JP5807779B2 - Non-aqueous secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous secondary battery.

  In the present specification, the “secondary battery” generally refers to a battery that can be repeatedly charged and includes so-called storage batteries such as lithium secondary batteries (typically lithium ion secondary batteries) and nickel metal hydride batteries. In the present specification, the “active material” refers to reversibly occlusion and release (typically insertion and removal) of a chemical species that serves as a charge carrier in a secondary battery (for example, lithium ions in a lithium ion secondary battery). A possible substance. Further, the “non-aqueous secondary battery” refers to a secondary battery in which a non-aqueous electrolyte (for example, a non-aqueous electrolyte) is used as an electrolyte.

  As a non-aqueous secondary battery, for example, a lithium ion secondary battery can realize a relatively high capacity and high output as compared to other secondary batteries such as a nickel metal hydride battery. For this reason, in particular, the importance is increasing as a power source (vehicle-mounted power source) for driving a motor coupled to a driving wheel of the vehicle.

In a lithium ion secondary battery, an electrode active material that reversibly occludes and releases lithium ions is used. As such an electrode active material, it has been proposed to use lithium cobalt composite oxide (LiCoO ₂ ) capable of realizing higher capacity. However, cobalt is a rare material and is relatively expensive. In order to supply lithium ion secondary batteries stably, we want to keep the ratio depending on cobalt low. For this reason, lithium-nickel-cobalt-manganese in which a part of cobalt (Co) of lithium cobalt composite oxide (LiCoO ₂ ) already put into practical use is replaced with cheaper nickel (Ni) or manganese (Mn). It has been proposed to use complex oxides.

  Furthermore, it has also been proposed to use a lithium-nickel-cobalt-manganese composite oxide containing tungsten (W). For example, in Japanese Patent Application Laid-Open No. 2009-140787 (Patent Document 1), tungsten-containing lithium-nickel-cobalt-manganese composite oxide increases the generation of gas during high-temperature storage due to the inclusion of tungsten. This publication discloses that niobium (Nb) is further added to the tungsten-containing lithium-nickel-cobalt-manganese composite oxide in order to suppress the generation of such gas.

  Moreover, in a lithium ion secondary battery, for example, a polyolefin microporous film may be disposed as a separator between a positive electrode and a negative electrode. Such a polyolefin microporous membrane has an oxidizing atmosphere in the vicinity of the positive electrode surface when the charging voltage is set to 4.25 V or more. As a result, the nonaqueous electrolyte material and separator that are in physical contact with the positive electrode are susceptible to oxidative decomposition. As a result, the internal resistance of the lithium ion secondary battery increases and the battery characteristics deteriorate. In contrast, JP 2007-188777 A (Patent Document 2) provides an oxidation resistance by providing a resin layer having an inorganic substance on at least one principal surface of a base material layer of a separator, and oxidative decomposition of the separator. In addition, it has been proposed to suppress deterioration of battery characteristics.

JP 2009-140787 A JP 2007-188777 A

  By the way, the capacity | capacitance of a lithium ion secondary battery may fall by repeating charging and discharging, for example. Moreover, the metal element which comprises a positive electrode active material can be gradually eluted in electrolyte solution. The inventor believes that the eluted metal element is deposited on the negative electrode and fixed to the negative electrode by alloying with lithium ions, etc., so that the battery capacity of the lithium ion secondary battery is increased by repeating charging and discharging. I think it will be one of the causes of the decline. Further, the present inventor has obtained knowledge that a phenomenon in which the battery capacity of the lithium ion secondary battery is reduced is particularly noticeable when the positive electrode active material contains manganese (Mn).

  A non-aqueous secondary battery according to the present invention includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, a battery case in which the positive electrode and the negative electrode are accommodated, and a non-aqueous acid accommodated in the battery case. With electrolyte. Here, the positive electrode has as a positive electrode active material containing at least manganese and tungsten. Further, the non-aqueous secondary battery includes boehmite between the positive electrode and the negative electrode. Here, boehmite may be contained in the separator. Boehmite may be arranged on the surface of the separator on the negative electrode side.

  Further, when a heat resistant layer (HRL) is interposed between the positive electrode and the negative electrode, boehmite may be included in the heat resistant layer. Here, the heat resistant layer is a porous layer containing an insulating metal oxide having heat resistance. The heat-resistant layer is mainly used for the purpose of preventing the oxidative decomposition of the separator that leads to an internal short circuit and the deterioration of battery characteristics. Typically, a porous heat-resistant layer made of an inorganic filler (for example, an insulating metal oxide) and a small amount of a binder is formed on a resin porous substrate. Moreover, the heat-resistant layer may be provided on at least one surface of the positive electrode, the negative electrode, and the separator, for example. The above heat-resistant layer is often provided on the surface (one surface) of the positive electrode, the negative electrode, or the separator from the viewpoint of simplifying the battery structure or the manufacturing process and the effect of preventing a short circuit. Boehmite may be a filler.

