WO2020177599A1 - 二次电池 - Google Patents

二次电池 Download PDF

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Publication number
WO2020177599A1
WO2020177599A1 PCT/CN2020/076824 CN2020076824W WO2020177599A1 WO 2020177599 A1 WO2020177599 A1 WO 2020177599A1 CN 2020076824 W CN2020076824 W CN 2020076824W WO 2020177599 A1 WO2020177599 A1 WO 2020177599A1
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WO
WIPO (PCT)
Prior art keywords
electrode assembly
electrode
secondary battery
insulating tape
battery according
Prior art date
Application number
PCT/CN2020/076824
Other languages
English (en)
French (fr)
Inventor
李志凌
李晖
张婷婷
周勇
何佳宁
吴维清
李白清
Original Assignee
青海时代新能源科技有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from CN201910155674.1A external-priority patent/CN110190340B/zh
Priority claimed from CN201920265229.6U external-priority patent/CN209401784U/zh
Application filed by 青海时代新能源科技有限公司 filed Critical 青海时代新能源科技有限公司
Priority to JP2021550680A priority Critical patent/JP7374204B2/ja
Publication of WO2020177599A1 publication Critical patent/WO2020177599A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/572—Means for preventing undesired use or discharge
    • H01M50/584—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries
    • H01M50/586—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries inside the batteries, e.g. incorrect connections of electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the invention relates to the field of batteries, in particular to a secondary battery.
  • the secondary battery includes an electrode assembly and a case for accommodating the electrode assembly.
  • the existing case is usually connected to the positive electrode of the electrode assembly to keep the case at a higher potential to prevent corrosion.
  • the case will increase the short circuit risk of the secondary battery after being charged.
  • metal foreign matter will remain on the outer surface of the electrode assembly; while the electrode assembly expands during the working process and squeezes the shell at the end of the cycle. At this time, the metal foreign matter is likely to pierce the electrode assembly. Separator, and connect the negative electrode of the electrode assembly with the casing, which causes a short circuit and causes safety risks.
  • the object of the present invention is to provide a secondary battery that can reduce the risk of short circuit and improve safety performance.
  • the present invention provides a secondary battery including an electrode assembly, a case, a top cover assembly and a first insulating tape.
  • the electrode assembly includes one or more electrode units, the electrode unit has a positive pole piece, a negative pole piece, and a separator arranged between the positive pole piece and the negative pole piece, and the electrode unit is a winding
  • the negative pole piece of the outermost circle of the electrode unit is located outside the positive pole piece of the outermost circle.
  • the casing has a first side wall and an accommodating cavity, the electrode assembly is accommodated in the accommodating cavity, the casing is electrically connected to the positive pole piece, and the top cover assembly is connected to the casing.
  • the first insulating tape is located between the electrode assembly and the first side wall, and is closely attached to the outer surface of the electrode assembly.
  • the negative electrode tab includes a negative electrode current collector and a negative electrode active material layer coated on both surfaces of the negative electrode current collector. Along the length direction parallel to the winding axis of the electrode unit, the end of the first insulating tape extends beyond the negative active material layer.
  • the electrode assembly has two end faces opposed to each other in the length direction, and the end of the first insulating tape does not exceed the end face.
  • the first insulating tape includes a base and an adhesive layer, and the base is adhered to the outer surface of the electrode assembly through the adhesive layer.
  • the thickness of the substrate is 10 ⁇ m-50 ⁇ m, and the elastic modulus of the substrate is 1 Gpa-6 Gpa.
  • the thickness of the adhesive layer is 0.5 ⁇ m-15 ⁇ m, and the adhesive strength of the adhesive layer is greater than 0.05 N/mm 2 .
  • the secondary battery further includes a protective member located inside the case, and the protective member separates the electrode assembly and the first insulating tape from the case. open.
  • the outer surface of the electrode assembly includes a first surface and a second surface
  • the first surface is a flat surface and is located at an end of the electrode assembly in the thickness direction
  • the second surface is connected to the first surface and is located at an end of the electrode assembly in the width direction.
  • the first side wall is located on a side of the electrode assembly close to the first surface in the thickness direction, and the first insulating tape is located between the first surface and the first side wall.
  • the secondary battery further includes a second insulating tape, at least part of the second insulating tape is in close contact with the second surface, and the second insulating tape is The first insulating tape is integrally formed.
  • the ratio of the area of the first insulating tape to the area of the first surface is 75%-95%.
  • the electrode units are plural and arranged along the thickness direction, each of the electrode units has a narrow surface along the width direction, and the second surface includes each The narrow face of the electrode unit.
  • the narrow surface is at least partially a circular arc surface.
  • the edge of the first insulating tape extends to an intersection line between the first surface and the second surface.
  • the first sidewalls are two and are respectively located on both sides of the electrode assembly in the thickness direction.
  • the housing further includes two second side walls, the two second side walls are respectively disposed on both sides of the electrode assembly along the width direction, the two first side walls and the two The second side wall is connected to form a rectangular frame.
  • the area of the first side wall is larger than the area of the second side wall.
  • the top cover assembly includes a top cover plate, an electrode terminal, and an adapter sheet, the top cover plate is connected to the case, and the electrode terminal is disposed on the top cover. Board, the adapter sheet electrically connects the electrode terminal and the electrode assembly.
  • first insulating tapes there are two first insulating tapes and are respectively located at both ends of the electrode assembly in the thickness direction.
  • the beneficial effects of the present invention are as follows: by closely attaching the first insulating tape to the outer surface of the electrode assembly, the metal foreign matter attached to the outer surface of the electrode assembly can be reduced; furthermore, when the electrode assembly expands, the first insulating tape can The first side wall is separated from the electrode assembly, so as to prevent metal foreign objects from piercing the diaphragm, prevent the electrode assembly from being electrically connected to the first side wall, reduce the risk of short circuit, and improve the insulation performance and safety performance.
  • Fig. 1 is a schematic diagram of a secondary battery according to the present invention.
  • Fig. 2 is another schematic diagram of a secondary battery according to the present invention.
  • FIG. 3 is a schematic diagram of an embodiment of the electrode assembly and the first insulating tape of FIG. 2.
  • Figure 4 is a cross-sectional view of Figure 3.
  • Figure 5 is a cross-sectional view taken along the line A-A of Figure 4.
  • FIG. 6 is a schematic diagram of the electrode unit of FIG. 4.
  • FIG. 7 is a schematic diagram of another embodiment of the electrode assembly and the first insulating tape of FIG. 2.
  • the secondary battery of the present application includes an electrode assembly 1, a case 2, a top cover assembly 3, and a first insulating tape 4.
  • the electrode assembly 1 includes electrode units 11, and there may be one or more electrode units 11; in this embodiment, the electrode units 11 are preferably multiple and arranged along the thickness direction Y. 4 to 6, the electrode unit 11 includes a positive pole piece 111, a negative pole piece 112, and a separator 113 disposed between the positive pole piece 111 and the negative pole piece 112.
