A winding type secondary battery cell, a method of manufacturing the same, and an application thereof

Abstract

This invention provides a wound-type secondary battery cell, its preparation method, and its application, relating to the field of lithium-ion battery technology. The wound-type secondary battery cell of this invention includes a positive electrode, a negative electrode, a separator located between the positive and negative electrodes, an electrolyte, and a solid electrolyte. The solid electrolyte is coated between the positive and negative electrodes at the corner of the wound structure of the wound-type secondary battery cell. The electrolyte contains a positive electrode protective additive, which includes sulfur-containing substances and borates, added in an amount of 0.1~2wt%. This invention effectively solves the gap problem at the corner by coating a solid electrolyte between the positive and negative electrodes at the corner position and optimizing the electrolyte, thus promoting lithium-ion transport efficiency and significantly improving the cycle performance of the wound-type secondary battery cell. The lithium-ion secondary battery can maintain 80% cycle capacity for up to 1900 cycles.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a wound secondary battery cell, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries, with their superior high operating voltage, long cycle life, and environmental compatibility, have become the preferred solution in the current energy storage field, widely penetrating key application scenarios such as pure electric passenger vehicles, hybrid vehicles, and smart grid energy storage. However, with the continuous iteration and upgrading of related application technologies, the market has placed more stringent technical requirements on the safety, reliability, electrochemical kinetic performance, and high-temperature cycle stability of lithium-ion batteries. It is worth noting that consumer range anxiety remains one of the core bottlenecks restricting the large-scale adoption of lithium-ion batteries in the passenger vehicle sector, and the promotion and application of fast charging technology has proven to be an effective way to alleviate this anxiety. In the industrial manufacturing process of lithium-ion batteries, there are two main core technology routes: stacking and winding. Among them, the winding process has become the mainstream manufacturing method in the industry due to its significant advantages of high production efficiency and stable product yield. However, due to the inherent characteristics of the winding structure, microscopic gaps are easily formed in the corner areas of the battery electrodes. When the battery enters the later stages of cycling and the electrolyte is depleted, these gaps will further expand, leading to the interruption of the lithium-ion transport path (i.e., the "lithium-ion broken bridge phenomenon"), triggering a series of side reactions, and ultimately causing a sharp decline in battery cycle performance (commonly known as "cycle plunge"). Especially in application scenarios where ultra-fast charging technology is combined with the winding process, the safety and performance risks caused by the above-mentioned technical defects are further amplified.

[0003] Therefore, optimizing solutions to this technical problem has become a key issue that the industry urgently needs to address. Summary of the Invention

[0004] This invention addresses the shortcomings and deficiencies of current wound secondary battery cells, such as poor cycle performance and severe degradation, by providing a wound secondary battery cell that significantly improves cycle performance through specific structural design and electrolyte optimization.

[0005] Another object of the present invention is to provide a method for preparing a wound secondary battery cell.

[0006] Another object of the present invention is to provide a battery cell module.

[0007] Another object of the present invention is to provide a battery pack.

[0008] Another object of the present invention is to provide an electrical device.

[0009] In a first aspect, the present invention protects a wound secondary battery cell, comprising a positive electrode, a negative electrode, a separator located between the positive electrode and the negative electrode, an electrolyte, and a solid electrolyte, wherein the solid electrolyte is coated between the positive electrode and the negative electrode at the corner of the wound structure of the wound secondary battery cell. The electrolyte contains a positive electrode protection additive, which includes sulfur-containing substances and borates, and the amount added is 0.1~2wt%.

[0010] According to the wound secondary battery cell protected by the present invention, preferably, the sulfur-containing substance is selected from any one or more of 1,3-propanesulfonyl lactone or methane disulfonate; and / or, the borate is selected from one or more of lithium difluorooxalate borate or lithium dioxalate borate.

[0011] According to the wound secondary battery cell protected by the present invention, preferably, the positive electrode protective additive is a mixture of methylene methane disulfonate and lithium difluorooxalate borate or the positive electrode protective additive is a mixture of methylene methane disulfonate, lithium difluorooxalate borate and 1,3-propane sulpholactone. The preferred mixing mass ratio of methylene methane disulfonate and lithium difluorooxalate borate is (0.2~0.8):(0.2~0.8), more preferably 0.5:0.3; The preferred mixing ratio of methylene disulfonate, lithium difluorooxalate borate, and 1,3-propanesulfonyl lactone is (0.2 ~ 0.8):(0.2 ~ 0.8):(0.2 ~ 0.8), and more preferably 0.5:0.5:0.3.

[0012] According to the wound secondary battery cell protected by the present invention, preferably, the coating position of the solid electrolyte has a trajectory curvature κ ≥ 0.025 mm. -1 The corner location.

[0013] According to the wound secondary battery cell protected by the present invention, preferably, the thickness of the solid electrolyte coating is 0.1~5μm, more preferably 1~3μm.

[0014] According to the wound secondary battery cell protected by the present invention, preferably, the coating thickness of the solid electrolyte starts from the beginning and end of the uncoated area and increases gradually to the final coating thickness, wherein the initial coating thickness is 10% or more of the final coating thickness.

[0015] According to the wound secondary battery cell protected by the present invention, preferably, the solid electrolyte is coated on any one or more of the surfaces of the negative electrode, the positive electrode, or the diaphragm that are in contact with the positive and negative electrodes, preferably on the negative electrode.