  The present inventor has found that it is preferable to provide boehmite between the positive electrode and the negative electrode, especially when the positive electrode active material contains manganese and tungsten. In this case, the present inventors imagine that tungsten eluted from the positive electrode is attracted to the surface of boehmite. Furthermore, the manganese eluted from the positive electrode is attracted to boehmite by tungsten attracted to the surface of boehmite. Thus, as a result, boehmite can capture manganese eluted from the positive electrode. And it is thought that the quantity of manganese which finally reaches a negative electrode decreases.

Here, boehmite (Boehmite) the composition formula: alumina monohydrate represented by AlOOH or _{Al 2 O 3 · H 2 O} . It is insoluble in water, hardly reacts with acids and alkalis at room temperature, has excellent chemical stability, and hydrated water does not dehydrate to around 450 ° C. and has high heat resistance. Further, when a heat-resistant layer is interposed between the positive electrode and the negative electrode, boehmite may be included in the heat-resistant layer. In this case, boehmite is good to be contained in the heat-resistant layer in the form of a filler, for example. Boehmite may be arranged on the surface of the separator on the negative electrode side.

Hereinafter, tungsten is appropriately described as “W”, and manganese is appropriately described as “Mn”. In a preferred embodiment of the non-aqueous secondary battery disclosed herein, the positive electrode active material is a Mn-containing Li composite oxide containing W. Typically, for example, Li _x Mn _3-x in which Mn element in LiMn ₂ O ₄ having a spinel structure or LiMnO ₂ having a layered structure is replaced with W and another element M (preferably a transition metal element). _{-y-z M y W z O} 4 and _{Li (Mn 1-x-y} M x W y) of the _{O 2} and the like can be exemplified. Thus, when the positive electrode active material contains Mn, Mn eluted from the positive electrode active material can be removed by the presence of both W and boehmite. According to the non-aqueous secondary battery using such a positive electrode active material, it is possible to maintain excellent output characteristics of, for example, a 4.2 V level and a high capacity.

  Moreover, the non-aqueous secondary battery disclosed here is suitable as a vehicle driving battery. The non-aqueous secondary battery disclosed herein can achieve higher capacity and improved cycle characteristics by the configuration as described above. For this reason, it is equipped with performance suitable as a battery mounted on a vehicle that requires high-rate charge / discharge. Therefore, according to the present invention, it is possible to provide a vehicle (for example, an automobile) provided with the non-aqueous secondary battery as a power source (typically, a power source of a hybrid vehicle or an electric vehicle).

It is sectional drawing which shows typically the cross section of the lithium ion secondary battery which concerns on one Embodiment of this invention. It is sectional drawing which shows typically the cross section of the lithium ion secondary battery which concerns on other embodiment of this invention. It is a side view showing typically a vehicle provided with a lithium ion secondary battery concerning one embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

  FIG. 1 is a schematic cross-sectional view showing a configuration of a lithium ion secondary battery 10 (non-aqueous secondary battery) according to an embodiment of the present invention. The lithium ion secondary battery 10 includes, for example, a positive electrode 12 (typically a positive electrode sheet), a negative electrode 14 (typically a negative electrode sheet), and a positive electrode 12 and a negative electrode 14, as shown in FIG. And a battery case 15 in which the positive electrode 12 and the negative electrode 14 are accommodated, and a nonaqueous electrolyte (not shown) accommodated in the battery case 15. Here, the positive electrode 12 has a positive electrode active material containing at least manganese (Mn) and tungsten (W). The nonaqueous secondary battery 10 includes a boehmite 30 between the positive electrode 12 and the negative electrode 14.

  According to the non-aqueous secondary battery disclosed herein, the problem of reduction in battery capacity in the positive electrode active material containing manganese is solved, and the excellent high output characteristics inherent in the non-aqueous secondary battery 10 are expressed over a long period of time. Can do. The nonaqueous secondary battery 10 according to the present invention is not limited to the structure shown in FIG. The structure of the nonaqueous secondary battery 10 disclosed in FIG. 1 will be described in detail later. Here, with reference to FIG. 1 as appropriate, each component of the nonaqueous secondary battery according to an embodiment of the present invention, such as the positive electrode 12, the negative electrode 14, and the separator 13, will be described in order.

[Positive electrode 12]
As the positive electrode 12 (typically, a positive electrode sheet), a form in which a positive electrode active material layer 124 containing a positive electrode active material is formed on a positive electrode current collector 122 as shown in FIG. 1 can be used.

  As the positive electrode current collector 122, a rod-like body, a plate-like body, a foil-like body, a net-like body, or the like mainly composed of aluminum, nickel, titanium, stainless steel, or the like can be used.

