Secondary battery

Abstract

A secondary battery includes an electrode group, a tape, an electrolyte, and a bottomed cylindrical outer can that houses the electrode group, the tape, and the electrolyte. The electrode group is wound by a positive electrode, a negative electrode, and a separator. The negative electrode includes a negative electrode current collector. The separator is interposed between the positive electrode and the negative electrode. The tape fixes an end portion of the electrode group. The negative electrode has an outermost peripheral portion disposed at an outermost periphery of the electrode group. The tape includes a metal base material layer and is attached to the negative electrode current collector of the outermost peripheral portion. The negative electrode current collector of the outermost peripheral portion to which the tape is attached contacts the outer can. A static friction coefficient of the metal base material layer with respect to a material of the outer can is 0.8 or less.

Description

Technical Field

[0001] This disclosure relates to a secondary battery having a wound electrode assembly. Background Technology

[0002] The secondary battery comprises an electrode assembly, an electrolyte, and an outer container for housing the electrode assembly and electrolyte. The electrode assembly consists of a positive electrode, a negative electrode, and a separator between the positive and negative electrodes, wound together. Adhesive tape (winding fixing tape) is attached to the circumference of the wound electrode assembly to fix the winding end.

[0003] Patent Document 1 discloses "a non-aqueous electrolyte secondary battery comprising an electrode assembly, a tape for fixing at least the winding end of the electrode assembly, and a non-aqueous electrolyte. The electrode assembly is formed by winding a positive electrode, a negative electrode, and a separator between the positive and negative electrodes. At least in the charged state, the negative electrode contains lithium metal and / or a lithium alloy, and the tape has a tensile strength of 20 N / 10 mm or less when the elongation is 200% or more." Furthermore, Patent Document 1 describes that the substrate of the tape is formed from a polymer such as resin.

[0004] Prior art literature

[0005] Patent Document 1: International Publication No. 2019 / 003641 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] To reduce internal resistance, it is considered to construct the electrode assembly such that the negative current collector is exposed on the outer peripheral surface of the electrode assembly that contacts the inner surface of the outer can. However, when resin tape is used to wrap and fix the tape, the internal resistance is sometimes not sufficiently reduced because the high-resistance resin tape is located between the electrode assembly and the outer can.

[0008] Furthermore, the secondary battery includes a mechanism that, in the event of an internal short circuit, the increased internal pressure causes the seal at the opening of the outer can to detach, allowing the electrode assembly to exit through the can opening. This mechanism suppresses the rise in battery temperature during an internal short circuit. If resin tape is attached to the outer periphery of the electrode assembly, the dissolution of the resin tape during an internal short circuit will delay the exit of the electrode assembly, causing the battery temperature to rise.

[0009] Methods for solving problems

[0010] One aspect of this disclosure relates to a secondary battery comprising an electrode assembly, an adhesive tape, an electrolyte, and a bottomed cylindrical outer casing for housing the electrode assembly, the adhesive tape, and the electrolyte. The electrode assembly is formed by winding a positive electrode, a negative electrode, and a separator. The negative electrode has a negative current collector. The separator is located between the positive electrode and the negative electrode. The adhesive tape secures the winding end of the electrode assembly. The negative electrode has an outermost peripheral portion disposed on the outermost periphery of the electrode assembly. The adhesive tape has a metal substrate layer and is attached to the negative current collector on the outermost peripheral portion. The negative current collector on the outermost peripheral portion with the adhesive tape attached is in contact with the outer casing. The static friction coefficient of the metal substrate layer relative to the material of the outer casing is 0.8 or less.

[0011] The effects of the invention

[0012] According to this disclosure, in a secondary battery, the internal resistance can be reduced and the temperature rise during an internal short circuit can be suppressed.

[0013] The novel features of the invention are described in the appended claims. The invention, in both its structure and content, can be combined with other objects and features of the invention, and will be better understood by referring to the following detailed description of the accompanying drawings. Attached Figure Description

[0014] Figure 1 This is a schematic diagram illustrating the structure of a friction coefficient test.

[0015] Figure 2 This is a cross-sectional view schematically illustrating an example of a secondary battery according to an embodiment of the present disclosure.

[0016] Figure 3 This is a schematic front view of an example of a wound electrode assembly viewed from the side of the winding end.

[0017] Figure 4 This is a schematic front view of an example of a wound electrode assembly viewed from the side opposite to the end of the winding.

[0018] Figure 5 This is a schematic top view of one end face of an example of a wound electrode assembly viewed from the direction of the winding axis. Detailed Implementation

[0019] The following description illustrates embodiments of this disclosure by way of example, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​or materials are sometimes illustrated, but other numerical values ​​or materials can be applied as long as the effects of this disclosure are achieved. In this specification, references such as "numerical value A to numerical value B" include both numerical value A and numerical value B, and can be replaced with "numerical value A or higher and numerical value B or lower." In the following description, when lower and upper limits of numerical values ​​related to specific physical properties or conditions are illustrated, any combination of any illustrated lower limit and any illustrated upper limit can be used, provided the lower limit is not greater than the upper limit.

[0020] The secondary battery disclosed herein includes an electrode assembly, adhesive tape, an electrolyte, and a bottomed cylindrical outer casing. The electrode assembly is formed by winding a positive electrode, a negative electrode, and a separator. The negative electrode includes a negative current collector. The separator is located between the positive and negative electrodes. The adhesive tape secures the winding end of the electrode assembly. The outer casing houses the electrode assembly, adhesive tape, and electrolyte. The negative electrode has an outermost peripheral portion disposed on the outermost periphery of the electrode assembly. The adhesive tape has a metal substrate layer and is attached to the outermost peripheral negative current collector. Hereinafter, the adhesive tape having the metal substrate layer will also be referred to as "metal adhesive tape." The outermost peripheral negative current collector to which the adhesive tape is attached is in contact with the outer casing, and the static friction coefficient of the metal substrate layer relative to the material of the outer casing is 0.8 or less.

