JP2012243478A - Nonaqueous electrolyte secondary battery and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery in which an addition effect of an electrolyte additive can be more adequately exerted.SOLUTION: A nonaqueous electrolyte secondary battery 100 includes: a positive electrode 30 including a positive electrode active material; a negative electrode 40 including a negative electrode active material; and a nonaqueous electrolyte 90 arranged in contact with both of the active materials. A nonaqueous electrolyte including an oxalate complex compound, which contains at least one of B element and P element, and a nonaqueous solvent is used as the nonaqueous electrolyte 90. The DBP absorption value X (mL) of the total positive electrode active material included in the battery 100 and the DBP absorption value Y (mL) of the total negative electrode active material included in the battery 100 have a relationship satisfying the expression: 0.60≤X/Y≤1.25.

Description

  The present invention relates to a secondary battery (non-aqueous electrolyte secondary battery) provided with a non-aqueous electrolyte.

  Lithium ion secondary batteries and other non-aqueous electrolyte secondary batteries are becoming increasingly important as on-vehicle power supplies or personal computers and portable terminals. In particular, a lithium ion secondary battery that is lightweight and obtains a high energy density is expected to be preferably used as a high-output power source mounted on a vehicle. In order to further improve the performance of the non-aqueous electrolyte secondary battery, it has been proposed to add various additives to the non-aqueous electrolyte. For example, Patent Documents 1 to 3 describe an electrolyte solution for a lithium ion secondary battery containing an oxalatoborate type compound (for example, lithium bis (oxalato) borate).

Japanese Patent No. 3730856 JP 2010-192430 A JP 2010-0334050 A

  However, according to the study of the present inventor, the use of an oxalatoborate type compound in a non-aqueous electrolyte secondary battery can be useful for battery durability (such as suppression of resistance increase due to repeated storage and charge / discharge). On the other hand, other battery performance may be reduced. This invention is made | formed in view of this situation, Comprising: It aims at provision of the nonaqueous electrolyte secondary battery with which the effect of electrolyte solution additive can be exhibited more appropriately. Another related object is to provide a method for manufacturing such a non-aqueous electrolyte secondary battery.

  The present inventor has found that if the additive contained in the non-aqueous electrolyte is distributed (arranged) more in locations where it can exert an advantageous effect on the battery performance, the advantageous effect is less likely to be exhibited or disadvantageous. We thought that the amount of distribution to places where effects could be produced would be relatively reduced, and that the above problems could be solved. Therefore, the present inventor paid attention to the DBP (dibutyl phthalate) absorption amount of the positive electrode active material and the negative electrode active material as an index for grasping the distribution ratio of the additive in the non-aqueous electrolyte to the positive electrode and the negative electrode. And, by adjusting the ratio of the DBP absorption amount of the total positive electrode active material possessed by the positive electrode and the DBP absorption amount of the total negative electrode active material possessed by the negative electrode, the function of the electrolyte additive can be exhibited more appropriately and the high performance. The present invention was completed by finding that a non-aqueous electrolyte secondary battery can be obtained.

  The non-aqueous electrolyte secondary battery disclosed herein includes a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and non-aqueous electrolysis arranged in contact with both the positive electrode active material and the negative electrode active material. Liquid. The non-aqueous electrolyte includes a non-aqueous solvent and an oxalato complex compound (hereinafter also referred to as “BP-oxalato compound”) containing at least one of element B (boron) and element P (phosphorus). A water electrolyte is used. About the DBP absorption amount (hereinafter also referred to as “total positive electrode active material DBP absorption amount”) X (mL) with respect to the total amount of the positive electrode active material contained in the battery, and the total amount of the negative electrode active material contained in the battery The DBP absorption amount (hereinafter also referred to as “total negative electrode active material DBP absorption amount”) Y (mL) satisfies the following formula: 0.60 ≦ X / Y ≦ 1.25.

  According to the knowledge of the present inventors, the BP-oxalato compound added to the electrolytic solution is adsorbed on the positive electrode (for example, oxidatively decomposes on the positive electrode surface to form a film), thereby removing the positive electrode active material from the electrolytic solution. While protecting, the effect of improving the durability of the battery (for example, suppressing an increase in resistance due to repeated storage and charge / discharge) can be exhibited. On the other hand, the BP-oxalato compound adsorbed on the negative electrode can be a factor of reducing the initial characteristics (for example, initial efficiency, initial resistance, etc.) of the battery. In addition, in a conventional non-aqueous electrolyte secondary battery having a general configuration, the additive added to the electrolyte is distributed more than three times more on the negative electrode side than on the positive electrode side (in other words, on the positive electrode side). In general, it is said that only about 0.33 times or less of the negative electrode side is distributed to the negative electrode side). Typically, it is said that 10 times or more of the negative electrode side is distributed compared to the positive electrode side.

  In the non-aqueous electrolyte secondary battery according to the present invention, the characteristics of the positive electrode and the negative electrode are adjusted so that more BP-oxalato compound added to the electrolyte is distributed to the positive electrode side than the conventional general battery. Has been. Specifically, the total positive electrode active material DBP absorption amount X is at least 0.60 times the total negative electrode active material DBP absorption amount Y. As a result, the BP-oxalato compound added to the electrolytic solution can be used more effectively, and adverse effects caused by the compound can be suppressed. As a result, a higher performance non-aqueous electrolyte secondary battery can be realized.

  In the present specification, the “secondary battery” refers to a general power storage device that can be repeatedly charged and discharged, and is a term including a so-called storage battery such as a lithium secondary battery and a power storage element such as an electric double layer capacitor. The “non-aqueous electrolyte secondary battery” refers to a battery provided with a non-aqueous electrolyte (typically, an electrolyte containing a supporting salt (supporting electrolyte) in a non-aqueous solvent). The “lithium secondary battery” refers to a secondary battery that uses lithium ions as electrolyte ions and is charged and discharged by the movement of lithium ions between the positive and negative electrodes. A secondary battery generally referred to as a lithium ion battery is a typical example included in the lithium secondary battery in this specification. The electrode active material refers to a material that can reversibly occlude and release chemical species (lithium ions in a lithium secondary battery) serving as a charge carrier.

  As a preferred example of the BP-oxalato compound in the technology disclosed herein, lithium bis (oxalato) borate represented by the following formula (I) can be given.

  The relationship between the total mole number A (mmol) of the BP-oxalato compound contained in the battery and the total positive electrode active material DBP absorption amount X (mL) is expressed by the following formula: 0.02 ≦ A / X (mmol / mL) ) ≦ 0.30; According to the battery of this aspect, the function of the oxalato compound is more appropriately exhibited, and higher performance can be realized. If A / X is too small, the amount of the oxalato compound supplied per actual reaction area of the positive electrode active material becomes too small, and the addition effect of the oxalato compound (for example, resistance increase due to repeated storage and charge / discharge) The suppression effect tends to be small. When A / X is too large, the amount of the oxalato compound allocated to the negative electrode becomes too large, and the initial characteristics of the battery may tend to be deteriorated due to the influence of the oxalato compound allocated to the negative electrode.

  The DBP absorption amount x (mL / 100 g) per 100 g of the positive electrode active material is preferably 25 mL / 100 g or more (typically 25 to 75 mL / 100 g). If the DBP absorption amount x is too small, the mass of the positive electrode active material relative to the mass of the negative electrode active material increases so that the energy density of the battery may easily decrease. In addition, in order to satisfy the above X / Y, a negative electrode active material having a DBP absorption amount y (mL / 100 g) per 100 g that is too small may be used, and the reaction resistance of the negative electrode may easily increase. .

  The DBP absorption amount y (mL / 100 g) per 100 g of the negative electrode active material is preferably 35 to 75 mL / 100 g. If the DBP absorption y is too small, the actual reaction area of the negative electrode may be reduced, and the output resistance of the battery may be easily increased. If y is too large, the amount of the negative electrode active material that can be used to satisfy the above X / Y becomes too small with respect to the positive electrode active material, and metal lithium tends to precipitate depending on the battery use conditions. Can occur.

  In a preferred embodiment, the relationship between the DBP absorption amount x (mL) per 100 g of the positive electrode active material and the DBP absorption amount y (mL) per 100 g of the negative electrode active material is expressed by the following formula: 0.55 ≦ x /Y≦1.15; If x / y is too large, the amount of the positive electrode active material necessary to satisfy the above X / Y becomes too large, and the energy density of the battery tends to decrease. When x / y is too small, the amount of the negative electrode active material that can be used to satisfy the above X / Y is too small with respect to the positive electrode active material, and depending on the use conditions of the battery, metallic lithium is likely to be deposited. Inconvenience can occur.

  Preferable examples of the positive electrode active material include lithium transition metal oxides. The technology disclosed herein can be preferably applied to, for example, a battery using a lithium transition metal oxide having a layered structure as a positive electrode active material (for example, a lithium transition metal oxide containing at least nickel as a constituent metal element). Preferable examples of the negative electrode active material include a carbon material having a graphite structure at least partially.

  According to this specification, a method for manufacturing a non-aqueous electrolyte secondary battery is also provided. The method includes providing a positive electrode having a positive electrode active material and a negative electrode having a negative electrode active material. The positive electrode and the negative electrode prepared here are DBP absorption amount X (mL) with respect to the total amount of the positive electrode active material of the positive electrode (typically coincides with the total positive electrode active material DBP absorption amount). The relationship with the DBP absorption amount Y (mL) of the total amount of the negative electrode active material of the negative electrode (typically coincides with the total negative electrode active material DBP absorption amount) is as follows: 0.60 ≦ X / Y ≦ 1.25 is satisfied. The method also includes providing a non-aqueous electrolyte solution (typically, a non-aqueous electrolyte solution further containing a supporting electrolyte) containing a non-aqueous solvent and a BP-oxalato compound. Also, the battery includes a positive electrode, the negative electrode, and the non-aqueous electrolyte contained in a container.

  In the battery manufactured by such a method, the characteristics of the positive electrode and the negative electrode satisfy the above X / Y (that is, more BP-oxalato compound added to the electrolytic solution is distributed to the positive electrode side than the conventional general battery. Thus, the characteristics of the positive electrode and the negative electrode are adjusted.) Therefore, the oxalate compound added to the electrolytic solution can be used more effectively, and a higher performance non-aqueous electrolyte battery in which the adverse effects of the oxalato compound are suppressed can be obtained.

  In a preferred embodiment of the method for producing a non-aqueous electrolyte secondary battery disclosed herein, the total number of moles A (mmol) of the BP-oxalato compound contained in the non-aqueous electrolyte contained in the container, The relationship with the substance DBP absorption amount X (mL) satisfies the following formula: 0.02 ≦ A / X (mmol / mL) ≦ 0.30. According to the battery of this aspect, the function of the oxalato compound is more appropriately exhibited, and higher performance can be realized. The value of A / X depends on, for example, the total positive electrode active material DBP absorption amount X, and the concentration of the oxalate compound in the electrolytic solution used for the construction of each battery and the amount of the electrolytic solution used (contained in the container) By adjusting one or both of them, it is possible to set so as to satisfy the above formula.

