WO2024036507A1 - 电化学装置以及电子装置 - Google Patents

电化学装置以及电子装置 Download PDF

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WO2024036507A1
WO2024036507A1 PCT/CN2022/113002 CN2022113002W WO2024036507A1 WO 2024036507 A1 WO2024036507 A1 WO 2024036507A1 CN 2022113002 W CN2022113002 W CN 2022113002W WO 2024036507 A1 WO2024036507 A1 WO 2024036507A1
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Prior art keywords
negative electrode
layer
winding
positive electrode
active material
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PCT/CN2022/113002
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English (en)
French (fr)
Inventor
闫东阳
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宁德新能源科技有限公司
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Priority to PCT/CN2022/113002 priority Critical patent/WO2024036507A1/zh
Priority to CN202280007085.9A priority patent/CN116547851A/zh
Publication of WO2024036507A1 publication Critical patent/WO2024036507A1/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
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • 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 present application relates to the field of energy storage devices, and in particular, to an electrochemical device and an electronic device.
  • Electrochemical devices such as batteries are widely used in electronic products such as electronic mobile devices, power tools, and electric vehicles. After long-term charge and discharge cycles, lithium will precipitate on the surface of the negative electrode of the electrochemical device to form lithium dendrites, thus affecting the service life of the electrochemical device.
  • the present application provides an electrochemical device that can reduce the possibility of lithium precipitation from the negative electrode piece.
  • the present application also provides an electronic device having the above electrochemical device.
  • a first aspect of the present application provides an electrochemical device, including an electrode assembly.
  • the electrode assembly includes stacked and wound negative electrode pieces and positive electrode pieces.
  • the negative electrode sheet includes a first negative active material layer, a negative current collector and a second negative active material layer that are stacked in sequence.
  • the first negative active material layer is closer to the winding center axis than the second negative active material layer.
  • the positive electrode sheet includes a first positive electrode active material layer, a positive electrode current collector and a second positive electrode active material layer that are stacked in sequence.
  • the first positive electrode active material layer is closer to the winding center axis than the second positive electrode active material layer.
  • the negative electrode current collector includes a negative electrode empty foil area, a negative electrode single-sided area, and a negative electrode double-sided area that are connected in sequence.
  • the negative electrode piece includes a negative electrode winding first layer and a negative electrode winding sublayer.
  • the negative electrode single-sided area is provided with a second negative electrode active material layer, and the negative electrode single-sided area is located at least on the first layer of the negative electrode winding and the second layer of the negative electrode winding.
  • the positive electrode current collector includes a positive electrode double-sided area, and the positive electrode double-sided area is located on the side of the negative electrode winding sublayer away from the winding central axis.
  • the positive electrode double-sided area includes the starting end of the positive electrode double-sided area.
  • the negative electrode sheet also includes a first layer including an insulating material. The first layer is located on the negative electrode winding first layer and extends from the first negative electrode active material layer to the negative electrode empty foil area.
  • the negative electrode single-sided area is disposed on the negative electrode winding first layer and the starting end of the positive electrode double-sided area overlaps the negative electrode single-sided area located on the negative electrode winding first layer in the first direction, and at the same time, on the negative electrode winding first layer
  • the first layer is provided to improve the flatness of the electrochemical device. Therefore, the possibility of the formation splint first contacting the thicker part of the electrode assembly during the fixture formation process can be reduced, resulting in insufficient or even no pressure on other parts of the electrode assembly due to its thinness, thus reducing the risk of lithium precipitation and prolonging the electrochemical process. The service life of the device.
  • the first layer can also be used to fix the second negative electrode active material layer located on the negative electrode single-sided area of the negative electrode winding first layer, reducing the possibility of the negative electrode active material on this part of the second negative electrode active material layer falling off.
  • the starting end of the positive electrode bifacial region overlaps the first layer.
  • the first layer can further compensate for the thickness difference on both sides of the starting end of the positive electrode bifacial region of the electrode assembly in the first direction, which is beneficial to improving the flatness of the electrochemical device.
  • the positive electrode current collector further includes a positive electrode empty foil area, and the positive electrode empty foil area and the positive electrode double-sided area are connected in sequence along the winding direction.
  • the positive electrode sheet includes a positive electrode winding first layer and a positive electrode winding sub-layer, and the positive electrode double-sided area is located in the positive electrode winding sub-layer.
  • the negative electrode sheet further includes a first arc of negative electrode winding, a secondary arc of negative electrode winding, three layers of negative electrode winding, three arcs of negative electrode winding, and four layers of negative electrode winding.
  • the negative electrode winding first layer, the negative electrode winding first arc, the negative electrode winding secondary layer, the negative electrode winding secondary arc, the negative electrode winding three layers, the negative electrode winding three arcs and the negative electrode winding four layers are connected in sequence.
  • the single-sided area of the negative electrode extends from the first layer of the negative electrode winding to at least three arcs of the negative electrode winding.
  • the negative electrode double-sided area includes the starting end of the negative electrode double-sided area, and the starting end of the negative electrode double-sided area is located on the fourth layer of the negative electrode winding.
  • the direction from the first arc of the negative electrode winding to the second arc of the negative electrode winding is the second direction, and the first direction is perpendicular to the second direction.
  • the direction perpendicular to both the first direction and the second direction is the third direction.
  • the positive electrode tab further includes a second layer including an insulating material, the second layer extending from the first positive electrode active material layer or the second positive electrode active material layer to the positive electrode empty foil region.
  • the second layer includes a second layer starting end and a second layer ending end that are oppositely arranged in the winding direction, and the second layer starting end is located in the positive electrode empty foil area.
  • the line that passes through the starting end of the negative electrode double-sided region and extends in the first direction is a first virtual line
  • the line that passes through the termination end of the second layer and extends in the first direction is a second virtual line. In the second direction, the first virtual line is closer to the negative electrode winding first arc than the second virtual line.
  • the negative electrode single-sided area includes the starting end of the negative electrode single-sided area. Viewed from the third direction, the starting end of the negative electrode single-sided area is located between the first virtual line and the second virtual line, or the starting end of the negative electrode single-sided area is located on the side of the second virtual line away from the first virtual line in the second direction. . Therefore, the electrode assembly between the first virtual line and the second virtual line can be filled with the second negative electrode active material layer located on the negative electrode single-sided area of the negative electrode winding first layer to achieve thickness compensation, and can also be filled by the first negative electrode active material layer. Layers can be filled for thickness compensation. Therefore, the formed splint can tightly compact the area between the first virtual line and the second virtual line during the clamp forming process, improve the contact interface between the positive electrode piece and the negative electrode piece, and reduce the possibility of lithium precipitation.
  • the electrochemical device further includes a positive electrode tab.
  • the positive electrode tab is connected to the surface of the positive electrode empty foil area away from the winding central axis, and the positive electrode tab is located on the first layer of the positive electrode winding.
  • the second layer extends to the first layer of the positive electrode winding and overlaps with the positive electrode tab in the first direction. Therefore, the second layer can be used to cover the burrs or solder marks on the surface of the positive electrode tab, reducing the possibility that the above-mentioned burrs or solder marks will penetrate the isolation film and accidentally contact the negative electrode tab and short-circuit, thereby extending the service life of the electrochemical device.
  • the positive electrode tab is separated from the negative electrode single-sided area located on the first layer of the negative electrode winding. Therefore, the possibility that the thickness of the electrode assembly corresponding to the positive electrode tab increases when the two overlap is reduced, thereby improving the energy density of the electrochemical device.
  • the electrochemical device further includes a negative electrode tab and a third layer including an insulating material.
  • the negative electrode tab is connected to the surface of the negative electrode empty foil area facing the winding central axis, and the negative electrode tab is located on the first layer of the negative electrode winding.
  • the positive electrode empty foil area includes the starting end of the positive electrode empty foil area.
  • the third layer is located on the surface of the negative electrode empty foil area away from the winding central axis. In the first direction, the third layer overlaps the negative electrode tab and the starting end of the positive electrode empty foil area.
  • the third layer can be used to cover the welding marks or burrs of the negative electrode tab, and is also used to cover the starting end of the positive electrode empty foil area, reducing the possibility of accidental contact and short circuit between the positive electrode empty foil area and the negative electrode empty foil area.
  • the positive electrode tab, the negative electrode tab, and the starting end of the positive electrode empty foil area are separated in the first direction.
  • the positive electrode tab and the negative electrode tab are separated in the first direction, thus reducing the possibility that the thickness of the electrode assembly corresponding to the positive electrode tab increases when they overlap, thereby reducing the impact on the energy density of the electrochemical device.
  • the positive electrode tab is separated from the starting end of the positive electrode empty foil area in the first direction, thereby reducing the possibility that the positive electrode tab exceeds the positive electrode empty foil area during welding, and also reducing the accuracy requirements for the positive electrode tab welding position.
  • the second layer is disposed on a surface of the positive electrode empty foil area facing away from the winding central axis, and the second layer extends from the second positive electrode active material layer to the positive electrode empty foil area.
  • the second layer is used to insulate and protect the surface of the exposed positive electrode empty foil area, reducing the possibility of the positive electrode empty foil area accidentally contacting and short-circuiting the negative electrode empty foil area during mechanical abuse, and also reducing the possibility of mechanical abuse. It is possible that the positive electrode empty foil area is torn and the isolation film is pierced and the negative electrode empty foil area is mistakenly contacted and short-circuited.
  • the second layer can also reduce the possibility of lithium precipitation when the starting end of the negative electrode double-sided region does not exceed the starting end of the positive electrode double-sided region.
  • the positive electrode plate further includes a fourth layer including an insulating material.
  • the fourth layer is disposed on the surface of the positive electrode empty foil area facing the winding central axis, and the fourth layer extends from the first positive electrode active material layer to the positive electrode empty foil area.
  • the fourth layer is used to insulate and protect the surface of the exposed positive electrode empty foil area, reducing the possibility of the positive electrode empty foil area accidentally contacting and short-circuiting the negative electrode empty foil area during mechanical abuse, and also reducing the possibility of mechanical abuse. There is a possibility that the positive electrode empty foil area may be torn and then pierce the isolation film and mistakenly contact the negative electrode empty foil area and cause a short circuit.
  • the fourth layer includes a fourth layer starting end and a fourth layer ending end that are oppositely arranged in the winding direction.
  • the starting end of the fourth layer is located in the positive electrode empty foil area.
  • the fourth layer termination end is located between the first virtual line and the second virtual line.
  • the fourth layer is used to insulate and protect the surface of the exposed positive electrode empty foil area, reducing the possibility of the positive electrode empty foil area accidentally contacting and short-circuiting the negative electrode empty foil area during mechanical abuse, and also reducing the possibility of mechanical abuse. There is a possibility that the positive electrode empty foil area may be torn and then pierce the isolation film and mistakenly contact the negative electrode empty foil area and cause a short circuit.
  • the negative electrode sheet further includes a fifth layer including an insulating material, and the fifth layer is provided on the negative electrode winding secondary arc.
  • the fifth layer can increase the thickness of the negative electrode winding secondary arc, that is, increase the thickness at the corners of the electrode assembly. Therefore, in the fixture formation process, it is helpful to improve the contact interface between the positive electrode piece and the negative electrode piece at the corner of the electrode assembly and reduce the possibility of lithium precipitation at the corner.
  • the fifth layer is also used to support the negative electrode winding secondary arc and reduce the possibility of the negative electrode piece cracking if the curvature radius at the negative electrode winding secondary arc is too small.
  • the first negative active material layer includes a first negative active material, and the first negative active material includes graphite.
  • the second negative active material layer includes a second negative active material, and the second negative active material includes graphite.
  • the X-ray diffraction pattern of at least one of the first negative active material layer or the second negative active material layer includes a 004 diffraction peak and a 110 diffraction peak.
  • the ratio of the peak area of the 004 diffraction peak to the peak area of the 110 diffraction peak is the OI value of the first active material layer or the second negative active material layer, and the OI value ranges from 5.0 to 20.0.
  • the contact area between the electrolyte and the negative active material is increased, which improves the dynamic performance of the first negative active material layer or the second negative active material layer, enables faster insertion of lithium ions, and further reduces lithium evolution. possibility.
  • the OI ranges from 5.0 to 13.0, thereby further improving the kinetic performance of the first negative active material layer or the second negative active material layer and reducing the possibility of lithium evolution.
  • the peaks in the Raman spectrum of at least one of the first negative active material layer or the second negative active material layer with a shift range of 1255 cm -1 to 1355 cm -1 and 1575 cm - 1 to 1600 cm -1 are respectively D peak and G peak.
  • the intensity ratio of D peak and G peak ranges from 0.05 to 0.80.
  • the intensity ratio of the D peak and the G peak ranges from 0.30 to 0.80, thereby further reducing the possibility of lithium evolution.
  • the electrochemical device further includes an electrolyte.
  • the electrolyte contains lithium salt, and the concentration of the lithium salt in the electrolyte ranges from 0.5 mol/L to 2.5 mol/L. By increasing the lithium salt concentration, it is beneficial to increase the conductivity of the electrolyte, improve the kinetic performance of the electrochemical device, and further reduce the possibility of lithium precipitation.
  • the concentration of the lithium salt in the electrolyte ranges from 1.0 mol/L to 2.5 mol/L, thereby further reducing the possibility of lithium evolution.
  • the first layer, the second layer, and the third layer each independently include a substrate layer and an adhesive layer.
  • the adhesive layer has adhesive properties, and the base material layer is used to set and support the adhesive layer.
  • the thickness of the first layer ranges from 1 ⁇ m to 50 ⁇ m, such that the difference in thickness between the electrode assembly corresponding to the positive electrode tab and the electrode assembly located between the first imaginary line and the second imaginary line is small, thereby It is beneficial to improve the flatness of the electrochemical device.
  • a second aspect of the present application also provides an electronic device, which includes the electrochemical device as described above.
  • the electronic device is powered by the above-mentioned electrochemical device, and the possibility of lithium precipitation in the electrochemical device is reduced, so it has an improved service life.
  • FIG. 1 is a view along a first direction of an electrochemical device provided by an embodiment of the present application.
  • FIG. 2 is a view of the electrode assembly of the electrochemical device shown in FIG. 1 along a third direction.
  • FIG. 3A is a partial enlarged view of the electrode assembly A shown in FIG. 2 .
  • FIG. 3B is an expanded view of the negative electrode piece of the electrode assembly shown in FIG. 2 .
  • FIG. 3C is an expanded view of the positive electrode piece of the electrode assembly shown in FIG. 2 .
  • FIG. 4 is a partial enlarged view of the electrode assembly A shown in FIG. 2 in other embodiments.
  • FIG. 5 is a partial enlarged view of the electrode assembly A shown in FIG. 2 in other embodiments.
  • FIG. 6 is an enlarged view of the first layer of the electrode assembly shown in FIG. 3A.
  • FIG. 7 is an enlarged view of the second layer of the electrode assembly shown in FIG. 3A.
  • FIG. 8 is a partial enlarged view of the electrode assembly A shown in FIG. 2 in other embodiments.
  • FIG. 9 is a partial enlarged view of the electrode assembly A shown in FIG. 2 in other embodiments.
  • FIG. 10 is a partial enlarged view of the electrode assembly A shown in FIG. 2 in other embodiments.
  • FIG. 11 is a partial enlarged view of the electrode assembly A shown in FIG. 2 in other embodiments.
  • FIG. 12 is a partial enlarged view of the electrode assembly A shown in FIG. 2 in other embodiments.
  • FIG. 13 is an enlarged view of the fourth layer of the electrode assembly shown in FIG. 3A.
  • FIG. 14 is an enlarged view of the third layer of the electrode assembly shown in FIG. 3A.
  • FIG. 15 is an enlarged view of the fifth layer of the electrode assembly shown in FIG. 3A.
  • FIG. 16 is a schematic structural diagram of an electronic device according to an embodiment of the present application.
  • spatially relative terms such as “on,” etc., may be used herein for convenience to describe the relationship of one element or feature to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device or device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the diagram is turned over, elements described as “above” or “on” other elements or features would then be oriented “below” or “beneath” the other elements or features. Thus, the exemplary term “upper” may include both upper and lower directions. It will be understood that, although the terms first, second, third, etc.
  • an electrochemical device 100 including a housing 10 , an electrode assembly 20 , a negative electrode tab 30 , a positive electrode tab 40 and an electrolyte (not shown).
  • the electrode assembly 20 and the electrolyte are located in the housing 10, and the electrode assembly 20 has a wound structure.
  • the negative electrode tab 30 and the positive electrode tab 40 are both electrically connected to the electrode assembly 20 and extend out of the housing 10 from the inside.
  • the casing 10 may be a packaging bag sealed with a packaging film (such as aluminum-plastic film), that is, the electrochemical device 100 may be a soft-pack battery.
  • the electrochemical device 100 is not limited to soft-pack batteries, and may also be steel-shell batteries or aluminum-shell batteries.
  • FIG. 2 shows that the number of electrode assemblies 20 is one. In other embodiments, the number of electrode assemblies 20 may also be multiple. The plurality of electrode assemblies 20 are located in the housing 10 and are electrically connected in parallel or in series.
  • the electrode assembly 20 includes a negative electrode piece 21 , a positive electrode piece 22 and an isolation film 23 .
  • the isolation film 23 is disposed between the negative electrode piece 21 and the positive electrode piece 22 .
  • the negative electrode piece 21 , the isolation film 23 and the positive electrode piece 22 are stacked and wound in sequence to form the electrode assembly 20 .
  • the electrode assembly 20 has a winding center axis O perpendicular to the paper surface.
  • the electrode assembly 20 has a winding direction D.
  • the winding direction D refers to a certain point along the negative electrode piece 21, the positive electrode piece 22 or the isolation film 23 as shown in FIG. 2 around the winding central axis O from the inside to the outside. direction of movement.
  • winding directions D There are two winding directions D, namely, clockwise or counterclockwise rotation around the winding central axis O.
  • the winding direction D is the direction of counterclockwise rotation around the winding central axis O as shown in FIG. 2 .
  • the winding direction D may also be a clockwise rotation direction.
  • the negative electrode sheet 21 includes a negative electrode current collector 210 , a first negative electrode active material layer 211 and a second negative electrode active material layer 212 .
  • the negative electrode current collector 210 includes a first surface 210a and a second surface 210b arranged oppositely.
  • the first negative electrode active material layer 211 is provided on the first surface 210a
  • the second negative electrode active material layer 212 is provided on the second surface 210b.
  • the first negative active material layer 211 is closer to the winding center axis O than the second negative active material layer 212 .
  • the positive electrode sheet 22 includes a positive current collector 220 , a first positive active material layer 221 and a second positive active material layer 222 .
  • the positive current collector 220 includes a third surface 220a and a fourth surface 220b arranged oppositely.
  • the first positive active material layer 221 is provided on the third surface 220a, and the second positive active material layer 222 is provided on the fourth surface 220b.
  • the first cathode active material layer 221 is closer to the winding center axis O than the second cathode active material layer 222 .
  • a three-dimensional coordinate system is established based on the mutually perpendicular first direction D 1 , the second direction D 2 and the third direction D 3 .
  • the first direction D 1 is a direction perpendicular to one surface of the negative electrode tab 30 .
  • the second direction D 2 is the direction from the positive electrode tab 40 to the negative electrode tab 30 .
  • the third direction D 3 is the direction of the winding central axis O in some embodiments. Another three-dimensional coordinate system is established based on the mutually perpendicular fourth direction D 1 ′, the fifth direction D 2 ′ and the third direction D 3 .
