WO2015156344A1 - リチウムイオン二次電池 - Google Patents
リチウムイオン二次電池 Download PDFInfo
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- WO2015156344A1 WO2015156344A1 PCT/JP2015/061062 JP2015061062W WO2015156344A1 WO 2015156344 A1 WO2015156344 A1 WO 2015156344A1 JP 2015061062 W JP2015061062 W JP 2015061062W WO 2015156344 A1 WO2015156344 A1 WO 2015156344A1
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- negative electrode
- separator
- positive electrode
- lithium ion
- ion secondary
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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
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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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
- H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/463—Separators, membranes or diaphragms characterised by their shape
- H01M50/466—U-shaped, bag-shaped or folded
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/463—Separators, membranes or diaphragms characterised by their shape
- H01M50/469—Separators, membranes or diaphragms characterised by their shape tubular or cylindrical
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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
- H01M2220/00—Batteries for particular applications
- H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
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- 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
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- 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
-
- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Definitions
- the present invention relates to a lithium ion secondary battery, and more particularly to a lithium ion secondary battery sealed with a film-shaped exterior material in which a thin plate-like positive electrode and a thin plate-like negative electrode housed in a bag-like or cylindrical separator are laminated.
- a battery pack containing a secondary battery having a large capacity is used for a device that uses a battery as a driving power source, such as an electric bicycle, an electric motorcycle, and an electric vehicle.
- a lithium ion secondary battery having a large volume energy density and mass energy density is suitable as a battery for a driving power source.
- Lithium ion secondary batteries are known to have a columnar shape in which a strip-like positive electrode and a strip-like negative electrode are laminated via a separator, and a flat one in which a thin plate-like positive electrode and a thin plate-like negative electrode are laminated via a separator. Yes.
- flat batteries can easily increase the capacity per unit battery by increasing the area of the positive and negative electrodes or increasing the number of positive and negative electrodes to be stacked. It is suitable as a battery for power supplies.
- a flat unit battery of a lithium ion secondary battery can effectively utilize the high energy density of the lithium ion secondary battery by covering the battery element with a film-like packaging material.
- the dimensions of the positive electrode, the separator, and the negative electrode are determined in order to prevent metallic lithium from precipitating in a dendrite shape due to current concentration at the corner of the negative electrode during charging. That is, the dimension of the separator is the largest in the stacking positional relationship between the positive electrode active material application part, the negative electrode active material application part, and the separator.
- the outer periphery of the separator is positioned outside the outer periphery of the positive electrode active material application portion and the negative electrode active material application portion.
- the dimension of the application part of a positive electrode active material is the smallest, and the outer periphery of the application part of a positive electrode active material is located inside the outer periphery of the application part of a separator and a negative electrode active material.
- a positive electrode and a negative electrode used for a lithium ion secondary battery are manufactured by applying and drying a slurry prepared by mixing particles of an active material and a conductive auxiliary agent with a binder, respectively. Accordingly, when subjected to an impact due to vibration, dropping, etc., there is a possibility that problems such as falling off of the active material and breakage of the electrode may occur.
- the outer periphery of the thin plate negative electrode is located closer to the outer package than the outer periphery of the thin plate positive electrode, so that the thin plate negative electrode is more resistant to external impacts. Is easily affected by contact with the exterior body.
- Patent Documents 1 and 2 if the outer periphery of the separator is positioned outside the portion excluding the non-applied portion of the active material, the separator exposed from the laminated body than the electrode is a buffer member if the impact is small. It can be expected to alleviate electrode breakage and active material loss.
- the positive electrode is accommodated in a bag-shaped separator, and the bag-shaped separator and the negative electrode containing the positive electrode are disposed.
- a bag-shaped separator By inserting the positive electrode into the bag-shaped separator, even if the positive electrode active material or the negative electrode active material falls off from the current collector, the bag-shaped separator prevents the active material from adhering to the counter electrode and prevents deterioration in quality. Can do. Since wrinkles due to thermal shrinkage tend to occur when a bag-shaped separator is produced, in Patent Document 3, generation of wrinkles is prevented by performing thermal welding of the separators at a predetermined interval.