  Any of the non-aqueous electrolyte secondary batteries disclosed herein (which may be batteries manufactured by any of the methods disclosed herein) has high durability (for example, increased resistance during storage). For example, it is suitable as a power source mounted on a vehicle. Therefore, the battery disclosed here (typically a lithium ion secondary battery) is a power source (typically driving) for a motor mounted on a vehicle such as a hybrid vehicle or an automobile equipped with an electric motor such as an electric vehicle. It can be suitably used as a power source.

It is a perspective view which shows the external shape of the nonaqueous electrolyte secondary battery which concerns on one Embodiment. It is the II-II sectional view taken on the line of FIG. It is a cross-sectional SEM image of the void | hole hollow active material particle which concerns on one Embodiment. It is a side view which shows typically the vehicle (automobile) provided with the nonaqueous electrolyte secondary battery which concerns on one Embodiment.

  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.

  The technology disclosed herein is referred to as various non-aqueous electrolyte secondary batteries (hereinafter referred to as “non-aqueous secondary batteries”) using a non-aqueous electrolyte containing a BP-oxalato compound at the time of battery construction. May be widely applied). Hereinafter, although the present invention will be described in more detail mainly using the case where the non-aqueous secondary battery is a lithium ion secondary battery as an example, the application target of the present invention is not intended to be limited to such a battery.

≪Example of lithium ion secondary battery structure≫
In the lithium ion secondary battery according to an embodiment of the technology disclosed herein, for example, as illustrated in FIGS. 1 and 2, the wound electrode body 20 includes the non-aqueous electrolyte 90 and the electrode body 20. It has the structure accommodated in the flat box-shaped battery case 10 corresponding to a shape. The opening 12 of the case 10 is closed with a lid 14. The lid body 14 is provided with a positive terminal 38 and a negative terminal 48 for external connection so that a part of the terminals protrudes outward from the lid body 14. The lithium ion secondary battery 100 having such a configuration is provided in the lid body 14 after the electrode body 20 is accommodated inside the opening portion 12 of the case 10 and the lid body 14 is attached to the opening portion 12 of the case 10. It can be constructed by injecting an electrolytic solution 90 from a prepared electrolytic solution injection hole (not shown) and then closing the injection hole.

  The electrode body 20 has a positive electrode sheet 30 in which a positive electrode mixture layer 34 containing a positive electrode active material is held by a long sheet-like positive electrode current collector 32 and a negative electrode mixture layer 44 containing a negative electrode active material in a long sheet form. The negative electrode sheet 40 held on the negative electrode current collector 42 is overlapped and wound, and the obtained wound body is pressed from the side surface direction and flared to form a flat shape. Typically, an insulating layer is disposed between the positive electrode mixture layer 34 and the negative electrode mixture layer 44 to prevent direct contact therebetween. In a preferred embodiment, two long sheet-like separators 50 are used as the insulating layer. For example, the electrode body 20 is configured by winding these separators 50 together with the positive electrode sheet 30 and the negative electrode sheet 40. The insulating layer may be coated on one or both surfaces of the positive electrode mixture layer 34 and the negative electrode mixture layer 44.

  The positive electrode sheet 30 is formed such that the positive electrode mixture layer 34 is not provided (or removed) at one end portion along the longitudinal direction, and the positive electrode current collector 32 is exposed. Similarly, the negative electrode sheet 40 is formed so that the negative electrode mixture layer 44 is not provided (or removed) at one end along the longitudinal direction, and the negative electrode current collector 42 is exposed. Yes. A positive electrode terminal 38 is joined to the exposed end portion of the positive electrode current collector 32, and a negative electrode terminal 48 is joined to the exposed end portion of the negative electrode current collector 42. The positive and negative electrode terminals 38 and 48 and the positive and negative electrode current collectors 32 and 42 can be joined by, for example, ultrasonic welding, resistance welding, or the like.

≪Positive electrode mixture layer≫
In a preferred embodiment, the positive electrode mixture layer 34 is a layer mainly composed of a positive electrode active material. The positive electrode mixture layer 34 may contain optional components such as a conductive material and a binder (binder) in addition to the positive electrode active material.

  As the positive electrode active material, a material capable of reversibly occluding and releasing lithium is used, and various materials known to be usable as a positive electrode active material of a lithium ion secondary battery (for example, oxidation of a layered structure) 1 type or 2 types or more of a thing and an oxide of a spinel structure) can be used without limitation. Preferable examples include oxides (lithium transition metal oxides) containing lithium and at least one transition metal element as constituent metal elements, such as lithium nickel oxide, lithium cobalt oxide, and lithium manganese oxide. For example, a lithium transition metal oxide having a layered structure can be preferably used.

Here, the lithium nickel oxide is an oxide containing only lithium (Li) and nickel (Ni) as a constituent metal element (for example, lithium nickelate represented by LiNiO ₂ ), in addition to Li and Ni. Also includes oxides containing at least one metal element (that is, transition metal elements other than Li and Ni and / or typical metal elements) as constituent metal elements at a rate equivalent to or less than Ni in terms of the number of atoms. That means Examples of the metal element other than Li and Ni include, for example, Co, Al, Mn, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce. It may be one or more metal elements selected from the group consisting of: The same meaning applies to lithium cobalt oxide and lithium manganese oxide. As a preferable positive electrode active material in the technique disclosed herein, a lithium transition metal oxide (typically, lithium nickel oxide having a layered structure) containing at least Ni as a constituent metal element is exemplified. For example, a lithium transition metal oxide containing at least Ni, Co, and Mn as constituent metal elements (for example, containing approximately the same amount of three elements of Ni, Co, and Mn in terms of the number of atoms) can be preferably used. Hereinafter, a lithium transition metal oxide containing Ni, Co and Mn as constituent metal elements may be referred to as “LiNiCoMn oxide”.

Other suitable examples of the material that can be used as the positive electrode active material include olivine type lithium phosphate and other polyanion materials. The lithium olivine is, for example, an olivine-type lithium phosphate (LiFePO ₄ , LiMnPO _4, etc.) represented by a general formula LiMPO ₄ (M is at least one element of Co, Ni, Mn, and Fe). obtain.

  Examples of the conductive material include carbon materials such as carbon powder and carbon fiber, and conductive metal powder such as nickel powder. As the carbon powder, various carbon blacks (for example, acetylene black, furnace black, ketjen black), graphite powder, and the like can be used. Among these, acetylene black (AB) is a preferable carbon powder. Such conductive materials can be used singly or in appropriate combination of two or more.

  Examples of the binder include carboxymethylcellulose (CMC; typically a sodium salt is used), polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), and polyvinylidene fluoride (PVDF). ) And the like. Such a binder can be used individually by 1 type or in combination of 2 or more types as appropriate.

  The proportion of the positive electrode active material in the entire positive electrode mixture layer is suitably about 50% by mass or more (typically 50 to 95% by mass), and usually about 70 to 95% by mass. preferable. When the conductive agent is used, the ratio of the conductive material in the entire positive electrode mixture layer can be, for example, about 2 to 20% by mass, and preferably about 2 to 15% by mass. When using a binder, the ratio of the binder to the whole positive electrode mixture layer can be, for example, about 1 to 10% by mass, and usually about 2 to 5% by mass is appropriate.

  As the positive electrode current collector 32, a conductive member made of a highly conductive metal is preferably used. For example, aluminum or an alloy containing aluminum as a main component can be used. The shape of the positive electrode current collector 32 may vary depending on the shape of the lithium ion secondary battery, and is not particularly limited, and may be various forms such as a rod shape, a plate shape, a sheet shape, a foil shape, and a mesh shape. . In the lithium ion secondary battery 100 including the wound electrode body 20 as in the present embodiment, a sheet-like aluminum positive electrode current collector 32 can be preferably used. In such an embodiment, for example, an aluminum sheet (aluminum foil) having a thickness of about 10 μm to 30 μm can be preferably used as the positive electrode current collector 32.

In the positive electrode sheet 30 having such a configuration, the positive electrode active material (typically in particulate form) and optional components used as necessary are contained in an appropriate solvent (for example, water, N-methyl-2-pyrrolidone (NMP), etc.). It can preferably be produced by applying a dispersed paste or slurry-like composition (composition for forming a positive electrode mixture layer) to the positive electrode current collector 32 and drying the composition. This drying can be performed under heating as necessary. After drying, the whole may be pressed as necessary. The mass of the positive electrode mixture layer 34 provided per unit area of the positive electrode current collector 32 (the total mass on both sides in the configuration having the positive electrode mixture layer 34 on both surfaces of the positive electrode current collector 32) is, for example, 8 to 30 mg / cm. It is appropriate to set it to about ² . The density of the positive electrode mixture layer 34 can be set to, for example, about 1.9 to 2.9 g / cm ³ . In particular, in a lithium ion secondary battery used as a vehicle-mounted power source, at least one (preferably both) of the positive electrode mixture layer mass (mg / cm ² ) and the positive electrode mixture layer density (g / cm ³ ) is satisfied. It is preferable.

≪Negative electrode mixture layer≫
In a preferred embodiment, the negative electrode mixture layer 44 is a layer mainly composed of a negative electrode active material. The negative electrode mixture layer 44 may contain an optional component such as a binder as required in addition to the negative electrode active material.

  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. A carbon material is mentioned as a suitable negative electrode active material. Particulate carbon materials (carbon particles) having a graphite structure (layered structure) at least partially are preferable. Any carbon material of a so-called graphitic material (graphite), non-graphitizable carbon material (hard carbon), easily graphitized carbon material (soft carbon), or a combination of these materials is preferably used. obtain. Among these, graphite particles such as natural graphite can be preferably used. Carbon particles in which amorphous (amorphous) carbon is added to the surface of graphite may be used. The ratio of the negative electrode active material in the entire negative electrode mixture layer is not particularly limited, but it is usually appropriately about 50% by mass or more, preferably about 90 to 99% by mass (for example, about 95 to 99% by mass). It is.

  As a binder, the thing similar to the positive electrode mentioned above can be used individually or in combination of 2 or more types. What is necessary is just to select the addition amount of a binder suitably according to the kind and quantity of a negative electrode active material, for example, can be about 1-5 mass% of the whole negative mix layer.

  As the negative electrode current collector 42, a conductive member made of a metal having good conductivity is preferably used. For example, copper or an alloy containing copper as a main component can be used. Further, the shape of the negative electrode current collector 42 can be in various forms like the positive electrode current collector 32. As in the present embodiment, in the lithium ion secondary battery 100 including the wound electrode body 20, a sheet-like copper negative electrode current collector 42 can be preferably used. In this embodiment, for example, a copper sheet (copper foil) having a thickness of about 5 μm to 30 μm can be preferably used as the negative electrode current collector 42.