  • the fourth direction D 1 ′ is the extension direction of the negative electrode piece 21 before winding, and is also the extension direction of the positive electrode piece 22 before winding.
  • the fifth direction direction is the extension direction of the negative electrode piece 21 before winding.
  • the positive electrode current collector 220 may use aluminum foil or nickel foil, and the negative electrode current collector 210 may use at least one of copper foil, nickel foil, or carbon-based current collector.
  • the cathode active material layer contains a cathode active material including a compound that reversibly intercalates and deintercalates lithium ions (ie, a lithiated intercalation compound).
  • the cathode active material may include lithium transition metal complex oxide.
  • the lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese and nickel.
  • the cathode active material is selected from lithium cobalt oxide (LiCoO 2 ), lithium nickel manganese cobalt ternary material (NCM), lithium manganate (LiMn 2 O 4 ), lithium nickel manganate (LiNi 0.5 Mn 1.5 O 4 ) or at least one of lithium iron phosphate (LiFePO 4 ).
  • the negative active material layer contains a negative active material, and a negative active material known in the art that can perform reversible deintercalation of active ions is used, which is not limited in this application.
  • a negative active material known in the art that can perform reversible deintercalation of active ions is used, which is not limited in this application.
  • it may include but is not limited to one of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, lithium titanate or other metals that can form an alloy with lithium, or Various combinations.
  • the graphite can be selected from one or a combination of artificial graphite, natural graphite and modified graphite;
  • the silicon-based material can be selected from one or more of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon alloys or Various combinations;
  • tin-based materials can be selected from one or a combination of elemental tin, tin oxide compounds, tin alloys, etc.
  • the isolation film 23 includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide or aramid.
  • polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene.
  • polyethylene and polypropylene have a good effect on improving short circuit and can improve the stability of the electrochemical device 100 through the shutdown effect.
  • the state of the electrolyte may be one or more of gel, solid and liquid.
  • the liquid electrolyte includes lithium salt and non-aqueous solvent.
  • the lithium salt is selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium perchlorate (LiClO 4 ), lithium tetraphenylborate (LiB(C 6 H 5 ) 4 ), lithium methanesulfonate (LiCH 3 SO 3 ), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ) , lithium bis(trifluoromethanesulfonyl)imide (LiN(SO 2 CF 3 ) 2 , lithium
  • the lithium salt is LiPF 6 because it can give high ionic conductivity and improve cycle characteristics.
  • the non-aqueous solvent can be Carbonate compounds, carboxylate compounds, ether compounds, nitrile compounds, other organic solvents or combinations thereof.
  • carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate ( DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), Vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-tris carbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2 carbonate - Difluoro
  • the negative electrode current collector 210 includes a negative electrode empty foil area 2101 , a negative electrode single-sided area 2102 and a negative electrode double-sided area 2103 that are connected in sequence. Please refer to FIGS. 3A and 3B together.
  • the first surface 210a of the negative electrode empty foil region 2101 is not provided with the first negative electrode active material layer 211, and the second surface 210b of the negative electrode empty foil region 2101 is not provided with the second negative electrode active material layer 212.
  • the first surface 210a of the negative electrode single-sided region 2102 is provided with the first negative electrode active material layer 211, and the second surface 210b of the negative electrode single-sided region 2102 is not provided with the second negative electrode active material layer 212.
  • the first surface 210a of the negative electrode double-sided region 2103 is provided with a first negative electrode active material layer 211, and the second surface 210b of the negative electrode double-sided region 2103 is provided with a second negative electrode active material layer 212. It can be understood that the distinction between the negative electrode empty foil area 2101, the negative electrode single-sided area 2102 and the negative electrode double-sided area 2103 is defined based on whether corresponding negative electrode active material layers are provided on the respective first surface 210a and second surface 210b.
  • the surfaces of the negative electrode empty foil region 2101 and the negative electrode single-sided region 2102 without the negative electrode active material layer must be completely exposed.
  • the first surface 210a and/or the second surface 210b of the negative electrode empty foil region 2101 may be provided with other functional layers (for example, a functional layer containing an insulating material; another example, a functional layer containing a conductive agent and an insulating material; or , a functional layer containing conductive agent and adhesive).
  • the second surface 210b of the negative electrode single-sided region 2102 may also be provided with other functional layers.
  • the negative electrode sheet 21 includes a negative electrode winding first layer 21 a , a negative electrode winding first arc 21 b , a negative electrode winding secondary layer 21 c , a negative electrode winding secondary arc 21 d , and a negative electrode coil connected in sequence.
  • the negative electrode is wound with three layers 21e, the negative electrode is wound with three arcs 21f, the negative electrode is wound with four layers 21g, and the negative electrode is wound with four arcs 21h.
  • the negative electrode winding first layer 21a, the negative electrode winding second layer 21c, the negative electrode winding third layer 21e, and the negative electrode winding fourth layer 21g are straight sections respectively; the negative electrode winding first arc 21b, the negative electrode winding second layer The arc 21d, the negative electrode winding three arcs 21f and the negative electrode winding four arcs 21h are respectively curved sections.
  • the negative electrode winding first layer 21a, the negative electrode winding second layer 21c, the negative electrode winding third layer 21e, and the negative electrode winding fourth layer 21g can also be curved sections respectively.
  • the negative electrode winding first layer 21a, the negative electrode winding first arc 21b, the negative electrode winding sub-layer 21c and the negative electrode winding sub-arc 21d constitute the negative electrode winding first turn formed after the negative electrode pole piece 21 is wound along the winding direction D. at least part of.
  • the three negative electrode winding layers 21e, the negative electrode winding three arcs 21f, the negative electrode winding four layers 21g and the negative electrode winding four arcs 21h constitute at least the negative electrode winding secondary turns formed after the negative electrode pole piece 21 is wound along the winding direction D. part.
  • one circle refers to starting from a certain point on the negative electrode piece 21 as the starting end, and arriving at another point along the winding direction D as the ending end.
  • the center is on a straight line, and the start end is between the end end and the center of the circle.
  • the first direction D 1 is also the direction from the negative electrode winding sub-layer 21 c to the negative electrode winding first layer 21 a.
  • the second direction D 2 is also the direction from the negative pole winding first arc 21 b to the negative pole winding secondary arc 21 d.
  • the negative electrode empty foil area 2101 is located on the negative electrode winding first layer 21a.
  • the negative electrode single-sided area 2102 is located at least on the negative electrode winding first layer 21a and the negative electrode winding sublayer 21c.
  • the negative electrode single-sided area 2102 is also located at the negative electrode winding first arc 21b.
  • the negative electrode single-sided area 2102 continuously extends from the negative electrode winding first layer 21a to the negative electrode winding first arc 21b and the negative electrode winding sub-layer 21c along the winding direction D.
  • the negative electrode single-sided region 2102 includes a starting end 2102a of the negative electrode single-sided region, and the starting end 2102a of the negative electrode single-sided region is located at the negative electrode winding first layer 21a.
  • the starting end 2102a of the negative electrode single-sided area refers to the part where the negative electrode single-sided area 2102 starts to be wound along the winding direction D, which is the interface position between the negative electrode empty foil area 2101 and the negative electrode single-sided area 2102.
  • the negative electrode tab 30 can be connected to the negative electrode empty foil area 2101.
  • the negative electrode tab 30 is connected to the first surface 210a of the negative electrode empty foil region 2101 facing the winding central axis O, and the negative electrode tab 30 is located on the negative electrode winding first layer 21a.
  • the negative electrode tab 30 can be welded to the negative electrode empty foil area 2101, thereby improving the connection reliability between the negative electrode tab 30 and the negative electrode empty foil area 2101.
  • the positive current collector 220 includes a positive double-sided region 2202 .
  • the third surface 220a of the positive electrode double-sided region 2202 is provided with a first positive electrode active material layer 221, and the fourth surface 220b of the positive electrode double-sided region 2202 is provided with a second positive electrode active material layer 222.
  • the positive electrode double-sided region 2202 is located on the side of the negative electrode winding sublayer 21 c away from the winding central axis O, and further extends along the winding direction D.
  • the positive electrode current collector 220 may also include a positive electrode empty foil area 2201, and the positive electrode empty foil area 2201 and the positive electrode double-sided area 2202 are connected in sequence along the winding direction D. It can be understood that the distinction between the positive electrode double-sided area 2202 and the positive electrode empty foil area 2201 is defined based on whether the corresponding positive electrode active material layer is provided on the respective third surface 220a and fourth surface 220b, which does not mean that the positive electrode The surface of the empty foil area 2201 that is not provided with the negative active material layer must be completely exposed. For example, other functional layers may be provided on the third surface 220a and/or the fourth surface 220b of the positive electrode empty foil region 2201.
  • the positive electrode sheet 22 includes a positive electrode winding first layer 22a, a positive electrode winding first arc 22b, a positive electrode winding secondary layer 22c and a positive electrode winding secondary arc 22d connected in sequence.
  • the positive electrode winding first layer 22a and the positive electrode winding sub-layer 22c are straight sections respectively; the positive electrode winding first arc 22b and the positive electrode winding secondary arc 22d are respectively curved sections.
  • the positive electrode winding first layer 22a and the positive electrode winding sub-layer 22c can also be curved sections respectively.
  • the positive electrode winding first layer 22a, the positive electrode winding first arc 22b, the positive electrode winding secondary layer 22c and the positive electrode winding secondary arc 22d constitute at least the positive electrode winding first turn formed after the positive electrode pole piece 22 is wound along the winding direction D. part.
  • the first winding turn of the positive electrode is located on the side away from the winding central axis O of the first winding turn of the negative electrode.
  • the positive electrode empty foil area 2201 can be located at the positive electrode winding first layer 22a and the positive electrode winding first arc 22b, and the positive electrode empty foil area 2201 located at the positive electrode winding first layer 22a can be separated from the negative electrode winding first layer through the isolation film 23.
  • the negative electrode empty foil area 2101 of layer 21a is opposite.
  • the positive electrode empty foil area 2201 includes a starting end 2201a of the positive electrode empty foil area.
  • the starting end 2201a of the positive electrode empty foil area refers to the portion starting from the head of the positive electrode piece 22 along the winding direction D.
  • the positive electrode double-sided region 2202 is located in the positive electrode winding sub-layer 22c and the positive electrode winding sub-arc 22d, and further extends along the winding direction D.
  • the positive electrode tab 40 may be connected to the positive electrode empty foil area 2201 located on the positive electrode winding first layer 22a.
  • the positive electrode tab 40 is connected to the fourth surface 220b of the positive electrode empty foil region 2201 away from the winding central axis O, and the positive electrode tab 40 is located on the positive electrode winding first layer 22a.
  • the positive electrode tab 40 can be welded to the positive electrode empty foil area 2201, thereby improving the connection reliability between the positive electrode tab 40 and the positive electrode empty foil area 2201.
  • the positive electrode empty foil area 2201 can also be removed to reduce the size of the electrode assembly 20 in the first direction D 1 .
  • the positive electrode tab 40 in the second direction D 2 , is between the negative electrode tab 30 and the negative electrode single-sided region 2102 located on the negative electrode winding first layer 21 a. That is, in the second direction D 2 , the positive electrode tab 40 is closer to the negative electrode single-sided region 2102 located on the negative electrode winding first layer 21 a than the negative electrode tab 30 . In this way, when the position of the positive electrode tab 40 is close to the negative electrode winding secondary arc 21d in the second direction D2 , the starting end 2201a of the positive electrode empty foil area pierces the isolation film 23 and mistakenly contacts the negative electrode winding secondary arc 21d and is short-circuited. possibility.
  • the positive double-sided region 2202 includes a positive double-sided region starting end 2202a.
  • the starting end 2202a of the positive electrode double-sided area refers to the part where the positive electrode double-sided area 2202 starts to be wound along the winding direction D, that is, the junction position of the positive electrode empty foil area 2201 and the positive electrode double-sided area 2202 (defined as passing through the positive electrode double-sided area).
  • the line starting from the area 2202a and extending in the first direction D 1 is the intersection line L 0 ). Since the positive electrode double-sided area 2202 is an area where the positive electrode active material is coated on both sides, the starting end 2202a of the positive electrode double-sided area is also the position where the thickness of the positive electrode sheet 22 changes in the winding direction D.
  • the starting end 2202a of the positive electrode double-sided region overlaps the negative electrode single-sided region 2102 located on the negative electrode winding first layer 21a.
  • the starting end 2202 a of the positive electrode double-sided region is separated from the starting end 2102 a of the negative electrode single-sided region.
  • the starting end 2202a of the positive electrode double-sided area and the starting end 2102a of the negative electrode single-sided area may just overlap and intersect when viewed from the third direction D3 .
  • Line L 0 passes through the starting end 2102a of the negative electrode single-sided region.
  • the negative electrode single-sided region 2102 is not only located on the negative electrode wound sub-layer 21c and opposite to the positive electrode double-sided region 2202 located on the positive electrode wound sub-layer 22c across the isolation film 23; moreover, the negative electrode single-sided region 2102 also spans It passes through the negative electrode winding first arc 21b and extends to the negative electrode winding first layer 21a.
  • the second negative active material layer 212 located on the negative single-sided region 2102 of the negative electrode winding first layer 21a can compensate for the thickness difference of the electrode assembly 20 on both sides of the starting end 2202a of the positive double-sided region in the first direction D1 , That is, the difference in thickness of the electrode assembly 20 on both sides of the boundary line L 0 is compensated, which is beneficial to improving the flatness of the electrochemical device 100 .
  • the present application also provides that the negative electrode piece 21 includes a first layer 51 containing an insulating material.
  • the first layer 51 is located on the negative electrode winding first layer 21a and extends from the second negative electrode active material layer 212 to the second surface 210b of the negative electrode empty foil region 2101.
  • the first layer 51 includes a first layer starting end 51a and a first layer ending end 51b that are oppositely arranged in the winding direction D.
  • the starting end 51a of the first layer is located on the negative electrode empty foil area 2101, and the ending end 51b of the first layer is located on the second negative electrode active material layer 212 and covers the starting end 2102a of the negative electrode single-sided area. Therefore, the first layer 51 can be used to fix the second negative electrode active material layer 212 located on the negative electrode single-sided area 2102 of the negative electrode winding first layer 21a, and reduce the negative electrode active material on this part of the second negative electrode active material layer 212 from separating from the negative electrode. Possibility of current collector 210.
  • the second negative electrode active material layer 212 and the first layer located on the negative electrode single-sided area 2102 of the negative electrode winding first layer 21a 51 can also compensate for the difference in thickness of the electrode assembly 20 at the position corresponding to the positive electrode tab 40 compared to other areas, which is beneficial to further improving the flatness of the electrochemical device 100 .
  • the positional relationship between the negative electrode single-sided region 2102 and the first layer 51 in the electrode assembly 20 can be determined through the following steps: (1) Discharging the electrochemical device 100 to 2.75V at 0.2C; (2) Configuring the resin The composition is prepared from a crystal glue resin matrix (such as epoxy resin), a catalyst and a curing agent in a certain proportion; (3) Pour the resin composition into the mold, and cut the casing 10 of the electrochemical device 100 After opening, place it in the mold at an angle to reduce the bubbles that may remain at the bottom of the electrochemical device 100, and then continue to slowly pour the resin composition so that the electrochemical device 100 is completely immersed in the resin composition, allowing the resin composition to pass through the shell.
  • a crystal glue resin matrix such as epoxy resin
  • a catalyst and a curing agent in a certain proportion
  • the incision of the body 10 slowly flows into the housing 10; (4) Level the electrochemical device 100, discharge excess bubbles, and then let it stand until the resin composition solidifies; (5) Along the direction perpendicular to the third direction D3 Cut the head of the electrochemical device 100 in cross-section and polish the cutting surface to obtain the cross-section of the electrochemical device 100; (6) Use an optical microscope to observe the above-mentioned cross-section of the electrochemical device 100 to determine the negative electrode single-sided area 2102 and the first The positional relationship of layer 51 in electrode assembly 20.
  • the material of the first layer 51 can be selected from polyvinylidene fluoride, modified polyvinylidene fluoride, polyacrylate, modified polyacrylate, modified polyethylene, modified polydiene, polycyclic Oxyethane, polyvinylidene fluoride, styrene-butadiene rubber, modified rubber, copolymer of vinylidene fluoride and hexafluoropropylene, butadiene, acrylonitrile, styrene, methyl methacrylate, butyl acrylate, Vinylpyrrolidone, isooctyl methacrylate, isooctyl acrylate, polyvinylidene fluoride, 9-octadecenenitrile, propyl propionate, ethyl propionate, N-methylpyrrolidone or 4-phenyl ring At least one insulating material in hexanone.
  • the first layer 51 can be single-sided tape or double-sided tape.
  • the first insulation layer 51 may also be a ceramic layer.
  • the ceramic layer includes a ceramic material including hafnium dioxide, strontium titanate, tin dioxide, cesium oxide, magnesium oxide, nickel oxide, calcium oxide, barium oxide, zinc oxide, zirconium oxide, yttrium oxide , at least one of aluminum oxide, titanium oxide, silicon dioxide, boehmite, magnesium hydroxide or aluminum hydroxide.
  • the first layer 51 may be a two-layer or multi-layer structure.
  • the first layer 51 may include a first base material layer 511 and a first adhesive layer 512 that are stacked.
  • the first layer 51 may be single-sided tape, and the first base material layer 511 is used to set and support the first adhesive layer 512 .
  • the first adhesive layer 512 is provided between the first base material layer 511 and the negative electrode winding first layer 21a.
  • the first adhesive layer 512 has adhesiveness, and the first layer 51 is adhered to the negative electrode winding first layer 21a through the first adhesive layer 512.
  • the materials of the first base material layer 511 and the first adhesive layer 512 are each independently selected from the above-mentioned insulating materials.
  • the adhesive material in the first adhesive layer 512 can be embedded in the second negative electrode active material layer 212 located in the negative electrode winding first layer 21a, thereby converting this part of the second negative electrode active material layer 212
  • the negative active materials in them are bonded together. In this way, the possibility that the negative active material of the portion of the second negative active material layer 212 separates from the negative current collector 210 can be further reduced.
  • the first layer 51 may also be double-sided tape.
  • the negative electrode single-sided area 2102 by arranging the negative electrode single-sided area 2102 to be located on the negative electrode winding first layer 21a and making the starting end 2202a of the positive electrode double-sided area overlap with the negative electrode single-sided area 2102 located on the negative electrode winding first layer 21a in the first direction D1 , At the same time, the first layer 51 is provided on the negative electrode winding first layer 21a, so that the flatness of the electrochemical device 100 is improved.
  • the formation splint first contacts the thicker part of the electrode assembly 20 (such as the position where the starting end 2202a of the positive electrode double-sided region is located, or the position where the positive electrode tab 40 is located) during the jig forming process, causing other parts of the electrode assembly 20 to be thinner And the possibility of under-pressure or even no pressure. It can be understood that when a certain position of the electrode assembly 20 is under insufficient or even no pressure, the interface contact between the positive electrode piece 22, the isolation film 23 and the negative electrode piece 21 at that position is not close, and the interface will become loose during the long-term charging and discharging process.
  • the present application can reduce the possibility of lithium precipitation caused by insufficient local pressure on the electrode assembly 20 during the formation of the clamp, and prolongs the service life of the electrochemical device 100 .
  • the starting end 2202 a of the positive electrode double-sided region can be set to overlap the first layer 51 .
