JP6184810B2 - Non-aqueous secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous secondary battery having excellent load characteristics and high initial charge / discharge efficiency.

  In recent years, non-aqueous secondary batteries have been desired to have a high capacity at a low cost so that they can be used as secondary batteries for storage batteries such as industrial machinery or solar power generation systems.

  As one means for meeting the demand for such a non-aqueous secondary battery, by increasing the thickness of the electrode mixture layer (positive electrode mixture layer and negative electrode mixture layer) of the electrodes (positive electrode and negative electrode), There is a method for increasing the capacity of the secondary battery. However, when the thickness of the electrode mixture layer is simply increased, there is a possibility that the capacity cannot be sufficiently extracted during discharge under a high load.

  On the other hand, a technique for improving the load characteristics of a non-aqueous secondary battery by using a non-aqueous electrolyte solvent having good ion conductivity is also known. For example, Patent Documents 1 and 2 disclose a technique in which ethylene carbonate or propylene carbonate and acetonitrile are used in combination with a non-aqueous electrolyte solvent for a non-aqueous secondary battery.

Japanese Unexamined Patent Publication No. 1-54674 JP-A-7-85888

  However, in the non-aqueous secondary battery using a non-aqueous electrolyte containing a nitrile solvent such as acetonitrile, the first charge / discharge efficiency is low, and the present inventor cannot fully utilize the assumed capacity. It became clear by these examinations.

  Therefore, when enhancing the load characteristics of a non-aqueous secondary battery by using a nitrile solvent, development of a technique for suppressing a decrease in the initial charge / discharge efficiency due to the use of the nitrile solvent is also required.

  This invention is made | formed in view of the said situation, The objective is to provide the non-aqueous secondary battery which has the outstanding load characteristic and high initial stage charge / discharge efficiency.

  The non-aqueous secondary battery of the present invention that has achieved the above object is a positive electrode having a positive electrode active material layer on one or both sides of a current collector, a negative electrode having a negative electrode active material layer on one or both sides of the current collector, and , A non-aqueous secondary battery using a non-aqueous electrolyte containing a lithium salt and an organic solvent, wherein the non-aqueous electrolyte has a lithium salt concentration of 2 to 7 mol / l, and the non-aqueous electrolyte is the organic solvent A nitrile solvent and at least one carbonate selected from a cyclic carbonate and a chain carbonate, and each of the negative electrode active material layer and the positive electrode active material layer has an activity of the other electrode. The area of the non-facing portion that does not face the material layer is 15% or less of the area of the facing portion that faces each other.

  According to the present invention, a nonaqueous secondary battery having excellent load characteristics and high initial charge / discharge efficiency can be provided.

It is drawing for demonstrating "the width | variety of the non-opposing part of a negative electrode active material layer" in a laminated electrode body. It is drawing for demonstrating "the width | variety of the non-opposing part of a negative electrode active material layer" in a wound electrode body. It is a top view which represents typically an example of the non-aqueous secondary battery of this invention. It is the sectional view on the AA line of the non-aqueous secondary battery of FIG.

  The nonaqueous secondary battery of the present invention comprises a positive electrode having a positive electrode active material layer on one or both sides of a current collector and a negative electrode having a negative electrode active material layer on one or both sides of the current collector, for example, via a separator. An electrode body made to face each other and a non-aqueous electrolyte containing a lithium salt and an organic solvent are provided. A nitrile solvent is used as the organic solvent for the nonaqueous electrolyte.

  The nitrile solvent has high ion conductivity, and can increase the diffusibility of lithium ions in the battery. Therefore, even in the positive electrode in which the positive electrode active material layer is thickened and the filling amount of the positive electrode active material is increased, the lithium ion can be satisfactorily reached even in the vicinity of the current collector where the lithium ion is difficult to reach during discharge under high load. Can spread. Therefore, a sufficient capacity can be extracted even during high-load discharge, and a non-aqueous secondary battery having excellent load characteristics can be obtained.

  However, on the other hand, when a nitrile solvent is used, lithium ions released from the positive electrode during the initial charge of the non-aqueous secondary battery are diffused throughout the negative electrode due to its high ionic conductivity. . In a non-aqueous secondary battery, since the area of the negative electrode active material layer is generally larger than that of the positive electrode active material layer, the lithium active material layer is not even facing the positive electrode active material layer. If the ions are diffused and occluded, the lithium ions remain in the negative electrode without being released during the first discharge, resulting in an irreversible capacity. Nitrile solvents are highly reactive with the negative electrode surface (the active surface of the negative electrode) and may cause deterioration of the negative electrode.

  For these reasons, in the nonaqueous secondary battery using a nonaqueous electrolyte containing a nitrile solvent, the initial charge / discharge efficiency is lowered.

  Therefore, in the nonaqueous secondary battery of the present invention, (1) the organic solvent of the nonaqueous electrolyte uses at least one carbonate selected from a cyclic carbonate and a chain carbonate together with a nitrile solvent, (2) The lithium salt concentration of the non-aqueous electrolyte is 2 to 7 mol / l. (3) For each of the negative electrode active material layer or the positive electrode active material layer, the areas of the non-opposing portions that do not face the active material layer of the other electrode are It was set as the structure which is 15% or less of the area of the opposing part which opposes.