The negative electrode mixture layer 44 is, for example, a paste or slurry composition (for forming a negative electrode mixture layer) in which a negative electrode active material (typically particles) is dispersed in an appropriate solvent (eg, water, NMP, etc.). The composition can be preferably produced by applying the composition to the negative electrode current collector 42 and drying the composition. This drying can be performed under heating as necessary. After drying, the whole may be pressed as necessary. The mass (total mass of both surfaces) of the negative electrode mixture layer 44 provided per unit area of the negative electrode current collector 42 is suitably, for example, about 6 to 30 mg / cm ² . The density of the negative electrode mixture layer 44 can be, for example, about 0.9 to 1.5 g / cm ³ . Particularly, in a lithium ion secondary battery used as a vehicle-mounted power source, at least one (preferably both) of the negative electrode mixture layer mass (mg / cm ² ) and the negative electrode mixture layer density (g / cm ³ ) is satisfied. It is preferable.

  As the separator 50 interposed between the positive electrode sheet 30 and the negative electrode sheet 40, the same separator as a general separator in the field can be used without particular limitation. For example, a porous sheet made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, or polyamide, a nonwoven fabric, or the like can be used. Preferable examples include a single layer or multilayer structure porous sheet (microporous resin sheet) mainly composed of one or more kinds of polyolefin resins. For example, a PE sheet, a PP sheet, a sheet having a three-layer structure (PP / PE / PP structure) in which PP layers are laminated on both sides of the PE layer, and the like can be suitably used. The thickness of the separator is preferably set within a range of approximately 10 μm to 40 μm, for example.

≪Nonaqueous electrolyte≫
As the nonaqueous electrolytic solution 90, a solution containing at least a nonaqueous solvent and a BP-oxalato compound is used. Typically, in addition to a non-aqueous solvent and a BP-oxalato compound, a non-aqueous electrolyte solution further containing a lithium compound (supporting electrolyte) that can be dissolved in the non-aqueous solvent and supply lithium ions is used.

  As the non-aqueous solvent, the same conventional electrolyte solution for a lithium ion secondary battery can be used. Such a nonaqueous electrolytic solution typically includes a nonaqueous solvent and a lithium compound (supporting electrolyte) that can be dissolved in the solvent to supply lithium ions. 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 an electrolytic solution for a secondary battery can be used.

  Preferable examples of the non-aqueous solvent for electrolytic solution in the technique disclosed herein include non-aqueous solvents mainly composed of carbonates. In the non-aqueous secondary battery including the non-aqueous electrolyte solution having such a composition, the application significance of the technology disclosed herein is particularly great. For example, the nonaqueous solvent contains one or more carbonates, and the total volume of these carbonates is 60% by volume or more (more preferably 75% by volume or more, and further preferably 90% by volume) of the total volume of the nonaqueous solvent. The non-aqueous electrolyte solution occupying the volume may be preferably 100% by volume.

≪BP-oxalato compound≫
A typical example of the BP-oxalato compound in the technology disclosed herein is an oxalato complex having a structural portion in which at least one oxalate ion (C ₂ O ₄ ²⁻ ) is coordinated to boron (B) or phosphorus (P). It is. As a preferable BP-oxalato compound, a B element-containing oxalate salt represented by the following formula (II) or (III) is exemplified.

Here, R ₁ and R ₂ in formula (II) are each independently a halogen atom (for example, F, Cl, Br, preferably F) and a carbon number of 1 to 10 (preferably 1 to 3). Selected from perfluoroalkyl groups. A ^{+ in} formulas (I) and (II) may be either an inorganic cation or an organic cation. Specific examples of inorganic cations include alkali metal cations such as Li, Na and K; alkali metal cations such as Li, Na and K; alkaline earth metal cations such as Be, Mg and Ca; Zn, Cu, Co, Fe, Ni, Mn, Ti, Pb, Cr, V, Ru, Y, metal cations such as lanthanoids, actinoids, protons, and the like. Specific examples of organic cations include tetraalkylammonium ions such as tetrabutylammonium ion, tetraethylammonium ion and tetramethylammonium ion; trialkylammonium ions such as triethylmethylammonium ion and triethylammonium ion; other pyridinium ions and imidazoliums Ion, tetraethylphosphonium ion, tetramethylphosphonium ion, tetraphenylphosphonium ion, triphenylsulfonium ion, triethylsulfonium ion; and the like. Examples of preferred cations include Li ions, tetraalkylammonium ions and protons.

  Another example of the preferred BP-oxalato compound is a P element-containing oxalate salt represented by the following formula (IV) or (V).

In the above formulas (IV) and (V), an example in which the cation is Li ion is shown, but other cation may be used in the same manner as A ⁺ in formulas (II) and (III). Further, F in the above formulas (IV) and (V) is independently F and other halogen atoms (for example, F, Cl, Br. Preferably, F is the same as R ₁ and R ₂ in formula (II). ) And perfluoroalkyl groups having 1 to 10 (preferably 1 to 3) carbon atoms.

  Such a BP-oxalato compound can be prepared by a known method, or can be obtained by purchasing a commercially available product. Usually, as the BP-oxalato compound, a B element-containing oxalate salt represented by the above formula (III) can be preferably used. Among these, a preferable oxalato compound includes lithium bis (oxalato) borate represented by the formula (I) (hereinafter sometimes referred to as “LiBOB”).

  In the non-aqueous electrolyte used for the construction of the battery disclosed herein, the concentration of the BP-oxalato compound is such that the compound is stably dissolved in the normal use temperature range of the battery (for example, -30 ° C to 60 ° C). The concentration is not particularly limited. Usually, it is appropriate to make the concentration of the oxalato compound satisfying the preferred A / X disclosed herein. From the viewpoint of easy adjustment of A / X to a preferable value and ease of preparation of the electrolytic solution, the concentration of the oxalato compound is usually about 0.005 mol / L to 0.20 mol / L (for example, about 0.005 mol / L). A non-aqueous electrolyte solution of about 01 mol / L to about 0.10 mol / L can be preferably used.

≪Supporting electrolyte≫
As the supporting electrolyte, various materials known to be capable of functioning as a supporting electrolyte for a lithium ion secondary battery can be appropriately employed. For example, 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 ₁ or more selected from various lithium salts (excluding lithium salts belonging to the BP-oxalato compound) known to be capable of functioning as a supporting electrolyte for lithium ion secondary batteries, such as ₄ be able to. Of these, LiPF ₆ can be preferably used.

The concentration of the supporting electrolyte (supporting salt) is not particularly limited, and can be, for example, the same level as that of a conventional lithium ion secondary battery. Usually, a nonaqueous electrolytic solution containing a supporting electrolyte 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) can be preferably used.
The nonaqueous electrolytic solution in the technology disclosed herein can contain components other than the BP-oxalato compound, the supporting electrolyte, and the nonaqueous solvent described above as long as the effects of the present invention are not significantly impaired. Examples of such optional components include additives (typically lithium salts) such as difluorophosphoric acid and monofluorophosphate. Or the non-aqueous electrolyte which does not contain components other than a BP-oxalato compound, a supporting electrolyte, and a non-aqueous solvent substantially may be sufficient.

  In the technology disclosed herein, the ratio X / Y between the total positive electrode active material DBP absorption amount X (mL) and the total negative electrode active material DBP absorption amount Y (mL) is higher than that of a conventional general non-aqueous secondary battery. Is also characterized by being set large.

≪Total active material DBP absorption≫
Here, the total positive electrode active material DBP absorption amount X (mL) is the DBP absorption amount x (mL / 100 g) per 100 g of the positive electrode active material, and the mass m _p (g) of the positive electrode active material of the battery. From the following formula: X (mL) = (x × m _p ) / 100; Similarly, the total negative electrode active material DBP absorption amount Y (mL) is the DBP absorption amount y (mL / 100 g) per 100 g of the negative electrode active material, and the mass m _n (g) of the negative electrode active material of the battery. From the following formula: Y (mL) = (y × m _n ) / 100;

≪DBP absorption per unit mass≫
The DBP absorption amount x, y per 100 g of the positive electrode active material and the negative electrode active material is determined according to JIS K6217-4 “Carbon black for rubber—Basic characteristics—Part 4: Determination of DBP absorption amount”. Here, DBP (dibutyl phthalate) is used as the reagent liquid, and the powder to be inspected (each powder of the positive electrode active material and the negative electrode active material) is titrated with a constant speed burette, and the change in viscosity characteristics is measured with a torque detector. Then, the addition amount of the reagent liquid per unit mass (here, 100 g) of the powder to be inspected corresponding to a torque of 70% of the generated maximum torque is defined as the DBP absorption amount (mL / 100 g). As a DBP absorption amount measuring device, for example, an absorption amount measuring device manufactured by Asahi Research Institute, Ltd., model “S410” may be used.

≪Total active material DBP absorption ratio X / Y≫
In a typical aspect of the technology disclosed herein, the total positive electrode active material DBP absorption amount X and the total negative electrode active material DBP absorption amount Y have a relationship satisfying 0.60 ≦ X / Y. According to such a configuration, the BP-oxalato compound added to the electrolyte solution has a favorable effect for the battery (for example, an effect of suppressing an increase in resistance) as compared with a battery in which X / Y is less than 0.60. The amount of distribution to the negative electrode side that does not contribute to such a favorable effect (or can exhibit a disadvantageous effect for the battery) can be reduced. Therefore, the BP-oxalato compound added to the electrolytic solution can be used more effectively (the ratio of the oxalato compound effectively used can be increased), and adverse effects caused by the compound can be suppressed. As a result, the trade-off associated with the use of the BP-oxalato compound is eliminated or reduced, and a higher-performance nonaqueous electrolyte battery can be realized. X / Y may be 0.65 or more (for example, 0.70 or more). Also, from the viewpoints of availability of positive electrode active material and / or negative electrode active material, ease of production of positive electrode and / or negative electrode, stability of battery performance, capacity ratio (initial capacity ratio) between positive electrode and negative electrode, etc. X / Y is suitably 1.25 or less (for example, 1.2 or less and may be less than 1.0).

As a method of increasing the value of X / Y, there are (1) a method of increasing X and (2) a method of decreasing Y. Here, if the mass _mn of the negative electrode active material of the battery is reduced, Y decreases, but if _mn is too small, the balance between the positive electrode capacity and the negative electrode capacity is lost, and depending on the use conditions (charging conditions, etc.) of the battery. May cause inconveniences such as easy deposition of metallic lithium. In addition, the actual reaction area of the negative electrode active material (the area that can be effectively used for storage and release of Li ⁺ ) is reduced, and the battery performance (output performance, quick charge performance, etc.) tends to decrease. Although X increases if a large amount of mass m _p of the positive electrode active material included in the battery, when too much m _p, capacity balance equally positive and negative electrodes in the case m _n is too small is likely to collapse. Further, since the volume of the positive electrode active material increases, the energy density of the battery tends to decrease. Therefore, it is preferable to realize the above X / Y by using a material (one or both of the positive electrode active material and the negative electrode active material) whose DBP absorption amount per unit mass is in the preferable range disclosed herein.