  • the first layer 51 can also be used to further compensate for the thickness difference of the electrode assembly 20 on both sides of the starting end 2202a of the positive electrode double-sided region in the first direction D1 , which is beneficial to further improving the flatness of the electrochemical device 100.
  • the negative electrode single-sided region 2102 extends from the negative electrode winding first layer 21a to at least the negative electrode winding three arcs 21f, that is, the negative electrode single-sided area 2102 is at least located at the negative electrode winding first layer 21a, The negative electrode winding first arc 21b, the negative electrode winding secondary layer 21c, the negative electrode winding secondary arc 21d, the negative electrode winding three layers 21e and the negative electrode winding three arcs 21f.
  • the negative electrode single-sided region 2102 is located at the negative electrode winding first layer 21a, the negative electrode winding first arc 21b, the negative electrode winding sub-layer 21c, the negative electrode winding secondary arc 21d, the negative electrode winding third layer 21e and the negative electrode winding Three arcs 21f.
  • the negative electrode double-sided region 2103 is located on the fourth negative electrode winding layer 21g and further extends along the winding direction D. Compared with the situation where the negative electrode double-sided area is provided in the negative electrode winding secondary arc 21d, the negative electrode winding third layer 21e and the negative electrode winding third arc 21f, this application can reduce the usage of negative electrode active materials and can also increase the energy density.
  • the negative electrode double-sided region 2103 includes a negative electrode double-sided region starting end 2103a, and the negative electrode double-sided region starting end 2103a is located at the negative electrode winding fourth layer 21g.
  • the starting end 2103a of the negative electrode double-sided region refers to the part where the negative electrode double-sided region 2103 starts to be wound, that is, the junction position between the negative electrode single-sided region 2102 and the negative electrode double-sided region 2103.
  • the starting end 2103a of the negative electrode double-sided region can be set to exceed the starting end 2202a of the positive electrode double-sided region in the opposite direction of the winding direction D.
  • the positive electrode plate 22 further includes a second layer 52 including an insulating material.
  • the second layer 52 covers the starting end 2202a of the positive electrode double-sided region and is formed from the first positive electrode active material layer 221 or The second positive electrode active material layer 222 extends to the positive electrode empty foil region 2201 .
  • the second layer 52 extends from the second cathode active material layer 222 to the fourth surface 220b of the cathode empty foil region 2201 away from the winding center.
  • the second layer 52 includes a second layer starting end 52a and a second layer ending end 52b that are oppositely arranged in the winding direction D.
  • the starting end 52a of the second layer is located on the positive electrode empty foil area 2201, and the ending end 52b of the second layer is located on the second positive electrode active material layer 222.
  • the second layer 52 is used to insulate and protect the fourth surface 220b of the exposed positive electrode empty foil area 2201, reducing the possibility of short circuit between the positive electrode empty foil area 2201 and the negative electrode empty foil area 2101 due to mechanical abuse. , and also reduces the possibility that the positive electrode empty foil area 2201 is torn during mechanical abuse, and the torn positive electrode empty foil area 2201 pierces the isolation film 23 and mistakenly contacts the negative electrode empty foil area 2101 for a short circuit.
  • the second layer 52 covers part of the second positive electrode active material layer 222, the second layer 52 can also reduce the size of the area adjacent to the positive electrode double-sided area when the starting end 2103a of the negative electrode double-sided area does not exceed the starting end 2202a of the positive electrode double-sided area.
  • the lithium ions desorbed from part of the second positive electrode active material layer 222 at the starting end 2202a cannot be fully received by the first negative electrode active material layer 211, thereby reducing the possibility of excess lithium ions accumulating and lithium precipitation.
  • the material of the second layer 52 may be selected from polyvinylidene fluoride, modified polyvinylidene fluoride, polyacrylate, modified polyacrylate, modified polyethylene, modified polydiene, polycyclic Oxyethane, polyvinylidene fluoride, styrene-butadiene rubber, modified rubber, copolymer of vinylidene fluoride and hexafluoropropylene, butadiene, acrylonitrile, styrene, methyl methacrylate, butyl acrylate, Vinylpyrrolidone, isooctyl methacrylate, isooctyl acrylate, polyvinylidene fluoride, 9-octadecenenitrile, propyl propionate, ethyl propionate, N-methylpyrrolidone or 4-phenyl ring At least one of hexanone.
  • the second layer 52 can be single-sided tape or double-sided tape
  • the second layer 52 may be a two-layer or multi-layer structure.
  • the second layer 52 may include a stacked second base material layer 521 and a second adhesive layer 522.
  • the second layer 52 may be single-sided tape, and the second base material layer 521 is used to set and support the second adhesive layer 522 .
  • the second adhesive layer 522 is provided between the second base material layer 521 and the positive electrode empty foil area 2201 .
  • the second adhesive layer 522 has adhesiveness, and the second layer 52 is adhered to the positive electrode empty foil area 2201 through the second adhesive layer 522 .
  • the materials of the second base material layer 521 and the second adhesive layer 522 are each independently selected from the above-mentioned insulating materials.
  • the second layer 52 may also be double-sided tape.
  • the line passing through the starting end 2103a of the negative electrode double-sided region and extending along the first direction D 1 is defined as the first virtual line L 1
  • the line passing through the second layer termination end 52b and extending along the first direction D 1 is defined.
  • the second virtual line L 2 is the first virtual line L 1 in the second direction D 2 .
  • the first virtual line L 1 is closer to the negative electrode winding first arc 21 b than the second virtual line L 2
  • the second virtual line L 2 is closer to the winding arc than the first virtual line L 1 around the central axis O.
  • the boundary line L 0 is located between the first virtual line L 1 and the second virtual line L 2 .
  • the negative electrode piece 21 located between the first virtual line L 1 and the second virtual line L 2 may undergo lithium deposition because:
  • the thickness of the negative electrode piece 21 changes in the winding direction D from the negative electrode single-sided area 2102 to the negative electrode double-sided area 2103 (i.e., at the starting end 2103a of the negative electrode double-sided area), during the rolling process,
  • the portion of the first negative active material layer 211 or the second negative active material layer 212 adjacent to the starting end 2103a of the negative electrode double-sided region and located between the first virtual line L 1 and the second virtual line L 2 is susceptible to over-rolling or rolling. Incomplete impact.
  • roller pressing may cause the negative active material to have a high compaction density or even break, resulting in uneven film formation of the solid electrolyte interface film (SEI film) and the possibility of cycle deterioration; on the other hand, it may also lead to poor electrolyte infiltration and surface
  • SEI film solid electrolyte interface film
  • the impedance increases, leading to lithium precipitation.
  • Incomplete rolling may result in the part of the first negative active material layer 211 or the second negative active material layer 212 having a lower density and more pores, causing the part of the first negative active material layer 211 or the second negative active material layer 212 to
  • the demand for electrolyte also increases accordingly. After a long-term charge and discharge cycle, due to the rapid consumption of electrolyte near the first negative active material layer 211 or the second negative active material layer 212 in this part, local polarization increases, thus Lead to lithium precipitation.
  • the negative electrode piece 21 located between the first imaginary line L 1 and the second imaginary line L 2 is close to the corner of the electrode assembly 20 .
  • the thickness of the electrode assembly 20 at the corner is thin, and it is easy to receive insufficient or even no pressure during the fixture formation process, causing the interface contact between the positive electrode piece 22, the isolation film 23 and the negative electrode piece 21 at this position to be loose, and in the long term During the charge and discharge process, the interface contact continues to deteriorate, leading to lithium precipitation.
  • the starting end 2102a of the negative electrode single-sided region can be set between the first virtual line L 1 and the second virtual line L 2 .
  • the starting end 2202a of the positive electrode double-sided area overlaps the negative electrode single-sided area 2102 located on the negative electrode winding first layer 21a in the first direction D1, so in the second direction D2 , the first virtual line L1 and The distance between the second virtual line L 2 is L, the distance between the starting end 2102a of the negative electrode single-sided area and the first virtual line L 1 is a, and the distance between the starting end 2202a of the positive electrode double-sided area and the second virtual line L 2 is The distance is b, then a+b ⁇ L.
  • the electrode assembly 20 located between the first virtual line L 1 and the second virtual line L 2 can be filled with the second negative electrode active material layer 212 located on the negative electrode single-sided region 2102 of the negative electrode winding first layer 21 a.
  • Implement thickness compensation Since the first layer 51 is provided on the negative electrode winding first layer 21a, the electrode assembly 20 located between the first virtual line L1 and the second virtual line L2 can also be filled with the first layer 51 to achieve thickness compensation. Therefore, during the fixture formation process, the formation splint can tightly compact the electrode assembly 20 between the first virtual line L1 and the second virtual line L2 , thereby improving the contact interface between the positive electrode piece 22 and the negative electrode piece 21, Reduce the possibility of lithium precipitation.
  • the thickness H of the first layer 51 may be set to range from 1 ⁇ m to 50 ⁇ m.
  • the thickness range of the first layer 51 so that the difference in thickness between the electrode assembly 20 corresponding to the positive electrode tab 40 and the first imaginary line L 1 and the second imaginary line L 2 does not exceed 20 ⁇ m, This is beneficial to making the electrochemical device 100 flatter.
  • the manufacturing difficulty of the first layer 51 is also reduced.
  • the thickness H can be measured using a caliper or other suitable measuring tool, or the image of the above-mentioned cross-section of the electrochemical device 100 can also be collected and measured in the image.
  • the position of the negative electrode single-sided region 2102 can also be changed.
  • the negative electrode single-sided area 2102 can also be located only in the negative electrode winding first layer 21a, the negative electrode winding first arc 21b, the negative electrode winding sub-layer 21c, the negative electrode winding secondary arc 21d and the negative electrode winding third layer 21e.
  • the negative electrode double-sided area 2103 is located at the negative electrode winding third arc 21f and the negative electrode winding fourth layer 21g and further extends along the winding direction D.
  • the starting end 2103a of the negative electrode double-sided area is located at the negative electrode winding third arc 21f.
  • the negative electrode double-sided area 2103 is provided in the negative electrode winding three arcs 21f, it is beneficial to increase the thickness of the electrode assembly 20 at the corners. Therefore, during the fixture formation process, it is beneficial to improve the contact interface between the positive electrode piece 22 and the negative electrode piece 21 and reduce the possibility of lithium precipitation at the corners of the electrode assembly 20 .
  • the position of the starting end 2102a of the negative electrode single-sided region can also be changed.
  • the starting end 2102a of the negative electrode single-sided region may also be located on the side of the second virtual line L2 away from the first virtual line L1 in the second direction D2 . Therefore, there is a second negative active material layer 212 on the negative electrode empty foil region 2101 located on the side of the second imaginary line L 2 away from the first imaginary line L 1 in the second direction D 2 .
  • the electrode assembly 20 between the first virtual line L 1 and the second virtual line L 2 can also be filled with the negative electrode single-sided region 2102 located on the negative electrode winding first layer 21 a to achieve thickness compensation.
  • the second negative electrode active material layer 212 on the negative electrode empty foil area 2101 located on the side of the second virtual line L2 away from the first virtual line L1 in the second direction D2 can also compensate for the negative electrode tab 40 corresponding to
  • the difference between the thickness of the electrode assembly 20 and the thickness of the electrode assembly 20 on the side of the second imaginary line L 2 away from the first imaginary line L 1 is conducive to further improving the flatness of the electrochemical device 100 .
  • the positive electrode tab 40 in the first direction D 1 , is separated from the negative electrode single-sided region 2102 located on the negative electrode winding first layer 21 a. That is, in the first direction D 1 , the positive electrode tab 40 does not overlap with the negative electrode single-sided area 2102 located on the negative electrode winding first layer 21 a , thereby reducing the thickness increase of the electrode assembly 20 corresponding to the positive electrode tab 40 when the two overlap. possibility, thereby reducing the impact on the energy density of the electrochemical device 100 .
  • the first layer starting end 51a may be located on a side of the second virtual line L2 away from the first virtual line L1 in the second direction D2 , and the first layer ending end 51b It can coincide with the first virtual line L1 . Therefore, there is the first layer 51 on the negative electrode empty foil region 2101 located on the side of the second virtual line L2 away from the first virtual line L1 in the second direction D2 .
  • the first layer 51 located on the side of the second virtual line L 2 away from the first virtual line L 1 can also compensate the electrode assembly 20 corresponding to the positive electrode tab 40 and the second virtual line L 2 away from the first virtual line L
  • the thickness difference between the electrode assemblies 20 on one side of 1 is beneficial to further improving the flatness of the electrochemical device 100 .
  • the first layer 51 covers part of the second surface 210b of the negative electrode empty foil area 2101 at this time, it can be used to insulate and protect the exposed second surface 210b of the negative electrode empty foil area 2101, reducing the risk of negative electrode emptying.
  • the possibility of a short circuit between the foil area 2101 and the positive electrode empty foil area 2201 by mistake during mechanical abuse also reduces the possibility that the negative electrode empty foil area 2101 will be torn during mechanical abuse, and the torn negative electrode empty foil area 2101 will pierce the isolation film 23 And the possibility of short circuit due to mistaken contact with the positive electrode empty foil area 2201.
  • the first layer 51 is separated from the positive electrode tab 40 . That is, in the first direction D 1 , the first layer 51 does not overlap with the positive electrode tab 40 , which reduces the possibility that the thickness of the electrode assembly 20 corresponding to the positive electrode tab 40 will increase when the two overlap, thereby reducing the impact on the electricity. Effect of chemical device 100 energy density. As shown in FIG. 10 , in other embodiments, the first layer 51 may also overlap the positive electrode tab 40 in the first direction D 1 , thereby reducing the width of the first layer 50 in the first direction D 1 Cutting requirements and precision control requirements for the first layer 50 position.
  • the positive electrode tab 40 , the negative electrode tab 30 and the starting end 2201 a of the positive electrode empty foil region are separated in the first direction D 1 . That is, the positive electrode tab 40, the negative electrode tab 30 and the starting end 2201a of the positive electrode empty foil area do not overlap in the first direction D1 .
  • the positive electrode tab 40 and the negative electrode tab 30 do not overlap, thus reducing the possibility that the thickness of the electrode assembly 20 corresponding to the positive electrode tab 40 increases when they overlap, thereby increasing the energy density of the electrochemical device 100 .
  • the positive electrode tab 40 does not overlap with the starting end 2201a of the positive electrode empty foil area, thus reducing the possibility that the positive electrode tab 40 exceeds the positive electrode empty foil area 2201 during welding, and also reducing the accuracy requirements for the welding position of the positive electrode tab 40.
  • the first layer starting end 51 a when viewed from the third direction D 3 , may also coincide with the second virtual line L 2 . That is, the first layer 51 does not exceed the range defined between the first virtual line L 1 and the second virtual line L 2 .
  • the first layer termination end 51 b may also be located on the side of the first virtual line L 1 away from the second virtual line L 2 in the second direction D 2 . Therefore, part of the first layer 51 is provided at the corners of the electrode assembly 20 . In this way, the first layer 51 can also increase the thickness of the electrode assembly 20 at the corners. Therefore, during the fixture formation process, it is beneficial to improve the contact interface between the positive electrode piece 22 and the negative electrode piece 21 between the first virtual line L 1 and the second virtual line L 2 and reduce the possibility of lithium precipitation at the corners of the electrode assembly 20 .
  • the second layer 52 extends to the positive winding first layer 22 a and overlaps the positive tab 40 in the first direction D 1 .
  • the second layer 52 is also used to cover the burrs or welding marks on the surface of the positive electrode tab 40 (the burrs can be produced when cutting the positive electrode tab 40, and the welding marks can be produced when the positive electrode tab 40 is welded to the positive electrode empty foil area 2201 , but this application is not limited), reduce the possibility of the above-mentioned burrs or solder marks piercing the isolation film 23, and extend the service life of the electrochemical device 100.
  • the positive electrode plate 22 further includes a fourth layer 54 including an insulating material.
  • the fourth layer 54 covers a portion of the first positive electrode active material layer 221 adjacent to the starting end 2202a of the positive electrode double-sided region, and extends from the first positive electrode active material layer 221 to the third surface of the positive electrode empty foil region 2201 toward the winding central axis O 220a on.
  • the fourth layer 54 includes a fourth layer starting end 54a and a fourth layer ending end 54b that are oppositely arranged in the winding direction D.
  • the starting end 54a of the fourth layer is located on the positive electrode empty foil area 2201, and the ending end 54b of the fourth layer is located on the first positive electrode active material layer 221.
  • the fourth layer 54 is used to insulate and protect the third surface 220a of the exposed positive electrode empty foil area 2201, reducing the possibility of short circuit between the positive electrode empty foil area 2201 and the negative electrode empty foil area 2101 due to mechanical abuse. , and also reduces the possibility that the positive electrode empty foil area 2201 is torn during mechanical abuse, and the torn positive electrode empty foil area 2201 pierces the isolation film 23 and mistakenly contacts the negative electrode empty foil area 2101 for a short circuit.
  • the fourth layer termination end 54b is located between the first virtual line L1 and the second virtual line L2 . Therefore, along the winding direction D, the end end 52b of the second layer exceeds the end end 54b of the fourth layer.
  • the material of the fourth layer 54 can be selected from polyvinylidene fluoride, modified polyvinylidene fluoride, polyacrylate, modified polyacrylate, modified polyethylene, modified polydiene, polyethylene oxide, Polyvinylidene fluoride, styrene-butadiene rubber, modified rubber, copolymer of vinylidene fluoride and hexafluoropropylene, butadiene, acrylonitrile, styrene, methyl methacrylate, butyl acrylate, vinylpyrrolidone, At least one of isooctyl methacrylate, isooctyl acrylate, polyvinylidene fluoride, 9-octadecenenitrile, propyl propionate, ethyl propionate, N-methylpyrrolidone or 4-phenylcyclohexanone A sort of.
  • the fourth layer 54 can be single-sided tape or double-sided tape. In other embodiments
  • the fourth layer 54 may be a two-layer or multi-layer structure.
  • the fourth layer 54 may include a stacked fourth base material layer 541 and a fourth adhesive layer 542 .
  • the fourth layer 54 may be single-sided tape, and the fourth base material layer 541 is used to set and support the fourth adhesive layer 542 .
  • the fourth adhesive layer 542 is provided between the fourth base material layer 541 and the positive electrode empty foil area 2201 .
  • the fourth adhesive layer 542 has adhesiveness, and the fourth layer 54 is adhered to the positive electrode empty foil area 2201 through the fourth adhesive layer 542 .
  • the materials of the fourth base material layer 541 and the fourth adhesive layer 542 are each independently selected from the above-mentioned insulating materials.
  • the fourth layer 54 may also be double-sided tape.
  • the fourth layer 54 may not cover the portion of the first positive active material layer 221 adjacent to the starting end 2202a of the positive double-sided region.
  • the fourth layer 54 can also be omitted.
  • the electrochemical device 100 further includes a third layer 53 including an insulating material.
  • the third layer 53 is provided on the second surface 210b of the negative electrode empty foil area 2101 away from the winding central axis O. In the first direction D 1 , the third layer 53 overlaps the negative electrode tab 30 and the starting end 2201 a of the positive electrode empty foil area. Therefore, the third layer 53 can cover the welding marks or burrs of the negative electrode tab 30, and is also used to cover the starting end 2201a of the positive electrode empty foil area, reducing the possibility of a short circuit between the positive electrode empty foil area 2201 and the negative electrode empty foil area 2101. .