  By adopting the configurations (1) and (2), the reaction between the nitrile solvent and the negative electrode surface can be suppressed. In addition, by adopting the configuration of (3), it is possible to reduce as much as possible the amount of lithium ions that become irreversible among the lithium ions released from the positive electrode during the initial charge. According to the present invention, by combining the effects of these configurations, even if a positive electrode having a thick positive electrode active material layer is used, the non-aqueous solution has excellent load characteristics and high initial charge / discharge efficiency. It can be set as a secondary battery.

  The non-aqueous electrolyte according to the non-aqueous secondary battery of the present invention contains, as an organic solvent, a nitrile solvent and at least one carbonate selected from cyclic carbonates and chain carbonates.

  Specific examples of nitrile solvents include mononitriles such as acetonitrile, propionitrile, butyronitrile, valeronitrile, benzonitrile, acrylonitrile; malononitrile, succinonitrile, glutaronitrile, adiponitrile, 1,4-dicyanoheptane, 1, 5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 2,6-dicyanoheptane, 1,8-dicyanooctane, 2,7-dicyanooctane, 1,9-dicyanononane, 2,8- Dicyanononane, 1,10-dicyanodecane, 1,6-dicyanodecane, dinitriles such as 2,4-dimethylglutaronitrile; cyclic nitriles such as benzonitrile; alkoxy-substituted nitriles such as methoxyacetonitrile; One of them May be used alone, or in combination of two or more kinds. Among these, mononitrile is more preferable, and acetonitrile is still more preferable.

  Specific examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate (1,2-butylene carbonate, trans-2,3-butylene carbonate, cis-2,3-butylene carbonate), vinylene carbonate, and the like. Specific examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, and ethyl propyl carbonate. The non-aqueous electrolyte may contain only one of the cyclic carbonates and chain carbonates exemplified above, or two or more (two or more of the cyclic carbonates exemplified above, the chain carbonates exemplified above. 2 or more of them, or 1 or more of the cyclic carbonates exemplified above and one or more of the chain carbonates exemplified above). Among these, cyclic carbonate is more preferable, and ethylene carbonate or propylene carbonate is more preferable.

  The content of the nitrile solvent in the total organic solvent of the non-aqueous electrolyte used in the non-aqueous secondary battery is 5 mass from the viewpoint of better ensuring the effect of improving the load characteristics of the non-aqueous secondary battery. % Or more, preferably 10% by mass or more. However, if the amount of the nitrile solvent in the total organic solvent of the non-aqueous electrolyte is too large, for example, the amount of the carbonate solvent is too small, and the action of suppressing the reaction between the nitrile solvent and the negative electrode due to their use. May decrease. Therefore, the content of the nitrile solvent in the total organic solvent of the nonaqueous electrolytic solution used for the nonaqueous secondary battery is preferably 80% by mass or less, and more preferably 40% by mass or less.

  In addition, the content of the carbonate (at least one carbonate selected from cyclic carbonate and chain carbonate) in the total organic solvent of the non-aqueous electrolyte used in the non-aqueous secondary battery is determined by the use of the nitrile solvent. From the viewpoint of better ensuring the effect of suppressing the reaction between the negative electrode and the negative electrode, the content is preferably 10% by mass or more, and more preferably 30% by mass or more. However, if the amount of the carbonate-based solvent in the total organic solvent of the non-aqueous electrolyte is too large, for example, the amount of the nitrile-based solvent is too small, and the effect of improving the load characteristics of the non-aqueous secondary battery due to their use is small. There is a risk of becoming. Therefore, the content of the carbonate in the total organic solvent of the nonaqueous electrolyte used for the nonaqueous secondary battery is preferably 80% by mass or less, and more preferably 60% by mass or less.

  As the organic solvent for the nonaqueous electrolyte, a solvent other than these can be used together with the nitrile solvent and the carbonate solvent. Specific examples of the organic solvent that can be used with the nitrile solvent and the carbonate solvent include: chain esters such as methyl propionate; cyclic esters such as γ-butyrolactone and γ-valerolactone; dimethoxyethane, diethyl ether, 1, Chain ethers such as 3-dioxolane, diglyme, triglyme and tetraglyme; cyclic ethers such as 1,3-dioxane, 1,4-dioxane, tetrahydrofuran and 2-methyltetrahydrofuran; sulfites such as ethylene glycol sulfite; Is mentioned. Further, these compounds may be halogen-substituted products typified by fluorinated products.

Specific examples of the lithium salt of the non-aqueous _{electrolyte, LiClO 4, LiPF 6, LiBOB} , LiAsF 6, inorganic lithium salts such _{LiSbF 6; LiCF 3 SO 3,} LiCF 3 CO 2, Li 2 C 2 F 4 (SO ₃ ) ₂ , LiNC _n F _2n SO ₄ (n ≧ 2), LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (n ≧ ₂ ) 2), an organic lithium salt such as LiN (R _f OSO ₂ ) ₂ [where R _f is a fluoroalkyl group], etc., and only one of these may be used, or two or more of them may be used in combination May be. Among these, when a compound having a phosphorus atom is used, it becomes easier to release a free fluorine atom, and therefore it is more preferable to use LiPF ₆ .

  The concentration of the lithium salt in the non-aqueous electrolyte (when multiple types of lithium salts are used, the total concentration; the same shall apply hereinafter) is 2 mol / l or more from the viewpoint of suppressing the reaction between the nitrile solvent and the negative electrode. , 2.5 mol / l or more is preferable. However, if the lithium salt concentration in the non-aqueous electrolyte is too high, the viscosity increases and the ionic conductivity decreases, so the lithium salt concentration in the non-aqueous electrolyte is 7 mol / l or less and 6 mol / l or less. It is preferable that

  Depending on the type of organic solvent used in the non-aqueous electrolyte, the solubility of the specific lithium salt is low, and it may not be possible to ensure the above concentration by using only one type of lithium salt. For this, a plurality of lithium salts may be used in combination so that the total lithium salt concentration satisfies the above value.

  The nonaqueous electrolyte preferably contains vinylene carbonate. Vinylene carbonate has a function of forming a film on the surface of the negative electrode by charging / discharging the non-aqueous secondary battery. And since the reaction derived from the contact between the negative electrode and the nonaqueous electrolyte can be suppressed by the coating derived from vinylene carbonate formed on the negative electrode surface, the deterioration of the negative electrode due to the nitrile solvent can be suppressed more favorably. That is, vinylene carbonate has not only a function as a nonaqueous electrolyte organic solvent but also a function as an additive for suppressing deterioration of the negative electrode. When a carbon material is used as the negative electrode active material (described later), the effect of suppressing the reaction between the negative electrode and the nonaqueous electrolyte component by vinylene carbonate becomes more remarkable. As described above, vinylene carbonate is preferably used in combination with other cyclic carbonates or chain carbonates because a relatively large amount of the vinylene carbonate is consumed by being involved in film formation by charging and discharging the battery as described above. .

  The vinylene carbonate content in the non-aqueous electrolyte may be used within the range of the amount described above as the preferred content of the carbonate in the total organic solvent, but the vinylene carbonate is coated with the charge / discharge of the battery. Since it also has the function of an additive to be formed, it is also preferable to adjust the amount in the total amount of the nonaqueous electrolyte. Specifically, from the viewpoint of ensuring the above-mentioned effects by use better, the content of vinylene carbonate in the non-aqueous electrolyte used for the non-aqueous secondary battery is preferably 2% by mass or more, and 4% by mass. % Or more is more preferable. However, if the amount of vinylene carbonate in the non-aqueous electrolyte is too large, the amount of gas generated in the battery increases, and the storage characteristics of the battery may deteriorate. Therefore, the content of vinylene carbonate in the non-aqueous electrolyte used for the non-aqueous secondary battery is preferably 15% by mass or less, and more preferably 10% by mass or less.

  In addition, the non-aqueous electrolyte includes 1,3-propane sultone, diphenyl disulfide, biphenyl, fluorobenzene, t-butylbenzene, for the purpose of improving battery safety, charge / discharge cycleability, and high-temperature storage properties. Additives such as halogen-substituted cyclic carbonates (such as 4-fluoro-1,3-dioxolan-2-one), sulfolane, fluoroethylene carbonate, and ethylene sulfite can be appropriately added.

  Furthermore, the nonaqueous secondary battery of the present invention is obtained by adding a gelling agent such as a known polymer to the liquid nonaqueous electrolyte (nonaqueous electrolyte) to form a gel (gel electrolyte). It may be used.

  The positive electrode according to the non-aqueous secondary battery of the present invention has a structure having a positive electrode active material layer containing a positive electrode active material, a conductive additive, a binder, etc. on one side or both sides of a positive electrode current collector. .

Examples of the positive electrode active material contained in the positive electrode active material layer include lithium cobalt oxides such as LiCoO ₂ ; lithium manganese oxides such as LiMnO ₂ and Li ₂ MnO ₃ ; lithium nickel oxides such as LiNiO ₂ ; LiMn ₂ O ₄ , Li _4/3 Ti _5/3 O ₄ and other spinel-structured lithium-containing composite oxides; LiFePO ₄ and other olivine-structured lithium-containing composite compounds; compounds obtained by substituting the above compounds with various elements; 1 type of these may be used, and 2 or more types may be used in combination.

  Examples of the conductive auxiliary agent related to the positive electrode active material layer include graphites such as natural graphite (eg, scaly graphite) and artificial graphite; acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and the like. It is preferable to use carbon materials such as carbon blacks; carbon fibers; and conductive fibers such as metal fibers; carbon fluorides; metal powders such as aluminum; zinc oxide; Conductive whiskers; conductive metal oxides such as titanium oxide; organic conductive materials such as polyphenylene derivatives; and the like can also be used.

  Examples of the binder relating to the positive electrode active material layer include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), and polyvinylpyrrolidone (PVP).

  For example, a positive electrode active material, a conductive additive, and a binder are dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) or water to form a paste-like or slurry-like positive electrode mixture-containing composition (positive electrode). (A composition for forming an active material layer) is prepared (however, the binder may be dissolved in a solvent), applied to one or both sides of the current collector, dried, and then calendered as necessary. It can manufacture by forming a positive electrode active material layer through the process of giving. However, the positive electrode is not limited to those manufactured by the above method, and may be manufactured by other methods.

  As the positive electrode current collector, an aluminum foil, a punching metal, a net, an expanded metal, or the like can be used, but an aluminum foil is usually used. A current collector provided with a conductive layer such as a carbon layer on the surface can also be preferably used. The thickness of the positive electrode current collector is preferably 10 to 30 μm.

  Moreover, you may form the lead body for electrically connecting with the other member in a non-aqueous secondary battery according to a conventional method as needed.

  As a composition of a positive electrode active material layer, it is preferable that content of a positive electrode active material is 80.0-99.8 mass%, and content of a conductive support agent is 0.1-10 mass%, for example. It is preferable that the binder content is 0.1 to 10% by mass.

  The thickness of the positive electrode active material layer (when the positive electrode active material layer is provided on both sides of the current collector, the thickness per side of the current collector. The same applies to the thickness of the positive electrode active material layer). From the viewpoint of increasing the capacity, it is preferably 70 μm or more, and more preferably 100 μm or more. However, if the positive electrode active material layer is too thick, the diffusion resistance of lithium ions increases and the internal resistance of the battery may increase. Therefore, the thickness of the positive electrode active material layer is preferably 1 mm or less, and more preferably 500 μm or less.

  As described above, when the positive electrode active material layer is thick as described above, it is usually difficult to sufficiently draw out the capacity of the positive electrode during discharge under a high load. However, in the non-aqueous secondary battery of the present invention, excellent load characteristics are ensured by the action of the nitrile solvent used in the non-aqueous electrolyte even when the positive electrode having the thick positive electrode active material layer as described above is used. be able to.

  The negative electrode includes a negative electrode active material layer containing a negative electrode active material (including a negative electrode active material, a binder, and a negative electrode mixture layer containing a conductive auxiliary agent used as necessary. The same applies hereinafter). A structure having a current collector on one side or both sides is used.

Examples of the negative electrode active material include graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads, carbon fibers, activated carbon, and metals that can be alloyed with lithium (Si Sn or the like) or an alloy thereof, an oxide (such as lithium titanate such as Li ₄ Ti ₅ O ₁₂ ), or the like, and one or more of these can be used. Moreover, metallic lithium and lithium alloys (lithium-aluminum alloy etc.) can also be used for a negative electrode active material.

  As the negative electrode binder and the conductive additive, the same materials as those exemplified above as those that can be used for the positive electrode can be used.

  The negative electrode is, for example, a paste-like or slurry-like negative electrode mixture-containing composition (negative electrode active material) in which a negative electrode active material, a binder, and a conductive auxiliary agent used as necessary are dispersed in a solvent such as NMP or water. (The composition for forming the material layer) is prepared (however, the binder may be dissolved in a solvent), applied to one or both sides of the current collector, dried, and then calendered as necessary. It manufactures by forming an active material layer through the process to give. Moreover, when using metal lithium or a lithium alloy as a negative electrode active material, a negative electrode can also be manufactured by sticking these foils on one or both sides of a current collector to form a negative electrode active material layer. However, the negative electrode is not limited to those manufactured by the above methods, and may be manufactured by other methods.

  As the current collector for the negative electrode, a foil made of copper or nickel, a punching metal, a net, an expanded metal, or the like can be used, but a copper foil is usually used. In the negative electrode current collector, when the thickness of the entire negative electrode is reduced in order to obtain a battery having a high energy density, the upper limit of the thickness is preferably 30 μm, and the lower limit is 5 μm in order to ensure mechanical strength. Is desirable.

  Moreover, you may form in the negative electrode the lead body for electrically connecting with the other member in a non-aqueous secondary battery according to a conventional method as needed.

  The thickness of the negative electrode active material layer (in the case of a negative electrode having a current collector, the thickness per side of the current collector) is preferably 10 to 100 μm. Moreover, when a negative electrode has a negative mix layer, as the composition, it is preferable that a negative electrode active material shall be 80.0-99.8 mass% and a binder shall be 0.1-10 mass%, for example. Furthermore, when making a negative mix layer contain a conductive support agent, it is preferable that the quantity of the conductive support agent in a negative mix layer shall be 0.1-10 mass%.

  The separator according to the non-aqueous secondary battery of the present invention has a property that the pores are blocked (that is, a shutdown function) at 80 ° C. or higher (more preferably 100 ° C. or higher) and 170 ° C. or lower (more preferably 150 ° C. or lower). It is preferable that a separator used in a normal non-aqueous secondary battery, for example, a microporous film made of polyolefin such as polyethylene (PE) or polypropylene (PP) can be used. The microporous film constituting the separator may be, for example, one using only PE or one using PP, or a laminate of a PE microporous film and a PP microporous film. There may be.

  The separator according to the non-aqueous secondary battery of the present invention may have a heat-resistant layer mainly composed of a heat-resistant resin or inorganic fine particles formed on the surface of the polyolefin microporous film. The heat-resistant layer has an effect of suppressing occurrence of a short circuit due to lithium dendrite and suppressing heat shrinkage of the microporous film.

  The inorganic fine particles have an electrical insulating property, are electrochemically stable, and further have a non-aqueous electrolyte (non-aqueous electrolyte solution) for the battery and a solvent used for the composition for forming the heat-resistant layer. The material is not particularly limited as long as it is a material that is stable and stable, that is, a material that hardly undergoes a chemical change in the battery and is difficult to deform.

Specific examples of the inorganic fine particles include, for example, oxide fine particles such as iron oxide, SiO ₂ , Al ₂ O ₃ , TiO ₂ , BaTiO ₃ , and ZrO ₂ ; nitride fine particles such as aluminum nitride and silicon nitride; calcium fluoride Slightly soluble ionic crystal fine particles such as barium fluoride and barium sulfate; Covalent crystal fine particles such as silicon and diamond; Clay fine particles such as talc and montmorillonite; Boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, seri Examples include inorganic fine particles such as sites derived from mineral resources such as sites, bentonite, hydrotalcite, or artificial products thereof. Further, the surface of conductive fine particles such as metal fine particles; oxide fine particles such as SnO ₂ and tin-indium oxide (ITO); carbon fine particles such as carbon black and graphite; It may be fine particles that have been made electrically insulating by surface treatment with the above-mentioned materials constituting the electrically insulating fine particles.

  Specific examples of the heat resistant resin include polyimide, melamine resin, phenol resin, crosslinked polymethyl methacrylate (crosslinked PMMA), crosslinked polystyrene (crosslinked PS), polydivinylbenzene (PDVB), benzoguanamine-formaldehyde condensate, and the like. Fine particles of crosslinked polymer; heat-resistant resin such as thermoplastic polyimide. These organic resins (polymers) are a mixture of the above exemplified materials, a modified body, a derivative, a copolymer (random copolymer, alternating copolymer, block copolymer, graft copolymer), crosslinked body ( In the case of the above heat-resistant polymer). The form of the heat-resistant resin and inorganic fine particles may be any form such as a spherical shape, a particle shape, or a plate shape.

  The heat-resistant resin and the inorganic fine particles are bound by a resin binder usually used for manufacturing a positive electrode or a negative electrode, thereby forming the porous heat-resistant layer.

  In addition, it is preferable that the thickness of a separator is 10-30 micrometers, for example.

  In the nonaqueous secondary battery of the present invention, the positive electrode and the negative electrode are stacked with the separator interposed therebetween, whereby a laminated body (laminated electrode body) configured such that the positive electrode and the negative electrode face each other, The laminated body is further used in the form of an electrode body such as a wound body (wound electrode body) in which the laminated body is wound in a spiral shape.

  In the electrode body, for each of the negative electrode active material layer and the positive electrode active material layer, the area of the non-facing portion not facing the active material layer of the other electrode is 15% or less of the area of the facing portions facing each other. . As a result, the amount of irreversible capacity among lithium ions occluded in the negative electrode active material layer can be reduced as much as possible during the initial charge of the non-aqueous secondary battery. The initial charge / discharge efficiency can be increased.

  For each of the negative electrode active material layer and the positive electrode active material layer, the area of the non-facing portion that does not face the active material layer of the other electrode is 15% or less of the area of the facing portion that faces each other. For each of the active layer and the positive electrode active material layer, arrange each active material layer so that portions not facing each other do not occur, or a part of the active material layer of one electrode faces the active material layer of the other electrode In the case of having a non-opposing portion that does not, the ratio of the area of the non-opposing portion is 15/115 or less of the total area of the active material layer of the electrode, that is, 13% or less. What is necessary is just to decide the dimension and arrangement | positioning of a layer.

  In addition, since the initial charge / discharge efficiency of the non-aqueous secondary battery can be increased as the ratio of the area of the non-opposing part to the area of the opposing part is small, the ratio is preferably 12% or less. 8% or less, more preferably 5% or less. In addition, since the first charge / discharge efficiency tends to be higher when the width of the non-facing portion is narrower, the dimensions and arrangement of the active material layers are set so that the width of the non-facing portion is 2 mm or less, preferably 1 mm or less. It is desirable to decide.

  In the normal battery configuration, the entire surface of the positive electrode active material layer is opposed to the negative electrode active material layer, and the area ratio of the non-opposing portion of the negative electrode active material layer is 15% or less of the area of the opposed portion. Each active material layer may be disposed. In this case, in order to prevent lithium precipitation at the end of the active material layer, it is desirable to dispose the positive electrode active material layer and the negative electrode active material layer so that the entire peripheral edge of the negative electrode active material layer is a non-opposing portion, Further, the width of the non-facing portion is preferably 0.1 mm or more, and more preferably 0.3 mm or more.

  On the other hand, when the negative electrode active material is lithium titanate or the like, the entire surface of the negative electrode active material layer is opposed to the positive electrode active material layer, and no non-opposing portion is provided in each active material layer (the negative electrode active material layer The entire surface and the entire surface of the positive electrode active material layer may be opposed to each other), or a non-opposing portion may be provided in a part of the positive electrode active material layer. Also in this case, each active material layer may be arranged so that the ratio of the area of the non-opposing portion is 15% or less of the area of the opposing portion.

  1 and 2 are drawings for explaining “width of a non-facing portion of the active material layer” in a configuration in which the entire surface of the positive electrode active material layer faces the negative electrode active material layer. FIG. 1 is an explanatory diagram in the case where an electrode body composed of a positive electrode, a negative electrode, and a separator is a laminated electrode body (an electrode body formed only by overlapping them), and (a) shows a circular positive electrode active in a plan view. The case where the positive electrode which has the material layer 50 and the negative electrode which has the circular negative electrode active material layer 60 by planar view is facing is shown, (b) is a positive electrode which has the square positive electrode active material layer 50 by planar view. And a negative electrode having a square negative electrode active material layer 60 in a plan view is opposed to each other. Moreover, FIG. 2 is explanatory drawing in the case where the electrode body comprised by a positive electrode, a negative electrode, and a separator is a wound electrode body formed by winding these laminated bodies in a spiral shape. In these drawings, in order to facilitate understanding of the positional relationship between the positive electrode active material layer 50 and the negative electrode active material layer 60, the current collector and separator of the positive electrode and the negative electrode are not shown. In FIG. 2, a part of a portion where the positive electrode active material layer 50 and the negative electrode active material layer 60 are opposed to each other in the wound electrode body is shown in a plan view.

  In FIG. 1, the front side in the drawing is the negative electrode active material layer 60, and the one indicated by the dotted line on the depth side is the positive electrode active material layer 50. The “width of the non-opposing portion of the negative electrode active material layer” in the laminated electrode body is the distance between the outer peripheral edge of the negative electrode active material layer 60 and the outer peripheral edge of the positive electrode active material layer 50 in plan view (a in FIG. Length).

  Also in FIG. 2, as in FIG. 1, the front side in the drawing is the negative electrode active material layer 60, and the depth side dotted line is the positive electrode active material layer 50. For the formation of the wound electrode body, a strip-shaped positive electrode and a strip-shaped negative electrode are used, and the “width of the non-opposing portion of the negative electrode active material layer” is in the longitudinal direction of the strip-shaped positive electrode and the strip-shaped negative electrode. It means the distance (the length of b in the figure) between the outer end of the negative electrode active material layer 60 and the outer end of the positive electrode active material layer 50 in the orthogonal direction.

  In the case of a configuration in which the entire surface of the negative electrode active material layer faces the positive electrode active material layer (a configuration in which a part of the positive electrode active material layer has a non-opposing portion), the positive electrode and the negative electrode may be interchanged. .

  Examples of the form of the non-aqueous secondary battery of the present invention include a cylindrical shape (such as a rectangular tube shape or a cylindrical shape) using a steel can or an aluminum can as an outer can. Moreover, it can also be set as the soft package battery which used the laminated film which vapor-deposited the metal as an exterior body.

  The non-aqueous secondary battery of the present invention can ensure excellent load characteristics even when the positive electrode active material layer is thick, and can satisfactorily suppress capacity reduction during high output discharge. The same use as the various uses to which the conventionally known non-aqueous secondary battery is applied, including the use of high capacity and high output discharge like the storage battery use of photovoltaic power generation system Can be used.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

Example 1
<Preparation of positive electrode>
LiNi _0.5 Co _0.2 Mn _0.3 O _{2 as} positive electrode active material: 93.7 parts by mass, acetylene black as conductive aid: 4.0 parts by mass, PVDF as binder: 2.0 Mix part by mass and polyvinyl pyrrolidone (PVP) as a dispersant: 0.3 part by mass, add an appropriate amount of NMP, and mix and disperse using a planetary mixer to produce a positive electrode mixture-containing slurry. Prepared.

Next, after applying the positive electrode mixture-containing slurry to one surface of an aluminum foil having a thickness of 15 μm serving as a positive electrode current collector so that the applied amount after drying is 21 mg / cm ^2, and drying at 85 ° C. And vacuum drying at 100 ° C. for 8 hours. Then, the press process was performed using the roll press machine and the positive electrode provided with the positive electrode active material layer (positive electrode mixture layer) whose thickness after a press process is 90 micrometers was produced. In addition, when apply | coating the positive mix containing slurry to aluminum foil, the uncoated part was formed so that a part of aluminum foil might be exposed.

  Next, the positive electrode is cut so that the positive electrode active material layer has an area of 30 mm × 30 mm and includes an exposed portion of the aluminum foil, and an aluminum lead piece for taking out an electric current is further exposed to the exposed portion of the aluminum foil. To obtain a positive electrode with leads.

<Production of negative electrode>
Graphite as the negative electrode active material: 96 parts by mass, and CMC as the binder: 2 parts by mass and SBR: 2 parts by mass Add an appropriate amount of water, and mix and disperse using a planetary mixer The negative electrode mixture-containing slurry was prepared. Next, the negative electrode mixture-containing slurry is applied to one surface of a copper foil having a thickness of 7 μm serving as a negative electrode current collector so that the applied amount after drying is 13.5 mg / cm ² and dried at 85 ° C. And then vacuum-dried at 100 ° C. for 8 hours. Then, the negative electrode provided with the negative electrode active material layer (negative electrode mixture layer) with a thickness of 102 micrometers by performing press processing using the roll press machine was produced. In addition, when apply | coating negative mix containing slurry to copper foil, the uncoated part was formed so that a part of copper foil might be exposed.

  Next, the negative electrode was cut so that the area of the negative electrode active material layer was 30.5 mm × 30.5 mm and the exposed portion of the copper foil was included, and further, a nickel lead piece for taking out current was obtained. It welded to the exposed part of copper foil, and the negative electrode with a lead was obtained.

<Preparation of non-aqueous electrolyte>
In a solvent in which ethylene carbonate, acetonitrile, and vinylene carbonate are mixed at a mass ratio of 33:56:11, LiPF ₆ is adjusted to a concentration of 0.3 mol / l, and LiN (CF ₃ SO ₂ ) ₂ is added to 2. A non-aqueous electrolyte was prepared by dissolving each so as to have a concentration of 5 mol / l. The concentration of vinylene carbonate in the total amount of the nonaqueous electrolytic solution was 6% by mass (the same applies to all examples and comparative examples described later).

<Battery assembly>
The positive electrode with lead and the negative electrode with lead are overlapped via a PE microporous membrane separator (thickness 18 μm) to form a laminated electrode body, and this laminated electrode body is made of an aluminum laminate film of 90 mm × 80 mm. Housed in the body. Subsequently, after injecting 1 mL of the non-aqueous electrolyte into the exterior body, the exterior body is sealed, and a laminate type non-aqueous secondary battery having a cross-sectional structure shown in FIG. did.

  Here, FIG. 3 and FIG. 4 will be described. FIG. 3 is a plan view schematically showing a non-aqueous secondary battery, and FIG. 4 is a cross-sectional view taken along line AA of FIG. The nonaqueous secondary battery 1 includes a laminated electrode body formed by laminating a positive electrode 5 and a negative electrode 6 via a separator 7 in a laminated film outer package 2 constituted by two laminated films, and a nonaqueous electrolytic solution. (Not shown) is accommodated, and the laminate film outer package 2 is sealed by heat-sealing the upper and lower laminate films at the outer peripheral portion thereof. In FIG. 4, each layer constituting the laminate film outer package 2 and each layer of the positive electrode 5 and the negative electrode 6 are not shown separately in order to avoid the drawing from becoming complicated.

  The positive electrode 5 is connected to the positive electrode external terminal 3 in the battery 1 through a lead body. Although not shown, the negative electrode 6 is also connected to the negative electrode external terminal 4 in the battery 1 through a lead body. doing. The positive electrode external terminal 3 and the negative electrode external terminal 4 are drawn out to the outside of the laminate film exterior body 2 so that they can be connected to an external device or the like.

Examples 2-9
Except that the type and concentration of the lithium salt and the type and composition of the organic solvent are as shown in Table 1, non-aqueous electrolytes were prepared in the same manner as in Example 1, and these non-aqueous electrolytes were used. Produced a laminated nonaqueous secondary battery in the same manner as in Example 1.

Example 10
A negative electrode (a negative electrode with leads) was prepared in the same manner as in Example 1 except that the area of the negative electrode active material layer was changed to 31 mm × 31 mm, and a laminated non-aqueous solution was obtained in the same manner as in Example 1 except that this negative electrode was used. A secondary battery was produced.

Examples 11-18
Except that the type and concentration of the lithium salt and the type and composition of the organic solvent are as shown in Table 2, non-aqueous electrolytes were prepared in the same manner as in Example 1, and these non-aqueous electrolytes were used. Produced a laminated nonaqueous secondary battery in the same manner as in Example 10.

Example 19
Negative electrode mixture composed of lithium titanate (Li ₄ Ti ₅ O ₁₂ ) powder as negative electrode active material: 85 parts by mass, acetylene black as conductive aid: 9 parts by mass, and PVDF as binder: 6 parts by mass An appropriate amount of NMP was added to the mixture, and these were mixed to prepare a negative electrode mixture-containing slurry. Next, a negative electrode having a negative electrode active material layer (negative electrode mixture layer) thickness of 150 μm was prepared in the same manner as in Example 1 except that this slurry was used. And using this negative electrode, the negative electrode with a lead whose area of a negative electrode active material layer is 29.5 mm x 29.5 mm was produced like Example 1. FIG.

  A laminated nonaqueous secondary battery was produced in the same manner as in Example 1 except that the negative electrode (negative electrode with leads) was used.

Example 20
A negative electrode (negative electrode with leads) was prepared in the same manner as in Example 19 except that the area of the negative electrode active material layer was changed to 29 mm × 29 mm, and a laminated non-aqueous solution was obtained in the same manner as in Example 1 except that this negative electrode was used. A secondary battery was produced.

Comparative Examples 1-4
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that the type and concentration of the lithium salt and the type and composition of the organic solvent were as shown in Table 3. Moreover, the negative electrode (negative electrode with a lead) was produced like Example 1 except having changed the area of the negative electrode active material layer into 32.5 mm x 32.5 mm.

  A laminated nonaqueous secondary battery was produced in the same manner as in Example 1 except that the nonaqueous electrolyte and the negative electrode were used.

Comparative Example 5
A negative electrode (a negative electrode with leads) was prepared in the same manner as in Example 19 except that the area of the negative electrode active material layer was changed to 27.5 mm × 27.5 mm, and the same procedure as in Example 1 was performed except that this negative electrode was used. A laminated nonaqueous secondary battery was produced.

  The structure of the non-aqueous electrolyte used for the non-aqueous secondary battery of an Example and a comparative example is shown in Tables 1-3, and the positive electrode active material layer which concerns on the positive electrode used for these non-aqueous secondary batteries, and the negative electrode which concerns on a negative electrode The ratio of the area of the non-facing portion to the area of the portion facing the active material layer (in the table, “the ratio of the non-facing area to the facing area of the positive electrode active material layer and the negative electrode active material layer”), negative electrode active material Tables 4 to 6 show the width of the non-facing portion of the layer and the width of the non-facing portion of the positive electrode active material layer. In Tables 1 to 3, EC means ethylene carbonate, PC means propylene carbonate, DMC means dimethyl carbonate, AN means acetonitrile, PN means propionitrile, and VC means vinylene carbonate. .

  Moreover, the following first-time charge / discharge efficiency measurement and load characteristic evaluation were performed about the non-aqueous secondary battery of the Example and the comparative example. These results are shown in Tables 7-9.

<Initial charge / discharge efficiency measurement>
About each non-aqueous secondary battery of an Example and a comparative example, after performing a constant current charge to 4.2V with the electric current value of 0.2C at 23 degreeC, it is 4.2V until an electric current value will be set to 0.1 CmA. The battery was charged at a constant voltage, and the charge capacity (0.2 C charge capacity) was measured. Then, about each battery after charge, it discharged with the constant current until it became 2.5V with the electric current value of 0.2C, and 0.2C discharge capacity was measured. And about each battery, the value which remove | divided 0.2C discharge capacity by 0.2C charge capacity was represented by the percentage, and the first time charge / discharge efficiency was calculated | required.

<Evaluation of load characteristics>
About each non-aqueous secondary battery of an Example and a comparative example, except having changed the electric current value at the time of constant current charge and constant current charge into 3C, it is constant current-constant voltage on the same conditions as 0.2C charge / discharge capacity measurement Charging and constant current discharging were performed, and 3C charging capacity was measured.

  As shown in Tables 1 to 9, the non-aqueous secondary batteries of Examples 1 to 20 using the non-aqueous electrolyte solution having an appropriate composition and appropriately arranging the negative electrode active material layer and the positive electrode active material layer are as follows. The initial charge / discharge efficiency is high, the discharge capacity is large even at a high load of 3C, and the load characteristics are good.

  As is clear from the comparison between Example 1 and Comparative Example 4 and the comparison between Example 19 and Example 20 and Comparative Example 5, the non-opposing area with respect to the opposing area of the positive electrode active material layer and the negative electrode active material layer When the ratio exceeds 15%, the initial charge / discharge efficiency is lowered and the discharge capacity is lowered.

  As is clear from the comparison between Comparative Example 1 and Comparative Example 2, when the ratio of the non-facing area to the facing area of the positive electrode active material layer and the negative electrode active material layer exceeds 15%, a nitrile solvent is used. The battery (Comparative Example 1) having an organic solvent structure including the nitrile-based battery has a lower initial charge / discharge efficiency than the battery having a general-purpose organic solvent structure not containing a nitrile solvent (Comparative Example 2). It can be seen that it is more important to adjust the ratio of the non-facing area to the facing area between the positive electrode active material layer and the negative electrode active material layer in a battery having an organic solvent structure including a solvent.

  Further, as is clear from the comparison between Comparative Example 4 and Comparative Examples 1 and 3, when the lithium salt concentration is less than 2 mol / l, the initial charge / discharge efficiency is lowered, and in particular, carbonate as an organic solvent. In Comparative Example 1 that does not contain, it is greatly reduced.

DESCRIPTION OF SYMBOLS 1 Nonaqueous secondary battery 2 Laminate film exterior body 5 Positive electrode 6 Negative electrode 7 Separator 50 Positive electrode active material layer 60 Negative electrode active material layer

Claims (11)

Nonaqueous using positive electrode having positive electrode active material layer on one or both sides of current collector, negative electrode having negative electrode active material layer on one or both sides of current collector, and nonaqueous electrolyte containing lithium salt and organic solvent A secondary battery,
As the negative electrode active material, graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads, carbon fibers, activated carbon, metals that can be alloyed with lithium, or alloys thereof , Containing at least one selected from metallic lithium and lithium alloys,
The non-aqueous electrolyte has a lithium salt concentration of 2 to 7 mol / l,
The non-aqueous electrolyte contains, as the organic solvent, a nitrile solvent and at least one carbonate selected from cyclic carbonate and chain carbonate,
The entire surface of the positive electrode active material layer faces the negative electrode active material layer;
The negative active with the material layer, the area of the non-opposing portions that do not face the positive electrode active material layer, a non-aqueous secondary battery, wherein more than 15% of the area of the facing portions facing each other.   The non-aqueous secondary battery according to claim 1, wherein a width of the non-facing portion is 2 mm or less.   The non-aqueous secondary battery according to claim 1, wherein a width of the non-facing portion is 0.1 mm or more. The non-aqueous secondary battery according to any one of claims 1 to 3 , wherein a content of the nitrile solvent in the total organic solvent of the non-aqueous electrolyte is 5 to 80% by mass. The non-aqueous electrolyte, as the nitrile solvent, a non-aqueous secondary battery according to any one of claims 1 to 4 containing mononitriles. The nonaqueous secondary battery according to claim 5 , wherein the nonaqueous electrolyte contains acetonitrile, propionitrile, butyronitrile, valeronitrile, benzonitrile, or acrylonitrile as a mononitrile. The nonaqueous secondary battery according to any one of claims 1 to 6 , wherein the nonaqueous electrolyte contains ethylene carbonate or propylene carbonate as the cyclic carbonate. The non-aqueous electrolyte, as the chain carbonate, dimethyl carbonate, a non-aqueous secondary battery according to any one of claims 1 to 7 containing diethyl carbonate or ethyl methyl carbonate. The non-aqueous electrolyte, a non-aqueous secondary battery according to any one of claims 1-8 containing vinylene carbonate as the cyclic carbonate. The thickness of the positive electrode active material layer per one surface of the current collector, a non-aqueous secondary battery according to any one of claims 1 to 9 is 70μm to 1mm. The nonaqueous secondary battery according to any one of claims 1 to 10 , having a structure in which the positive electrode and the negative electrode are wound.

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