Although not particularly limited, in the non-aqueous secondary battery disclosed herein, the ratio (C _N / C _P ) of the initial capacity (C _N ) of the negative electrode to the initial capacity (C _P ) of the positive electrode is usually For example, 1.0 to 2.0 is appropriate, and 1.2 to 1.9 is preferable. If C _N / C _P is too small, inconveniences such as easy deposition of metallic lithium may occur depending on the use conditions of the battery (for example, during rapid charging). When C _N / C _P is too large, the energy density of the battery may be easily lowered.

The initial capacity (C _P ) of the positive electrode can be measured, for example, by the following method. That is, a measurement cell (half-cell) is constructed using a positive electrode sheet having a positive electrode mixture layer on a positive electrode current collector punched into a predetermined size as a measurement electrode and a metal lithium electrode as a counter electrode. For the measurement cell, the positive electrode active material was changed to lithium until the potential of the measurement electrode was 4.2 V (metal lithium reference; hereinafter, the metal lithium reference voltage was expressed as “V (vs. Li / Li ⁺ )”). The first charge of desorbing ions and then inserting lithium ions into the positive electrode active material (typically inserting lithium ions until the potential of the measurement electrode reaches 3.0 V (vs. Li / Li ⁺ )). By performing the discharge cycle, the initial capacity [mAh / cm ² ] per unit area of the positive electrode sheet is obtained. By multiplying this by the positive electrode mixture layer forming area [cm ² ] of the positive electrode sheet provided in the non-aqueous secondary battery, the initial capacity (C _P ) of the positive electrode is calculated. The initial capacity (C _N ) of the negative electrode is determined by inserting lithium ions into the negative electrode active material until the potential of the measurement electrode reaches 0.02 V in the first charge / discharge cycle, and then releasing the lithium ions (typically It can be calculated in the same manner as the initial capacity (C _P ) of the positive electrode except that the lithium ion is released until the potential of the measurement electrode becomes 1.5 V (vs. Li / Li ⁺ ). The initial capacity ratio (C _N / C _P ) between the positive electrode and the negative electrode can be obtained from C _P and C _N thus grasped.

≪Relationship between the total number of moles A of BP-oxalato compound and the total positive electrode active material DBP absorption amount X≫
The relationship between the total mole number A (mmol) of the BP-oxalato compound contained in the battery and the total positive electrode active material DBP absorption amount X (mL) is expressed by the following formula: 0.02 ≦ A / X (mmol / mL) ) ≦ 0.30 (more preferably 0.04 ≦ A / X (mmol / mL) ≦ 0.25, for example 0.05 ≦ A / X (mmol / mL) ≦ 0.20); . According to the battery of this aspect, the function of the BP-oxalato compound is more appropriately exhibited, and higher performance can be realized. When A / X is too small, the amount of the oxalato compound supplied per actual reaction area of the positive electrode active material is too small, and the effect of adding the compound (for example, the effect of suppressing an increase in resistance) tends to be small. . If A / X is too large, the amount (absolute amount) of the oxalato compound distributed to the negative electrode is too large even with the configuration satisfying the preferred X / Y disclosed herein, and the oxalato compound distributed to the negative electrode The initial characteristics of the battery tend to deteriorate due to the influence of the above.

  The reason why the initial efficiency of the battery tends to decrease when the absolute amount of the BP-oxalato compound distributed to the negative electrode is increased is, for example, that the compound is reductively decomposed on the negative electrode side (that is, the cost for the reductive decomposition). It is conceivable that the amount of electricity lost becomes irreversible capacity and reduces efficiency). The reason why the initial resistance of the battery tends to increase when the absolute amount of the BP-oxalato compound distributed to the negative electrode is increased is that the decomposition product generated by the reductive decomposition becomes a resistance component on the negative electrode side (for example, It is conceivable to increase the resistance of the film formed on the surface of the negative electrode active material layer.

≪DBP absorption x of positive electrode active material≫
The DBP absorption amount x (mL / 100 g) per 100 g of the positive electrode active material is preferably 20 mL / 100 g or more (for example, 25 mL / 100 g or more). When x is too small, the mass m _p of the positive electrode active material to the mass m _n of the negative electrode active material is too large, the energy density of the battery may tend to decrease. In addition, in order to satisfy the above X / Y, a negative electrode active material having a DBP absorption amount y (mL / 100 g) per 100 g that is too small may be used, and the reaction resistance of the negative electrode may easily increase. . The upper limit of the DBP absorption amount x is not particularly limited, but from the viewpoints of availability of the positive electrode active material, ease of production, durability (for example, mechanical strength of the positive electrode active material particles, structure maintainability with respect to the cycle test), etc. Usually, it is preferable to use a positive electrode active material in which x is 75 mL / 100 g or less (typically 60 mL / 100 g or less, for example, 50 mL / 100 g or less).

≪DBP absorption amount y of negative electrode active material≫
The DBP absorption amount y (mL / 100 g) per 100 g of the negative electrode active material is preferably 75 mL / 100 g or less (for example, 60 mL / 100 g or less). When y is too large, it becomes difficult to select a positive electrode active material that can satisfy the above X / Y, or the negative electrode active material is not easily adapted to a liquid medium (for example, water) to prepare a composition for forming a negative electrode mixture layer. It may become difficult to do. The amount m _n of the negative electrode active material that can be used to satisfy the above X / Y is too small relative to the amount m _p of the positive electrode active material, metal lithium is easily precipitated by the use conditions such as a battery Inconvenience can occur. On the other hand, if the DBP absorption y is too small, the actual reaction area of the negative electrode may be too small, and the output resistance of the battery may easily increase. Therefore, normally, the negative electrode active material whose y is 35 mL / 100g or more (for example, 40 mL / 100g or more) is preferable.

≪DBP absorption ratio x / y≫
In a preferred embodiment, the relationship between the DBP absorption amount x (mL) per 100 g of the positive electrode active material and the DBP absorption amount y (mL) per 100 g of the negative electrode active material is expressed by the following formula: 0.55 ≦ x /Y≦1.15 (for example, 0.60 ≦ x / y ≦ 1.10); When x / y is too large, here by the amount m _p becomes too much of the positive electrode active material required to meet the preferred X / Y disclosed, the energy density of the battery tends to decrease. If x / y is too small, the amount _{mn of the} negative electrode active material that can be used to satisfy the above X / Y becomes too small, resulting in inconveniences such as metal lithium being liable to precipitate depending on the use conditions of the battery. obtain.

≪Average particle size≫
The DBP absorption amount x of the positive electrode active material may vary depending on the particle size (for example, average particle diameter), particle structure, composition (for example, affinity for DBP), surface state, and the like of the positive electrode active material. If other conditions (particle structure and the like) are the same, the DBP absorption amount x tends to increase as the average particle size (particle outer shape) decreases. On the other hand, if the particle size of the positive electrode active material is too large, the output characteristics of the battery may be easily degraded. On the other hand, if the particle size is too small, the internal resistance of the positive electrode mixture layer tends to increase, or the handleability of the positive electrode active material may decrease. Therefore, for example, a positive electrode active material having an average particle diameter of 2 μm to 10 μm (more preferably 3 μm to 8 μm) and having a preferable DBP absorption amount x disclosed herein can be preferably used.

  Similarly, the DBP absorption amount y of the negative electrode active material may vary depending on the particle size (average particle diameter, etc.), particle structure, composition, surface state, etc. of the negative electrode active material. From the viewpoint of battery performance (for example, output characteristics) and handling property of the negative electrode active material, for example, the average particle size is in the range of 5 μm to 30 μm (more preferably 8 μm to 25 μm), and the preferred DBP absorption disclosed herein. A negative electrode active material having an amount y can be preferably employed.

  In the present specification, the “average particle diameter” refers to a median diameter (D50) obtained by a general laser diffraction particle size distribution measuring apparatus unless otherwise specified. In the present specification, the term “particle” refers to a structural unit that acts as an independent particle in a material state unless otherwise specified. Therefore, for example, in the case of particles that form a secondary particle in which a plurality of primary particles are aggregated and are dispersed as secondary particles (while maintaining the appearance of an aggregate of primary particles) when dispersed in a solvent. Unless otherwise specified, the particle means a secondary particle. In the secondary particles of this form, the average particle size obtained by the laser diffraction particle size distribution measuring apparatus described above is the average particle size for the secondary particles.

≪Particle structure of positive electrode active material≫
In general, the DBP absorption x of a positive electrode active material powder for lithium ion batteries (for example, a lithium transition metal oxide powder having a layered structure) composed of dense solid structure particles is about 10 to 20 mL / 100 g. If the other conditions (particle size and the like) are approximately the same, the DBP absorption x of the porous or hollow structure particles tends to be larger than the DBP absorption x of the solid particles. As the positive electrode active material in the technology disclosed herein, particles having such a porous structure or hollow structure can be preferably used. At least a part of the positive electrode active material included in the battery (typically 5% by mass or more, for example, 30% by mass or more, preferably 50% by mass or more, and may be 70% by mass or more, substantially By using particles having a porous structure or hollow structure, the DBP absorption amount x of the positive electrode active material can be increased as compared with the case where only solid structure particles are used. it can. Thus, the preferred X / Y value disclosed herein can be obtained without using a positive electrode active material having an extremely small average particle size or without extremely increasing the amount of the positive electrode active material relative to the negative electrode active material. It can be realized.

  Here, the porous structure refers to a structure (sponge-like structure) in which a substantial part and a void part are mixed over the entire particle. As a typical example of a positive electrode active material having a porous structure, a positive electrode active material obtained by a so-called spray baking method (sometimes referred to as a spray dry method) (typically a secondary in which primary particles are collected). It takes the form of particles.). The hollow structure refers to a structure having a shell portion and a hollow portion (cavity portion) inside thereof. In a preferred embodiment, the shell portion may have a through hole that allows the outside of the particle to communicate with the hollow portion (hereinafter, the hollow structure having the through hole in the shell portion is referred to as a “perforated hollow structure”. The active material particles having such a structure are sometimes referred to as “porous hollow active material particles”. The particles of such a hollow structure (meaning that it includes a perforated hollow structure unless otherwise specified) are such that the substantial part is biased toward the shell part, and a space is secured in the hollow part. In this respect, the particles having a porous structure are clearly distinguished from each other in terms of structure.

  In a preferred embodiment of the technology disclosed herein, at least a part of the positive electrode active material (typically 5% by mass or more, for example, 30% by mass or more, preferably 50% by mass or more, and 70% by mass or more). Or substantially all of the active material particles having a perforated hollow structure. Such active material particles having a hollow structure can have an excellent balance between the particle diameter and the DBP absorption amount x as compared with particles having a porous structure as a whole. Moreover, the battery excellent in the durability with respect to charging / discharging cycles (less deterioration of battery performance) can be given. As the material of the active material particles having such a hollow structure, lithium transition metal oxide (typically, lithium transition metal oxide having a layered structure) is preferable. A lithium transition metal oxide (typically lithium nickel oxide) containing at least Ni as a transition metal is particularly preferred.

