the conductive agent may include, but is not limited to, conductive carbon black, acetylene black, Ketjen black, carbon nanofibers, carbon nanotubes, graphene, etc.; and the binder may include, but is not limited to, polyvinylidene fluoride, styrene-butadiene rubber, polyvinyl alcohol, polyurethane, etc. The proportioning and preparation of the active material layer slurry are conventional techniques in the art and will not be described in detail here.

[0054] 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 5-15 mg / cm 2 , more preferably 5~12 mg / cm 2 By properly matching the surface densities of the positive and negative active material layers 22, it is possible to improve energy density while also matching the positive and negative electrode capacities, thereby avoiding problems such as lithium dendrites during battery charge and discharge, and extending cycle life.

[0055] In one embodiment of the present application, hollow foil areas are provided at both ends of the positive electrode sheet, and the hollow foil areas are covered with heat-resistant insulating tape 6, and / or hollow foil areas are provided at both ends of the negative electrode sheet, and the hollow foil areas are covered with heat-resistant insulating tape 6. When the battery cell is exposed to high temperatures, because the heat-resistant insulating tape 6 has excellent high-temperature resistance, even if the separator undergoes thermal contraction, direct contact between the hollow foil areas of the positive and negative electrode sheets will not occur, causing a short circuit in the battery, thereby effectively improving the safety of the battery. In addition, the provision of the heat-resistant insulating tape 6 also helps prevent dust contamination and has anti-corrosion functions, which can effectively protect the stability and life of the battery cell.

[0056] like Figure 6 As shown, according to the second aspect of the present application, the present invention further provides a method for manufacturing the above-mentioned battery electrode sheet, comprising the following steps:

[0057] 1) Using a dual-cavity coating die head, the active material layer 2 slurry is coated on at least one surface of the current collector 1;

[0058] 2) One of the material chambers applies the active material layer 2 slurry to the surface of the current collector 1 by continuous coating to form a first coating layer 100 having a complete coating area;

[0059] 3) Another material cavity is used to coat the active material layer 2 slurry in the gap part adjacent to the first coating layer 100 by intermittent coating to form a second coating layer 200 with coating areas and blank areas 300 alternating;

[0060] 4) Cutting along the edge close to the blank area 300 to obtain a single pole piece containing both the first coating layer 100 and the second coating layer 200;

[0061] 5) Welding the pole lug 4 at the blank area 300 and pasting the temperature-resistant insulating tape 6, thereby obtaining the battery pole piece.

[0062] The manufacturing method of the pole piece provided by the utility model adopts the mode of double-cavity coating die cooperating with continuous + intermittent coating, can prepare the pole piece containing complete coating areas and blank areas 300 at one time, is simple and efficient in process, easy to realize the design of the pole lug groove 3, and does not need laser cleaning. In addition, cutting a certain width at the edge of the blank area 300 can remove the thinned area of the coating layer, avoid lithium precipitation in the pole piece during use, and improve the pole piece quality and battery performance.

[0063] In an embodiment according to the application, in step 4), the cutting line is located at the edge of the first coating layer, and the distance between the blank area 300 and the cutting line is 1-10 mm. The coating process is prone to thinned coating thickness on both sides of the blank area 300, and if cutting is directly performed at the edge of the blank area 300, lithium precipitation in the thinned area of the pole piece edge is easy to occur. Therefore, when cutting, the thinned part of the second coating layer 200 close to the blank area 300 is cut to the blank area 300 by 1-10 mm, so that lithium precipitation in the thinned area of the pole piece can be avoided. 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 with the pole lug 4, or can be directly welded with the pole lug 4 without cutting off.

[0064] According to a third aspect of the application, the utility model also provides a secondary battery, which comprises the battery pole piece described in any of the above paragraphs or the battery pole piece prepared by the manufacturing method of the battery pole piece described in any of the above paragraphs. The battery pole piece of the utility model is applied to the secondary battery, so that a battery product with high energy density, excellent rate performance and reliable safety performance can be obtained.

[0065] In an embodiment according to the application, the secondary battery is a lithium ion battery, which comprises a roll core, an electrolyte and a soft package shell, the roll core comprises a positive pole piece, a negative pole piece and a separator arranged between the positive pole piece and the negative pole piece, the positive pole piece, the separator and the negative pole piece are sequentially laminated and wound to form the roll core, and the roll core and the electrolyte are jointly sealed in the shell. Among them, the positive pole piece and the negative pole piece are both the above-mentioned electrode pieces.

[0066] In an embodiment according to the application, a layer of heat-conductive material is attached to the outer surface of the secondary battery; the heat-conductive and heat-dissipating performance of the battery can be further improved, the temperature rise of the battery is inhibited, and the use reliability is improved.

[0067] In order to further illustrate the implementation and advantages of the technical scheme of the utility model, the following specific examples and comparative examples are described.