  • the material of the third layer 53 can be selected from polyvinylidene fluoride, modified polyvinylidene fluoride, polyacrylate, modified polyacrylate, modified polyethylene, modified polydiene, polyethylene oxide, Polyvinylidene fluoride, styrene-butadiene rubber, modified rubber, copolymer of vinylidene fluoride and hexafluoropropylene, butadiene, acrylonitrile, styrene, methyl methacrylate, butyl acrylate, vinylpyrrolidone, At least one of isooctyl methacrylate, isooctyl acrylate, polyvinylidene fluoride, 9-octadecenenitrile, propyl propionate, ethyl propionate, N-methylpyrrolidone or 4-phenylcyclohexanone A sort of.
  • the third layer 53 can be single-sided tape or double-sided tape. In other embodiment
  • the third layer 53 may be a two-layer or multi-layer structure.
  • the third layer 53 may include a stacked third base material layer 531 and a third adhesive layer 532 .
  • the third layer 53 may be single-sided tape, and the third base material layer 531 is used to set and support the third adhesive layer 532 .
  • the third adhesive layer 532 is provided between the third base material layer 531 and the negative electrode empty foil area 2101 .
  • the third adhesive layer 532 has adhesiveness, and the third layer 53 is adhered to the negative electrode empty foil area 2101 through the third adhesive layer 532 .
  • the materials of the third base material layer 531 and the third adhesive layer 532 are each independently selected from the above-mentioned insulating materials.
  • the third layer 53 may also be double-sided tape.
  • the negative electrode plate 21 further includes a fifth layer 55 including an insulating material, and the fifth layer 55 is provided on the negative electrode winding secondary arc 21d.
  • the fifth layer 55 may be disposed on the first surface 210a of the negative electrode single-sided area 2102 located at the negative electrode winding sub-arc 21d.
  • the fifth layer 55 can increase the thickness of the negative electrode winding secondary arc 21d. In this way, the fifth layer 55 can increase the thickness of the corner of the electrode assembly 20.
  • the fifth layer 55 is also used to support the negative electrode winding sub-arc 21d and reduce the possibility that the negative electrode tab 21 will crack due to a too small curvature radius at the negative electrode winding sub-arc 21d.
  • the material of the fifth layer 55 can be selected from polyvinylidene fluoride, modified polyvinylidene fluoride, polyacrylate, modified polyacrylate, modified polyethylene, modified polydiene, polyethylene oxide, Polyvinylidene fluoride, styrene-butadiene rubber, modified rubber, copolymer of vinylidene fluoride and hexafluoropropylene, butadiene, acrylonitrile, styrene, methyl methacrylate, butyl acrylate, vinylpyrrolidone, At least one of isooctyl methacrylate, isooctyl acrylate, polyvinylidene fluoride, 9-octadecenenitrile, propyl propionate, ethyl propionate, N-methylpyrrolidone or 4-phenylcyclohexanone A sort of.
  • the fifth layer 55 can be single-sided tape or double-sided tape. In other embodiment
  • the fifth layer 55 may be a two-layer or multi-layer structure.
  • the fifth layer 55 may include a stacked fifth base material layer 551 and a fifth adhesive layer 552 .
  • the fifth layer 55 may be single-sided tape, and the fifth base material layer 551 is used to set and support the fifth adhesive layer 552 .
  • the fifth adhesive layer 552 is provided between the fifth base material layer 551 and the negative electrode single-sided region 2102 .
  • the fifth adhesive layer 552 has adhesiveness, and the fifth layer 55 is adhered to the negative electrode single-sided region 2102 through the fifth adhesive layer 552 .
  • the materials of the fifth base material layer 551 and the fifth adhesive layer 552 are each independently selected from the above-mentioned insulating materials.
  • the fifth layer 55 may also be double-sided tape.
  • the kinetic properties of the negative electrode piece 21 can also be improved to further reduce the possibility of lithium precipitation in the negative electrode piece 21.
  • the first negative active material layer 211 includes a first negative active material, and the first negative active material includes graphite.
  • the X-ray diffraction pattern of the first negative active material layer 211 includes a 004 diffraction peak and a 110 diffraction peak.
  • the ratio of the peak area of the 004 diffraction peak to the peak area of the 110 diffraction peak is the orientation index (ie, OI value) of the first negative active material layer 211, and the OI value ranges from 5.0 to 20.0.
  • the OI value can be used to characterize the anisotropy of the negative active material layer.
  • the lower limit of the OI value the possibility of the negative active material easily falling off during the production process of the negative electrode piece is reduced.
  • the OI value ranges from 5.0 to 13.0, thereby further improving the dynamic performance of the first negative active material layer 211 and reducing the possibility of lithium evolution.
  • the 004 diffraction peak and the 110 diffraction peak in the X-ray diffraction pattern of the negative active material were tested in accordance with the Machinery Industry Standard of the People's Republic of China JB/T4220-2011 "Method for Determination of Lattice Parameters of Artificial Graphite".
  • the test conditions are as follows: use dimethyl carbonate (DMC) to clean the negative active material and dry it; X-rays use CuK ⁇ radiation, and the CuK ⁇ radiation is removed by a filter or monochromator; when recording the 004 diffraction peak, the scanning range of the diffraction angle 2 ⁇ is 53° to 57°. When recording the 110 diffraction peak, the scanning range of the diffraction angle 2 ⁇ is 75° to 79°; then, calculate the ratio of the peak area obtained from the 004 diffraction peak to the peak area obtained from the 110 diffraction peak, and this ratio is the OI value.
  • the second negative active material layer 212 includes a second negative active material and the first negative active material includes graphite.
  • the OI value of the second negative electrode active material layer 212 can also be set to a range of 5.0 to 20.0, thereby improving the dynamic performance of the second negative electrode active material layer 212 and reducing the possibility of lithium precipitation in the second negative electrode active material layer 212 .
  • the shift range in the Raman spectrum of the first negative active material layer is 1255 cm -1 ⁇ 1355 cm -1 and 1575 cm -1 ⁇
  • the peaks at 1600 cm -1 are D peak and G peak respectively, and the intensity ratio of D peak and G peak ranges from 0.05 to 0.80.
  • the peak in the Raman spectrum of the first negative active material layer with a displacement range of 1255cm -1 ⁇ 1355cm -1 represents the lattice defects of carbon atoms.
  • the intensity ratio of D peak and G peak can be used to characterize the surface defects of the negative active material. The higher the intensity ratio between D peak and G peak, it indicates that the surface defects of the negative active material are higher, which is beneficial to increasing the contact area between the negative active material and the electrolyte, and is beneficial to the infiltration of the electrolyte.
  • the negative active material Surface defects can also increase the channels for ion embedding, which is beneficial to ion transfer.
  • this application increases the intensity ratio of the D peak and the G peak so that the negative active material layer has an appropriate amount of surface defects, thereby improving the dynamic performance of the first negative active material layer 211 and further reducing the possibility of lithium precipitation.
  • the defects may include at least one of point defects caused by the introduction of heteroatoms into the crystal structure of the negative electrode active material, hole defects caused by partial atom deletion, or defects caused by lattice dislocation.
  • the intensity ratio of the D peak and the G peak ranges from 0.30 to 0.80, thereby further reducing the possibility of lithium evolution.
  • the test method for the intensity ratio of D peak and G peak is as follows: select an area of 100 ⁇ m ⁇ 100 ⁇ m on the negative active material layer, and use a laser microscopy confocal Raman spectrometer (Raman, HR Evolution, HORIBA Scientific Instrument Division ) Scan the negative active materials in this area.
  • the laser wavelength of the Raman spectrometer can be in the range of 532nm to 785nm to obtain the D peak and G peak of all negative active materials in this area.
  • the intensity of the D peak and G peak of each particle is recorded as I D and I G respectively.
  • the frequency of I D /I G is counted with a step size of 0.02 to obtain a normal distribution diagram. These particles are counted and the frequency of I D /I G is calculated. mean and variance.
  • the intensity ratio of the D peak and the G peak in the second negative active material can also be set to a range of 0.05 to 0.80, thereby improving the The dynamic properties of the second negative electrode active material layer 212 reduce the possibility of lithium precipitation in the second negative electrode active material layer 212 .
  • the concentration of the lithium salt in the electrolyte ranges from 0.5 mol/L to 2.5 mol/L.
  • the lithium salt is dissolved in the solvent system and ionized, partially forming solvated lithium ions and corresponding anion groups, providing ionic conductivity. Therefore, by increasing the concentration of lithium salt in the electrolyte, this application is conducive to increasing the conductivity of the electrolyte, improving the dynamic performance of the electrochemical device 100, and further reducing the possibility of lithium precipitation. At the same time, by setting the upper limit of the lithium salt concentration, the possibility that excessive lithium salt concentration may cause difficulty in dissolution or crystallization during low-temperature storage after dissolution is reduced.
  • the concentration of the lithium salt in the electrolyte ranges from 1.0 mol/L to 2.5 mol/L, thereby further reducing the possibility of lithium evolution.
  • the concentration of lithium salt in the electrolyte is measured using an ion chromatograph.
  • electrochemical device 100 is exemplified by a lithium-ion battery, the present application is also applicable to other suitable electrochemical devices.
  • electrochemical device 100 includes any device that can undergo electrochemical reactions, such as all kinds of primary batteries. , secondary batteries, fuel cells, solar cells or capacitors.
  • the electrochemical device 100 may be a lithium secondary battery, including lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries and lithium ion polymer secondary batteries.
  • an embodiment of the present application further provides an electronic device 1 , including the above-mentioned electrochemical device 100 .
  • the electronic device 1 is powered by the above-mentioned electrochemical device 100, and the possibility of lithium precipitation in the electrochemical device 100 is reduced, thereby maintaining a longer service life.
  • the electronic device 1 of the present application may be, but is not limited to, a notebook computer, a pen input computer, a mobile computer, an e-book player, a portable telephone, a portable fax machine, a portable copier, a portable printer, a head-mounted Stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles , bicycles, lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the performance of the electrochemical device provided by this application is described below through specific examples and comparative examples.
  • the electrochemical device is a lithium-ion soft pack battery as an example and the specific preparation process and testing method are combined to describe this application.
  • the preparation method described in this application is only an example, and any other suitable preparation methods are used. Methods are within the scope of this application.
  • Preparation of the negative electrode sheet 21 Mix the negative active materials artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) in a weight ratio of 96:1.5:2.5, add deionized water as the solvent, and prepare it to a weight percentage into a 70wt% slurry and stir evenly.
  • the slurry is evenly coated on a surface of a copper foil with a thickness of 10 ⁇ m, and dried at 110° C. to obtain a first negative active material layer 211 with a thickness of 150 ⁇ m.
  • Repeat the above steps on the other surface of the copper foil to obtain a second negative active material layer 212 with a thickness of 150 ⁇ m.
  • the negative electrode tab 30 is welded to the negative electrode empty foil area 2101 of the negative electrode piece 21, and the first layer 51 is covered on the starting end 2102a of the negative electrode single-sided area.
  • the first layer 51 extends from the first negative electrode active material layer 211 to the negative electrode cavity.
  • the material of the negative electrode tab 30 is nickel (Ni), the material of the first layer 51 is polyvinylidene fluoride, and the thickness of the first layer 51 is 11 ⁇ m.
  • the OI values of the first negative active material layer 211 and the second negative active material layer 212 are both 15.0, and the D peak and G peak in the Raman spectra of the first negative active material layer 211 and the second negative active material layer 212
  • the intensity ratios are all 0.20.
  • Preparation of the positive electrode sheet 22 Mix the positive active materials lithium cobalt oxide (LiCoO 2 ), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.0:1.5, and add N-methyl NMP was used as the solvent to prepare a slurry with a solid content of 75wt%, and stirred evenly. The slurry is evenly coated on a surface of an aluminum foil with a thickness of 12 ⁇ m, and dried at 90° C. to obtain a first positive electrode active material layer 221 with a thickness of 100 ⁇ m. Repeat the above steps on the other surface of the aluminum foil to obtain a second cathode active material layer 222 with a thickness of 100 ⁇ m. On the positive electrode empty foil area 2101 of the positive electrode piece 22, there is a positive electrode tab 40, and the material of the positive electrode tab 40 is aluminum (Al).
  • LiCoO 2 lithium cobalt oxide
  • Super P conductive carbon black
  • PVDF polyvinylid
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the negative electrode piece 21, the isolation film 23 and the positive electrode piece 22 are stacked and wound in sequence to obtain the electrode assembly 20.
  • the isolation film 23 is made of a polyethylene (PE) film with a thickness of 15 ⁇ m.
  • PE polyethylene
  • the negative electrode single-sided area 2102 extends from the negative electrode winding first layer 21a to the negative electrode winding three arcs 21f along the winding direction D, and the starting end 2102a of the negative electrode single-sided area is located at the first between virtual line L 1 and second virtual line L 2 .
  • the starting end 2202a of the positive electrode double-sided region overlaps the negative electrode single-sided region 2102 located on the negative electrode winding first layer 21a.
  • the first layer 51 is located on the negative electrode winding first layer 21a and extends from the first negative electrode active material layer 211 to the second surface 210b of the negative electrode empty foil region 2101.
  • the first layer starting end 51a is located on the side of the second virtual line L2 away from the first virtual line L1 in the second direction D2 .
  • the first layer 51 does not overlap the positive electrode tab 40 .
  • Preparation of lithium-ion battery Place the punched aluminum plastic film (thickness: 150 ⁇ m) in the assembly fixture with the pit surface facing upward, and place the electrode assembly 20 in the pit. Inject electrolyte into the pit of the aluminum-plastic film, and lead the positive electrode tab 40 and the negative electrode tab 30 out of the aluminum-plastic film. It is then chemically formed and packaged to obtain a lithium-ion battery with a size of 92.21mm ⁇ 66.68mm ⁇ 5.099mm and a capacity of 5900mAh.
  • Embodiment 1 The difference from Embodiment 1 is that the negative electrode single-sided area 2102 is only located in the negative electrode winding first layer 21a, the negative electrode winding first arc 21b, the negative electrode winding secondary layer 21c, the negative electrode winding secondary arc 21d and the negative electrode winding third layer 21e .
  • the negative electrode single-sided area 2102 extends from the negative electrode winding sub-layer 21c to the negative electrode winding three arcs 21f along the winding direction D. That is, the negative electrode single-sided area 2102 is not located at The negative electrode winding first layer 21a. Also omit the first layer 51.
  • Embodiment 1 The difference from Embodiment 1 is that in the first direction D1 , the starting end 2202a of the positive electrode double-sided region does not overlap with the negative electrode single-sided region 2102 located on the negative electrode winding first layer 21a. Also omit the first layer 51.
  • Example 1 and Comparative Examples 1-2 were respectively subjected to an initial energy density test and a lithium evolution test, and then the thickness of the electrode assembly 20 between the first virtual line L1 and the second virtual line L2 was measured. The difference in thickness of the electrode assembly 20 corresponds to the positive electrode tab 40 .
  • the corresponding test results are recorded in Table 1.
  • the test steps for lithium precipitation include: (1) Place the battery in a constant temperature box at 25°C ⁇ 2°C for 2 hours; (2) Charge the battery, specifically: charge at 1.3C constant current to 4.1V, constant voltage Discharge to 1.0C, let stand for 5min, charge with constant current at 1.0C to 4.2V, discharge with constant voltage to 0.7C, let stand for 5min, charge with constant current at 0.7C to 4.3V, discharge with constant voltage to 0.4C, let stand for 5min, 0.4 C charge with constant current to 4.45V, discharge with constant voltage to 0.025C, and let stand for 5 minutes; (3) Discharge the battery, specifically discharge with constant current of 0.5C to 3.0V.
  • the degree of lithium precipitation is divided into slight lithium precipitation, moderate lithium precipitation and severe lithium precipitation. Slight lithium precipitation means that the lithium precipitation area is less than 0.5% of the entire area of the negative electrode piece 21. Moderate lithium precipitation means that the lithium precipitation area is 0.5% to 5.0% of the entire area of the negative electrode piece 21. Severe lithium precipitation means that the lithium precipitation area is larger than the negative electrode. 5.0% of the overall area of the pole piece 21 .
  • Embodiment 1-2 sets the negative electrode single-sided area 2102 at the negative electrode winding first layer 21a and makes the positive electrode double-sided area starting end 2202a in the first direction D1 It overlaps the negative electrode single-sided area 2102 located on the negative electrode winding first layer 21a, and at the same time, the first layer 51 is disposed on the negative electrode winding first layer 21a, so that the electrode between the first virtual line L 1 and the second virtual line L 2
  • the component 20 is filled, so the difference in the thickness of the electrode component 20 between the first imaginary line L 1 and the second imaginary line L 2 and the thickness of the electrode component 20 corresponding to the positive electrode tab 40 is reduced, that is, the flatness of the battery is improved , so the battery does not produce lithium.
  • Embodiment 1 The difference from Embodiment 1 is that the first layer 51 does not exceed the range defined between the first virtual line L 1 and the second virtual line L 2 .
  • Embodiment 1 The difference from Embodiment 1 is that in the first direction D 1 , the first layer 51 overlaps the positive electrode tab 40 .
  • Embodiment 1 The difference from Embodiment 1 is that the starting end 2102a of the negative electrode single-sided region is located on the side of the second virtual line L2 away from the first virtual line L1 .
  • the difference from Embodiment 1 is that the first layer termination end 51b is located on the side of the first virtual line L1 away from the second virtual line L2 in the second direction D2 .
  • Embodiment 1 The difference from Embodiment 1 is that the thickness of the first layer 51 is different.
  • the thickness of the electrode assembly 20 corresponding to the positive electrode tab 40 is consistent with the first virtual line L 1 and the second The thickness difference of the electrode assembly 20 between the virtual lines L 2 increases, so the flatness of the batteries in Examples 7-8 is reduced, and lithium deposition occurs in the batteries.
  • the thickness difference exceeds 20 ⁇ m, so slight lithium precipitation occurs after 500 cycles, and slight lithium precipitation occurs after 1000 cycles.
  • Examples 9-26 were further designed to improve the dynamic performance of the battery.
  • the difference between Examples 9-26 and Example 4 lies in the OI value, the intensity ratio of D peak and G peak, or the lithium salt concentration value.
  • Example 4 comparing Example 4 and Examples 9 to 13, it can be seen that when the OI value is set to 5.0 to 20.0, better 500 cycle and 1000 cycle performance can be obtained; when the OI value is further set to 5.0 to 13, Better 1000 cycle performance can be obtained. Comparing Example 4 and Examples 14 to 20, it can be seen that when the value of I D /I G is set to 0.05 to 0.80, better 500 cycle and 1000 cycle performance can be obtained; when the value of I D /I G is further set, Better 1000 cycle performance can be obtained with values from 0.30 to 0.80.