≪Method for producing perforated hollow active material particles≫
The porous hollow active material particles having the lithium transition metal oxide as a constituent material can be preferably produced, for example, as follows. The production method includes an aqueous solution containing at least one of transition metal elements contained in the lithium transition metal oxide constituting the active material particles (in a preferred embodiment, all of the metal elements other than lithium contained in the oxide). It includes precipitating the transition metal hydroxide from a solution under appropriate conditions (raw material hydroxide generation step). Moreover, the transition metal hydroxide and the lithium compound are mixed (mixing step). Furthermore, it can include firing the mixture (firing step). Hereinafter, a preferred embodiment of such a production method will be described in detail by taking as an example the case of producing a perforated hollow active material particle composed of a LiNiCoMn oxide having a layered structure. It is not intended to be limited to hollow active material particles.

In a preferred embodiment of the method for producing active material particles disclosed herein, the raw material hydroxide generation step supplies ammonium ions (NH ₄ ⁺ ) to an aqueous solution of the transition metal compound, and transition metal water from the aqueous solution. Depositing oxide particles. The solvent (aqueous solvent) constituting the aqueous solution is typically water, and may be a mixed solvent containing water as a main component. As the solvent other than water constituting the mixed solvent, an organic solvent (such as a lower alcohol) that can be uniformly mixed with water is preferable. The aqueous solution of the transition metal compound (hereinafter also referred to as “transition metal solution”) constitutes the lithium transition metal oxide in accordance with the composition of the lithium transition metal oxide constituting the active material particles as the production target. It contains at least one (preferably all) transition metal elements (here, Ni, Co and Mn). For example, a transition metal solution containing one or more compounds that can supply Ni ions, Co ions, and Mn ions in an aqueous solvent is used. As the metal ion source compound, sulfates, nitrates, chlorides, and the like of the metals can be appropriately employed. For example, a transition metal solution having a composition in which nickel sulfate, cobalt sulfate and manganese sulfate are dissolved in an aqueous solvent (preferably water) can be preferably used.

The NH ₄ ⁺ may be supplied to the transition metal solution in the form of an aqueous solution (typically an aqueous solution) containing NH ₄ ⁺ , for example, and supplied by directly blowing ammonia gas into the transition metal solution. These supply methods may be used in combination. An aqueous solution containing NH ₄ ⁺ can be prepared, for example, by dissolving a compound (ammonium hydroxide, ammonium nitrate, ammonia gas, or the like) that can be an NH ₄ ⁺ source in an aqueous solvent. In a preferred embodiment, NH ₄ ⁺ is supplied in the form of an aqueous ammonium hydroxide solution (ie, aqueous ammonia).

≪Nucleation stage≫
In a preferred embodiment, the raw material hydroxide generation step comprises a step of depositing transition metal hydroxide nuclei from the transition metal solution (nucleation generation step) and a step of growing the nuclei (particle growth step). Including. In a preferred embodiment, both the nucleation step and the particle growth step are performed in the presence of ammonium ions. At least the particle growth step is preferably performed while controlling the ammonium ion concentration in the solution (for example, controlling it to a predetermined value or less). The particle growth stage is preferably carried out under alkaline conditions at a pH lower than that in the nucleation stage.

  From the viewpoint that it is easy to obtain porous hollow active material particles with little variation (for example, a small number ratio of particles whose particle size or particle structure is greatly deviated from the average), in the nucleation stage, from the transition metal solution, It is preferable to deposit a large number of nuclei within a short time (eg, almost simultaneously). For example, the nuclei may be precipitated from a solution in which the transition metal hydroxide is in a supersaturated state (for example, by allowing the solution to reach a critical degree of supersaturation). In order to suitably realize such a precipitation mode, it is advantageous to perform the nucleation step under a condition of pH 12 or more (typically pH 12 or more and 14 or less, for example, pH 12.2 or more and 13 or less).

The NH ₄ ⁺ concentration in the nucleation stage is not particularly limited, but usually it is suitably about 25 g / L or less, for example, about 3 to 25 g / L. The pH and NH ₄ ⁺ concentration can be adjusted by appropriately balancing the usage amount of the ammonia water and the usage amount of an alkaline agent (a compound having an action of tilting the liquidity to alkalinity). The amount used can be grasped as a supply rate to the reaction system, for example. As the alkaline agent, for example, sodium hydroxide, potassium hydroxide and the like can be typically used in the form of an aqueous solution. In a preferred embodiment, an aqueous sodium hydroxide solution is used. In addition, in this specification, the value of pH shall mean pH value on the basis of liquid temperature of 25 degreeC.

≪Particle growth stage≫
In the particle growth stage, the transition metal hydroxide nuclei (typically particles) precipitated in the nucleation stage are preferably grown under alkaline conditions at a lower pH than in the nucleation stage. For example, the growth may be performed at a pH of less than 12 (typically a pH of 10 or more and less than 12, preferably a pH of 10 or more and 11.8 or less, such as a pH of 11.0 or more and 11.8 or less). The transition metal hydroxide particles (raw material hydroxide particles) obtained through this particle growth stage preferably have a structure in which the density inside the particles is lower than the density of the outer surface portion of the particles. In order to stably obtain transition metal hydroxide particles having such a structure, it is important not to make the NH ₄ ⁺ concentration too high (suppress it low) in the particle growth stage. This increases the deposition rate of the transition metal hydroxide (here, the composite hydroxide containing Ni, Co, and Mn), and is a raw material water suitable for forming the apertured hollow active material particles disclosed herein. Oxide particles (in other words, raw material hydroxide particles that easily form a fired product having a perforated hollow structure) can be effectively produced. Usually, it is appropriate that the NH ₄ ⁺ concentration in the particle growth stage is 25 g / L or less, preferably 15 g / L or less, more preferably 10 g / L or less (for example, 8 g / L or less). The lower limit of the NH ₄ ⁺ concentration is not particularly limited. However, from the viewpoints of ease of management of production conditions, quality stability, mechanical strength (for example, hardness) of the obtained active material particles, etc., the NH ₄ ⁺ concentration is usually set. It is appropriate to set it to 1 g / L or more (preferably 3 g / L or more). The pH and NH ₄ ⁺ concentration in the particle growth stage can be adjusted in the same manner as in the nucleation stage.

In a preferred embodiment, the NH ₄ ⁺ concentration in the particle growth stage is 7 g / L or less (typically 1 to 7 g / L, for example, 3 to 7 g / L). NH ₄ ⁺ concentration in the particle growth step, for example, may be a substantially the same level as NH ₄ ⁺ concentration in the nucleation stage may be lower than NH ₄ ⁺ concentration in the nucleation stage. In addition, the precipitation rate of the transition metal hydroxide is, for example, the transition metal ions contained in the liquid phase of the reaction liquid with respect to the total number of moles of transition metal ions contained in the transition metal solution supplied to the reaction liquid. It can be grasped by examining the transition of the total number of moles (total ion concentration).

In implementing the technology disclosed herein, it is necessary to clarify the reason why raw material hydroxide particles suitable for the formation of perforated hollow active material particles can be obtained by keeping the NH ₄ ⁺ concentration low as described above. For example, the following can be considered. That is, for example, the following equilibrium reaction occurs in the transition metal solution. In the following formulas 1 and 2, M ₁ is a transition metal, and at least Ni is included in this embodiment.

Here, when the NH ₃ concentration in the transition metal solution is lowered, the equilibrium of Equation 1 moves to the left and the concentration of M ₁ ²⁺ increases, so the equilibrium of Equation 2 moves to the right and M ₁ (OH) _2. Generation is promoted. In other words, M ₁ (OH) ₂ is likely to precipitate. In such a situation where M ₁ (OH) ₂ is likely to precipitate, M ₁ (OH) ₂ is mainly precipitated because of the transition metal hydroxide already precipitated (nuclei generated in the nucleation stage, or M ₁ (OH) ₂ that occurs in the vicinity of the outer surface of the transition metal hydroxide particles in the course of the grain growth stage and precipitates inside the precipitate is reduced. As a result, raw material hydroxide particles having a structure in which the internal density is lower than the density of the outer surface portion (raw material hydroxide particles suitable for the formation of perforated hollow active material particles, which are perforated hollow active material particles It is presumed that the precursor particles are formed as well. On the other hand, if the NH ₄ ⁺ concentration in the particle growth stage is too high, the precipitation rate of M ₁ (OH) ₂ becomes small, so the difference between the precipitation amount near the outer surface and the precipitation amount inside becomes small, It is presumed that the raw material hydroxide particles tend not to be formed.

  In each of the nucleation stage and the particle growth stage, the temperature of the reaction solution is preferably controlled so as to be a substantially constant temperature (for example, a predetermined temperature ± 1 ° C.) in a range of about 30 ° C. to 60 ° C. The temperature of the reaction solution may be approximately the same in the nucleation stage and the particle growth stage. Moreover, it is preferable to maintain the reaction liquid and the atmosphere in the reaction tank in a non-oxidizing atmosphere through the nucleation stage and the particle growth stage. Further, the total number of moles (total ion concentration) of Ni ions, Co ions and Mn ions contained in the reaction solution is set to, for example, about 0.5 to 2.5 mol / L through the nucleation stage and the particle growth stage. It is preferably about 1.0 to 2.2 mol / L. The transition metal solution may be replenished (typically continuously supplied) in accordance with the deposition rate of the transition metal hydroxide so that the total ion concentration is maintained. The amounts of Ni ions, Co ions, and Mn ions contained in the reaction solution correspond to the composition of the active material particles as the target product (that is, the molar ratio of Ni, Co, and Mn in the LiNiCoMn oxide constituting the active material particles). It is preferable to set the quantity ratio.

≪Mixing process≫
In a preferred embodiment, the transition metal hydroxide particles thus produced (here, composite hydroxide particles containing Ni, Co and Mn) are separated from the reaction solution, washed and dried. Then, the transition metal hydroxide particles and the lithium compound are mixed at a desired quantitative ratio to prepare an unfired mixture (mixing step). In this mixing step, typically, the quantitative ratio corresponding to the composition of the active material particles as the target (that is, the molar ratio of Li, Ni, Co, Mn in the LiNiCoMn oxide constituting the active material particles) Li compound and transition metal hydroxide particles are mixed. As the lithium compound, lithium compounds that can be converted into oxides upon heating, such as lithium carbonate and lithium hydroxide, can be preferably used.

≪Baking process≫
And the said mixture is baked and the active material particle of a hole hollow structure is obtained (baking process). This firing step is typically performed in an oxidizing atmosphere (for example, in the air). The firing temperature in this firing step can be set to 700 ° C. to 1100 ° C., for example. It is preferable that the maximum baking temperature be 800 ° C or higher (preferably 800 ° C to 1100 ° C, for example, 800 ° C to 1050 ° C). According to the maximum firing temperature within this range, the sintering reaction of the primary particles of the lithium transition metal oxide (preferably Ni-containing Li oxide, here LiNiCoMn oxide) can proceed appropriately. Preferably, the fired product is crushed and sieved after the firing step to adjust the particle size of the active material particles.