[0068] Example 1

[0069] Preparation of the positive electrode tab:

[0070] The positive electrode tab includes an aluminum foil current collector and a positive active material layer arranged on both surfaces of the aluminum foil current collector; a tab slot with a width of 8 mm and a length of 20 mm is arranged in the middle of the tab, and the tab slot is a non-through slot along the Y direction (the width direction of the tab). An aluminum tab is arranged in the tab slot, and the width of the tab is 7 mm, including a connecting section inside the tab and an exposed section outside the tab.

[0071] The tab slot is attached with a temperature-resistant insulating paper covering the connecting section of the tab. The temperature-resistant insulating paper used is a polyimide (PI) substrate coated with an acrylic adhesive on the surface, and the heat-resistant temperature is 150℃. The area of the temperature-resistant insulating paper accounts for 100% of the positive projection area of the tab slot.

[0072] The exposed section of the tab is provided with a tab adhesive; along the Y direction, the distance between the upper edge of the temperature-resistant insulating paper and the lower edge of the tab adhesive is 0.5 mm. The connecting section of the tab is also attached with a heat-conductive silicone layer to improve the heat-conductive and heat-dissipating performance of the tab.

[0073] The positive active material layer is a mixture of positive 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 active material layer is 22 mg / cm².

[0074] The two ends of the tab are provided with an empty foil area with a width of 15 mm, and the empty foil area is attached with a temperature-resistant insulating paper.

[0075] The preparation method of the positive electrode tab is as follows:

[0076] 1) A double-chamber coating die is used to coat the positive active material layer slurry on both surfaces of the aluminum foil current collector;

[0077] 2) One of the chambers coats the positive 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;

[0078] 3) Another material cavity forms a second coating layer with coating and blank areas alternating by intermittent coating of the positive active material layer slurry in the gap part adjacent to the first coating layer;

[0079] 4) After drying, slitting is performed along the edge close to the blank area, and the slitting line is located in the first coating layer, wherein the distance between the edge of the blank area and the slitting line is 5 mm, to obtain a single pole piece containing the first coating layer and the second coating layer;

[0080] 5) The positive pole lug is welded in the blank area, and the temperature-resistant insulating adhesive tape is attached, to obtain the positive pole piece.

[0081] Preparation of the negative pole piece:

[0082] The negative pole piece includes a copper foil current collector and a negative active material layer arranged on both surfaces of the copper foil current collector. A pole lug groove with a width of 10 mm and a length of 22 mm is arranged in the middle of the pole piece, and the pole lug groove is a non-through groove along the Y direction. A nickel pole lug is arranged in the pole lug groove, and the pole lug has a width of 9 mm, including a connecting section located in the pole piece and an exposed section located outside the pole piece.

[0083] The pole lug groove is attached with a temperature-resistant insulating adhesive tape covering the connecting section of the pole lug. The temperature-resistant insulating adhesive tape used is a polyether ether ketone (PEEK) substrate coated with a silicone adhesive on the surface, and the heat-resistant temperature is 180℃. The area of the temperature-resistant insulating adhesive tape accounts for 110% of the positive projection area of the pole lug groove.

[0084] The exposed section of the pole lug is provided with a pole lug adhesive. Along the Y direction, the distance between the upper edge of the temperature-resistant insulating adhesive tape and the lower edge of the pole lug adhesive is 1 mm.

[0085] The connecting section of the pole lug is also attached with a graphene heat-conducting layer to improve the heat-conducting and heat-dissipating performance of the pole lug.

[0086] The negative active material layer is a mixture of hard carbon, carbon black and carboxymethyl cellulose in a mass ratio of 95:2:3; and the areal density of the negative active material layer is 8 mg / cm².

[0087] The pole piece is provided with a width of 12 mm at both ends of the pole piece, and the temperature-resistant insulating adhesive tape is attached to the empty foil area.

[0088] The preparation method of the negative pole piece is as follows:

[0089] 1) The negative active material layer slurry is coated on both surfaces of the copper foil current collector by using a double-cavity coating die;

[0090] 2) One of the material cavities forms a first coating layer with a complete coating area by continuously coating the negative active material layer slurry on the surface of the current collector;

[0091] 3) Another material cavity coats the negative active material layer slurry in the gap part adjacent to the first coating layer by intermittent coating to form a second coating layer with coating and blank areas alternating;

[0092] 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 pole piece containing the first coating layer and the second coating layer;

[0093] 5) The negative tab is welded in the blank area, and the temperature-resistant insulating adhesive tape is attached, to obtain the negative pole piece.

[0094] Preparation of a lithium ion battery:

[0095] A soft package battery is made using the above positive pole piece, negative pole piece, and PP separator; wherein the temperature-resistant insulating adhesive tape is attached to the position opposite to the negative tab of the positive pole piece, and the heat-conducting silicone layer is attached to the outer surface of the battery.

[0096] Comparative Example 1

[0097] Unlike Example 1, the positive pole piece of this comparative example is made using the traditional through-hole foil area (through-hole tab slot) design, and the negative pole piece is made using the traditional through-hole foil area (through-hole tab slot) design.

[0098] Other than Example 1, which is not described here.

[0099] The lithium ion batteries prepared in the examples and comparative examples are respectively subjected to the following electrochemical performance tests, and the test results are shown in Table 1.

[0100] 1. Energy density test: After 3 cycles of charging and discharging at 0.2C current in a 25℃ environment, the discharge capacity of the battery is measured; the volume energy density (Wh / L) is calculated according to the volume of the battery.

[0101] 2. Internal resistance test: Using the alternating current impedance method, the alternating current impedance value at 1 kHz frequency is measured under the condition of 50% SOC of the battery.

[0102] 3. Rate performance test: Discharge at 0.2C, 0.5C, 1C, 2C, and 5C rates respectively in a 25℃ environment, and record the discharge capacity retention rate (relative to 0.2C capacity) at each rate.

[0103] Table 1

[0104]

[0105] The test results of the above Table 1 are analyzed as follows:

[0106] 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 tab slot design adopted by the utility model, which increases the coating area of active materials and improves the space utilization.

[0107] 2) Internal resistance: the internal resistance of Example 1 is lower than that of Comparative Example 1, because the middle tab design of the utility model shortens the average transmission distance of current in the pole piece, and the more uniform current distribution further reduces the internal resistance.

[0108] 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 utility model not only reduces the internal resistance, but also improves the current distribution and reduces the risk of local overload, thereby improving the performance at high rates.

[0109] In summary, the battery pole piece design provided by the utility model significantly improves the space utilization of the battery by adopting non-through tab slot and middle tab design, and improves the current distribution. 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 the condition of high rate charging and discharging, the advantage of the utility model is more obvious, which is of great significance for application scenarios that require fast charging and discharging (such as electric vehicles, portable electronic devices, etc.).

[0110] It should be noted that the contents not described in detail in the specification belong to the existing technology known to those skilled in the art, which will not be described here.

[0111] According to the disclosure and teaching of the above description, those skilled in the art of the utility model can also make changes and modifications to the above embodiments. Therefore, the utility model is not limited to the above specific embodiments, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the utility model belongs to the protection scope of the utility model. In addition, although some specific terms are used in the specification, these terms are only for convenience of description and do not constitute any limitation on the utility model.

Claims

1. A battery pole piece, characterized by: The battery pole piece comprises a current collector and an active material layer arranged on at least one surface of the current collector; a middle part of the pole piece is provided with a pole tab slot which is a non-through slot along a Y direction, and the pole tab slot is provided with a pole tab comprising a connecting section located in the pole piece and an exposed section located outside the pole piece.

2. The battery pole piece of claim 1, wherein: The pole tab slot is attached with a temperature-resistant insulating adhesive tape, and the temperature-resistant insulating adhesive tape covers the connecting section of the pole tab; the area of the temperature-resistant insulating adhesive tape accounts for 30-200% of the area of the pole tab slot orthogonally projected; the heat-resistant temperature of the temperature-resistant insulating adhesive tape is greater than or equal to 130℃.

3. The battery pole piece of claim 2, wherein: The exposed section of the pole tab is provided with a pole tab adhesive; along the Y direction, the absolute value of the distance between the upper edge of the temperature-resistant insulating adhesive tape and the lower edge of the pole tab adhesive is 0.1-2mm.

4. The battery pole piece of claim 1, wherein: The connecting section of the pole tab is further attached with a layer of heat-conducting material.

5. The battery pole piece of claim 1, wherein: The width of the pole tab accounts for 30-100% of the width of the pole tab slot.

6. The battery pole piece of claim 1, wherein: The width of the pole tab slot is 3-20mm.

7. The battery pole piece of claim 1, wherein: The length of the pole tab slot accounts for 10-90% of the width of the pole tab.

8. The battery pole piece of claim 1, wherein: The length of the pole tab slot is 10-100mm.

9. The battery pole piece of any one of claims 1-8, wherein: The current collector is a positive current collector and / or a negative current collector, the active material layer is a positive active material layer and / or a negative active material layer, the positive active material layer is arranged on at least one surface of the positive current collector, and the negative active material layer is arranged on at least one surface of the negative current collector; The pole piece is a positive pole piece and / or a negative pole piece, a middle part of the positive pole piece is provided with a positive pole tab slot which is a non-through slot along a Y direction, and the positive pole tab slot is provided with a positive pole tab; a middle part of the negative pole piece is provided with a negative pole tab slot which is a non-through slot along a Y direction, and the negative pole tab slot is provided with a negative pole tab; The position opposite to the negative pole tab of the positive pole piece is attached with a temperature-resistant insulating adhesive tape; and / or, the position opposite to the negative pole tab of the positive pole piece is provided with an empty foil area, and the empty foil area is attached with a temperature-resistant insulating adhesive tape.

10. A secondary battery characterized by comprising: The battery pole piece comprises a current collector and an active material layer arranged on at least one surface of the current collector; a middle part of the pole piece is provided with a pole tab slot which is a non-through slot along a Y direction, and the pole tab slot is provided with a pole tab comprising a connecting section located in the pole piece and an exposed section located outside the pole piece.

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