  Further, in the nonaqueous secondary battery disclosed herein, the positive electrode active material is an active material capable of reversibly occluding and releasing chemical species serving as charge carriers (for example, lithium ions in a lithium ion secondary battery). . In this embodiment, any material that can reversibly store and release Li (typically insertion and removal) as described above and includes at least Mn in its chemical composition may be used.

  As such a material, for example, when the non-aqueous secondary battery is a lithium ion secondary battery, a lithium transition metal composite oxide having a layered structure that can be used for a positive electrode of a general lithium secondary battery, a spinel structure Of these, a substance containing Mn can be preferably used among the lithium transition metal composite oxides, polyanion compounds having an olivine structure, and the like.

The positive electrode active material contains W. As such a positive electrode active material, for example, lithium containing lithium and a transition metal element as constituent metal elements such as lithium nickelate (LiNiO ₂ ), lithium cobaltate (LiCoO ₂ ), lithium manganate (LiMnO ₂ ), and the like. Examples thereof include a solid solution in which W and Mn, which are transition metal elements, are dissolved in a positive electrode active material mainly composed of a transition metal oxide.

For example, a solid solution in which a part of Mn of lithium manganate is replaced by W, a part of Ni site of LiNiO ₂ such as LiNi _1- abc Co _a Mn _b W _c O ₂ is replaced by Co, Mn and W Based on Li ₂ MnO ₃ such as Li (Li ₁ -abc _cd Mn _a Co _b Nic W _d ) O ₂ , W was dissolved in LiNiO ₂ or LiCoO ₂ . Examples include high manganese-containing solid solutions. In particular, the lithium-nickel-cobalt-manganese composite oxide containing W, represented by the general formula: Li (Li ₁ -abc _cd Mn _a Co _b Ni _c W _d ) O ₂ , It has excellent output characteristics and has preferable performance as an active material constituting a positive electrode for a non-aqueous secondary battery.

In addition to those disclosed above, a positive electrode active material mainly composed of an olivine-type phosphate compound containing W and Mn is also preferably used. Preferable examples include lithium manganese phosphate (LiMnPO ₄ or the like) with W added.

  The positive electrode active material layer 124 is a layer in which the positive electrode active material described above is attached to the positive electrode current collector 122 together with, for example, a binder and a conductive material used as necessary.

  Various known binders can be used as the binder. As the binder, a water-soluble polymer material that dissolves in water can be used. Examples of water-soluble polymer materials that are soluble in water include carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC), hydroxypropylmethylcellulose phthalate (HPMCP), and polyvinyl alcohol. (PVA).

  For the binder, a polymer material that is dispersed in water (water-dispersible) may be suitably used. Examples of polymer materials that are dispersed in water (water-dispersible) include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene-hexafluoropropylene copolymer. Fluorine resin such as coalescence (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), vinyl acetate copolymer, styrene butadiene block copolymer (SBR), acrylic acid modified SBR resin (SBR latex), Arabic Examples thereof include rubbers such as rubber and organic binders (PVDF). Although the usage-amount of a binder is not specifically limited, For example, it can be set as 0.5-10 mass parts with respect to 100 mass parts of positive electrode active materials.

  Examples of the conductive material include carbon black (for example, acetylene black), carbon material such as graphite powder, or conductive metal powder such as nickel powder. These may be used individually by 1 type, and 2 or more types may be used together. Although it does not specifically limit also about the usage-amount of an electrically conductive material, For example, setting it as 1-20 mass parts (preferably 5-15 mass parts) with respect to 100 mass parts of positive electrode active materials is illustrated.

[Negative electrode 14]
As shown in FIG. 1, the negative electrode 14 (typically, a positive electrode sheet) can be used in a form in which a negative electrode active material layer 144 containing a negative electrode active material is formed on a negative electrode current collector 142.

  As the negative electrode current collector 142, a rod-like body, a plate-like body, a foil-like body, a net-like body, or the like mainly composed of copper, nickel, titanium, stainless steel, or the like can be used.

  The negative electrode active material layer 144 is a layer in which a negative electrode active material is attached to the negative electrode current collector 122 together with, for example, a binder and a conductive material used as necessary. For the binder of the negative electrode 14, the same materials as those mentioned for the binder of the positive electrode 12 can be appropriately used. Examples thereof include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), and styrene butadiene rubber (SBR). As for the conductive material, similarly to the positive electrode, a carbon material such as carbon black can be preferably used.

  As the negative electrode active material, one type or two or more types of materials conventionally used for lithium ion secondary batteries can be used without any particular limitation. For example, a particulate carbon material (carbon particles) including a graphite structure (layered structure) at least in part. More specifically, the negative electrode active material is, for example, natural graphite, natural graphite coated with an amorphous carbon material, graphite (graphite), non-graphitizable carbon (hard carbon), graphitizable carbon ( Soft carbon) or a carbon material combining these may be used.