  In a preferred embodiment, the mixture is calcined at a temperature T1 of 700 ° C. to 900 ° C. (that is, 700 ° C. ≦ T1 ≦ 900 ° C., for example, 700 ° C. ≦ T1 ≦ 800 ° C., typically 700 ° C. ≦ T1 <800 ° C.). A second firing step, and a result obtained through the first firing step is fired at a temperature T2 of 800 ° C. to 1100 ° C. (ie, 800 ° C. ≦ T2 ≦ 1100 ° C., for example, 800 ° C. ≦ T2 ≦ 1050 ° C.) And a firing step. By this, the active material particle of a perforated hollow structure can be formed more efficiently. T1 and T2 are preferably set so that T1 <T2.

  The first firing stage and the second firing stage are performed continuously (for example, by holding the mixture at the first firing temperature T1, and subsequently raising the temperature to the second firing temperature T2 and maintaining the temperature at T2. Alternatively, after maintaining at the first firing temperature T1, it is once cooled (for example, cooled to room temperature) and, if necessary, crushed and sieved before being subjected to the second firing stage. Good.

  In the technology disclosed herein, the first firing stage is a temperature T1 in which the sintering reaction of the target lithium transition metal oxide proceeds and is lower than the melting point and lower than the second firing stage. It can be grasped as a stage for firing. Further, the second firing stage should be understood as a stage in which the sintering reaction of the target lithium transition metal oxide proceeds and the firing is performed at a temperature T2 that is lower than the melting point and higher than the first firing stage. Can do. It is preferable to provide a temperature difference of 50 ° C. or higher (typically 100 ° C. or higher, for example, 150 ° C. or higher) between T1 and T2.

≪Structure of porous hollow active material particles≫
A typical structure of the perforated hollow active material particles produced by such a method will be described with reference to a scanning electron microscope (SEM) image shown in FIG. This active material particle 610 penetrates the shell portion 612, the hollow portion 614, and the hollow portion 614 of the particle 610 and the outside of the shell portion 612 (outside of the particle 610) spatially continuous through the shell portion 612. A hole 616 is provided. The constituent material of the perforated hollow active material particles 610 shown in FIG. 3 is LiNiCoMn oxide. As shown in FIG. 3, the shell portion 612 is densely sintered at portions other than the through-holes 616, and no gap penetrating the inside and outside of the shell portion 612 is recognized at this portion.

  The DBP absorption amount x (mL / 100 g) of such porous hollow active material particles 610 may vary depending on, for example, the average particle diameter of the particles 610, the particle porosity, the structure of the shell 612 and the through holes 616, and the like. For example, porous hollow active material particles having an average particle diameter of 3 μm to 8 μm and exhibiting a preferable DBP absorption amount x disclosed herein can be preferably employed as the positive electrode active material or a component thereof. The adjustment of the average particle diameter is, for example, in the above-described method for producing porous hollow active material particles through pH in the nucleation stage, time for continuing the particle growth process, precipitation rate of transition metal hydroxide in the particle growth process, etc. It can be carried out. The deposition rate of the transition metal hydroxide can be adjusted through, for example, the concentration, pH, reaction system temperature, etc. of one or more chemical species related to Formula 1 or Formula 2 above. Alternatively, the average particle diameter may be adjusted by selecting particles by general sieving. Such an average particle diameter adjusting method can be carried out alone or in appropriate combination.

<Particle porosity>
As a positive electrode active material or a component thereof in the technology disclosed herein, the particle porosity is 2% or more (typically 5% or more, preferably 10% or more), and the above preferable DBP absorption amount x It is possible to preferably employ porous active material particles having pores. If the particle porosity is too small, it may be difficult to sufficiently exhibit the advantages of having a porous hollow structure. The particle porosity may be 20% or more (typically 23% or more, preferably 30% or more). The upper limit of the particle porosity is not particularly limited, but the durability of the active material particles (for example, the ability to withstand compressive stress that can be applied during battery production or use and maintain a hollow hollow shape), ease of production, etc. From this point, it is usually appropriate to set it to 75% or less (for example, 70% or less). The particle porosity can be adjusted, for example, in the above-described method for producing porous hollow active material particles, through the time during which the particle growth step is continued, the deposition rate of transition metal hydroxide in the particle growth step, and the like.

  Here, “particle porosity” refers to the proportion of the apparent volume of the active material particles 610 occupied by the hollow portions 614. This ratio can be grasped based on the cross-sectional SEM image of the active material particles 610. In the cross-sectional SEM image, as shown in FIG. 3, the shell portion 612, the hollow portion 614, and the through-hole 616 of the active material particle 610 can be distinguished by the difference in color tone or shade. For example, for a plurality of active material particles 610 appearing in an arbitrary cross-sectional SEM image of the positive electrode mixture layer, the area A occupied by the hollow portions 614 of the active material particles 610 and the active material particles 610 are apparently The ratio (A / B) with the cross-sectional area B is obtained. Here, the apparent cross-sectional area B occupied by the active material particles 610 refers to the cross-sectional area occupied by the shell portion 612, the hollow portion 614, and the through holes 616 of the active material particles 610. The value of the ratio (A / B) is arithmetically averaged for a plurality of cross-sectional SEM images of the positive electrode mixture layer. Thus, the ratio (A / B) increases as the number of cross-sectional SEM images for which the ratio (A / B) is determined increases and the number of active material particles 610 that is the basis for calculating the ratio (A / B) increases. ) Arithmetic mean converges. The ratio of the hollow portion 614 to the apparent volume of the active material particles 610 (that is, the particle porosity) is generally determined by the average value of the ratio (A / B). Usually, it is preferable to determine the particle porosity based on at least 10 (for example, 20 or more) active material particles 610. Moreover, it is preferable to obtain | require particle | grain porosity based on the cross-sectional SEM image of the positive mix layer in at least arbitrary 3 places (for example, 5 places or more).

≪Structure of shell and through hole≫
As the positive electrode active material or the component thereof in the technology disclosed herein, the circumferential length of the shell portion 612 (the thickness T (k) of the shell portion 612) shown in the cross-sectional SEM image of the porous hollow active material particles 610 is used. It means the length that goes around the cross section of the particle 610 along the center.The part where the shell part 612 is interrupted by the through-hole 616 is complemented from the shape of the shell part 612 on both sides thereof. The length occupied by the hole 616 (corresponding to the passing length of the through-hole 616 at the center of the thickness of the shell 612. When two or more through-holes 616 appear in one cross section, the through-holes The total length of 616 is preferably 30% or less, more preferably 20% or less, and the above DBP absorption amount x can be preferably used. When the length occupied by the through-hole 616 is too large, the durability of the particles 610 (for example, the ability to withstand the compressive stress that can be applied during battery manufacture or use and maintain a perforated hollow shape) may tend to decrease. On the other hand, if the length occupied by the through-hole 616 is too small, the hollow portion 614 of the particle 610 is difficult to be effectively utilized, and the advantage of having a perforated hollow structure may not be sufficiently exhibited. Therefore, the length occupied by the through hole 616 is preferably 0.5% or more, and more preferably 1% or more (for example, 3% or more).

  In a preferred embodiment, among the circumferential lengths of the shell portion 612 in the cross section of the hollow hollow active material particles 610, the average length of the continuous shell portions 612 (continuous without being interrupted by the through holes 616) is the through hole. It is 3 times or more (for example, 3 to 100 times) of the average passing length of 616, and more preferably 5 times or more (for example, 5 to 50 times). The ratio of the length occupied by the through-holes 616 in the circumferential length of the shell 612, and the relationship between the average length of the continuous shells 612 and the average passing length of the through-holes 616 are usually at least 10 (for example, It is preferable to obtain an arithmetic average value based on 20 or more active material particles 610. Moreover, it is preferable to obtain | require based on the cross-sectional SEM image of the positive mix layer in at least arbitrary 3 places (for example, 5 places or more).

≪Hardness of active material particles≫
In the technique disclosed herein, the porous hard active material particles used as the positive electrode active material or its constituent components have an average hardness of approximately 0.5 MPa or more (typically 1.0 MPa or more, for example, 2 (0.0 MPa to 10 MPa) can be preferably employed. Here, the “average hardness” refers to a value obtained by dynamic microhardness measurement performed using a flat diamond indenter with a diameter of 50 μm and under a load speed of 0.5 mN / sec to 3 mN / sec. For the dynamic microhardness measurement, for example, a microhardness meter manufactured by Shimadzu Corporation, model “MCT-W500” can be used. As the hardness measurement is performed for more active material particles, the arithmetic average value of the hardness of those active materials converges. As the average hardness, it is preferable to employ an arithmetic average value based on at least three (preferably five or more) active material particles. The above-described method for producing perforated active material particles including a nucleation step and a particle growth step is suitable as a method for producing perforated active material particles having such average hardness. The perforated hollow active material particles obtained by this method are harder (higher average hardness) and have morphological stability than the positive electrode active material particles having a general porous structure obtained by, for example, a spray firing method. Can be excellent.

As a preferable application target of the above-described method for producing porous hollow active material particles, a hollow hollow made of a lithium transition metal oxide (typically a lithium transition metal oxide having a layered structure) containing at least nickel as a constituent metal element is used. An active material particle is mentioned. For example, production of porous hollow active material particles using a lithium transition metal oxide having a composition represented by the following formula: Li _{1 + a} Ni _b Co _c Mn _(1-bc) M _d O ₂ ; It is suitable for. Here, 0 ≦ a ≦ 0.2, 0.1 <b <0.9, 0.1 <c <0.4, and 0 ≦ d ≦ 0.01. M in the above formula is an additive, for example, at least one selected from the group consisting of Zr, W, Mg, Ca, Na, Fe, Cr, Zn, Si, Sn, Al, B and F. possible. The proportion of Ni in the metal elements other than lithium contained in the lithium transition metal oxide is preferably 5% or more, more preferably 10% or more (for example, 25% or more) in terms of the number of atoms.

  The non-aqueous secondary battery disclosed herein may be one constructed (assembled) using a non-aqueous electrolyte solution containing a BP-oxalato compound, and after the construction, a part of the oxalato compound or All may be altered (decomposition etc.). For example, an electrode body having a positive electrode and a negative electrode satisfying preferable X / Y disclosed herein is accommodated in a container, and a non-aqueous electrolyte containing a BP-oxalato compound is injected into the container to impregnate the electrode body. Typically, most of the oxalato compound contained in the electrolyte decomposes near the surface of the battery positive electrode or negative electrode immediately after the battery is constructed or when the battery is charged for the first time. The inventor reduced the reaction resistance of the positive electrode by forming a film having good ion conductivity on the surface of the positive electrode or by using the oxalato compound decomposed near the surface of the positive electrode as a component of the film. I think that it contributes to. Therefore, in order to exert the application effect of the present invention, it is sufficient that a non-aqueous electrolyte containing an oxalato compound is used at the time of construction of the battery. It is not necessary for the oxalato compound to remain in the battery.

