JP2010135265A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery for making long-period reliability and the output characteristics improve. <P>SOLUTION: In the nonaqueous electrolyte secondary battery having a battery element including a unit cell layer in which a positive electrode in which a positive electrode active material layer is formed on a surface of a current collector, a negative electrode in which a negative electrode active material layer is formed on the surface of the current collector are laminated via an electrolyte layer; and compressive stress, when an electrolyte (1) used for the negative electrode active material layer is strained by 50%, is smaller than that when the electrolyte (2) used for the positive electrode active material layer, is strained by 50%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nonaqueous electrolyte secondary battery, an assembled battery using the battery, and a vehicle. In particular, the present invention relates to a non-aqueous electrolyte secondary battery excellent in long-term reliability and output characteristics, and an assembled battery and a vehicle using the battery.

  In recent years, in order to cope with air pollution and global warming, reduction of the amount of carbon dioxide has been eagerly desired, and the automobile industry is no exception. Expectations have been gathered for the reduction of carbon dioxide emissions through the introduction of electric vehicles and hybrid electric vehicles, and motor-driven secondary batteries that hold the key to their practical use are being actively developed.

  As a secondary battery for driving a motor, a lithium ion secondary battery having the highest theoretical energy among all the batteries is attracting attention, and is currently being developed rapidly. In general, a lithium ion secondary battery has a positive electrode obtained by applying a positive electrode active material or the like to a positive electrode current collector and a negative electrode obtained by applying a negative electrode active material or the like to a negative electrode current collector via a liquid or solid electrolyte layer, It has the structure accommodated in a battery case.

  In such a lithium ion secondary battery, as a development trend, high energy density and high output of the battery are demanded, and development of a thin battery is progressing as a countermeasure. As a technique for obtaining such a thin and light battery, there is a polymer battery in which the electrolyte portion that is a solution is made solid to reduce the thickness.

  On the other hand, in such a polymer battery, an alloy material or a carbonaceous material is used as an electrode active material. However, with the charge / discharge reaction, the electrode active material expands and contracts as the lithium ions are stored and released. For example, when a carbon-based negative electrode active material such as graphite is used, the volume change is approximately 10% with respect to the interlayer distance, and with an alloy-based active material, the volume change is nearly 200% with respect to the electrode volume. When a polymer solid electrolyte or a gel electrolyte containing an electrolytic solution component is used for these electrodes, contact between the interfaces decreases or the expansion and contraction of the electrodes may decrease as the electrolyte is repeatedly charged and discharged. Acts as a pressure on the layer. For this reason, the electrolytic solution is locally insufficient or the electrolytic solution oozes out, resulting in a decrease in long-term reliability of the battery. Further, the use of a polymer solid electrolyte or a gel electrolyte containing an electrolytic solution component causes a problem that diffusion is reduced and output characteristics are lowered as compared with a non-aqueous secondary battery using only an electrolytic solution.

In order to solve such a problem, for example, Patent Document 1 reports using an electrolyte layer containing a gel electrolyte in a structure having a certain mechanical strength. According to Patent Document 1, the output characteristics are improved by improving the retention of the electrolyte contained in the gel electrolyte.
JP-A-11-354160

  However, in Patent Document 1, since a mechanism for gas generation on the negative electrode side is not provided, peeling of the negative electrode interface occurs due to expansion and contraction of the negative electrode, which causes a problem in long-term reliability. In addition, Patent Document 1 has a problem that the target output characteristics are low because the conductivity of the gel electrolyte is low.

  Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide a non-aqueous secondary battery that improves long-term reliability and output characteristics.

  As a result of intensive studies to solve the above problems, the present inventors have obtained a non-aqueous electrolyte secondary battery using an electrolyte that makes the negative electrode active material layer softer than the positive electrode active material layer. It has been found that the above problems can be solved, and the present invention has been completed.

  According to the present invention, peeling at the negative electrode interface can be suppressed / prevented by efficiently releasing the gas generated in the negative electrode. For this reason, a non-aqueous secondary battery with improved long-term reliability and output characteristics can be obtained.

  In the present invention, a positive electrode in which a positive electrode active material layer is formed on the surface of a current collector and a negative electrode in which a negative electrode active material layer is formed on the surface of the current collector are stacked via an electrolyte layer. A nonaqueous electrolyte secondary battery having a battery element including a battery layer, wherein compressive stress at 50% strain of the electrolyte (1) used in the negative electrode active material layer is used in the positive electrode active material layer Provided is a nonaqueous electrolyte secondary battery having a smaller compressive stress at the time of 50% strain of the electrolyte (2).

  In non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries, air that has entered the interior of the battery element when packaged or air that remains adsorbed in the pores of the negative electrode, during the first charge and discharge, Bubbles are generated. In addition, even though it is non-aqueous, since a small amount (ppm order) of water exists in the battery, the lithium ion secondary battery using a carbon-based material as the negative electrode active material is charged for the first time after assembly. Then, due to the reaction inside the battery, water is decomposed to generate hydrogen and oxygen. Furthermore, during the formation of a coating on the negative electrode surface, gas such as hydrocarbons and carbon oxides (for example, carbon dioxide) increases due to the increase in electrical resistance and decomposition of the electrolyte solution (for example, hydrolysis of lithium salt, which is an electrolyte salt). Will occur. In the conventional polymer battery, since the flexibility of the interface between the negative electrode active material layer and the electrolyte layer is low, the gas hardly moves. If such a gas is left inside the battery, the battery swells or the internal pressure of the battery rises, and the gas pushes up the active material layer to cause peeling from the electrode, which adversely affects the laminated structure. That is, the presence of gas in the battery can cause deterioration of characteristics such as charge / discharge characteristics and battery life. Further, in the portion where the gas is generated in this way, the movement of lithium ions is hindered, which may cause a decrease in battery characteristics. As described above, it is necessary to take measures to solve various problems caused by the gas generated at the negative electrode interface.

  On the other hand, in the present invention, the negative electrode active material layer uses an electrolyte (1) having a low compressive stress at the time of 50% strain. Thus, by providing the negative electrode active material layer with flexibility having a large shape change, even if gas is generated at the negative electrode interface, the gas can be easily moved without remaining at the generation site and escapes from the reaction site. Therefore, by taking such a structure, various problems due to gas generation can be reduced.

In addition, as described above, in a polymer battery using a solid polymer electrolyte or a gel electrolyte containing an electrolytic solution component, the electrode active material expands and contracts as the lithium ions are occluded and released along with the charge / discharge reaction. When the charge / discharge cycle is repeated in such a state, the contact at the interface is lowered, or the expansion / contraction of the electrode acts as a pressure on the electrolyte layer. For this reason, the electrolytic solution is locally insufficient or the electrolytic solution oozes out, resulting in a decrease in long-term reliability of the battery. In particular, when silicon (Si) is used for the negative electrode active material, the amount of lithium in the active material increases due to alloying with Li due to charging, and the Li ₁₅ Si ₄ composition is in a so-called amorphous state. The volume change is relatively small, and it is a stable region. When the battery is further charged, the amount of lithium exceeds the Li ₁₅ Si ₄ composition, changes from an amorphous state to a crystalline state, reaches an unstable region, and at that time, a significant volume expansion occurs. Conversely, a large volume of shrinkage occurs. Such expansion and contraction causes particle collapse (miniaturization), and deterioration of the electrode proceeds. That is, due to the collapse of the active material particles due to expansion and contraction, a part of the active material is cut off from the flow of electrons to the current collector, and thus cannot contribute to the battery reaction.

  On the other hand, in the present invention, the electrolyte (1) having a low compressive stress at the time of 50% strain is used for the negative electrode, thereby giving the negative electrode active material layer flexibility with a large form change. Thereby, even if expansion | swelling shrinkage | contraction occurs with an electrode, especially a negative electrode, since a negative electrode active material layer is soft, expansion | swelling shrinkage | contraction can be absorbed here. For this reason, this invention is effective in suppression and prevention of the fall of battery performance.

  On the other hand, in the present invention, the positive electrode active material layer uses an electrolyte (2) having a high compressive stress at 50% strain as compared with the negative electrode active material layer. As described above, on the positive electrode side, as much gas is not generated as compared with the negative electrode, various problems due to gas generation and expansion / contraction are unlikely to occur. On the contrary, the retention property of the gel electrolyte in the active material layer can be improved by making the positive electrode active material layer have a hard structure with little change in shape. For this reason, liquid leakage and a short circuit can be suppressed and prevented, the lifetime of a battery can be extended, and long-term reliability can be ensured.

  Hereinafter, embodiments of the lithium ion battery of the present invention will be described with reference to the drawings. However, the technical scope of the present invention should be determined based on the description of the claims, and only in the following forms: Not limited. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  First, since the nonaqueous electrolyte secondary battery according to the present invention has a large capacity and is excellent in long-term reliability and output characteristics, it can be suitably used as a drive power source for vehicles. In addition to this, the present invention can be sufficiently applied to non-aqueous electrolyte secondary batteries for portable / mobile devices such as mobile phones and notebook computers that are strongly required to be small in size and have a high capacity.