  Moreover, various metal compounds (for example, metal oxides) can be used as the negative electrode active material, for example. Here, the metal compound is specifically exemplified by a metal compound (preferably a metal oxide) containing Si, Ge, Sn, Pb, Al, Ga, In, As, Sb, Bi, or the like as a constituent metal element. The Further, for example, a granular negative electrode active material whose surface is sufficiently covered with a carbon film and excellent in conductivity can be suitably used. In this case, the conductive auxiliary material is not contained in the negative electrode active material layer, or the content of the conductive auxiliary material can be reduced as compared with the conventional case. Although the usage-amount of a conductive support material is not specifically limited, For example, about 1-30 mass parts (preferably about 2-20 mass parts, for example, 5-10 masses) with respect to 100 mass parts of negative electrode active materials to be used. Part). A conductive auxiliary material may be previously contained in the electrode active material supply material described above.

[Separator 13]
The separator 13 is interposed between the positive electrode 12 and the negative electrode 14. As the separator 13, a porous sheet made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, polyamide or the like, a nonwoven fabric, or the like can be used. Preferable examples include those composed of a porous polyolefin resin. For example, a porous separator sheet made of synthetic resin (for example, made of polyolefin such as polyethylene) can be suitably used. When a solid electrolyte or a gel electrolyte described later is used as the electrolyte, a separator may not be necessary (that is, in this case, the electrolyte itself can function as a separator).

  In the example shown in FIGS. 1 and 2, the separator 13 is formed of a sheet-like member. The separator 13 may be a member that insulates the positive electrode active material layer 124 and the negative electrode active material layer 144 and allows the electrolyte to move. Therefore, the separator 13 is not limited to a sheet-like member. For example, the separator 13 may be formed of a layer of particles having insulating properties formed on the surface of the positive electrode active material layer 124 or the negative electrode active material layer 144 instead of the sheet-like member. Here, as the particles having insulating properties, inorganic fillers having insulating properties (for example, fillers such as metal oxides and metal hydroxides) or resin particles having insulating properties (for example, particles such as polyethylene and polypropylene) ).

[Nonaqueous electrolyte]
As the nonaqueous electrolyte, a liquid electrolyte containing a nonaqueous solvent and a lithium salt soluble in the solvent is preferably used. It may be a solid (gel) electrolyte in which a polymer is added to such a liquid electrolyte. As the non-aqueous solvent, aprotic solvents such as carbonates, esters, ethers, nitriles, sulfones, and lactones can be used. For example, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, 1,3-dioxolane, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, acetonitrile, propionitrile, nitromethane, N, N-dimethylformamide, dimethyl sulfoxide, sulfolane, γ-butyrolactone, etc. One kind or two or more kinds selected from non-aqueous solvents known to be usable for the electrolyte of the secondary battery can be used.

Lithium salts include LiPF ₆ , LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC (SO ₂ CF ₃ ) ₃ , LiClO _4, etc., one or more selected from various lithium salts known to be capable of functioning as a supporting electrolyte in the electrolyte of a lithium ion secondary battery can be used. The concentration of the lithium salt is not particularly limited, and can be the same as, for example, the electrolyte used in a conventional lithium ion secondary battery. Usually, a non-aqueous electrolyte containing a supporting electrolyte (lithium salt) at a concentration of about 0.1 mol / L to 5 mol / L (for example, about 0.8 mol / L to 1.5 mol / L) is preferably used. it can.

[Boehmite 30]
Further, in the nonaqueous secondary battery disclosed herein, boehmite 30 is disposed between the positive electrode 12 and the negative electrode 14. Here, the positive electrode active material contains tungsten, and the boehmite 30 has a function of removing Mn eluted from the positive electrode 12 before reaching the negative electrode 14 in relation to the tungsten. Thereby, battery deterioration resulting from elution of Mn can be effectively suppressed.

  The boehmite 30 is a chemically stable inorganic material that is insoluble in water and hardly reacts with acids and alkalis at room temperature. In the lithium ion secondary battery 10 disclosed here, the positive electrode active material contains tungsten, and the boehmite 30 is disposed between the positive electrode 12 and the negative electrode 14. In the form shown in FIG. 1, a layer containing boehmite 30 is formed on the surface of the separator 13.

  In this case, even when charging / discharging of the lithium ion secondary battery is repeated and Mn is eluted from the positive electrode 12, Mn reaching the negative electrode 14 can be reduced. Although the action of such boehmite 30 has not been completely elucidated, the present inventor assumes the following event.

  That is, the boehmite 30 attracts tungsten among the metal elements eluted from the positive electrode 12 into the nonaqueous electrolyte. Subsequently, Mn eluted from the positive electrode 12 is attracted to the boehmite due to the presence of tungsten attracted to the boehmite 30. Thereby, before Mn eluted from the positive electrode 12 reaches the negative electrode 14, Mn is removed from the electrolytic solution, and the amount of Mn reaching the negative electrode 14 can be reduced. As a result, battery deterioration due to Mn eluting from the positive electrode can be effectively suppressed.