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Abstract

一种电化学装置，包括电极组件。电极组件包括负极极片和正极极片。负极极片包括第一负极活性材料层、负极集流体、第二负极活性材料层和第一层。正极极片包括第一正极活性材料层、正极集流体和第二正极活性材料层。负极极片包括负极卷绕首层和负极卷绕次层。负极集流体的负极单面区至少位于负极卷绕首层和负极卷绕次层。正极集流体的正极双面区位于负极卷绕次层背离卷绕中心轴的一侧。正极双面区包括正极双面区起始端。在第一方向上，正极双面区起始端与位于负极卷绕首层的负极单面区重叠。第一层位于负极卷绕首层且从第一负极活性材料层上延伸至负极空箔区上。还提供一种电子装置。本申请可降低析锂可能性，提高使用寿命。

Description

电化学装置以及电子装置 技术领域
本申请涉及储能装置领域，尤其是涉及一种电化学装置和电子装置。
背景技术
电化学装置(如电池)在电子移动设备、电动工具及电动汽车等电子产品中有着广泛使用。在经过长期的充放电循环后，电化学装置的负极极片表面会析出锂而形成锂枝晶，从而影响电化学装置的使用寿命。
发明内容
本申请提供一种能够降低负极极片析锂可能性的电化学装置。
另，本申请还提供一种具有上述电化学装置的电子装置。
本申请第一方面提供一种电化学装置，包括电极组件。电极组件包括层叠卷绕的负极极片和正极极片。负极极片包括依次层叠的第一负极活性材料层、负极集流体和第二负极活性材料层，第一负极活性材料层相较于第二负极活性材料层更靠近卷绕中心轴。正极极片包括依次层叠的第一正极活性材料层、正极集流体和第二正极活性材料层，第一正极活性材料层相较于第二正极活性材料层更靠近卷绕中心轴。沿卷绕方向，负极集流体包括依次连接的负极空箔区、负极单面区和负极双面区。负极极片包括负极卷绕首层和负极卷绕次层。负极单面区设有第二负极活性材料层，负极单面区至少位于负极卷绕首层和负极卷绕次层。正极集流体包括正极双面区，正极双面区位于负极卷绕次层背离卷绕中心轴的一侧。正极双面区包括正极双面区起始端。在第一方向上，正极双面区起始端与位于负极卷绕首层的负极单面区重叠，第一方向为负极卷绕次层至负极卷绕首层的方向。负极极片还包括包含绝缘材料的第一层，第一层位于负极卷绕首层且从第一负极活性材料层上延伸至负极空箔区上。
本申请通过设置负极单面区设于负极卷绕首层且使在第一方向上正极双面区起始端与位于负极卷绕首层的负极单面区重叠，同时在负极卷绕首层上设置第一层，使得电化学装置的平整性提高。因此， 可减小夹具化成工艺中因化成夹板首先接触电极组件较厚处导致电极组件其它位置由于较薄而受压不足甚至不受压的可能性，从而降低了析锂的风险，延长电化学装置的使用寿命。第一层还可用于固定位于负极卷绕首层的负极单面区上的第二负极活性材料层，减小该部分第二负极活性材料层上的负极活性材料脱落的可能性。
在一些实施例中，在第一方向上，正极双面区起始端与第一层重叠。如此，第一层可在第一方向上进一步补偿电极组件于正极双面区起始端两侧的厚度差异，有利于提高电化学装置的平整度。
在一些实施例中，正极集流体还包括正极空箔区，正极空箔区和正极双面区沿卷绕方向依次连接。正极极片包括正极卷绕首层和正极卷绕次层，正极双面区位于正极卷绕次层。
在一些实施例中，负极极片还包括负极卷绕首弧、负极卷绕次弧、负极卷绕三层、负极卷绕三弧和负极卷绕四层。沿卷绕方向，负极卷绕首层、负极卷绕首弧、负极卷绕次层、负极卷绕次弧、负极卷绕三层、负极卷绕三弧和负极卷绕四层依次连接。负极单面区从负极卷绕首层至少延伸至负极卷绕三弧。负极双面区包括负极双面区起始端，负极双面区起始端位于负极卷绕四层。负极卷绕首弧至负极卷绕次弧的方向为第二方向，第一方向垂直于第二方向。与第一方向和第二方向均垂直的方向为第三方向。相较于在负极卷绕次弧、负极卷绕三层和负极卷绕三弧设置负极双面区的情况，本申请可减少负极活性材料的使用量，也可以提高能量密度。
在一些实施例中，正极极片还包括包含绝缘材料的第二层，第二层从第一正极活性材料层或第二正极活性材料层上延伸至正极空箔区上。第二层包括在卷绕方向上相对设置的第二层起始端和第二层终止端，第二层起始端位于正极空箔区。经过负极双面区起始端且沿第一方向延伸的线为第一虚拟线，经过第二层终止端且沿第一方向延伸的线为第二虚拟线。在第二方向上，第一虚拟线相较于第二虚拟线更靠近负极卷绕首弧。负极单面区包括负极单面区起始端。从第三方向观察，负极单面区起始端位于第一虚拟线和第二虚拟线之间，或负极单面区起始端在第二方向上位于第二虚拟线背离第一虚拟线的一侧。因此，可使得第一虚拟线和第二虚拟线之间的电极组件可被位于负极卷绕首层的负极单面区上的第二负极活性材料层填充以实现厚度补偿，也可被第一层能填充以实现厚度补偿。因此，可使得在夹具化成工艺中化成夹板能够紧密压实第一虚拟线和第二虚拟线之间的区域，改善正极极片和负极极片的接触界面，降低析锂的可能性。
在一些实施例中，电化学装置还包括正极极耳。正极极耳连接于正极空箔区的背离卷绕中心轴的表面，正极极耳位于正极卷绕首层。第二层延伸至正极卷绕首层并在第一方向上与正极极耳重叠。因此，第二层可用于覆盖正极极耳表面的毛刺或焊印，减小上述毛刺或焊印刺穿隔离膜并与负极极片误接触短路的可能性，延长电化学装置的使用寿命。
在一些实施例中，正极极耳与位于负极卷绕首层的负极单面区相离。因此，减小了二者重叠时对应于正极极耳的电极组件厚度增加的可能性，从而可提升电化学装置的能量密度。
在一些实施例中，电化学装置还包括负极极耳和包含绝缘材料的第三层。负极极耳连接于负极空箔区的朝向卷绕中心轴的表面，负极极耳位于负极卷绕首层。正极空箔区包括正极空箔区起始端。第三层设于负极空箔区背离卷绕中心轴的表面。在第一方向上，第三层与负极极耳和正极空箔区起始端重叠。第三层可用于覆盖负极极耳的焊印或毛刺，而且还用于覆盖正极空箔区起始端，减小正极空箔区和负极空箔区误接触短路的可能性。
在一些实施例中，正极极耳、负极极耳和正极空箔区起始端在第一方向上相离。正极极耳与负极极耳在第一方向上相离，因此减小了二者重叠时对应于正极极耳的电极组件厚度增加的可能性，从而减小了对电化学装置能量密度的影响。正极极耳与正极空箔区起始端在第一方向上相离，因此减小了焊接时正极极耳超出正极空箔区的可能性，也减小了对正极极耳焊接位置的精度要求。
在一些实施例中，第二层设于正极空箔区背离卷绕中心轴的表面，第二层从第二正极活性材料层上延伸至正极空箔区上。第二层用于对裸露的正极空箔区表面起到绝缘保护的作用，减小了正极空箔区在机械滥用时与负极空箔区误接触短路的可能性，也减小了机械滥用时正极空箔区发生撕裂后刺穿隔离膜与负极空箔区误接触短路的可能性。而且，第二层也可以减小当负极双面区起始端未超出正极双面区起始端时析锂的可能性。
在一些实施例中，正极极片还包括包含绝缘材料的第四层。第四层设于正极空箔区朝向卷绕中心轴的表面，第四层从第一正极活性材料层上延伸至正极空箔区上。第四层用于对裸露的正极空箔区表面起到绝缘保护的作用，减小了正极空箔区在机械滥用时与负极空箔区误接触短路的可能性，也减小了机械滥用时正极空箔区发生撕裂后刺穿隔离膜并与负极空箔区误接触短路的可能性。
在一些实施例中，第四层包括在卷绕方向上相对设置的第四层起始端和第四层终止端。第四层起始端位于正极空箔区。从第三方向观察，第四层终止端位于第一虚拟线和第二虚拟线之间。第四层用于对裸露的正极空箔区表面起到绝缘保护的作用，减小了正极空箔区在机械滥用时与负极空箔区误接触短路的可能性，也减小了机械滥用时正极空箔区发生撕裂后刺穿隔离膜并与负极空箔区误接触短路的可能性。
在一些实施例中，负极极片还包括包含绝缘材料的第五层，第五层设于负极卷绕次弧。第五层可增加负极卷绕次弧的厚度，即增加电极组件拐角处厚度。因此在夹具化成工艺中，有利于改善电极组件拐角处正极极片和负极极片的接触界面，降低拐角处析锂的可能性。第五层还用于支撑负极卷绕次弧，减小负极卷绕次弧处曲率半径过小时导致负极极片开裂的可能性。
在一些实施例中，第一负极活性材料层包括第一负极活性材料，第一负极活性材料包括石墨。第二负极活性材料层包括第二负极活性材料，第二负极活性材料包括石墨。第一负极活性材料层或第二负极活性材料层的至少一者的X射线衍射图谱包括004衍射峰和110衍射峰。004衍射峰的峰面积与110衍射峰的峰面积的比值为第一活性材料层或第二负极活性材料层的OI值，OI值的范围为5.0至20.0。通过降低OI值，增大了电解液与负极活性材料的接触面积，使得第一负极活性材料层或第二负极活性材料层的动力学性能提高，能够较快地嵌入锂离子，进一步降低析锂的可能性。
在一些实施例中，OI的范围为5.0至13.0，从而进一步提升第一负极活性材料层或第二负极活性材料层的动力学性能，降低析锂的可能性。
在一些实施例中，第一负极活性材料层或第二负极活性材料层的至少一者的拉曼光谱中位移范围为1255cm -1～1355cm -1与1575cm - 1～1600cm -1的峰分别为D峰和G峰。D峰和G峰的强度比值范围为0.05至0.80。通过提高D峰和G峰的强度比值，使得负极活性材料层具有适量的表面缺陷，提升了第一负极活性材料层的动力学性能，进一步降低了析锂的可能性。
在一些实施例中，D峰和G峰的强度比值范围为0.30至0.80，从而进一步降低析锂的可能性。
在一些实施例中，电化学装置还包括电解液。电解液包含锂盐，锂盐在电解液中的浓度范围为0.5mol/L至2.5mol/L。通过提高锂盐 浓度，有利于提高电解液的电导率，提升电化学装置的动力学性能，进一步降低了析锂的可能性。
在一些实施例中，锂盐在电解液中的浓度范围为1.0mol/L至2.5mol/L，从而进一步降低析锂的可能性。
在一些实施例中，第一层、第二层和第三层各自独立地包括基材层和粘接层。粘接层具有粘接性，基材层用于设置和支撑粘接层。
在一些实施例中，第一层的厚度范围为1μm至50μm，使得对应于正极极耳的电极组件与位于第一虚拟线和第二虚拟线之间的电极组件的厚度之差较小，从而有利于提高电化学装置的平整度。
本申请第二方面还提供一种电子装置，其包括如上所述的电化学装置。电子装置通过上述电化学装置供电，且电化学装置析锂可能性降低，因此具有改善的使用寿命。
附图说明
本申请的上述和/或附加的方面和优点从结合下面附图对实施例的描述中将变得明显和容易理解，其中：
图1为本申请一实施方式提供的电化学装置沿第一方向的视图。
图2为图1所示的电化学装置的电极组件沿第三方向的视图。
图3A为图2所示的电极组件A处的局部放大图。
图3B为图2所示的电极组件的负极极片的展开图。
图3C为图2所示的电极组件的正极极片的展开图。
图4为图2所示的电极组件A处于另一些实施例中的局部放大图。
图5为图2所示的电极组件A处于另一些实施例中的局部放大图。
图6为图3A所示的电极组件的第一层的放大图。
图7为图3A所示的电极组件的第二层的放大图。
图8为图2所示的电极组件A处于另一些实施例中的局部放大图。
图9为图2所示的电极组件A处于另一些实施例中的局部放大图。
图10为图2所示的电极组件A处于另一些实施例中的局部放大图。
图11为图2所示的电极组件A处于另一些实施例中的局部放大图。
图12为图2所示的电极组件A处于另一些实施例中的局部放大图。
图13为图3A所示的电极组件的第四层的放大图。
图14为图3A所示的电极组件的第三层的放大图。
图15为图3A所示的电极组件的第五层的放大图。
图16为本申请一实施方式提供的电子装置的结构示意图。
具体实施方式
下面对本申请实施例中的技术方案进行清楚、详细地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请。
下文，将详细地描述本申请的实施方式。但是，本申请可体现为许多不同的形式，并且不应解释为限于本文阐释的示例性实施方式。而是，提供这些示例性实施方式，从而使本申请透彻的和详细的向本领域技术人员传达。
另外，为了简洁和清楚，在附图中，各种组件、层的尺寸或厚度可被放大。遍及全文，相同的数值指相同的要素。如本文所使用，术语“及/或”、“以及/或者”包括一个或多个相关列举项目的任何和所有组合。另外，应当理解，当要素A被称为“连接”要素B时，要素A可直接连接至要素B，或可能存在中间要素C并且要素A和要素B可彼此间接连接。
进一步，当描述本申请的实施方式时使用“可”指“本申请的一个或多个实施方式”。
本文使用的专业术语是为了描述具体实施方式的目的并且不旨在限制本申请。如本文所使用，单数形式旨在也包括复数形式，除非上下文另外明确指出。应进一步理解，术语“包括”，当在本说明书中使用时，指存在叙述的特征、数值、步骤、操作、要素和/或组分，但是不排除存在或增加一个或多个其他特征、数值、步骤、操作、要素、组分和/或其组合。
空间相关术语，比如“上”等可在本文用于方便描述，以描述如图中阐释的一个要素或特征与另一要素(多个要素)或特征(多个特征)的关系。应理解，除了图中描述的方向之外，空间相关术语旨在包括设备或装置在使用或操作中的不同方向。例如，如果将图中的设备翻转， 则描述为在其他要素或特征“上方”或“上”的要素将定向在其他要素或特征的“下方”或“下面”。因此，示例性术语“上”可包括上面和下面的方向。应理解，尽管术语第一、第二、第三等可在本文用于描述各种要素、组分、区域、层和/或部分，但是这些要素、组分、区域、层和/或部分不应受这些术语的限制。这些术语用于区分一个要素、组分、区域、层或部分与另一要素、组分、区域、层或部分。因此，下面讨论的第一要素、组分、区域、层或部分可称为第二要素、组分、区域、层或部分，而不背离示例性实施方式的教导。
在本申请中，参数数值之间的大于、小于或不等于设计关系，需要排除测量设备的合理误差。
请参阅图1和图2，本申请一实施方式提供一种电化学装置100，包括壳体10、电极组件20、负极极耳30、正极极耳40和电解液(图未示)。电极组件20和电解液位于壳体10内，且电极组件20为卷绕结构。负极极耳30和正极极耳40均电连接于电极组件20，且由壳体10的内部伸出壳体10。壳体10可以是采用封装膜(如铝塑膜)封装得到的包装袋，即电化学装置100可以为软包电池。在另一些实施例中，电化学装置100并不限于软包电池，还可以为钢壳电池或铝壳电池等。图2示出电极组件20的数量为一个。在其它实施例中，电极组件20的数量也可以为多个，多个电极组件20位于壳体10内，且通过并联或者串联的方式电连接。
如图2所示，电极组件20包括负极极片21、正极极片22和隔离膜23，隔离膜23设置于负极极片21和正极极片22之间。负极极片21、隔离膜23和正极极片22依次层叠卷绕以形成电极组件20。电极组件20具有垂直于纸面的卷绕中心轴O。电极组件20具有卷绕方向D，卷绕方向D指的是沿着如图2所示的负极极片21、正极极片22或者隔离膜23的某一点绕着卷绕中心轴O从内向外移动的方向。卷绕方向D可以有两种，即绕着卷绕中心轴O进行顺时针或逆时针转动的方向。在一些实施例中，卷绕方向D为图2所示绕着卷绕中心轴O进行逆时针转动的方向。在另一些实施例中，卷绕方向D也可以为顺时针转动的方向。
如图2、图3A和图3B所示，负极极片21包括负极集流体210、第一负极活性材料层211和第二负极活性材料层212。负极集流体210包括相对设置的第一表面210a和第二表面210b，第一负极活性材料层211设于第一表面210a，第二负极活性材料层212设于第二表面210b。第一负极活性材料层211相较于第二负极活性材料层212 更靠近卷绕中心轴O。正极极片22包括正极集流体220、第一正极活性材料层221和第二正极活性材料层222。正极集流体220包括相对设置的第三表面220a和第四表面220b，第一正极活性材料层221设于第三表面220a，第二正极活性材料层222设于第四表面220b。第一正极活性材料层221相较于第二正极活性材料层222更靠近卷绕中心轴O。在本申请中，根据相互垂直的第一方向D 1、第二方向D 2和第三方向D 3建立三维坐标系。第一方向D 1为垂直于负极极耳30其中一表面的方向。第二方向D 2为正极极耳40至负极极耳30的方向。第三方向D 3在一些实施例中为卷绕中心轴O的方向。根据相互垂直的第四方向D 1’、第五方向D 2’和第三方向D 3建立另一三维坐标系。第四方向D 1’为负极极片21卷绕前的延伸方向，也为正极极片22卷绕前的延伸方向。第五方向X’为负极极片21展开后负极集流体210和第二负极活性材料层212的堆叠方向，也为正极极片22展开后正极集流体220和第二正极活性材料层222的堆叠方向。
在一些实施例中，正极集流体220可以使用铝箔或镍箔，负极集流体210可以使用铜箔、镍箔或碳基集流体中的至少一种。
正极活性材料层包含正极活性材料，正极活性材料包括可逆地嵌入和脱嵌锂离子的化合物(即，锂化插层化合物)。在一些实施例中，正极活性材料可以包括锂过渡金属复合氧化物。该锂过渡金属复合氧化物含有锂以及从钴、锰和镍中选择的至少一种元素。在一些实施例中，正极活性材料选自钴酸锂(LiCoO 2)、锂镍锰钴三元材料(NCM)、锰酸锂(LiMn 2O 4)、镍锰酸锂(LiNi 0.5Mn 1.5O 4)或磷酸铁锂(LiFePO 4)中的至少一种。
负极活性材料层包含负极活性材料，采用本领域已知的能够进行活性离子可逆脱嵌的负极活性材料，本申请不做限制。例如，可以是包括但不限于石墨、软碳、硬碳、碳纤维、中间相碳微球、硅基材料、锡基材料、钛酸锂或其他能与锂形成合金的金属等中的一种或多种的组合。其中，石墨可选自人造石墨、天然石墨以及改性石墨中的一种或多种的组合；硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅合金中的一种或多种的组合；锡基材料可选自单质锡、锡氧化合物、锡合金等中的一种或多种的组合。
隔离膜23包括聚乙烯、聚丙烯、聚偏氟乙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺或芳纶中的至少一种。例如，聚乙烯包括选自高密度聚乙烯、低密度聚乙烯或超高分子量聚乙烯中的至少一种。其中聚乙烯和聚丙烯，它们对改善短路具有良好的作用，并可以通过关断效 应改善电化学装置100的稳定性。
电解液的状态可以是凝胶态、固态和液态中的一种或多种。液态电解液包括锂盐和非水溶剂。锂盐选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、六氟砷酸锂(LiAsF 6)、高氯酸锂(LiClO 4)、四苯硼酸锂(LiB(C 6H 5) 4)、甲磺酸锂(LiCH 3SO 3)、双氟磺酰亚胺锂(LiFSI)、双三氟甲烷磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiCF 3SO 3)、双(三氟甲基磺酰)亚胺锂(LiN(SO 2CF 3) 2、三(三氟甲基磺酰)甲基锂(LiC(SO 2CF 3) 3)、二草酸硼酸锂(LiBOB)和二氟磷酸锂(LiPO 2F 2)中的一种或多种。例如，锂盐选用LiPF 6，因为它可以给出高的离子导电率并改善循环特性。非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、腈化合物、其它有机溶剂或它们的组合。碳酸酯化合物的实例为碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)、碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)、碳酸氟代亚乙酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯、碳酸三氟甲基亚乙酯及其组合。
如图3A所示，沿卷绕方向D，负极集流体210包括依次连接的负极空箔区2101、负极单面区2102和负极双面区2103。请一并参照图3A和图3B，负极空箔区2101的第一表面210a未设置第一负极活性材料层211，负极空箔区2101的第二表面210b未设置第二负极活性材料层212。负极单面区2102的第一表面210a设有第一负极活性材料层211，负极单面区2102的第二表面210b未设置第二负极活性材料层212。负极双面区2103的第一表面210a设有第一负极活性材料层211，负极双面区2103的第二表面210b设有第二负极活性材料层212。可以理解，负极空箔区2101、负极单面区2102和负极双面区2103三者的区分是针对各自的第一表面210a和第二表面210b上是否设有对应的负极活性材料层来界定，这并不意味着负极空箔区2101和负极单面区2102未设有负极活性材料层的表面上必须是全部裸露的。例如，负极空箔区2101的第一表面210a和/或第二表面210b上可设有其它功能层(如，包含绝缘材料的功能层；又如，包含导电剂和绝缘材料的功能层；或者，包含导电剂和粘结剂的功能层)。负极单面区2102的第二表面210b也可以设有其它功能层。
如图3A所示，沿卷绕方向D，负极极片21包括依次连接的负 极卷绕首层21a、负极卷绕首弧21b、负极卷绕次层21c、负极卷绕次弧21d、负极卷绕三层21e、负极卷绕三弧21f、负极卷绕四层21g和负极卷绕四弧21h。在一些实施例中，负极卷绕首层21a、负极卷绕次层21c、负极卷绕三层21e和负极卷绕四层21g分别为平直段；负极卷绕首弧21b、负极卷绕次弧21d、负极卷绕三弧21f和负极卷绕四弧21h分别为弯曲段。在其它实施例中，负极卷绕首层21a、负极卷绕次层21c、负极卷绕三层21e和负极卷绕四层21g也可以分别为弯曲段。其中，负极卷绕首层21a、负极卷绕首弧21b、负极卷绕次层21c和负极卷绕次弧21d构成负极极片21沿卷绕方向D进行卷绕后形成的负极卷绕首圈的至少一部分。负极卷绕三层21e、负极卷绕三弧21f、负极卷绕四层21g和负极卷绕四弧21h构成负极极片21沿卷绕方向D进行卷绕后形成的负极卷绕次圈的至少一部分。在本申请中，一圈指的是从负极极片21上的某个点作为起始端开始计算，沿着卷绕方向D一周到达另一个点为结束端，结束端与起始端以及此圈的中心在一条直线上，起始端在结束端和此圈中心之间。第一方向D 1也为自负极卷绕次层21c至负极卷绕首层21a的方向。第二方向D 2也为自负极卷绕首弧21b至负极卷绕次弧21d的方向。
负极空箔区2101位于负极卷绕首层21a。负极单面区2102至少位于负极卷绕首层21a和负极卷绕次层21c。负极单面区2102还位于负极卷绕首弧21b，如，负极单面区2102从负极卷绕首层21a沿卷绕方向D连续地延伸至负极卷绕首弧21b和负极卷绕次层21c。负极单面区2102包括负极单面区起始端2102a，且负极单面区起始端2102a位于负极卷绕首层21a。负极单面区起始端2102a指的是沿着卷绕方向D，负极单面区2102开始卷绕的部分，即为负极空箔区2101与负极单面区2102的交界位置。负极极耳30可连接于负极空箔区2101。在一些实施例中，负极极耳30连接于负极空箔区2101的朝向卷绕中心轴O的第一表面210a，负极极耳30位于负极卷绕首层21a。通过将负极极耳30设置于负极卷绕首层21a，可以降低负极极耳30的弯曲并提高负极极耳30的平整性。在一些实施例中，负极极耳30可焊接于负极空箔区2101，从而提高负极极耳30与负极空箔区2101的连接可靠性。
如图3A和图3C所示，正极集流体220包括正极双面区2202。正极双面区2202的第三表面220a设有第一正极活性材料层221，正极双面区2202的第四表面220b设有第二正极活性材料层222。如图3A所示，正极双面区2202位于所述负极卷绕次层21c背离卷绕中心 轴O的一侧，并沿卷绕方向D进一步延伸。在一些实施例中，正极集流体220还可包括正极空箔区2201，正极空箔区2201和正极双面区2202沿卷绕方向D依次连接。可以理解，正极双面区2202和正极空箔区2201二者的区分是针对各自的第三表面220a和第四表面220b上是否设有对应的正极活性材料层来界定，这并不意味着正极空箔区2201未设有负极活性材料层的表面上必须是全部裸露的。例如，正极空箔区2201的第三表面220a和/或第四表面220b上可设有其它功能层。沿卷绕方向D，正极极片22包括依次连接的正极卷绕首层22a、正极卷绕首弧22b、正极卷绕次层22c和正极卷绕次弧22d。在一些实施例中，正极卷绕首层22a和正极卷绕次层22c分别为平直段；正极卷绕首弧22b和正极卷绕次弧22d分别为弯曲段。在其它实施例中，正极卷绕首层22a和正极卷绕次层22c也可以分别为弯曲段。正极卷绕首层22a、正极卷绕首弧22b、正极卷绕次层22c和正极卷绕次弧22d构成正极极片22沿卷绕方向D进行卷绕后形成的正极卷绕首圈的至少一部分。正极卷绕首圈位于负极卷绕首圈背离卷绕中心轴O的一侧。此时，正极空箔区2201可位于正极卷绕首层22a和正极卷绕首弧22b，且位于正极卷绕首层22a的正极空箔区2201可隔着隔离膜23与位于负极卷绕首层21a的负极空箔区2101相对。正极空箔区2201包括正极空箔区起始端2201a。正极空箔区起始端2201a指的是沿着卷绕方向D，正极极片22的头部起始的部分。正极双面区2202位于正极卷绕次层22c和正极卷绕次弧22d，并沿卷绕方向D进一步延伸。正极极耳40可连接于位于正极卷绕首层22a的正极空箔区2201。在一些实施例中，正极极耳40连接于正极空箔区2201的背离卷绕中心轴O的第四表面220b，且正极极耳40位于正极卷绕首层22a。通过将正极极耳40设置于正极卷绕首层22a，可以降低正极极耳40的弯曲并提高正极极耳40的平整性。在一些实施例中，正极极耳40可焊接于正极空箔区2201，从而提高正极极耳40与正极空箔区2201的连接可靠性。在另一些实施例中，正极空箔区2201也可以去掉，减小电极组件20在第一方向D 1上的尺寸。在一些实施例中，在第二方向D 2上，正极极耳40在负极极耳30与位于负极卷绕首层21a的负极单面区2102之间。即，在第二方向D 2上，正极极耳40相较于负极极耳30更靠近位于负极卷绕首层21a的负极单面区2102。如此，可减小正极极耳40位置在第二方向D 2上靠近负极卷绕次弧21d时，正极空箔区起始端2201a刺穿隔离膜23并与负极卷绕次弧21d误接触短路的可能性。
正极双面区2202包括正极双面区起始端2202a。正极双面区起始端2202a指的是沿着卷绕方向D，正极双面区2202开始卷绕的部分，即为正极空箔区2201与正极双面区2202的交界位置(定义经过正极双面区起始端2202a且在第一方向D 1上延伸的线为交界线L 0)。由于正极双面区2202为双面涂布区域正极活性材料的区域，正极双面区起始端2202a也为正极极片22在卷绕方向D上厚度发生变化的位置。在第一方向D 1上，正极双面区起始端2202a与位于负极卷绕首层21a的负极单面区2102重叠。例如，在一些实施例中，在第一方向D 1上，正极双面区起始端2202a与负极单面区起始端2102a相离。
如图4所示，在另一些实施例中，在第一方向D 1上，正极双面区起始端2202a与负极单面区起始端2102a也可以刚好重叠，从第三方向D 3观察时交界线L 0经过负极单面区起始端2102a。此时，可以理解为负极单面区2102不仅位于负极卷绕次层21c并隔着隔离膜23与位于正极卷绕次层22c的正极双面区2202相对；而且，负极单面区2102还跨过负极卷绕首弧21b并延伸至负极卷绕首层21a上。如此，位于负极卷绕首层21a的负极单面区2102上的第二负极活性材料层212可在第一方向D 1上补偿电极组件20于正极双面区起始端2202a两侧的厚度差异，即补偿电极组件20位于交界线L 0两侧的厚度差异，从而有利于提高电化学装置100的平整度。
考虑到负极卷绕首弧21b曲率半径较小，即负极卷绕首弧21b曲率(弯曲程度)相对较大，为了减小跨过负极卷绕首弧21b并延伸至负极卷绕首层21a的负极单面区2102上的第二负极活性材料层212脱落的可能性，本申请还设置负极极片21包括包含绝缘材料的第一层51。第一层51位于负极卷绕首层21a且从第二负极活性材料层212上延伸至负极空箔区2101的第二表面210b上。第一层51包括在卷绕方向D上相对设置的第一层起始端51a和第一层终止端51b。第一层起始端51a位于负极空箔区2101上，第一层终止端51b位于第二负极活性材料层212上且覆盖负极单面区起始端2102a。因此，第一层51可用于固定位于负极卷绕首层21a的负极单面区2102上的第二负极活性材料层212，减小该部分第二负极活性材料层212上的负极活性材料脱离负极集流体210的可能性。
其中，当正极极耳40连接于位于正极卷绕首层22a的正极空箔区2201时，位于负极卷绕首层21a的负极单面区2102上的第二负极活性材料层212和第一层51还可补偿电极组件20于正极极耳40 对应位置处相较于其它区域的厚度差异，有利于进一步提高电化学装置100的平整度。
在本申请中，可通过以下步骤确定负极单面区2102和第一层51在电极组件20中的位置关系：(1)将电化学装置100以0.2C放电至2.75V；(2)配置树脂组合物，其由水晶胶树脂基体(如环氧树脂)、催化剂及固化剂按照一定比例调配而成；(3)将树脂组合物倒入模具中，并将电化学装置100的壳体10切开后倾斜地置于模具中，以减少电化学装置100底部可能残存的气泡，再继续缓慢倒入树脂组合物，使得将电化学装置100完全浸没于树脂组合物中，使得树脂组合物通过壳体10的切口缓慢流入壳体10内；(4)将电化学装置100至位置水平，将多余的气泡排出，然后静置至树脂组合物凝固；(5)沿垂直于第三方向D 3的截面切割电化学装置100头部并对切割面进行打磨，从而得到将电化学装置100的截面；(6)采用光学显微镜观察电化学装置100的上述截面，可确定负极单面区2102和第一层51在电极组件20中的位置关系。
在一些实施例中，第一层51的材质可以选自聚偏氟乙烯、改性聚偏氟乙烯、聚丙烯酸酯、改性聚丙烯酸酯、改性聚乙烯、改性聚二烯，聚环氧乙烷、聚偏二氟乙烯、丁苯橡胶、改性橡胶、偏二氟乙烯与六氟丙烯的共聚物、丁二烯、丙烯腈、苯乙烯、甲基丙烯酸甲酯、丙烯酸丁酯、乙烯基吡咯烷酮、甲基丙烯酸异辛酯、丙烯酸异辛酯、聚偏二氟乙烯、9-十八烯腈、丙酸丙酯、丙酸乙酯、N-甲基吡咯烷酮或4-苯基环己酮中的至少一种绝缘材料。第一层51可以为单面胶或双面胶。在另一些实施例中，第一绝缘层51还可以为陶瓷层。在一些实施例中，陶瓷层包括陶瓷材料，陶瓷材料包括二氧化铪、钛酸锶、二氧化锡、氧化铯、氧化镁、氧化镍、氧化钙、氧化钡、氧化锌、氧化锆、氧化钇、三氧化二铝、氧化钛、二氧化硅、勃姆石、氢氧化镁或氢氧化铝中的至少一种。
如图6所示，在一些实施例中，第一层51可以为两层或多层结构。例如，第一层51可包括层叠设置的第一基材层511和第一粘接层512。此时，第一层51可以为单面胶，第一基材层511用于设置和支撑第一粘接层512。在第一方向D 1上，第一粘接层512设于第一基材层511和负极卷绕首层21a之间。第一粘接层512具有粘接性，第一层51通过第一粘接层512粘接在负极卷绕首层21a上。此时，第一基材层511和第一粘接层512的材质各自独立地选自上述绝缘材料。进一步地，在一些实施例中，第一粘接层512中的粘接材 料可嵌入位于负极卷绕首层21a的第二负极活性材料层212中，从而将该部分第二负极活性材料层212中的负极活性材料粘接在一起。如此，可进一步减小该部分第二负极活性材料层212的负极活性材料脱离负极集流体210的可能性。在其它实施例中，第一层51还可以为双面胶。
本申请中，通过设置负极单面区2102位于负极卷绕首层21a并使在第一方向D 1上正极双面区起始端2202a与位于负极卷绕首层21a的负极单面区2102重叠，同时在负极卷绕首层21a上设置第一层51，使得电化学装置100的平整性提高。因此，可减小夹具化成工艺中因化成夹板首先接触电极组件20较厚处(如正极双面区起始端2202a所在位置，或者，正极极耳40所在位置)导致电极组件20其它位置由于较薄而受压不足甚至不受压的可能性。可以理解，当电极组件20某位置受压不足甚至不受压时，该位置的正极极片22、隔离膜23和负极极片21之间界面接触不紧密，且在长期的充放电过程中界面接触不断恶化，这会提高界面阻抗，影响锂离子传输，导致过量的锂离子囤积并产生锂枝晶。因此，本申请可降低夹具化成时电极组件20局部受压不足导致析锂的可能性，延长了电化学装置100的使用寿命。
考虑到位于交界线L 0一侧的正极双面区2202与位于交界线L 0另一侧起厚度补偿作用的第二负极活性材料层212二者之间存在厚度差异。如图5所示，在一些实施例中，在第一方向D 1上，可设置正极双面区起始端2202a与第一层51重叠。如此，第一层51还可用于在第一方向D 1上进一步补偿电极组件20于正极双面区起始端2202a两侧的厚度差异，有利于进一步提高电化学装置100的平整度。
如图3A所示，在一些实施例中，负极单面区2102从负极卷绕首层21a至少延伸至负极卷绕三弧21f，即，负极单面区2102至少位于负极卷绕首层21a、负极卷绕首弧21b、负极卷绕次层21c、负极卷绕次弧21d、负极卷绕三层21e和负极卷绕三弧21f。在一些实施例中，负极单面区2102位于负极卷绕首层21a、负极卷绕首弧21b、负极卷绕次层21c、负极卷绕次弧21d、负极卷绕三层21e和负极卷绕三弧21f。此时，负极双面区2103位于负极卷绕四层21g并沿卷绕方向D进一步延伸。相较于在负极卷绕次弧21d、负极卷绕三层21e和负极卷绕三弧21f设置负极双面区的情况，本申请可减少负极活性材料的使用量，也可以提高能量密度。负极双面区2103包括负极双面区起始端2103a，且负极双面区起始端2103a位于负极卷绕四 层21g。负极双面区起始端2103a指的是负极双面区2103开始卷绕的部分，即为负极单面区2102与负极双面区2103的交界位置。为了减小负极双面区起始端2103a的第一负极活性材料层211析锂的可能性，可设置负极双面区起始端2103a沿卷绕方向D的反方向超出正极双面区起始端2202a。
如图3A所示，在一些实施例中，正极极片22还包括包含绝缘材料的第二层52，第二层52覆盖正极双面区起始端2202a，并从第一正极活性材料层221或第二正极活性材料层222上延伸至正极空箔区2201上。在一些实施例中，第二层52从第二正极活性材料层222上延伸至正极空箔区2201背离卷绕中心的第四表面220b上。第二层52包括在卷绕方向D上相对设置的第二层起始端52a和第二层终止端52b。第二层起始端52a位于正极空箔区2201上，第二层终止端52b位于第二正极活性材料层222上。第二层52用于对裸露的正极空箔区2201的第四表面220b起到绝缘保护的作用，减小了正极空箔区2201在机械滥用时与负极空箔区2101误接触短路的可能性，也减小了机械滥用时正极空箔区2201发生撕裂、且撕裂的正极空箔区2201刺穿隔离膜23并与负极空箔区2101误接触短路的可能性。而且，由于第二层52覆盖部分第二正极活性材料层222，因此第二层52也可以减小当负极双面区起始端2103a未超出正极双面区起始端2202a时，临近正极双面区起始端2202a的部分第二正极活性材料层222脱出的锂离子未能够充分被第一负极活性材料层211接收的可能性，从而减少过量的锂离子囤积并析锂的可能性。
在一些实施例中，第二层52的材质可以选自聚偏氟乙烯、改性聚偏氟乙烯、聚丙烯酸酯、改性聚丙烯酸酯、改性聚乙烯、改性聚二烯，聚环氧乙烷、聚偏二氟乙烯、丁苯橡胶、改性橡胶、偏二氟乙烯与六氟丙烯的共聚物、丁二烯、丙烯腈、苯乙烯、甲基丙烯酸甲酯、丙烯酸丁酯、乙烯基吡咯烷酮、甲基丙烯酸异辛酯、丙烯酸异辛酯、聚偏二氟乙烯、9-十八烯腈、丙酸丙酯、丙酸乙酯、N-甲基吡咯烷酮或4-苯基环己酮中至少一种。第二层52可以为单面胶或双面胶。在另一些实施例中，第二层52还可以为陶瓷层。
如图7所示，在一些实施例中，第二层52可以为两层或多层结构。例如，第二层52可包括层叠设置的第二基材层521和第二粘接层522。此时，第二层52可以为单面胶，第二基材层521用于设置和支撑第二粘接层522。在第一方向D 1上，第二粘接层522设于第二基材层521和正极空箔区2201之间。第二粘接层522具有粘接性， 第二层52通过第二粘接层522粘接在正极空箔区2201上。此时，第二基材层521和第二粘接层522的材质各自独立地选自上述绝缘材料。在其它实施例中，第二层52还可以为双面胶。
如图3A所示，定义经过负极双面区起始端2103a且沿第一方向D 1延伸的线为第一虚拟线L 1，经过第二层终止端52b且沿第一方向D 1延伸的线为第二虚拟线L 2。在第二方向D 2上，第一虚拟线L 1相较于第二虚拟线L 2更靠近负极卷绕首弧21b，第二虚拟线L 2相较于第一虚拟线L 1更靠近卷绕中心轴O。由于负极双面区起始端2103a沿卷绕方向D的反方向超出正极双面区起始端2202a，交界线L 0位于第一虚拟线L 1和第二虚拟线L 2之间。其中，位于第一虚拟线L 1和第二虚拟线L 2之间的负极极片21可能会发生析锂，原因在于：
首先，由于负极极片21在卷绕方向D上自负极单面区2102至负极双面区2103的交界位置(即负极双面区起始端2103a处)存在厚度变化，因此在辊压过程中，临近负极双面区起始端2103a且位于第一虚拟线L 1和第二虚拟线L 2之间的部分第一负极活性材料层211或第二负极活性材料层212容易受到过辊压或辊压不完全的影响。其中，过辊压可能导致负极活性材料压实密度较高甚至破碎，造成固体电解质界面膜(SEI膜)成膜不均匀，存在循环恶化可能性；另一方面也可能导致电解液浸润不良，表面阻抗增加，导致析锂。辊压不完全可能导致该部分第一负极活性材料层211或第二负极活性材料层212密度较低，孔隙较多，导致该部分第一负极活性材料层211或第二负极活性材料层212对电解液的需求量也对应增大，经过长期的充放电循环后，由于该部分第一负极活性材料层211或第二负极活性材料层212附近电解液消耗较快，局部极化增大，从而导致析锂。
其次，位于第一虚拟线L 1和第二虚拟线L 2之间的负极极片21靠近电极组件20拐角处。拐角处电极组件20厚度较薄，在夹具化成工艺中容易受压不足甚至不受压，使得该位置的正极极片22、隔离膜23和负极极片21之间界面接触不紧密，且在长期的充放电过程中界面接触不断恶化，导致析锂。
为了降低位于第一虚拟线L 1和第二虚拟线L 2之间的负极极片21发生析锂的可能性，如图3A所示，在一些实施例中，从第三方向D 3观察，可设置负极单面区起始端2102a位于第一虚拟线L 1和第二虚拟线L 2之间。其中，由于在第一方向D 1上正极双面区起始端2202a与位于负极卷绕首层21a的负极单面区2102重叠，因此在第二方向D 2上，定义第一虚拟线L 1和第二虚拟线L 2之间的距离为L，负极单 面区起始端2102a和第一虚拟线L 1之间的距离为a，正极双面区起始端2202a和第二虚拟线L 2之间的距离为b，则a+b≥L。具体地，当在第一方向上正极双面区起始端2202a与负极单面区起始端2102a刚好重叠时，则a+b＝L；当在第一方向D 1上正极双面区起始端2202a与负极单面区起始端2102a不重叠时，则a+b>L。
此时，可使得位于第一虚拟线L 1和第二虚拟线L 2之间的电极组件20被位于负极卷绕首层21a的负极单面区2102上的第二负极活性材料层212填充以实现厚度补偿。由于第一层51设于负极卷绕首层21a，位于第一虚拟线L 1和第二虚拟线L 2之间的电极组件20还可以被第一层51填充以实现厚度补偿。因此，可使得在夹具化成工艺中，化成夹板能够紧密压实第一虚拟线L 1和第二虚拟线L 2之间的电极组件20，改善正极极片22和负极极片21的接触界面，降低发生析锂的可能性。
在一些实施例中，可设置第一层51的厚度H范围(在图6中标出)为1μm至50μm。通过设置第一层51的厚度范围，使得对应于正极极耳40的电极组件20与第一虚拟线L 1和第二虚拟线L 2之间的电极组件20的的厚度之差不超过20μm，从而有利于使得电化学装置100更加平整。此外，通过设置第一层51的厚度下限，也减小了第一层51的制造难度。其中，可在获得电极组件20上述截面后，采用卡尺或其它合适的量具测得厚度H，或者也可以采集电化学装置100上述截面的图像并在图像中进行测量。
如图8所示，在另一些实施例中，负极单面区2102的位置也可以改变。例如，负极单面区2102还可仅位于负极卷绕首层21a、负极卷绕首弧21b、负极卷绕次层21c、负极卷绕次弧21d和负极卷绕三层21e。此时，负极双面区2103位于负极卷绕三弧21f和负极卷绕四层21g并沿卷绕方向D进一步延伸，负极双面区起始端2103a位于负极卷绕三弧21f。相较于图3A所示的结构，由于负极卷绕三弧21f设置负极双面区2103，有利于增加电极组件20拐角处厚度。因此在夹具化成工艺中，有利于改善正极极片22和负极极片21的接触界面，降低电极组件20拐角处析锂的可能性。
如图9所示，在另一些实施例中，负极单面区起始端2102a的位置也可以改变。例如，负极单面区起始端2102a也可以在第二方向D 2上位于第二虚拟线L 2背离第一虚拟线L 1的一侧。因此，在第二方向D 2上位于第二虚拟线L 2背离第一虚拟线L 1的一侧的负极空箔区2101上具有第二负极活性材料层212。如此，同样可使得在第一虚拟 线L 1和第二虚拟线L 2之间的电极组件20被位于负极卷绕首层21a的负极单面区2102填充以实现厚度补偿。此外，在第二方向D 2上位于第二虚拟线L 2背离第一虚拟线L 1的一侧的负极空箔区2101上的第二负极活性材料层212还可补偿对应于正极极耳40的电极组件20厚度与第二虚拟线L 2背离第一虚拟线L 1的一侧的电极组件20厚度之间的差异，有利于进一步提高电化学装置100的平整度。
进一步地，在一些实施例中，在第一方向D 1上，正极极耳40与位于负极卷绕首层21a的负极单面区2102相离。即，在第一方向D 1上，正极极耳40与位于负极卷绕首层21a的负极单面区2102不重叠，从而减小二者重叠时对应于正极极耳40的电极组件20厚度增加的可能性，从而减小了对电化学装置100能量密度的影响。
如图3A所示，在一些实施例中，第一层起始端51a在第二方向D 2上可位于第二虚拟线L 2背离第一虚拟线L 1的一侧，第一层终止端51b可与第一虚拟线L 1重合。因此，在第二方向D 2上位于第二虚拟线L 2背离第一虚拟线L 1的一侧的负极空箔区2101上具有第一层51。此时，位于第二虚拟线L 2背离第一虚拟线L 1一侧的第一层51还可补偿对应于正极极耳40的电极组件20与第二虚拟线L 2背离第一虚拟线L 1的一侧的电极组件20之间的厚度差异，有利于进一步提高电化学装置100的平整度。此外，由于此时第一层51覆盖负极空箔区2101的部分第二表面210b，因此可用于对裸露的负极空箔区2101的第二表面210b起到绝缘保护的作用，减小了负极空箔区2101在机械滥用时与正极空箔区2201误接触短路的可能性，也减小了机械滥用时负极空箔区2101发生撕裂、且撕裂的负极空箔区2101刺穿隔离膜23并与正极空箔区2201误接触短路的可能性。
进一步地，在第一方向D 1上，第一层51与正极极耳40相离。即，在第一方向D 1上，第一层51与正极极耳40不重叠，减小二者重叠时对应于正极极耳40的电极组件20厚度增加的可能性，从而减小了对电化学装置100能量密度的影响。如图10所示，在另一些实施例中，在第一方向D 1上，第一层51也可以与正极极耳40重叠，从而降低了对第一层50在第一方向D 1上宽度的裁切要求和对第一层50位置的精度控制要求。
如图3A所示，在一些实施例中，正极极耳40、负极极耳30和正极空箔区起始端2201a在第一方向D 1上相离。即，正极极耳40、负极极耳30和正极空箔区起始端2201a在第一方向D 1上不重叠。正极极耳40与负极极耳30不重叠，因此减小了二者重叠时对应于正 极极耳40的电极组件20厚度增加的可能性，从而可提升电化学装置100的能量密度。正极极耳40与正极空箔区起始端2201a不重叠，因此减小了焊接时正极极耳40超出正极空箔区2201的可能性，也减小了对正极极耳40焊接位置的精度要求。
如图11所示，在另一些实施例中，从第三方向D 3观察，第一层起始端51a也可以与第二虚拟线L 2重合。即，第一层51不超过第一虚拟线L 1和第二虚拟线L 2之间所界定的范围。
如图12所示，在另一些实施例中，第一层终止端51b在第二方向D 2上也可以位于第一虚拟线L 1背离第二虚拟线L 2的一侧。因此，部分第一层51设于电极组件20拐角处。如此，第一层51还可增加电极组件20拐角处厚度。因此在夹具化成工艺中，有利于改善第一虚拟线L 1和第二虚拟线L 2之间正极极片22和负极极片21的接触界面，降低电极组件20拐角处析锂的可能性。
如图3A所示，在一些实施例中，第二层52延伸至正极卷绕首层22a并在第一方向D 1上与正极极耳40重叠。此时，第二层52还用于覆盖正极极耳40表面的毛刺或焊印(毛刺可在裁切正极极耳40时产生，焊印可将正极极耳40焊接于正极空箔区2201时产生，但本申请并不作限制)，减小上述毛刺或焊印刺穿隔离膜23的可能性，延长电化学装置100的使用寿命。
如图3A所示，在一些实施例中，正极极片22还包括包含绝缘材料的第四层54。第四层54覆盖临近正极双面区起始端2202a的部分第一正极活性材料层221，并从第一正极活性材料层221上延伸至正极空箔区2201朝向卷绕中心轴O的第三表面220a上。第四层54包括在卷绕方向D上相对设置的第四层起始端54a和第四层终止端54b。第四层起始端54a位于正极空箔区2201上，第四层终止端54b位于第一正极活性材料层221上。第四层54用于对裸露的正极空箔区2201的第三表面220a起到绝缘保护的作用，减小了正极空箔区2201在机械滥用时与负极空箔区2101误接触短路的可能性，也减小了机械滥用时正极空箔区2201发生撕裂、且撕裂的正极空箔区2201刺穿隔离膜23并与负极空箔区2101误接触短路的可能性。从第三方向D 3观察，第四层终止端54b位于第一虚拟线L 1和第二虚拟线L 2之间。因此沿卷绕方向D，第二层终止端52b超过第四层终止端54b。
其中，第四层54的材质可以选自聚偏氟乙烯、改性聚偏氟乙烯、聚丙烯酸酯、改性聚丙烯酸酯、改性聚乙烯、改性聚二烯，聚环氧乙烷、聚偏二氟乙烯、丁苯橡胶、改性橡胶、偏二氟乙烯与六氟丙烯的 共聚物、丁二烯、丙烯腈、苯乙烯、甲基丙烯酸甲酯、丙烯酸丁酯、乙烯基吡咯烷酮、甲基丙烯酸异辛酯、丙烯酸异辛酯、聚偏二氟乙烯、9-十八烯腈、丙酸丙酯、丙酸乙酯、N-甲基吡咯烷酮或4-苯基环己酮中至少一种。第四层54可以为单面胶或双面胶。在另一些实施例中，第四层54还可以为陶瓷层。
如图13所示，在一些实施例中，第四层54可以为两层或多层结构。例如，第四层54可包括层叠设置的第四基材层541和第四粘接层542。此时，第四层54可以为单面胶，第四基材层541用于设置和支撑第四粘接层542。在第一方向D 1上，第四粘接层542设于第四基材层541和正极空箔区2201之间。第四粘接层542具有粘接性，第四层54通过第四粘接层542粘接在正极空箔区2201上。此时，第四基材层541和第四粘接层542的材质各自独立地选自上述绝缘材料。在其它实施例中，第四层54也可以为双面胶。
可以理解，由于负极单面区2102设于负极卷绕首层21a上，因此负极单面区起始端2102a未超出正极双面区起始端2202a的可能性较小，临近正极双面区起始端2202a的部分第一正极活性材料层221脱出的锂离子未能够充分被第二负极活性材料层212接收并析锂的可能性也较小。因此在另一些实施例中，第四层54可以不覆盖临近正极双面区起始端2202a的部分第一正极活性材料层221。或者，在已设置第二层52对正极空箔区2201进行绝缘保护的前提下，第四层54也可以省略。
如图3A所示，在一些实施例中，电化学装置100还包括包含绝缘材料的第三层53。第三层53设于负极空箔区2101背离卷绕中心轴O的第二表面210b。在第一方向D 1上，第三层53与负极极耳30和正极空箔区起始端2201a重叠。因此，第三层53可覆盖负极极耳30的焊印或毛刺，而且还用于覆盖正极空箔区起始端2201a，减小正极空箔区2201和负极空箔区2101误接触短路的可能性。
其中，第三层53的材质可以选自聚偏氟乙烯、改性聚偏氟乙烯、聚丙烯酸酯、改性聚丙烯酸酯、改性聚乙烯、改性聚二烯，聚环氧乙烷、聚偏二氟乙烯、丁苯橡胶、改性橡胶、偏二氟乙烯与六氟丙烯的共聚物、丁二烯、丙烯腈、苯乙烯、甲基丙烯酸甲酯、丙烯酸丁酯、乙烯基吡咯烷酮、甲基丙烯酸异辛酯、丙烯酸异辛酯、聚偏二氟乙烯、9-十八烯腈、丙酸丙酯、丙酸乙酯、N-甲基吡咯烷酮或4-苯基环己酮中至少一种。第三层53可以为单面胶或双面胶。在另一些实施例中，第三层53还可以为陶瓷层。
如图14所示，在一些实施例中，第三层53可以为两层或多层结构。例如，第三层53可包括层叠设置的第三基材层531和第三粘接层532。此时，第三层53可以为单面胶，第三基材层531用于设置和支撑第三粘接层532。在第一方向D 1上，第三粘接层532设于第三基材层531和负极空箔区2101之间。第三粘接层532具有粘接性，第三层53通过第三粘接层532粘接在负极空箔区2101上。此时，第三基材层531和第三粘接层532的材质各自独立地选自上述绝缘材料。在其它实施例中，第三层53也可以为双面胶。
如图3A所示，在一些实施例中，负极极片21还包括包含绝缘材料的第五层55，第五层55设于负极卷绕次弧21d。在一些实施例中，当负极单面区2102延伸至负极卷绕次弧21d时，第五层55可设于位于负极卷绕次弧21d的负极单面区2102的第一表面210a上。第五层55可增加负极卷绕次弧21d的厚度，如此，第五层55可增加电极组件20拐角处厚度。因此在夹具化成工艺中，有利于改善拐角处正极极片22和负极极片21的接触界面，降低电极组件20拐角处析锂的可能性。此外，第五层55还用于支撑负极卷绕次弧21d，减小负极卷绕次弧21d处曲率半径过小时导致负极极片21开裂的可能性。
其中，第五层55的材质可以选自聚偏氟乙烯、改性聚偏氟乙烯、聚丙烯酸酯、改性聚丙烯酸酯、改性聚乙烯、改性聚二烯，聚环氧乙烷、聚偏二氟乙烯、丁苯橡胶、改性橡胶、偏二氟乙烯与六氟丙烯的共聚物、丁二烯、丙烯腈、苯乙烯、甲基丙烯酸甲酯、丙烯酸丁酯、乙烯基吡咯烷酮、甲基丙烯酸异辛酯、丙烯酸异辛酯、聚偏二氟乙烯、9-十八烯腈、丙酸丙酯、丙酸乙酯、N-甲基吡咯烷酮或4-苯基环己酮中至少一种。第五层55可以为单面胶或双面胶。在另一些实施例中，第五层55还可以为陶瓷层。
如图15所示，在一些实施例中，第五层55可以为两层或多层结构。例如，第五层55可包括层叠设置的第五基材层551和第五粘接层552。此时，第五层55可以为单面胶，第五基材层551用于设置和支撑第五粘接层552。在第一方向D 1上，第五粘接层552设于第五基材层551和负极单面区2102之间。第五粘接层552具有粘接性，第五层55通过第五粘接层552粘接在负极单面区2102上。此时，第五基材层551和第五粘接层552的材质各自独立地选自上述绝缘材料。在其它实施例中，第五层55也可以为双面胶。
本申请中，还可通过改善负极极片21的动力学性能，从而进一 步降低负极极片21的析锂可能性。在一些实施例中，第一负极活性材料层211包括第一负极活性材料，第一负极活性材料包括石墨。第一负极活性材料层211的X射线衍射图谱包括004衍射峰和110衍射峰。004衍射峰的峰面积与110衍射峰的峰面积比值为第一负极活性材料层211的取向指数(即OI值)，OI值的范围为5.0至20.0。其中，OI值可用于表征负极活性物质层的各向异性。OI值越小，负极活性材料层的各向异性越小，各向同性越大，电解液与负极活性材料的接触面积增大，有利于锂离子的扩散。因此本申请通过降低OI值，使得第一负极活性材料层211的动力学性能提高，能够较快地嵌入锂离子，进一步降低析锂的可能性。同时，通过设置OI值的下限，减小了负极极片在制作过程中负极活性材料容易脱落的可能性。在一些实施例中，OI值的范围为5.0至13.0，从而进一步提升第一负极活性材料层211的动力学性能，降低析锂的可能性。其中，按照中华人民共和国机械行业标准JB/T4220-2011《人造石墨的点阵参数测定方法》测试负极活性材料的X射线衍射图谱中的004衍射峰和110衍射峰。试验条件如下：采用碳酸二甲酯(DMC)清洗负极活性材料并烘干；X射线采用CuKα辐射，CuKα辐射由滤波片或单色器除去；在记录004衍射峰时，衍射角2θ的扫描范围为53°至57°。在记录110衍射峰时，衍射角2θ的扫描范围为75°至79°；然后，计算由004衍射峰得到的峰面积与由110衍射峰得到的峰面积的比值，该比值即为OI值。在一些实施例中，第二负极活性材料层212包括第二负极活性材料，第一负极活性材料包括石墨。此时，也可以设置第二负极活性材料层212的OI值范围为5.0至20.0，从而提升第二负极活性材料层212的动力学性能，降低第二负极活性材料层212析锂的可能性。
在一些实施例中，当第一负极活性材料层211的第一负极活性材料包括石墨时，第一负极活性材料层的拉曼光谱中位移范围为1255cm -1～1355cm -1与1575cm -1～1600cm -1的峰分别为D峰和G峰，D峰和G峰的强度比值范围为0.05至0.80。其中，第一负极活性材料层在拉曼光谱中位移范围为1255cm -1～1355cm -1的峰代表碳原子的晶格缺陷，峰值越高表示缺陷碳的含量越高；在位移范围为1575cm - 1～1600cm -1的峰代表碳原子sp 2杂化的面内伸缩振动。D峰和G峰的强度比值可用于表征负极活性材料的表面缺陷度。D峰和G峰的强度比值越高，表明负极活性材料的表面缺陷较高，这有利于增加负极活性材料与电解液的接触面积，有利于电解液的浸润，另一方面， 负极活性材料的表面缺陷还可以增加离子嵌入的通道，有利于离子的传递。因此本申请通过提高D峰和G峰的强度比值，使得负极活性材料层具有适量的表面缺陷，提升了第一负极活性材料层211的动力学性能，进一步降低了析锂的可能性。同时，通过限定峰和G峰的强度比值的下限值，减小了负极活性材料表面缺陷度过高时对电解液消耗速度过快的可能性，提高了电化学装置100的循环能力。其中，缺陷可以包括负极活性材料的晶体结构中引入杂原子而产生的点缺陷、部分原子缺失导致的空穴缺陷、或者晶格错位引起的缺陷中的至少一种。在一些实施例中，D峰和G峰的强度比值范围为0.30至0.80，从而进一步降低析锂的可能性。其中，D峰和G峰的强度比值测试方法如下：在负极活性材料层上选取一个大小为100μm×100μm的面积，利用激光显微共聚焦拉曼光谱仪(Raman，HR Evolution，HORIBA科学仪器事业部)扫描该面积内的负极活性材料，拉曼光谱仪的激光波长可处于532nm至785nm的范围内，得到该面积范围内所有负极活性材料的D峰和G峰；采用LabSpec软件对数据进行处理得到每个颗粒的D峰和G峰的强度，分别记为I D和I G，以0.02为步长统计I D/I G的频次得到正态分布图，统计这些颗粒，计算I D/I G的平均值和方差。在一些实施例中，当第二负极活性材料层212的第二负极活性材料包括石墨时，也可以设置第二负极活性材料中D峰和G峰的强度比值范围为0.05至0.80，从而提升第二负极活性材料层212的动力学性能，降低第二负极活性材料层212析锂的可能性。