  The lithium ion battery that is the subject of the present invention is, for example, any conventionally known form / structure, such as a stacked (flat) battery or a wound (cylindrical) battery, when distinguished by form / structure. Is also applicable. By adopting a stacked (flat) battery structure, long-term reliability can be secured by a sealing technique such as simple thermocompression bonding, which is advantageous in terms of cost and workability.

  Also, when viewed in terms of electrical connection (electrode structure) in a lithium ion battery, it can be applied to both non-bipolar (internal parallel connection type) batteries and bipolar (internal series connection type) batteries. is there. Of these, bipolar batteries are preferred because they have the advantage of having a higher power density and higher voltage than stacked batteries. A stacked battery takes lead wires from each of a positive electrode and a negative electrode, and is connected to an adjacent battery via the lead wires. For this reason, the conduction path of electrons becomes longer corresponding to the length of the lead wire, and the output of the battery is lowered. On the other hand, in the bipolar battery, current flows in the vertical direction (electrode stacking direction) through the current collector, so that the electron conduction path can be shortened and the output is high. Thereby, a battery with a high battery voltage can be constituted.

  When distinguished by the type of electrolyte in the lithium ion battery, any of the conventionally known ones such as a solution electrolyte type battery using a solution electrolyte such as a non-aqueous electrolyte for the electrolyte, a polymer battery using a polymer electrolyte for the electrolyte, etc. It can also be applied to electrolyte types. It is preferably applied to a polymer battery using a polymer electrolyte as an electrolyte. The polymer battery is further divided into a gel electrolyte type battery using a polymer gel electrolyte (also simply referred to as a gel electrolyte) and a solid polymer (all solid) type battery using a polymer solid electrolyte (also simply referred to as a polymer electrolyte). It is done. Among them, polymer batteries, especially solid polymer (all solid) batteries, do not cause liquid leakage, so there is no problem of liquid junction, high reliability, and a simple configuration with excellent output characteristics. This is advantageous in that it can be done.

  In the following description, a non-polar type (internal parallel connection type) lithium ion battery and a bipolar type (internal series connection type) lithium ion battery according to the present invention will be described with reference to the drawings. is not.

  FIG. 1 schematically shows the overall structure of a laminated lithium ion secondary battery (hereinafter also simply referred to as a lithium ion battery) which is a typical embodiment of the lithium ion battery of the present invention. FIG.

  As shown in FIG. 1, in the lithium ion battery 10 of this embodiment, a substantially rectangular power generation element (battery element) 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminate sheet 29 that is an exterior. It has a structure. Specifically, the power generation element 21 is housed and sealed by using a polymer-metal composite laminate sheet as the battery exterior and joining all of its peripheral parts by thermal fusion.

  The power generation element 21 includes a positive electrode in which the positive electrode active material layer 13 is disposed on both surfaces of the positive electrode current collector 11, an electrolyte layer 17, and a negative electrode in which the negative electrode active material layer 15 is disposed on both surfaces of the negative electrode current collector 12. It has a stacked configuration. Specifically, the positive electrode, the electrolyte layer, and the negative electrode are laminated in this order so that one positive electrode active material layer 13 and the negative electrode active material layer 15 adjacent thereto face each other with the electrolyte layer 17 therebetween. .

  Thereby, the adjacent positive electrode, electrolyte layer, and negative electrode constitute one unit cell layer 19. Therefore, it can be said that the lithium ion battery 10 of the present embodiment has a configuration in which a plurality of single battery layers 19 are stacked and electrically connected in parallel. Further, on the outer periphery of the unit cell layer 19, a seal portion (insulating layer) for insulating between the adjacent positive electrode current collector 11 and negative electrode current collector 12 (not shown; reference numeral 31 in FIG. 4 described later) May be provided. Although the positive electrode active material layer 12 is disposed on only one side of the outermost layer positive electrode current collector located on both outermost layers of the power generation element 21, active material layers may be provided on both sides. In addition, the arrangement of the positive electrode and the negative electrode is reversed from that in FIG. 3 so that the outermost negative electrode current collector is positioned in both outermost layers of the power generation element 21, and the negative electrode is formed only on one side of the outermost negative electrode current collector. An active material layer may be arranged.

  The positive electrode current collector 11 and the negative electrode current collector 12 are attached to a positive electrode current collector plate 25 and a negative electrode current collector plate 27 that are electrically connected to the respective electrodes (positive electrode and negative electrode), and are sandwiched between end portions of the laminate sheet 29. Thus, it has a structure led out of the laminate sheet 29. The positive electrode current collector plate 25 and the negative electrode current collector plate 27 are ultrasonically welded to the positive electrode current collector 11 and the negative electrode current collector 12 of each electrode, respectively, via a positive electrode lead and a negative electrode lead (not shown) as necessary. Or resistance welding or the like.

  FIG. 2 schematically shows the overall structure of a bipolar stacked lithium ion secondary battery (hereinafter also simply referred to as a bipolar lithium ion battery), which is another typical embodiment of the lithium ion battery of the present invention. FIG. However, the technical scope of the present invention is not limited to such a form.

  In the bipolar battery 10 ′ of this embodiment shown in FIG. 2, a substantially rectangular power generation element (battery element; laminate) 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminate film 29 that is a battery exterior material. It has a stopped structure.

  As shown in FIG. 2, in the power generation element 21 of the bipolar battery 10 ′ of the present embodiment, a positive electrode active material layer 13 that is electrically coupled to one surface of the current collector 11 is formed. And a plurality of bipolar electrodes having a negative electrode active material layer 15 electrically coupled to the opposite surface. Each bipolar electrode is stacked via the electrolyte layer 17 to form the power generation element 21. The electrolyte layer 17 has a configuration in which an electrolyte is held at the center in the surface direction of a separator as a base material. At this time, each bipolar type is formed such that the positive electrode active material layer 13 of one bipolar electrode and the negative electrode active material layer 15 of another bipolar electrode adjacent to the one bipolar electrode face each other through the electrolyte layer 17. Electrodes and electrolyte layers 17 are alternately stacked. That is, the electrolyte layer 17 is disposed between the positive electrode active material layer 13 of one bipolar electrode and the negative electrode active material layer 15 of another bipolar electrode adjacent to the one bipolar electrode.

  The adjacent positive electrode active material layer 13, electrolyte layer 17, and negative electrode active material layer 15 constitute one single battery layer (= battery unit or single cell) 19. Therefore, it can be said that the bipolar battery 10 ′ has a configuration in which the single battery layers 19 are stacked. Further, for the purpose of preventing liquid junction due to leakage of the electrolytic solution from the electrolyte layer 17, a seal portion 31 is disposed on the outer peripheral portion of the unit cell layer 19. By providing the seal portion 31, it is possible to insulate between the adjacent current collectors 11 and prevent a short circuit due to contact between adjacent electrodes. A positive electrode active material layer 13 is formed only on one side of the positive electrode outermost layer current collector 11 a located in the outermost layer of the power generation element 21. The negative electrode active material layer 15 is formed only on one surface of the outermost current collector 11b on the negative electrode side located in the outermost layer of the power generation element 21. However, the positive electrode active material layer 13 may be formed on both surfaces of the outermost layer current collector 11a on the positive electrode side. Similarly, the negative electrode active material layer 13 may be formed on both surfaces of the outermost layer current collector 11b on the negative electrode side.

  Further, in the bipolar secondary battery 10 ′ shown in FIG. 2, a positive electrode current collector plate 25 is disposed so as to be adjacent to the positive electrode side outermost layer current collector 11a, and this is extended to form a laminate sheet 29 that is a battery exterior material. Derived. On the other hand, the negative electrode current collector plate 27 is disposed so as to be adjacent to the negative electrode side outermost layer current collector 11b, which is similarly extended and led out from the laminate sheet 29 which is an exterior of the battery.

  In the bipolar battery 10 ′ shown in FIG. 2, a seal portion 31 is usually provided around each single cell layer 19. The purpose of this seal portion 31 is to prevent the adjacent current collectors 14 in the battery from contacting each other and the occurrence of a short circuit due to a slight irregularity at the end of the unit cell layer 19 in the power generation element 21. Is provided. By installing such a seal portion 31, long-term reliability and safety can be ensured, and a high-quality bipolar battery 10 'can be provided.

  Note that the number of stacks of the unit cell layers 19 is adjusted according to a desired voltage. In the bipolar battery 10 ′, the number of times the single battery layer 19 is stacked may be reduced if a sufficient output can be secured even if the battery is made as thin as possible. Even in the bipolar battery 10 ′, in order to prevent external impact and environmental degradation during use, the power generation element 21 is sealed under reduced pressure in a laminate sheet 29 that is a battery exterior material, and the positive current collector plate 25 and the negative current collector. It is preferable that the plate 27 be taken out of the laminate sheet 29.

  The constituent elements and the manufacturing method of the lithium ion battery 10 and the bipolar battery 10 'are basically the same except that the electrical connection form (electrode structure) in both batteries is different. Therefore, it demonstrates below centering on each component of the above-mentioned lithium ion battery 10. FIG. However, it goes without saying that the constituent elements and the manufacturing method of the bipolar battery 10 ′ can be configured or manufactured by appropriately using the same constituent elements and manufacturing method. Moreover, an assembled battery and a vehicle can also be comprised using the lithium ion battery 10 and / or bipolar battery 10 'of this invention.