- the heat welded portion disposed around the electrode is crystallized after the separator is softened or melted, the flexibility is lowered as compared with that before the heat weld. Therefore, when the welded portion comes into contact with the positive electrode when subjected to vibration or impact, the active material may fall off from the electrode. The fallen active material stays in the separator, but if it falls off in large quantities, the capacity is reduced. Also, if the electrode is cracked when the active material is removed, the separator may be damaged, which is not preferable.
- the present invention solves the above-described problems that occur when a bag-like or cylindrical separator is used. In addition, it prevents the positive electrode and the negative electrode from cracking due to vibration and impact. Then, it is possible to provide a battery that is more excellent in electrical characteristics and safety by reducing the falling off of the positive electrode active material and the negative electrode active material.
- An object of the present invention is to accommodate a thin plate-like positive electrode coated with a positive electrode active material, a thin plate-like negative electrode coated with a negative electrode active material and a battery element laminated via a separator, and an electrolytic solution in an exterior body,
- the outer periphery of the separator is positioned outside the outer periphery of the negative electrode, both of the concave and convex portions, and the outer periphery of the negative electrode is positioned outside the outer periphery of the positive electrode accommodated in the bag-shaped or cylindrical separator. It can be solved by a lithium ion secondary battery.
- the active material from both the positive electrode and the negative electrode is less likely to fall off and cracks are less likely to occur.
- the occurrence of cracks in the positive electrode and the negative electrode is reduced when subjected to vibration or impact, and the active material is less likely to fall off.
- a battery having excellent properties can be provided.
- FIG. 1 is a plan view showing the appearance of the lithium ion secondary battery of the present invention.
- FIG. 2 is a perspective view showing an assembly of battery elements of the lithium ion secondary battery of the present invention.
- FIG. 3 is a diagram showing an example of the positive electrode and the negative electrode of the lithium ion secondary battery of the present invention.
- FIG. 4 is a diagram for explaining an example of the bag-like separator of the lithium ion secondary battery diagram of the present invention and the positive electrode inserted therein.
- FIG. 5 is a view for explaining a laminated state of a bag-like separator into which a positive electrode of the lithium ion secondary battery of the present invention is inserted and a negative electrode.
- FIG. 1 is a plan view showing the appearance of the lithium ion secondary battery of the present invention.
- FIG. 2 is a perspective view showing an assembly of battery elements of the lithium ion secondary battery of the present invention.
- FIG. 3 is a diagram showing an example of the positive electrode and the negative electrode
- FIG. 6 is a diagram for explaining battery elements of the lithium ion secondary battery of the present invention.
- FIG. 7 is a diagram illustrating battery elements of the lithium ion secondary battery of the present invention.
- FIG. 8 is a diagram illustrating a state in which a bag-like separator into which a positive electrode of the lithium ion secondary battery of the present invention is inserted and a negative electrode are stacked.
- FIG. 9 is a diagram for explaining an outer package of one embodiment of the lithium ion secondary battery of the present invention.
- FIG. 1 is a plan view showing the appearance of the lithium ion secondary battery of the present invention.
- FIG. 2 is a perspective view showing an assembly of battery elements of the lithium ion secondary battery of the present invention.
- the battery element 4 is housed inside the outer package 10 together with the electrolytic solution.
- One end of each of the positive electrode terminal 2 and the negative electrode terminal 3 of the battery element is taken out from the outer package 10 as a positive electrode terminal exposed portion 2a and a negative electrode terminal exposed portion 3a.
- Each exposed portion functions as an external terminal for connecting to an external device or the like.
- a flexible film, a can case, or the like can be used for the exterior body, a roller using a flexible film is preferable from the viewpoint of reducing the weight of the battery.
- a film in which a heat welding layer is provided on the inner surface of the metal layer for preventing leakage of the electrolytic solution and moisture from the outside and a protective layer is provided on the outer surface can be used.
- polyethylene or the like is provided on the inner surface
- aluminum foil or stainless steel foil is provided on the metal layer
- a film of nylon or polyethylene terephthalate is formed on the outer surface.
- FIG. 2 shows an example in which four long fixing members are used to fix the battery element from one outermost layer to the other outermost layer through a side surface where the positive electrode terminal and the negative electrode terminal are not provided. However, it can be appropriately set according to the size of the electrode, the number of stacked layers, and the like.
- FIG. 3 is a diagram for explaining the thin plate-like positive electrode and the thin plate-like negative electrode used for the battery element described in FIG. 2, in which FIG. 3A shows the positive electrode 6 and FIG. 3B shows the negative electrode.
- the positive electrode includes a positive electrode active material application part 6a in which an active material is applied to a positive electrode current collector, and a positive electrode active material non-application part 6b in which no active material is applied in order to connect electrode terminals.
- the negative electrode includes a negative electrode active material application part 7a and a negative electrode active material non-application part 7b.
- LiCoO2, LiNiO2, LiNiyCo1-yO2 (y 0.01 to 0.99)
- LiMnO2, LiMn2O4, LiNixCoyMnzO2 (x + y + z 1)
- LiFePO4 M is Fe, Mn, Ni
- Li 2 Examples thereof include lithium transition metal composite oxides such as MPO 4 F (M is Fe, Mn, Ni) and the like, and one or more of these can be used in combination.
- Examples of the negative electrode active material include carbon materials such as graphite, amorphous carbon, and carbon nanotubes, lithium metal materials, alloy materials such as silicon and tin, oxide materials such as Nb2O5 and TiO2, or composites thereof. Can be used.
- As the positive electrode current collector aluminum, stainless steel, nickel, titanium, or an alloy thereof can be used, and aluminum is particularly preferable.
- As the negative electrode current collector copper, stainless steel, nickel, titanium, or an alloy thereof can be used.
- FIG. 4 is a diagram for explaining how the thin plate-like positive electrode is inserted into a bag-like or cylindrical separator.
- the separator 8 at least the side 8a for inserting the thin plate-like positive electrode is opened in the peripheral portion where the two rectangular separators are stacked.
- Side 8b and side 8d adjacent to side 8a are closed by heat welding or folding.
- a bag-like separator is formed, and when the side 8c is opened, a cylindrical separator is formed.
- a polyolefin-based separator is preferably used as the separator.
- polypropylene, polyethylene, or a single layer or a combination of these in combination can be used.
- the shrinkage rate differs greatly depending on the difference in the in-plane direction.
- the direction in which the shrinkage rate is small has an opening for inserting an electrode, that is, an active material for connecting electrode terminals. It is preferable to match the direction in which the non-applied part exists.
- ⁇ Separator may not be welded to the end of the separator in the direction of taking out the terminal. Even in this case, it is possible to prevent a situation in which the separator is greatly contracted when the battery is abnormal and the non-coated portion of the active material is exposed.
- FIG. 4B is a diagram for explaining in detail the state of thermal welding of a portion surrounded by a broken line S1 in FIG. 4A.
- the separator is thermally welded at predetermined intervals.
- the heat welding part 8z is provided in the edge part or the edge part vicinity of a separator so that the convex part 8x and the recessed part 8y may arise in the outer periphery of a separator.
- FIG. 4B shows a comb-like shape, the uneven shape may be a wave shape or a combination of a straight line and a curve.
- the average value w1 of the difference between the apex of the adjacent convex portion and the concave portion is 0.3 mm or more and 3 mm or less. The reason for this will be described later with reference to FIG.
- FIG. 5 is an exploded view for explaining a laminated state of the thin plate-like positive electrode 6 and the thin plate-like negative electrode 7 accommodated in the bag-like separator.
- the two layers of the thin plate-like positive electrode inserted into the bag-like separator Only three layers are shown.
- a thin plate positive electrode 6 and a thin plate negative electrode 7 accommodated in a bag-like separator 8 are prepared, and the thin plate positive electrode 6 and the thin plate negative electrode 7 are alternately laminated.
- the non-applied parts of the positive electrode are drawn out from the same side, and the non-applied part of the negative electrode is drawn out from the same side.
- the non-applied portion of the positive electrode and the non-applied portion of the negative electrode do not have to be arranged on opposite sides.
- the width of the non-applied part of the positive electrode and the negative electrode or the take-out position is changed, the non-applied part of the positive electrode and the non-applied part of the negative electrode can be arranged on the same side.
- FIG. 6 is a diagram illustrating a battery element in which a thin plate positive electrode and a thin plate negative electrode housed in a bag-shaped separator are stacked.
- the thin plate-like positive electrode and the thin plate-like negative electrode 7 accommodated in the bag-like separator 8 are alternately positioned while being positioned at their respective ends by making the outer dimensions of the bag-like separator 8 and the outer dimensions of the thin-plate negative electrode 7 the same.
- a predetermined number can be sequentially stacked.
- FIG. 7 is a diagram illustrating a battery element that has been assembled. After laminating the laminated body of the thin plate-like positive electrode and the thin plate-like negative electrode housed in the bag-like separator, the laminated member is fixed from one end of one laminated surface to the opposite laminated surface with a fixing member 5 such as an adhesive tape. By passing through the above process, the battery element 4 in which the thin plate-shaped positive electrode and the thin plate-shaped negative electrode housed in the bag-shaped separator are not displaced can be produced.
- FIG. 8 is a schematic diagram for explaining the positional relationship among the thin plate positive electrode, the thin plate negative electrode, and the separator.
- FIG. 8A is a view as seen from a direction perpendicular to the laminated surface when a bag-like separator containing a thin plate-like positive electrode and a thin plate-like negative electrode sheet are laminated
- FIG. 8B is a broken line S2 in FIG. 8A. It is the figure which expanded the enclosed part. As shown in FIG.
- the battery element of the lithium ion secondary battery of the present invention is the outer periphery of the bag-like separator, and both the convex portion 8x and the concave portion 8y generated by heat welding are the outer peripheral portion 70 of the thin plate negative electrode and It arrange
- the convex portion 8x comes into contact with the exterior body.
- the convex portion 8x serves as a cushioning material. It is preferable that the average value w1 of the difference in apex between the adjacent convex portion 8x and the concave portion 8y is 0.3 mm or more and 3 mm or less, and the convex portion width x1> the concave portion width y1.
- the convex portion 8x can mitigate the impact on the end portion 70 of the negative electrode sheet and prevent the negative electrode sheet from being damaged or the negative electrode active material from falling off.
- the impact on the recess 8y is also reduced, the impact on the end portion 60 of the positive electrode sheet adjacent thereto can also be reduced.
- the heat-welded part of the bag-shaped or cylindrical separator is formed on at least one of the long sides adjacent to the side surface from which the positive electrode terminal or the negative electrode terminal is taken out, and when the battery element is formed, Of these, it is particularly effective to set the area of formation by the convex portion to 4 mm 2 or more.
- the separator may be bent along the electrode when the adhesive tape is applied.
- the separator is too large, the buffer density is improved, but the energy density per unit volume as a lithium ion secondary battery is lowered. Accordingly, it is possible to prevent the energy density from being lowered by arranging the welded portion 8z and the outer peripheral side of the negative electrode sheet so as to overlap each other. Moreover, since the separator is not bent along the outer periphery of the negative electrode even when a tape for fixing the laminated body is attached to the side surface, it is possible to prevent a decrease in buffering properties.
- FIG. 9 is a diagram for explaining a flexible exterior body in which a film having good heat-weldability is laminated on one surface of an aluminum film and a synthetic resin film having high strength is laminated on the other surface.
- a battery element housing portion 9 for housing battery elements is formed on the flexible exterior body 10 by pressing or the like.
- the battery element can be sealed by bonding two flexible exterior bodies 10 together.
- the battery element may be sealed so that one flexible outer package 10 is folded back.
- it can replace with a film-form exterior body and can have a battery element accommodating part inside by drawing process etc. of the board
- FIG. 9 is a diagram for explaining a flexible exterior body in which a film having good heat-weldability is laminated on one surface of an aluminum film and a synthetic resin film having high strength is laminated on the other surface.
- a battery element housing portion 9 for housing battery elements is formed on the flexible exterior body 10 by pressing or the like.
- the battery element can be sealed by bonding two flexible exterior bodies 10 together.
- FIG. 1 shows a battery element housing portion formed in the exterior body with a battery element, an electrolytic solution, and a part of the positive electrode terminal and a part of the negative electrode terminal electrically connected to the battery element, which are sealed. A lithium ion secondary battery is completed.
- Example 1 Two separators composed mainly of polypropylene with a thickness of 25 ⁇ m are stacked, with 3 mm on the periphery and a width of 0.5 mm along the outer periphery at an interval of 3 mm, and a width of 2 mm in the vertical direction.
- the distance difference w1 was intermittently heat-welded with a dimension of 0.4 mm to produce a bag-shaped separator having irregularities on the outer periphery.
- a thin plate-like positive electrode made of aluminum foil having a longitudinal dimension of the positive electrode active material application portion of 120 mm, a vertical dimension of 65 mm, and a thickness of 20 ⁇ m is inserted into the bag-shaped separator, and is opened from the opening of the bag.
- the non-coated portion of the positive electrode active material was exposed.
- the coating layer of the positive electrode active material is made of 130 ⁇ m of a slurry obtained by mixing 40% by mass of lithium nickelate and 51% by mass of lithium manganate with 3% by mass of carbon black as a conductive additive and 6% by mass of PVdF as a binder. It was applied by thickness, dried and compressed.
- a negative electrode made of copper foil having a longitudinal dimension of 125 mm, a perpendicular dimension of 68 mm, and a thickness of 10 ⁇ m was used for the negative electrode active material application portion of the thin plate negative electrode.
- a slurry mixed with 91% by mass of graphite, 3% by mass of carbon black as a conductive auxiliary agent, and 6% by mass of PVdF as a binder was applied to the active material application part of the thin plate negative electrode to a thickness of 100 ⁇ m and dried. A thing was used.
- the laminate was fixed so as not to be displaced.
- electrode terminals were attached, and 10 lithium ion secondary batteries housed in an outer package made of a film-shaped outer package together with an electrolytic solution containing cyclic carbonate and LiPF6 were produced.
- Example 2 Except for the point that w1 was set to 0.3 mm in Example 1, the same measurement was performed by changing Example 1, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
- Comparative Example 1 A lithium ion secondary battery was fabricated and tested in the same manner as in Example 1 except that the heat welding conditions were changed from Example 1 and the difference w1 in the distance between the adjacent convex part and the apex of the concave part was 0.2 mm. And shown in Table 1.
- the lithium ion secondary battery of the present invention has irregularities formed on the outer periphery of the separator containing the thin plate positive electrode, and both the concave and convex portions are located outside the outer periphery of the negative electrode. It is possible to provide a lithium ion secondary battery having excellent characteristics that do not have a significant influence on the battery.
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Abstract
Description
リチウムイオン二次電池には帯状正極と帯状負極をセパレーターを介して積層したものを卷回した柱状のもの、薄板状正極と薄板状負極をセパレーターを介して積層した扁平状のものが知られている。
扁平状のリチウムイオン二次電池の単位電池は、電池要素をフィルム状外装材で外装することによって、リチウムイオン二次電池の有する高エネルギー密度を有効に利用することができる。
リチウムイオン二次電池に用いる正極電極や負極電極は、それぞれ活物質、導電性助剤の粒子を結着剤と混合して作製したスラリーを塗布、乾燥して製造している。したがって、振動や落下等による衝撃を受けると、活物質の脱落、電極の破断といった不具合を発生するおそれがあった。
一方、特許文献1、2のように、セパレータの外周が活物質の非塗布部を除いた部分よりも外側に位置すれば、小さな衝撃であれば積層体から電極よりも露出したセパレータが緩衝部材の役割を果たし、電極の破断や活物質の脱落を緩和することが期待できる。
正極電極を袋状セパレータに挿入することで、正極活物質や負極活物質が集電体から脱落しても、袋状セパレータによって対極に活物質が付着するのを防ぎ、品質の低下を防ぐことができる。
袋状セパレータを作製するときには熱収縮に起因したしわが生じやすくなるため、特許文献3ではセパレータの熱溶着を所定間隔を設けて行うことでしわの発生を防いでいる。
また、熱溶着によって作製した袋状または筒状のセパレータでは、電極を収容する部分の寸法は、電極を収容できる程度に電極の外形寸法よりもわずかに大きなものとして作製している。しかしながら、セパレータは熱収縮を起こすために両者の寸法は、ほぼ同一となることがある。
脱落した活物質はセパレータ内に留まるものの、大量に脱落すれば容量低下を引き起こす。また、活物質の脱落の際に電極にクラックが発生するようなことがあればセパレータを傷つける可能性があり好ましくない。
本発明は、袋状または筒状セパレータを用いた場合に生じる前述した問題を解決するものである。また、振動や衝撃によって正極および負極にクラックが発生することを防止するものである。そして、正極活物質および負極活物質の脱落を低減し、より電気特性や安全性に優れた電池を提供するものである。
図1は、本発明のリチウムイオン二次電池の外観を示す平面図である。また、図2は、本発明のリチウムイオン二次電池の電池要素の組立体を示す斜視図である。
リチウムイオン二次電池1は、電池要素4を外装体10の内部に電解液と共に密封して収容している。電池要素の正極端子2、負極端子3のそれぞれの一端部を正極端子露出部2a及び負極端子露出部3aとして、外装体10から取り出している。それぞれの露出部は外部機器等と接続するための外部端子として機能する。
電池要素4の正極端子と負極端子を設けていない側面には、袋状または筒状セパレータに収容して積層した正極電極と負極電極が位置ずれを生じないようにするためにテープ等の固定部材5を設けることが好ましい。
図2では長尺の4枚の固定部材を用いて電池要素の一方の最外層から他方の最外層までを正極端子と負極端子を設けていない側面を介して固定している例を示しているが、電極の大きさ、積層枚数等に応じて適宜設定することができる。
正極は、正極集電体に活物質を塗布した正極活物質塗布部6aと、電極端子を接続するために活物質を塗布していない正極活物質非塗布部6bとを備えている。負極も同様に、負極活物質塗布部7aと負極活物質非塗布部7bとを備えている。
正極活物質としては、LiCoO2、LiNiO2、LiNiyCo1-yO2(y=0.01~0.99)、LiMnO2、LiMn2O4、LiNixCoyMnzO2(x+y+z=1)、LiFePO4(MはFe、Mn、Ni)、又はLi2MPO4F(MはFe、Mn、Ni)等のリチウム遷移金属複合酸化物などが挙げられ、これらの1種または2種以上を混合して使用することができる。
正極集電体としてはアルミニウム、ステンレス鋼、ニッケル、チタンまたはこれらの合金等を用いることができ、特にアルミニウムが好ましい。負極集電体としては銅、ステンレス鋼、ニッケル、チタンまたはこれらの合金を用いることができる。
セパレータ8は、2枚の矩形状のセパレータを重ねた周縁部のうち、少なくとも薄板状正極を挿入するための辺8aは開口している。辺8aと隣接する辺8bおよび辺8dが熱溶着または折り返しによって閉じられている。正極端子6aを取り出す辺8aに対向する辺8cを熱溶着または折り返しによって閉じると袋状セパレータとなり、辺8cを開口しておくと筒状のセパレータとなる。
セパレータは外周を熱溶着する際に生じる熱収縮によりセパレータにシワが入ることを防ぐために、外周を所定間隔ごとに熱溶着している。本発明においては、セパレータの外周に凸部8xや凹部8yが生じるように、セパレータの端部または端部近傍に熱溶着部8zを設けている。
図4(b)では櫛歯状の形状を記載しているが、凹凸の形状は波状や直線と曲線とを組み合わせたものでも良い。その際、隣り合う凸部と凹部の頂点の差の距離の平均値w1は0.3mm以上、3mm以下とすることが好ましい。この理由については後述する図8において説明する。
袋状のセパレータ8に収容した薄板状正極6と薄板状負極7とを準備し、薄板状正極6と薄板状負極7とを交互に積層したものである。
正極の非塗布部同士は同じ側面から引き出すようにし、負極の非塗布部士も同じ側面から引き出すようにしている。一方、図のように正極の非塗布部と負極の非塗布部とは互いに対向する辺に配置する必要はない。例えば、正極と負極の非塗布部の幅、あるいは取り出し位置が変えるならば、正極の非塗布部と負極の非塗布部を同じ辺に配置することも可能である。
袋状セパレータ8に収容した薄板状正極と薄板状負極7は、袋状セパレータ8の外形寸法と薄板状負極7の外形寸法を同一の寸法とすることで、それぞれの端部で位置決めしながら交互に所定の数を順次積層することができる。
袋状セパレータに収容した薄板状正極と薄板状負極の積層体を積層した後に、積層体の一方の積層面の一端から反対側の積層面へと粘着テープ等の固定部材5で固着する。
以上の工程を経ることで、袋状セパレータに収容した薄板状正極と薄板状負極とが位置ずれを起こすことがない電池要素4を作製することができる。
図8Aは、薄板状正極を収容した袋状セパレータと、薄板状負極シートとを積層したときに、積層面に対して垂直方向から見た図であり、図8Bは、図8Aの破線S2で囲んだ部分を拡大した図である。
図8Bに示すように、本発明のリチウムイオン二次電池の電池要素は、袋状セパレータの外周であり熱溶着によって生じた凸部8x、凹部8yのいずれもが薄板状負極の外周部70および薄板状正極の外周部60よりも外側に位置するように配置している。
隣り合う凸部8xと凹部8yとの頂点の差の距離の平均値w1を0.3mm以上、3mm以下、凸部の幅x1>凹部の幅y1とすることが好ましい。
袋状または筒状のセパレータにおける熱溶着される部分は、正極端子や負極端子を取り出す側面に隣接する長手の辺のうちの少なくとも一方に形成し、電池要素を形成したときに、一個の側面のうち凸部によって形成の面積を4mm2以上とするのが特に効果的である。
可撓性外装体10に対してプレス加工等によって電池要素を収容する電池要素収容部9を形成したものである。
図9Aのように2枚の可撓性外装体10を貼りあわせるようにして電池要素を封口することができる。また、図9Bのように1枚の可撓性外装体10を折り返すようにして電池要素を封口しても良い。
また、フィルム状外装体に代えて、アルミニウムの板の絞り加工等によって内部に電池要素収容部を有する形成することができる(図示せず)。
外装体に形成された電池要素収容部に、電池要素、電解液ならびに電池要素に電気的に接続された正極端子の一部および負極端子の一部を収容し、密閉することで図1に示すリチウムイオン二次電池が完成する。
厚さ25μmのポリプロピレンを主成分とするセパレータを2枚重ね、周囲3辺を3mmの間隔で外周辺に沿った幅0.5mm、それと垂直方法の幅2mmとし、隣合う凸部と凹部の頂点の距離の差w1を0.4mmの寸法で間欠的に熱溶着して、外周部に凹凸を設けた袋状セパレータを作製した。
袋状セパレータの内部に正極活物質の塗布部の長手方向の寸法が120mm、これに垂直な方向の寸法が65mm、厚さ20μmのアルミニウム箔製の薄板状正極を挿入し、袋の開口部からは正極活物質の非塗工部が露出するようにした。正極活物質の塗布層は、ニッケル酸リチウム40質量%とマンガン酸リチウム51質量%を導電性助剤としてカーボンブラックを3質量%、および結着剤としてPVdFを6質量%混合したスラリーを130μmの厚さで塗布し、乾燥して圧縮したものを用いた。
薄板状負極の活物質塗布部には黒鉛91質量%、導電性助剤としてカーボンブラック3質量%、結着剤としてPVdFを6質量%を混合したスラリーを100μmの厚さで塗布し、乾燥したものを用いた。
薄板状正極、薄板状負極および袋状セパレータの位置関係は、袋状セパレータの外周部よりも負極シートの外周部の方がセパレータよりも内側になるように配置し、袋状セパレータの内部に収容した正極シートの外周部のほうが負極シートよりも内側になるように配置した。
その後、電極端子を取り付け、環状カーボネート、LiPF6を含む電解液と共にフィルム状外装材からなる外装体に収容したリチウムイオン二次電池を10個作製した。
作製した10個の二次電池を積層方向を地面と平行に向け、端子を取り出している辺とは異なる2側面をそれぞれの方向からコンクリートの床に落下させることで、正極シートや負極シートからの活物質の脱落を確認し、試験結果を表1に示す。
実施例2
実施例1においてw1を0.3mmとした点を除き実施例1変えて同様の測定をして、実施例1と同様に評価を行い、その結果を表1に示す。
実施例1と熱溶着条件を変え、隣合う凸部と凹部の頂点の距離の差w1を0.2mmとした以外の点は、実施例1と同様にリチウムイオン二次電池を作製し、試験を行い表1に示す。
正極活物質脱落状況 正極活物質脱落量
実施例1 0/10 0/10
実施例2 0/10 0/10
比較例1 2/10 1/10
2・・・正極端子
2a・・・正極端子露出部
3・・・負極端子
3a・・・負極端子露出部
4・・・電池要素
5・・・固定部材
6・・・薄板状正極
6a・・・正極活物質塗布部
6b・・・正極活物質非塗布部
7・・・薄板状負極
7a・・・負極活物質塗布部
7b・・・負極活物質非塗布部
8・・・セパレータ
8a,8b,8c,8d・・・辺
8x・・・凸部
8y・・・凹部
8z・・・熱溶着部
10・・・外装体
w1・・・頂点の差の距離の平均値
x1・・・凸部の幅
y1・・・凹部の幅材
60・・・正極シートの端部
70・・・負極シートの端部
Claims (4)
- 正極活物質を塗布した薄板状正極、負極活物質を塗布した薄板状負極およびセパレータを介して積層した電池要素と、電解液とを外装体に収容した積層型のリチウムイオン二次電池において、前記セパレータは、外周の少なくとも一辺が間欠的に熱溶着した扁平の袋状また扁平の筒状であって、前記熱溶着した辺には直線、曲線、または直線及び曲線で形成した凹凸を備え、前記凹凸で形成したセパレータの外周は、凹部および凸部ともに前記負極の外周よりも外側に位置し、前記負極の外周は、前記袋状または筒状のセパレータに収容した正極の外周よりも外側に位置することを特徴とする積層型リチウムイオン二次電池。
- 前記熱溶着された辺における熱溶着部が、前記負極の外周と重なる位置で積層したことを特徴とする請求項1に記載の積層型リチウムイオン二次電池。
- 前記電池要素には固定部材を取り付けており、
前記固定部材は、少なくとも前記凹凸が形成された辺が位置する面に配置したことを特徴とする請求項1または2に記載の積層型リチウムイオン二次電池。 - 前記凹部と凸部の頂点の距離の差が、0.3mm以上3mm以下であることを特徴とする請求項1~3のいずれか1項に記載の積層型リチウムイオン二次電池。
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| JP2024516990A (ja) * | 2022-01-14 | 2024-04-18 | エルジー エナジー ソリューション リミテッド | 二次電池製造装置および二次電池製造方法 |
| JP7729020B2 (ja) | 2022-01-14 | 2025-08-26 | エルジー エナジー ソリューション リミテッド | 二次電池製造装置および二次電池製造方法 |
| JP2024520346A (ja) * | 2022-04-29 | 2024-05-24 | エルジー エナジー ソリューション リミテッド | 吸熱体を内蔵する角型二次電池 |
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| Publication number | Publication date |
|---|---|
| CN106463779B (zh) | 2019-02-26 |
| JPWO2015156344A1 (ja) | 2017-04-13 |
| US10164233B2 (en) | 2018-12-25 |
| JP6497751B2 (ja) | 2019-04-10 |
| US20170110703A1 (en) | 2017-04-20 |
| CN106463779A (zh) | 2017-02-22 |
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