[0021] The outer can contacts the outermost negative current collector, which is covered with adhesive tape. Specifically, the inner surface of the outer can has a first region that contacts the negative current collector and a second region that contacts the metal tape (metal substrate layer). In the second region, a low-resistance metal tape (metal substrate layer) is sandwiched between the electrode assembly (the outermost negative current collector) and the outer can. The formation of the first and second regions significantly reduces the internal resistance of the secondary battery, suppressing the increase in internal resistance even when resin tape exists between the electrode assembly and the outer can.

[0022] The secondary battery features a mechanism that, in the event of an internal short circuit, the increased internal pressure causes the seal at the opening of the outer can to detach, allowing the electrode assembly to exit through the opening. The metal tape exhibits superior heat resistance compared to resin tape with a resin-based layer. Therefore, it can suppress delays in electrode assembly exit caused by the dissolution of the resin tape during an internal short circuit, as well as the associated increase in battery temperature.

[0023] The static friction coefficient between the metal substrate layer and the outer can material is 0.8 or less. In this case, when the electrode assembly discharge mechanism is working, the friction between the metal substrate layer and the outer can is reduced, the electrode assembly is discharged smoothly, and the battery temperature rise caused by the delay in electrode assembly discharge is suppressed.

[0024] From the viewpoint of suppressing the discharge delay of the electrode assembly, the static friction coefficient of the metal substrate layer relative to the material of the outer can is preferably 0.6 or less.

[0025] From the viewpoint of the discharge of the electrode assembly, the static friction coefficient of the outermost negative electrode current collector relative to the material of the outer can is preferably 0.8 or less, more preferably 0.6 or less.

[0026] There can be one or more metal tapes (e.g., two). When using multiple metal tapes, none of the tapes should have a static friction coefficient greater than 0.8 between the metal substrate layer and the outer can material. That is, in any one of the multiple metal tapes, the static friction coefficient between the metal substrate layer and the outer can material must be less than 0.8. If at least one of the multiple metal tapes has a metal substrate layer with a static friction coefficient exceeding 0.8, the increased friction between the metal substrate layer and the outer can will cause a delay in the discharge of the electrode assembly.

[0027] Examples of materials for outer cans include iron (Fe), aluminum (Al), copper (Cu), nickel (Ni), and alloys containing these metals. Examples of iron-containing alloys include stainless steel (SUS). SUS is preferred as the material for the outer can. The outer can may have a coating (e.g., a Ni coating) on ​​its surface. Furthermore, when the outer can has a coating, the material of the outer can in the static friction coefficient refers to the material of the coating.

[0028] The static friction coefficient of the metal substrate layer relative to the outer can material can be calculated as follows.

[0029] Friction coefficient tests were conducted based on JIS K 7125. Specifically, as follows... Figure 1 As shown, a first specimen 51 is fixed on a horizontal specimen stage 50, and a second specimen 52 is placed on top of the first specimen 51. A weight 53 is then placed on top of the second specimen 52 as needed. This brings the first specimen 51 and the second specimen 52 into contact with each other and allows them to remain horizontally stationary. The total mass of the second specimen 52 and the weight 53 is 500g. The test is conducted without the weight 53, provided that the second specimen 52 has a mass of 500g.

[0030] Either specimen 51 or specimen 52 is made of the same material as the metal substrate layer of the wrapping and fixing tape. The other specimen is made of the same material as the outer can (or, if the surface has a coating, the coating). Each specimen can be prepared by sampling a portion of the substrate used in the metal substrate layer and a portion of the sheet material used in the can manufacturing process of the outer can. The contact area between specimen 51 and specimen 52 is 1200 mm². 2The first specimen 51 is plate-shaped. The second specimen 52 is, for example, plate-shaped, but may also be cuboid in shape. The thickness of the first specimen 51 and the second specimen 52 is, for example, 0.05~0.5 mm. The dimensions of the plate-shaped second specimen 52 are, for example, 30 mm × 40 mm. When viewed from the normal direction of the principal surface of the first specimen 51, the area of ​​the second specimen 52 is smaller than that of the first specimen 51. The surface roughness (e.g., arithmetic mean roughness Ra) of each specimen is, for example, within the range of surface roughness of each component of the outer can or metal substrate layer used in the battery. The arithmetic mean roughness Ra of the contact surface of the first specimen 51 and the second specimen 52 is, for example, 10 μm or less (or 5 μm or less). In addition, the arithmetic mean roughness Ra is an index representing surface roughness based on JIS B 0601.

[0031] A rope 54 is attached to the second specimen 52 and allowed to slide. The load F (maximum static friction force) generated at this time is measured using a force sensor. The test speed at this time (when the second specimen 52 is moved towards...) is... Figure 1 The stretching speed (in the direction of the arrow shown) is 1 mm / min. Based on the measured load F, the static friction coefficient is calculated as (load F / vertical resistance). Additionally, the vertical resistance is 4.9 N. The vertical resistance is calculated by multiplying the total mass (0.5 kg) of the second sample 52 and the weight 53 by 9.8 (m / s²). 2 The static friction coefficient is calculated by repeating the test five times. This yields the average static friction coefficient for specimen 51 and specimen 52.

[0032] The static friction coefficient of the outermost negative electrode current collector relative to the material of the outer can can be determined by using a sample made of the same material as the negative electrode current collector in either the first or second sample in the friction coefficient test described above.

[0033] The outer container can be a bottomed cylindrical shape or a bottomed square shape. The wound electrode assembly can be cylindrical or flat. A cylindrical electrode assembly can be stored in a bottomed cylindrical outer container, and a flat electrode assembly can be stored in a bottomed square outer container.