  Since boehmite is usually provided in the form of a powder, in the non-aqueous secondary battery disclosed herein, the boehmite powder is mixed with a binder (thickening agent if necessary) and deposited on a suitable substrate. It is good to let them. In the form shown in FIG. 1, for example, a separator 13 is used as a substrate on which boehmite powder is applied. The separator 13 is interposed between the positive electrode 12 and the negative electrode 14 and is suitable as a base material on which boehmite powder is applied.

  The boehmite powder may be applied to the surface of the positive electrode 12 (specifically, the positive electrode active material layer 124), for example, as shown in FIG. As shown in FIG. 2, when boehmite powder is applied to the surface of the positive electrode 12, it is possible to prevent Mn eluted from the positive electrode 12 from being diffused elsewhere. Moreover, although illustration is abbreviate | omitted, you may apply | coat boehmite powder to the surface of the negative electrode 14 (specifically negative electrode active material layer 144), for example.

  Moreover, the boehmite 30 should just be arrange | positioned between the positive electrode 12 and the negative electrode 14, and as above-mentioned, may be provided in at least one surface among the positive electrode 12, the negative electrode 14, and the separator 13. As shown in FIG. Alternatively, a base material coated with boehmite 30 may be prepared separately and interposed between the positive electrode 12 and the negative electrode 14.

[Heat resistant layer]
In the non-aqueous secondary battery disclosed herein, a heat-resistant layer may be disposed between the positive electrode 12 and the negative electrode 14. In this case, the boehmite 30 may be included in the heat resistant layer.

In this case, the configuration of the heat-resistant layer is not particularly limited, but typically, a material in which an inorganic substance (inorganic filler) is attached to a suitable base material together with a small amount of heat-resistant binder is preferably used. be able to. As the matrix resin for the heat-resistant layer, for example, known matrix resins such as polyvinylidene fluoride (PVdF), hexafluoropropylene (HFP), polytetrafluoroethylene (PTFE), and copolymers thereof are generally used. Yes. As the inorganic material, for example, various metals, semiconductors, or oxides and nitrides thereof are generally used. Specifically, for example, alumina (Al ₂ O ₃ ), boron nitride (BN), aluminum nitride (AlN), titanium dioxide (TiO ₂ ) _, silicon dioxide (SiO ₂ ), etc. exhibit insulating properties and are available. Since it is easy, it is preferably used.

  In the nonaqueous secondary battery disclosed herein, the heat-resistant layer may be provided on at least one surface of, for example, a positive electrode, a negative electrode, and a separator. Thus, the heat-resistant layer is disposed between the positive electrode and the negative electrode. Therefore, boehmite may be provided in such a heat-resistant layer. In this case, by arranging an appropriate amount of boehmite on the heat-resistant layer almost uniformly, the Mn element eluted from the positive electrode can be supplemented by the heat-resistant layer. In addition, boehmite can be more easily and more effectively arranged in the non-aqueous secondary battery, and the effects of the configuration of the present invention can be more reliably exhibited.

  In such a non-aqueous secondary battery, boehmite powder may be used as one of the inorganic substances constituting the heat-resistant layer, and the boehmite may be included in the heat-resistant layer. In this case, all the inorganic substances constituting the heat-resistant layer may be boehmite, or other inorganic substances and boehmite may be used in combination. The heat-resistant layer may have a multilayer structure, and one of them may include a layer made of boehmite. As a result, in addition to the function of suppressing oxidative decomposition and deterioration of battery characteristics in the heat-resistant layer, it is possible to have a function of suppressing a decrease in battery capacity due to Mn, and a non-aqueous secondary battery having a simpler configuration is provided. The

  A non-aqueous secondary battery (lithium ion secondary battery) is constructed by housing the positive electrode and the negative electrode together with an electrolyte in an appropriate container (a metal or resin casing, a bag made of a laminate film, or the like). In a typical configuration of the nonaqueous secondary battery disclosed herein, a separator is interposed between the positive electrode and the negative electrode. The shape (outer shape of the container) of the non-aqueous secondary battery is not particularly limited, and may be, for example, a cylindrical shape, a square shape, a coin shape, or the like.

  The technique disclosed as described above is characterized by using a substance containing W and Mn as a positive electrode active material, and further disposing boehmite between the positive electrode and the negative electrode. Therefore, as long as the object of the present invention can be realized, the material, shape, and the like of other battery components are not particularly limited, and are the same as those of conventional non-aqueous secondary batteries (typically lithium ion secondary batteries). Can consider changes.

  Hereinafter, as a preferred embodiment of the non-aqueous secondary battery disclosed herein, the lithium ion secondary battery shown in FIG. 1 will be described more specifically.