  • the electrode unit 11 may be formed by spirally winding the positive pole piece 111, the negative pole piece 112, and the separator 113, and the electrode unit 11 is pressed to form a flat structure.
  • the positive pole piece 111 includes a positive current collector 111c and a positive active material layer 111d coated on both surfaces of the positive current collector 111c.
  • the positive current collector 111c may be aluminum foil, and the positive active material layer 111d includes lithium manganate or lithium iron phosphate.
  • the positive electrode current collector 111c has a positive electrode blank area that is not covered by the positive electrode active material layer 111d.
  • the negative pole piece 112 includes a negative current collector 112c and a negative active material layer 112d coated on both surfaces of the negative current collector 112c.
  • the negative current collector 112c may be copper foil, and the negative active material layer 112d includes graphite or silicon.
  • the negative electrode current collector 112c has a negative electrode blank area that is not covered by the negative electrode active material layer 112d.
  • the lithium ions in the positive electrode active material layer 111d need to pass through the separator 113 and be embedded in the negative electrode active material layer 112d; during winding, if the positive electrode piece 111 is finished (ie the electrode unit 11 The outermost negative pole piece 112 of the outermost circle is located inside the outermost positive pole piece 111), then the lithium ions of the outermost positive pole piece 111 cannot be inserted into the negative pole piece 112, which causes the problem of lithium evolution. Therefore, preferably, the outermost negative pole piece 112 of the electrode unit 11 of the present application is located outside the outermost positive pole piece 111. Of course, in order to ensure insulation, the outermost diaphragm 113 of the electrode unit 11 is located outside the outermost negative pole piece 112.
  • the electrode unit 11 includes a narrow surface 11a and a main surface 11b.
  • the main surface 11b is located at both ends of the electrode unit 11 in the thickness direction Y, and the main surface 11b is substantially flat.
  • the narrow surface 11a is located at both ends of the electrode unit 11 in the width direction X and is at least partially arc-shaped.
  • the narrow surface 11a connects the two main surfaces 11b.
  • the area of the main surface 11b is larger than the area of the narrow surface 11a.
  • the thickness direction Y and the width direction X are perpendicular to each other, and both the thickness direction Y and the width direction X are perpendicular to the winding axis of the electrode unit 11.
  • both the narrow surface 11a and the main surface 11b are surfaces where the diaphragm 113 is exposed.
  • a containing cavity 22 is formed inside the casing 2 to contain the electrode assembly 1 and the electrolyte.
  • the receiving cavity 22 has an opening at one end, and the electrode assembly 1 can be placed into the receiving cavity 22 through the opening.
  • the housing 2 can be made of conductive metal materials such as aluminum or aluminum alloy.
  • the housing 2 may be prismatic. Specifically, the housing 2 includes a first side wall 21, a second side wall 23, and a bottom wall.
  • the first side walls 21 are two and are respectively disposed on the electrode assembly 1 along the thickness direction Y.
  • the two first side walls 21 and the two second side walls 23 are connected together to form an approximately rectangular frame. body.
  • the bottom wall is disposed on the lower side of the first side wall 21 and the second side wall 23 and connected to the first side wall 21 and the second side wall 23, the bottom wall, the two first side walls 21 and the two second side walls 23 encloses the housing cavity 22 of the housing 2.
  • the first side wall 21 has a larger area.
  • the top cover assembly 3 includes a top cover plate 31, an electrode terminal 32 and an adapter piece 33.
  • the top cover plate 31 is connected to the casing 2 and covers the opening of the casing 2 to seal the opening of the casing 2.
  • the electrode terminal 32 is provided on the top cover plate 31, and the adapter piece 33 can be electrically connected to the electrode terminal 32 and the electrode assembly 1 by welding or the like.
  • the top cover 31 and the bottom wall of the housing 2 are respectively located on both sides of the electrode assembly 1.
  • the top cover plate 31 may be a metal plate, and the top cover plate 31 is electrically connected to the positive electrode terminal 32 and insulated from the negative electrode terminal 32.
  • the housing 2 can be sealed to the top cover 31 by welding or the like.
  • the electrolyte is likely to corrode the case 2 and affect the performance and life of the secondary battery.
  • the case 2 is electrically connected to the positive pole piece 111 via the top cover 31 and the positive electrode terminal 32. Connect, so that the casing 2 can be maintained at a high potential, avoid electrochemical corrosion, and improve the performance and life of the secondary battery.
  • the generated metal foreign matter is easily sputtered and attached to the outer surface of the electrode assembly 1.
  • the electrode assembly 1 will expand, and the expansion of the electrode assembly 1 in the thickness direction Y is the most serious; during expansion, the electrode assembly 1 will squeeze the first side wall 21, and under pressure, it will adhere to the electrode
  • the metal foreign matter on the surface of the assembly 1 easily pierces the separator 113, and conducts the negative electrode active material layer 112d of the negative pole piece 112 with the first side wall 21.
  • the inside of the electrode assembly 1 will quickly Generate heat, thereby causing safety risks.
  • a first insulating tape 4 is preferably arranged on the outer surface of the electrode assembly 1.
  • the first insulating tape 4 is in close contact with the outer surface of the electrode assembly 1 and is located between the electrode assembly 1 and the first side wall 21. between.
  • a plurality of electrode units 11 are laminated together, and the plurality of electrode units 11 constitute the electrode assembly 1; when laminating, the first insulating tape 4 is set to the outside of the electrode assembly 1.
  • step (i) when the number of electrode assemblies 1 is large, it is only necessary to paste the first insulating tape 4 on the surfaces of the two outermost electrode units 11. Therefore, in step (i), the surface of some electrode units 11 does not need to be pasted. An insulating tape 4.
  • the metal foreign matter generated by the welding is easily attached to the outer surface of the electrode assembly.
  • the electrode assembly expands during the working process and squeezes the shell at the end of the cycle.
  • the metal foreign body easily pierces the diaphragm of the electrode assembly and connects the negative electrode of the electrode assembly with the shell, causing a short circuit and causing safety risks.
  • the first insulating tape 4 is bonded on the outer surface of the electrode assembly 1.
  • the first insulating tape 4 can protect the electrode assembly 1, thereby reducing metal foreign matter directly attached to the outer surface of the electrode assembly 1.
  • the first insulating tape 4 can separate the first side wall 21 from the electrode assembly 1, so as to prevent the metal foreign matter remaining between the first insulating tape 4 and the housing 2 from piercing the diaphragm 113 and prevent the electrode
  • the assembly 1 is electrically connected to the first side wall 21, which reduces the risk of short circuit and improves the insulation performance.
  • the metal foreign matter may remain between the first insulating tape 4 and the electrode assembly 1.
  • the metal foreign matter is still easy to puncture Breaking the diaphragm 113 and even puncturing the negative pole piece 112 affects the performance of the secondary battery.
  • the first insulating tape 4 is closely attached to the outer surface of the electrode assembly 1, so metal foreign matter hardly enters between the first insulating tape 4 and the electrode assembly 1, thereby preventing the metal foreign matter from piercing the diaphragm 113 and the electrode assembly 1.
  • the size of the negative electrode active material layer 112d of the negative pole piece 112 is usually larger than that of the positive electrode.
  • the size of the positive electrode active material layer 111d of the pole piece 111 is usually larger than that of the positive electrode.
  • one end 112a of the negative electrode active material layer 112d exceeds one end 111a of the positive electrode active material layer 111d; at the other end of the electrode assembly 1 along the length direction Z At one end, the other end 112b of the anode active material layer 112d extends beyond the other end 111b of the cathode active material layer 111d.
  • the size of the separator 113 along the length direction Z is generally larger than the size of the negative electrode active material layer 112d; specifically, at one end of the electrode assembly 1 along the length direction Z, one end 113a of the separator 113 extends beyond the negative electrode active material One end 112a of the layer 112d; at the other end of the electrode assembly 1 along the length direction Z, the other end 113b of the separator 113 extends beyond the other end 112b of the negative electrode active material layer 112d.
  • the separator 113 completely covers the positive electrode active material layer 111d and the negative electrode active material layer 112d in the longitudinal direction Z.
  • the end of the first insulating tape 4 extends beyond the negative electrode active material layer 112d of the negative electrode piece 112. That is, at one end of the electrode assembly 1 along the length direction Z, one end 4a of the first insulating tape 4 extends beyond one end 112a of the negative active material layer 112d; at the other end of the electrode assembly 1 along the length direction Z, The other end 4b of an insulating tape 4 extends beyond the other end 112b of the negative electrode active material layer 112d.
  • the first insulating tape 4 can completely cover the negative electrode active material layer 112d, thereby improving insulation performance, minimizing the risk of conduction between the negative electrode active material layer 112d and the first side wall 21, and improving safety performance.
  • the electrode assembly 1 has two end faces 12 opposite to each other along the length direction Z. Specifically, after the electrode assembly 1 is wound into shape, the two ends of the diaphragm 113 are wound into multiple turns, each end approximately forms a surface, and the surface formed by each end is the end surface 12. A small gap is left on the two end surfaces 12, and the electrolyte can enter the inside of the electrode assembly 1 through the gap, thereby improving the wettability.
  • the end of the first insulating tape 4 does not exceed the end surface 12, that is, along the length direction Z, the first insulating tape 4 is located between the two end surfaces of the electrode assembly 1. . If the end of the first insulating tape 4 exceeds the end surface 12, the part of the first insulating tape 4 beyond the end surface 12 is easily bent onto the end surface 12 during assembly or use, thereby covering the gap on the end surface 12 and affecting the wettability. , Causing the risk of lithium analysis.
  • the first insulating tape 4 includes a base 41 and an adhesive layer 42, and the base 41 is attached to the outer surface of the electrode assembly 1 through the adhesive layer 42.
  • the material of the base 41 may be a flexible polymer, such as PMMA or PET.
  • the material of the adhesive layer 42 can be acrylate or ethyl acetate.
  • the base 41 is directly adhered to the outer surface of the electrode assembly 1 via the adhesive layer 42, and there is no gap between the first insulating tape 4 and the electrode assembly 1, so as to prevent metal foreign matter from entering the first insulating tape 4 and the electrode assembly 1 between.
  • the first insulating tape 4 can reduce the metal foreign matter adhering to the outer surface of the electrode assembly 1, the metal foreign matter will still adhere to the outer surface of the first insulating tape 4. Therefore, the first insulating tape 4 needs to have Enough thickness to avoid being pierced by metal foreign bodies.
  • the first insulating tape 4 since the electrode assembly 1 will expand and deform during use, the first insulating tape 4 must be capable of corresponding elastic deformation with the expansion and contraction of the electrode assembly 1, so as to ensure the cycle performance and safety performance of the secondary battery.
  • the thickness of the substrate 41 is 10 ⁇ m-50 ⁇ m, and the elastic modulus is 1 Gpa-6 Gpa.
  • the size of the metal foreign matter produced by welding is uneven.
  • the thickness of the base 41 is less than 10 ⁇ m, the metal foreign matter with a larger size may still pierce the first insulating tape 4, causing the negative pole piece 112 and The first side wall 21 is electrically connected, causing a risk of short circuit;
  • the thickness of the base 41 is greater than 50 ⁇ m, the volume of the first insulating tape 4 is relatively large, which occupies the internal space of the housing 2. Therefore, by limiting the thickness dimension of the base body 41 to 10 ⁇ m-50 ⁇ m, the risk of short circuit can be effectively reduced, and at the same time, it can be ensured that the first insulating tape 4 does not occupy too much space in the housing 2.
  • the thickness of the base 41 is 12 ⁇ m-30 ⁇ m.
  • the base 41 When the elastic modulus of the base 41 is less than 1 Gpa, the base 41 is prone to plastic deformation under the expansion pressure, resulting in the thickness of the base 41 being reduced and the strength weakened. At this time, the metal foreign matter may pierce the first insulating tape 4 and cause a negative electrode.
  • the pole piece 112 is electrically connected to the first side wall 21, causing a short circuit risk.
  • the elastic modulus of the base 41 When the elastic modulus of the base 41 is greater than 6 Gpa, the base 41 will hardly deform under the expansion pressure, that is, the base 41 will restrain the expansion of the electrode assembly 1; under the restraining force, the partial electrolyte of the electrode assembly 1 It is squeezed out, resulting in insufficient electrolyte, so that lithium ions cannot pass through the separator 113, and lithium precipitation is initiated. Therefore, by restricting the elastic modulus of the matrix 41 to be greater than 1 Gpa and less than 6 Gpa, the risk of short circuit can be effectively reduced, and at the same time, the generation of lithium can be avoided and the cycle performance can be improved.
  • the elastic modulus of the base 41 is 1.2 Gpa-4.5 Gpa.
  • the thickness of the adhesive layer 42 is 0.5 ⁇ m-15 ⁇ m. If the thickness of the adhesive layer 42 is less than 0.5 ⁇ m, the adhesive strength of the adhesive layer 42 is too low, which may easily cause the base 41 to separate from the electrode assembly 1 and cause the protection function of the base 41 to fail. If the thickness of the adhesive layer 42 is greater than 15 ⁇ m, the space occupied by the adhesive layer 42 will be too large and the energy density of the secondary battery will be reduced.
  • the adhesive strength of the adhesive layer 42 is preferably greater than 0.05 N/mm 2 .
  • the outer surface of the electrode assembly 1 includes two first surfaces 13 and two second surfaces 14.
  • the two first surfaces 13 are generally flat surfaces and are respectively located at the two ends of the electrode assembly 1 in the thickness direction Y, and the two second surfaces 14 are respectively located at the two ends of the electrode assembly 1 in the width direction X. Two ends of each second surface 14 are respectively connected to two first surfaces 13.
  • the plurality of electrode units 11 of the electrode assembly 1 are sequentially arranged along the thickness direction Y. Therefore, among all the main surfaces 11b of the plurality of electrode units 11, the one closest to the first side wall 21 is The surface 11b is exposed, and the other main surface 11b closest to the other first side wall 21 is exposed.
  • the two exposed main surfaces 11b are the two first surfaces 13 of the electrode assembly 1 respectively.
  • the “exposure” refers to the electrode assembly 1 as a whole.
  • One second surface 14 includes a narrow surface 11a at one end of each electrode unit 11 in the width direction X, and the other second surface 14 includes a narrow surface 11a at the other end of each electrode unit 11 in the width direction X.
  • the two first surfaces 13 are respectively located at both ends of the electrode assembly 1 along the thickness direction Y, and the two second surfaces 14 are respectively located at both ends of the electrode assembly 1 along the width direction X.
  • the first surface 13 and the second The two surfaces 14 intersect each other, so the intersection line L is formed at the junction of the first surface 13 and the second surface 14.
  • the area of the main surface 11b of the electrode unit 11 is larger than the area of the narrow surface 11a, when the electrode unit 11 expands during use, the main surface 11b of the electrode unit 11 deforms more seriously; in other words, the thickness of the electrode unit 11 is not large.
  • the protrusion size of the main surface 11b of the electrode unit 11 in the thickness direction Y is larger than the protrusion size of the narrow surface 11a in the thickness direction Y. Therefore, the first surface 13 is easier to press the housing 2 than the second surface 14.
  • the first surface 13 is generally a flat surface
  • the second surface 14 includes a plurality of narrow surfaces 11b and each narrow surface 11b is at least partly an arc surface, even if the first surface 13 and the second surface 14 are deformed to the same degree
  • the contact area between the first surface 13 and the housing 2 is larger than the contact area between the second surface 14 and the housing 2. Therefore, the main surface 11b of the electrode unit 11 has a higher risk of short circuit than the narrow surface 11a.
  • the gap reserved between the electrode assembly 1 and the housing 2 is relatively small, especially the gap between the first surface 13 and the first side wall 21.
  • the first surface 13 is susceptible to the force of the first side wall 21; and since the second surface 14 is generally arc-shaped, the second surface 14 and the second side wall 23 and the second surface 14
  • the first insulating tape 4 is closely attached to the first surface 13, that is, the first insulating tape 4 is adhered to the first surface 13.
  • the first insulating tape 4 can separate the first side wall 21 from the first surface 13, so as to prevent metal foreign objects from piercing the first surface 13, prevent the negative active material layer 112d from being electrically connected to the first side wall 21, and improve the insulation performance.
  • the edge of the first insulating tape 4 extends to the intersection line L.
  • the two edges of the first insulating tape 4 along the width direction X are the first edge 4c and the second edge 4d, respectively; in the width direction X, the first edge 4c is aligned with the intersection line L located at one end of the first surface 13 The second edge 4d is flush with the intersection line L located at the other end of the first surface 13.
  • the first insulating tape 4 can completely separate the first side wall 21 from the negative pole piece 112, thereby avoiding electrical connection between the first side wall 21 and the negative pole piece 112 and improving insulation performance.
  • the ratio of the area of the first insulating tape 4 to the area of the first surface 13 is preferably 75%-95%. If the area ratio is greater than 95%, when bonding the first insulating tape 4, the first insulating tape 4 is likely to be misaligned, causing the first insulating tape 4 to extend beyond the end surface 12, affecting wettability and causing a risk of lithium evolution.
  • the secondary battery further includes a protective member 6 located inside the casing 2.
  • the protective member 6 can surround the electrode assembly 1 and the first insulating tape 4. To separate the electrode assembly 1 from the housing 2 and separate the electrode assembly 1 from the first insulating tape 4 from the housing 2.
  • the protective member 6 generally encloses a rectangular cavity, and the electrode assembly 1 and the first insulating tape 4 are contained in the cavity and surrounded by the protective member 6.
  • step (iv) before putting the electrode assembly 1 and the first insulating tape 4 adhered to the electrode assembly 1 into the housing 2, firstly, the protective member 6 is surrounded by the electrode assembly 1 and the first insulating tape 4 Then put the protective member 6, the electrode assembly 1 and the first insulating tape 4 into the housing 2 together, and finally weld the housing 2 and the top cover plate 31 of the top cover assembly 3 to realize the seal.
  • the secondary battery further includes a second insulating tape 5, the second insulating tape 5 at least partially closely adhere to the second surface 14, and the second insulating tape 5 and the first insulation With 4 connected.
  • the first insulating tape 4 and the second insulating tape 5 are preferably integral members.

Abstract

本发明提供了一种二次电池，其包括电极组件、壳体、顶盖组件和第一绝缘带。电极组件包括一个或多个电极单元，电极单元具有正极极片、负极极片和设置于正极极片、负极极片之间的隔膜，电极单元为卷绕式结构且为扁平状，电极单元的最外圈的负极极片位于最外圈的正极极片的外侧。壳体具有第一侧壁和容纳腔，电极组件收容于容纳腔，壳体与正极极片电连接，顶盖组件密封连接于壳体。第一绝缘带位于电极组件与第一侧壁之间，且与电极组件的外表面紧密贴合。

Description

二次电池 技术领域
本发明涉及电池领域，尤其涉及一种二次电池。
背景技术
二次电池包括电极组件和用于收容电极组件的壳体，现有的壳体通常与电极组件的正极导通，使壳体保持较高的电位以防止腐蚀。然而，壳体带电后会增大二次电池的短路风险。例如，在装配二次电池的过程中，会在电极组件的外表面残留金属异物；而电极组件在工作过程中膨胀并在循环后期挤压壳体，此时，金属异物容易刺破电极组件的隔膜，并将电极组件的负极与壳体连通，从而造成短路，引发安全风险。
发明内容
鉴于背景技术中存在的问题，本发明的目的在于提供一种二次电池，其能降低短路风险，提高安全性能。
为了实现上述目的，本发明提供了一种二次电池，其包括电极组件、壳体、顶盖组件和第一绝缘带。所述电极组件包括一个或多个电极单元，所述电极单元具有正极极片、负极极片和设置于所述正极极片、所述负极极片之间的隔膜，所述电极单元为卷绕式结构且为扁平状，所述电极单元的最外圈的负极极片位于最外圈的正极极片的外侧。所述壳体具有第一侧壁和容纳腔，所述电极组件收容于所述容纳腔，所述壳体与所述正极极片电连接，所述顶盖组件连接于所述壳体。所述第一绝缘带位于所述电极组件与所述第一侧壁之间，且与所述电极组件的外表面紧密贴合。
在根据一些实施例的二次电池中，所述负极极片包括负极集流体和涂覆于所述负极集流体两个表面的负极活性物质层。沿平行于所述电极单元的卷绕轴的长度方向，所述第一绝缘带的端部超出所述负极活性物质层。
在根据一些实施例的二次电池中，所述电极组件具有沿所述长度方向相 对设置的两个端面，所述第一绝缘带的端部不超出所述端面。
在根据一些实施例的二次电池中，所述第一绝缘带包括基体和粘接层，所述基体通过所述粘接层粘贴于所述电极组件的外表面。
在根据一些实施例的二次电池中，所述基体的厚度为10μm-50μm，所述基体的弹性模量为1Gpa-6Gpa。
在根据一些实施例的二次电池中，所述粘接层的厚度为0.5μm-15μm，所述粘接层的粘接强度大于0.05N/mm 2。
在根据一些实施例的二次电池中，所述二次电池还包括位于所述壳体内部的保护构件，所述保护构件将所述电极组件以及所述第一绝缘带与所述壳体隔开。
在根据一些实施例的二次电池中，所述电极组件的外表面包括第一表面和第二表面，所述第一表面为平整面并且位于所述电极组件沿所述厚度方向的端部，所述第二表面连接于所述第一表面并且位于所述电极组件沿宽度方向的端部。所述第一侧壁位于所述电极组件沿所述厚度方向靠近所述第一表面的一侧，所述第一绝缘带位于所述第一表面与所述第一侧壁之间。
在根据一些实施例的二次电池中，所述二次电池还包括第二绝缘带，所述第二绝缘带的至少部分与所述第二表面紧密贴合，且所述第二绝缘带与所述第一绝缘带一体形成。
在根据一些实施例的二次电池中，所述第一绝缘带的面积与所述第一表面的面积之比为75％-95％。
在根据一些实施例的二次电池中，所述电极单元为多个且沿所述厚度方向排列，各所述电极单元沿所述宽度方向的端部具有窄面，所述第二表面包括各所述电极单元的所述窄面。
在根据一些实施例的二次电池中，所述窄面至少部分为圆弧面。
在根据一些实施例的二次电池中，沿所述宽度方向，所述第一绝缘带的边缘延伸至所述第一表面和所述第二表面之间的相交线。
在根据一些实施例的二次电池中，所述第一侧壁为两个且分别位于所述电极组件沿所述厚度方向的两侧。所述壳体还包括两个第二侧壁，所述两个第二侧壁分别设置于所述电极组件沿所述宽度方向的两侧，所述两个第一侧壁和所述两个第二侧壁连接并形成矩形的框体。所述第一侧壁的面积大于所 述第二侧壁的面积。
在根据一些实施例的二次电池中，所述顶盖组件包括顶盖板、电极端子和转接片，所述顶盖板连接于所述壳体，所述电极端子设置于所述顶盖板，所述转接片电连接所述电极端子和所述电极组件。
在根据一些实施例的二次电池中，所述第一绝缘带为两个且分别位于所述电极组件沿所述厚度方向的两端。
本发明的有益效果如下：通过将第一绝缘带与电极组件的外表面紧密贴合，可以减少电极组件的外表面附着的金属异物；再者，当电极组件膨胀时，第一绝缘带能够将第一侧壁和电极组件隔开，从而避免金属异物刺穿隔膜，防止电极组件与第一侧壁电连接，降低短路风险，提高绝缘性能和安全性能。
附图说明
图1为根据本发明的二次电池的一示意图。
图2为根据本发明的二次电池的另一示意图。
图3为图2的电极组件和第一绝缘带的一实施例的示意图。
图4为图3的一断面图。
图5为图4沿线A-A作出的断面图。
图6为图4的电极单元的示意图。
图7为图2的电极组件和第一绝缘带的另一实施例的示意图。
其中，附图标记说明如下：
1电极组件                   22容纳腔
11电极单元                  23第二侧壁
111正极极片                 3顶盖组件
111c正极集流体              31顶盖板
111d正极活性物质层          32电极端子
112负极极片                 33转接片
112c负极集流体              4第一绝缘带
112d负极活性物质层          41基体
113隔膜                     42粘接层
11a窄面                     4c第一边缘
11b主面                       4d第二边缘
12端面                        5第二绝缘带
13第一表面                    6保护构件
14第二表面                    X宽度方向
2壳体                         Y厚度方向
21第一侧壁                    Z长度方向
具体实施方式
为了使本申请的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本申请进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本申请，并不用于限定本申请。
在本申请的描述中，除非另有明确的规定和限定，术语“第一”、“第二”、“第三”仅用于描述的目的，而不能理解为指示或暗示相对重要性；术语“多个”是两个以上(包括两个)；除非另有规定或说明，术语“连接”应做广义理解，例如，“连接”可以是固定连接，也可以是可拆卸连接，或一体地连接，或电连接，或信号连接；“连接”可以是直接相连，也可以通过中间媒介间接相连。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
本说明书的描述中，需要理解的是，本申请实施例所描述的“上”、“下”等方位词是以附图所示的角度来进行描述的，不应理解为对本申请实施例的限定。下面通过具体的实施例并结合附图对本申请做进一步的详细描述。
参照图1和图2，本申请的二次电池包括电极组件1、壳体2、顶盖组件3和第一绝缘带4。
电极组件1包括电极单元11，电极单元11可为一个或多个；在本实施例中，电极单元11优选为多个且沿厚度方向Y排列。参照图4至图6，电极单元11包括正极极片111、负极极片112和设置于正极极片111、负极极片112之间的隔膜113。电极单元11可通过螺旋地卷绕正极极片111、负极极片112和隔膜113而形成，且电极单元11经过压力按压形成扁平状结构。
正极极片111包括正极集流体111c和涂覆于正极集流体111c两个表面的正极活性物质层111d，正极集流体111c可为铝箔，正极活性物质层111d 包括锰酸锂或磷酸铁锂。正极集流体111c具有未被正极活性物质层111d覆盖的正极空白区域。负极极片112包括负极集流体112c和涂覆于负极集流体112c两个表面的负极活性物质层112d，负极集流体112c可为铜箔，负极活性物质层112d包括石墨或硅。负极集流体112c具有未被负极活性物质层112d覆盖的负极空白区域。
在二次电池的工作过程中，正极活性物质层111d内的锂离子需要穿过隔膜113并嵌入到负极活性物质层112d中；在卷绕时，如果以正极极片111收尾(即电极单元11的最外圈的负极极片112位于最外圈的正极极片111的内侧)，那么最外圈的正极极片111的锂离子无法嵌入到负极极片112中，从而引发析锂问题。因此，优选地，本申请的电极单元11的最外圈的负极极片112位于最外圈的正极极片111的外侧。当然，为了保证绝缘性，电极单元11的最外圈的隔膜113位于最外圈的负极极片112的外侧。
参照图6，电极单元11包括窄面11a和主面11b，主面11b位于电极单元11沿厚度方向Y的两端，且主面11b大体为平面。窄面11a位于电极单元11沿宽度方向X的两端且至少部分为圆弧面，窄面11a连接两个主面11b。主面11b的面积大于窄面11a的面积。其中，厚度方向Y和宽度方向X彼此垂直，且厚度方向Y和宽度方向X均垂直于电极单元11的卷绕轴。另外，由于电极单元11最外圈为隔膜113，所以窄面11a和主面11b均为隔膜113外露的表面。
壳体2内部形成有容纳腔22，以收容电极组件1和电解液。容纳腔22在一端形成开口，而电极组件1可经由所述开口放置到容纳腔22内。壳体2可由铝或铝合金等导电金属的材料制成。
壳体2可为棱柱形，具体地，壳体2包括第一侧壁21、第二侧壁23和底壁，第一侧壁21为两个且分别设置于电极组件1沿厚度方向Y的两侧，第二侧壁23为两个且分别设置于电极组件1沿宽度方向X的两侧，两个第一侧壁21和两个第二侧壁23连接在一起并形成近似矩形的框体。底壁设置于第一侧壁21和第二侧壁23的下侧且连接于第一侧壁21和第二侧壁23，底壁、两个第一侧壁21和两个第二侧壁23围成壳体2的容纳腔22。与第二侧壁23相比，第一侧壁21具有较大的面积。
参照图1，顶盖组件3包括顶盖板31、电极端子32和转接片33。顶盖 板31连接于壳体2并覆盖壳体2的开口，以将壳体2的开口密封。电极端子32设置于顶盖板31，转接片33可通过焊接等方式分别与电极端子32、电极组件1电连接。在长度方向Z上，顶盖板31和壳体2的底壁分别位于电极组件1的两侧。
电极端子32可为两个，其中，正极性的电极端子32经由一个转接片33与正极极片111电连接，负极性的电极端子32经由另一个转接片33与负极极片112电连接。顶盖板31可为金属板，且顶盖板31与正极性的电极端子32电连接，与负极性的电极端子32绝缘。壳体2可通过焊接等方式与顶盖板31密封连接。
在已知技术中，电解液容易腐蚀壳体2，影响二次电池的性能和寿命；而在本申请中，壳体2经由顶盖板31和正极性的电极端子32与正极极片111电连接，从而使壳体2能够保持在高电位，避免电化学腐蚀，改善二次电池的性能和寿命。
在装配二次电池过程中，产生的金属异物容易溅射并附着到电极组件1的外表面。在工作过程中，电极组件1会出现膨胀，且电极组件1在厚度方向Y上的膨胀最为严重；膨胀时，电极组件1会挤压第一侧壁21，在压力的作用下，附着在电极组件1表面的金属异物容易刺破隔膜113，并将负极极片112的负极活性物质层112d和第一侧壁21导通，尤其当二次电池处于满充电状态时，电极组件1内部会迅速产热，从而引发安全风险。
因此，优选地，本申请优选在电极组件1的外表面上设置第一绝缘带4，第一绝缘带4与电极组件1的外表面紧密贴合且位于电极组件1与第一侧壁21之间。第一绝缘带4优选为两个，且两个第一绝缘带4分别位于电极组件1沿厚度方向Y的两端。
下面简要说明本申请的二次电池的成型过程：
(i)将正极极片111、负极极片112和隔膜113卷绕为一体以制备出电极单元11；卷绕成型后在电极单元11的表面粘贴第一绝缘带4。
(ii)将多个电极单元11层叠在一起，多个电极单元11组成电极组件1；层叠时，将第一绝缘带4设置到电极组件1的外侧。
(iii)将电极单元11的正极空白区域和负极空白区域分别焊接到两个转接片33，然后再将两个转接片33焊接到顶盖组件1的两个电极端子32。
(iv)将电极组件1以及粘接在电极组件1上的第一绝缘带4放入壳体2内，然后将壳体2与顶盖组件3的顶盖板31焊接，实现壳体2的密封。
其中，当电极组件1的数量较多时，只需在最外侧的两个电极单元11的表面上粘贴第一绝缘带4，因此，在步骤(i)中，一些电极单元11的表面无需粘贴第一绝缘带4。
在已知技术中，当焊接电极端子和转接片时，焊接产生的金属异物很容易附着到电极组件的外表面。而电极组件在工作过程中膨胀并在循环后期挤压壳体，此时，金属异物容易刺破电极组件的隔膜，并将电极组件的负极与壳体连通，从而造成短路，引发安全风险。
而在本申请中，在将转接片33与电极端子32焊接之前，先在电极组件1的外表面上粘接第一绝缘带4；在焊接转接片33与电极端子32时，第一绝缘带4可以保护电极组件1，从而减少直接附着到电极组件1的外表面的金属异物。
当电极组件1膨胀时，第一绝缘带4能够将第一侧壁21和电极组件1隔开，从而避免第一绝缘带4与壳体2之间存留的金属异物刺穿隔膜113，防止电极组件1与第一侧壁21电连接，降低短路风险，提高绝缘性能。
如果第一绝缘带4与电极组件1的外表面之间留有空隙，那么金属异物可能会残留在第一绝缘带4和电极组件1之间；当电极组件1膨胀时，金属异物仍然容易刺破隔膜113，甚至刺伤负极极片112，影响二次电池的性能。而在本申请中，第一绝缘带4与电极组件1的外表面紧密贴合，所以金属异物几乎不会进入第一绝缘带4和电极组件1之间，从而避免金属异物刺破隔膜113和负极极片112。
为了保证正极极片111的锂离子能够尽可能地嵌入到负极极片112中，沿平行于电极单元11的卷绕轴的长度方向Z，负极极片112的负极活性物质层112d尺寸通常大于正极极片111的正极活性物质层111d尺寸。具体地，参照图5，在电极组件1沿长度方向Z的一端，负极活性物质层112d的一个端部112a超出正极活性物质层111d的一个端部111a；在电极组件1沿长度方向Z的另一端，负极活性物质层112d的另一个端部112b超出正极活性物质层111d的另一个端部111b。而为了保证绝缘性能，沿长度方向Z，隔膜113的尺寸通常大于负极活性物质层112d的尺寸；具体地，在电极组件1沿 长度方向Z的一端，隔膜113的一个端部113a超出负极活性物质层112d的一个端部112a；在电极组件1沿长度方向Z的另一端，隔膜113的另一个端部113b超出负极活性物质层112d的另一个端部112b。此时，隔膜113沿长度方向Z完全覆盖正极活性物质层111d和负极活性物质层112d。
优选地，在本申请中，沿平行于电极单元11的卷绕轴的长度方向Z，第一绝缘带4的端部超出负极极片112的负极活性物质层112d。也就是说，在电极组件1沿长度方向Z的一端，第一绝缘带4的一个端部4a超出负极活性物质层112d的一个端部112a；在电极组件1沿长度方向Z的另一端，第一绝缘带4的另一个端部4b超出负极活性物质层112d的另一个端部112b。此时，在长度方向Z上，第一绝缘带4能够完全覆盖负极活性物质层112d，从而改善绝缘性能，最大程度上降低负极活性物质层112d与第一侧壁21导通的风险，提高安全性能。
电极组件1具有沿长度方向Z相对设置的两个端面12。具体地，当电极组件1卷绕成型后，隔膜113的两个端部卷绕为多圈，各端部近似形成一个面，各端部形成的面即为端面12。所述两个端面12上留有细小的缝隙，而电解液可经由所述缝隙进入电极组件1的内部，从而改善浸润性。
在本申请中，优选地，沿长度方向Z，第一绝缘带4的端部不超出端面12，也就是说，沿长度方向Z，第一绝缘带4位于电极组件1的两个端面之间。如果第一绝缘带4的端部超出端面12，那么在装配或使用过程中，第一绝缘带4超出端面12的部分容易弯折到端面12上，从而遮挡端面12上的缝隙，影响浸润性，引发析锂风险。
第一绝缘带4包括基体41和粘接层42，基体41通过粘接层42粘贴于电极组件1的外表面。基体41的材质可为柔性聚合物，例如PMMA或PET。粘接层42的材质可为丙烯酸酯或乙酸乙酯。
在本申请中，基体41经由粘接层42直接粘接到电极组件1的外表面，第一绝缘带4与电极组件1之间无间隙，从而避免金属异物进入第一绝缘带4和电极组件1之间。在本申请中，第一绝缘带4虽然能够减少附着于电极组件1的外表面的金属异物，但是金属异物仍然会附着在第一绝缘带4的外表面，因此，第一绝缘带4需要具有足够的厚度，以避免自身被金属异物刺穿。另外，由于电极组件1在使用过程中会膨胀变形，第一绝缘带4必须保 证能够随电极组件1的膨胀收缩而发生相应地弹性形变，从而保证二次电池的循环性能和安全性能。
在本申请中，基体41的厚度10μm-50μm，弹性模量为1Gpa-6Gpa。
在二次电池装配过程中，由焊接产生金属异物的尺寸不均，当基体41的厚度小于10μm时，尺寸较大的金属异物仍然可能会刺破第一绝缘带4，导致负极极片112与第一侧壁21电连接，引发短路风险；当基体41的厚度大于50μm时，第一绝缘带4的体积较大，占用壳体2的内部空间。因此，通过限制基体41的厚度尺寸为10μm-50μm，可以有效地降低短路风险，同时还能够保证第一绝缘带4不会过多地占用壳体2空间。优选地，基体41的厚度12μm-30μm。
当基体41的弹性模量小于1Gpa时，基体41在膨胀压力下极容易发生塑性变形，导致基体41的厚度变小、强度变弱，此时金属异物可能刺破第一绝缘带4，造成负极极片112与第一侧壁21电连接，引发短路风险。当基体41的弹性模量大于6Gpa时，基体41在膨胀压力下几乎不会变形，也就是说，基体41会束缚电极组件1的膨胀；在束缚力的作用下，电极组件1局部的电解液被挤出，造成电解液不足的现象，从而导致锂离子无法通过隔膜113，引发析锂。故通过限制基体41的弹性模量大于1Gpa且小于6Gpa，可以有效地降低短路风险，同时还能够避免产生析锂，提高循环性能。优选地，基体41的弹性模量为1.2Gpa-4.5Gpa。
粘接层42的厚度为0.5μm-15μm。如果粘接层42的厚度小于0.5μm，那么粘接层42的粘接强度偏低，容易导致基体41与电极组件1分离，造成基体41的保护功能失效。如果粘接层42的厚度大于15μm，会导致粘接层42占用的空间过大，降低二次电池的能量密度。
当电极组件1膨胀时，隔膜113与粘接层42之间会产生应力集中，为避免隔膜113与粘接层42分离，粘接层42的粘接强度优选大于0.05N/mm 2。
参照图3，电极组件1的外表面包括两个第一表面13和两个第二表面14。两个第一表面13大体为平整面并且分别位于电极组件1沿厚度方向Y的两端，两个第二表面14分别位于电极组件1沿宽度方向X的两端。各第二表面14的两端分别连接于两个第一表面13。
在本实施例中，电极组件1的多个电极单元11沿厚度方向Y依次排列， 因此，在所述多个电极单元11的所有主面11b中，最靠近一个第一侧壁21的一个主面11b露出，最靠近另一个第一侧壁21的另一个主面11b露出。露出的两个主面11b则分别为电极组件1的两个第一表面13。另外，所述“露出”是相对于电极组件1整体而言。
由于窄面11a至少部分为圆弧面，相邻的电极单元11的窄面11a之间留有间隙，各电极单元11的窄面11a不会被其它电极单元11覆盖，因此，多个电极单元11的窄面11a均露出。一个第二表面14包括各电极单元11沿宽度方向X一端的窄面11a，另一个第二表面14包括各电极单元11沿宽度方向X另一端的窄面11a。
在本申请中，两个第一表面13分别位于电极组件1沿厚度方向Y的两端，而两个第二表面14分别位于电极组件1沿宽度方向X的两端，第一表面13和第二表面14彼此相交，所以第一表面13和第二表面14的交界处会形成相交线L。
由于电极单元11的主面11b的面积大于窄面11a的面积，所以当电极单元11在使用过程中膨胀时，电极单元11的主面11b变形较为严重；换句话说，在电极单元11厚度不变的情况下，电极单元11的主面11b沿厚度方向Y凸出的尺寸大于窄面11a沿厚度方向Y凸出的尺寸。因此，第一表面13相比第二表面14更容易挤压壳体2。再者，第一表面13大体为平整面，且第二表面14包括多个窄面11b并且每个窄面11b至少部分为圆弧面，即使第一表面13和第二表面14变形的程度相同，第一表面13与壳体2接触面积相比于第二表面14与壳体2接触面积更大。因此，电极单元11的主面11b相比于窄面11a存在更高的短路风险。
为了提高能量密度，电极组件1与壳体2之间预留的间隙较小，特别是第一表面13和第一侧壁21之间的间隙。当电极组件1膨胀时，第一表面13容易受到第一侧壁21的作用力；而由于第二表面14大体为弧形，第二表面14与第二侧壁23之间以及第二表面14与第一侧壁21之间均留有较大的间隙，所以电极组件1膨胀时，第二表面14不易受到第二侧壁23和第一侧壁21的作用力。因此，优选地，第一绝缘带4与第一表面13紧密贴合，也就是说，第一绝缘带4粘接在第一表面13上。第一绝缘带4能够将第一侧壁21与第一表面13隔开，从而避免金属异物刺穿第一表面13，防止负极活性 物质层112d与第一侧壁21电连接，提高绝缘性能。
参照图4，沿宽度方向X，第一绝缘带4的边缘延伸至相交线L。具体地，第一绝缘带4沿宽度方向X的两个边缘分别为第一边缘4c和第二边缘4d；在宽度方向X上，第一边缘4c与位于第一表面13一端的相交线L齐平，第二边缘4d与位于第一表面13另一端的相交线L齐平。此时，在宽度方向X上，第一绝缘带4能够将第一侧壁21与负极极片112完全隔开，从而避免第一侧壁21与负极极片112电连接，提高绝缘性能。
第一表面13的未被第一绝缘带4覆盖的区域仍然存在被金属异物刺破的风险，因此，为了保证绝缘性能，第一绝缘带4的面积与第一表面13的面积之比优选为75％-95％。如果所述面积比大于95％，那么在粘接第一绝缘带4时，第一绝缘带4容易出现错位，导致第一绝缘带4超出端面12，影响浸润性，引发析锂风险。
为了进一步提高绝缘性能和避免第一绝缘带4在进入壳体2时损伤，二次电池还包括位于壳体2内部的保护构件6，保护构件6可环绕在电极组件1和第一绝缘带4的外侧，以将电极组件1与壳体2隔开和将电极组件1与第一绝缘带4与壳体2隔开。保护构件6大体围成一个矩形的空腔，而电极组件1和第一绝缘带4收容在所述空腔内并被保护构件6包围。具体地，在步骤(iv)中，在将电极组件1以及粘接在电极组件1上的第一绝缘带4放入壳体2之前，首先将保护构件6环绕在电极组件1和第一绝缘带4的外侧，然后将保护构件6、电极组件1和第一绝缘带4一起放入壳体2内部，最后将壳体2与顶盖组件3的顶盖板31焊接，实现壳体2的密封。
参照图7，在替代的实施例中，所述二次电池还包括第二绝缘带5，第二绝缘带5至少部分与第二表面14紧密贴合，且第二绝缘带5与第一绝缘带4相连。第一绝缘带4和第二绝缘带5优选为一体式构件。如果没有第二绝缘带5，那么粘贴第一绝缘带4时，需要确保第一边缘4c和第二边缘4d与相交线L齐平，对工艺精度要求较高；而通过设置第二绝缘带5，可以允许第一边缘4c与相交线L出现错位，只要保证相交线L被第一绝缘带4或第二绝缘带5覆盖，从而简化绝缘带的粘接工艺。

Claims (16)

  1. 一种二次电池，其特征在于，包括电极组件(1)、壳体(2)、顶盖组件(3)和第一绝缘带(4)；
    所述电极组件(1)包括一个或多个电极单元(11)，所述电极单元(11)具有正极极片(111)、负极极片(112)和设置于所述正极极片(111)、所述负极极片(112)之间的隔膜(113)，所述电极单元(11)为卷绕式结构且为扁平状，所述电极单元(11)的最外圈的负极极片(112)位于最外圈的正极极片(111)的外侧；
    所述壳体(2)具有第一侧壁(21)和容纳腔(22)，所述电极组件(1)收容于所述容纳腔(22)，所述壳体(2)与所述正极极片(111)电连接，所述顶盖组件(3)连接于所述壳体(2)；
    所述第一绝缘带(4)位于所述电极组件(1)与所述第一侧壁(21)之间，且与所述电极组件(1)的外表面紧密贴合。
  2. 根据权利要求1所述的二次电池，其特征在于，
    所述负极极片(112)包括负极集流体(112c)和涂覆于所述负极集流体(112c)两个表面的负极活性物质层(112d)；
    沿平行于所述电极单元(11)的卷绕轴的长度方向(Z)，所述第一绝缘带(4)的端部超出所述负极活性物质层(112d)。
  3. 根据权利要求2所述的二次电池，其特征在于，所述电极组件(1)具有沿所述长度方向(Z)相对设置的两个端面(12)，所述第一绝缘带(4)的端部不超出所述端面(12)。
  4. 根据权利要求1-3中任一项所述的二次电池，其特征在于，所述第一绝缘带(4)包括基体(41)和粘接层(42)，所述基体(41)通过所述粘接层(42)粘贴于所述电极组件(1)的外表面。
  5. 根据权利要求4所述的二次电池，其特征在于，所述基体(41)的厚 度为10μm-50μm，所述基体(41)的弹性模量为1Gpa-6Gpa。
  6. 根据权利要求4或5所述的二次电池，其特征在于，所述粘接层(42)的厚度为0.5μm-15μm，所述粘接层(42)的粘接强度大于0.05N/mm 2。
  7. 根据权利要求1-6中任一项所述的二次电池，其特征在于，所述二次电池还包括位于所述壳体(2)内部的保护构件(6)，所述保护构件(6)将所述电极组件(1)以及所述第一绝缘带(4)与所述壳体(2)隔开。
  8. 根据权利要求1-7任一项所述的二次电池，其特征在于，
    所述电极组件(1)的外表面包括第一表面(13)和第二表面(14)，所述第一表面(13)为平整面并且位于所述电极组件(1)沿所述厚度方向(Y)的端部，所述第二表面(14)连接于所述第一表面(13)并且位于所述电极组件(1)沿宽度方向(X)的端部；
    所述第一侧壁(21)位于所述电极组件(1)沿所述厚度方向(Y)靠近所述第一表面(13)的一侧，所述第一绝缘带(4)位于所述第一表面(13)与所述第一侧壁(21)之间。
  9. 根据权利要求8所述的二次电池，其特征在于，所述二次电池还包括第二绝缘带(5)，所述第二绝缘带(5)的至少部分与所述第二表面(14)紧密贴合，且所述第二绝缘带(5)与所述第一绝缘带(4)一体形成。
  10. 根据权利要求8或9所述的二次电池，其特征在于，所述第一绝缘带(4)的面积与所述第一表面(13)的面积之比为75％-95％。
  11. 根据权利要求8-10中任一项所述的二次电池，其特征在于，所述电极单元(11)为多个且沿所述厚度方向(Y)排列，各所述电极单元(11)沿所述宽度方向(X)的端部具有窄面(11a)，所述第二表面(14)包括各所述电极单元(11)的所述窄面(11a)。
  12. 根据权利要求11所述的二次电池，其特征在于，所述窄面(11a)至少部分为圆弧面。
  13. 根据权利要求8-12中任一项所述的二次电池，其特征在于，沿所述宽度方向(X)，所述第一绝缘带(4)的边缘延伸至所述第一表面(13)和所述第二表面(14)之间的相交线。
  14. 根据权利要求1-13中任一项所述的二次电池，其特征在于，
    所述第一侧壁(21)为两个且分别位于所述电极组件(1)沿所述厚度方向(Y)的两侧；
    所述壳体(2)还包括两个第二侧壁(23)，所述两个第二侧壁(23)分别设置于所述电极组件沿所述宽度方向(X)的两侧，所述两个第一侧壁(21)和所述两个第二侧壁(23)连接并形成矩形的框体；
    所述第一侧壁(21)的面积大于所述第二侧壁(23)的面积。
  15. 根据权利要求1-14中任一项所述的二次电池，其特征在于，
    所述顶盖组件(3)包括顶盖板(31)、电极端子(32)和转接片(33)，所述顶盖板(31)连接于所述壳体(2)，所述电极端子(32)设置于所述顶盖板(31)，所述转接片(33)电连接所述电极端子(32)和所述电极组件(1)。
  16. 根据权利要求1-15中任一项所述的二次电池，其特征在于，所述第一绝缘带(4)为两个且分别位于所述电极组件(1)沿所述厚度方向(Y)的两端。
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