[0016] According to the wound secondary battery cell protected by the present invention, preferably, the solid electrolyte satisfies at least one of the following conditions: The sodium-ion superconductor structure solid electrolyte is lithium aluminum titanium phosphate (Li). 1-x Al x Ti 2-x (PO4)3, 0 < x ≤ 0.5, preferably Li 0.7 Al 0.3 Ti 1.7 (PO4)3 or Li 1.4 Al 0.4 Ti 1.6 (PO4)3; Garnet-structured solid electrolytes are lanthanum zirconium oxide (LLZO) or tantalum-doped lithium lanthanum zirconium oxide (Li). 7-x La3Zr 2- x Ta x O 12 0 < x ≤ 0.4, preferably Li 6.75 La3Zr 1.75 Ta 0.2 5O 12 ; The perovskite-structured solid electrolyte is lithium lanthanum titanium oxide (Li). 3x La 2 / 3-x TiO3), 0.04≤x≤0.17, preferably Li 0.34 La 0.56 TiO3.

[0017] According to the wound secondary battery cell protected by the present invention, preferably, the electrolyte further comprises any one or more of vinyl sulfate, vinylene carbonate, and fluorovinylene carbonate, preferably in a content of 0.5~10 wt%; And / or, the separator is a polyethylene film, the polyethylene film is coated with PVDF coating on both sides, and a boehm ceramic layer is coated on the surface in contact with the positive electrode.

[0018] Secondly, the present invention also specifically protects a method for preparing a wound secondary battery cell, characterized by comprising the following steps: A solid electrolyte is coated in a predetermined area of ​​the positive electrode, negative electrode, or separator, wherein the predetermined area corresponds to a winding trajectory curvature κ ≥ 0.025 mm. -1 The corner location; The positive electrode, separator, and negative electrode are wound together, with the separator positioned between the positive and negative electrodes, to produce a semi-finished wound battery cell. The wound battery cell semi-finished product is packed into a packaging shell, dried, and then injected with electrolyte. The wound secondary battery cell is obtained through vacuum sealing, settling, formation, and shaping.

[0019] Thirdly, the present invention also protects a battery cell module, including the wound secondary battery cell.

[0020] Fourthly, the present invention also protects a battery pack including the wound secondary battery cell or battery cell module.

[0021] Fifthly, the present invention also protects an electrical device comprising the wound secondary battery cell or battery cell module or battery pack.

[0022] Sixthly, the present invention also protects a vehicle including the wound-type battery cell or battery cell module or battery pack.

[0023] Beneficial effects: This invention provides a wound secondary battery cell. By coating a solid electrolyte between the positive and negative electrodes at the corner position and optimizing the electrolyte, the gap problem at the corner is effectively solved, and the lithium-ion transport efficiency is promoted. This significantly improves the cycle performance of the wound secondary battery cell, and the lithium-ion secondary battery can maintain a cycle capacity of 80% for up to 1900 cycles.

[0024] The method for preparing the wound two-cell battery of the present invention is simple and has excellent cycle performance, and can be widely used in the preparation of cell modules, battery packs and electrical devices. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is one of the structural schematic diagrams of the wound secondary battery cell provided by the present invention.

[0027] Figure 2 This is the second schematic diagram of the structure of the wound secondary battery cell provided by the present invention.

[0028] Figure 3 This is the third schematic diagram of the structure of the wound secondary battery cell provided by the present invention.

[0029] Figure 4 This is the fourth schematic diagram of the structure of the wound secondary battery cell provided by the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] In a specific embodiment, the present invention provides a wound secondary battery cell, including a positive electrode, a negative electrode, a separator located between the positive electrode and the negative electrode, an electrolyte, and a solid electrolyte, wherein the solid electrolyte is coated between the positive electrode and the negative electrode at the corner of the wound structure of the wound secondary battery cell; The electrolyte contains a positive electrode protection additive, which includes sulfur-containing substances and borates, and the amount added is 0.1~2wt%.

[0032] It should be noted that: In the wound secondary battery cell of the present invention, a positive electrode protection additive is added to the electrolyte, which can optimize lithium-ion transport efficiency, ensure transport stability, and thus improve cycle performance in conjunction with solid electrolyte coating.

[0033] During the first charge and discharge cycle of the battery, the positive electrode protectant preferentially undergoes an oxidative polymerization reaction on the positive electrode surface, forming a dense, uniform, and highly lithium-ion conductive solid electrolyte interphase (CEI) film. This CEI film effectively prevents the continuous oxidative decomposition of electrolyte solvent molecules on the positive electrode surface, reduces the rate of electrolyte depletion, and avoids obstruction of lithium-ion transport at corners. The CEI film formed by the positive electrode protectant also isolates the positive electrode active material from direct contact with the electrolyte, reducing the ineffective consumption of lithium ions in the electrolyte.

[0034] The gaps at the electrode corners caused by the winding process are a core factor contributing to reduced cycle performance. Solid-state electrolytes (SSEs) possess excellent formability and interfacial adhesion, allowing them to directly fill the gaps at electrode corners after coating, forming a continuous ion-conducting medium. Simultaneously, SSEs exhibit stable mechanical properties. During the volume expansion / contraction of batteries in long-term charge-discharge cycles, their rigidity and bonding characteristics constrain electrode deformation, preventing further widening of gaps due to electrolyte consumption and electrode displacement. This eliminates breakpoints in the lithium-ion transport path, ensuring smooth lithium-ion migration through the continuous channels formed by the SSE throughout the cycle. SSEs also possess high lithium-ion conductivity and low interfacial impedance, enabling them to partially replace liquid electrolytes for efficient lithium-ion transport. In some specific embodiments, the amount of positive electrode protective additive added to the electrolyte mentioned in this invention is 0.1% to 2% of the mass of the positive electrode electrolyte. For example, it can be a point value such as 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, or any range of values.

[0035] In some specific embodiments, the sulfur-containing positive electrode protective additive mentioned in this invention may be selected from any one or more of 1,3-propanesulfonyl lactone (PS) or methylene disulfonate (MMDS), and the borate may be selected from one or more of lithium difluorooxalate borate (LiODFB) or lithium bis(oxalate borate) (LiBOB).

[0036] In some specific embodiments, the positive electrode protective additive mentioned in this invention is a mixture of methylene methane disulfonate and lithium difluorooxalate borate, or the positive electrode protective additive is a mixture of methylene methane disulfonate, lithium difluorooxalate borate, and 1,3-propanesulfonyl lactone.

[0037] In some specific embodiments, in order to better promote the improvement of the cycle performance of the wound secondary battery cell, the positive electrode protection additive mentioned in this invention is preferably one of the following combinations: The positive electrode protective additive is a mixture of methylene methane disulfonate and lithium difluorooxalate borate, preferably with a mass ratio of (0.2~0.8):(0.2~0.8), more preferably 0.5:0.3; The positive electrode protective additive is a mixture of methylene methane disulfonate, lithium difluorooxalate borate and 1,3-propane sulfonyl lactone, preferably in a mixing ratio of (0.2~0.8):(0.2~0.8):(0.2~0.8), more preferably 0.5:0.5:0.3.

[0038] In some specific embodiments, the electrolyte mentioned in this invention may further contain a non-aqueous solvent, wherein the non-aqueous solvent is selected from at least one carbonate. The carbonate compound mentioned in this invention may be ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or combinations thereof.

[0039] In some specific embodiments, the electrolyte mentioned in this invention may also contain a carboxylic acid ester solvent, wherein the carboxylic acid ester solvent is selected from propyl propionate (PP), ethyl propionate (EP), propyl acetate (PA), ethyl acetate (EA), and combinations thereof.

[0040] In some specific embodiments, the electrolyte mentioned in this invention may further contain an electrolyte lithium salt, wherein the lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiTFSI), lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalate borate), lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium tri(trifluoromethylsulfonyl)methyl, or lithium bis(trifluoromethylsulfonyl)imide.

[0041] In some specific embodiments, the electrolyte mentioned in this invention preferably contains one or more of vinyl sulfate (DTD), vinylene carbonate (VC), and fluorovinylene carbonate (FEC), preferably in a content of 0.5 to 10 wt%.

[0042] In other embodiments, to achieve better cycle performance and enhance the promoting effect of solid electrolyte coating, the coated position of the wound secondary battery cell mentioned in this invention is more preferably such that the trajectory curvature κ ≥ 0.025 mm. -1 The corner location.

[0043] In some specific embodiments, the solid electrolyte coating width mentioned in this invention is determined according to the width of the positive and negative electrode sheets, covering the width of the positive and negative electrode sheets.

[0044] The terminology for trajectory curvature κ used in this invention is explained as follows: Trajectory curvature is a geometric quantity that describes the degree of curvature of a curve trajectory. Its core function is to quantify the degree of curvature of a curve at a certain point. The greater the curvature, the more obvious the curvature of the curve at that point; when the curvature is 0, the curve is a straight line at that point.

[0045] For a smooth curve in a plane or space, the definition of its trajectory curvature k is derived based on the radius of curvature R: Radius of curvature R: The radius of the osculating circle of a curve at a point (the circle tangent to the curve at that point and with the same curvature). Relationship between curvature k and radius of curvature: κ = 1 / R, meaning the curvature is the reciprocal of the radius of curvature.

[0046] Coating position control can effectively fill corner gaps, and at the same time avoid uneven bonding between multiple layers of wound electrodes due to excessive coating position.

[0047] In some specific embodiments, in order to achieve a better coating and filling effect, the coating thickness of the solid electrolyte mentioned in this invention is 0.1~5μm, for example, it can be a point value or any range of values ​​such as 0.1μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 4μm, 5μm, preferably 1~3μm.

[0048] In some specific embodiments, the coating thickness of the solid electrolyte mentioned in this invention starts from the beginning and end of the uncoated area and increases gradually to the final coating thickness, preferably the initial coating thickness is 10% or more of the final coating thickness.

[0049] At the starting end of the coating process, the coating thickness is gradually increased to the final coating thickness at a rate of 10% or more of the initial coating thickness. The final coating thickness is maintained until the coating process is close to the end. Then, the coating thickness is gradually reduced to 10% or more of the final coating thickness, and the coating process is ended. Preferably, the coating thickness at the beginning and end of the uncoated areas at both ends is the same.

[0050] In a specific embodiment, the solid electrolyte is coated on any one or more of the surfaces of the negative electrode, the positive electrode, or the membrane that are in contact with the positive and negative electrodes, preferably on the negative electrode.

[0051] The multi-faceted coating can be any combination of the positive electrode, negative electrode, contact surface between the separator and the positive electrode, and contact surface between the separator and the negative electrode.

[0052] In specific embodiments, the solid electrolyte coating mentioned in this invention between the positive and negative electrodes at the corner of the wound structure of the wound secondary battery cell does not specifically define the coating interface. For example, it can be any of the following coating methods: One method is to coat the solid electrolyte onto the surface where the positive electrode and the separator contact at the corner of the wound structure of the wound secondary battery cell.

[0053] Method Two: Solid electrolyte is coated on the surface where the negative electrode and the separator contact at the corner of the wound structure of the wound secondary cell.

[0054] Method 3: Solid electrolyte is coated on the surface of the separator and negative electrode at the corner of the wound structure of the wound secondary cell.

[0055] Method 4: Solid electrolyte is coated on the surface of the separator and positive electrode at the corner of the wound structure of the wound secondary cell.

[0056] In some specific embodiments, the coating method of the present invention can be used alone or in combination. For example, it can be coated simultaneously on the surface of the separator in contact with the negative electrode and the surface of the separator in contact with the positive electrode at the corner of the winding structure of the wound cell; or it can be coated simultaneously on the surface of the positive electrode in contact with the separator and the surface of the negative electrode in contact with the separator. For example, it can be coated on the surface where the positive electrode and the diaphragm are in contact, and on the surface where the diaphragm and the positive electrode are in contact.

[0057] In specific embodiments, the solid electrolyte oxide solid electrolyte mentioned in this invention can be selected from any one of sodium ion superconductor structure, garnet structure, and perovskite structure.

[0058] In some specific exemplary embodiments, the electrolyte may be a sodium-ion superconductor structure solid electrolyte, such as lithium aluminum titanium phosphate (Li). 1-x Al x Ti 2-x (PO4)3, 0 ≤ x ≤ 0.5, preferably Li 0.7 Al 0.3 Ti 1.7 (PO4)3 or Li 1.4 Al 0.4 Ti 1.6 (PO4)3.

[0059] In some specific exemplary embodiments, the electrolyte may be a garnet-structured solid electrolyte, such as lanthanum zirconium oxide (LLZO) or tantalum-doped lithium lanthanum zirconium oxide (Li). 7-x La3Zr 2-x Ta x O 12 0 ≤ x ≤ 0.4, preferably Li 6.75 La3Zr 1.75 Ta 0.2 5O 12 .

[0060] In some specific exemplary embodiments, the electrolyte may be a perovskite-structured solid electrolyte, such as lithium lanthanum titanium oxide (Li). 3x La 2 / 3-x TiO3), 0.04≤x≤0.17, preferably Li 0.34 La 0.56 TiO3.

[0061] In some specific embodiments, the separator mentioned in this invention is preferably a polyethylene film coated with PVDF coating on both sides, and a boehm ceramic layer is coated on the positive electrode contact surface. The thickness of each layer can refer to the conventional thickness range.

[0062] In some specific embodiments, the present invention also provides a method for preparing a wound secondary battery cell, comprising the following steps: A solid electrolyte is coated in a predetermined area of ​​the positive electrode, negative electrode, or separator, wherein the predetermined area corresponds to a winding trajectory curvature κ ≥ 0.025 mm. -1 The corner location; The positive electrode, separator, and negative electrode are wound together, with the separator positioned between the positive and negative electrodes, to produce a semi-finished wound battery cell. The wound battery cell semi-finished product is packed into a packaging shell, dried, and then injected with electrolyte. The wound secondary battery cell is obtained through vacuum sealing, settling, formation, and shaping.

[0063] In some specific embodiments, the positive electrode mentioned in this invention includes a positive current collector and a positive active material layer on its surface, wherein the positive active material layer includes a positive active material and a conductive agent. The negative electrode includes a negative current collector and a negative active material layer located on the negative current collector.

[0064] In the method for preparing the wound secondary battery cell mentioned in this invention, the method for preparing the positive electrode is as follows: Ternary material LiNi 0.80 Co 0.10 Mn 0.10 O2 is used to mix active material, conductive carbon (SP), carbon nanotubes (CNTs) and polyvinylidene fluoride (PVDF) in a weight ratio of 96.3:0.7:1:2 in a solvent (N-methylpyrrolidone) and stir evenly to obtain positive electrode slurry.

[0065] Aluminum foil is used as the positive electrode current collector. The positive electrode current collector coated with positive electrode slurry is dried at 80~90℃, for example 85℃, and then cold-pressed, cut into sheets and slit to prepare the positive electrode.

[0066] In the method for preparing the wound secondary battery cell mentioned in this invention, the method for preparing the negative electrode is as follows: Artificial graphite, conductive carbon (SP), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were mixed in deionized water at a weight ratio of 96.4:1:1.2:1.4 and stirred evenly to obtain the negative electrode slurry.

[0067] Using copper foil as the negative electrode current collector, the negative electrode current collector coated with negative electrode slurry is dried at 110~130℃, for example 120℃, and then cold-pressed, cut into sheets and slit to prepare the negative electrode.

[0068] In the method for preparing the wound secondary battery cell mentioned in this invention, the electrolyte is prepared as follows: In an argon atmosphere, solvents EC, EMC, and DMC (volume ratio 3:5:2) are added. Based on the total mass of the electrolyte, 0.5wt% FEC and 0.5wt% DTD are added, along with positive electrode protection additives (0.1~2wt%). Subsequently, LiPF6 is added at a mass ratio of 12.5% ​​to obtain the electrolyte.

[0069] Preparation of the separator: A polyethylene film with a substrate thickness of 7 μm was used as the separator. A 5 μm PVDF coating was applied to both sides, and a 3 μm thick boehm ceramic layer was applied to its surface to obtain the separator.

[0070] A 3µm solid electrolyte is coated onto the membrane at the corresponding corner of the positive or negative electrode, or a solid electrolyte is coated onto the corner of the separator, and then dried at 60°C after solidification.

[0071] Assembly of lithium-ion cells: The positive electrode, separator, and negative electrode are wound together, with the separator positioned between the positive and negative electrodes to provide isolation. The side coated with boehmite ceramic layer is aligned with the positive electrode. The cells are then placed in an aluminum-plastic film, dried at 80°C, and injected with the prepared electrolyte. After vacuum sealing, settling, formation, and shaping, the lithium-ion cell is successfully assembled.

[0072] Performance testing: Cyclic storage test: At 25℃, the lithium-ion battery was first fully discharged at 1C and then tested. The test procedure was as follows: the lithium-ion battery was charged at a constant current of 3C to a voltage of 4.25V, then charged at a constant voltage of 4.25V to a current of 0.05C. After resting for 5 minutes, the lithium-ion battery was discharged at a constant current of 1C to a voltage of 2.8V. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. The lithium-ion cell was subjected to multiple charge-discharge cycles using the above method until the discharge capacity of the lithium-ion secondary battery decreased to 80%, and the number of cycles of the lithium-ion cell was recorded.

[0073] In a specific embodiment, the present invention also provides a battery cell module, including the wound secondary battery cell.

[0074] In a specific embodiment, the present invention also provides a battery pack, including the wound secondary battery cell or the battery cell module.

[0075] In a specific embodiment, the present invention also provides an electrical device, including the wound 200-cell battery, the battery cell module, or the battery pack.

[0076] In a specific embodiment, the present invention also provides a vehicle, including the wound battery cell, the battery cell module, or the battery pack. Example 1 A type of wound secondary battery cell, such as Figure 1The battery includes a positive electrode, a negative electrode, a separator between the positive and negative electrodes, an electrolyte, and a solid electrolyte. The solid electrolyte is coated on the surface of the positive electrode at the corner of the wound structure of the wound secondary battery cell, where it contacts the separator; the coating location is where the trajectory curvature κ ≥ 0.025 mm. -1 At the corner position, the coating width is the same as the width of the positive electrode sheet.

[0077] The solid electrolyte is Li 0.7 Al 0.3 Ti 1.7 (PO4)3, coating thickness 3μm, solid electrolyte coating starts from the uncoated area and increases with the initial coating thickness gradient to the final coating thickness, the initial coating thickness is 0.3μm.

[0078] The positive electrode includes a positive current collector and a positive active material layer on its surface, wherein the positive active material layer includes a positive active material and a conductive agent. The negative electrode includes a negative current collector and a negative active material layer located on the negative current collector.

[0079] The preparation method of the positive electrode is as follows: Ternary material LiNi 0.80 Co 0.10 Mn 0.10 O2 is used to mix active material, conductive carbon (SP), carbon nanotubes (CNTs) and polyvinylidene fluoride (PVDF) in a weight ratio of 96.3:0.7:1:2 in a solvent (N-methylpyrrolidone) and stir evenly to obtain positive electrode slurry.

[0080] Aluminum foil was used as the positive electrode current collector. The positive electrode current collector coated with slurry was dried at 85°C and then cold-pressed, cut into sheets and slit to prepare the positive electrode.

[0081] The preparation method of the negative electrode is as follows: Artificial graphite, conductive carbon (SP), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were mixed in deionized water at a weight ratio of 96.4:1:1.2:1.4 and stirred evenly to obtain the negative electrode slurry.

[0082] Copper foil was used as the negative electrode current collector. The negative electrode current collector coated with negative electrode slurry was dried at 120°C and then cold-pressed, cut into sheets and slit to prepare the negative electrode.

[0083] The electrolyte is prepared as follows: In an argon atmosphere, solvents EC, EMC, and DMC (volume ratio 3:5:2) were added. Based on the total mass of the electrolyte, 0.5 wt% FEC and 0.5 wt% DTD were added, followed by LiPF6 (12.5% ​​by mass) and PS (0.5% by mass) to obtain the electrolyte.

[0084] Preparation of the separator: A polyethylene film with a substrate thickness of 7 μm was used as the separator. A 5 μm PVDF coating was applied to both sides, and a 3 μm thick boehm ceramic layer was applied to its surface to obtain the separator.

[0085] A 3µm solid electrolyte layer was coated onto the membrane at the corresponding corner of the positive electrode, and then dried at 60°C after solidification.

[0086] This embodiment also provides a method for assembling a factor lithium-ion battery cell: the above-mentioned positive electrode, separator, and negative electrode are wound together, with the separator positioned between the positive and negative electrodes to provide isolation. The side coated with boehmite ceramic layer is aligned with the positive electrode. The battery cell is then placed in an aluminum-plastic film, dried at 80°C, and then injected with the prepared electrolyte. After vacuum sealing, settling, formation, and shaping, the lithium-ion battery cell is completed.

[0087] Example 2 A type of wound secondary battery cell, such as Figure 2 Includes a positive electrode; a negative electrode; a separator located between the positive and negative electrodes; an electrolyte; and a solid electrolyte coated on the surface of the negative electrode at the corner of the wound structure of the wound secondary battery cell, where it contacts the separator; the coating location is where the trajectory curvature κ ≥ 0.025 mm. -1 At the corner position, the coating width is the same as the width of the negative electrode sheet.

[0088] The solid electrolyte is Li7La3Zr2O 12 The coating thickness is 3 μm. The solid electrolyte coating starts from the uncoated area and gradually increases to the final coating thickness. The initial coating thickness is 0.3 μm.

[0089] The electrolyte contains MMDS, a positive electrode protection additive, which accounts for 0.5% of the total mass of the electrolyte.

[0090] Everything else is the same as in Example 1.

[0091] Example 3 A type of wound secondary battery cell, such as Figure 2 Includes a positive electrode; a negative electrode; a separator located between the positive and negative electrodes; an electrolyte; and a solid electrolyte coated on the surface of the negative electrode at the corner of the wound structure of the wound secondary battery cell, where it contacts the separator; the coating location is where the trajectory curvature κ ≥ 0.025 mm. -1 At the corner position, the coating width is the same as the width of the negative electrode sheet.

[0092] The solid electrolyte is Li 6.75 La3Zr 1.75 Ta 0.25 O 12The coating thickness is 3 μm. The solid electrolyte coating starts from the uncoated area and gradually increases to the final coating thickness. The initial coating thickness is 0.3 μm.

[0093] The electrolyte contains a positive electrode protection additive, LiBOB, which accounts for 0.3% of the total mass of the electrolyte.

[0094] Everything else is the same as in Example 1.

[0095] Example 4 A type of wound secondary battery cell, such as Figure 2 Includes a positive electrode; a negative electrode; a separator located between the positive and negative electrodes; an electrolyte; and a solid electrolyte coated on the surface of the negative electrode at the corner of the wound structure of the wound secondary battery cell, where it contacts the separator; the coating location is where the trajectory curvature κ ≥ 0.025 mm. -1 At the corner position, the coating width is the same as the width of the negative electrode sheet.

[0096] The solid electrolyte is Li 0.33 La 0.56 TiO3, coating thickness 3μm, solid electrolyte coating starts from the uncoated area and increases gradually to the final coating thickness, preferably the initial coating thickness is 0.3μm.

[0097] The electrolyte contains a positive electrode protection additive, LiODFB, which accounts for 0.5% of the total mass of the electrolyte.

[0098] Everything else is the same as in Example 1.

[0099] Example 5 A type of wound secondary battery cell, such as Figure 3 Includes a positive electrode; a negative electrode; a separator located between the positive and negative electrodes; an electrolyte; and a solid electrolyte, which is coated on the surface of the separator at the corner of the wound structure of the wound secondary battery cell that contacts the negative electrode; the coating location is where the trajectory curvature κ ≥ 0.025 mm. -1 At the corner position, the coating width is the same as the width of the negative electrode sheet.

[0100] The solid electrolyte is Li 0.33 La 0.56 TiO3, coating thickness 3μm, solid electrolyte coating starts from the uncoated area and increases gradually to the final coating thickness, the initial coating thickness is 0.3μm.

[0101] The electrolyte contains a positive electrode protection additive PS, which accounts for 0.5% of the total mass of the electrolyte.

[0102] Everything else is the same as in Example 1.

[0103] Example 6 A type of wound secondary battery cell, such as Figure 4 Includes a positive electrode; a negative electrode; a separator located between the positive and negative electrodes; an electrolyte; and a solid electrolyte coated on the surface of the separator at the corner of the wound structure of the wound secondary battery cell, which is in contact with the positive electrode; the coating location is where the trajectory curvature κ ≥ 0.025 mm. -1 At the corner position, the coating width is the same as the width of the positive electrode sheet.

[0104] The solid electrolyte is Li 0.7 Al 0.3 Ti 1.7 (PO4)3, coating thickness 3μm, solid electrolyte coating starts from the uncoated area and increases with the initial coating thickness gradient to the final coating thickness, the initial coating thickness is 0.3μm.

[0105] The electrolyte contains MMDS, a positive electrode protection additive, which accounts for 0.5% of the total mass of the electrolyte.

[0106] Everything else is the same as in Example 1.

[0107] Example 7 A type of wound secondary battery cell is basically the same as that in Example 4, except that the electrolyte contains positive electrode protection additives MMDS+LiODFB, which account for 0.5+0.3% of the total mass of the electrolyte.

[0108] Example 8 A type of wound secondary battery cell is basically the same as that in Example 4, except that the electrolyte contains positive electrode protection additives MMDS+LiODFB+PS, which account for 0.5+0.5+0.5% of the total mass of the electrolyte.

[0109] Example 9 A type of wound secondary battery cell, basically the same as in Example 1, except that: the solid electrolyte is Li. 0.7 Al 0.3 Ti 1.7 (PO4)3, coating thickness 3μm. The difference from Example 1 is that there is no gradient setting at the start and end of the coating, and the overall coating thickness is uniformly 3μm.

[0110] Example 10 A wound secondary battery cell is basically the same as in Example 1, except that the solid electrolyte coating thickness is 0.5 μm. Everything else is the same as in Example 1.

[0111] Example 11 A wound secondary battery cell is basically the same as that in Example 1, except that the content of the positive electrode additive is 0.1%. Everything else is the same as in Example 1.

[0112] Example 12 A wound secondary battery cell is basically the same as that in Example 1, except that the content of the positive electrode additive is 1.0%. Everything else is the same as in Example 1.

[0113] Example 13 A wound secondary battery cell is basically the same as that in Example 1, except that the content of the positive electrode additive is 2.0%. Everything else is the same as in Example 1.

[0114] Example 14 A wound secondary battery cell is basically the same as in Example 1, except that the solid electrolyte coating thickness is 0.1 μm. Everything else is the same as in Example 1.

[0115] Example 15 A type of wound secondary battery cell is basically the same as that in Example 1, except that the solid electrolyte coating thickness is 5μm.

[0116] Everything else is the same as in Example 1.

[0117] Example 16 A type of wound secondary battery cell is basically the same as that in Example 1, except that the solid electrolyte coating thickness is 1μm.

[0118] Everything else is the same as in Example 1.

[0119] Comparative Example 1 A type of wound secondary battery cell differs from Example 1 in that it has no solid electrolyte coating and the electrolyte does not contain positive electrode additives.

[0120] Comparative Example 2 A type of wound secondary battery cell differs from Example 6 in that the electrolyte does not contain positive electrode additives.

[0121] Comparative Example 3 A type of wound secondary battery cell differs from Example 1 in that it has no solid electrolyte coating.

[0122] Result detection Cyclic storage test: At 25℃, the lithium-ion battery was first fully discharged at 1C and then tested. The test procedure was as follows: the lithium-ion battery was charged at a constant current of 3C to a voltage of 4.25V, then charged at a constant voltage of 4.25V to a current of 0.05C. After resting for 5 minutes, the lithium-ion battery was discharged at a constant current of 1C to a voltage of 2.8V. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. The lithium-ion cell was subjected to multiple charge-discharge cycles using the above method until the discharge capacity of the lithium-ion secondary battery decreased to 80%, and the number of cycles of the lithium-ion cell was recorded.

[0123] The test results are shown in Table 1 below: Table 1. No. Solid electrolyte coating location Solid electrolyte type Types of positive electrode additives Positive electrode additive content cycle Example 1 positive electrode <![CDATA[Li 0.7 Al 0.3 Of 1.7 (PO4)3]]> PS 0.5 1756 Example 2 negative electrode <![CDATA[Li7La3Zr2O 12 ]]> MMDS 0.5 1769 Example 3 negative electrode <![CDATA[Li 6.75 La3Zr 1.75 Yes 0.25 Oh 12 ]]> LiBOB 0.3 1778 Example 4 negative electrode <![CDATA[Li 0.34 The 0.56 TiO3]]> LiODFB 0.5 1804 Example 5 The diaphragm is for the negative electrode <![CDATA[Li 0.34 The 0.56 TiO3]]> PS 0.5 1736 Example 6 The diaphragm is opposite to the positive electrode. <![CDATA[Li 1.4 Al 0.4 Of 1.6 (PO4)3]]> MMDS 0.5 1732 Example 7 negative electrode <![CDATA[Li 0.34 The 0.56 TiO3]]> MMDS+LiODFB 0.5+0.3 1852 Example 8 negative electrode <![CDATA[Li 0.34 The 0.56 TiO3]]> MMDS+LiODFB+PS 0.5+0.5+0.5 1900 Example 9 positive electrode <![CDATA[Li 0.7 Al 0.3 Of 1.7 (PO4)3]]> PS 0.5 1645 Example 10 positive electrode <![CDATA[Li 0.7 Al 0.3 Of 1.7 (PO4)3]]> PS 0.5 1639 Example 11 positive electrode <![CDATA[Li 0.7 Al 0.3 Of 1.7 (PO4)3]]> PS 0.1 1636 Example 12 positive electrode <![CDATA[Li 0.7 Al 0.3 Of 1.7 (PO4)3]]> PS 1.0 1778 Example 13 positive electrode <![CDATA[Li 0.7 Al 0.3 Of 1.7 (PO4)3]]> PS 2.0 1765 Example 14 positive electrode <![CDATA[Li 0.7 Al 0.3 Of 1.7 (PO4)3]]> PS 0.5 1643 Example 15 positive electrode <![CDATA[Li 0.7 Al 0.3 Of 1.7 (PO4)3]]> PS 0.5 1602 Example 16 positive electrode <![CDATA[Li 0.7 Al 0.3 Of 1.7 (PO4)3]]> PS 0.5 1753 Comparative Example 1 / / / / 1321 Comparative Example 2 The diaphragm is opposite to the positive electrode. <![CDATA[Li 1.4 Al 0.4 Of 1.6 (PO4)3]]> / / 1525 Comparative Example 3 / / PS 0.5 1417 As can be seen from the data in Table 1 above, the wound secondary battery cell provided by this invention has excellent cycle performance, with a maximum of 1900 cycles before the discharge capacity decays to 80%. In contrast, the wound secondary battery cell provided in Comparative Example 1, without any related improvements, only has 1321 cycles before the discharge capacity decays to 80%.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A wound secondary battery cell, comprising a positive electrode, a negative electrode, a separator located between the positive electrode and the negative electrode, an electrolyte, and a solid electrolyte, characterized in that, The solid electrolyte is coated between the positive and negative electrodes at the corner of the winding structure of the wound secondary cell; The electrolyte contains a positive electrode protection additive, which includes sulfur-containing substances and borates, and the amount added is 0.1~2wt%.

2. The wound secondary battery cell according to claim 1, characterized in that, The sulfur-containing substance is selected from any one or more of 1,3-propanesulfonyl lactone or methane disulfonate methylene ester; and / or, the borate is selected from one or more of lithium difluorooxalate borate or lithium dioxalate borate.

3. The wound secondary battery cell according to claim 2, characterized in that, The positive electrode protection additive is a mixture of methylene methane disulfonate and lithium difluorooxalate borate, or the positive electrode protection additive is a mixture of methylene methane disulfonate, lithium difluorooxalate borate, and 1,3-propane sulcolone. The preferred mixing mass ratio of methylene methane disulfonate and lithium difluorooxalate borate is (0.2~0.8):(0.2~0.8), more preferably 0.5:0.3; The preferred mixing ratio of methylene disulfonate, lithium difluorooxalate borate, and 1,3-propanesulfonyl lactone is (0.2~0.8):(0.2~0.8):(0.2~0.8), and more preferably 0.5:0.5:0.

3.

4. The wound secondary battery cell according to any one of claims 1 to 3, characterized in that, The solid electrolyte is coated at a location with a trajectory curvature κ ≥ 0.025 mm. -1 The corner location.

5. The wound secondary battery cell according to claim 4, characterized in that, The thickness of the solid electrolyte coating is 0.1~5μm, preferably 1~3μm.

6. The wound secondary battery cell according to claim 5, characterized in that, The coating thickness of the solid electrolyte starts from the beginning and end of the uncoated area and increases gradually to the final coating thickness, preferably with the initial coating thickness being 10% or more of the final coating thickness.

7. The wound secondary battery cell according to any one of claims 1 to 6, characterized in that, The solid electrolyte is coated on any one or more of the surfaces of the negative electrode, the positive electrode, or the separator that are in contact with the positive and negative electrodes, preferably on the negative electrode.

8. The wound secondary battery cell according to any one of claims 1 to 6, characterized in that, The solid electrolyte satisfies at least one of the following conditions: The sodium-ion superconductor structure solid electrolyte is lithium aluminum titanium phosphate (Li). 1-x Al x Ti 2-x (PO4)3, 0 < x ≤ 0.5, preferably Li 0.7 Al 0.3 Ti 1.7 (PO4)3 or Li 1.4 Al 0.4 Ti 1.6 (PO4)3; Garnet-structured solid electrolytes are lanthanum zirconium oxide (LLZO) or tantalum-doped lithium lanthanum zirconium oxide (Li). 7-x La3Zr 2-x Ta x O 12 0 < x ≤ 0.4, preferably Li 6.75 La3Zr 1.75 Ta 0.2 5O 12 ; The perovskite-structured solid electrolyte is lithium lanthanum titanium oxide (Li). 3x La 2 / 3-x TiO3), 0.04≤x≤0.17, preferably Li 0.34 La 0.56 TiO3.

9. The wound secondary battery cell according to any one of claims 1 to 8, characterized in that, The electrolyte further comprises any one or more of vinyl sulfate, vinylene carbonate, and fluorovinylene carbonate, preferably in a content of 0.5-10 wt%. And / or, the separator is a polyethylene film, the polyethylene film is coated with PVDF coating on both sides, and a boehm ceramic layer is coated on the surface in contact with the positive electrode.

10. A method for preparing a wound secondary battery cell according to any one of claims 1 to 9, characterized in that, Includes the following steps: A solid electrolyte is coated in a predetermined area of ​​the positive electrode, negative electrode, or separator, wherein the predetermined area corresponds to a winding trajectory curvature κ ≥ 0.025 mm. -1 The corner location; The positive electrode, separator, and negative electrode are wound together, with the separator positioned between the positive and negative electrodes, to produce a semi-finished wound battery cell. The wound battery cell semi-finished product is packed into a packaging shell, dried, and then injected with electrolyte. The wound secondary battery cell is obtained through vacuum sealing, settling, formation, and shaping.

11. A battery cell module, characterized in that, Includes the wound secondary battery cell as described in any one of claims 1 to 9.

12. A battery pack, characterized in that, Includes the wound secondary battery cell as described in any one of claims 1 to 9 or the battery cell module as described in claim 11.

13. An electrical appliance, characterized in that, It includes the wound secondary battery cell according to any one of claims 1 to 9, the battery cell module according to claim 11, or the battery pack according to claim 12.

14. A vehicle, characterized in that, It includes the wound secondary battery cell according to any one of claims 1 to 9, the battery cell module according to claim 11, or the battery pack according to claim 12.

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