在一些实施例中，锂盐在电解液中的浓度范围为0.5mol/L至2.5mol/L。锂盐溶解于溶剂体系中并电离，部分形成溶剂化的锂离子和对应阴离子团，提供离子导通能力。因此本申请通过提高锂盐在电解液中的浓度，有利于提高电解液的电导率，提升电化学装置100的动力学性能，进一步降低了析锂的可能性。同时，通过设置锂盐浓度的上限值，减小了锂盐浓度过大可能会导致难以溶解或者溶解后低温存储时出现析晶的可能性。在一些实施例中，锂盐在电解液中的浓度范围为1.0mol/L至2.5mol/L，从而进一步降低析锂可能性。其中，锂盐在电解液中的浓度采用离子色谱仪测定。
虽然以上电化学装置100以锂离子电池进行举例说明，然而，本申请还适用于其它合适的电化学装置，这样的电化学装置100包括可以发生电化学反应的任何装置，如所有种类的一次电池、二次电池、燃料电池、太阳能电池或电容。特别的，电化学装置100可以是锂二次电池，包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池 和锂离子聚合物二次电池。
请参阅图16，本申请一实施方式还提供一种电子装置1，包括上述电化学装置100。电子装置1通过上述电化学装置100供电，且电化学装置100的析锂可能性降低，从而维持较长的使用寿命。在一实施方式中，本申请的电子装置1可以是，但不限于笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
以下通过具体实施例和对比例对本申请提供的电化学装置的性能进行说明。其中，以电化学装置为锂离子软包电池为例并结合具体制备过程和测试方法对本申请进行说明，本领域技术人员应理解，本申请中描述的制备方法仅是实例，其他任何合适的制备方法均在本申请的范围内。
实施例1
负极极片21的制备：将负极活性材料人造石墨、导电炭黑(Super P)、丁苯橡胶(SBR)按照重量比96:1.5:2.5进行混合，加入去离子水作为溶剂，调配成重量百分比为70wt％的浆料，并搅拌均匀。将浆料均匀涂覆在厚度为10μm的铜箔一表面上，110℃条件下烘干，得到厚度为150μm的第一负极活性材料层211。在铜箔另一表面上重复以上步骤，得到厚度为150μm的第二负极活性材料层212。在负极极片21的负极空箔区2101上焊接负极极耳30，在负极单面区起始端2102a上覆盖第一层51，第一层51从第一负极活性材料层211上延伸至负极空箔区2101上。负极极耳30材质为镍(Ni)，第一层51材质为聚偏氟乙烯，第一层51厚度为11μm。经测试，第一负极活性材料层211和第二负极活性材料层212的OI值均为15.0，第一负极活性材料层211和第二负极活性材料层212的拉曼光谱中D峰和G峰的强度比值均为0.20。
正极极片22的制备：将正极活性材料钴酸锂(LiCoO 2)、导电炭黑(Super P)、聚偏二氟乙烯(PVDF)按照重量比97.5:1.0:1.5进行混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成固含量为75wt％的浆料，并搅拌均匀。将浆料均匀涂覆在厚度为12μm的铝箔一表面上，90℃条件下烘干，得到厚度为100μm的第一正极活性材料层221。 在铝箔另一表面上重复以上步骤，得到厚度为100μm的第二正极活性材料层222。在正极极片22的正极空箔区2101上正极极耳40，正极极耳40材质为铝(Al)。
电解液的制备：在干燥氩气气氛中，首先将有机溶剂碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)以质量比EC:EM C:DEC＝30:50:20混合，然后向有机溶剂中加入锂盐六氟磷酸锂(LiPF 6)溶解并混合均匀，得到锂盐浓度为0.8mol/L的电解液。
电极组件20的制备：将负极极片21、隔离膜23和正极极片22依次层叠卷绕得到电极组件20，隔离膜23选用厚度为15μm的聚乙烯(PE)膜。卷绕后，如图2和图3A所示，负极单面区2102沿着卷绕方向D从负极卷绕首层21a延伸至负极卷绕三弧21f，负极单面区起始端2102a位于第一虚拟线L 1和第二虚拟线L 2之间。在第一方向D 1上，正极双面区起始端2202a与位于负极卷绕首层21a的负极单面区2102重叠。第一层51位于负极卷绕首层21a且从第一负极活性材料层211上延伸至负极空箔区2101的第二表面210b上。第一层起始端51a在第二方向D 2上位于第二虚拟线L 2背离第一虚拟线L 1的一侧。在第一方向D 1上，第一层51与正极极耳40不重叠。
锂离子电池的制备：将冲坑成型的铝塑膜(厚度为150μm)置于组装夹具内，坑面朝上，将电极组件20置于坑内。向铝塑膜的坑内注入电解液，并将正极极耳40和负极极耳30引出铝塑膜外。然后进行化成，封装，得到尺寸为92.21mm×66.68mm×5.099mm，容量为5900mAh的锂离子电池。
实施例2
与实施例1不同之处在于，负极单面区2102仅位于负极卷绕首层21a、负极卷绕首弧21b、负极卷绕次层21c、负极卷绕次弧21d和负极卷绕三层21e。
对比例1
与实施例1不同之处在于，卷绕后，负极单面区2102沿着卷绕方向D从负极卷绕次层21c延伸至负极卷绕三弧21f，即，负极单面区2102并未位于负极卷绕首层21a。同时省略第一层51。
对比例2
与实施例1不同之处在于，在第一方向D 1上，正极双面区起始端2202a与位于负极卷绕首层21a的负极单面区2102不重叠。同时省略第一层51。
然后，对实施例1和对比例1-2的电池分别进行初始能量密度测 试和析锂测试，然后测量位于第一虚拟线L 1和第二虚拟线L 2之间的电极组件20的厚度与对应于正极极耳40的电极组件20的厚度差。对应的测试结果记录于表1中。
其中，初始能量密度的计算公式为：初始能量密度(Wh/L)＝首次放电能量(Wh)÷[(电池长度(mm)×宽度(mm)×初始厚度(mm)]×1000000＝电池容量×放电平台÷(电池长度×宽度×初始厚度)。
析锂的测试步骤包括：(1)电池置于25℃±2℃的恒温箱中静置2小时；(2)对电池进行充电，具体为：以1.3C恒流充电至4.1V，恒压放电至1.0C、静置5min、1.0C恒流充电至4.2V，恒压放电至0.7C、静置5min、0.7C恒流充电至4.3V，恒压放电至0.4C、静置5min、0.4C恒流充电至4.45V，恒压放电至0.025C、静置5min；(3)对电池进行放电，具体为以0.5C恒流放电至3.0V，此为一次析锂测试循环；(4)重复500次上述析锂测试循环后，拆解电池并检查负极极片21于负极双面区起始端2103a附近(第一虚拟线L 1和第二虚拟线L 2之间所界定的范围内)的负极活性材料表面是否析锂；(5)重复500次上述析锂测试循环后，拆解电池并检查负极极片21于负极双面区起始端2103a附近(第一虚拟线L 1和第二虚拟线L 2之间所界定的范围内)的负极活性材料表面是否析锂。其中，若观察负极活性材料表面存在灰色区域则为析锂，若无灰色的地方则无析锂。其中，析锂程度分为轻微析锂、中度析锂以及严重析锂。轻微析锂为析锂区域小于为负极极片21整体区域的0.5％，中度析锂为析锂区域为负极极片21整体区域的0.5％～5.0％，严重析锂为析锂区域大于负极极片21整体区域的5.0％。
表1
Figure PCTCN2022113002-appb-000001
由表1数据可知，相较于对比例1-2，实施例1-2通过设置负极单面区2102位于负极卷绕首层21a并使在第一方向D 1上正极双面区起始端2202a与位于负极卷绕首层21a的负极单面区2102重叠，同时在负极卷绕首层21a上设置第一层51，使得在第一虚拟线L 1和第二虚拟线L 2之间的电极组件20被填充，因此位于第一虚拟线L 1和第二虚拟线L 2之间的电极组件20的厚度与对应于正极极耳40的电极组件20的厚度差异减小，即电池平整性提高，因此电池未产生析锂。
实施例3
与实施例1不同之处在于，第一层51不超过第一虚拟线L 1和第二虚拟线L 2之间所界定的范围。
实施例4
与实施例1不同之处在于，在第一方向D 1上，第一层51与正极极耳40重叠。
实施例5
与实施例1不同之处在于，负极单面区起始端2102a位于第二虚拟线L 2背离第一虚拟线L 1的一侧。
实施例6
与实施例1不同之处在于，第一层终止端51b在第二方向D 2上位于第一虚拟线L 1背离第二虚拟线L 2的一侧。
然后，对实施例3-6的电池分别进行初始能量密度测试和析锂测试，然后测量位于第一虚拟线L 1和第二虚拟线L 2之间的电极组件20的厚度与对应于正极极耳40的电极组件20的厚度之差。对应的测试结果记录于表2中。
表2
Figure PCTCN2022113002-appb-000002
从表2数据可知，相较于实施例1，由于实施例3中第一层起始端51a未超过第二虚拟线L 2背离第一虚拟线L 1的一侧，因此第一层51补偿第二虚拟线L 2与正极极耳40之间的电极组件20的厚度的能力不足，电池平整性相对降低，在经过1000次循环后产生轻度析锂。相较于实施例1、5-6，由于实施例4中第一层51与正极极耳40在 第一方向D 1上重叠，因此电池平整性降低，在经过1000次循环后产生轻度析锂。
实施例7-8
与实施例1不同之处在于，第一层51厚度不同。
然后，对实施例7-8的电池分别进行初始能量密度测试和析锂测试，然后测量位于第一虚拟线L 1和第二虚拟线L 2之间的电极组件20的厚度与对应于正极极耳40的电极组件20的厚度之差。对应的测试结果记录于表3中。
表3
Figure PCTCN2022113002-appb-000003
从表3数据可知，相较于实施例1，由于实施例7-8中第一层51厚度较大，使得对应于正极极耳40的电极组件20厚度与第一虚拟线L 1和第二虚拟线L 2之间的电极组件20厚度差异增大，因此实施例7-8电池平整性降低，电池产生析锂。其中实施例8中厚度差超过20μm，因此经过500次循环后产生轻度析锂，经过1000次循环后产生轻度析锂。
实施例9-26
针对实施例4的电池经过1000次循环后产生轻度析锂的情况，进一步设计实施例9-26以提升电池的动力学性能。实施例9-26与实施例4不同之处在于OI值、D峰和G峰的强度比值或锂盐浓度值。
然后，对实施例9-26的电池分别进行析锂测试，对应的测试结果记录于表4中。其中，由于实施例12的OI值过小，导致在制造过程中负极活性材料脱落，未制得负极极片。由于实施例20的D峰和G峰的强度比值过大，使得循环过程中石墨材料对电解液消耗过快，因此电池未能完成1000次循环测试。由于实施例26的锂盐浓度过高，容易导致在制造过程中电解液析晶，未制得电池。
表4
Figure PCTCN2022113002-appb-000004
根据表4，对比实施例4、实施例9至13可知，当设置OI值为5.0至20.0时，可以获得较好的500次循环和1000次循环性能；当进一步设置OI值5.0至13时，可以获得更好的1000次循环性能。对比实施例4、实施例14至20可知，当设置I D/I G的值为0.05至0.80时，可以获得较好的500次循环和1000次循环性能；当进一步设置I D/I G的值为0.30至0.80时，可以获得更好的1000次循环性能。对比实施例4、实施例21至26可知，当设置锂盐浓度为0.5mol/L至2.5mol/L时，可以获得较好的500次循环和1000次循环性能；当设置锂盐浓度为1.0mol/L至2.5mol/L时，可以获得更好的1000次循环性能。
以上所揭露的仅为本申请较佳实施方式而已，当然不能以此来限定本申请，因此依本申请所作的等同变化，仍属本申请所涵盖的范围。

Claims (22)

  1. 一种电化学装置，包括电极组件，所述电极组件包括层叠卷绕的负极极片和正极极片；所述负极极片包括依次层叠的第一负极活性材料层、负极集流体和第二负极活性材料层，所述第一负极活性材料层相较于所述第二负极活性材料层更靠近卷绕中心轴；所述正极极片包括依次层叠的第一正极活性材料层、正极集流体和第二正极活性材料层，所述第一正极活性材料层相较于所述第二正极活性材料层更靠近所述卷绕中心轴；其中，
    沿卷绕方向，所述负极集流体包括依次连接的负极空箔区、负极单面区和负极双面区，所述负极极片包括负极卷绕首层和负极卷绕次层；所述负极单面区设有所述第二负极活性材料层，所述负极单面区至少位于所述负极卷绕首层和所述负极卷绕次层；所述正极集流体包括正极双面区，所述正极双面区位于所述负极卷绕次层背离所述卷绕中心轴的一侧；所述正极双面区包括正极双面区起始端，在第一方向上，所述正极双面区起始端与位于所述负极卷绕首层的负极单面区重叠，所述第一方向为所述负极卷绕次层至所述负极卷绕首层的方向；
    所述负极极片还包括包含绝缘材料的第一层，所述第一层位于所述负极卷绕首层且从所述第一负极活性材料层上延伸至所述负极空箔区上。
  2. 如权利要求1所述的电化学装置，其中，在所述第一方向上，所述正极双面区起始端与所述第一层重叠。
  3. 如权利要求1所述的电化学装置，其中，所述正极集流体还包括正极空箔区，所述正极空箔区和所述正极双面区沿所述卷绕方向依次连接；所述正极极片包括正极卷绕首层和正极卷绕次层，所述正极双面区位于所述正极卷绕次层。
  4. 如权利要求3所述的电化学装置，其中，所述负极极片还包括负极卷绕首弧、负极卷绕次弧、负极卷绕三层、负极卷绕三弧和负极卷绕四层；沿卷绕方向，所述负极卷绕首层、所述负极卷绕首弧、所述负极卷绕次层、所述负极卷绕次弧、所述负极卷绕三层、所述负极卷绕三弧和所述负极卷绕四层依次连接；所述负极单面区从所述负极卷绕首层至少延伸至所述负极卷绕三弧，所述负极双面区包括负极双面区起始端，所述负极双面区起始端位于所述负极卷绕四层；
    所述负极卷绕首弧至所述负极卷绕次弧的方向为第二方向，所述第一方向垂直于所述第二方向，与所述第一方向和所述第二方向均垂 直的方向为第三方向。
  5. 如权利要求4所述的电化学装置，其中，所述正极极片还包括包含绝缘材料的第二层，所述第二层从所述第一正极活性材料层或所述第二正极活性材料层上延伸至所述正极空箔区上；所述第二层包括在所述卷绕方向上相对设置的第二层起始端和第二层终止端，所述第二层起始端位于所述正极空箔区；
    经过所述负极双面区起始端且沿所述第一方向延伸的线为第一虚拟线，经过所述第二层终止端且沿所述第一方向延伸的线为第二虚拟线；在所述第二方向上，所述第一虚拟线相较于所述第二虚拟线更靠近所述负极卷绕首弧；所述负极单面区包括负极单面区起始端，从所述第三方向观察，所述负极单面区起始端位于所述第一虚拟线和所述第二虚拟线之间，或所述负极单面区起始端在所述第二方向上位于所述第二虚拟线背离所述第一虚拟线的一侧。
  6. 如权利要求5所述的电化学装置，其中，所述电化学装置还包括正极极耳，所述正极极耳连接于所述正极空箔区的背离所述卷绕中心轴的表面，所述正极极耳位于所述正极卷绕首层，所述第二层延伸至所述正极卷绕首层并在所述第一方向上与所述正极极耳重叠。
  7. 如权利要求6所述的电化学装置，其中，在所述第一方向上，所述正极极耳与位于所述负极卷绕首层的负极单面区相离。
  8. 如权利要求6所述的电化学装置，其中，所述电化学装置还包括负极极耳和包含绝缘材料的第三层，所述负极极耳连接于所述负极空箔区的朝向所述卷绕中心轴的表面，所述负极极耳位于所述负极卷绕首层，所述正极空箔区包括正极空箔区起始端；所述第三层设于所述负极空箔区背离所述卷绕中心轴的表面，在所述第一方向上，所述第三层与所述负极极耳和所述正极空箔区起始端重叠。
  9. 如权利要求8所述的电化学装置，其中，所述正极极耳、所述负极极耳和所述正极空箔区起始端在所述第一方向上相离。
  10. 如权利要求5所述的电化学装置，其中，所述第二层设于所述正极空箔区背离所述卷绕中心轴的表面，所述第二层从所述第二正极活性材料层上延伸至所述正极空箔区上。
  11. 如权利要求10所述的电化学装置，其中，所述正极极片还包括包含绝缘材料的第四层，所述第四层设于所述正极空箔区朝向所述卷绕中心轴的表面，所述第二层从所述第一正极活性材料层上延伸至所述正极空箔区上。
  12. 如权利要求11所述的电化学装置，其中，所述第四层包括在 卷绕方向上相对设置的第四层起始端和第四层终止端，所述第四层起始端位于所述正极空箔区；从所述第三方向观察，所述第四层终止端位于所述第一虚拟线和所述第二虚拟线之间。
  13. 如权利要求4所述的电化学装置，其中，所述负极极片还包括包含绝缘材料的第五层，所述第五层设于所述负极卷绕次弧。
  14. 如权利要求1所述的电化学装置，其中，所述第一负极活性材料层包括第一负极活性材料，所述第一负极活性材料包括石墨，所述第二负极活性材料层包括第二负极活性材料，所述第二负极活性材料包括石墨；
    所述第一负极活性材料层或所述第二负极活性材料层的至少一者的X射线衍射图谱包括004衍射峰和110衍射峰，所述004衍射峰的峰面积与所述110衍射峰的峰面积的比值为所述第一负极活性材料层或所述第二负极活性材料层的OI值，所述OI值的范围为5.0至20.0。
  15. 如权利要求14所述的电化学装置，其中，所述OI的范围为5.0至13.0。
  16. 如权利要求1所述的电化学装置，其中，所述第一负极活性材料层或所述第二负极活性材料层的至少一者的拉曼光谱中位移范围为1255cm -1～1355cm -1与1575cm -1～1600cm -1的峰分别为D峰和G峰，所述D峰和所述G峰的强度比值范围为0.05至0.80。
  17. 如权利要求16所述的电化学装置，其中，所述D峰和所述G峰的强度比值范围为0.30至0.80。
  18. 如权利要求1所述的电化学装置，其中，所述电化学装置还包括电解液，所述电解液包含锂盐，所述锂盐在所述电解液中的浓度范围为0.5mol/L至2.5mol/L。
  19. 如权利要求18所述的电化学装置，其中，所述锂盐在所述电解液中的浓度范围为1.0mol/L至2.5mol/L。
  20. 如权利要求8所述的电化学装置，其中，所述第一层、所述第二层和所述第三层各自独立地包括基材层和粘接层。
  21. 如权利要求1所述的电化学装置，其中，所述第一层的厚度范围为1μm至50μm。
  22. 一种电子装置，其中，包括如权利要求1至21项中任一项所述的电化学装置。
PCT/CN2022/113002 2022-08-17 2022-08-17 电化学装置以及电子装置 WO2024036507A1 (zh)

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