High-power battery pole group

Abstract

The invention discloses a high-power battery pole group which is characterized in that a middle-section coating of a positive plate is made of a lithium-intercalated and de-intercalated high-rate discharge active material, an upper-section coating and a lower-section coating are made of materials with insulation and liquid absorption capabilities, and the liquid absorption capability of the lower-section coating is greater than that of the upper-section coating; the negative plate upper-section coating is an active material for bearing rapid embedding of lithium ions, and the negative plate lower-section coating is a porous liquid absorption layer formed by an active material which contains a large-particle-size main body material and has rapid liquid absorption capability; the diaphragm upper-section coating and the diaphragm lower-section coating are made of a ceramic material which has liquid absorbing and retaining capabilities and can expand after absorbing liquid to fill a gap between a positive electrode and a negative electrode at the top end, the diaphragm middle-section coating does not have the liquid absorbing capability, and the porosity of a base membrane on which the diaphragm lower-section coating is positioned is greater than that of the base membrane of the middle-section coating and the upper-section coating. According to the invention, the problems of structural lithium precipitation and imbibition lithium precipitation are solved, and the service life of the high-power battery cell is guaranteed in all directions.

Description

Technical Field

[0001] The invention relates to the technical field of high-rate battery cells, and in particular to a high-power battery electrode group. Background Art

[0002] High-rate batteries are currently the key application products for automobiles and consumer products. The main principle is the rapid deintercalation and transfer of lithium ions in active materials and media, thereby forming power output to the outside. The life of high-rate batteries is affected by the system, structure, liquid absorption and other aspects. Among them, system design, structural lithium precipitation and less electrolyte or poor electrolyte wetting are the key factors in battery cell design. The system and materials need to support the rapid deintercalation of lithium ions; the structure needs to maintain a small gap between the pole pieces to avoid polarization; the infiltration of the electrolyte is not only affected by the specific surface area of ​​the active material and the coating and compaction, but also by the structure and layout inside the battery cell. The siphoning of the electrolyte will be affected by the structure.

[0003] Chinese patent CN217158275U discloses a high-capacity and high-rate battery, including a shell, a cap seal ring is installed on the inner side of the shell near the top, a cap top cover is installed on the inner side of the cap seal ring, wherein a CID is arranged below the top cover, the CID is installed on the inner side of the cap seal ring through a safety valve sheet, a breathable plate is arranged below the CID, a breathable hole is opened on the breathable plate, and a gasket is installed inside the shell near the bottom of the breathable plate. This patented technology can effectively improve the capacity and rate of the battery through a positive electrode sheet made of high-nickel system materials and a negative electrode sheet made of a composite of artificial graphite and natural graphite, and reduce the internal resistance through two negative ears, and support high-rate discharge, so that the battery can reach 3.0.Ah, a long-term continuous discharge rate of 15A, and an instantaneous discharge rate of 20A, so that the battery can have high capacity and high rate performance.

[0004] Chinese patent CN118281289A discloses a high-rate fast-charging and high-safety battery for power energy storage and its manufacturing method. The positive electrode material is prepared by lithium iron phosphate coated with carbon, carbon nanotubes, acetylene black, and graphene, and the surface of the lithium iron phosphate is coated with a layer of carbon film; the negative electrode material is prepared by disordered carbon, and the spacing between disordered carbon layers is 0.30.4nm; the diaphragm is a diaphragm with large porosity and low thickness. The battery prepared by this patented technology has the effect of high-rate fast charging. The positive electrode material is lithium iron phosphate coated with carbon, carbon nanotubes, acetylene black, and graphene. The surface of the lithium iron phosphate is coated with a layer of carbon film. The structural problem increases the surface area, which is conducive to the shuttle of lithium ions and improves the charging efficiency. At the same time, the coated carbon material can absorb harmful substances, moisture and oxides in the electrolyte to improve the battery cycle performance; adding carbon nanotubes, acetylene black, and graphene conductive agents to form a conductive network of points, lines, and surfaces connecting the current collector and the lithium iron phosphate material improves the rate performance.