  In addition, the non-aqueous secondary battery constructed using a non-aqueous electrolyte containing a B element-containing oxalato compound (for example, LiBOB) means that, for example, the constituent member of the battery (the surface of the positive and negative electrode mixture layer, etc.) It can be grasped by collecting a measurement sample from the sample and detecting B element by ICP (high frequency inductively coupled plasma) emission analysis, ion chromatography or the like. Further, the amount of the B element-containing oxalato compound (in other words, the amount of the B element-containing oxalato compound supplied into the battery case) in the non-aqueous electrolyte used for the construction of the non-aqueous secondary battery is, for example, Quantifying the amount of B element contained in the positive and negative electrodes by ion chromatography; analyzing the non-aqueous electrolyte stored in the battery container by ion chromatography to quantify the amount of B element contained in the electrolyte; The electrolytic solution can be analyzed by ion chromatography to determine the chemical species caused by LiBOB and its decomposition products;

Similarly, it is a non-aqueous secondary battery constructed using a non-aqueous electrolyte containing a P element-containing oxalato compound, for example, from a constituent member of the battery (such as the surface of the positive / negative electrode mixture layer) to a measurement sample Can be obtained by detecting P element by ICP emission analysis, ion chromatography or the like. According to this analysis, even in a battery using a non-aqueous electrolyte containing LiPF ₆ as a supporting electrolyte, the presence of the P element derived from the P element-containing oxalato compound is distinguished from the P element derived from LiPF _6. Can be recognized. The amount of the P element-containing oxalato compound in the non-aqueous electrolyte used in the construction of the non-aqueous secondary battery is, for example, by analyzing the non-aqueous electrolyte accumulated in the battery container by ion chromatography, It can be grasped by quantifying the chemical species resulting from the P element-containing oxalato compound and its decomposition product.

  In order to grasp the total positive electrode active material DBP absorption amount X (mL) of the battery after assembly of the non-aqueous secondary battery (which may be after the start of use of the battery), for example, the battery is disassembled. The positive electrode mixture is recovered (in a battery having the positive electrode mixture layer formed on the positive electrode current collector, the positive electrode mixture layer is separated from the current collector), and the positive electrode mixture is removed from the oxidizing atmosphere. It is preferable that the organic component (binder or the like) is volatilized and removed by heating in, and the DBP absorption amount X (mL) is measured for the heated residue (inorganic component). The heating residue may include a conductive material (acetylene black or the like) which is an optional component of the positive electrode mixture, but the amount used is usually a small amount (20% of the positive electrode active material on a mass basis) compared to the positive electrode active material. Therefore, it is possible to grasp the approximate value of the total positive electrode active material DBP absorption amount X (mL) by measuring the DBP absorption amount of the mixture of the positive electrode active material and the conductive material.

  On the other hand, in order to grasp the total negative electrode active material DBP absorption Y (mL) of the battery after the assembly of the nonaqueous secondary battery (which may be after the start of use of the battery), for example, the battery is disassembled. The negative electrode mixture is recovered, the negative electrode mixture is heated in an oxidizing atmosphere to volatilize and remove organic components (binder, etc.), and the DBP absorption amount Y (mL) for the heating residue (inorganic component) Should be measured. From the total positive electrode active material DBP absorption amount X (mL) and the total negative electrode active material DBP absorption amount Y (mL) thus obtained, the X / Y value of the battery can be estimated.

  Non-aqueous secondary batteries disclosed herein (typically lithium ion secondary batteries) have improved durability (eg, less resistance increase during storage) due to the use of BP-oxalato compounds, and Since it can be a high-performance battery having excellent initial characteristics (for example, one or both of initial efficiency and initial resistance), it can be used as a secondary battery for various applications. For example, as shown in FIG. 4, any non-aqueous secondary battery 100 disclosed herein can be suitably used as a power source for a vehicle driving motor (electric motor) mounted on a vehicle 1 such as an automobile. it can. Although the kind of vehicle 1 is not specifically limited, Typically, they are a hybrid vehicle, an electric vehicle, a fuel cell vehicle, etc. Such non-aqueous secondary battery 100 may be used alone, or may be used in the form of an assembled battery that is connected in series and / or in parallel.

Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to the specific examples.
≪Positive electrode active material≫
As the positive electrode active material in the following experiments, active material particles having a perforated hollow structure produced as follows were used.
Ion exchange water is put into a reaction tank set at a temperature of 40 ° C., and nitrogen gas is circulated while stirring to replace the ion exchange water with nitrogen, and oxygen gas (O ₂ ) concentration in the reaction tank is 2 Adjusted to 0.0% non-oxidizing atmosphere. Next, a 25% aqueous sodium hydroxide solution and 25% aqueous ammonia were added so that the pH measured on the basis of the liquid temperature of 25 ° C. was 12.5 and the NH ₄ ⁺ concentration in the liquid was 5 g / L.

  In nickel sulfate, cobalt sulfate, and manganese sulfate, the molar ratio of Ni: Co: Mn is 0.33: 0.33: 0.33, and the total molar concentration of these metal elements is 1.8 mol / L. A mixed aqueous solution was prepared by dissolving in water. By supplying this mixed aqueous solution, 25% NaOH aqueous solution and 25% aqueous ammonia into the reaction vessel at a constant rate, the reaction solution was controlled to pH 12.5 and ammonia concentration 5 g / L, while the NiCoMn was removed from the reaction solution. The composite hydroxide was crystallized (nucleation stage).

When 2 minutes and 30 seconds had elapsed from the start of the supply of the mixed aqueous solution, the supply of the 25% NaOH aqueous solution was stopped. The mixed aqueous solution and 25% aqueous ammonia were continuously supplied at a constant rate. After the pH of the reaction solution dropped to 11.6, the supply of 25% aqueous NaOH solution was resumed. Then, while controlling the reaction solution to pH 11.6 and the ammonia concentration described later, the operation of supplying the above mixed aqueous solution, 25% NaOH aqueous solution and 25% ammonia water was continued for 4 hours to grow NiCoMn composite hydroxide particles. (Particle growth stage). The product was then removed from the reaction vessel, washed with water and dried. In this manner, composite hydroxide particles having a composition represented by Ni _0.33 Co _0.33 Mn _0.33 (OH) _{2 + α} (where α is 0 ≦ α ≦ 0.5) were obtained. .

The composite hydroxide particles were heat-treated at 150 ° C. for 12 hours in an air atmosphere. Next, Li ₂ CO ₃ as the lithium source and the composite hydroxide particles are combined into the number of moles of lithium (M _Li ) and the total number of moles of Ni, Co and Mn constituting the composite hydroxide (M _Me ). And the mixture (M _Li : M _Me ) was 1.15: 1. This mixture was fired at 760 ° C. for 4 hours (first firing stage), and then fired at 950 ° C. for 10 hours (second firing stage). Thereafter, the fired product was crushed and sieved. In this manner, an active material particle sample having a composition represented by Li _1.15 Ni _0.33 Co _0.33 Mn _0.33 O ₂ was obtained.

  In the above active material particle sample preparation process, by adjusting the conditions of the reaction liquid used when preparing the composite hydroxide particles, more specifically, the ammonia concentration of the reaction liquid is adjusted to 1 to 15 g in the particle growth stage. By maintaining (controlling) each at a different concentration between 25 mL / mL, the DBP absorption amount x by the above-described method is 22 mL / 100 g (sample P1), 30 mL / 100 g (sample P2), and 35 mL / 100 g (sample P3), respectively. And 4 types of active material particles of 41.1 mL / 100 g (sample P4) were produced.

  When surface SEM observation was performed on the active material particles of these samples P1 to P4, each active material particle sample had a clear shell portion and a hollow portion, and the shell portion had several (per particle) It was confirmed that an average of one or more through-holes were formed, and the shell portion was densely sintered at portions other than the through-holes. When the average hardness of samples P1 to P4 was measured by the above method, it was confirmed that all were in the range of 0.5 MPa to 10 MPa. Further, the average particle diameters of the samples P1 to P4 were all in the range of 3 μm to 8 μm, and the particle porosity was in the range of 3% to 50%.

≪Negative electrode active material≫
As the negative electrode active material, graphite particles and carbon particles having a structure in which amorphous carbon was coated on the surfaces of the particles were used. Specifically, the amorphous carbon-coated carbon particles are made by attaching a pitch to the surface of natural graphite powder by a vapor phase method, firing at 1000 ° C. to 1300 ° C. for 10 hours in an inert atmosphere, and then sieving. The average particle size was adjusted. In the negative electrode active material sample preparation process, the average particle diameter (D50) of the natural graphite powder used is varied between 8 μm and 11 μm, and the coating amount of the pitch with respect to the mass of the graphite powder is 0% by mass to 6% by mass. By varying the range, the DBP absorption y by the above-described method was 34.3 mL / 100 g (sample Q1), 36.6 mL / 100 g (sample Q2), 50 mL / 100 g (sample Q3), and 60 mL / 100 g (sample), respectively. Q4) and 5 types of negative electrode active materials of 77.5 mL / 100 g (sample Q5) were prepared.

≪Production of evaluation battery≫
Samples P1 to P4 prepared above were used as the positive electrode active material, and samples Q1 to Q5 were used as the negative electrode active material to prepare evaluation batteries (Examples 1 to 14) having the structures shown in FIGS.
Positive electrode active material (from samples P1 to P4, those corresponding to DBP absorption x shown in Tables 1 to 3 were used), acetylene black (AB) as a conductive material, and PVDF as a binder Were mixed with NMP such that their mass ratio was 90: 8: 2 and NV was 50% to prepare a slurry-like composition. The above composition is 95 mm wide on both surfaces of an aluminum foil (positive electrode current collector) 32 having a thickness of 15 μm, a width of 115 mm, and a length of 3000 mm so that the total mass after drying is 12 mg / cm ^2. Applied. This was dried and pressed to produce a positive electrode sheet 30 having a positive electrode mixture layer 34 on both sides of the current collector 32.

The negative electrode active material prepared above (from samples Q1 to Q5, the one corresponding to the DBP absorption y shown in Tables 1 to 3 was used), SBR, and CMC had a mass ratio of 98: 1. 1 and mixed with ion-exchanged water so that NV was 45% to prepare a slurry-like composition. The above composition is 105 mm wide on both sides of a copper foil (negative electrode current collector) 42 having a thickness of 10 μm, a width of 120 mm, and a length of 3200 mm, and the total mass after drying is 7.5 mg / cm ^2. It was applied as follows. This was dried and pressed to produce a negative electrode sheet 40 having a negative electrode mixture layer 44 on both sides of the current collector 42.