[0034] The negative electrode may have a negative electrode binder layer supported on the negative electrode current collector. In this case, at least a portion of the outermost peripheral region of the negative electrode opposite to the outer can is not supported by the negative electrode binder layer (exposing the negative electrode current collector). The negative electrode binder layer only needs to be formed on the surface of the negative electrode current collector opposite to the positive electrode (positive electrode binder layer). Preferably, at least 70% or 80% of the area of ​​the outermost peripheral region opposite to the outer can is not supported by the negative electrode binder layer. More preferably, the entire area of ​​the outermost peripheral region opposite to the outer can is not supported by the negative electrode binder layer. Preferably, at least 70% or 80% of the area of ​​the outermost peripheral region where the adhesive tape is attached is not supported by the negative electrode binder layer. More preferably, the entire area of ​​the outermost peripheral region where the adhesive tape is attached is not supported by the negative electrode binder layer.

[0035] Examples of secondary batteries include non-aqueous electrolyte secondary batteries such as lithium-ion batteries and lithium metal batteries. The negative electrode of a lithium-ion battery includes a negative electrode flux layer supported on the negative electrode current collector. This flux layer contains a negative electrode active material that absorbs lithium ions during charging and releases lithium ions during discharging. The negative electrode of a lithium metal battery is one where lithium metal is deposited during charging and dissolves in the electrolyte during discharging. It can consist solely of a negative electrode current collector, or lithium metal can be deposited on the surface of the current collector during charging. A thin negative electrode flux layer can be supported on the surface of the negative electrode current collector in a lithium metal secondary battery.

[0036] (Wrap and fix the tape)

[0037] The metal substrate layer is composed, for example, of a foil or sheet-like substrate. The metal substrate layer may contain one metal or two or more metals. It may also be an alloy layer containing two or more metals. Preferably, the metal substrate layer contains at least one metal selected from nickel (Ni), iron (Fe), copper (Cu), titanium (Ti), zinc (Zn), silver (Ag), gold (Au), and stainless steel (SUS). In this case, it is easy to improve the conductivity and heat resistance of the metal tape, and it is easy to control the static friction coefficient relative to the outer can material to below 0.8.

[0038] From the viewpoint of fixing the electrode assembly, the tape preferably includes an adhesive layer. This adhesive layer is preferably disposed on one surface of the metal substrate layer (the outermost peripheral surface). In this case, the outermost negative current collector is in close contact with the metal substrate layer through the adhesive layer. The adhesive layer is formed of an adhesive. Examples of adhesives include acrylic adhesives, silicone adhesives, and rubber adhesives. Among these, acrylic adhesives are preferred from the viewpoint of heat resistance, etc.

[0039] The ratio of the thickness of the adhesive layer to the thickness of the metal substrate layer is, for example, 5 to 25%. From the viewpoint of reducing internal resistance, the thickness of the adhesive layer is, for example, 75 μm or less. Even in cases of low conductivity, the adhesive layer contained in the tape can be compressed between the inner surface of the outer can and the electrode assembly within the battery, so that the effect of the adhesive layer on the conductivity of the tape can be thinned to a negligible degree.

[0040] The adhesive layer can be conductive and can be formed from a conductive adhesive (e.g., an adhesive containing conductive particles). Examples of conductive particles include metal particles, composite particles containing resin particles, and metal coatings covering the surface of the resin particles. Examples of metals contained in the metal particles and metal coatings include Ni, Cu, Ag, Fe, etc. The metal particles and metal coatings can contain one type of metal or two or more types. Examples of resins contained in the resin particles include acrylic resins, polystyrene, etc.

[0041] From the viewpoint of easily reducing internal resistance and ensuring energy density (battery capacity), the thickness of the tape is preferably 250 μm or less, more preferably 200 μm or less. From the viewpoint of suppressing tape breakage, the thickness of the tape is, for example, 50 μm or more. The thickness of the tape is the combined thickness of the metal substrate layer and the adhesive layer.

[0042] When securing the winding end with multiple tapes, multiple tapes (e.g.) are preferred. Figure 3 The tapes 41 and 42 have thicknesses within the aforementioned preferred range. Furthermore, the thicknesses of the multiple tapes can differ from one another without impairing the reduction in internal resistance caused by the tapes. From the viewpoint of reducing internal resistance and ensuring uniformity of surface pressure on the electrode assembly, it is preferable that the thicknesses of the multiple tapes are approximately the same.

[0043] The width of the tape is preferably 4 mm or more and 12 mm or less. In this case, the tape can be used to stably fix the winding end and to easily ensure sufficient contact area between the outer can and the outermost periphery.

[0044] When securing the winding end with multiple tapes, multiple tapes (e.g.) are preferred. Figure 3 The tapes 41 and 42 each have widths within the aforementioned preferred range. Furthermore, the widths of the multiple tapes can differ from one another without impairing the reduction in internal resistance caused by the tapes. From the viewpoint of reducing internal resistance and ensuring uniformity of surface pressure on the electrode assembly, it is preferable that the widths of the multiple tapes are approximately the same.

[0045] The tape is preferably wound around the electrode assembly with its two ends not overlapping. When securing the winding ends with multiple tapes, it is preferable that each tape is wound around the electrode assembly with its two ends not overlapping. The length of the tape (the dimension along the length of the tape) is preferably 1 mm to 7 mm shorter than the outer circumference of the electrode assembly. For example, the tape is preferably wound around the outer circumference of the electrode assembly at least 0.8 turns and less than 0.99 turns. In this case, the effect of securing the electrode assembly is improved, and it is easier to mitigate the stress associated with the expansion and contraction of the electrode assembly, and to easily suppress damage to the positive and negative electrodes (especially breakage of the negative electrode current collector) associated with the expansion and contraction of the electrode assembly.

[0046] The tapes comprise a first tape and a second tape, which are respectively attached to one end side and the other end side of the electrode assembly along the winding axis direction, on the outermost negative current collector. The first tape and the second tape preferably each have a metal substrate layer with a static friction coefficient of 0.8 or less relative to the material of the outer can. Thus, at the central portion along the winding axis direction of the electrode assembly, the outermost negative current collector contacts the outer can. The first tape and the second tape facilitate the reduction of internal resistance, enabling more stable fixation of the winding end of the electrode assembly.

[0047] The following describes examples of the components of a non-aqueous electrolyte secondary battery. However, secondary batteries are not limited to the examples described below.

[0048] (negative electrode)

[0049] The negative electrode, for example, comprises a negative current collector and a negative electrode additive layer supported on the surface of the negative current collector. The negative electrode additive layer, for example, includes a negative electrode active material, a binder, and a thickening agent. The negative electrode, for example, can be obtained by coating both sides of the negative current collector with a negative electrode slurry, drying the coating, and then calendering to form the negative electrode additive layer. The negative electrode slurry includes a negative electrode additive and a dispersion medium (e.g., water). The negative electrode additive layer may be formed on only one side of the negative current collector or on both sides. In this case, the negative electrode slurry may not be coated on a designated area (the surface area opposite the outer can) of the negative current collector, thus exposing the negative current collector. Alternatively, the negative current collector may be exposed in the designated area by removing the negative electrode additive layer, etc. In the case of a lithium metal secondary battery, the negative electrode may consist solely of the negative current collector, or lithium foil may be pressed onto the negative current collector.

[0050] The negative electrode mixture contains at least a negative electrode active substance, and may contain other components as needed. Examples of other components include binders, tackifiers, and conductive materials.

[0051] The negative electrode active material can be a material that reversibly absorbs and releases lithium ions. Examples of negative electrode active materials include carbonaceous materials, Si-containing materials, and Sn-containing materials. The negative electrode can contain one type of negative electrode active material or a combination of two or more types. Examples of carbonaceous materials include graphite, easily graphitized carbon (soft carbon), and difficult-to-graphitize carbon (hard carbon).

[0052] Examples of anode active materials include carbonaceous materials, Si-containing materials, and Sn-containing materials. An anode may contain one type of anode active material or a combination of two or more. Examples of carbonaceous materials include graphite, easily graphitized carbon (soft carbon), and difficult-to-graphitize carbon (hard carbon).

[0053] Conductive materials include, for example, carbon materials. Examples of carbon materials include carbon black, acetylene black, Ketjen black, carbon nanotubes, and graphite.

[0054] Examples of adhesive materials include fluoropolymers, polyacrylonitrile, polyimide resins, acrylic resins, polyolefin resins, and rubber-like polymers. Examples of fluoropolymers include polytetrafluoroethylene and polyvinylidene fluoride. Examples of tackifying materials include carboxymethyl cellulose (CMC) and sodium salts of CMC.

[0055] The negative current collector can be any conductive sheet. Foil, film, etc., can be used as the conductive sheet.

[0056] Materials used for the negative electrode current collector (conductive sheet) include, for example, copper (Cu), nickel (Ni), iron (Fe), and alloys containing these metallic elements. Examples of alloys include copper alloys and stainless steel (SUS). Among these, copper and / or copper alloys, which have high conductivity, are preferred.

[0057] There are no particular restrictions on the thickness of the negative current collector, for example, it can be 5μm or more and 300μm or less.

[0058] (positive electrode)

[0059] The positive electrode, for example, comprises a positive current collector and a positive electrode additive layer supported on the surface of the positive current collector. The positive electrode additive layer, for example, includes a positive electrode active material, a conductive material, and a binder material. The positive electrode, for example, can be obtained by coating both sides of the positive current collector with a positive electrode slurry containing a positive electrode active material, a conductive material, and a binder material, drying the coating, and then calendering to form the positive electrode additive layer. The positive electrode slurry contains a positive electrode additive and a dispersion medium (e.g., N-methyl-2-pyrrolidone). The positive electrode additive layer may be formed on only one side of the positive current collector or on both sides.

[0060] A positive electrode mixture contains at least a positive electrode active substance, and may contain other ingredients as needed. Examples of other ingredients include binders, conductive materials, etc.

[0061] The positive electrode active material is a material that absorbs and releases lithium ions. Examples of positive electrode active materials include lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanions, and transition metal sulfides. Among these, lithium-containing transition metal oxides are preferred from the viewpoint of low manufacturing cost and high average discharge voltage.

[0062] Examples of transition metal elements contained in lithium-containing transition metal oxides include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, and W. Lithium-containing transition metal oxides may contain one or more transition metal elements. These transition metal elements can be Ni, Co, and / or Mn. Lithium-containing transition metal oxides may contain more than one typical element as needed. Examples of typical elements include Mg, Al, Ca, Zn, Ga, Ge, Sn, Sb, Pb, and Bi. Al is a typical example.

[0063] In lithium-containing transition metal oxides, composite oxides containing Ni, Co, and / or Mn as transition metal elements, and sometimes Al as an arbitrary component, with a layered structure and a rock-salt-type crystal structure are preferred for obtaining high capacity.

[0064] As a bonding material, conductive material, etc., the material exemplified in the negative electrode can be used, for example. The shape and thickness of the positive electrode current collector can be selected from the shape and range of the positive electrode current collector.

[0065] Materials used as positive current collectors (conductive sheets) include, for example, aluminum (Al), titanium (Ti), iron (Fe), and alloys containing these metallic elements. As alloys, they can be Al alloys, Ti alloys, Fe alloys, etc. Fe alloys can be stainless steel (SUS).

[0066] There are no particular restrictions on the thickness of the positive current collector, for example, it can be above 5μm and below 300μm.

[0067] (Diaphragm)

[0068] The diaphragm uses a porous sheet material with ion permeability and insulation. Examples of porous sheets include microporous films, woven fabrics, and nonwoven fabrics. The material of the diaphragm is not particularly limited, and polymer materials can be used. Examples of polymer materials include olefin resins, polyamide resins, and cellulose. Examples of olefin resins include polyethylene, polypropylene, and copolymers of ethylene and propylene. The diaphragm may contain additives (inorganic fillers, etc.) as needed. The thickness of the diaphragm is not particularly limited, for example, it can be 5 μm or more and 100 μm or less.

[0069] (electrolytes)

[0070] The electrolyte can be a non-aqueous electrolyte with lithium-ion conductivity. There are no particular limitations on the non-aqueous electrolyte; any known non-aqueous electrolyte used in secondary batteries can be used. The non-aqueous electrolyte may contain, for example, a non-aqueous solvent, lithium ions, and anions dissolved in the non-aqueous solvent. The non-aqueous electrolyte can be liquid or gel-like.

[0071] Liquid non-aqueous electrolytes are prepared by dissolving lithium salts in a non-aqueous solvent. Dissolving the lithium salt in the non-aqueous solvent generates lithium ions and anions.

[0072] Examples of non-aqueous solvents include esters, ethers, nitriles, amides, and their halogenated derivatives. Non-aqueous electrolytes may contain only one of these non-aqueous solvents or two or more. Examples of halogenated derivatives include fluorides. LiPF6 and other lithium salts can be used as lithium salts. The concentration of lithium salts in non-aqueous electrolytes can be above 0.5 mol / L and below 3.5 mol / L.

[0073] (outer body)

[0074] The electrode assembly and non-aqueous electrolyte are housed within the outer casing (battery housing). The outer casing is not particularly limited and can use any known type. The outer casing typically includes an outer can and a sealing body that seals the opening of the outer can. The outer can is formed, for example, by using a sheet material such as SUS plate and performing a prescribed can-making process. The surface of the SUS plate may be nickel-plated. The outer can functions as the negative terminal. The sealing body (sealing plate) functions as the positive terminal. The sealing body may include a sealing plate and a gasket. To electrically insulate the sealing plate from the outer can, a gasket is placed between the sealing plate and the open end of the outer can.

[0075] (Positive lead, negative lead)

[0076] The positive electrode and the sealing body are electrically connected via a positive electrode lead. Materials for the positive electrode lead include, for example, aluminum or an aluminum alloy. The negative electrode is electrically connected to the outer can by contacting the outer casing through the outermost current collector, which is covered with adhesive tape. The negative electrode and the outer can can also be electrically connected via a negative electrode lead. Materials for the negative electrode lead include, for example, nickel or a nickel alloy.

[0077] Here, Figure 2 This is a cross-sectional view schematically illustrating an example of a secondary battery according to an embodiment of the present disclosure. Additionally, a winding and fixing tape 40 is wound around the circumferential surface of the electrode assembly 14, but... Figure 2 The 40mm roll of fixing tape is omitted from the text. Figures 3-5 This is a front view showing an example of a wound electrode assembly where the winding end is fixed with tape. Figure 3 and Figure 4This is a diagram showing the electrode assembly from the side. Figure 3 From Figure 5 The image viewed from the X1 direction. Figure 4 From Figure 5 The image is viewed from the X2 direction. Figure 5 This is a diagram showing the electrode assembly viewed from the direction of the winding axis. Figure 3 and Figure 4 The diagram is an observation in the Y direction. The secondary batteries involved in this disclosure are not limited thereto.

[0078] The cylindrical secondary battery 10 includes a bottomed cylindrical outer casing (battery housing) 30, a wound electrode assembly 14 housed within the outer casing 30, and an electrolyte (not shown). The outer casing 30 includes an outer can 38 and a sealing body (sealing plate 31 and gasket 37) that seals the opening of the outer can 38. The outer can 38 is a bottomed cylindrical shell made of metal (e.g., SUS). A gasket 37 is disposed between the outer can 38 and the sealing plate 31. Inside the outer can 38, insulating plates 17 and 18 are respectively disposed at both ends of the electrode assembly 14.

[0079] The sealing plate 31 includes a filter 32, a lower valve body 33, an insulating component 34, an upper valve body 35, and a cover 36. All components except the insulating component 34 are electrically connected to each other.

[0080] The cylindrical electrode assembly 14 is formed by winding the positive electrode 11, the negative electrode 12, and the separator 13 such that a separator 13 is disposed between the positive electrode 11 and the negative electrode 12. The positive electrode 11, the negative electrode 12, and the separator 13 are each strip-shaped. The positive electrode 11 includes a positive current collector and a positive electrode flux layer formed on both sides of the positive current collector. The negative electrode 12 includes a negative current collector and a negative electrode flux layer formed on both sides of the negative current collector. However, the negative electrode flux layer is not supported on the entire surface area of ​​the negative electrode 12 opposite to the outer can 38 (the surface of the negative current collector on the side opposite to the outer can), and the negative current collector is exposed.

[0081] One end of the positive lead 19 is connected to the positive electrode 11, and the other end of the positive lead 19 is connected to the sealing plate 31 (filter 32). That is, the positive electrode 11 is electrically connected to the cover 36, which also serves as the positive terminal. One end of the negative lead 20 is connected to the negative electrode 12, and the other end of the negative lead 20 is connected to the outer container 38, which also serves as the negative terminal.

[0082] The bottomed cylindrical outer can 38 houses the electrode assembly 14, with the winding end 14e secured by tape 40, and an electrolyte (not shown). The secondary battery 10 has a mechanism that, in the event of an internal short circuit, causes the sealing body (sealing plate 31) installed at the opening of the outer can 38 to detach, allowing the electrode assembly 14, with the winding end 14e secured by tape 40, to be discharged from the opening of the outer can 38.

[0083] The negative electrode 12 has an outermost peripheral portion 12a disposed on the outermost periphery 14s of the electrode assembly 14. In the entire surface region of the outermost peripheral portion 12a opposite to the outer can 38, the negative electrode additive layer is not supported, but the negative electrode current collector is exposed.

[0084] The tape 40 includes a first tape 41 and a second tape 42 that are respectively attached to the negative current collector of the outermost peripheral portion 12a on one end 141 side and the other end 142 side in the winding axis direction of the electrode assembly 14.

[0085] The negative current collector of the outermost peripheral portion 12a, to which adhesive tape 40 (first tape 41, second tape 42) is attached, contacts the outer can 38. At one end 141 in the winding axis direction of the electrode assembly 14, the negative current collector of the outermost peripheral portion 12a has a region that contacts the outer can 38 through the first tape 41. At one end 142 in the winding axis direction of the electrode assembly 14, the negative current collector of the outermost peripheral portion 12a has a region that contacts the outer can 38 through the second tape 42. In the central portion 143 in the winding axis direction of the electrode assembly 14, the negative current collector of the outermost peripheral portion 12a is in direct contact with the outer can 38. This allows for more stable fixation of the winding end 14e of the electrode assembly 14 and facilitates a reduction in internal resistance.

[0086] The first adhesive tape 41 has a first substrate layer. The second adhesive tape 42 has a second substrate layer. Both the first and second substrate layers are metal substrate layers with a static friction coefficient of 0.8 or less relative to the material of the outer can 38. The static friction coefficients of the first and second substrate layers may be approximately the same or different. The types of metals contained in the substrate layers of the first and second substrate layers may be the same or different.

[0087] The first adhesive tape 41 has a first adhesive layer disposed on one surface (the outermost peripheral surface) of the first substrate layer. The second adhesive tape 42 has a second adhesive layer disposed on one surface (the outermost peripheral surface) of the second substrate layer. The first adhesive layer and the second adhesive layer may each be a conductive adhesive layer. The materials forming the first adhesive layer and the second adhesive layer may be the same or different.

[0088] Adhesive tapes 41 and 42 are wound around electrode assembly 41 with their ends not overlapping. That is, in the winding direction of adhesive tapes 41 and 42, portions 41a and 42a of unwound adhesive tapes 41 and 42 are present on the outer circumferential surface of electrode assembly 14. The length of adhesive tapes 41 and 42 (the dimension of the adhesive tapes 41 and 42 in the longitudinal direction) is preferably 1 mm or more and 7 mm or less shorter than the outer circumferential length of electrode assembly 14. For example, adhesive tapes 41 and 42 are preferably wound around the outer circumference of electrode assembly 14 for at least 0.8 turns and at least 0.99 turns.

[0089] Figure 3 The distance L1 between the tape 41 and one end 141 of the electrode assembly 14 in the winding axis direction, and the distance L2 between the tape 42 and the other end 142 of the electrode assembly 14 in the winding axis direction, can each be, for example, 2 to 5 mm. L1 and L2 can be different, but from the viewpoint of easily and stably fixing the electrode assembly, it is preferable that L1 and L2 are approximately the same.

[0090] Figure 3 The distance L3 between the tapes 41 and 42 shown is preferably 18 to 46 mm. In this case, the area of ​​the negative current collector of the outermost peripheral portion 12a in direct contact with the outer can 38 can be easily and sufficiently ensured at the central portion 143 in the winding axis direction of the electrode assembly 14.

[0091] In the illustrated example, a negative lead 20 is provided, but it is also possible to omit the negative lead 20. Even without the negative lead 20, the negative electrode 12 is electrically connected to the outer can 38 through the contact between the inner side of the outer can 38 and the electrode group 14 (outermost periphery 12a) which is fixed by tape 40 to the winding end 14e, thus sufficiently reducing the internal resistance.

[0092] In the illustrated example, both the first and second tapes have a metal substrate layer, but either the first or second tape may have a resin substrate layer. In this case, the effect of the resin tape is small, while the metal tape can reduce internal resistance and suppress the discharge delay of the electrode assembly. Examples of resins contained in the resin substrate layer include polypropylene resin. The static friction coefficient of the resin substrate layer relative to the material of the outer can is preferably 0.8 or less. If either the first or second tape has a metal substrate layer with a static friction coefficient relative to the material of the outer can exceeding 0.8, a delay in the discharge of the electrode assembly will occur.

[0093] Postscript

[0094] Based on the above description of the embodiments, the following technical solution is disclosed.

[0095] (Technical Solution 1)

[0096] A secondary battery includes an electrode assembly, an adhesive tape, an electrolyte, and a bottomed cylindrical outer casing for housing the electrode assembly, the adhesive tape, and the electrolyte.

[0097] The electrode assembly is formed by winding a positive electrode, a negative electrode, and a separator. The negative electrode has a negative current collector, and the separator is located between the positive electrode and the negative electrode.

[0098] The tape secures the end of the winding of the electrode assembly.

[0099] The negative electrode has an outermost peripheral portion disposed on the outermost periphery of the electrode group.

[0100] The tape has a metal substrate layer and is attached to the outermost negative electrode current collector.

[0101] The negative current collector, with the tape attached, is in contact with the outermost periphery of the outer packaging can.

[0102] The static friction coefficient of the metal substrate layer relative to the material of the outer can is less than 0.8.

[0103] (Technical Solution 2)

[0104] The secondary battery according to technical solution 1

[0105] The static friction coefficient of the metal substrate layer relative to the material of the outer can is less than 0.6.

[0106] (Technical Solution 3)

[0107] The secondary battery according to technical solution 1 or 2

[0108] The negative electrode has a negative electrode flux layer supported on the negative electrode current collector.

[0109] The negative electrode mixture layer is not carried on at least a portion of the outermost peripheral region opposite the outer can.

[0110] (Technical Solution 4)

[0111] The secondary battery according to any one of technical solutions 1 to 3,

[0112] The metal substrate layer comprises at least one selected from nickel, iron, copper, titanium, zinc, silver, gold, and stainless steel.

[0113] (Technical Solution 5)

[0114] The secondary battery according to any one of technical solutions 1 to 4,

[0115] The outer can is made of stainless steel.

[0116] (Technical Solution 6)

[0117] The secondary battery according to any one of technical solutions 1 to 5,

[0118] The tape has an adhesive layer.

[0119] The adhesive layer is disposed on the surface of the outermost peripheral side of the metal substrate layer.

[0120] (Technical Solution 7)

[0121] The secondary battery according to any one of technical solutions 1 to 6,

[0122] The thickness of the tape is less than 250 μm.

[0123] (Technical Solution 8)

[0124] The secondary battery according to any one of technical solutions 1 to 7,

[0125] The width of the tape is 4mm or more and 12mm or less.

[0126] (Technical Solution 9)

[0127] The secondary battery according to any one of technical solutions 1 to 8,

[0128] The length of the tape is more than 1 mm and less than 7 mm shorter than the outer perimeter of the electrode assembly.

[0129] (Technical Solution 10)

[0130] The secondary battery according to any one of technical solutions 1 to 9,

[0131] The tape includes a first tape and a second tape, which are respectively attached to one end and the other end of the electrode assembly along the winding axis to the outermost negative current collector.

[0132] The first tape and the second tape each have a metal substrate layer having a static friction coefficient of 0.8 or less relative to the material of the outer can.

[0133] At the center of the winding axis of the electrode assembly, the outermost negative current collector contacts the outer can.

[0134] [Example]

[0135] The present disclosure will now be described in detail based on embodiments and comparative examples, but the present disclosure is not limited to the following embodiments.

[0136] Secondary batteries E1~E9, R1~R3

[0137] (The production of the positive electrode)

[0138] A positive electrode slurry is prepared by mixing the positive electrode active material, acetylene black, and polyvinylidene fluoride (PVDF) in a mass ratio of 95:2.5:2.5, adding an appropriate amount of N-methyl-2-pyrrolidone, and stirring. The positive electrode active material is a lithium-containing transition metal oxide containing nickel, cobalt, and aluminum. Next, the positive electrode slurry is coated onto both sides of an aluminum foil serving as the positive electrode current collector. After drying, the coating is rolled to form a positive electrode binder layer. The positive electrode current collector with the binder layer formed on both sides is then cut to a specified size to manufacture the positive electrode.

[0139] (Making the negative electrode)

[0140] A negative electrode slurry is prepared by mixing graphite (the negative electrode active material), styrene-butadiene copolymer rubber (SBR), and sodium carboxymethyl cellulose (CMC-Na) in a mass ratio of 98:1:1, and then adding an appropriate amount of water and stirring. Next, the negative electrode slurry is coated onto both sides of a copper foil serving as the negative electrode current collector, the coating is dried, and then rolled to form a negative electrode binder layer. The negative electrode current collector with the binder layer formed on both sides is cut to a specified size to manufacture the negative electrode. On one surface of the outermost region of the negative electrode (the entire region opposite the outer can), the negative electrode current collector is exposed, without forming a binder layer.

[0141] The static friction coefficient of the outermost negative current collector relative to the material of the outer can is less than 0.6.

[0142] (Preparation of non-aqueous electrolytes)

[0143] LiPF6 was dissolved at a concentration of 1.0 mol / L in a mixed solvent of ethylene carbonate and dimethyl carbonate (volume ratio 3:7) to prepare a non-aqueous electrolyte.

[0144] (Fabrication of the electrode assembly)

[0145] One end of an aluminum positive electrode lead is attached to the positive electrode. One end of a nickel negative electrode lead is attached to the negative electrode. In an inert gas atmosphere, the positive and negative electrodes are wound into a spiral shape with a porous polyethylene membrane acting as a separator, thereby fabricating an electrode assembly.

[0146] (Fixing the end of the electrode assembly winding)

[0147] Secure the winding end of the electrode assembly with tape. Specifically, as follows: Figures 3-5As shown, a first adhesive tape 41 and a second adhesive tape 42 are respectively attached to two locations on the outer periphery 14s of the electrode assembly 14 (on one end 141 side and the other end 142 side of the winding shaft). The first adhesive tape 41 has a first substrate layer and a first adhesive layer formed on one surface (the surface on the outermost peripheral side) of the first substrate layer. The second adhesive tape 42 has a second substrate layer and a second adhesive layer formed on one surface (the surface on the outermost peripheral side) of the second substrate layer.

[0148] The materials for the first and second substrate layers are as shown in Table 1. Additionally, PP in Table 1 refers to polypropylene resin. The static friction coefficients of the first substrate layer relative to the outer can material and the static friction coefficients of the second substrate layer relative to the outer can material are shown in Table 1.

[0149] The thickness of the first tape 41 and the second tape 42 is 150 μm when a metal substrate layer is provided, and 30 μm when a PP substrate layer is provided. The width of the first tape 41 and the second tape 42 is 9 mm.

[0150] The lengths of the first tape 41 and the second tape 42 are 2 mm shorter than the length of the outer periphery 14s of the electrode assembly 14.

[0151] The distance L1 between the first tape 41 and one end 141 of the electrode assembly 14 in the winding axis direction, and the distance L2 between the second tape 42 and the other end 142 of the electrode assembly 14 in the winding axis direction, are both 5 mm. The distance L3 between the first tape 41 and the second tape 42 is 36 mm.

[0152] The thickness of the first and second adhesive layers is 30 μm in the case of a metal substrate and 10 μm in the case of a PP substrate. Acrylic adhesives are used for both the first and second adhesive layers.

[0153] (Assembly of secondary batteries)

[0154] Prepare a bottom-mounted cylindrical stainless steel (SUS) outer casing. Place the electrode assembly inside the casing. Connect the other end of the positive electrode lead to the sealing plate, and the other end of the negative electrode lead to the inner bottom surface of the casing. After injecting the non-aqueous electrolyte, seal the opening of the casing with the sealing plate. Then, place a gasket between the sealing plate and the opening of the casing. This completes the construction of a cylindrical non-aqueous electrolyte secondary battery.

[0155] [evaluate]

[0156] The secondary battery was charged at a constant current of 500mA until the voltage reached 4.2V, resulting in a fully charged battery. The internal resistance at this point was then measured.

[0157] In addition, an internal short-circuit test based on heating was conducted. Specifically, a fully charged secondary battery was placed in a furnace at 200°C, and the electrode assembly ejection mechanism was activated. Thermocouples were used to measure the temperature near the center of the side of the cylindrical battery, and the maximum temperature at this point was measured.

[0158] Table 1

[0159]

[0160] In secondary batteries E1 to E2, where either the first or second tape is Cu tape and the other is PP tape, the internal resistance is reduced, and the temperature rise during an internal short circuit is suppressed. In secondary battery E3, where both the first and second tapes are Cu tapes, the internal resistance is further reduced, and the temperature rise during an internal short circuit is further suppressed.

[0161] In secondary batteries E4 to E5, where either the first or second tape is SUS tape and the other is PP tape, the internal resistance is reduced, and the temperature rise during an internal short circuit is suppressed. In secondary battery E6, where both the first and second tapes are SUS tapes, the internal resistance is further reduced, and the temperature rise during an internal short circuit is further suppressed.

[0162] In secondary batteries E7-E8, where either the first or second tape is a Ni tape and the other is a PP tape, the internal resistance is reduced, and the temperature rise during an internal short circuit is suppressed. In secondary battery E9, where both the first and second tapes are Ni tapes, the internal resistance is further reduced, and the temperature rise during an internal short circuit is further suppressed.

[0163] In the secondary battery R1, where both the first and second tapes are PP tapes, the internal resistance increases because there is a high-resistivity PP tape between the outer can and the electrode assembly.

[0164] In the secondary battery R1, since both the first and second tapes are PP tapes, the melting of PP during a short circuit has a significant impact (the amount of PP melted between the outer can and the electrode assembly is large), which causes a delay in the discharge of the electrode assembly and an increase in the maximum temperature during a short circuit.

[0165] On the other hand, in secondary batteries E1, E2, E4, E5, E7, and E8, either the first or second tape is a PP tape, and the other is a Cu, SUS, or Ni tape. Therefore, the impact of PP melting during a short circuit is small, and the temperature rise during a short circuit is suppressed.

[0166] In secondary battery R2, where both the first and second tapes are Al tapes, the static friction coefficient of the Al tape is greater than 0.8. Therefore, due to the delayed discharge of the electrode assembly, the maximum temperature during a short circuit increases significantly. In secondary battery R3, the first tape is a Cu tape, but the second tape is an Al tape with a static friction coefficient greater than 0.8. Therefore, due to the delayed discharge of the electrode assembly, the maximum temperature during a short circuit also increases.

[0167] Industry availability

[0168] This disclosure can be used for secondary batteries containing wound electrode arrays housed in an outer can.

[0169] The present invention has been described in conjunction with currently preferred embodiments, but this disclosure should not be construed as restrictive. Various variations and modifications will be apparent to those skilled in the art upon reading the above disclosure. Therefore, the appended claims should be interpreted as including all variations and modifications without departing from the true spirit and scope of the invention.

[0170] Explanation of reference numerals in the attached figures

[0171] 10: Secondary battery, 11: Positive electrode, 12: Negative electrode, 12a: Outer periphery of negative electrode, 13: Separator, 14: Electrode assembly, 14s: Outer periphery of electrode assembly, 14e: End of winding of electrode assembly, 31: Sealing plate, 38: Outer can, 40: Adhesive tape, 41: First adhesive tape, 42: Second adhesive tape.

Claims

1. A secondary battery comprising an electrode assembly, an adhesive tape, an electrolyte, and a bottomed cylindrical outer casing for housing the electrode assembly, the adhesive tape, and the electrolyte. The electrode assembly is formed by winding a positive electrode, a negative electrode, and a separator. The negative electrode has a negative current collector, and the separator is located between the positive electrode and the negative electrode. The tape secures the end of the winding of the electrode assembly. The negative electrode has an outermost peripheral portion disposed on the outermost periphery of the electrode group. The tape has a metal substrate layer and is attached to the outermost negative electrode current collector. The negative current collector, with the tape attached, is in contact with the outermost periphery of the outer packaging can. The static friction coefficient of the metal substrate layer relative to the material of the outer can is less than 0.

8.

2. The secondary battery according to claim 1, The static friction coefficient of the metal substrate layer relative to the material of the outer can is less than 0.

6.

3. The secondary battery according to claim 1, The negative electrode has a negative electrode flux layer supported on the negative electrode current collector. The negative electrode mixture layer is not carried on at least a portion of the outermost peripheral region opposite the outer can.

4. The secondary battery according to claim 1, The metal substrate layer comprises at least one selected from nickel, iron, copper, titanium, zinc, silver, gold, and stainless steel.

5. The secondary battery according to claim 1, The outer can is made of stainless steel.

6. The secondary battery according to claim 1, The tape has an adhesive layer. The adhesive layer is disposed on the surface of the outermost peripheral side of the metal substrate layer.

7. The secondary battery according to claim 1, The thickness of the tape is less than 250 μm.

8. The secondary battery according to claim 1, The width of the tape is 4mm or more and 12mm or less.

9. The secondary battery according to claim 1, The length of the tape is more than 1 mm and less than 7 mm shorter than the outer perimeter of the electrode assembly.

10. The secondary battery according to claim 1, The tape includes a first tape and a second tape, which are respectively attached to one end and the other end of the electrode assembly along the winding axis to the outermost negative current collector. The first tape and the second tape each have a metal substrate layer having a static friction coefficient of 0.8 or less relative to the material of the outer can. At the center of the winding axis of the electrode assembly, the outermost negative current collector contacts the outer can.

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