Battery, battery device and electric equipment

Abstract

The invention relates to the technical field of new energy, and discloses a battery, a battery device and electric equipment.The battery comprises a battery shell and a battery cell, the battery cell comprises a pole piece and an insulating film, the pole piece comprises a current collector and an active substance layer, and the proportion of the thickness of the active substance layer in the single pole piece to the thickness of the pole piece is a; the battery cell further comprises a protective layer which is adhered to the active substance layer of the bending section; the protective layer comprises an isolating layer and a bonding layer, pores penetrate through the isolating layer, and the proportion of the total area of the pores to the total area of the isolating layer is b; the active material layer of the negative plate at at least one end in the first direction exceeds the active material layer of the positive plate, and the exceeding distance is c; a * b * c is more than or equal to 0.3 * 10 <-2 > and less than or equal to 61.1 * 10 <-2 >, and the unit is mm. According to the battery provided by the invention, the lithium ion transmission efficiency is guaranteed, the swelling risk of the bonding layer is inhibited, the material falling risk at the R corner part is small, the service life of the battery is prolonged, and lithium precipitation is not easy to occur at the R corner part.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, specifically to a battery, battery device, and electrical equipment. Background Technology

[0002] To improve battery energy density, it is often necessary to increase battery size to accommodate more active material. However, with increased battery size, the risk of active material shedding from the electrodes rises, affecting battery capacity stability and cycle life. Analysis shows that electrode shedding is particularly severe at the bends in the core winding. In related technologies, adhesive tape is applied to the bends in the core winding to fix the active material and suppress electrode shedding.

[0003] However, the tape can hinder lithium-ion transport to some extent. Lithium-ion transport needs to bypass the tape area. After long-term use, lithium plating and lithium dendrite accumulation at the bends can easily puncture the diaphragm and cause internal short circuits, posing a safety hazard. Summary of the Invention

[0004] In view of this, the present invention provides a battery, a battery device, and an electrical device to solve the problem that applying tape to the bends of the battery core can easily increase the risk of lithium plating and thus cause a short circuit.

[0005] In a first aspect, the present invention provides a battery comprising: The battery casing has an opening at at least one end along a first direction; A battery cell, suitable for being disposed inside a battery casing along a first direction, is manufactured by a winding method; the battery cell includes a flat portion and an R-corner portion located at at least one end of the flat portion along a second direction; The battery cell includes electrodes and an insulating film. The electrodes include positive electrodes and negative electrodes, and the insulating film is located between adjacent positive and negative electrodes. The electrode includes a current collector and an active material layer coated on at least one side of the current collector, wherein the thickness of the active material layer in a single electrode is a proportion of the electrode thickness. The electrode includes bent sections, and multiple bent sections form the R-corner portion; The cell also includes a protective layer, which is adhered to the active material layer of the bending section; the protective layer includes an insulating layer and an adhesive layer, with the adhesive layer disposed between the insulating layer and the bending section, and the insulating layer having through-holes, the total area of ​​the through-holes accounting for b% of the total area of ​​the insulating layer; Along the first direction, the width of the active material layer of the negative electrode is greater than the width of the active material layer of the positive electrode, and the active material layer of the negative electrode is set beyond the active material layer of the positive electrode at least one end along the first direction, wherein the distance of the extension at one end is c, in mm. a, b, and c satisfy the relation: 0.3 × 10 -2 ≤a×b×c≤61.1×10 -2 The unit is mm.

[0006] Beneficial Effects: This embodiment adjusts the relationship between a, b, and c to satisfy the above formula. When the proportion b of the total area of ​​the channels to the total area of ​​the separator increases, the thickness proportion a of the active material layer in a single electrode sheet is correspondingly reduced, and the excess distance c of the negative electrode sheet is decreased. While ensuring lithium-ion transport efficiency, it suppresses the risk of swelling of the adhesive layer, reduces the risk of material loss at the R-corner, improves battery life, and makes lithium plating less likely to occur at the R-corner, thus improving battery safety. When the value of the formula a×b×c is too large, it will lead to stress concentration in the active material layer, swelling of the adhesive layer, or redundancy of the negative electrode material, increasing the risk of material loss at the R-corner. When the value of the formula a×b×c is too small, it will lead to obstructed lithium-ion transport and insufficient lithium intercalation space in the negative electrode, which will easily lead to lithium-ion precipitation, forming lithium dendrites, and increasing the risk of battery insulation failure.

[0007] Secondly, the present invention also provides a battery device comprising: a plurality of batteries as described above.

[0008] Since the battery device includes a battery and has the same effect as a battery, it will not be described further here.

[0009] Thirdly, the present invention also provides an electrical device, comprising: an electrical device body, and a battery device as described above that is electrically connected to the electrical device body.

[0010] Since electrical equipment includes batteries and has the same effect as batteries, it will not be elaborated further here. Attached Figure Description

[0011] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0012] Figure 1 This is an exploded view of the battery of the present invention; Figure 2 This is a cross-sectional schematic diagram of the battery cell of the present invention; Figure 3 This is a cross-sectional schematic diagram of the positive electrode, negative electrode, and insulating film of the present invention; Figure 4 This is a detailed view of the cross-section of the battery cell of the present invention; Figure 5 This is a partial cross-sectional view of the protective layer of the present invention; Figure 6 This is a schematic diagram of the unfolded state of the positive or negative electrode sheet of the present invention.

[0013] Explanation of reference numerals in the attached figures: 1. Battery casing; 11. Opening; 2. Battery cell; 21. Flat section; 22. Rounded corner; 201. Electrode; 202. Insulating film; 203. Protective layer; 204. Tab; 2011, Positive electrode sheet; 2012, Negative electrode sheet; 2017, Current collector; 2019, Active material layer; 2031, Separator layer; 2032, Adhesive layer; 20111, First insulating layer; 20121, Second insulating layer; 20311, Channel; Detailed Implementation To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0015] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0016] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0017] To improve battery energy density, it is often necessary to increase battery size to accommodate more active material. However, with increased battery size, the risk of active material shedding from the electrodes rises, affecting battery capacity stability and cycle life. Analysis shows that electrode shedding is particularly severe at the bends in the core winding. In related technologies, adhesive tape is applied to the bends in the core winding to fix the active material and suppress electrode shedding.

[0018] However, the tape can hinder lithium-ion transport to some extent. Lithium-ion transport requires bypassing the tape area, and over time, this can lead to lithium plating and dendrite accumulation at bends, potentially puncturing the separator and causing internal short circuits, posing a safety hazard. Lithium plating is an abnormal electrochemical phenomenon during lithium-ion battery charging where lithium ions fail to properly embed into the negative electrode material and instead deposit as metallic lithium on the negative electrode surface. The large accumulation of deposited lithium ions forms dendritic metallic lithium crystals on the electrode surface; their uncontrolled growth can puncture the separator, causing a short circuit, thermal runaway, or even an explosion.

[0019] Research has shown that incorporating ion transport channels in the protective layer can suppress lithium crystal formation. However, perforations in the protective layer make it prone to detaching from the electrode. Increasing the size of the negative electrode beyond the positive electrode provides more space for lithium intercalation, reducing the risk of lithium ion deposition at cell bends. However, excessively large negative electrode sizes can affect the space utilization within the battery casing, reducing energy density. To improve energy density, the proportion of active material layer thickness to electrode thickness can be increased; however, excessively increasing the active material layer thickness increases the risk of material loss at cell bends, reducing battery life.