  In the present invention, the negative electrode active material layer uses an electrolyte (1) having a small compressive stress at 50% strain. The positive electrode active material layer uses an electrolyte (2) having a large compressive stress at 50% strain as compared with the negative electrode active material layer. Thus, by making a negative electrode active material layer into a soft structure, the gas generated on the negative electrode side can be efficiently released from the reaction site, and expansion and contraction can be effectively absorbed. Further, by making the positive electrode active material layer a hard structure, liquid leakage and short circuit can be effectively suppressed / prevented. Thereby, a large capacity and excellent output characteristics can be achieved. In the present invention, the negative electrode active material layer may have a laminated structure. In such a case, the electrolyte (1) having a low compressive stress at 50% strain according to the present invention is used at least at the interface between the electrolyte layer and the negative electrode active material layer. Thereby, the effect by this invention can fully be achieved. Moreover, the other layer which is not in contact with the electrolyte layer when the negative electrode active material layer has a laminated structure can be a negative electrode active material layer similar to the conventional one. Similarly, the positive electrode active material layer may have a laminated structure. In such a case, the electrolyte (2) having a large compressive stress at 50% strain according to the present invention is used at least at the interface between the electrolyte layer and the positive electrode active material layer. Thereby, the effect by this invention can fully be achieved. Moreover, the other layer which is not in contact with the electrolyte layer in the case where the positive electrode active material layer has a laminated structure can be a positive electrode active material layer similar to the conventional one.

  In the present specification, the “electrolyte” means a substance that ionizes into a cation and an anion when dissolved in a solvent. As will be described in detail below, when the electrolyte is an all-solid electrolyte, “electrolyte (1)” or “electrolyte (2)” means only an all-solid electrolyte. When the electrolyte is a gel electrolyte, the “electrolyte (1)” or “electrolyte (2)” means a gel electrolyte (polymer gel electrolyte) in which an electrolytic solution is held in a matrix polymer.

  In the present invention, the magnitude relationship of the compressive stress at the time of 50% strain between the electrolyte (1) and the electrolyte (2) is not particularly limited as long as the above effect can be achieved. Specifically, the ratio of the compressive stress at 50% strain of the electrolyte (2) of the positive electrode active material layer to the compressive stress at 50% strain of the electrolyte (1) of the negative electrode active material layer exceeds 1 and is 100. The following is preferable. Within such a range, long-term reliability and output characteristics can be improved. More preferably, the ratio of the compressive stress at 50% strain of the positive electrode active material layer to the compressive stress at 50% strain of the negative electrode active material layer is more than 1 and 50 or less, particularly preferably more than 1 and 10 or less. It is. In the present specification, “compressive stress at 50% strain” means a value measured by measuring the load-strain-stress of the electrolyte and measured in the following examples.

  Further, the compressive stress at the time of 50% strain of the electrolyte (1) used in the negative electrode active material layer is not particularly limited as long as the generated gas can be released and expansion and contraction can be appropriately absorbed. Preferably, the compressive stress at 50% strain of the electrolyte (1) is 0.01 to 2.5 MPa, more preferably 0.01 to 1.3 MPa. By using the electrolyte (1) having a compressive stress at the time of 50% strain for the negative electrode active material layer, the generated gas can be sufficiently released, and the expansion and contraction can be efficiently absorbed. Reliability can be achieved.

  The compressive stress at the time of 50% strain of the electrolyte (2) used for the positive electrode active material layer is not particularly limited as long as liquid leakage and short circuit can be suppressed / prevented as described above. Preferably, the compressive stress at 50% strain of the electrolyte (2) is 0.02 to 3.0 Mpa, more preferably 0.05 to 1.8 Mpa. By using such an electrolyte (2) having a compressive stress at 50% strain in the positive electrode active material layer, it is possible to sufficiently suppress and prevent liquid leakage and short circuit.

  Hereinafter, each component of the nonaqueous electrolyte secondary battery according to the present invention will be described.

<Positive electrode / negative electrode active material layer>
In the present invention, the form of the electrolyte used in the negative electrode active material layer and the positive electrode active material layer is not particularly limited, and the electrolyte may be in any form of liquid, gel, or solid. In consideration of safety when the battery is damaged and prevention of liquid junction, the electrolyte is preferably a solid polymer electrolyte such as a gel electrolyte or an all-solid electrolyte. That is, it is preferable that at least one of the electrolytes (1) and (2) is a solid polymer electrolyte. Liquid leakage can be prevented by using a solid polymer electrolyte as the electrolyte. As a result, a liquid junction can be prevented and a highly reliable lithium ion battery can be constituted. Here, the “solid polymer electrolyte” will be described later in detail, but includes a polymer gel electrolyte, a solid polymer electrolyte, and an inorganic solid electrolyte.

  Specific examples of the electrolyte include conventionally known materials: (a) gel electrolyte (polymer gel electrolyte), (b) all solid polymer electrolyte (polymer solid electrolyte, inorganic solid electrolyte), (c) A liquid electrolyte (electrolyte) is preferred. Hereinafter, these electrolytes will be described in detail.

(A) Gel electrolyte (polymer gel electrolyte)
The gel electrolyte (polymer gel electrolyte) refers to an electrolyte solution held in a matrix polymer (host polymer). The use of a gel electrolyte as the electrolyte is superior in that the fluidity of the electrolyte is lost, the electrolyte is prevented from flowing out to the current collector, and the ion conductivity between the layers can be easily blocked.

  As described in detail below, the gel electrolyte (polymer gel electrolyte) is prepared by including an electrolyte solution usually used in a lithium ion battery in an all solid polymer electrolyte such as PEO or PPO. Moreover, what hold | maintained electrolyte solution in polymer skeletons which do not have lithium ion conductivity, such as PVdF, PAN, and PMMA, is also contained in gel electrolyte (polymer gel electrolyte). The ratio of the polymer constituting the gel electrolyte and the electrolytic solution is not particularly limited. If 100% of the polymer is an all solid polymer electrolyte and 100% of the electrolyte is a liquid electrolyte, all of the intermediates are included in the concept of gel electrolyte (polymer gel electrolyte). An inorganic solid electrolyte having ion conductivity such as an inorganic solid such as ceramic corresponds to the all solid electrolyte. Therefore, the polymer gel electrolyte, the solid polymer electrolyte, and the inorganic solid electrolyte are all included in the solid electrolyte.

  Examples of the matrix polymer used as the gel electrolyte include a polymer having polyethylene oxide in the main chain or side chain (PEO), a polymer having polypropylene oxide in the main chain or side chain (PPO), polyethylene glycol (PEG), polyacrylonitrile ( PAN), polymethacrylic ester, polyvinylidene fluoride (PVdF), copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP), polyacrylonitrile (PAN), poly (methyl acrylate) (PMA), poly (methyl) Methacrylate) (PMMA). In addition, mixtures of the above-described polymers, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers, and the like can also be used. Among these, it is desirable to use PEO, PPO and their copolymers, PVdF, PVdF-HFP.

Moreover, as an electrolytic solution (plasticizer), it is possible to use an electrolytic solution usually used for a lithium ion battery. And such electrolyte, an electrolyte salt are those dissolved in a solvent, as the electrolyte _{salt, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiSbF 6, LiAlCl 4, Li 2 B 10 Cl 10, _{LiI, LiBr, LiCl, LiAlCl,} LiHF 2, inorganic acid anion salts such as _{LiSCN, LiCF 3 SO 3, Li} (CF 3 SO 2) 2 N, LiBOB ( lithium bis oxide borate), LiBETI (lithium bis (perfluoro And an organic acid anion salt such as Li (C ₂ F ₅ SO ₂ ) ₂ N). These electrolyte salts may be used alone or in the form of a mixture of two or more. As the solvent, ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethoxyethane. , Sulfolane, acetonitrile and the like. Of these, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate are preferred. These solvents may be used alone or in the form of a mixture of two or more. The concentration of the lithium salt in the electrolytic solution is not particularly limited, but usually about 0.5 to 2.5 mol / liter is preferable.

  The ratio of the electrolyte solution in the gel electrolyte in the present invention is not particularly limited, but is appropriately adjusted according to the desired compressive stress at the time of 50% strain of the electrolytes (1) and (2). sell. In addition, the compressive stress at the time of 50% distortion of the electrolytes (1) and (2) varies depending on the types of the matrix polymer and the electrolytic solution. Usually, the content of the matrix polymer is 0.1 to 50% by mass, more preferably 1 to 30% by mass, based on the total of the matrix polymer and the electrolytic solution. In particular, when PVdF is used as the matrix polymer, the content of PVdF is 1 to 20% by mass, and more preferably 1 to 15% by mass, based on the total of the matrix polymer and the electrolytic solution.

  Further, the compressive stress at 50% strain can be controlled by controlling the type and amount of electrolyte used in the active material layer. Hereinafter, although the preferable control method is described, this invention is not limited to the following form. In general, the compressive stress at 50% strain is proportional to the amount of electrolyte. For this reason, the compression stress at the time of 50% strain can be appropriately controlled by defining the amounts of the electrolyte and the electrolyte contained in the active material layer. For example, when the electrolyte (1) is a gel electrolyte layer, about 50 to 99.9% by mass with respect to the mass of the gel polymer electrolyte (= total mass of the matrix polymer and the electrolyte solution) in the matrix polymer. It is preferable to hold the electrolytic solution. More preferably, it is preferable to hold about 70-97 mass% electrolyte solution with respect to the mass of a gel polymer electrolyte (= total mass of a matrix polymer and electrolyte solution) in a matrix polymer. Moreover, when electrolyte (2) is a gel electrolyte layer, about 50-95 mass% electrolyte solution with respect to the mass (= total mass of a matrix polymer and electrolyte solution) in gel polymer electrolyte in a matrix polymer. Is preferably retained. More preferably, about 70-95 mass% electrolyte solution is hold | maintained with respect to the mass of a gel polymer electrolyte (= total mass of a matrix polymer and electrolyte solution) in a matrix polymer. Thus, the compression stress at the time of 50% strain can be controlled to a desired level by appropriately adjusting the holding amount of the electrolytic solution in the matrix polymer.

  Here, when the electrolyte (1) or (2) is a gel electrolyte, the method for forming the active material layer containing the gel electrolyte is not particularly limited, and a conventionally known method is applied in the same manner or appropriately modified. it can. For example, (a) a method of cooling a polymer to room temperature by using an electrolyte containing a polymer that can be gelled by cooling in a heated state, and (a) a monomer using an electrolyte containing a monomer. A polymerization method or the like can be employed.

  Of the above methods, in the method (a), it is usually sufficient to apply an electrolytic solution to the surface of the active material layer and leave it for an appropriate period of time, but the rate at which the electrolytic solution impregnates the voids in the active material layer. In order to increase the pressure, operations such as press-fitting and vacuum impregnation may be performed. The gel electrolyte is preferably formed by completely filling the voids in the active material layer, but even if a certain amount of voids remain, there is no significant problem with battery characteristics. In the case where voids are generated to such a degree that the battery characteristics are deteriorated, it is preferable to employ a method for increasing the impregnation rate as described above. The gelable polymer used in (a) above is appropriately selected from the matrix polymers. Specific examples include PMMA, PEMA, PMA, PEA, polyacrylic acid, polymethacrylic acid, PVdF, PVdF-HFP, and PAN.

  In the method (a), since the viscosity of the electrolytic solution is low, it is easy to impregnate the electrolytic solution in the voids of the active material layer. Since the thickness of the active material layer is usually 1 mm or less, the impregnation with the electrolytic solution is completed quickly. Further, in any method, by applying a calendar treatment to the coating film, the coating film can be consolidated and the active material filling amount can be increased. In addition, the monomer used by said (a) is suitably selected according to the kind of desired gel electrolyte. Polymers that are easy to control polymerization and that are produced by addition polymerization that does not generate by-products during polymerization are preferred. In particular, a polymer produced by addition polymerization of a reactive unsaturated group-containing monomer is excellent in productivity. Specifically, the reactive unsaturated group-containing monomer includes acrylic acid, methyl acrylate, ethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, ethoxyethyl acrylate, methoxyethyl acrylate, ethoxyethoxyethyl acrylate, Examples include polyethylene glycol monoacrylate, ethoxyethyl methacrylate, methoxyethyl methacrylate, ethoxyethoxyethyl methacrylate, polyethylene glycol monomethacrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminoethyl acrylate, and acrylonitrile. In addition, as a method for polymerizing the monomer, a known method using heat, ultraviolet rays, electron beams or the like can be applied. From the viewpoint of productivity, a method using ultraviolet rays is preferred. In this case, in order to effectively advance the reaction, a polymerization initiator that reacts with ultraviolet rays can be blended in the electrolytic solution. Examples of the ultraviolet polymerization initiator include benzoin, benzyl, acetophenone, benzophenone, Michler's ketone, biacetyl, benzoyl peroxide and the like.

  More specifically, an electrolyte is prepared by dissolving an electrolyte salt in a solvent. A matrix polymer and a polymerization initiator are added to this electrolytic solution to prepare an electrolyte precursor solution. Next, after immersing the active material layer in the electrolyte precursor solution, the excess electrolyte precursor solution is removed to obtain an impregnated active material layer. Further, the electrolyte of the impregnated active material layer is polymerized. Here, the conditions for immersing the active material layer in the electrolyte precursor solution are not particularly limited as long as the electrolyte precursor solution is sufficiently infiltrated into the active material layer. Specifically, the active material layer may be immersed in the electrolyte precursor solution at a temperature of 15 to 60 ° C., more preferably 20 to 50 ° C. for 1 to 120 minutes, more preferably 5 to 60 minutes. preferable. Moreover, after immersing on predetermined conditions, an excess electrolyte precursor solution is removed, However, It does not restrict | limit especially as a method which can be used in this case, A well-known method can be used. For example, a method in which an active material layer soaked with an electrolyte precursor solution is sandwiched between footwear films and then lightly squeezed with a roll or the like; a method in which a separator substrate soaked with an electrolyte precursor solution is lightly squeezed can be preferably used.

(B) All solid electrolyte (polymer solid electrolyte, inorganic solid electrolyte)
The use of an all solid electrolyte as the electrolyte is superior in that the fluidity of the electrolyte is lost, the electrolyte does not flow out to the current collector layer, and the ion conductivity between the layers can be blocked.

Examples of the all solid electrolyte include known solid polymer electrolytes such as PEO, PPO, and copolymers thereof, and inorganic solid electrolytes having ion conductivity such as ceramic. The solid polymer electrolyte contains a lithium salt to ensure ionic conductivity. The lithium _{salt, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiSbF 6, LiAlCl 4, Li 2 B 10 Cl 10, LiI, LiBr, LiCl, LiAlCl, LiHF 2, inorganic acid anions such as LiSCN Ionic salt, LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiBOB (lithium bisoxide borate), LiBETI (lithium bis (perfluoroethylenesulfonylimide); Li (C ₂ F ₅ SO ₂ ) ₂ N Organic acid anion salts, etc.). Preferably, LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ can be used. In addition, the said lithium salt may be used independently or may be used with the form of 2 or more types of mixtures.

(C) Liquid electrolyte (electrolyte)
Examples of the electrolytic solution include those obtained by dissolving an electrolyte salt in a solvent. Here, the electrolyte salt is not particularly limited. _{Specifically, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiSbF 6, LiAlCl 4, Li 2 B 10 Cl 10, LiI, LiBr, LiCl, LiAlCl, LiHF 2, inorganic acid anions such as LiSCN Ionic salt, LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiBOB (lithium bisoxide borate), LiBETI (lithium bis (perfluoroethylenesulfonylimide); Li (C ₂ F ₅ SO ₂ ) ₂ N Organic acid anion salts, etc.). These electrolyte salts may be used alone or in the form of a mixture of two or more. Also, the solvent is not particularly limited. Specifically, examples of the solvent include EC, PC, GBL, DMC, and DEC. These solvents may be used alone or in the form of a mixture of two or more.

  At least one of the positive electrode active material layer and the negative electrode active material layer according to the present invention preferably has a network structure or a pore structure. When the electrolyte (1) or (2) is a liquid electrolyte, generally, when the liquid is injected from the direction along the surface of the laminate, the liquid hardly penetrates most in the vicinity of the center of each layer. For this reason, even if the liquid electrolyte is injected in each step, there may be a portion where the liquid electrolyte does not sufficiently penetrate. However, with such a structure, penetration of the electrolyte solution in the surface direction can be promoted, and lithium ions can be easily taken up. In addition, since the penetration depth of the liquid is short in the depth (thickness) direction of the surface, the surface can be sufficiently penetrated and ion conductivity can be sufficiently secured. Here, either one or both of the positive electrode active material layer and the negative electrode active material layer preferably have the above-described structure, and more preferably, at least the negative electrode active material layer has the above structure. When the active material layer has a network structure or a pore structure, the porosity of the active material layer is not particularly limited as long as it can promote the penetration of the electrolytic solution and sufficiently ensure the ionic conductivity. The porosity of the positive electrode active material layer and the negative electrode active material layer is preferably 10 to 40%, respectively. Here, the porosity of the positive electrode active material layer and the negative electrode active material layer may be the same or different. If the porosity of each layer is 10% or more, sufficient voids can be secured and a sufficient amount of liquid material can be spread. On the contrary, if it is 40% or less, a sufficient capacity as a secondary battery can be secured. Further, the relationship between the porosity of the positive electrode active material layer and the porosity of the negative electrode active material layer is not particularly limited. Preferably, the ratio of the voids of the positive electrode active material layer to the porosity of the negative electrode active material layer is 80 to 120%. In addition, the said porosity means the porosity of the said 1 layer, when a positive electrode layer and a negative electrode layer are one layer, and the porosity of each layer in the case of being a laminated body of two or more layers, respectively. .

  As described above, the active material layer is a layer including an active material that is formed on the current collector and plays a central role in the charge / discharge reaction. As described above, the negative electrode active material layer includes the electrolyte (1) having a low compressive stress at the time of 50% strain. Further, the positive electrode active material layer includes an electrolyte (2) having a high compressive stress at the time of 50% strain. Each active material layer contains an active material. That is, the positive electrode active material layer includes a positive electrode active material. The negative electrode active material layer includes a negative electrode active material.

Here, the positive electrode active material has a composition that occludes ions during discharge and releases ions during charge. A preferable example is a lithium-transition metal composite oxide that is a composite oxide of a transition metal and lithium. Specifically, Li · Co-based composite oxide such as LiCoO _2, Li · Ni-based composite oxide such as LiNiO _2, Li · Mn-based composite oxide such as spinel LiMn ₂ O _4, Li · such LiFeO ₂ Fe-based composite oxides and those obtained by replacing some of these transition metals with other elements can be used. These lithium-transition metal composite oxides are excellent in reactivity and cycle characteristics, and are low-cost materials. Therefore, it is possible to form a battery having excellent output characteristics by using these materials for electrodes. In addition, examples of the positive electrode active material include transition metal oxides such as LiFePO ₄ and lithium phosphate compounds and sulfuric acid compounds; transition metal oxides such as V ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ , and MoO ₃ , and sulfides. Materials; PbO ₂ , AgO, NiOOH, etc. can also be used. The positive electrode active material may be used alone or in the form of a mixture of two or more. The average particle diameter of the positive electrode active material is not particularly limited, but is preferably 1 to 100 μm, more preferably 1 to 20 μm, from the viewpoint of increasing the capacity, reactivity, and cycle durability of the positive electrode active material. Within such a range, the secondary battery can suppress an increase in the internal resistance of the battery during charging and discharging under high output conditions, and can extract a sufficient current. When the positive electrode active material is secondary particles, it can be said that the average particle diameter of the primary particles constituting the secondary particles is preferably in the range of 10 nm to 1 μm. It is not limited to. However, it goes without saying that, depending on the manufacturing method, the positive electrode active material may not be a secondary particle formed by aggregation, agglomeration, or the like. As the particle diameter of the positive electrode active material and the particle diameter of the primary particles, a median diameter obtained using a laser diffraction method can be used. The shape of the positive electrode active material varies depending on the type and manufacturing method, and examples thereof include a spherical shape (powdered shape), a plate shape, a needle shape, a column shape, and a square shape, but are not limited thereto. Any shape can be used without any problems. Preferably, an optimal shape that can improve battery characteristics such as charge / discharge characteristics is appropriately selected.

Further, the negative electrode active material has a composition that releases ions during discharging and can store ions during charging. The negative electrode active material is not particularly limited as long as it can reversibly occlude and release lithium. Examples of the negative electrode active material include metals such as Si and Sn, TiO, Ti ₂ O ₃ , TiO ₂ , or Metal oxides such as SiO ₂ , SiO, SnO ₂ , complex oxides of lithium and transition metals such as Li _4/3 Ti _5/3 O ₄ or Li ₇ MnN, Li—Pb alloys, Li—Al alloys , Li, or carbon materials such as natural graphite, artificial graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon, or hard carbon. Moreover, it is preferable that a negative electrode active material contains the element alloyed with lithium. By using an element that forms an alloy with lithium, it is possible to obtain a battery having a high capacity and an excellent output characteristic having a higher energy density than that of a conventional carbon-based material. The negative electrode active material may be used alone or in the form of a mixture of two or more.

  The element alloying with lithium is not limited to the following, but specifically, Si, Ge, Sn, Pb, Al, In, Zn, H, Ca, Sr, Ba, Ru, Rh, Ir, Pd, Pt, Ag, Au, Cd, Hg, Ga, Tl, C, N, Sb, Bi, O, S, Se, Te, Cl, and the like. Among these, from the viewpoint of configuring a battery having excellent capacity and energy density, at least one selected from the group consisting of carbon materials and / or Si, Ge, Sn, Pb, Al, In, and Zn. It is preferable to include an element, and it is particularly preferable to include an element of a carbon material, Si, or Sn. These may be used alone or in combination of two or more.

  The average particle size of the negative electrode active material is not particularly limited, but is preferably 1 to 100 μm, more preferably 1 to 20 μm from the viewpoint of increasing the capacity, reactivity, and cycle durability of the negative electrode active material. Within such a range, the secondary battery can suppress an increase in the internal resistance of the battery during charging and discharging under high output conditions, and can extract a sufficient current. In addition, when the negative electrode active material is secondary particles, it can be said that the average particle diameter of primary particles constituting the secondary particles is desirably in the range of 10 nm to 1 μm. It is not limited to. However, it goes without saying that, depending on the manufacturing method, the negative electrode active material may not be a secondary particle formed by aggregation, lump or the like. As the particle diameter of the negative electrode active material and the particle diameter of the primary particles, a median diameter obtained by using a laser diffraction method can be used. The shape of the negative electrode active material varies depending on the type and manufacturing method, and examples thereof include a spherical shape (powdered shape), a plate shape, a needle shape, a column shape, and a square shape, but are not limited thereto. Any shape can be used without any problems. Preferably, an optimal shape that can improve battery characteristics such as charge / discharge characteristics is appropriately selected.

  The active material layer may contain other materials if necessary. For example, a conductive aid, a binder, and the like can be included. When an ion conductive polymer is included, a polymerization initiator for polymerizing the polymer may be included.

  A conductive support agent means the additive mix | blended in order to improve the electroconductivity of an active material layer. Examples of the conductive aid include carbon powders such as acetylene black, carbon black, ketjen black, and graphite, various carbon fibers such as vapor grown carbon fiber (VGCF; registered trademark), expanded graphite, and the like. However, it goes without saying that the conductive assistant is not limited to these.

  Examples of the binder include polyvinylidene fluoride (PVdF), polyvinylidene fluoride (PVdF), polyimide, PTFE, SBR, and a synthetic rubber binder. However, it goes without saying that the binder is not limited to these. When the binder and the matrix polymer used as the gel electrolyte are the same, it is not necessary to use a binder.

  The compounding ratio of the components contained in the active material layer is not particularly limited. The blending ratio can be adjusted by appropriately referring to known knowledge about lithium ion secondary batteries.

  There is no restriction | limiting in particular also about the thickness of an active material layer, The conventionally well-known knowledge about a nonaqueous electrolyte secondary battery can be referred suitably. As an example, the thickness of the active material layer is preferably about 10 to 100 μm, and more preferably 20 to 50 μm. If the active material layer is about 10 μm or more, the battery capacity can be sufficiently secured. On the other hand, if the active material layer is about 100 μm or less, it is possible to suppress the occurrence of the problem of an increase in internal resistance due to the difficulty in diffusing lithium ions in the electrode deep part (current collector side).

<Current collector>
In the present invention, the material of the current collector is not particularly limited, but specific examples include, for example, iron, chromium, nickel, manganese, titanium, molybdenum, vanadium, niobium, aluminum, copper, silver, gold, and platinum. And at least one current collector material selected from the group consisting of carbon and more preferably at least one current collector selected from the group consisting of aluminum, titanium, copper, nickel, silver, or stainless steel (SUS) Preferred examples include electrical materials, which may be used in a single layer structure (for example, in the form of a foil), may be used in a multilayer structure composed of different kinds of layers, or may be covered with these. A clad material (for example, a clad material of nickel and aluminum, a clad material of copper and aluminum) may be used. Alternatively, a plating material of a combination of these current collector materials can be preferably used. Further, a current collector in which the surface of a metal (excluding aluminum) as the current collector material is coated with aluminum as another current collector material may be used. Moreover, you may use the electrical power collector which bonded together the metal foil which is two or more said electrical power collector materials depending on the case. The above materials are excellent in corrosion resistance, conductivity, workability, and the like. The general thickness of the current collector is 5 to 50 μm. However, a current collector having a thickness outside this range may be used.

  The size of the current collector is determined according to the intended use of the battery. If a large electrode used for a large battery is manufactured, a current collector having a large area is used. If a small electrode is produced, a current collector with a small area is used.

  The method for forming the positive electrode layer (or the negative electrode layer) on the surface of the current collector is not particularly limited, and known methods can be used in the same manner. For example, as described above, a positive electrode active material (or a negative electrode active material), and if necessary, an electrolyte salt for increasing ionic conductivity, a conductive assistant for increasing electronic conductivity, and a binder, A positive electrode active material liquid (or a negative electrode active material liquid) is prepared by dispersing and dissolving in an appropriate solvent. This is applied onto a current collector, dried to remove the solvent, and then pressed to form a positive electrode layer (or negative electrode layer) on the current collector. In this case, the solvent is not particularly limited, and N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylformamide, cyclohexane, hexane and the like can be used. When adopting polyvinylidene fluoride (PVdF) as a binder, NMP may be used as a solvent.

  In the above method, the positive electrode active material liquid (or the negative electrode active material liquid) is applied onto the current collector, dried, and then pressed. At this time, the porosity of the positive electrode layer (or the negative electrode layer) can be controlled by adjusting the pressing conditions.

  Specific means and press conditions for the press treatment are not particularly limited, and can be appropriately adjusted so that the porosity of the positive electrode layer (or the negative electrode layer) after the press treatment becomes a desired value. Specific examples of the press process include a hot press machine and a calendar roll press machine. Also, the pressing conditions (temperature, pressure, etc.) are not particularly limited, and conventionally known knowledge can be referred to as appropriate.

  The thicknesses of the positive electrode layer and the negative electrode layer are not particularly limited, but are preferably 10 to 200 μm, particularly 20 to 100 μm. At this time, the thicknesses of the positive electrode layer and the negative electrode layer may be the same or different.