  The positive electrode sheet 30 and the negative electrode sheet 40 were wound together with two porous polyethylene sheets 50 (thickness 20 μm), and formed into a flat shape to produce an electrode body 20. The positive electrode terminal 38 and the negative electrode terminal 48 were attached to the lid body 14, and these terminals 38 and 48 were welded to the positive electrode current collector 32 and the negative electrode current collector 42 exposed at the end of the electrode body 20, respectively. Thus, the electrode body 20 connected to the lid body 14 was accommodated in the inside of the opening portion 12 of the case 10, and the lid body 14 was welded to the opening portion 12 of the case 10.

A nonaqueous electrolytic solution 90 was injected from an electrolytic solution injection hole (not shown) provided in the lid 14. As the non-aqueous electrolyte 90, LiPF ₆ as a supporting salt was contained at a concentration of 1 mol / L (1 M) in a 1: 1: 1 volume ratio of EC, DMC, and EMC, and Table 1 3 containing lithium bis (oxalato) borate (LiBOB) at the concentration shown in FIG.

  Then, the said injection hole was plugged and the lithium ion secondary battery 100 for evaluation was constructed | assembled. Each test battery has about 32 mg of a positive electrode active material, about 30 mg of a negative electrode active material, and about 30 mL of a non-aqueous electrolyte.

  Next, the conditioning process, rated capacity measurement, and SOC adjustment performed for the evaluation test battery constructed as described above will be described in order.

<< conditioning >>
The conditioning process was performed according to the following procedures 1-2.
Procedure 1: A constant voltage of 1 C (1 C means a current value that discharges a fully charged battery to a discharge end voltage in 1 hour, sometimes called a discharge time rate). 4. Charge until it reaches 1V (CC charge), then pause for 5 minutes.
Procedure 2: After Procedure 1, charge with constant voltage charging (CV charging) for 1.5 hours and rest for 5 minutes.

≪Measurement of rated capacity≫
The rated capacity of the evaluation test battery was measured by the following procedures 1 to 3 at a temperature of 25 ° C. and a voltage range of 3.0 V to 4.1 V for the evaluation test battery after the conditioning step.
Procedure 1: After reaching 3.0 V by constant current discharge (CC discharge) of 1 C, discharge at constant voltage discharge for 2 hours (CV discharge), and then rest for 10 seconds.
Procedure 2: After reaching 4.1 V by constant current charging at 1 C, charge for 2.5 hours by constant voltage charging, and then rest for 10 seconds.
Procedure 3: After reaching 3.0 V by constant current discharge of 0.5 C, discharge at constant voltage discharge for 2 hours, and then stop for 10 seconds.
The discharge capacity (CCCV discharge capacity) in the discharge from the constant current discharge to the constant voltage discharge in the procedure 3 is defined as the rated capacity.

≪SOC adjustment≫
The SOC adjustment was performed by the following procedures 1 and 2 in a temperature environment of 25 ° C. after the conditioning process and the rated capacity measurement.
Procedure 1: Charging at a constant current of 3V to 1C to obtain a charged state (SOC 60%) of about 60% of the rated capacity. Here, “SOC” means State of Charge.
Procedure 2: When adjusting to SOC of 60% or more, after Procedure 1, charge at a constant voltage until a desired state of charge is reached.

  Next, a method for measuring “initial efficiency”, “initial resistance”, and “resistance after durability” and a method for calculating a resistance increase rate will be described in order for the battery for the evaluation test.

≪Initial efficiency≫
The total capacity charged (CC-CV charge) through procedure 1 and procedure 2 in the conditioning process is defined as initial charge capacity, and the total capacity discharged (CC-CV charge) in procedure 1 in the rated capacity measurement is defined as initial discharge capacity. To do. Then, the initial efficiency (%) was calculated by the following formula: (initial discharge capacity) / initial charge capacity) × 100;

≪Initial resistance≫
The evaluation battery adjusted to SOC 60% (charged state of about 60% of the rated capacity) was discharged for 10 seconds at a discharge rate of 7C in a measurement environment of −15 ° C. From the voltage drop at this time, the initial resistance value (10-second IV resistance value) at a low temperature (−15 ° C.) was obtained.

≪Resistivity increase rate by high temperature storage durability test≫
A battery having an SOC of 80% (charged state of about 80% of the rated capacity) was stored in an environment of 60 ° C. for 30 days. The 10-second IV resistance (resistance after durability) of the battery after storage was measured in the same manner as the initial resistance. Then, the rate of increase in resistance (%) was calculated according to the following formula: (resistance after durability) / (initial resistance) × 100;

  Tables 1 to 3 show the initial efficiency, initial resistance, post-endurance resistance, and resistance increase rate obtained for the evaluation batteries according to Examples 1 to 14. In these tables, the DBP absorption amounts x and y of the positive electrode active material and the negative electrode active material used for the preparation of each battery, the concentration of LiBOB in the used non-aqueous electrolyte, and the non-aqueous electrolyte injected into each battery The total molar quantity A of LiBOB contained (calculated from the LiBOB concentration and the amount of electrolyte used). The total positive electrode active material DBP absorption amount X and the total negative electrode active material DBP absorption amount Y (the above x, y, and Calculated from the masses of the positive electrode active material and the negative electrode active material contained in each battery.), Their ratio (X / Y), the ratio of the total molar quantity A of LiBOB to the total positive electrode active material DBP absorption amount X (A / X ) Is also shown.

  As shown in Table 1, among the evaluation batteries of Examples 1 to 6 manufactured using non-aqueous electrolytes having the same total LiBOB amount A (mmol), X / Y is 0.60 to 1.25. In Examples 1-4 in the range, the rate of increase in resistance was clearly smaller than Example 5 in which X / Y was less than 0.60. This is because, even in the case where the amount of LiBOB in the battery is the same, in the batteries according to Examples 1 to 4 where X / Y is large, more LiBOB is distributed to the positive electrode side. It is thought that was demonstrated. Moreover, it is considered that the initial efficiency of Examples 1 to 4 was higher than that of Example 5 because the amount of LiBOB distributed to the negative electrode side to reduce the initial efficiency was small. The initial resistance of the battery according to Example 6 was higher than that of Examples 1 to 4 because the value of X / Y was increased by using a negative electrode active material having a DBP absorption y that was too small. It is inferred that the area was insufficient and the battery reaction rate was restricted, which caused the initial resistance to increase.

  As shown in Table 2, the battery according to Example 8 using the positive electrode active material with the DBP absorption x being too small was clearly lower in initial efficiency than the batteries according to Examples 1 and 7. This is because, in the battery according to Example 8, X / Y is less than 0.60 (0.50 or less), so a large amount of LiBOB is distributed on the negative electrode side, and the initial efficiency is reduced due to the reductive decomposition of LiBOB. It is considered a thing.

  As shown in Table 3, the batteries according to Examples 1 and 9 to 12 in which A / X is in the range of 0.02 to 0.30 mmol / mL, the initial efficiency is low, the resistance increase rate is small, and good performance is obtained. Indicated. Example 13 in which A / X was too small had a higher resistance increase rate than Examples 1 and 9-12. This is because even if the distribution ratio of LiBOB to the positive electrode side is increased by setting X / Y to 0.60 or more, the total amount of LiBOB is too small, so the amount of LiBOB supplied per actual reaction area of the positive electrode is insufficient. Therefore, it is considered that a sufficient addition effect was not exhibited. In Example 14, the initial efficiency was low because even if the distribution ratio of LiBOB to the negative electrode side was decreased by increasing X / Y, if the total amount of LiBOB was too large, it was distributed to the negative electrode side even with a low distribution ratio. The absolute amount of LiBOB increases, and it is presumed that the initial efficiency was reduced by the reductive decomposition of LiBOB.

  As mentioned above, although this invention was demonstrated in detail, the said embodiment and Example are only illustrations and what changed and changed the above-mentioned specific example is contained in the invention disclosed here.

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Battery case 12 Opening part 14 Cover body 20 Winding electrode body 30 Positive electrode sheet (positive electrode)
32 Positive electrode current collector 34 Positive electrode mixture layer 38 Positive electrode terminal 40 Negative electrode sheet (negative electrode)
42 Anode current collector 44 Anode mixture layer 48 Anode terminal 50 Separator 90 Nonaqueous electrolyte 100 Lithium ion secondary battery (nonaqueous secondary battery)
610 Active material particles 612 Shell portion 614 Hollow portion 616 Through hole

Claims (9)

A non-aqueous electrolyte secondary battery,
It is constructed using a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte disposed in contact with both the positive electrode active material and the negative electrode active material,
As the non-aqueous electrolyte, a non-aqueous electrolyte containing an oxalato complex compound containing at least one of element B and element P, and a non-aqueous solvent is used.
The relationship between the DBP absorption amount X (mL) for the total amount of the positive electrode active material included in the battery and the DBP absorption amount Y (mL) for the total amount of the negative electrode active material included in the battery is expressed by the following formula. :
0.60 ≦ X / Y ≦ 1.25;
Satisfying the non-aqueous electrolyte secondary battery. The relationship between the total number of moles A (mmol) of the oxalato complex compound contained in the battery and the DBP absorption amount X (mL) for the total amount of the positive electrode active material contained in the battery is expressed by the following formula:
0.02 ≦ A / X (mmol / mL) ≦ 0.30;
The nonaqueous electrolyte secondary battery according to claim 1, wherein   The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the DBP absorption amount x (mL / 100g) per 100g of the positive electrode active material is 25mL / 100g or more.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein a DBP absorption amount y (mL / 100 g) per 100 g of the negative electrode active material is 35 to 75 mL / 100 g. The relationship between the DBP absorption amount x (mL) per 100 g of the positive electrode active material and the DBP absorption amount y (mL) per 100 g of the negative electrode active material is expressed by the following formula:
0.55 ≦ x / y ≦ 1.15;
The nonaqueous electrolyte secondary battery according to claim 1, wherein   The non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein the oxalato complex compound is lithium bis (oxalato) borate.   The non-aqueous electrolyte according to claim 1, wherein the positive electrode active material is a lithium transition metal oxide, and the negative electrode active material is a carbon material having a graphite structure at least in part. Secondary battery. A method of manufacturing a non-aqueous electrolyte secondary battery,
Preparing a positive electrode having a positive electrode active material and a negative electrode having a negative electrode active material, wherein the positive electrode and the negative electrode are DBP absorption amount X (mL) with respect to the total amount of the positive electrode active material possessed by the positive electrode; The relationship between the total amount of the negative electrode active material of the negative electrode and the DBP absorption amount Y (mL) is represented by the following formula:
0.60 ≦ X / Y ≦ 1.25;
Satisfy;
Providing a non-aqueous electrolyte containing an oxalato complex compound containing at least one of element B and element P and a non-aqueous solvent; and
Storing the positive electrode, the negative electrode, and the non-aqueous electrolyte in a container to construct a battery;
A method for producing a non-aqueous electrolyte secondary battery. Relationship between the total mole number A (mmol) of the oxalato complex compound contained in the non-aqueous electrolyte contained in the container and the DBP absorption amount X (mL) with respect to the total amount of the positive electrode active material contained in the battery But the following formula:
0.02 ≦ A / X (mmol / mL) ≦ 0.30;
The method of claim 8, wherein: