JP2015125833A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery which is arranged to be able to exhibit high battery characteristics and in which a preferred amount of a coating is formed on the surface of an active material of each of positive and negative electrodes.SOLUTION: A nonaqueous electrolyte secondary battery comprises: a positive electrode having a positive electrode active material; a negative electrode having a negative electrode active material; and a nonaqueous electrolyte. When incorporated in a battery, the nonaqueous electrolyte contains a sulfonic acid compound having a triple bond, a vinylene carbonate compound, and a phosphono acetic ester compound. The active material of each of the positive and negative electrodes has a coating. The coating of the positive electrode active material includes SOand SOwhich originate from the sulfonic acid compound by 3-10 μmol/m. The coating of the negative electrode active material includes: SOand SOoriginating from the sulfonic acid compound by 3-10 μmol/m; and COoriginating from the vinylene carbonate compound, the content of which is 2-7 times that of the SOand SO.

Description

  The present invention relates to a secondary battery (non-aqueous electrolyte secondary battery) provided with a non-aqueous electrolyte. Specifically, the present invention relates to the battery including a coating on the surfaces of the positive electrode active material and the negative electrode active material.

  In recent years, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries have been used as so-called portable power sources such as personal computers and portable terminals and power sources for driving vehicles. In particular, a lithium ion secondary battery that is lightweight and has a high energy density is preferably used as a high-output power source for driving electric vehicles, hybrid vehicles, and the like.

In such a non-aqueous electrolyte secondary battery, a part of the non-aqueous electrolyte is decomposed at the time of initial charge, and a film made of the decomposition product is formed on the surface of the negative electrode active material. Such a coating suppresses reductive decomposition of the nonaqueous electrolytic solution that accompanies subsequent charge and discharge, and improves the durability of the battery.
Patent documents 1 and 2 are mentioned as a technique relevant to this. For example, Patent Document 1 discloses that a non-aqueous electrolyte contains 0.01 to 10% by weight of a vinylene carbonate compound and 0.01 to 10% by weight of an alkyne compound as a film forming agent, thereby forming a strong film on the negative electrode. It is described that it can be formed and the cycle characteristics can be further improved (paragraph 0027 of Patent Document 1).

International Publication No. 2005/008829 International Publication 2012/141270

However, according to the study by the present inventors, when the amount of the film-forming agent is determined with respect to the whole non-aqueous electrolyte, design parameters (for example, battery capacity, the basis weight of the negative electrode active material layer, thickness, density, etc.) When it is difficult to properly cope with the change of the battery, in some cases, the coating on the surface of the negative electrode active material is insufficient and the durability is lowered, and in other cases, the coating is excessive and causes an increase in battery resistance. was there. Furthermore, according to the study by the present inventors, it may be preferable to provide a coating on the surface of the positive electrode active material as in the case of the negative electrode active material. For example, in a battery that is exposed to harsh conditions (for example, in a high temperature environment) for a long time, an oxidative decomposition reaction of the nonaqueous electrolytic solution may occur at the positive electrode. Alternatively, according to the study by the present inventors, a non-aqueous electrolyte (typically a supporting salt contained in the electrolyte, for example, LiPF ₆ ) reacts with moisture contained in the battery to react with an acid (eg, fluoride). Hydrogen fluoride (HF)) may be generated. Such an acid may accelerate elution of a constituent element (typically a transition metal element such as a manganese element) from the positive electrode active material, which may deteriorate the positive electrode active material or increase battery resistance.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide higher battery characteristics by providing a suitable amount of coating on the surfaces of the positive electrode active material and the negative electrode active material (for example, a battery). It is to provide a non-aqueous electrolyte secondary battery having low resistance and excellent cycle characteristics.

In order to solve the above problems, the present inventors first considered optimizing the coating amounts of the positive electrode active material and the negative electrode active material. Furthermore, it was considered to suppress the generation of “acid” that could cause deterioration of the positive electrode active material and increase in battery resistance. And after earnest examination, it came to contemplate the present invention.
That is, according to the invention disclosed herein, a positive electrode having a positive electrode active material made of a lithium composite metal oxide, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte are accommodated in a battery case. A water electrolyte secondary battery is provided. The non-aqueous electrolyte contains (1) a sulfonic acid compound having a triple bond, (2) a vinylene carbonate compound, and (3) a phosphonoacetate compound at the time of battery construction. The positive electrode active material and the negative electrode active material each have a coating. Coating the positive electrode active material, SO ₃ derived from the sulfonic acid compound ^- and _SO ^{4 2-a,} containing the above positive electrode active ratio of material surface area 1 m ² per 3 [mu] mol / ^{m 2} or more 10 .mu.mol / ^{m 2} or less. The coating of the negative electrode active material, SO ₃ derived from the sulfonic acid compound ^- a and _SO ^{4 2-,} contained in the negative electrode active ratio of material surface area 1 m ² per 3 [mu] mol / ^{m 2} or more 10 .mu.mol / ^{m 2} or less, and Further, CO ₃ ²⁻ derived from the vinylene carbonate compound is contained at a ratio of 2 μmol or more and 7 μmol or less with respect to 1 μmol of the SO ₃ ⁻ and SO ₄ ²⁻ .

By including the phosphonoacetic acid ester compound at the time of battery construction, the compound and a trace amount of water contained in the battery react to trap (capture) moisture in the structure of the compound. Specifically, the carboxylic acid ester group (—C (═O) —O—) of the phosphonoacetic acid ester compound is cleaved to cause a hydration reaction (addition reaction), and water molecules are taken into the structure of the compound. obtain. Thereby, reaction with a nonaqueous electrolyte and a water | moisture content can be prevented suitably, and generation | occurrence | production of an acid (for example, hydrogen fluoride (HF)) can be suppressed. Therefore, deterioration of the positive electrode active material (for example, elution of constituent elements) can be highly suppressed.
Moreover, the crystal structure of a positive electrode active material can be hold | maintained in a more stable state by providing the coating film derived from a sulfonic acid compound on the surface of a positive electrode active material. In addition, the oxidative decomposition of the nonaqueous electrolytic solution can be highly suppressed, and the formation of a high-resistance film (for example, lithium fluoride (LiF)) can be prevented.
Furthermore, by providing the surface of the negative electrode active material with a film derived from a sulfonic acid compound and a film derived from a vinylene carbonate compound, reductive decomposition of the non-aqueous electrolyte can be suppressed to a high degree, for example, long exposure to a high temperature environment. A high capacity maintenance rate can be maintained even if it is done.
As described above, the battery having such a configuration can stably exhibit high battery characteristics. For example, by reducing the acidity in the battery, it is possible to realize a nonaqueous electrolyte secondary battery that can exhibit energy density and output density over a long period of time.

In this specification, the amount (μmol / m ² ) of ions per 1 m ² of the specific surface area of the active material is the number of ions contained per unit area of the electrode measured by ion chromatography (IC: Ion Chromatography). A value obtained by dividing the amount (μmol / cm ² ) by the surface area (m ² / cm ² ) of the active material contained per unit area of the electrode. The method for quantifying the film using IC will be described in detail later. The surface area (m ² / cm ² ) of the active material contained per unit area of the electrode is the product of the basis weight (g / cm ² ) of the active material and the BET specific surface area (m ² / g) of the active material. Can be obtained. The BET specific surface area (m ² / g) is obtained by analyzing the adsorption amount measured by a gas adsorption method (constant capacity adsorption method) using nitrogen (N ₂ ) gas by the BET method (eg, BET one-point method). Can be obtained.

In a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, the coating film of the positive electrode active material comprises the SO ₃ ⁻ and SO ₄ ^{2− of} ₃ μmol / m per 1 m ² of the specific surface area of the positive electrode active material. ^{2 to} 8 μmol / m ² or less. Moreover, the coating film of the negative electrode active material contains the SO ₃ ⁻ and SO ₄ ²⁻ at 5 μmol / m ² or more and 10 μmol / m ² or less per 1 m ² of the specific surface area of the negative electrode active material. The amount of SO ₃ ⁻ and SO ₄ ²⁻ is greater in the negative electrode active material coating than in the positive electrode active material coating.
According to this aspect, it is possible to further suppress an increase in resistance accompanying the formation of the film, and to suppress the decomposition of the nonaqueous electrolytic solution at a high level. Therefore, the effect of the present invention can be realized at a high level.

In a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, the coating film of the negative electrode active material has a phosphonoacetate ion (RO ₂ —P (═O) —CH ₂ derived from the phosphonoacetate compound). -C (= O) -O ^-) which contained in the negative electrode active ratio of material surface area 1 m ² per 3 [mu] mol / ^{m 2} or more 12 [mu] mol / ^{m 2} or less.
According to the study by the present inventors, the phosphonoacetate compound in the form of trapping moisture can be deposited on the surface of the negative electrode active material by applying a voltage. Specifically, the carboxylate group (—C (═O) —O—) can be bonded to the surface of the negative electrode active material in a cleaved form. By adjusting the amount of phosphonoacetate ions contained in the coating within the above range, the effect of the present invention can be realized at a higher level.

In a preferred aspect of the non-aqueous electrolyte secondary battery disclosed herein, the lithium composite metal oxide contains manganese element (Mn).
In general, when the positive electrode active material contains a manganese element, elution of the manganese element from the positive electrode active material can be a problem under severe conditions (for example, in a high temperature environment). However, according to the technique disclosed here, the elution of the constituent elements from the positive electrode active material can be highly suppressed. Therefore, even when a transition metal composite oxide (typically lithium nickel cobalt manganese composite oxide) containing a large amount of manganese (typically containing about 30 mol% to 40 mol%) is used as the positive electrode active material, High durability (for example, high temperature storage characteristics and cycle characteristics) can be realized.

In a preferred aspect of the non-aqueous electrolyte secondary battery disclosed herein, the battery case includes a pressure-type current interruption mechanism (that is, a current interruption mechanism that operates when the battery internal pressure increases).
Generally, in a battery having a pressure type current interruption mechanism, if a large amount of gas is generated in the battery during normal use, the current interruption mechanism may malfunction or the battery case may be deformed. obtain. However, according to the technique disclosed here, the oxidation or reductive decomposition of the nonaqueous electrolytic solution can be highly suppressed, and the amount of gas generated during normal use can be suppressed to a small level. Therefore, the operability of the current interruption mechanism can be improved, and a highly reliable nonaqueous electrolyte secondary battery can be realized.

In a preferred embodiment of the nonaqueous electrolyte secondary battery disclosed herein, when the coating on the surface of the negative electrode active material is divided into two in the thickness direction, the components of the coating are different between the upper layer portion and the lower layer portion. . In the upper layer portion, the amount of the coating derived from the sulfonic acid compound and the vinylene carbonate compound is large, and in the lower layer portion, the amount of the coating derived from the phosphonoacetate compound is large.
According to the study by the present inventors, the sulfonic acid compound having a triple bond and the vinylene carbonate compound can form a mixed film on the surface of the negative electrode active material in a copolymerized form. Since such a mixed film is excellent in stability and durability, by having a large amount of the mixed film at the interface (that is, the upper layer part) with the non-aqueous electrolyte, the non-aqueous electrolyte is hardly decomposed even in a high temperature environment, for example. Stable performance can be demonstrated over a long period of time.

式（Ｉ）において、Ｒ^１は、炭素原子数１〜６のアルキル基、炭素原子数３〜６のシクロアルキル基、炭素原子数６〜１２のアリール基、または炭素原子数１〜６のパーフルオロアルキル基である。また、Ｒ^２，Ｒ^３，Ｒ^４，Ｒ^５は、それぞれ独立して、水素原子、炭素原子数１〜４のアルキル基である。
中間位置に三重結合を有するスルホン酸化合物を含むことで、正極活物質および負極活物質の表面に、好適な割合で良質な被膜を安定的に形成することができる。 In a preferred embodiment of the nonaqueous electrolyte secondary battery disclosed herein, the sulfonic acid compound is a compound represented by the following formula (I).

In the formula (I), R ¹ represents an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a par group having 1 to 6 carbon atoms. A fluoroalkyl group; R ² , R ³ , R ⁴ and R ⁵ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
By including a sulfonic acid compound having a triple bond at an intermediate position, a good-quality film can be stably formed at a suitable ratio on the surfaces of the positive electrode active material and the negative electrode active material.

In a preferred embodiment, R ¹ in the above formula (I) is a methyl group (CH ₃ ).
In another preferred embodiment, R ^{2 to} R ⁵ in the above formula (I) are all hydrogen atoms.
A preferred example of the sulfonic acid compound having a triple bond is 2-butyne-1,4-diol dimethanesulfonate.

式（ＩＩ）において、Ｒ^６，Ｒ^７は、それぞれ独立して、炭素原子数１〜６のアルキル基、炭素原子数３〜６のシクロアルキル基、炭素原子数２〜６のアルケニル基、炭素原子数３〜６のアルキニル基、炭素原子数１〜６のハロゲン化アルキル基、または炭素原子数６〜１２のアリール基である。 In a preferred embodiment of the nonaqueous electrolyte secondary battery disclosed herein, the phosphonoacetate compound is a compound represented by the following formula (II).

In the formula (II), R ⁶ and R ⁷ are each independently an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, carbon An alkynyl group having 3 to 6 atoms, a halogenated alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms.

In a preferred embodiment, R ⁶ in the above formula (II) is an ethyl group (CH ₂ CH ₃ ).
In another preferable embodiment, R ⁷ in the above formula (II) is a 2-propynyl group (CH ₂ CCH)).
A preferred example of the phosphonoacetate compound is 2-propynyl diethylphosphonoacetate.

式（ＩＩＩ）において、Ｒ^８，Ｒ^９は、それぞれ独立して、水素原子、炭素原子数１〜４のアルキル基である。 In a preferred embodiment of the nonaqueous electrolyte secondary battery disclosed herein, the vinylene carbonate compound is a compound represented by the following formula (III).

In formula (III), R ⁸ and R ⁹ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

In a preferred embodiment, R ⁸ and R ⁹ in the above formula (III) are both hydrogen atoms. That is, the vinylene carbonate compound is vinylene carbonate. By using vinylene carbonate, a polymerization reaction with a sulfonic acid compound having a triple bond is more likely to occur, and high charge / discharge efficiency can be realized. Therefore, the application effect of the present invention can be exhibited at a high level.

  As described above, the non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) disclosed herein can achieve high durability. For example, high energy density and high input / output characteristics can be maintained even when the initial characteristics are high and the initial characteristics are maintained in a high temperature environment. Furthermore, high reliability (overcharge tolerance) can be realized by providing a current interruption mechanism. Therefore, taking advantage of these features, applications that require high energy density, high output density, or high durability and reliability in a wide range of temperatures (for example, power sources for driving motors mounted on vehicles (for driving) It can be suitably used for power supply)).

It is a longitudinal cross-sectional view which shows typically the nonaqueous electrolyte secondary battery which concerns on one Embodiment. It is a schematic diagram which shows the structure of the wound electrode body which concerns on one Embodiment. It is a graph which shows the relationship between the quantity of the phosphono acetate ion in a film, and a high temperature storage durability characteristic (capacity maintenance rate and IV resistance increase rate).

  Hereinafter, preferred embodiments of the present invention will be described. Matters necessary for the implementation of the present invention other than matters specifically mentioned in the present specification 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 non-aqueous electrolyte secondary battery disclosed herein has a configuration in which a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte are housed in a battery case. Hereinafter, each component will be described in order.

≪Battery case≫
The battery case is a container that accommodates a positive electrode, a negative electrode, and a non-aqueous electrolyte. The shape of the battery case (outer shape of the container) can be, for example, a circle (cylindrical shape, coin shape, button shape), hexahedron shape (cuboid shape, cube shape), bag shape, and a shape obtained by processing and deforming them. . As the material of the battery case, a metal material such as aluminum or steel; a resin material such as polyphenylene sulfide resin or polyimide resin can be used. Among these, relatively light metals (for example, aluminum and aluminum alloys) can be preferably used for the purpose of improving heat dissipation and increasing energy density.
In a preferred embodiment disclosed herein, the battery case is provided with a pressure type current interruption device (CID: Current Interrupt Device) that operates according to an increase in the internal pressure of the battery case. In general, a non-aqueous electrolyte secondary battery is used in a state where the voltage is controlled so as to be within a predetermined region (for example, 3.0 V or more and 4.2 V or less). As a result, overcharging may occur over a predetermined voltage. When the battery is overcharged, non-aqueous electrolyte components (for example, non-aqueous solvents and gas generating agents) are electrolyzed to generate gas. The pressure-type current interruption mechanism cuts off the charging current to the battery and stops the progress of overcharge when the internal pressure of the battery case exceeds a predetermined level by this gas. According to the technology disclosed herein, the amount of gas generated during normal use can be suppressed, and thus the safety mechanism can be operated accurately only during overcharge. Therefore, malfunction or the like hardly occurs, and the reliability (overcharge resistance) against overcharge can be further improved.

≪Positive electrode≫
The positive electrode is not particularly limited as long as it includes the positive electrode active material, but typically, the positive electrode active material layer containing the positive electrode active material is fixed on the positive electrode current collector.
As the positive electrode current collector, a conductive member made of a metal having good conductivity (for example, aluminum, nickel, titanium, etc.) can be suitably used.

The positive electrode active material layer contains at least a positive electrode active material. As the positive electrode active material, one or more kinds of various materials known to be usable as the positive electrode active material of the non-aqueous electrolyte secondary battery can be employed. Preferable examples include layered and spinel-based lithium composite metal oxides (for example, LiNiO ₂ , LiCoO ₂ , LiMn ₂ O ₄ , LiFeO ₂ , LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiNi _{0 .5} Mn _1.5 O ₄ , LiCrMnO ₄ , LiFePO _4, etc.). Among these, from the viewpoint of thermal stability and energy density, a lithium nickel cobalt manganese composite oxide having a layered structure (typically a layered rock salt structure) containing Li, Ni, Co and Mn as constituent elements is preferably used. Can do.
In general, in a complex oxide containing a transition metal element (especially a manganese element), elution of constituent elements may be accelerated by an acid (for example, hydrogen fluoride) generated by hydrolysis of a supporting salt, for example. However, according to the technique disclosed here, elution of such constituent elements can be prevented, and the crystal structure of the positive electrode active material can be maintained in a more stable state. Therefore, for example, it contains a large amount of manganese element that easily elutes in a high temperature environment (for example, when the total of nickel, cobalt, and manganese in the lithium nickel cobalt manganese composite oxide is 100 mol%, the proportion of manganese is 30 mol% to High battery performance can be stably realized over a long period of time.

  Here, the lithium nickel cobalt manganese composite oxide is an oxide containing only Li, Ni, Co and Mn as constituent metal elements, and at least one other metal element other than Li, Ni, Co and Mn. It is meant to include oxides containing (ie, transition metal elements and / or typical metal elements other than Li, Ni, Co and Mn). Such metal elements include magnesium (Mg), calcium (Ca), strontium (Sr), titanium (Ti), zirconium (Zr), vanadium (V), niobium (Nb), chromium (Cr), molybdenum (Mo), Tungsten (W), iron (Fe), rhodium (Rh), palladium (Pb), platinum (Pt), copper (Cu), zinc (Zn), boron (B), aluminum (Al), gallium (Ga), It may be one or more elements of indium (In), tin (Sn), lanthanum (La), and cerium (Ce). The addition amount (blending amount) of these metal elements is not particularly limited, but is usually 0.01 mol% to 5 mol% (for example, 0.05 mol% to 2 mol%, typically 0.1 mol% to 0.8 mol%). possible. By setting the addition amount as described above, further excellent battery characteristics (for example, high energy density) can be realized.

The properties of the positive electrode active material are not particularly limited, but are typically in the form of particles or powder. The average particle diameter of the particulate positive electrode active material may be 20 μm or less (typically 1 μm to 20 μm, for example, 5 μm to 15 μm). Further, the BET specific surface area is 0.1 m ² / g or more (typically 0.7 m ² / g or more, for example 0.8 m ² / g or more), and 5 m ² / g or less (typically 1 ³ m ² / g or less, for example 1.2 m ² / g or less).
The positive electrode active material satisfying one or two of the above properties has high battery characteristics (for example, high input / output characteristics) because a reaction field of charge carriers is widely ensured even when a film is formed. It can be demonstrated. Furthermore, during overcharge, the components of the nonaqueous electrolyte (for example, nonaqueous solvents and film forming agents) can be rapidly oxidatively decomposed, and the current interrupting mechanism can be activated at the initial stage of overcharge starting from this. .
In the present specification, the “average particle size” means a particle size distribution corresponding to 50% cumulative from the fine particle side in a volume-based particle size distribution measured by a particle size distribution measurement based on a general laser diffraction / light scattering method. (D ₅₀ particle diameter, also called median diameter).

In the technique disclosed herein, a film is formed on the surface of the positive electrode active material. In the coating, ₃ ^μmol to 10 ^{μmol of} SO ₃ ⁻ and SO ₄ ²⁻ derived from the sulfonic acid compound are contained per unit specific surface area (1 m ² ) of the positive electrode active material. The film derived from the sulfonic acid compound typically has a form containing a sulfur (S) atom-containing group (for example, a sulfonyl group or a sulfonyloxy group) and a charge carrier. Since the coating containing sulfur atoms is excellent in thermal stability, the amount of SO ₃ ⁻ and SO ₄ ²⁻ contained in the coating is ₃ μmol / m ² or more (typically 4 μmol / m ² or more, for example, 5 μmol / m ² or more), the coating film can be maintained in a stable state even in a high temperature environment, and excellent durability can be realized.
In general, the fluorine anion (F ⁻ ) generated by the reaction between a small amount of water contained in the battery and the non-aqueous electrolyte is negatively charged and is therefore attracted to the positive electrode side. Then, it can be oxidized and decomposed on the surface of the positive electrode (for example, the surface of the positive electrode active material) to form lithium fluoride (LiF) and be deposited on the positive electrode active material. Such a coating serves as a resistance component, which may increase internal resistance and decrease durability. However, the coating film containing the sulfur atom-containing group has many unpaired electron pairs (lawn pairs) and has a bulky structure. For this reason, it can suppress that hydrogen fluoride (specifically fluorine anion) approaches by using an electrostatic interaction and / or a steric hindrance by providing the film concerning a positive electrode. Therefore, it is possible to prevent lithium fluoride having high resistance from being generated.
In addition, the SO ₃ contained in the in the coating ^- a and _SO ⁴ amount of ^2-10 .mu.mol / ^{m 2} or less (typically 8 [mu] mol / ^{m 2} or less, for example 6μmol / ^{m 2} or less) by the above The reaction field of the charge carrier (lithium ion in the case of a lithium ion secondary battery) can be suitably ensured while sufficiently exhibiting the effect. For this reason, high battery performance can be realized stably, and the effects of the present invention can be exhibited at a high level.

The “amount of SO ₃ ⁻ and SO ₄ ²⁻ per 1 m ² of the specific surface area of the positive electrode active material (μmol / m ² )” is the SO per unit area of the electrode measured by ion chromatography (IC). ₃ ^- and _SO ^{4 2-amount} of (μmol / cm ^2), can be determined by dividing the surface area of the positive electrode active material contained per unit area of the electrode ^{(m 2} / cm 2).
Specifically, first, the positive electrode (positive electrode active material layer) taken out by disassembling the battery is immersed in an appropriate solvent (for example, EMC), and then cut into an appropriate size to collect a measurement sample. Next, by immersing the measurement sample in a 50% acetonitrile (CH ₃ CN) aqueous solution for a predetermined time (for example, about 1 to 30 minutes), the film components (SO ₃ ⁻ , SO ₄ ²⁻ ) to be measured are measured. ) In a solvent. This solution is subjected to IC measurement, and the content (μmol) of ions to be measured is quantified from the obtained results. Next, the SO ₃ ⁻ and SO ₄ ²⁻ quantitative values (μmol) are summed and divided by the area (cm ² ) of the positive electrode active material layer subjected to the measurement, thereby obtaining SO ₃ per unit area of the measurement sample. ^- and _SO ^{4 2-of} determining the amount (μmol / cm ^2). Then, by dividing this value by the product of the basis weight (g / cm ² ) of the positive electrode active material and the BET specific surface area (m ² / g) of the positive electrode active material, “per specific surface area 1 m ^{2 of the} positive electrode active material” Of SO ₃ ⁻ and SO ₄ ²⁻ ”.

  In addition, although the case where IC was used was illustrated above as a technique for measuring the coating amount, the present invention is not limited to this. For example, a conventionally known inductively coupled plasma-atomic emission spectroscopy (ICP-AES) ) And X-ray absorption fine structure analysis method (XAFS: X-ray Absorption Fine Structure).

  For the positive electrode active material layer, in addition to the positive electrode active material, one or more materials that can be used as components of the positive electrode active material layer in a general non-aqueous electrolyte secondary battery are used as necessary. May be contained. Examples of such a material include a conductive material and a binder. As the conductive material, for example, carbon materials such as various carbon blacks (for example, acetylene black and ketjen black), activated carbon, graphite, and carbon fiber can be suitably used. As the binder, for example, a halogenated vinyl resin such as polyvinylidene fluoride (PVdF), or a polyalkylene oxide such as polyethylene oxide (PEO) can be preferably used. In addition, various additives (for example, an inorganic compound that generates gas during overcharge, a dispersant, a thickener, and the like) can be included as long as the effects of the present invention are not significantly impaired.

  The proportion of the positive electrode active material in the entire positive electrode active material layer is suitably about 60% by mass or more (typically 60% by mass to 99% by mass), and usually about 70% by mass to 95% by mass. It is preferable that In the case of using a conductive material, the ratio of the conductive material in the entire positive electrode active material layer can be, for example, about 2% by mass to 20% by mass, and usually about 3% by mass to 10% by mass is preferable. . When using a binder, the ratio of the binder to the whole positive electrode active material layer can be, for example, about 0.5% by mass to 10% by mass, and usually about 1% by mass to 5% by mass is preferable. .

The mass (weight per unit area) of the positive electrode active material layer provided per unit area of the positive electrode current collector is 3 mg / cm ² or more per side of the positive electrode current collector (for example, 5 mg / cm ² or more) from the viewpoint of securing battery capacity. , Typically 7 mg / cm ² or more). Further, from the viewpoint of securing input / output characteristics, it can be set to 100 mg / cm ² or less (for example, 70 mg / cm ² or less, typically 50 mg / cm ² or less) per side of the positive electrode current collector.
The average thickness per one side of the positive electrode active material layer is, for example, 20 μm or more (typically 40 μm or more, preferably 50 μm or more), and can be 100 μm or less (typically 80 μm or less). The density of the positive electrode active material layer is, for example, 1 g / cm ³ or more (typically 1.5 g / cm ³ or more) and 4 g / cm ³ or less (eg, 3.5 g / cm ³ or less). obtain. The porosity (porosity) of the positive electrode active material layer is, for example, 10% by volume or more (typically 20% by volume or more) and 50% by volume or less (typically 40% by volume or less). possible.
By satisfying one or more of the above properties, an appropriate void can be maintained in the positive electrode active material layer, and the nonaqueous electrolyte can be sufficiently infiltrated. Therefore, a wide reaction field with the charge carrier can be secured, and high input / output characteristics can be exhibited during normal use. In addition, a large amount of gas can be generated quickly during overcharging, and the current interrupting mechanism can be operated accurately with this as a starting point. In addition, the conductivity in the positive electrode active material layer can be kept good, and an increase in resistance can be suppressed. Furthermore, the mechanical strength (shape retention) of the positive electrode active material layer can be suitably ensured, and good cycle characteristics can be realized.

Incidentally, the "porosity" in the present specification, multiplied by 100 and dividing the total pore volume obtained by the measurement of the mercury porosimeter a (cm ³⁾ in the apparent volume of the active material layer (cm ³⁾ value Say. The apparent volume can be calculated by the product of the area (cm ² ) and the thickness (cm) in plan view. Specifically, for example, the positive electrode to be measured is first cut into a square or a rectangle with a punching machine or a cutter. Next, the area (cm ² ) and the thickness (cm) of the cut-out sample in the plan view of the positive electrode active material layer are measured, and the apparent volume is calculated by multiplying these values. The thickness can be measured by, for example, a micrometer or a thickness meter (for example, a rotary caliper meter).

≪Negative electrode≫
The negative electrode is not particularly limited as long as the negative electrode active material is provided, but typically, the negative electrode active material layer containing the negative electrode active material is fixed on the negative electrode current collector.
As the negative electrode current collector, a conductive member made of a metal having good conductivity (for example, copper, nickel, titanium, stainless steel, etc.) can be suitably used.

  The negative electrode active material layer contains at least a negative electrode active material. As the negative electrode active material, one kind or two or more kinds of various materials known to be usable as the negative electrode active material of the non-aqueous electrolyte secondary battery can be adopted. Preferable examples include carbon materials such as graphite (graphite), non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), carbon nanotubes, and those having a combination of these. Among these, from the viewpoint of energy density, graphite-based materials such as natural graphite (graphite) and artificial graphite can be preferably used.

The properties of the negative electrode active material are not particularly limited, but are typically in the form of particles or powder. The average particle size of the particulate negative electrode active material can be 50 μm or less (typically 20 μm or less, for example, 1 μm to 20 μm, preferably 5 μm to 15 μm). The BET specific surface area is 1 m ² / g or more (typically 2.5 m ² / g or more, for example, 2.8 m ² / g or more), and 10 m ² / g or less (typically 3.5 m ² / g or less, for example, 3.4 m ² / g or less).
The negative electrode active material satisfying one or two of the above properties has high battery characteristics (for example, high input / output characteristics) because a reaction field of charge carriers is widely secured even when a film is formed. It can be demonstrated.

The shape of the negative electrode active material having the above properties can typically have shape anisotropy, and can be, for example, a scale shape, a flat plate shape, or the like. Alternatively, it may be a spheroidized graphite obtained by applying stress to the flaky graphite (so-called spheroidized graphite).
In general, graphite has functional groups with high reactive activity such as hydroxyl groups and carboxyl groups at the end (edge surface) of the hexagonal network structure, and the edge surface reacts with a non-aqueous electrolyte to reduce the capacity of the battery. And increase resistance. Since spheroidized graphite has a curved structure with its highly reactive edge surface folded, the ratio of the edge surface is relatively small, thereby reducing the reactivity with the non-aqueous electrolyte relatively. Can be suppressed. Further, the orientation of the hexagonal network structure is homogenized by spheroidization, and for example, the conductivity in the thickness direction of the negative electrode active material layer can be improved. Therefore, irreversible capacity and resistance can be reduced by using spheroidized graphite, and even higher battery characteristics can be realized.

In the technique disclosed herein, a film is formed on the surface of the negative electrode active material. In the coating, _{3 to 10} ^{μmol of} SO ₃ ⁻ and SO ₄ ²⁻ derived from the sulfonic acid compound are contained per unit specific surface area (1 m ² ) of the negative electrode active material. Further, CO ₃ ²⁻ derived from the vinylene carbonate compound is contained in the coating, and the content ratio of the CO ₃ ²⁻ is ² μmol to 7 μmol with respect to 1 μmol of SO ₃ ⁻ and SO ₄ ^2−. It is. The film formed on the surface of the negative electrode active material typically has a form in which the triple bond site of the sulfonic acid compound and the double bond site of the vinylene carbonate compound are bonded to each other, and both compounds are copolymerized. For example, it is a form including an S atom-containing group (for example, a sulfonyl group or a sulfonyloxy group), a C atom-containing group (for example, a carbonyl group or a carboxylate group), and a charge carrier.
In general, in a battery having a carbon material (typically a graphite-based material) in a negative electrode, when charge and discharge are repeated, components of the non-aqueous electrolyte (for example, non-aqueous solvent and supporting salt) are gradually decomposed, and the energy density is increased. It can be reduced. However, the coating film is stable by including a component (CO ₃ ²⁻ ) derived from a vinylene carbonate compound, and has low resistance by including a component (SO ₃ ⁻ and SO ₄ ²⁻ ) derived from a sulfonic acid compound. . Therefore, there is little increase in resistance accompanying the film formation, and reductive decomposition of the non-aqueous electrolyte can be suppressed over a long period of time.
In addition, the amount of SO ₃ ⁻ and SO ₄ ²⁻ contained in the coating is ₃ μmol / m ^{2 to} 10 μmol / m ² (preferably SO ₃ ⁻ and SO ₄ ² included in the coating on the surface of the positive electrode active material). ^- more than the amount, for example, ^{5μmol / m 2 ~8μmol / m 2} ) and was, and, a _CO ^{3 2-} the amount included in the above in the coating the SO ₃ ^- against and _SO ^{4 2-amount} 1μmol By setting the ratio of 2 μmol to 7 μmol (preferably 3 μmol to 6 μmol, for example, 5 μmol to 6 μmol), the reaction field of the charge carrier can be suitably ensured while sufficiently exhibiting the above effects. For this reason, high battery performance can be realized stably, and the effects of the present invention can be exhibited at a high level.

The “amount of SO ₃ ⁻ and SO ₄ ²⁻ per 1 m ² of specific surface area of the negative electrode active material (μmol / m ² )” is the SO per unit area of the electrode measured by ion chromatography (IC). ₃ ^- and _SO ^{4 2-amount} of (μmol / cm ^2), can be determined by dividing the surface area of the negative electrode active material contained per unit area of the electrode ^{(m 2} / cm 2). The amounts of SO ₃ ⁻ and SO ₄ ²⁻ can be obtained by the same analysis method as that for the positive electrode active material.

Further, "SO ₃ ^- and _CO ^{3 2-} in the amount relative to _SO ^{4 2-quantity} 1μmol" is, _CO ^{3 2-} in the amount (μmol / cm ²⁾ the SO ₃ is measured by ion chromatography (IC) ^- and it can be determined by dividing the _SO ⁴ amount of ^{2- (μmol} / cm ^2). The amount of CO ₃ ²⁻ contained in the coating can be determined as follows.
Specifically, first, the negative electrode (negative electrode active material layer) taken out by disassembling the battery is immersed in an appropriate solvent (for example, EMC), and then cut into an appropriate size to collect a measurement sample. Next, the coating component (CO ₃ ²⁻ ) to be measured is extracted into water by immersing the measurement sample in ion-exchanged water for a predetermined time (for example, about 1 to 30 minutes). This solution is subjected to IC measurement, and the content (μmol) of ions to be measured is quantified from the obtained results. Next, by dividing the obtained measurement value (μmol) by the area (cm ² ) of the negative electrode active material layer subjected to the measurement, the amount of CO ₃ ²⁻ per unit area of the measurement sample (μmol / cm ^2). ) Then, by dividing this value by the amount of SO ₃ ⁻ and SO ₄ ²⁻ per unit area of the measurement sample (μmol / cm ² ), the existence ratio of these ions (that is, the mixing ratio in the mixed film). Can be requested.

In a preferred embodiment disclosed herein, phosphonoacetate ions derived from the phosphonoacetate compound are further contained in the coating film of the negative electrode active material at 3 μmol to 12 μmol per unit specific surface area (1 m ² ) of the negative electrode active material. Contained. Thereby, the effect of the present invention can be exhibited at a higher level.
The “amount of phosphonoacetate ions per 1 m ² of specific surface area of the negative electrode active material (μmol / m ² )” is the amount of phosphonoacetate ions (μmol / cm ² ) measured by ion chromatography (IC). It can be determined by dividing by the surface area (m ² / cm ² ) of the negative electrode active material contained per unit area of the electrode.
Specifically, first, the negative electrode (negative electrode active material layer) taken out by disassembling the battery is immersed in an appropriate solvent (for example, EMC), and then cut into an appropriate size to collect a measurement sample. Next, by immersing the measurement sample in ion-exchanged water for a predetermined time (for example, about 1 to 30 minutes), the coating component (RO ₂ -P (= O) -CH ₂ -C (= O) -O ^-) to extract the water. This solution is subjected to IC measurement, and the content (μmol) of ions to be measured is quantified from the obtained results. Next, the obtained measured value (μmol) is divided by the area (cm ² ) of the negative electrode active material layer subjected to the measurement, whereby RO ₂ —P (═O) —CH ₂ per unit area of the measurement sample. The amount (μmol / cm ² ) of —C (═O) —O 2 ^— is determined. Then, by dividing this value by the product of the basis weight (g / cm ² ) of the negative electrode active material and the BET specific surface area (m ² / g) of the negative electrode active material, “per specific surface area 1 m ^{2 of the} negative electrode active material” The amount of phosphonoacetate ions "can be determined.

In another preferred embodiment, when the coating on the surface of the negative electrode active material is divided into two in the thickness direction, the components of the coating are different between the upper layer portion and the lower layer portion. In the upper layer portion, the amount of the film derived from the sulfonic acid compound and the vinylene carbonate compound is large, and in the lower layer portion, the amount of the film derived from the phosphonoacetate compound is large. That is, the amount of the SO ₃ ⁻ and SO ₄ ²⁻ and the CO ₃ ²⁻ is large in the upper layer portion, and the amount of the phosphonoacetate ion can be increased in the lower layer portion.
According to the study by the present inventors, depending on the relationship of the reduction potential of the film forming agent, the charging conditions at the time of the initial charge, etc., the phosphonoacetic acid ester compound is preferentially reduced and decomposed. It may be formed on the surface of the negative electrode active material. In addition, such a film may typically be in a form in which water molecules are trapped. Then, the sulfonic acid compound and vinylene carbonate compound having a triple bond are reduced and decomposed, and a mixed film derived from the sulfonic acid compound and vinylene carbonate compound is typically formed on the film derived from the phosphonoacetate compound. obtain. Thereby, the film excellent in thermal stability and durability can be realized. For example, the non-aqueous electrolyte is hardly decomposed even in a high temperature environment, and stable battery performance can be exhibited over a long period of time.

In addition, the magnitude relationship of the component contained in each area | region of the upper layer part and lower layer part when a film is divided into the thickness direction is, for example, a scanning electron microscope (SEM: Scanning Electron Microscope) -energy dispersive X-ray spectroscopy ( This can be confirmed relatively easily by EDX (Energy Dispersive X-ray Spectroscopy).
Specifically, the negative electrode provided with the negative electrode active material layer is first removed from the battery case and separated from other members. Next, the negative electrode is washed with a suitable solvent (for example, EMC) to remove the supporting salt and the like. Next, a cross-section is performed on the negative electrode by cross-section polisher, and this cross-section is observed with an SEM. The obtained SEM observation image is analyzed by EDX (for example, mapping with an element peculiar to a phosphonoacetate compound (for example, phosphorus (P)) or an element peculiar to a sulfonic acid compound (for example, sulfur (S))) Then, the analysis image of the upper layer part (surface vicinity area) and the analysis image of the lower layer part (current collector vicinity area) are compared. Thereby, the segregation degree (magnitude relation of contained elements) of the coating component contained in the upper layer part and the lower layer part can be grasped.

  In addition to the above-described negative electrode active material, the negative electrode active material layer may contain one or more materials that can be used as components of the negative electrode active material layer in a general non-aqueous electrolyte secondary battery as necessary. May be contained. Examples of such materials include binders and various additives. As the binder, for example, a polymer material such as styrene butadiene rubber (SBR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), or the like can be suitably used. In addition, various additives such as a thickener, a dispersant, and a conductive material can be used as appropriate. For example, carboxymethylcellulose (CMC) or methylcellulose (MC) can be suitably used as the thickener.

  The proportion of the negative electrode active material in the entire negative electrode active material layer is suitably about 50% by mass or more, and is usually 90% by mass to 99% by mass (eg, 95% by mass to 99% by mass). preferable. When using a binder, the ratio of the binder to the whole negative electrode active material layer can be, for example, about 1% by mass to 10% by mass, and usually about 1% by mass to 5% by mass is preferable. When using a thickener, the ratio of the thickener to the whole negative electrode active material layer can be, for example, about 1% by mass to 10% by mass, and usually about 1% by mass to 5% by mass. Is preferred.