[0005] In the above patented technologies, the structure and materials are designed for high-rate characteristics. Although they can improve the rate of the battery cell, the failure problem caused by the high rate has not been completely solved. High-rate charging and discharging will still lead to electrolyte infiltration and cyclic lithium deposition failure. This problem can be alleviated by the system but cannot be completely solved. For example, there is a defect of slow liquid absorption rate in the existing positive and negative electrode structures. The electrode has few pores or cannot actually touch the electrolyte, resulting in the transfer of electrolyte relying entirely on the diaphragm, which will cause rapid life decay in the middle and late stages of high-rate discharge; for example, in the existing battery cell structure, there is a certain gap at the edge of the electrode due to thinning. In high-rate cycles, this gap will cause increased polarization, lithium deposition, and affect life. For example, the bottom of the existing diaphragm has a semi-enclosed effect on the electrolyte, and the diaphragm at the bottom of the electrode group will hinder the transmission channel of the electrode after bending. Therefore, it is particularly important to solve the above problems from the perspective of the system and battery cell structure. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings and defects of the prior art and provide a high-power battery electrode group. Through the design of different coatings on the electrode and the diaphragm, the problems of structural lithium deposition and liquid absorption lithium deposition are solved, and the life of the high-power battery cell is fully guaranteed.

[0007] A high-power battery electrode group, comprising a positive electrode sheet, a negative electrode sheet and a separator; the separator is located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet is a three-section coating structure, the middle section coating of the positive electrode sheet connects the upper section coating of the positive electrode sheet close to the pole ear side and the lower section coating of the positive electrode sheet away from the pole ear side; the middle section coating of the positive electrode sheet is a high-rate discharge active material for lithium insertion and extraction, the upper section coating of the positive electrode sheet and the lower section coating of the positive electrode sheet are materials with insulation and liquid absorption capabilities, and the liquid absorption capability of the lower section coating of the positive electrode sheet is greater than that of the upper section coating of the positive electrode sheet;

[0008] The negative electrode sheet has a two-stage coating structure, wherein the upper coating of the negative electrode sheet is an active material layer formed by an active material that supports rapid embedding of lithium ions, and the lower coating of the negative electrode sheet is a porous liquid-absorbing layer formed by an active material containing a large-particle main material with rapid liquid absorption capability;

[0009] The diaphragm has a three-section coating structure, wherein the middle coating of the diaphragm connects the upper coating of the diaphragm and the lower coating of the diaphragm. The upper coating of the diaphragm and the lower coating of the diaphragm are formed of a ceramic material that has the ability to absorb and retain liquid and can expand after absorbing liquid to fill the gap between the top positive and negative electrodes. The middle coating of the diaphragm is formed of a ceramic material that does not have the ability to absorb liquid. The porosity of the base membrane where the lower coating of the diaphragm is located is greater than the porosity of the base membrane of the middle coating of the diaphragm and the upper coating of the diaphragm.

[0010] The width of the upper coating of the positive electrode sheet is 1-15 mm, the width of the lower coating of the positive electrode sheet is 0.5-10 mm, the thickness of the upper coating of the positive electrode sheet and the lower coating of the positive electrode sheet are 20-300 μm, and the coating amount is 20-40 mg / cm 2 The coating thickness of the middle section of the positive electrode sheet is 50 to 300 um, and the coating amount is 30 to 40 mg / cm 2 .

[0011] Wherein, the materials with insulation and liquid absorption capabilities of the upper coating of the positive electrode sheet and the lower coating of the positive electrode sheet include insulating materials, adhesives and liquid absorbents;

[0012] Preferably, the insulating material is at least one of aluminum oxide and boehmite;

[0013] Preferably, the liquid absorbing agent is at least one of a resin-based material and a cellulose-based material;

[0014] Preferably, the binder is at least one of polyvinylidene fluoride and polyimide.

[0015] Preferably, the weight ratio of the insulating material is 75-85%; the weight ratio of the liquid absorbent is 5-10%; and the weight ratio of the binder is 10-15%.

[0016] The high-rate discharge active material for lithium deintercalation in the middle coating of the positive electrode sheet includes an active material main body material, a positive electrode binder and a positive electrode conductor;

[0017] Preferably, the main material of the active substance is at least one of nickel-cobalt-manganese, lithium iron phosphate, lithium cobalt oxide and the like;

[0018] Preferably, the active substance main material comprises a large particle main material and a small particle main material, wherein the particle size of the large particle main material is at least 1.1 to 2 times the particle size of the small particle main material;

[0019] Preferably, the weight proportion of the large particle main material in the active substance main material is 70-90%;

[0020] Preferably, the positive electrode conductive agent is formed by a composite of a spherical conductive agent and a conductive carbon tube, and the spherical conductive agent and the conductive carbon tube are composited through points and lines to achieve rapid transfer of electrons and ions;

[0021] Preferably, the weight of the ball conductive agent is 1 to 3 times that of the conductive carbon tube;

[0022] Preferably, in the high-rate discharge active material, the positive electrode binder accounts for 1.5-4% by weight, the positive electrode conductor accounts for 1-4% by weight, and the active material main body accounts for 92-97% by weight.

[0023] The thickness of the coating on the negative electrode sheet is 30-200um, and the coating amount is 15-20mg / cm 2 The thickness of the lower coating of the negative electrode sheet is the same as the thickness of the upper coating of the negative electrode sheet, and the width of the lower coating of the negative electrode sheet is 0.5 to 10 mm.

[0024] The porosity of the lower coating of the negative electrode sheet is 1.1-1.5 times that of the upper coating of the negative electrode sheet.

[0025] The active material layer of the upper coating of the negative electrode sheet / the lower coating of the negative electrode sheet comprises a negative electrode main material, a negative electrode conductive agent, a negative electrode dispersant and a negative electrode binder;

[0026] The negative electrode main material is at least one of artificial graphite, natural graphite, silicon-carbon, and silicon-oxygen materials;

[0027] The negative electrode main material comprises at least two negative electrode main materials with different particle sizes, the median particle size D50 of the large-particle negative electrode main material is 2 to 5 times that of the small-particle negative electrode main material, and the weight proportion of the negative electrode main material in the active material of the upper coating of the negative electrode sheet is 94 to 97.5%;

[0028] The negative electrode conductive agent is a spherical conductive agent, and its weight proportion in the active material of the upper coating of the negative electrode sheet is 0.3-2.5%;

[0029] The negative electrode dispersant is at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose and branched modified materials thereof, and the weight proportion of the active material in the upper coating of the negative electrode sheet is 0.3-1.5%;

[0030] The negative electrode binder is at least one of styrene-butadiene rubber, acrylonitrile, etc., and its weight ratio in the active material of the upper coating of the negative electrode sheet is 1.0-3.5%;

[0031] Among them, the median particle size D50 of the negative electrode main material of the lower coating of the negative electrode sheet is larger than the particle size of the negative electrode main material of the upper coating of the negative electrode sheet, and the median particle size D50 of the negative electrode main material of the lower coating of the negative electrode sheet is 20 to 50 um.

[0032] Among them, the base membrane porosity of the upper coating of the diaphragm is the same as that of the middle coating of the diaphragm; the ceramic materials of the upper coating of the diaphragm and the lower coating of the diaphragm include insulating ceramic material, bonding material, and liquid absorption and expansion functional material with liquid absorption capacity; and the surface of the ceramic material has a glue layer.

[0033] Wherein, the liquid-absorbing and swelling functional substance is a polymer SFC, which accounts for 10-20% by weight in the ceramic material of the upper coating of the diaphragm / the lower coating of the diaphragm;

[0034] The bonding material in the ceramic material is at least one of polyvinylidene fluoride and polyimide, accounting for 5 to 20% by weight in the ceramic material; the insulating ceramic material is at least one of aluminum oxide and boehmite, accounting for 55 to 80% by weight in the ceramic material;

[0035] Preferably, the adhesive layer includes a binder, which is at least one of polyvinylidene fluoride and polyimide, and is a sprayed dot structure covering the surface of the ceramic material coating, with a surface density of 0.8 g / m 2 .

[0036] Among them, the width of the diaphragm is 1 to 10 mm wider than the negative electrode sheet, the top of the diaphragm exceeds the height of the negative electrode sheet by 1 to 5 mm, the bottom of the diaphragm exceeds the negative electrode sheet by 1-5 mm, and the base membrane is made of PP or PE material with a thickness of 5 to 9 um; the porosity of the base membrane of the upper coating and the middle coating of the diaphragm is 30 to 50%, and the porosity of the base membrane of the lower coating of the diaphragm is greater than 50%.

[0037] The present invention is based on the design of a high-power system. Through the design of different coatings on the pole piece and the diaphragm, the structural lithium deposition and liquid absorption lithium deposition problems are solved, and the life of the high-power battery core is fully guaranteed. In particular, through the segmented design of the pole piece coating, multi-dimensional liquid absorption and electro-liquid transmission of the upper and lower layers of the pole piece are realized, and the pole piece liquid absorption path is optimized, so that the positive pole piece can directly absorb electro-liquid from the bottom, avoiding the positive pole piece being suspended and unable to absorb liquid due to the consideration of the negative electrode covering the positive electrode; and through the segmented design of the diaphragm, the large porosity structure of the lower section can avoid the blockage of the pole piece liquid absorption channel caused by the bending of the diaphragm; through the design of the upper section liquid absorption expansion layer, the electrolyte can be retained while the gap between the positive and negative electrodes caused by the thinning area can be realized, and the occurrence of edge lithium deposition can be avoided while retaining the electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of a positive electrode sheet according to an embodiment of the present invention.

[0039] Figure 2 Schematic diagram of a negative electrode sheet according to an embodiment of the present invention.

[0040] Figure 3 Schematic diagram of a diaphragm according to an embodiment of the present invention.

[0041] Figure 4 It is a schematic diagram of the arrangement of the separator and the positive electrode sheet in the battery electrode group according to an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0043] Referring to the attached drawings, a high-power battery electrode group includes a positive electrode sheet 10, a negative electrode sheet 20 and a separator 30; the separator is located between the positive electrode sheet and the negative electrode sheet to play an insulating role, and the positive electrode sheet, the negative electrode sheet and the separator are wound to form an electrode group, which also includes battery shell cover, battery electrode group, electro-fluid and bonding and sealing structure components and other battery components, which are not related to the present invention and are not shown again.

[0044] The innovation of the present invention lies in that the positive electrode sheet 10 of the present invention is a three-stage coating structure, wherein the positive electrode sheet middle-stage coating 12 connects the positive electrode sheet upper-stage coating 11 close to the pole ear side with the positive electrode sheet lower-stage coating 13 away from the pole ear side; the positive electrode sheet middle-stage coating is a high-rate discharge active material for lithium deintercalation, that is, an active layer that can perform high-rate discharge, the positive electrode sheet upper-stage coating and the positive electrode sheet lower-stage coating are materials with insulation and liquid absorption capabilities, and the liquid absorption capacity of the positive electrode sheet lower-stage coating is greater than that of the positive electrode sheet upper-stage coating;

[0045] The negative electrode sheet 20 of the present invention is a two-stage coating structure, wherein the upper coating 21 of the negative electrode sheet is an active material layer formed by an active material that supports rapid lithium ion embedding, and the lower coating 22 of the negative electrode sheet is a porous liquid absorbing layer formed by an active material having a rapid liquid absorbing ability and containing a large particle size main material, which is a porous liquid absorbing structure;

[0046] The diaphragm 30 of the present invention is a three-stage coating structure, in which the middle coating 32 of the diaphragm connects the upper coating 32 of the diaphragm and the lower coating 33 of the diaphragm. The upper coating and the lower coating of the diaphragm are formed of a ceramic material that has the ability to absorb and retain liquid and can expand after absorbing liquid to fill the gap between the top positive and negative electrodes. This expansion can fill the gap between the top positive and negative electrodes to avoid lithium precipitation caused by excessive gap; the middle coating of the diaphragm is formed of a ceramic material that does not have the ability to absorb liquid. The porosity of the base membrane where the lower coating of the diaphragm is located is greater than the porosity of the base membrane of the middle coating and the upper coating of the diaphragm, which can avoid the sealing of the lower diaphragm after bending and reduce the liquid absorption rate.

[0047] In some embodiments, the width of the upper coating of the positive electrode sheet is 1 to 15 mm, preferably 2 mm, and the width of the lower coating of the positive electrode sheet is 0.5 to 10 mm, preferably 1.5 mm. Specifically, the width of the upper coating and the lower coating of the positive electrode sheet can be selected within these ranges. In the present application, the positive electrode sheet includes aluminum foil, the thickness of the aluminum foil is 10 to 20 um, preferably 13 um bare aluminum foil and 1 um conductive layers on the upper and lower sides.

[0048] In some embodiments, the material with insulation and liquid absorption capabilities of the upper coating of the positive electrode sheet / the lower coating of the positive electrode sheet includes an insulating material, an adhesive and a liquid absorbent; the composite body formed by the three materials is uniformly attached to the upper coating area / the lower coating area to form the upper coating of the positive electrode sheet / the lower coating of the positive electrode sheet.

[0049] Preferably, the insulating material is at least one of aluminum oxide and boehmite, preferably aluminum oxide;

[0050] Preferably, the liquid absorbing agent is at least one of a resin-based and a cellulose (such as hydroxyl and methyl cellulose), preferably SFC, and the particle size after liquid absorption is 2 to 50 um, and the particle size after liquid absorption is preferably 30 um;

[0051] Preferably, the binder is at least one of polyvinylidene fluoride and polyimide;

[0052] Preferably, the weight ratio of the insulating material in the upper coating of the positive electrode sheet / the lower coating of the positive electrode sheet is 75-85%, preferably aluminum oxide, accounting for 80% by weight; the weight ratio of the liquid absorbent in the upper coating of the positive electrode sheet / the lower coating of the positive electrode sheet is 5-10%, preferably SFC, the particle size after liquid absorption is 30um, and the weight ratio before liquid absorption is 5%; the weight ratio of the binder in the upper coating of the positive electrode sheet / the lower coating of the positive electrode sheet is 10-15%, preferably polyvinylidene fluoride, which accounts for 15% by weight,

[0053] In some embodiments, the high-rate discharge active material for lithium deintercalation in the middle coating of the positive electrode sheet includes an active material main body material, a positive electrode binder and a positive electrode conductor;

[0054] Preferably, the main material of the active substance is at least one of nickel-cobalt-manganese, lithium iron phosphate, lithium cobalt oxide and the like, preferably the main material is lithium iron phosphate, accounting for 97%;

[0055] Preferably, the active substance main material includes a large particle main material and a small particle main material, which are uniformly mixed, wherein the particle size of the large particle main material is at least 1.1 to 2 times the particle size of the small particle main material; more preferably, the median particle size D50 of the large particle main material is 1.1 times that of the small particle main material, and the D50 of the small particle main material is 0.6um; the ratio of the large particle main material to the small particle main material is 8:2.

[0056] Preferably, the large particle main material accounts for 70 to 90% by weight of the active material main material composed of the large particle main material and the small particle main material;

[0057] Preferably, the positive electrode conductive agent is formed by a composite of a spherical conductive agent and a conductive carbon tube, and the spherical conductive agent and the conductive carbon tube are composited through points and lines to achieve rapid transfer of electrons and ions;

[0058] Preferably, the weight of the ball conductive agent is 1 to 3 times that of the conductive carbon tube, preferably 1 time;

[0059] Preferably, in the high-rate discharge active material, the positive electrode binder accounts for 1.5-4% by weight, preferably 2% by weight, the positive electrode conductor accounts for 1-4% by weight, preferably 1.5% by weight, and the active substance main material accounts for 92-97% by weight.

[0060] In some embodiments, the thickness of the upper coating of the positive electrode sheet and the lower coating of the positive electrode sheet is 20 to 300 um, preferably 160 um, and the coating amount is 20 to 40 mg / cm 2 The coating amount is preferably 30 mg / cm 2， The coating thickness of the middle section of the positive electrode sheet is 50-300um, preferably 170um, and the coating amount is 30-40mg / cm 2 The coating amount is preferably 35 mg / cm 2 .

[0061] In some embodiments, the thickness of the coating on the upper section of the negative electrode sheet is 30 to 200 um, preferably 120 um, and the coating amount is 15 to 20 mg / cm 2 The preferred coating amount is 19 mg / cm 2 The thickness of the lower coating of the negative electrode sheet is the same as the thickness of the upper coating of the negative electrode sheet, the width of the lower coating of the negative electrode sheet is 0.5-10 mm, preferably 2 mm, the negative electrode sheet includes a copper foil, the upper coating of the negative electrode sheet and the lower coating of the negative electrode sheet are coated on the copper foil to form a negative electrode sheet, the thickness of the copper foil is 3-8 um, preferably 6 um copper foil.

[0062] In some embodiments, the porosity of the lower coating of the negative electrode sheet is 1.1-1.5 times, preferably 1.5 times, that of the upper coating of the negative electrode sheet.

[0063] In some embodiments, the active material layer of the upper coating of the negative electrode sheet includes a negative electrode main material, a negative electrode conductive agent, a negative electrode dispersant and a negative electrode binder;

[0064] The negative electrode main material is at least one of artificial graphite, natural graphite, silicon-carbon, and silicon-oxygen materials;

[0065] The negative electrode main material comprises at least two negative electrode main materials with different particle sizes, the median particle size D50 of the large-particle negative electrode main material is 2 to 5 times, preferably 2 times, and the weight proportion of the negative electrode main material in the active material of the upper coating of the negative electrode sheet is 94 to 97.5%, preferably 96%;

[0066] The negative electrode conductive agent is a spherical conductive agent, and its weight proportion in the active material of the upper coating of the negative electrode sheet is 0.3-2.5%, preferably 1.5%;

[0067] The negative electrode dispersant is at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose and branched modified materials thereof, and the weight proportion of the active material in the upper coating of the negative electrode sheet is 0.3-1.5%, preferably 0.5%;

[0068] The negative electrode binder is at least one of styrene-butadiene rubber, acrylonitrile and the like, and its weight proportion in the active material of the upper coating of the negative electrode sheet is 1.0-3.5%, preferably 2%.

[0069] In the present application, the lower coating of the negative electrode sheet is a porous structure. In terms of material composition, except for the larger particle size of the main material, the rest is the same as the upper coating material of the negative electrode sheet. The accumulation between large particles can enrich the electrolyte upload channel path.

[0070] In some embodiments, the porosity of the base membrane corresponding to the upper coating of the diaphragm and the middle coating of the diaphragm is the same; the ceramic materials of the upper coating of the diaphragm and the lower coating of the diaphragm include insulating ceramic materials, adhesive materials, and liquid-absorbing and swelling functional materials with liquid-absorbing capacity; the surface of the ceramic material has a glue layer, wherein the ceramic layer formed by the ceramic material preferentially adheres to the surface of the base membrane, and then the glue layer adheres to the surface of the ceramic layer.

[0071] Wherein, the liquid-absorbing and swelling functional substance is a polymer SFC, which accounts for 10-20% by weight, preferably 10% in the ceramic material of the upper coating of the diaphragm / lower coating of the diaphragm;

[0072] The bonding substance in the ceramic material is at least one of polyvinylidene fluoride and polyimide, and its weight proportion in the ceramic material is 5-20%, preferably 15%.

[0073] The insulating ceramic material is at least one of aluminum oxide and boehmite, and its weight proportion in the ceramic material is 55-80%, preferably 75%. The insulating ceramic material in the ceramic material without functional substances preferably accounts for 85%.

[0074] Preferably, the adhesive layer includes a binder, which is at least one of polyvinylidene fluoride and polyimide, and is a sprayed dot structure covering the surface of the ceramic material coating, with a surface density of 0.8 g / m2 .

[0075] The width of the diaphragm is 1-10mm wider than the negative electrode sheet, preferably 4mm, the top of the diaphragm exceeds the height of the negative electrode sheet by 1-5mm, the bottom of the diaphragm exceeds the negative electrode sheet by 1-5mm, the base film is made of PP or PE material, and the thickness is 5-9um; the base film porosity of the upper coating of the diaphragm and the middle coating of the diaphragm is 30-50%, preferably 38%, and the base film porosity of the lower coating of the diaphragm is greater than 50%, preferably 55%. The width of the upper coating of the diaphragm and the lower coating of the diaphragm is the same, 1-15mm, preferably 4mm.

[0076] Specifically in this application, when assembling the battery, the bottom of the positive electrode sheet should be aligned with the bottom of the negative electrode sheet, the top of the positive electrode sheet should be aligned with the top of the negative electrode sheet, the diaphragm is located between the positive and negative electrode sheets, and the top of the diaphragm exceeds the height of the negative electrode sheet by 1 to 5 mm, and the bottom of the diaphragm exceeds the negative electrode sheet by 1 to 2 mm. The positive and negative electrode sheets and the diaphragm are wound to form a main winding electrode group; then the battery electrode group is sealed with a shell cover, a protective cover, an electrolyte, etc. to form a long cycle battery with a high rate of charge and discharge, and the injection coefficient is 3.3g / Ah. The arrangement of the diaphragm and the positive and negative electrode sheets of the battery stage group, such as Figure 4 As shown, in the high-pore area at the bottom of the diaphragm, the large holes are used to achieve smooth transfer of the electro-fluid to the lower end of the electrode, avoiding the closure effect from hindering the transfer of the electro-fluid. After the diaphragm is bent, a high-pore accumulation is formed, and the electro-fluid can pass through the bottom; there is a liquid absorption and expansion structure at the upper end of the diaphragm, which can reduce the gap caused by the thinning of the positive and negative electrode edges here through liquid absorption and expansion.

[0077] In summary, the positive electrode sheet of the battery of the present invention has a three-stage coating structure at the large surface level. The upper and lower coatings have not only an insulating function but also a liquid absorbing and retaining function. The lower stage structure has a stronger liquid absorbing structure and capacity; the upper stage structure can retain the electrolyte through the liquid absorbing components, thereby realizing the upper and lower bidirectional electro-liquid transfer of the electrolyte to the active substance.

[0078] The negative electrode sheet of the battery of the present invention is a two-stage structure, and the bottom of the electrode sheet has a strong liquid absorption channel structure, which ensures that the electrolyte is transferred to the pores of the active material at a faster speed, improves the circulation and avoids the occurrence of lithium precipitation.

[0079] The diaphragm of the battery of the present invention is a three-stage structure, the upper coating of the diaphragm is a diaphragm layer with liquid absorption ability; the lower coating of the diaphragm is a macroporous structure, which can realize the smooth transfer of electrolyte to the lower end of the pole piece through the macropores, avoiding the closure effect to hinder the transfer of electrolyte. The upper coating of the diaphragm is a coating with liquid absorption and expansion function, which can fill and infiltrate the pores at the edge of the pole piece through liquid absorption and expansion after liquid absorption, reduce polarization, avoid lithium deposition on the upper part of the pole group, and improve the service life of the battery cell.

[0080] The basic principles and main features of the present invention and the advantages of the present invention are shown and described above. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.

[0081] Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is therefore intended that all changes falling within the meaning and range of equivalent elements of the claims are included in the present invention.

[0082] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A high-power battery electrode group, comprising a positive electrode sheet, a negative electrode sheet and a separator; the separator is located between the positive electrode sheet and the negative electrode sheet, characterized in that: The positive electrode sheet has a three-stage coating structure, wherein the middle coating of the positive electrode sheet connects the upper coating of the positive electrode sheet close to the pole ear side with the lower coating of the positive electrode sheet far from the pole ear side; the middle coating of the positive electrode sheet is a high-rate discharge active material for lithium deintercalation, the upper coating of the positive electrode sheet and the lower coating of the positive electrode sheet are materials with insulation and liquid absorption capabilities, and the liquid absorption capacity of the lower coating of the positive electrode sheet is greater than that of the upper coating of the positive electrode sheet; The negative electrode sheet has a two-stage coating structure, wherein the upper coating of the negative electrode sheet is an active material layer formed by an active material that supports rapid embedding of lithium ions, and the lower coating of the negative electrode sheet is a porous liquid-absorbing layer formed by an active material that contains a large-particle main material and has a rapid liquid-absorbing ability; The diaphragm has a three-section coating structure, wherein the middle coating of the diaphragm connects the upper coating of the diaphragm and the lower coating of the diaphragm. The upper coating of the diaphragm and the lower coating of the diaphragm are formed of a ceramic material that has the ability to absorb and retain liquid and can expand after absorbing liquid to fill the gap between the top positive and negative electrodes. The middle coating of the diaphragm is formed of a ceramic material that does not have the ability to absorb liquid. The porosity of the base membrane where the lower coating of the diaphragm is located is greater than the porosity of the base membrane of the middle coating of the diaphragm and the upper coating of the diaphragm.

2. The high-power battery electrode group according to claim 1, characterized in that: The width of the upper coating of the positive electrode sheet is 1-15 mm, the width of the lower coating of the positive electrode sheet is 0.5-10 mm, the thickness of each is 20-300 um, and the coating amount is 20-40 mg / cm 2 The coating thickness of the middle section of the positive electrode sheet is 50 to 300 um, and the coating amount is 30 to 40 mg / cm 2 .

3. The high-power battery electrode group according to claim 1, characterized in that: The materials with insulation and liquid absorption capabilities of the positive electrode upper coating and the positive electrode lower coating include insulating materials, adhesives and liquid absorbents; Preferably, the insulating material is at least one of aluminum oxide and boehmite; Preferably, the liquid absorbing agent is at least one of a resin-based agent and a cellulose-based agent, and the particle size after liquid absorption is 2 to 50 um; Preferably, the binder is at least one of polyvinylidene fluoride and polyimide. Preferably, the weight ratio of the insulating material is 75-85%; the weight ratio of the liquid absorbent is 5-10%; and the weight ratio of the binder is 10-15%.

4. The high-power battery electrode group according to claim 1, characterized in that: The high-rate discharge active material for lithium deintercalation in the middle coating of the positive electrode sheet comprises an active material main body material, a positive electrode binder and a positive electrode conductor; Preferably, the main material of the active substance is at least one of nickel-cobalt-manganese, lithium iron phosphate, lithium cobalt oxide and the like; Preferably, the active substance main material comprises a large particle main material and a small particle main material, wherein the median particle size D50 of the large particle main material is at least 1.1 to 2 times that of the small particle main material; Preferably, the weight proportion of the large particle main material in the active substance main material is 70-90%; Preferably, the positive electrode conductive agent is formed by a composite of a spherical conductive agent and a conductive carbon tube, and the spherical conductive agent and the conductive carbon tube are composited through points and lines to achieve rapid transfer of electrons and ions; Preferably, the weight of the ball conductive agent is 1 to 3 times that of the conductive carbon tube; Preferably, in the high-rate discharge active material, the positive electrode binder accounts for 1.5-4% by weight, the positive electrode conductor accounts for 1-4% by weight, and the active material main body accounts for 92-97% by weight.

5. The high-power battery electrode group according to claim 1, characterized in that: The thickness of the coating on the negative electrode sheet is 30-200um; the coating amount is 15-20mg / cm 2 The thickness of the lower coating of the negative electrode sheet is the same as the thickness of the upper coating of the negative electrode sheet, and the width of the lower coating of the negative electrode sheet is 0.5 to 10 mm.

6. The high-power battery electrode group according to claim 1, characterized in that: The porosity of the lower coating of the negative electrode sheet is 1.1-1.5 times that of the upper coating of the negative electrode sheet.

7. The high-power battery electrode group according to claim 1, characterized in that: The active material layer of the negative electrode sheet upper coating / negative electrode sheet lower coating comprises a negative electrode main material, a negative electrode conductive agent, a negative electrode dispersant and a negative electrode binder; The negative electrode main material is at least one of artificial graphite, natural graphite, silicon-carbon, and silicon-oxygen materials; The negative electrode main material comprises at least two negative electrode main materials with different particle sizes, the median particle size D50 of the large-particle negative electrode main material is 2 to 5 times that of the small-particle negative electrode main material, and the weight proportion of the negative electrode main material in the active material of the upper coating of the negative electrode sheet is 94 to 97.5%; The negative electrode conductive agent is a spherical conductive agent, and its weight proportion in the active material of the upper coating of the negative electrode sheet is 0.3-2.5%; The negative electrode dispersant is at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose and branched modified materials thereof, and the weight proportion of the active material in the upper coating of the negative electrode sheet is 0.3-1.5%; The negative electrode binder is at least one of styrene-butadiene rubber, acrylonitrile, etc., and its weight ratio in the active material of the upper coating of the negative electrode sheet is 1.0-3.5%; Among them, the median particle size D50 of the negative electrode main material of the lower coating of the negative electrode sheet is larger than the particle size of the negative electrode main material of the upper coating of the negative electrode sheet, and the median particle size D50 of the negative electrode main material of the lower coating of the negative electrode sheet is 20 to 50 um.

8. The high-power battery electrode group according to claim 1, characterized in that: The base film porosity of the upper coating of the diaphragm is the same as that of the middle coating of the diaphragm; the ceramic material of the upper coating of the diaphragm and the lower coating of the diaphragm includes insulating ceramic material, bonding material, and liquid absorbing and swelling functional material with liquid absorbing capacity; the surface of the ceramic material has a glue layer.

9. The high-power battery electrode group according to claim 8, characterized in that: The liquid absorption and swelling functional substance is a polymer SFC, which accounts for 10-20% by weight in the ceramic material of the upper coating of the diaphragm / the lower coating of the diaphragm; The bonding material in the ceramic material is at least one of polyvinylidene fluoride and polyimide, accounting for 5 to 20% by weight in the ceramic material; the insulating ceramic material is at least one of aluminum oxide and boehmite, accounting for 55 to 80% by weight in the ceramic material; Preferably, the adhesive layer includes a binder, which is at least one of polyvinylidene fluoride and polyimide, and is a sprayed dot structure covering the surface of the ceramic material coating, with a surface density of 0.8 g / m 2 .

10. The high-power battery electrode group according to claim 8, characterized in that: The width of the diaphragm is 1 to 10 mm wider than the negative electrode sheet, the top of the diaphragm exceeds the height of the negative electrode sheet by 1 to 5 mm, the bottom of the diaphragm exceeds the negative electrode sheet by 1-5 mm, the base membrane is made of PP or PE material, and has a thickness of 5 to 9 um; the porosity of the base membrane of the upper coating and the middle coating of the diaphragm is 30 to 50%, and the porosity of the base membrane of the lower coating of the diaphragm is greater than 50%.

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