  FIG. 1 is a schematic cross-sectional view showing the configuration of the lithium ion secondary battery according to this embodiment. The lithium ion secondary battery 10 includes a battery case 15 having a shape in which an electrode body 11 including a positive electrode 12 and a negative electrode 14 can accommodate the electrode body 11 together with a non-aqueous electrolyte (for example, a non-aqueous electrolyte) (not shown). It has the structure accommodated in.

[Battery case 15]
The battery case 15 includes a bottomed cylindrical case main body 152 and a lid 154 that closes the opening. The case main body 152 and the lid body 154 are both made of metal and insulated from each other. In the lithium ion secondary battery 10, the lid 154 also serves as a positive electrode terminal, and the case main body 152 serves as a negative electrode terminal.

  The electrode body 11 includes a long sheet-like (band-like) positive electrode (positive electrode sheet) 12 and a long sheet-like (band-like) negative electrode (negative electrode sheet) 14 superimposed on two long sheet-like separators 13. These are formed by winding them into a cylindrical shape. Here, the positive electrode 12 has a positive electrode active material layer 124 containing a positive electrode active material formed on both surfaces of a long sheet-like positive electrode current collector 122 (for example, an aluminum foil). In the negative electrode 14, a negative electrode active material layer 144 containing a negative electrode active material is formed on both surfaces of a long sheet-like negative electrode current collector 142 (for example, copper foil).

  At one edge along the longitudinal direction of the positive electrode current collector 122, a portion where the current collector 122 is exposed without providing the positive electrode active material layer 124 (positive electrode active material layer non-forming portion) is provided. Similarly, on one edge along the longitudinal direction of the negative electrode current collector 142, a portion where the negative electrode active material layer is not provided but the current collector 142 is exposed (negative electrode active material layer non-forming portion) is provided. . As shown in FIG. 1, the positive and negative electrode sheets 12, 14 are formed by superimposing both composite material layers 142, 144, and the active material layer non-formation portions of both electrode sheets are one end and the other along the longitudinal direction of the separator 13. The positions are slightly shifted in the width direction so as to protrude from the end portions.

  A portion of the positive electrode sheet 12 where the positive electrode current collector 122 protrudes from the separator 13 is electrically connected to a lid 154 as a positive electrode terminal. Further, a portion of the negative electrode sheet 14 where the negative electrode current collector 142 protrudes from the separator 13 is electrically connected to a case main body 152 as a negative electrode terminal.

  Here, in the lithium ion secondary battery 10 shown in FIG. 1, a heat-resistant layer containing boehmite 30 is formed on the surface of the separator 13. In the lithium ion secondary battery 10 shown in FIG. 2, a heat-resistant layer containing boehmite 30 is formed on the surface of the positive electrode 12 (specifically, the surface of the positive electrode active material layer 124). The battery case 15 accommodates the electrode body 11 and is injected with a non-aqueous electrolyte (non-aqueous electrolyte). Since the non-aqueous electrolyte has already been described, the description thereof is omitted here.

  Thus, the lithium ion secondary battery 10 as the non-aqueous secondary battery contains the positive electrode 12, the negative electrode 14, the separator 13 interposed between the positive electrode 12 and the negative electrode 14, and the positive electrode 12 and the negative electrode 14. Battery case 15 and a nonaqueous electrolyte accommodated in the battery case 15 are provided. The positive electrode 12 has a positive electrode active material containing at least manganese (Mn) and tungsten (W). A boehmite 30 is provided between the positive electrode 12 and the negative electrode 14.

  In the lithium ion secondary battery 10 having such a configuration, a positive electrode active material is formed from the positive electrode 12 into the nonaqueous electrolyte solution for long-term storage (elapse of time), charge / discharge cycles in which charging and discharging are repeated, and the like. Metal elements can be eluted. The lithium ion secondary battery 10 disclosed here contains manganese (Mn) and tungsten (W) in the positive electrode active material, and Mn is eluted from the positive electrode. The lithium ion secondary battery 10 includes boehmite between the positive electrode 12 and the negative electrode 14. For this reason, manganese (Mn) eluted from the positive electrode can be captured by a synergistic effect of tungsten (W) and boehmite. As a result, the amount of Mn that reaches the negative electrode 14 and deposits on the negative electrode 14 is significantly reduced. With such an action, the lithium ion secondary battery 10 disclosed herein is suppressed from the problem of capacity reduction due to elution of the Mn component.

  Hereinafter, as a more specific example, a non-aqueous secondary battery (test battery) disclosed herein was constructed and its performance was evaluated.

<Sample 1>
[Preparation of positive electrode active material]
A manganese-containing lithium composite oxide containing tungsten having a composition represented by the general formula Li (Mn _{0.995 / 3} Ni _{0.995 / 3} Co _{0.995 / 3} W _0.005 ) O ₂ was prepared. That is, lithium acetate dihydrate [Li (CH ₃ COO) · 2H ₂ O] as a lithium source and manganese (II) acetate tetrahydrate [Mn (CH ₃ COO) ₂ · 4H ₂ O], nickel acetate (II) tetrahydrate as a nickel source [Ni (CH ₃ COO) ₂ · 4H ₂ O], and cobalt acetate (II) tetrahydrate as a cobalt source [ Co (CH ₃ COO) ₂ .4H ₂ O] and tungsten oxide WO ₃ as a tungsten source were weighed so as to have a molar ratio shown in the above general formula to prepare starting materials.

Next, these starting materials and glycolic acid (C ₂ H ₄ O ₃ ) are added to pure water, dissolved and diffused, and sufficiently stirred to prepare a raw material mixture. Subsequently, the raw material mixture is heated to 80 ° C. The solution was heated (dried) to evaporate the water and gelled. Then, it heated at 500 degreeC, baked for 5 hours, and grind | pulverized (stirred) with the ball mill. Further, the pulverized product was heated to 800 ° C. and baked for 5 hours, thereby synthesizing a target Mn-containing Li composite oxide (positive electrode active material particles) containing W. The obtained positive electrode active material particles were pulverized to an appropriate particle size.

[Production of positive electrode]
Next, a positive electrode of a test battery was produced.
First, in forming the positive electrode active material layer in the positive electrode, a positive electrode active material layer forming paste was prepared. The synthesized positive electrode active material particles, acetylene black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder are weighed so that the mass% ratio of these materials is 91: 6: 3. In addition to N-methylpyrrolidone (NMP), a positive electrode active material layer forming paste was prepared by mixing. And the said paste was apply | coated to the aluminum foil as a positive electrode electrical power collector, and the water | moisture content in a paste was dried (evaporated). This was stretched into a sheet with a roller press to produce a positive electrode sheet.

[Production of negative electrode]
A negative electrode for a test battery was prepared. Graphite is used as the negative electrode active material, and acetylene black as a conductive material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener have a mass% ratio of these materials. A negative electrode active material layer forming paste was prepared by weighing to 98: 1: 1 and dispersing in ion exchange water. This paste was applied to both sides of a copper foil as a negative electrode current collector, dried, and then pressed to prepare a negative electrode sheet.

[Non-aqueous electrolyte]
The non-aqueous electrolyte is prepared by dissolving 1 mol / L LiPF ₆ in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a volume ratio of 3: 4: 3. Using.

[Preparation of separator]
A polyethylene porous sheet was used as the separator. A paste made of boehmite, a binder, a thickener, and water was applied on the separator sheet, and water in the paste was dried (evaporated) to form a ceramic layer made of boehmite on the separator.

[Construction of lithium secondary battery]
A 18650-type (diameter 18 mm, height 65 mm) cylindrical lithium secondary battery for test was constructed using the prepared positive electrode sheet, negative electrode sheet, and separator. That is, the obtained positive electrode sheet, negative electrode sheet, and two separator sheets are wound so that the ceramic layer of the separator sheet is on the negative electrode side and wound together with the electrolyte solution in a cylindrical container. A lithium secondary battery for testing was constructed.

[Measurement of battery capacity]
Initial battery capacity is 4.1V CCCV (Constant Current / Constant Voltage) charge (1C charge, 4.1V, 10minCV) and 3.0V CCCV discharge (1C discharge, 3.0V, 10minCV) ). That is, in the initial stage of charging, the battery was charged at a constant current (1 C), and when the battery voltage reached 4.1 V, the battery was switched to a constant voltage of 4.1 V and charged for 10 minutes. In the initial stage of discharge, the battery was discharged at a constant current (1 C). When the battery voltage reached 3.0 V, the battery was switched to a constant voltage of 3.0 V and discharged for 10 minutes. Here, “1C” is defined by the amount of current that charges and discharges the capacity of the battery to be measured in one hour.

[Capacity maintenance rate]
The capacity retention rate is obtained by storing a test lithium secondary battery charged to 4.1 V after the first charge / discharge at 60 ° C. for one month, and obtaining the subsequent battery capacity (battery capacity after storage) in the same manner as described above. The ratio of the battery capacity after one month to the initial battery capacity (battery capacity after storage / initial battery capacity) (%) was obtained.

<Sample 2>
A 18650-type test lithium secondary battery was prepared in the same manner as Sample 1, except that when the lithium secondary battery was constructed, the separator sheet was laminated and wound so that the ceramic layer was on the positive electrode side. The above-described capacity retention rate was measured.

<Sample 3>
Except for using α-alumina instead of boehmite, a 18650-type test lithium secondary battery was prepared in the same manner as Sample 1, and the capacity retention rate was measured as described above.
<Sample 4>
A 18650-type test lithium secondary battery was prepared in the same manner as Sample 1 except that Li (Mn _1/3 Ni _1/3 Co _1/3 ) O ₂ not containing W was used as the positive electrode active material. The capacity retention rate was measured.

  The above results are shown in Table 1 below. In addition, W content in Table 1 shows the amount of W contained in the positive electrode active material as a ratio (atomic%) to the total amount of transition metal elements.

  From Table 1, the nonaqueous secondary battery disclosed here uses a Mn-containing Li composite oxide containing W as a positive electrode active material, and further includes boehmite in the battery structure. For this reason, it was confirmed that a high capacity maintenance rate of 90% or more (for one month) was exhibited even in a high temperature environment of 60 ° C. This is, for example, a value higher than that of the secondary battery having the conventional alumina heat-resistant layer of Sample 3, and it can be seen that the problem of capacity reduction is suppressed. In addition, as can be seen from Sample 1 and Sample 2, boehmite is compared between Sample 3 and Sample 4 regardless of whether it is disposed between the negative electrode and the separator or between the positive electrode and the separator. Both exhibit the same excellent effect. Here, boehmite has a tendency that the sample 1 arranged on the surface of the negative electrode side of the separator is more effective than the sample 2 in terms of capacity retention.

  Although the cause of these effects is not clear, W eluted from the positive electrode is attracted to the surface of the ceramic layer due to the acid / basic effects of the surface of the ceramic layer made of boehmite. Next, Mn is attracted to the ceramic layer by the presence of W attracted to the surface of the ceramic layer. As a result, Mn eluted from the positive electrode is attracted to the ceramic layer made of boehmite. This is considered to be due to the difficulty of depositing Mn ions on the negative electrode.

  Note that when this ceramic layer is made of alumina, which is most commonly used as a ceramic material, as can be seen from the results of Sample 3, the effect of suppressing the capacity drop cannot be obtained as compared with the case of using boehmite. Further, as can be seen from the results of Sample 4, even when a ceramic layer made of boehmite is provided, if the positive electrode active material does not contain W, it is not possible to obtain the effect of suppressing the decrease in capacity.

  That is, in the case of using a positive electrode active material containing Mn, addition of W to the positive electrode active material and disposing boehmite between the positive electrode and the negative electrode can suppress a decrease in capacity of the non-aqueous secondary battery. It can be said that the effect can be obtained more reliably.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.

  Any of the non-aqueous secondary batteries disclosed herein may have a performance suitable as a battery mounted on a vehicle, in particular, a high capacity maintenance ratio and an excellent durability. Therefore, according to this invention, as shown in FIG. 3, the vehicle 1 provided with one of the non-aqueous secondary batteries 10 disclosed here is provided. In particular, a vehicle (for example, an automobile) including the non-aqueous secondary battery as a power source (typically, a power source of a hybrid vehicle or an electric vehicle) is provided.

  According to the manufacturing method disclosed herein, it is possible to provide a non-aqueous secondary battery that is excellent in capacity retention rate (that is, cycle characteristics) and can maintain high capacity over a long period of time. By adopting the non-aqueous secondary battery disclosed herein as an in-vehicle secondary battery (particularly, an in-vehicle lithium secondary battery), for example, a vehicle using the non-aqueous secondary battery as a driving power source. Can be provided.

1 Vehicle 10 Lithium ion secondary battery (non-aqueous secondary battery)
11 Electrode body 12 Positive electrode sheet (positive electrode)
13 Separator 14 Negative electrode sheet (negative electrode)
15 Battery case 20 Lithium ion secondary battery (single cell)
30 Boehmite 122 Positive electrode current collector 124 Positive electrode active material layer 142 Negative electrode current collector 144 Negative electrode active material layer

Claims (7)

A positive electrode;
A negative electrode,
A separator interposed between the positive electrode and the negative electrode;
A battery case containing the positive electrode and the negative electrode;
A non-aqueous electrolyte housed in the battery case,
Here, the positive electrode has a manganese-containing lithium composite oxide containing tungsten as a positive electrode active material,
And the non-aqueous secondary battery provided with boehmite between the said positive electrode and the said negative electrode.   The non-aqueous secondary battery according to claim 1, wherein the boehmite is contained in the separator.   The non-aqueous secondary battery according to claim 2, wherein the boehmite is disposed on a negative electrode side surface of the separator. A heat-resistant layer is interposed between the positive electrode and the negative electrode,
The non-aqueous secondary battery according to any one of claims 1 to 3, wherein the boehmite is included in the heat-resistant layer.   The non-aqueous secondary battery according to claim 4, wherein the heat-resistant layer is provided on at least one surface of the positive electrode, the negative electrode, and the separator. The non-aqueous secondary battery according to any one of claims 1 to 5, wherein the boehmite is a filler.   A vehicle drive battery comprising the nonaqueous secondary battery according to any one of claims 1 to 6.

Images