[0020] The following is combined Figures 1 to 6 The following describes embodiments of the present invention.

[0021] According to an embodiment of the present invention, in one aspect, a battery is provided, comprising: The battery casing 1 has an opening 11 formed at least at one end along a first direction; The battery cell 2 is adapted to be disposed inside the battery case 1 along a first direction. The battery cell 2 is manufactured by winding. The battery cell 2 includes a straight portion 21 and an R-corner portion 22 located at at least one end of the straight portion 21 along a second direction. The battery cell 2 includes an electrode 201 and an insulating film 202. The electrode 201 includes a positive electrode 2011 and a negative electrode 2012. The insulating film 202 is located between adjacent positive electrode 2011 and negative electrode 2012. The electrode 201 includes a current collector 2017 and an active material layer 2019 coated on at least one side of the current collector 2017. The thickness of the active material layer 2019 in a single electrode 201 accounts for a proportion of the thickness of the electrode 201. The electrode 201 includes a bent section in a bent state, and multiple bent sections form an R-corner portion 22; The battery cell 2 also includes a protective layer 203, which is attached to the active material layer 2019 of the bending section. The protective layer 203 includes an insulating layer 2031 and an adhesive layer 2032. The adhesive layer 2032 is disposed between the insulating layer 2031 and the bending section. The insulating layer 2031 has a channel 20311 through it. The total area of ​​the channel 20311 accounts for b% of the total area of ​​the insulating layer 2031. Along the first direction, the width of the active material layer 2019 of the negative electrode 2012 is greater than the width of the active material layer 2019 of the positive electrode 2011, and the active material layer 2019 of the negative electrode 2012 extends beyond the active material layer 2019 of the positive electrode 2011 at least one end along the first direction, wherein the distance by which one end extends is c, in mm. a, b, and c satisfy the relation: 0.3 × 10 -2 ≤a×b×c≤61.1×10 -2 The unit is mm.

[0022] The battery in this embodiment includes a battery casing 1, which is a component used to provide a space to house the battery cell 2 and other components and isolate them from the outside environment. Specifically, the battery casing 1 may include a casing body and a cover plate. The casing body has an opening 11 at at least one end along a first direction, and the cover plate is disposed at the opening 11 to seal the casing body, sealing and isolating the internal environment of the battery from the external environment. An electrical connector is provided on the cover plate to enable conduction between the battery cell 2 and an external circuit. The battery casing 1 may be made of metals or alloys including, but not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, titanium, and magnesium.

[0023] During battery assembly, the battery cell 2 is inserted into the casing along a first direction. The battery cell 2 is welded to the electrical connector via the tabs 204 of the negative electrode 2012 and the positive electrode 2011. The electrical connector may specifically include a terminal post and may also include an adapter plate; the terminal post penetrates the cover plate and is insulated. When the electrical connector only includes a terminal post, one end of the terminal post extends out of the cover plate for connection with an external circuit, and the other end extends into the casing and is welded to the tab 204 of the battery cell 2; when the electrical connector also includes an adapter plate, one end of the adapter plate is welded to the tab 204, and the other end is welded to the terminal post, thereby achieving electrical connection.

[0024] The tabs 204 of the battery cell 2 specifically include a positive tab and a negative tab. The positive tab and the negative tab can extend along a first direction and be located at the same end of the battery cell 2, or they can be located at opposite ends of the battery cell 2.

[0025] In this embodiment, the battery cell 2 can specifically be a wound battery cell. A wound battery cell is generally made by a winding process using continuous positive and negative electrode sheets and an insulating film 202. The insulating film 202 is located between adjacent positive and negative electrode sheets to prevent direct contact between the positive and negative electrode sheets, which could cause a short circuit. The forming process of the wound battery cell includes a winding step and a pressing step. The continuous positive and negative electrode sheets and the insulating film 202 are continuously wound on a winding needle. After the winding needle is pulled out, the circular core is pressed to form an elliptical or racetrack-shaped core. The major axis of the battery cell 2 extends along a second direction, and the minor axis extends along a third direction, with the length of the major axis being greater than the length of the minor axis. The overall structure of the battery cell 2 forms an R-corner portion 22 and a straight portion 21. The straight portion 21 is formed in the central region of the battery cell 2, and the R-corner portions 22 are located on both sides of the straight portion 21 along the second direction. The R-corner portions 22 have an arc-shaped structure. During the pressing process, stress concentration occurs in the bending area of ​​the electrode sheet, which poses a significant risk of material loss.

[0026] The positive electrode 2011 and / or negative electrode 2012 include a current collector 2017 and an active material layer 2019 coated on at least one side of the current collector 2017. The active material layer 2019 located in the R-corner 22, especially the active material layer in the inner circle of the R-corner 22, is subjected to greater stress during the winding and compaction process, which poses a risk of cracking. In particular, during charge and discharge cycles, repeated volume expansion and contraction can easily exacerbate the generation of cracks, which can easily lead to the detachment of the active material layer 2019.

[0027] To suppress cracking and detachment of the active material layer 2019, in this embodiment, a protective layer 203 is further attached to the surface of the active material layer 2019 in the bending section. The protective layer 203 effectively covers the active material layer 2019, relieves stress concentration in the R-corner 22, and fixes the active material layer 2019, thereby suppressing the risk of cracking and detachment of the active material layer 2019.

[0028] The protective layer 203 includes an isolation layer 2031 and an adhesive layer 2032 attached to the isolation layer 2031. The isolation layer 2031 has high flexibility and can effectively resist stress deformation generated during bending. The adhesive layer 2032 is coated on the surface of the isolation layer 2031 and is closely attached to the active material layer 2019 to enhance the interfacial bonding force.

[0029] In this embodiment, the isolation layer 2031 is provided with a through-hole 20311. By providing the through-hole 20311, lithium ions can easily pass through the through-hole 20311 to achieve insertion and extraction, thereby improving the lithium ion transport efficiency in the corresponding area of ​​the protective layer 203 and reducing the risk of lithium dendrite formation. However, the protective layer 203 with the through-hole 20311 is prone to increasing the contact area between the electrolyte and the adhesive layer 2032 in the protective layer 203, causing the adhesive layer 2032 to swell, which in turn causes the protective layer 203 to fall off, losing protection for the bending section and increasing the risk of material falling off the bending section.

[0030] The larger the proportion 'a' of the thickness of the active material layer 2019 in the single electrode 201 to the total thickness of the electrode 201, the greater the risk of the active material layer 2019 cracking and falling off due to stress concentration when bent. Conversely, the smaller the proportion 'a' of the thickness of the active material layer 2019 in the single electrode 201 to the total thickness of the electrode 201, the lower the energy density of the cell and the less space is available for lithium intercalation. This can easily lead to an increased risk of lithium plating, causing lithium ions to precipitate on the negative electrode surface and form dendrites, increasing the risk of piercing the insulating film 202 and causing an internal short circuit.

[0031] The ratio b of the total area of ​​the channels 20311 to the total area of ​​the separator 2031 affects the lithium-ion transport efficiency and the degree of electrolyte erosion of the adhesive layer 2032. When the ratio b is too large, although it is beneficial to lithium-ion migration, it will significantly increase the electrolyte penetration path, exacerbate the swelling risk of the adhesive layer 2032, weaken the adhesion strength, make it easy to peel off, and cause material loss. When the ratio b is too small, lithium-ion transport is hindered, and the risk of lithium plating increases.

[0032] The active material layer 2019 of the negative electrode 2012 extends beyond the active material layer 2019 of the positive electrode 2011 at least one end along the first direction. The distance c is used to ensure that the negative electrode can fully accommodate lithium ions during charging and discharging. When c is larger, although it can improve the lithium ion capacity and reduce the risk of lithium plating, an excessively large c will lead to an increase in the redundant area of ​​the negative electrode 2012, making the negative electrode 2012 prone to material loss and occupying more space, thus affecting the overall energy density of the cell. When c is too small, the negative electrode cannot fully accommodate lithium ions, the risk of lithium plating increases significantly, thereby affecting the cycle life of the cell and even causing safety problems.

[0033] This embodiment adjusts the relationship between a, b, and c to satisfy the above formula. For example, when the proportion b of the total area of ​​the channel 20311 to the total area of ​​the separator 2031 increases, the thickness proportion a of the active material layer 2019 in the single electrode 201 is reduced accordingly, and the overhang distance c of the negative electrode 2012 is reduced. While ensuring the lithium-ion transmission efficiency, the swelling risk of the adhesive layer 2032 is suppressed, resulting in a small risk of material loss at the R-corner 22, improving battery life, and making lithium plating less likely to occur at the R-corner 22, thus improving battery safety.

[0034] When the value of formula a×b×c is too large, the thickness ratio 'a' of the active material layer 2019 in electrode 201 is too large, the ratio 'b' of the total area of ​​the pores 20311 to the total area of ​​the separator 2031 is too large, and the excess distance 'c' of the negative electrode 2012 is too large. This will lead to stress concentration in the active material layer, swelling of the adhesive layer, or redundancy of the negative electrode material, increasing the risk of material loss at the R corner 22.

[0035] When the values ​​of the formula a×b×c are too small, the thickness ratio a of the active material layer 2019 in the electrode 201 is too small, the ratio b of the total area of ​​the channel 20311 to the total area of ​​the separator 2031 is too small, and the excess distance c of the negative electrode 2012 is too small. This leads to obstructed lithium-ion transport and insufficient lithium intercalation space in the negative electrode, which can easily lead to lithium-ion precipitation, the formation of lithium dendrites, and a high risk of battery insulation failure.

[0036] For example, in this embodiment, the value of a×b×c can be 0.003 or 0.005 or 0.008 or 0.01 or 0.013 or 0.025 or 0.05 or 0.07 or 0.08 or 0.1 or 0.2 or 0.23 or 0.4 or 0.6 or 0.61, etc., or it can be any range formed by any two of the above values.

[0037] The positive electrode is one of the core components in a battery that carries the positive electrode active material. During charging, metal ions (such as lithium ions) are released from the crystal lattice of the positive electrode active material (oxidation reaction), migrate through the electrolyte, and intercalate into the negative electrode. During discharging, metal ions (such as lithium ions in a lithium battery) are released from the negative electrode and intercalated into the crystal lattice of the positive electrode active material (reduction reaction), thus realizing the storage and release of lithium ions.

[0038] A positive electrode generally includes a positive current collector and a positive active material layer. The positive active material layer is coated on at least one surface of the positive current collector and includes: a positive active material, a conductive agent, and a binder. The positive active material includes, but is not limited to, at least one of the following: lithium phosphates, lithium transition metal oxides and their respective modified compounds, or other conventional materials that can be used as positive active materials for batteries. These positive active materials can be used alone or in combination. The lithium phosphates include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also abbreviated as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also abbreviated as NCM333), LiNi0.5Co0.2Mn0.3O2 (also abbreviated as NCM523), LiNi0.5Co0.2Mn0.3O2), and LiNi0.5Co0.2Mn0.3O2. The cathode conductive agent includes, but is not limited to, graphite, superconducting carbon, and carbon black (such as acetylene black, Ketjen black, Super...). The cathode conductive agent includes, but is not limited to, graphite, superconducting carbon, and carbon black (such as acetylene black, Ketjen black, Super...). The cathode binder comprises, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc. The positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, it can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium with a silver-plated surface. The composite current collector can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).During the charging and discharging process of a battery, the negative electrode acts as a carrier for active ions (such as Li) coming from the positive electrode. These active ions can be inserted into or extracted, playing a role in energy storage and release. Negative electrode active materials include carbon-based materials (graphite, natural graphite, etc.), silicon-based materials (elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, etc.), tin-based materials (elemental tin, tin oxides, and tin alloys, etc.), lithium titanate materials, and metallic lithium materials. The negative electrode current collector can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium, and can be surface-plated with silver. Composite current collectors may include a polymer base layer and a metal layer. Composite current collectors can be formed by forming metal materials (aluminum, aluminum alloys, copper, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer substrate (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0039] The insulating membrane 202, also called a separator, is placed between the positive and negative electrode plates to separate them and prevent short circuits. The separator can be at least one of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride. A coating can also be applied to the surface of the separator. The coating can be an inorganic coating and / or an organic coating; wherein the inorganic coating material includes at least one of alumina, silicon oxide, titanium oxide, magnesium oxide, zirconium oxide, and boehmite; and the organic coating includes at least one of aramid coating and PVDF coating.

[0040] In protective layer 203, the material of insulating layer 2031 is polyvinyl chloride, polyethylene, polypropylene, polyvinylidene fluoride, or hexafluoropropylene. Vinylidene fluoride copolymer, tetrafluoropropylene Vinylidene fluoride copolymer, trifluorochloropropylene At least one or more of the following: polyvinylidene fluoride copolymer, polyethylene terephthalate, polyimide, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyvinylidene fluoride, polyvinylidene fluoride copolymer, polyarylate, fiber, nylon, nonwoven fabric, etc. The adhesive layer 2032 is made of at least one of the following: acrylic-acrylate copolymer, butadiene-styrene copolymer, styrene-acrylic copolymer, styrene-acrylate copolymer, ethylene-vinyl acetate copolymer, acrylic-grafted polyethylene, maleic anhydride-grafted polyethylene, acrylic-grafted polypropylene, polyvinylidene fluoride, maleic anhydride-grafted polypropylene, carboxymethyl cellulose, polyimide, polyetherimide, styrene-isoprene-styrene copolymer rubber, polyethylene phthalate, ethylene-vinyl acetate copolymer bisphenol A type epoxy resin, ethylene-vinyl acetate copolymer bisphenol F type epoxy resin, glycerol ether type epoxy resin, glycerol ester type epoxy resin, silicone type resin, polyurethane, and styrene-isoprene-styrene copolymer.

[0041] In some embodiments, the value range of c satisfies: 0.4≤c≤2.5, and the unit is mm.

[0042] The active material layer 2019 of the negative electrode 2012 extends beyond the active material layer 2019 of the positive electrode 2011 at least one end along the first direction. The distance c is used to ensure that the negative electrode can fully accommodate lithium ions during charging and discharging. When c is larger, although it can improve the lithium ion capacity and reduce the risk of lithium plating, an excessively large c will lead to an increase in the redundant area of ​​the negative electrode 2012, making the negative electrode 2012 prone to material loss and occupying more space, thus affecting the overall energy density of the cell. When c is too small, the negative electrode cannot fully accommodate lithium ions, the risk of lithium plating increases significantly, thereby affecting the cycle life of the cell and even causing safety problems.

[0043] For example, in this embodiment, the value of c can be 0.4 or 0.5 or 0.6 or 0.8 or 0.97 or 1 or 1.2 or 1.5 or 1.8 or 2 or 2.2 or 2.5, or it can be a range formed by any two of the above values.

[0044] In some embodiments, the active material layer 2019 of the negative electrode 2012 extends beyond the active material layer 2019 of the positive electrode 2011 at both ends along the first direction.

[0045] By setting the active material layer 2019 of the negative electrode 2012 to extend beyond the active material layer 2019 of the positive electrode 2011 at both ends along the first direction, the negative electrode has a more balanced lithium-ion receiving capacity during charging and discharging, further reducing the risk of lithium plating.

[0046] In some embodiments, the sum of the dimensions of the active material layer 2019 of the negative electrode 2012 extending beyond the active material layer 2019 of the positive electrode 2011 along the first direction is c2, in mm, and satisfies: 0.8≤c2≤5.

[0047] When the sum of the dimensions c2 of the active material layer 2019 of the negative electrode 2012 extending beyond the active material layer 2019 of the positive electrode 2011 along the first direction is too large, although it helps to increase the lithium-ion capacity of the negative electrode, it will lead to material waste, increase the redundancy of the negative electrode, decrease the space utilization rate, reduce the energy density of the cell, and increase the risk of material loss. When c2 is too small, the lithium-ion concentration in the edge area of ​​the negative electrode is prone to be too high, which will increase the probability of lithium plating.

[0048] For example, in this embodiment, the value of c2 can be 0.8 or 0.97 or 1 or 1.2 or 1.5 or 1.8 or 2 or 2.2 or 2.5 or 3 or 3.5 or 4.5 or 5, or it can be any range formed by any two of the above values.

[0049] In some embodiments, the active material layer 2019 of the negative electrode 2012 extends beyond one end of the current collector 2017 of the corresponding positive electrode 2011 along a first direction, with an extension distance of d in mm, satisfying: 0.45≤d≤2.4.

[0050] The active material layer 2019 of the negative electrode 2012 extends beyond the current collector 2017 of the corresponding positive electrode 2011 along one end of the first direction. When the distance d is too large, although it helps to increase the lithium ion capacity of the negative electrode, it will lead to material waste, increase the redundancy of the negative electrode, reduce the space utilization, reduce the energy density of the cell, and increase the risk of material loss. When d is too small, the lithium ion concentration in the edge area of ​​the negative electrode is prone to be too high, which will increase the probability of lithium plating.

[0051] For example, in this embodiment, the value of d can be 0.45 or 0.5 or 0.6 or 0.8 or 0.97 or 1 or 1.2 or 1.5 or 1.8 or 2 or 2.2 or 2.4, or it can be any range formed by any two of the above values.

[0052] In some embodiments, the positive electrode 2011 includes a current collector 2017 and an active material layer 2019 disposed on at least one surface of the current collector 2017. A first insulating layer 20111 is also disposed at at least one end along a first direction. The first insulating layer 20111 is disposed on the current collector 2017, and the width of the first insulating layer 20111 along the first direction ranges from 1 mm to 10 mm.

[0053] In this embodiment, the first insulating layer 20111 can be a tab adhesive or an insulating coating, used to block direct contact between the end of the positive electrode and the negative electrode, effectively preventing short circuits inside the cell.

[0054] When the width of the first insulating layer 20111 along the first direction is too small, it is difficult to completely cover the end of the positive electrode, resulting in a high risk of insulation failure and a potential short circuit. When the width of the first insulating layer 20111 along the first direction is too large, it will occupy too much effective space, affecting the compactness of the electrode material layout, reducing the overall energy density of the cell, and affecting the transport of lithium ions, resulting in a high risk of lithium plating.

[0055] For example, in this embodiment, the width of the first insulating layer 20111 along the first direction can be 1mm or 2mm or 2.5mm or 3mm or 5mm or 7mm or 8.4mm or 9mm or 10mm, or it can be a range formed by any two of the above values.

[0056] In some embodiments, the first insulating layer 20111 and the active material layer 2019 of the positive electrode 2011 at least partially overlap in a first direction.

[0057] By making the first insulating layer 20111 at least partially overlap with the active material layer 2019 of the positive electrode 2011 in the first direction, the active material layer 2019 in the edge region of the positive electrode can be covered, reducing the risk of material loss and preventing the negative electrode from being inserted into the positive electrode and causing a short circuit.

[0058] In some embodiments, at least one end of the negative electrode 2012 along the first direction is further provided with a second insulating layer 20121; along the first direction, the width of the second insulating layer 20121 ranges from 1mm to 10mm.

[0059] The second insulating layer 20121 is coated on at least one side of the current collector 2017 near the tab, or on at least one side of the tab surface, to prevent short circuit between the tab and the opposite electrode; it can also prevent the tab from breaking due to bending during battery cell assembly; the second insulating layer 20121 mainly includes insulating materials such as PVDF (polyvinylidene fluoride), boehmite, polypropylene, and polyethylene.

[0060] In this embodiment, the second insulating layer 20121 can be tab adhesive or insulating coating, used to block direct contact between the end of the positive electrode and the negative electrode, effectively preventing short circuits inside the cell.

[0061] When the width of the second insulating layer 20121 is too large relative to the width of the active material layer 2019 of the negative electrode sheet 2012, it will significantly compress the coating area of ​​the negative electrode active material, resulting in a decrease in capacity and affecting the battery energy density. When the ratio is too small, it will be difficult to effectively cover the edge of the negative electrode sheet, reduce the insulation reliability, increase the risk of short circuit between the positive and negative electrodes, and increase the risk of material loss from the active material layer 2019 of the negative electrode sheet 2012.

[0062] For example, in this embodiment, the width of the second insulating layer 20121 relative to the width of the active material layer 2019 of the negative electrode 2012 can be 1mm, 2mm, 2.5mm, 3mm, 5mm, 7mm, 8.4mm, 9mm, or 10mm, or it can be any range formed by any two of the above values.

[0063] In some embodiments, at least one end of the insulating film 202 extends beyond the end of the positive electrode 2011 along the first direction, and the distance extending beyond the end ranges from 0.6 mm to 7.3 mm.

[0064] When the distance exceeds the limit, it not only wastes the internal space of the cell and reduces the volume utilization rate, but also increases the impedance, affects the ion migration efficiency, and makes lithium plating more likely. When the distance exceeds the limit, it cannot effectively cover the end of the positive electrode, resulting in insufficient insulation performance and the risk of short circuit between the positive and negative electrodes.

[0065] For example, in this embodiment, at least one end of the insulating film 202 extends beyond the end of the positive electrode 2011 along the first direction. The value of the distance extending beyond the end can be 0.6mm, 1mm, 2mm, 2.5mm, 3mm, 5mm, 7mm, or 7.3mm, or it can be a range formed by any two of the above values.

[0066] In some embodiments, along the first direction, at least one end of the insulating film 202 extends beyond the end of the negative electrode 2012, and the distance extending beyond the end ranges from 0.4 mm to 4 mm.

[0067] When the distance exceeds the limit, the space occupied by the insulating film increases, resulting in a decrease in the volumetric energy density of the battery cell and an increase in impedance, which affects the ion migration efficiency and makes lithium plating more likely. When the distance exceeds the limit, it cannot effectively cover the edge area of ​​the negative electrode, resulting in a decrease in insulation reliability and an increase in the risk of short circuit between the positive and negative electrodes.

[0068] For example, in this embodiment, along the first direction, at least one end of the insulating film 202 extends beyond the end of the negative electrode 2012. The value of the distance extending beyond the end can be 0.4mm, 0.6mm, 1mm, 2mm, 2.5mm, 3mm, or 4mm, or it can be a range formed by any two of the above values.

[0069] It should be noted that in the above embodiments, the position where the insulating film 202 extends beyond the positive electrode 2011 can be on the same side as the position where the negative electrode 2012 extends beyond the positive electrode 2011.

[0070] In some embodiments, the range of values ​​for a satisfies: 0.7 ≤ a ≤ 0.98.

[0071] The larger the proportion 'a' of the thickness of the active material layer 2019 in the single electrode 201 to the total thickness of the electrode 201, the greater the risk of the active material layer 2019 cracking and falling off due to stress concentration when bent. Conversely, the smaller the proportion 'a' of the thickness of the active material layer 2019 in the single electrode 201 to the total thickness of the electrode 201, the lower the energy density of the cell and the less space is available for lithium intercalation. This can easily lead to an increased risk of lithium plating, causing lithium ions to precipitate on the negative electrode surface and form dendrites, increasing the risk of piercing the insulating film 202 and causing an internal short circuit.

[0072] For example, in this embodiment, the value of 'a' can be 0.7, 0.73, 0.75, 0.78, 0.8, 0.83, 0.86, 0.9, 0.94, or 0.98, or it can be any range formed by any two of the above values.

[0073] When electrode 201 is a positive electrode, the thickness of the active material layer 2019 in a single positive electrode ranges from 30μm to 210μm, and the thickness of a single positive electrode ranges from 36μm to 228μm. When electrode 201 is a negative electrode, the thickness of the active material layer 2019 in a single negative electrode ranges from 30μm to 200μm, and the thickness of a single negative electrode ranges from 34μm to 212μm.

[0074] In some embodiments, when electrode 201 is a negative electrode 2012, the value range of a satisfies: 0.7≤a≤0.96.

[0075] When electrode 201 is the negative electrode 2012, the thickness ratio 'a' of the active material layer 2019 directly affects the lithium intercalation capability and structural stability of the negative electrode. If 'a' is too large, it is easy to crack and lose material due to stress concentration when bending. If 'a' is too small, the lithium intercalation space is insufficient, the risk of lithium plating increases significantly, and lithium dendrites are easily formed, which can then pierce the insulating film 202 and cause an internal short circuit. In severe cases, it may lead to thermal runaway and threaten battery safety.

[0076] In some embodiments, when electrode 201 is a positive electrode 2011, the value range of a satisfies: 0.75≤a≤0.98.

[0077] When electrode 201 is a positive electrode 2011, the thickness ratio 'a' of the active material layer 2019 will affect the lithium-ion insertion / extraction efficiency and structural stability of the positive electrode material. If 'a' is too large, the risk of cracks in the active material layer due to drastic volume changes during charging and discharging will increase. If 'a' is too small, the content of positive electrode active material will be insufficient, resulting in a decrease in cell capacity and energy density, while also affecting the lithium-ion insertion / extraction efficiency and deteriorating cycle performance.

[0078] In some embodiments, the thickness of the current collector 2017 of the negative electrode 2012 ranges from 4 μm to 12 μm; And / or, the thickness of the active material layer 2019 of the negative electrode 2012 ranges from 30μm to 200μm.

[0079] If the thickness of the current collector 2017 in the negative electrode 2012 is too large, it will increase the internal resistance of the electrode, reduce the energy density of the battery, and affect the bending performance; if the thickness is too small, the mechanical strength will be insufficient, and it will be easy to break during rolling or bending, affecting the integrity of the electrode structure.

[0080] If the active material layer 2019 of the negative electrode 2012 is too thick, it is easy to crack or lose material during bending, which will affect the electrochemical performance; if the thickness is too small, the lithium intercalation capacity will be limited and the risk of lithium plating will increase.

[0081] In this embodiment, the current collector 2017 of the negative electrode 2012 can be coated with an active material layer 2019 on one side to form a single-sided negative electrode, or coated with an active material layer 2019 on both sides to form a double-sided negative electrode.

[0082] For example, in this embodiment, the thickness of the current collector 2017 of the negative electrode 2012 can be 4μm, 5μm, 6μm, 8μm, 10μm, or 12μm, or it can be a range formed by any two of the above values.

[0083] For example, in this embodiment, the thickness of the active material layer 2019 of the negative electrode 2012 can be 30μm or 45μm or 55μm or 73μm or 96μm or 100μm or 120μm or 145μm or 168μm or 200μm, or it can be a range formed by any two of the above values.

[0084] In some embodiments, the thickness of the current collector 2017 of the positive electrode 2011 ranges from 6 μm to 18 μm; And / or, the thickness of the active material layer 2019 of the positive electrode 2011 ranges from 30 μm to 210 μm.

[0085] To prevent corrosion of the current collectors, traditional lithium batteries typically use aluminum-containing current collectors for the positive electrode and copper-containing current collectors for the negative electrode. Since aluminum-containing materials include some aluminum alloys or oxides, the positive electrode sheet is less tough and more brittle than the negative electrode sheet, making it easier for the positive electrode active material to fall off in the bending area. Therefore, setting a protective layer 203 on the positive electrode sheet can effectively protect the active material on it.

[0086] When the thickness of the current collector 2017 in the positive electrode 2011 is too large, it will lead to a decrease in the bending performance of the positive electrode, increase the risk of brittle fracture, and cause the active material layer to peel off. When the thickness of the current collector 2017 in the positive electrode 2011 is too small, the mechanical strength is insufficient and it is difficult to withstand bending and rolling stress, which will also easily cause breakage.

[0087] When the active material layer 2019 of the positive electrode 2011 is too thick, cracks are easily generated during bending, which in turn leads to material loss; while when the active material layer 2019 of the positive electrode 2011 is too thin, the active material content is insufficient, resulting in low cell capacity and inability to effectively improve energy density.

[0088] In this embodiment, the current collector 2017 of the positive electrode 2011 can be coated with an active material layer 2019 on one side to form a single-sided negative electrode, or coated with an active material layer 2019 on both sides to form a double-sided negative electrode.

[0089] For example, in this embodiment, the thickness of the current collector 2017 of the positive electrode 2011 can be 6μm or 8μm or 10μm or 12μm or 14μm or 15μm or 18μm, or it can be a range formed by any two of the above values.

[0090] For example, in this embodiment, the thickness of the active material layer 2019 of the positive electrode 2011 can be 30μm or 45μm or 55μm or 73μm or 96μm or 100μm or 120μm or 145μm or 168μm or 200μm or 210μm, or it can be a range formed by any two of the above values.

[0091] In some embodiments, the thickness of the insulating film 202 ranges from 5 μm to 20 μm.

[0092] If the thickness of the insulating film 202 is too large, it will increase the internal resistance of the cell, affect the smooth transport of lithium ions, increase the risk of lithium plating, and affect the energy density; if the thickness of the insulating film 202 is too small, the insulation performance will be insufficient, which will easily cause internal short circuits and reduce battery safety.

[0093] For example, in this embodiment, the thickness of the insulating film 202 can be 5μm, 6μm, 8μm, 10μm, 12μm, 14μm, 15μm, 18μm, or 20μm, or it can be a range formed by any two of the above values.

[0094] In some embodiments, along the winding direction of the cell 2, the active material layer 2019 of the negative electrode 2012 at at least one end extends beyond the active material layer 2019 of the positive electrode 2011, and the distance of the extension ranges from 20mm to 800mm.

[0095] If the distance is too small, the space for the negative electrode 2012 to accommodate lithium ions is insufficient, which can easily lead to uneven deposition of lithium ions on the negative electrode surface, resulting in a high risk of lithium plating and potential safety hazards. If the distance is too large, it will waste negative electrode material, increase the cell volume, and reduce energy density.

[0096] For example, in this embodiment, along the winding direction of the cell 2, the distance by which the active material layer 2019 of the negative electrode 2012 extends beyond the active material layer 2019 of the positive electrode 2011 can be 20mm, 70mm, 98mm, 100mm, 180mm, 205mm, 310mm, 400mm, 500mm, 640mm, 750mm, or 800mm, or it can be a range formed by any two of the above values.

[0097] In some embodiments, at least one end of the battery cell 2 is provided with a tab 204 along the first direction; In the electrode unfolding direction, the shortest distance from the end of the protective layer 203 to the end of the tab 204 is M, in mm, and the value of M is within the range of 120≤M≤320.

[0098] When the distance M is too small, the heat generated by the tab can easily lead to excessively high local temperatures in the protective layer 203, which in turn causes thermal decomposition of the adhesive layer 2032 material, resulting in decreased or even failed adhesion performance. This may cause the protective layer to peel off, reducing the insulation protection effect on the tab area. When the distance M is too large, the distance between the bend and the tab is too far, resulting in an excessively long lead-out path for the tab, increasing internal resistance, and thus simultaneously affecting lithium-ion transport efficiency and exacerbating the risk of lithium plating.

[0099] For example, in this embodiment, the value of M can be 120, 150, 210, 280, 300, or 320, or it can be any range formed by any two of the above values.

[0100] In some embodiments, the value range of b satisfies: 0.01≤b≤0.3.

[0101] The ratio b of the total area of ​​the channels 20311 to the total area of ​​the separator 2031 affects the lithium-ion transport efficiency and the degree of electrolyte erosion of the adhesive layer 2032. When the ratio b is too large, although it is beneficial to lithium-ion migration, it will significantly increase the electrolyte penetration path, exacerbate the swelling risk of the adhesive layer 2032, weaken the adhesion strength, make it easy to peel off, and cause material loss. When the ratio b is too small, lithium-ion transport is hindered, and the risk of lithium plating increases.

[0102] For example, in this embodiment, the value of b can be 0.01, 0.05, 0.1, 0.15, 0.18, 0.2, 0.25, 0.3, etc., or it can be any range formed by any two of the above values.

[0103] In some embodiments, the thickness of the adhesive layer 2032 ranges from 10 μm to 50 μm; And / or, the thickness of the isolation layer 2031 ranges from 10 μm to 70 μm.

[0104] If the thickness of the 2032 adhesive layer is too small, the bonding strength will be insufficient, causing the active material to fall off; if the thickness is too large, it will increase the internal resistance of the cell, inhibit lithium ion migration, and thus increase the risk of lithium plating.

[0105] If the thickness of the 2031 isolation layer is too small, it will weaken its physical barrier ability and increase the risk of short circuit between the positive and negative electrodes; if the thickness is too large, it will reduce the proportion of active material and reduce the volumetric energy density.

[0106] For example, in this embodiment, the thickness of the adhesive layer 2032 can be 10μm, 15μm, 25μm, 30μm, 42μm, or 50μm, or it can be a range formed by any two of the above values.

[0107] For example, in this embodiment, the thickness of the isolation layer 2031 can be 10μm or 15μm or 25μm or 30μm or 42μm or 50μm or 55μm or 64μm or 70μm, or it can be a range formed by any two of the above values.

[0108] In some embodiments, the pore area of ​​a single channel 20311 ranges from 78.5 μm. 2 -196250μm 2 .

[0109] If the pore area of ​​a single channel 20311 is too small, it will restrict the lithium-ion transport channel, resulting in poor lithium-ion transport and exacerbating the risk of lithium plating; if the pore area of ​​a single channel 20311 is too large, it will increase the degree of erosion of the adhesive layer 2032 by the electrolyte, reduce the bonding stability, and cause the risk of material falling off.

[0110] For example, in this embodiment, the pore area of ​​a single channel 20311 can be 78.5 μm. 2 or 100μm 2 or 1000μm 2 or 20000μm 2 Or 196250μm 2 "etc." can also be the range formed by any two of the above values.

[0111] In some embodiments, the adhesive layer 2032 includes an adhesive area with adhesive and a non-adhesive area without adhesive, and the non-adhesive area is correspondingly provided with the area where the channel 20311 is formed in the isolation layer 2031.

[0112] The non-adhesive zone effectively prevents the colloid from clogging the pores 20311, ensuring smooth lithium-ion transport. Simultaneously, it reduces the contact area between the electrolyte and the colloid, slowing the swelling rate of the adhesive layer 2032, ensuring bonding strength, and reducing material loss.

[0113] In some embodiments, along the first direction, at least one end of the protective layer 203 extends beyond the active material layer 2019, with the extension distance ranging from 0.1 mm to 10 mm.

[0114] At least one end of the protective layer 203 extends beyond the active material layer 2019. When the extension distance is too large, it can easily lead to an extended lithium-ion transport path, increased internal resistance, and increased risk of lithium plating. When the extension distance is too small, it is difficult to effectively cover the edge of the active material layer 2019, thereby reducing the protective effect on the active material layer 2019 and posing a significant risk of material loss.

[0115] For example, in this embodiment, at least one end of the protective layer 203 extends beyond the active material layer 2019 along the first direction. The value of the distance extending beyond the active material layer 2019 can be 0.1 mm, 0.8 mm, 1 mm, 3 mm, 5 mm, or 10 mm, or it can be a range formed by any two of the above values.

[0116] In some embodiments, both sides of the current collector 2017 are coated with an active material layer 2019, and a protective layer 203 is attached to the area of ​​the active material layer 2019 on both sides located in the bending section.

[0117] It can provide symmetrical protection for the active material layer 2019 on both sides, effectively alleviating the peeling of the active material layer 2019 caused by uneven force on one side during bending.

[0118] Furthermore, when the protective layer 203 extends beyond the current collector 2017 along the first direction, the protective layers 203 on both sides can adhere to each other, further enhancing the structural stability of the R-corner 22 and preventing the active material layer 2019 from falling off.

[0119] In some embodiments, the straight portion 21 has R-corner portions 22 at both ends along the second direction, and the areas of the bent sections corresponding to the R-corner portions 22 at both ends are covered with protective layers 203.

[0120] By providing a protective layer 203 to the bending section areas corresponding to the R-corner 22 at both ends along the second direction, the structural strength of the cell edge area can be comprehensively strengthened, and electrode material loss can be suppressed.

[0121] In some embodiments, when the number of winding layers of the battery cell 2 is less than or equal to five, the active material layer 2019 of the bent section corresponding to the R-corner 22 is attached with a protective layer 203.

[0122] When the number of winding layers is small, the bending curvature of the electrode sheet is large, and the stress concentration effect is significant. Setting the protective layer 203 can effectively alleviate the cracking and shedding of the active material layer 2019. When the number of winding layers exceeds five, the stress distribution tends to be uniform, and the protective layer can be omitted to simplify the process.

[0123] Within the range of five or fewer winding layers, a protective layer 203 can be set on each layer, or it can be set only on the inner one to three layers where stress concentration is most significant.

[0124] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0125] The preparation of the example battery and the comparative battery includes the following steps: Measurement of dimensions, thickness, distance, and area Micrometers, calipers, scanning electron microscopes, etc. can be used to measure dimensions, thickness, distance, etc., and the area can be calculated from the dimensions.

[0126] Battery manufacturing (1) Preparation of the positive electrode: The prepared positive electrode active material, conductive agent acetylene black, and binder PVDF are mixed, and solvent NMP is added. The mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. Finally, it is cold-pressed and slit to obtain the positive electrode sheet. Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92~98):(4~1):(4~1).

[0127] (2) Preparation of negative electrode: The negative electrode active material, conductive agent acetylene black, thickener CMC, and binder SBR are mixed, and deionized water is added as a solvent. The mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained. The ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90~96): (4~2): (2~1): (4~1).

[0128] (3) Preparation of electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0129] (4) Preparation of the diaphragm: Polyethylene film is selected as the diaphragm.

[0130] (5) Preparation of lithium-ion batteries: The positive electrode, separator, and negative electrode are stacked in sequence and wound to form a bare battery cell. A protective layer is attached to the bent sections of the cell electrodes. The bare cell is then placed in a battery casing, which is a square casing. The battery is dried, injected with electrolyte, and then packaged, allowed to stand, formed, and volume-adjusted to obtain a lithium-ion battery.

[0131] The positive electrode active material can be selected from one or more lithium-containing positive electrode active materials, including lithium iron phosphate, ternary materials containing nickel, cobalt, and manganese, and lithium manganese iron phosphate; the negative electrode active material can be selected from one or more negative electrode active main materials, such as artificial graphite, natural graphite, silicon carbide, silicon oxide, and lithium titanate.

[0132] The testing method is as follows: Test Method 1: Battery Capacity Retention Rate Following the battery preparation method described above, corresponding lithium-ion batteries were prepared for each embodiment and comparative example. The parameters of the protective layer and cell in the lithium-ion batteries obtained in each embodiment and comparative example are shown in Table 1. All other structures are identical. The lithium-ion battery was charged at room temperature (25°C) with a constant current of 0.33C to the upper limit voltage, and then charged with a constant voltage of 0.33C until the current dropped to 0.05C. After standing for 5 minutes, the battery was discharged with a constant current of 0.33C to the lower limit voltage. This process was repeated three times to obtain the third discharge capacity Q1, which was taken as the fixed capacity.

[0133] The lithium-ion battery is charged at room temperature (25℃) with a constant current of 0.33C to the upper limit voltage, then charged with a constant voltage of 0.33C until the current drops to 0.05C. After resting for 5 minutes, the battery is discharged with a constant current of 0.33C to the lower limit voltage. This constitutes one cycle. After n cycles, the discharge capacity Qn of the battery on the nth cycle is recorded. The battery capacity retention rate is calculated using the formula "Battery capacity retention rate = Qn / Q1 × 100%". The number of cycles n when the capacity retention rate first falls below 80% is recorded as the number of cycles for that battery. If n is less than 1200, the battery is considered unqualified; if n is greater than or equal to 1200 and less than 1400, the battery is considered qualified; and if n is greater than or equal to 1400, the battery is considered good.

[0134] When the positive electrode active material of the battery is a nickel-cobalt-manganese ternary cathode, the upper limit voltage is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material of the battery is lithium iron phosphate, the upper limit voltage is 3.6V and the lower limit voltage is 2.5V.

[0135] In this test, the active material for the positive electrode of the battery was selected from a nickel-cobalt-manganese ternary LiNi alloy. 0.6 Co 0.2 Mn 0.2Taking O2 as an example, the mass ratio of positive electrode active material: conductive agent: binder meets 96:2:2; the negative electrode active material is selected from artificial graphite, and the ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2.

[0136] Test Method 2: Lithium Plating in the Battery Following the battery preparation method described above, corresponding lithium-ion batteries were prepared for each embodiment and comparative example. The parameters of the protective layer and cell in the lithium-ion batteries obtained in each embodiment and comparative example are shown in Table 1. All other structures are identical. The lithium-ion battery was charged at room temperature (25°C) with a constant current of 0.33C to the upper limit voltage, then charged at a constant voltage until the current dropped to 0.05C. After resting for 5 minutes, the battery was discharged with a constant current of 0.33C to the lower limit voltage. This constituted one cycle, and 2000 cycles were performed. Then, the lithium-ion battery was charged at 0.33C to the upper limit voltage, with a cutoff current less than or equal to 0.05C, resulting in a fully charged battery.

[0137] Disassemble the battery, then remove the electrodes and observe the lithium plating on the surface of the negative electrode in the bending section. The portion where the projection of a single protective layer coincides with the electrode is the first region, and the lithium plating area of ​​the first region is recorded as S10. The area of ​​a single protective layer adhered to the active material layer in the bending section is recorded as S20. Calculate the percentage of the lithium plating area on the surface of the negative electrode bending section using the formula: (S10 / S20) × 100%. If the lithium plating area on the surface of the negative electrode bending section is less than 10%, it is considered slight lithium plating; if it is between 10% and 50%, it is considered moderate lithium plating; and if it is greater than 50%, it is considered severe lithium plating. Batteries with severe lithium plating are considered unqualified products.

[0138] When the positive electrode active material of the battery is a nickel-cobalt-manganese ternary cathode, the upper limit voltage is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material of the battery is lithium iron phosphate, the upper limit voltage is 3.6V and the lower limit voltage is 2.5V.

[0139] In this test, the positive electrode active material of the battery was selected from a nickel-cobalt-manganese ternary LiNi alloy. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, the mass ratio of positive electrode active material: conductive agent: binder satisfies 96:2:2; the negative electrode active material is selected from artificial graphite, and the ratio of negative electrode active material: conductive agent: thickener: binder satisfies 95:2:1:2.

[0140] Table 1

[0141] Regarding the test results, referring to Table 1 above, the explanation is as follows: As can be seen from Examples 1-16, when the formula for a×b×c satisfies the range 0.3×10 -2 ≤a×b×c≤61.1×10 -2 At that time, the battery capacity retention rate test showed that the battery capacity remained good or qualified, and no unqualified cases were found; the lithium plating test showed that the lithium plating was slight or moderate, and no severe lithium plating was found; the performance requirements were met.

[0142] In Comparative Example 1, the value of the formula a×b×c was below the lower limit. The battery lithium plating test showed severe lithium plating, failing to meet performance requirements. In Comparative Examples 2 and 3, the value of the formula a×b×c exceeded the upper limit. The battery capacity retention test showed that the battery capacity retention was unqualified, failing to meet performance requirements.

[0143] According to an embodiment of the present invention, another aspect provides a battery device comprising: a plurality of batteries as described above.

[0144] The battery device also includes a housing for containing the batteries, which are electrically connected by stacking multiple batteries in the housing in series or parallel.

[0145] According to an embodiment of the present invention, in another aspect, an electrical device is also provided, comprising: an electrical device body, and a battery device as described above that is electrically connected to the electrical device body.

[0146] In this embodiment, the electrical equipment can specifically be electronic devices, electric vehicles, or energy storage systems. Electronic devices include smartphones, tablets, or laptops; electric vehicles include pure electric vehicles, hybrid electric vehicles, or electric motorcycles; and energy storage systems are used for grid energy storage or home energy management.

[0147] In this embodiment, the electrical equipment can specifically be an electric vehicle, a portable electronic device, or an energy storage system. Electric vehicles include electric cars, electric bicycles, or electric motorcycles; portable electronic devices include smartphones, tablets, or laptops; and energy storage systems include home energy storage devices or grid-scale energy storage units.