  Each of the positive electrode layer and the negative electrode layer may be a single layer or a laminate of two or more layers. When the positive electrode layer and the negative electrode layer are laminates, the number of layers is not particularly limited, and is 1 to 3 in consideration of ease of liquid electrolyte injection and ion conductivity, which will be described in detail below. It is preferable.

  When the positive electrode layer and the negative electrode layer are laminates, the positive electrode layer and the negative electrode layer are preferably composed of a plurality of layers having different porosity in the thickness direction of the negative electrode layer. Here, either one or both of the positive electrode layer and the negative electrode layer may have a structure composed of a plurality of layers having different porosity in the thickness direction of the negative electrode layer as described above. It is preferable that at least the negative electrode layer has the above structure. Such a structure is achieved by repeatedly forming the positive electrode layer and the negative electrode layer using the same method as described above.

<Electrolyte layer>
In the nonaqueous electrolyte secondary battery of the present invention, an electrolyte layer is provided between the positive electrode and the negative electrode. Here, the electrolyte layer preferably has a separator. In this case, the separator is impregnated with an electrolyte having a compressive stress at 50% strain lower than that of the electrolyte (2) used in the positive electrode active material layer. preferable. Here, the separator (1) used in the negative electrode active material layer is more preferably impregnated in the separator. By providing a soft structure having a low compressive stress at 50% strain as the electrolyte layer in this way, even if the gas moves to the electrolyte layer side, this gas can be easily released, and expansion and contraction at the negative electrode Can be absorbed more effectively. Furthermore, output characteristics can be improved by using the electrolyte (1) used in the negative electrode active material layer for the electrolyte layer.

  Further, the structure of the separator is not particularly limited, and may be only one layer (the separator itself constitutes the electrolyte layer) or may be a laminate of two or more layers. In the latter case, the separator impregnated with the electrolyte having a small compressive stress at the time of 50% strain is preferably disposed so as to be in contact with at least the negative electrode active material layer, and both the negative electrode active material layer and the positive electrode active material layer More preferably, they are arranged so as to contact each other. By disposing a separator impregnated with an electrolyte having a small compressive stress at 50% strain on the negative electrode active material layer side, expansion and contraction on the negative electrode side can be absorbed in the electrolyte layer in addition to the negative electrode active material layer. it can. In such a case, even when the gas generated during the coating formation on the negative electrode surface moves to the electrolyte layer side, the gas easily moves out of the unit cell layer because the electrolyte layer is soft. sell.

  Here, it does not restrict | limit especially as a separator, A well-known separator base material can be used. Examples thereof include polyolefin resins such as a microporous polyethylene film, a microporous polypropylene film, and a microporous ethylene-propylene copolymer film, and porous films or nonwoven fabrics such as aramid, polyimide, and cellulose, and laminates thereof. These have the outstanding effect that the reactivity with electrolyte (electrolyte solution) can be restrained low. In addition, a composite resin film in which a polyolefin-based resin nonwoven fabric or a polyolefin-based resin porous film is used as a reinforcing material layer, and the reinforcing material layer is filled with a vinylidene fluoride resin compound may be used.

  The thickness of the separator base material may be appropriately determined according to the intended use, but may be about 1 to 100 μm in the use of a secondary battery for driving a motor such as an automobile. Further, the porosity and size of the separator base material may be appropriately determined in consideration of the characteristics of the obtained secondary battery. For example, the porosity of the separator substrate is preferably 30 to 80%, more preferably 40 to 70%. The curvature of the separator base material is preferably 1.2 to 2.8. If it is a separator base material which has such porosity, sufficient quantity of electrolyte solution and the electrolyte of a separator layer can be introduce | transduced, and the intensity | strength of a separator layer can also be fully maintained.

  The electrolyte impregnated in the separator is not particularly limited, and a known electrolyte can be used. However, an electrolyte having a compression stress at 50% strain smaller than the electrolyte (2) is preferable. As the specific electrolyte, the same electrolyte as that described in the negative electrode / positive electrode active material layer can be used, and the description thereof is omitted here.

  Further, the method and conditions for impregnating the separator with an electrolyte having a smaller compressive stress at the time of 50% strain than the electrolyte (2) are not particularly limited. Here, the ratio of the compressive stress at the time of 50% strain of the electrolyte (2) to the electrolyte of the separator is not particularly limited, but is preferably more than 1 and 100 or less. Specifically, methods and conditions similar to the methods and conditions for forming the active material layer using the electrolyte (1) or (2) described above can be used. More specifically, an electrolyte is prepared by dissolving an electrolyte salt in a solvent. A matrix polymer and a polymerization initiator are added to this electrolytic solution to prepare an electrolyte precursor solution. Next, after the separator base material is immersed in the electrolyte precursor solution, an excess electrolyte precursor solution is removed to obtain an impregnated separator. Further, the electrolyte of the impregnated separator is polymerized. Here, the conditions for immersing the separator base material in the electrolyte precursor solution are not particularly limited as long as the electrolyte precursor solution sufficiently permeates the separator base material. Specifically, the separator base material may be immersed in the electrolyte precursor solution at a temperature of 15 to 60 ° C., more preferably 20 to 50 ° C., for 1 to 120 minutes, more preferably 5 to 60 minutes. preferable. Moreover, after immersing on predetermined conditions, an excess electrolyte precursor solution is removed, However, It does not restrict | limit especially as a method which can be used in this case, A well-known method can be used. For example, a method in which a separator base material infiltrated with an electrolyte precursor solution is sandwiched between footwear films and then lightly squeezed with a roll or the like; a method in which a separator base material infiltrated with an electrolyte precursor solution is lightly squeezed can be preferably used. When polymerizing the electrolyte of the impregnated separator, the polymerization reaction is performed in a state where the impregnated separator is sandwiched between the positive electrode active material layer and the negative electrode active material layer, whereby the positive electrode active material layer, the separator (electrolyte layer) ) And the negative electrode active material layer may be adhered to each other.

<Appearance structure of lithium ion secondary battery>
FIG. 3 is a perspective view showing an appearance of a stacked flat non-bipolar or bipolar lithium ion secondary battery which is a typical embodiment of the lithium ion battery according to the present invention.

  As shown in FIG. 3, the stacked flat lithium ion secondary battery 50 has a rectangular flat shape, and a positive electrode tab 58 and a negative electrode tab 59 for taking out electric power from both sides thereof. Has been pulled out. The power generation element (battery element) 57 is wrapped by the battery outer packaging material 52 of the lithium ion secondary battery 50, and the periphery thereof is heat-sealed. The power generation element (battery element) 57 includes a positive electrode tab 58 and a negative electrode tab 59. It is sealed in a state where it is pulled out to the outside. Here, the power generation element (battery element) 57 corresponds to the power generation element (battery element) 21 of the non-bipolar or bipolar lithium ion secondary battery 10, 10 ′ shown in FIG. 1 or FIG. A plurality of single battery layers (single cells) 19 composed of a positive electrode (positive electrode active material layer) 13, an electrolyte layer 17 and a negative electrode (negative electrode active material layer) 15 are laminated.

  The lithium ion battery of the present invention is not limited to the stacked flat shape shown in FIGS. 1 and 2, and the wound lithium ion battery has a cylindrical shape. It is not particularly limited, for example, such a cylindrical shape may be transformed into a rectangular flat shape. In the said cylindrical shape thing, a laminate film may be used for the exterior material, and the conventional cylindrical can (metal can) may be used, for example, It does not restrict | limit. Preferably, the power generation element (battery element) is covered with an aluminum laminate film. With this configuration, weight reduction can be achieved.

  3 is not particularly limited, and the positive electrode tab 58 and the negative electrode tab 59 may be pulled out from the same side, or the positive electrode tab 58 and the negative electrode tab 59 may be pulled out. However, the present invention is not limited to the one shown in FIG. 3, for example. Further, in a wound type lithium ion battery, instead of a tab, for example, a terminal may be formed using a cylindrical can (metal can).

  The lithium ion battery of the present invention is used as a power source for driving a vehicle or an auxiliary power source that requires a high volume energy density and a high volume output density as a large capacity power source for an electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, a hybrid fuel cell vehicle, It can be suitably used.

<Battery assembly>
The assembled battery of the present invention is formed by connecting a plurality of lithium ion secondary batteries of the present invention. Specifically, at least two or more are used, and are configured by serialization, parallelization, or both. Capacitance and voltage can be freely adjusted by paralleling in series. In the assembled battery of the present invention, the non-bipolar lithium ion secondary battery and the bipolar lithium ion secondary battery of the present invention are used, and these are combined in series, in parallel, or in series and in parallel. Thus, an assembled battery can also be configured.

  4 is an external view of a typical embodiment of the assembled battery according to the present invention, FIG. 4A is a plan view of the assembled battery, FIG. 4B is a front view of the assembled battery, and FIG. It is a side view of an assembled battery.

  As shown in FIG. 4, an assembled battery 300 according to the present invention forms a small assembled battery 250 in which a plurality of lithium ion secondary batteries of the present invention are connected in series or in parallel, and is detachable. A plurality of detachable small assembled batteries 250 are connected in series or in parallel, and have a large capacity and a large output suitable for vehicle power supplies and auxiliary power supplies that require high volume energy density and high volume output density. The assembled battery 300 can also be formed. 4A is a plan view of the assembled battery, FIG. 4A is a front view, and FIG. 4C is a side view. The small assembled battery 250 that can be attached / detached has an electrical connection means such as a bus bar. The assembled battery 250 is stacked in a plurality of stages using the connection jig 310. How many non-bipolar or bipolar lithium ion secondary batteries are connected to produce the assembled battery 250, and how many assembled batteries 250 are stacked to produce the assembled battery 300 are mounted. What is necessary is just to determine according to the battery capacity and output of the vehicle (electric vehicle) to be.

<Vehicle>
The vehicle of the present invention is characterized in that the lithium ion battery of the present invention or an assembled battery formed by combining a plurality of these is mounted. In the present invention, since a long-life battery excellent in long-term reliability and output characteristics can be configured, when such a battery is mounted, a plug-in hybrid electric vehicle having a long EV travel distance or an electric vehicle having a long charge travel distance can be configured. . In other words, the lithium ion battery of the present invention or an assembled battery formed by combining a plurality of these can be used as a power source for driving a vehicle. The lithium ion battery of the present invention or an assembled battery formed by combining a plurality of these is a vehicle, for example, a car, a hybrid car, a fuel cell car, an electric car (all are four-wheeled vehicles (passenger cars, commercial vehicles such as trucks and buses, This is because it can be used for motorcycles (including motorcycles) and tricycles (in addition to mini vehicles, etc.)) to provide a long-life and highly reliable vehicle. However, the application is not limited to automobiles. For example, it can be applied to various power sources for moving vehicles such as other vehicles, for example, trains, and power sources for mounting such as uninterruptible power supplies. It is also possible to use as.

  FIG. 5 is a conceptual diagram of a vehicle equipped with the assembled battery of the present invention.

  As shown in FIG. 5, in order to mount the assembled battery 300 on a vehicle such as the electric vehicle 400, the battery pack 300 is mounted under the seat at the center of the vehicle body of the electric vehicle 400. This is because if it is installed under the seat, the interior space and the trunk room can be widened. The place where the assembled battery 300 is mounted is not limited to the position under the seat, but may be a lower part of the rear trunk room or an engine room in front of the vehicle. The electric vehicle 400 using the assembled battery 300 as described above has high durability and can provide sufficient output even when used for a long period of time. Furthermore, it is possible to provide electric vehicles and hybrid vehicles that are excellent in fuel efficiency and running performance. A vehicle equipped with the assembled battery of the present invention can be widely applied to a hybrid vehicle, a fuel cell vehicle and the like in addition to an electric vehicle as shown in FIG.

  The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples.

  The compressive stress at 50% strain of the electrolyte was measured according to the following method.

<Method of measuring compressive stress at 50% strain of electrolyte>
The load-strain-stress of the gel electrolyte was measured at room temperature as follows.

  An electrolyte membrane was prepared as follows. Specifically, first, a gel electrolyte containing a solvent is poured into a petri dish. Next, this petri dish is heated in a dry environment to volatilize excess electrolytic components to obtain a gel electrolyte. Here, confirmation of the obtained gel electrolyte was confirmed from the electrical conductivity obtained by measuring impedance by a four-terminal method while measuring the thickness with a micrometer.

  A gel electrolyte is obtained in the same manner as in the above method except that a separator (polyolefin, thickness: 100 μm) is used. For the gel electrolyte thus obtained, the electrical conductivity was measured by the above method to confirm the accuracy of the gel electrolyte.

  About the obtained electrolyte membrane, the compression characteristic was evaluated on condition of the following. Load area: 12 mm, compressive displacement: compressive load (N) when displaced under the conditions of 0.01 mm / sec, compressive strain (%, value normalized by anvil height based on compressive displacement), compressive stress ( MPa) was detected every 0.5 sec. The measurement was terminated when the compressive strain reached 50%, and the compressive stress (MPa) at this time was defined as “compressive stress at 50% strain”.

Example 1
(1) Production of Negative Electrode Hard carbon (average particle diameter 20 μm) (85 wt%) was mixed as a negative electrode active material, acetylene black (5 wt%) was mixed as a conductive assistant, and PVdF (10 wt%) was mixed as a binder. To the mixture, NMP was added as a solvent and sufficiently stirred to prepare a slurry. The slurry thus obtained was applied, dried and pressed on a 15 μm copper (Cu) foil as a negative electrode current collector so that the final negative electrode active material layer had a thickness of 25 μm. It was.

  A heated roll press is applied to the negative electrode thus produced, and the hot press is performed to such an extent that the negative electrode does not break through the film. Thereafter, the produced negative electrode was cut into 90 × 90 mm.

(2) Impregnation of electrolyte (1) The electrolyte is a mixture of EC: PC (1: 1 vol%) (90 wt%) containing 1 M / L LiPF ₆ as a supporting salt and PVdF-HFP (10 wt%) as a host polymer. Then, dimethyl carbonate (DMC) was added as a solvent to the mixture and stirred sufficiently to obtain a gel electrolyte (1). The gel electrolyte (1) was applied to the negative electrode prepared in the above (1), and DMC was dried to impregnate the negative electrode with the gel electrolyte (1). In addition, the compressive stress at the time of 50% distortion of the gel electrolyte (1) used here was 0.171 MPa.

(3) Production of positive electrode LiMn ₂ O ₄ (average particle diameter 20 μm) (85 wt%) as a positive electrode active material, acetylene black (5 wt%) as a conductive assistant, and PVdF (10 wt%) as a binder were mixed. To the mixture, N-methyl-2-pyrrolidone (NMP) was added as a solvent and sufficiently stirred to prepare a slurry. The slurry thus obtained was applied on an aluminum (Al) foil which is a current collector having a thickness of 20 μm as a positive electrode current collector so that the final positive electrode active material layer had a thickness of 20 μm. Then, after pressing, it was dried to obtain a positive electrode.

  A heated roll press is applied to the positive electrode thus produced, and the hot press is performed to such an extent that the positive electrode does not break through the film. Thereafter, the produced positive electrode was cut into 90 × 90 mm.

(4) Impregnation of electrolyte (2) EC: PC (1: 1 volume%) (87 wt%) containing 1 M / L LiPF ₆ as a supporting salt as an electrolytic solution and PVdF-HFP (13 wt%) as a host polymer are mixed Then, DMC was added as a solvent to the mixture and stirred sufficiently to obtain a gel electrolyte (2). This gel electrolyte (2) was applied to the positive electrode prepared in (3) above, and DMC was dried, so that the gel electrolyte (2) was impregnated in the positive electrode. In addition, the compressive stress at the time of 50% distortion of the gel electrolyte (2) used here was 0.484 MPa.

(5) Preparation of gel polymer electrolyte layer By applying the gel electrolyte (1) prepared in (2) above to a 95 × 95 mm separator (polyolefin microporous membrane, thickness: 20 μm) and drying the DMC, A gel polymer electrolyte layer was prepared by impregnating the negative electrode with a gel electrolyte.

(6) Production of bipolar secondary battery The negative electrode produced in (2) above, the gel polymer electrolyte layer produced in (5) above, and the positive electrode produced in (4) above were laminated, A PE film was placed as a sealing material. After laminating three layers of such bipolar electrodes, the seal part was pressed from above and below (press conditions: 0.2 MPa, 160 ° C., 5 s) and fused to seal each layer.

  A high voltage terminal having a portion in which a part of a 100 μm Al plate of 130 mm × 80 mm capable of covering the entire projection surface of the bipolar battery element extended to the outside of the battery projection surface was produced. A bipolar battery element is sandwiched between these terminals, vacuum-sealed with aluminum laminate so as to cover them, and the entire bipolar battery element is pressurized by pressing both sides at atmospheric pressure, and the contact between the high voltage terminal and the battery element is enhanced. A bipolar battery was completed.

Example 2
(1) Production of negative electrode A negative electrode was produced in the same manner as in Example 1 (1).

(2) Impregnation with electrolyte (1) In the same manner as in Example 1 (2), the negative electrode produced in (1) was impregnated with gel electrolyte (1).

(3) Production of positive electrode A positive electrode was produced in the same manner as in Example 1 (3).

(4) Impregnation of electrolyte (2 ′) EC: PC (1: 1 vol%) (85 wt%) containing 1 M / L LiPF ₆ as a supporting salt as an electrolyte and PVdF-HFP (15 wt%) as a host polymer The mixture was mixed, DMC was added as a solvent to the mixture, and the mixture was sufficiently stirred to obtain a gel electrolyte (2 ′). This gel electrolyte (2 ′) was applied to the positive electrode prepared in (3) above, and DMC was dried, so that the gel electrolyte (2 ′) was impregnated in the positive electrode. In addition, the compressive stress at the time of 50% strain of the gel electrolyte (2 ′) used here was 0.628 MPa.

(5) Production of gel polymer electrolyte layer A gel polymer electrolyte layer was produced in the same manner as in Example 1 (5).

(6) Production of Bipolar Secondary Battery A bipolar secondary battery was produced in the same manner as in Example 1 (6).

Comparative Example 1
(1) Production of negative electrode A negative electrode was produced in the same manner as in Example 1 (1).

(2) Production of positive electrode A positive electrode was produced in the same manner as in Example 1 (3).

(3) Production of bipolar secondary battery The negative electrode produced in (1) above, a 95 × 95 mm separator (polyolefin microporous membrane, thickness: 20 μm), and the positive electrode produced in (2) above were laminated, A PE-made film having a width of 12 mm was placed around it to obtain a sealing material. After laminating three layers of such bipolar electrodes, the seal part was pressed from above and below (press conditions: 0.2 MPa, 160 ° C., 5 s) and fused to seal each layer.

A high voltage terminal having a portion in which a part of a 100 μm Al plate of 130 mm × 80 mm capable of covering the entire projection surface of the bipolar battery element extended to the outside of the battery projection surface was produced. Next, the power storage element was placed inside the exterior of an aluminum laminate film formed to the size of the power storage element, leaving one side for pouring the electrolyte, and heat-sealing the remaining three sides to form a bag. A predetermined amount of electrolyte was injected and impregnated therein, and the remaining one side was vacuum-sealed to produce a bipolar battery. The electrolyte is LiPF, which is a lithium salt, in a solution obtained by mixing propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) at PC: EC: DEC = 1: 1: 2 (volume ratio). A solution in which ₆ was dissolved to a concentration of 1M was used.

Comparative Example 2
(1) Production of negative electrode A negative electrode was produced in the same manner as in Example 1 (1).

(2) Impregnation of electrolyte (2 ′) A gel electrolyte (2 ′) was prepared in the same manner as in Example 2 (4). Further, in the same manner as in Example 2 (4), the gel electrolyte (2 ′) was impregnated in the negative electrode prepared in (1).

(3) Production of positive electrode A positive electrode was produced in the same manner as in Example 1 (3).

(4) Impregnation of electrolyte (2 ′) A gel electrolyte (2 ′) was prepared in the same manner as in Example 2 (4). Further, in the same manner as in Example 2 (4), the gel electrolyte (2 ′) was impregnated in the positive electrode prepared in (3).

(5) Production of gel polymer electrolyte layer A gel polymer electrolyte layer was produced in the same manner as in Example 1 (5).

(6) Production of Bipolar Secondary Battery Example 1 above except that the negative electrode produced in (2) above, the gel polymer electrolyte layer produced in (5) above, and the positive electrode produced in (4) above were used. A bipolar secondary battery was produced in the same manner as (6).

Comparative Example 3
(1) Production of negative electrode A negative electrode was produced in the same manner as in Example 1 (1).

(2) Impregnation of electrolyte (1 ″) EC: PC (1: 1 vol%) (76 wt%) containing 1 M / L LiPF ₆ as a supporting salt as an electrolyte and PVdF-HFP (24 wt%) as a host polymer The mixture was mixed, DMC was added as a solvent to the mixture, and the mixture was sufficiently stirred to obtain a gel electrolyte (1 ″). The gel electrolyte (1 ″) was applied to the negative electrode prepared in the above (1), and the DMC was dried to impregnate the negative electrode with the gel electrolyte (1 ″). In addition, the compressive stress at the time of 50% strain of the gel electrolyte (1 ″) used here was 1.988 MPa.

(3) Production of positive electrode A positive electrode was produced in the same manner as in Example 1 (3).

(4) Impregnation of electrolyte (1 ″) Gel electrolyte (1 ″) prepared in the same manner as in (2) above was applied to the positive electrode prepared in (3) above, and the DMC was dried, whereby gel electrolyte (1 ") Was impregnated into the positive electrode.

(5) Production of gel polymer electrolyte layer A gel polymer electrolyte layer was produced in the same manner as in Example 1 (5).

(6) Production of Bipolar Secondary Battery Example 1 above except that the negative electrode produced in (2) above, the gel polymer electrolyte layer produced in (5) above, and the positive electrode produced in (4) above were used. A bipolar secondary battery was produced in the same manner as (6).

(Evaluation)
The bipolar secondary batteries obtained in Examples 1 and 2 and Comparative Examples 1 to 3 were evaluated for charge / discharge efficiency and long-term reliability.

The charge / discharge test was performed in the following order:
1: Constant current charging (charging to a predetermined voltage with a predetermined current. After that, the voltage is held so that the total charging time is 8 hours.)
2: Pause (pause for 10 minutes)
3: Constant voltage discharge (discharge to a predetermined voltage with a predetermined current)
4: Set to rest (pause for 10 minutes). The charging current is 0.2C, the charging voltage is 4.2V, and the discharging voltage is 2V. Here, 1C is a current value at which the battery is fully charged (100% charged) when charged at that current value for 1 hour. For example, 2C is a current value that is twice that of 1C, and is a current value that can fully charge the battery in 30 minutes. In addition, the discharge current of the first cycle was 0.2C, the second cycle was 0.5C, and the third and subsequent cycles were 1C.

  The discharge efficiency is the ratio of the discharge capacity when the polymer electrolyte is used when the discharge capacity is 100% when only the liquid electrolyte is used as the electrolyte and charged at 0.2C and discharged at 0.2C { That is, discharge efficiency (%) = [(discharge capacity when using polymer electrolyte) / (discharge capacity when using only liquid electrolyte as electrolyte)] × 100}.

  The results are shown in Table 1 below. In the following Table 1, the charge / discharge efficiency in the long-term reliability was set to 100% of Comparative Example 1 in each cycle.

  From the results of Table 1 above, it can be seen that the battery of the present invention exhibits excellent charge / discharge efficiency and long-term reliability.

1 is a schematic cross-sectional view schematically showing an outline of a laminated flat non-bipolar lithium ion secondary battery which is a typical embodiment of a lithium ion battery of the present invention. It is the cross-sectional schematic which represented typically the outline | summary of the laminated flat bipolar lithium ion secondary battery which is another typical embodiment of the lithium ion battery of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view schematically showing an appearance of a stacked flat lithium ion secondary battery which is a typical embodiment of a lithium ion battery according to the present invention. 4A and 4B are external views schematically showing typical embodiments of the assembled battery according to the present invention, in which FIG. 4A is a plan view of the assembled battery, FIG. 4B is a front view of the assembled battery, and FIG. It is a side view of a battery. It is a conceptual diagram of the vehicle carrying the assembled battery of this invention.

Explanation of symbols

10 ... Lithium ion secondary battery,
11 ... positive electrode current collector,
11a: outermost positive electrode current collector,
12, 32 ... positive electrode (positive electrode active material layer),
13, 35 ... electrolyte layer,
14 ... negative electrode current collector,
15, 33 ... negative electrode (negative electrode active material layer),
16, 36 ... single cell layer (= battery unit or single cell),
17, 37, 57 ... battery element (power generation element; laminate),
18, 38, 58 ... positive electrode tab,
19, 39, 59 ... negative electrode tab,
20, 40 ... positive terminal lead,
21, 41 ... negative terminal lead,
22, 42, 52 ... battery exterior materials,
30 ... Bipolar lithium-ion battery,
31 ... current collector,
31a ... outermost layer current collector on the positive electrode side,
31b ... outermost layer current collector on the negative electrode side,
34 ... Bipolar electrode,
34a, 34b ... electrodes located in the outermost layer,
43 ... Seal part (insulating layer),
50 ... lithium ion battery,
250 ... small battery pack,
300 ... assembled battery,
310 ... connection jig,
400: Electric car.

Claims (10)

A single battery layer in which a positive electrode in which a positive electrode active material layer is formed on the surface of a current collector and a negative electrode in which a negative electrode active material layer is formed on the surface of the current collector are stacked via an electrolyte layer A non-aqueous electrolyte secondary battery having a battery element,
A non-aqueous electrolyte in which the compressive stress at 50% strain of the electrolyte (1) used in the negative electrode active material layer is smaller than the compressive stress at 50% strain of the electrolyte (2) used in the positive electrode active material layer Secondary battery.   The nonaqueous electrolyte secondary battery according to claim 1, wherein at least one of the electrolytes (1) and (2) is a solid polymer electrolyte.   The ratio of the compressive stress at 50% strain of the electrolyte (2) to the compressive stress at 50% strain of the electrolyte (1) is more than 1 and 100 or less. Water electrolyte secondary battery.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein a compressive stress at 50% strain of the electrolyte (1) is 0.01 to 2.5 MPa. The electrolyte layer has a separator,
The separator is impregnated with an electrolyte whose compressive stress at 50% strain is equal to or lower than the compressive stress at 50% strain of the electrolyte (2) used in the positive electrode active material layer. The nonaqueous electrolyte secondary battery according to item.   The non-aqueous electrolyte secondary battery according to claim 5, wherein the separator is impregnated with an electrolyte (1) used in a negative electrode active material layer. The positive electrode active material layer includes a lithium-transition metal composite oxide as an active material,
The negative electrode active material layer includes at least one selected from the group consisting of a carbon material, Al, Si, Ge, Sn, Pb, In, and Zn as an active material. The nonaqueous electrolyte secondary battery according to item.   The nonaqueous electrolyte secondary battery according to claim 1, which is a bipolar secondary battery.   The assembled battery using the nonaqueous electrolyte secondary battery as described in any one of Claims 1-8.   The vehicle which mounts the nonaqueous electrolyte secondary battery of any one of Claims 1-8, or the assembled battery of Claim 9 as a motor drive power supply.

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