[0148] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and all such modifications and variations fall within the scope defined by the present invention.

Claims

1. A battery, characterized in that, include: The battery casing (1) has an opening (11) formed at least at one end along a first direction. The battery cell (2) is adapted to be disposed inside the battery case (1) along the first direction, and the battery cell (2) is manufactured by winding; the battery cell (2) includes a flat portion (21) and an R-corner portion (22) located at at least one end of the flat portion (21) along the second direction. The battery cell (2) includes an electrode (201) and an insulating film (202). The electrode (201) includes a positive electrode (2011) and a negative electrode (2012). The insulating film (202) is located between adjacent positive electrode (2011) and negative electrode (2012). The electrode (201) includes a current collector (2017) and an active material layer (2019) coated on at least one side of the current collector (2017), wherein the thickness of the active material layer (2019) in a single electrode (201) is a proportion of the thickness of the electrode (201); The electrode (201) includes a bent section in a bent state, and multiple layers of the bent section form the R-corner (22). The battery cell (2) further includes a protective layer (203), which is attached to the active material layer (2019) of the bent section; the protective layer (203) includes an isolation layer (2031) and an adhesive layer (2032), the adhesive layer (2032) is disposed between the isolation layer (2031) and the bent section, the isolation layer (2031) is provided with a channel (20311), and the total area of ​​the channel (20311) accounts for b of the total area of ​​the isolation layer (2031); Along the first direction, the width of the active material layer (2019) of the negative electrode (2012) is greater than the width of the active material layer (2019) of the positive electrode (2011), and the active material layer (2019) of the negative electrode (2012) extends beyond the active material layer (2019) of the positive electrode (2011) at least one end along the first direction, wherein the distance by which one end extends is c, in mm; a, b, and c satisfy the relation: 0.3 × 10 -2 ≤a×b×c≤61.1×10 -2 The unit is mm.

2. The battery according to claim 1, characterized in that, The range of values ​​for c satisfies: 0.4≤c≤2.5, unit is mm.

3. The battery according to claim 1, characterized in that, The active material layer (2019) of the negative electrode (2012) extends beyond the active material layer (2019) of the positive electrode (2011) at both ends along the first direction.

4. The battery according to claim 3, characterized in that, The sum of the dimensions of the active material layer (2019) of the negative electrode (2012) extending beyond the active material layer (2019) of the positive electrode (2011) along the first direction is c2, in mm, and satisfies: 0.8≤c2≤5.

5. The battery according to claim 1, characterized in that, The active material layer (2019) of the negative electrode (2012) extends beyond one end of the current collector (2017) of the positive electrode (2011) along the first direction by a distance d in mm, satisfying: 0.45≤d≤2.

4.

6. The battery according to claim 1, characterized in that, The positive electrode (2011) includes a current collector (2017) and an active material layer (2019) disposed on at least one surface of the current collector (2017). A first insulating layer (20111) is also disposed at at least one end along the first direction. The first insulating layer (20111) is disposed on the current collector (2017), and the width of the first insulating layer (20111) along the first direction ranges from 1 mm to 10 mm.

7. The battery according to claim 6, characterized in that, The first insulating layer (20111) and the active material layer (2019) of the positive electrode (2011) at least partially overlap in the first direction.

8. The battery according to claim 1, characterized in that, The negative electrode sheet (2012) is further provided with a second insulating layer (20121) at at least one end along the first direction; along the first direction, the width of the second insulating layer (20121) ranges from 1mm to 10mm.

9. The battery according to claim 1, characterized in that, Along the first direction, at least one end of the insulating film (202) extends beyond the end of the positive electrode (2011), and the distance extending beyond the end ranges from 0.6 mm to 7.3 mm.

10. The battery according to claim 1, characterized in that, Along the first direction, at least one end of the insulating film (202) extends beyond the end of the negative electrode sheet (2012), and the distance extending beyond the end ranges from 0.4 mm to 4 mm.

11. The battery according to claim 1, characterized in that, The range of values ​​for 'a' satisfies: 0.7≤a≤0.98。 12. The battery according to claim 11, characterized in that, When the electrode (201) is the negative electrode (2012), the value range of a satisfies: 0.7≤a≤0.

96.

13. The battery according to claim 11, characterized in that, When the electrode (201) is the positive electrode (2011), the value range of a satisfies: 0.75≤a≤0.

98.

14. The battery according to claim 12, characterized in that, The thickness of the current collector (2017) of the negative electrode (2012) ranges from 4 μm to 12 μm; And / or, the thickness of the active material layer (2019) of the negative electrode (2012) ranges from 30 μm to 200 μm.

15. The battery according to claim 13, characterized in that, The thickness of the current collector (2017) of the positive electrode (2011) ranges from 6 μm to 18 μm; And / or, the thickness of the active material layer (2019) of the positive electrode (2011) ranges from 30 μm to 210 μm.

16. The battery according to claim 1, characterized in that, The thickness of the insulating film (202) ranges from 5μm to 20μm.

17. The battery according to claim 1, characterized in that, Along the winding direction of the cell (2), the active material layer (2019) of the negative electrode (2012) at at least one end extends beyond the active material layer (2019) of the positive electrode (2011), and the distance of the extension ranges from 20mm to 800mm.

18. The battery according to claim 1, characterized in that, Along the first direction, at least one end of the battery cell (2) is provided with a tab (204). In the electrode unfolding direction, the shortest distance between the end of the protective layer (203) and the end of the tab (204) is M, in mm, and the value range of M satisfies: 120≤M≤320.

19. The battery according to any one of claims 1 to 18, characterized in that, The value range of b satisfies: 0.01≤b≤0.

3.

20. The battery according to any one of claims 1 to 18, characterized in that, The thickness of the adhesive layer (2032) ranges from 10 μm to 50 μm; And / or, the thickness of the isolation layer (2031) ranges from 10 μm to 70 μm.

21. The battery according to any one of claims 1 to 18, characterized in that, The pore area of ​​a single channel (20311) ranges from 78.5 μm. 2 -196250μm 2 .

22. The battery according to any one of claims 1 to 18, characterized in that, The adhesive layer (2032) includes an adhesive area with adhesive and a non-adhesive area without adhesive. The non-adhesive area is provided in a manner corresponding to the area in the isolation layer (2031) where the channel (20311) is formed.

23. The battery according to any one of claims 1 to 18, characterized in that, Along the first direction, at least one end of the protective layer (203) extends beyond the active material layer (2019), with the extension distance ranging from 0.1 mm to 10 mm.

24. The battery according to any one of claims 1 to 18, characterized in that, Both sides of the current collector (2017) are coated with the active material layer (2019), and the active material layer (2019) on both sides is attached with the protective layer (203) in the area of ​​the bending section.

25. The battery according to any one of claims 1 to 18, characterized in that, The straight portion (21) forms the R-corner portion (22) at both ends along the second direction, and the area of ​​the bent section corresponding to the R-corner portion (22) at both ends is covered with the protective layer (203).

26. The battery according to any one of claims 1 to 18, characterized in that, Within the range where the number of winding layers of the battery cell (2) is less than or equal to five, the active material layer (2019) of the bent section corresponding to the R corner (22) is attached with the protective layer (203).

27. A battery device, characterized in that, It includes a plurality of batteries as described in any one of claims 1 to 26.

28. An electrical appliance, characterized in that, It includes an electrical device body and a battery device as described in claim 27 above, which is electrically connected to the electrical device body.

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