The mass (weight per unit area) of the negative electrode active material layer provided per unit area of the negative electrode current collector is 5 mg / cm ^{2 to} 20 mg / cm ² (typically 7 mg / cm ^{2 to} 15 mg) per one side of the negative electrode current collector. / Cm ² ).
The thickness per one side of the negative electrode active material layer is, for example, 40 μm or more (typically 50 μm or more), and can be 100 μm or less (typically 80 μm or less). Further, the density of the negative electrode active material layer is, for example, 0.5 g / cm ³ or more (typically 1 g / cm ³ or more) and 2 g / cm ³ or less (typically 1.5 g / cm ³ or less). ). Further, the porosity of the negative electrode active material layer is, for example, 5% by volume or more (typically 35% by volume or more) and 50% by volume or less.
By satisfying one or more of the above properties, the interface with the non-aqueous electrolyte can be suitably maintained, and both durability (cycle characteristics) and output characteristics are compatible at a high level during normal use. Can do. In addition, hydrogen ions generated at the positive electrode can be suitably reduced during overcharge, and a large amount of gas can be generated quickly.

≪Separator≫
In the non-aqueous electrolyte secondary battery disclosed herein, a separator is typically interposed between the positive and negative electrodes. Any separator may be used as long as it insulates the positive electrode active material layer and the negative electrode active material layer and has a function of holding a nonaqueous electrolyte and a shutdown function. Preferable examples include porous resin sheets (films) made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Among them, a polyolefin-based porous resin sheet (for example, PE or PP) has a shutdown temperature of 80 to 140 ° C. (typically 110 to 140 ° C., for example, 120 to 135 ° C.) and a heat resistant temperature of the battery ( Typically, it is sufficiently lower than about 200 ° C.), so that the shutdown function can be exhibited at an appropriate timing.

  Although the properties of the separator are not particularly limited, for example, the thickness is usually 10 μm or more (typically 15 μm or more, for example, 17 μm or more) and 40 μm or less (typically 30 μm or less, for example, 25 μm or less). When the thickness of the separator is within the above range, the ion permeability is further improved, and an internal short circuit (separator film breakage) is less likely to occur even when foreign matter is mixed in the battery. The separator can have a porosity (porosity) of about 20% to 90% by volume (typically 30% to 80% by volume, preferably 40% to 60% by volume).

  The separator may have a single layer structure, or may have a structure in which two or more porous resin sheets having different materials and properties (thickness, porosity, etc.) are laminated. As a multilayer structure, for example, a separator having a three-layer structure (that is, a three-layer structure of PP / PE / PP) in which a polypropylene (PP) layer is laminated on both sides of a polyethylene (PE) layer can be suitably used. Further, the separator may be a heat-resistant separator having a porous heat-resistant layer on one side or both sides (typically one side) of the porous sheet. This heat-resistant layer can be, for example, a layer containing an inorganic filler and a binder. As the inorganic filler, for example, alumina, boehmite, silica, titania, calcia, magnesia, zirconia, boron nitride, aluminum nitride and the like can be preferably used. The average thickness of the heat-resistant layer can be, for example, about 1 μm to 10 μm. According to this form, the fine short circuit of positive and negative electrodes is highly suppressed, and further excellent durability (for example, high temperature storage durability characteristics) can be realized.

≪Nonaqueous electrolyte≫
The non-aqueous electrolyte of the non-aqueous electrolyte secondary battery disclosed herein includes at least a supporting salt in the non-aqueous solvent. The non-aqueous electrolyte is in a liquid state at normal temperature (for example, 25 ° C.), and in a preferred embodiment, the non-aqueous electrolyte is always in a liquid state in a battery use environment (for example, in a temperature environment of 0 ° C. to 60 ° C.).
As the non-aqueous solvent, organic solvents such as various carbonates, ethers, esters, nitriles, sulfones, and lactones used in the electrolyte of general non-aqueous electrolyte secondary batteries can be used. . Specific examples include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and the like. Such a non-aqueous solvent can be used individually by 1 type or in combination of 2 or more types as appropriate. Among these, EC having a high relative dielectric constant, DMC and EMC having a high oxidation potential (wide potential window) can be preferably used.
For example, one or more carbonates are included as the non-aqueous solvent, and the total volume of these carbonates is 60% by volume or more (more preferably 75% by volume or more, more preferably 90% by volume) of the total volume of the non-aqueous solvent. % Or more and may be substantially 100% by volume).

The supporting salt is the same as that of a general non-aqueous electrolyte secondary battery as long as it contains charge carrier ions (for example, lithium ions, sodium ions, magnesium ions, etc., lithium ions in lithium ion secondary batteries). Can be appropriately selected and used. For example, when the charge carrier ions are lithium ions, lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li (CF ₃ SO ₂ ) ₂ N, LiCF ₃ SO ₃ are exemplified. Such a supporting salt can be used singly or in combination of two or more. LiPF ₆ may be mentioned as particularly preferred support salt.
The concentration of the supporting salt is preferably adjusted to be 0.7 mol / L to 1.3 mol / L with respect to the entire nonaqueous electrolytic solution.

  The non-aqueous electrolyte of the non-aqueous electrolyte secondary battery disclosed herein contains a sulfonic acid compound having a triple bond, a vinylene carbonate compound, and a phosphonoacetate compound at the time of battery construction. As described above, these compounds typically react with moisture in the battery after the battery is built (assembled), or are decomposed in the initial charge, and a high-quality film is formed on the surface of the positive electrode active material and / or the negative electrode active material. Can be combined (deposited). Therefore, it is necessary that these compounds contained in the non-aqueous electrolyte at the time of battery construction remain in the non-aqueous electrolyte after charge / discharge (typically after the initial charge, for example, after conditioning). do not do.

As the sulfonic acid compound having a triple bond, sulfonic acid and its derivatives can be used, and those prepared by a known method or those obtained by purchasing a commercially available product are not particularly limited, but one or more Can be used. A typical example is an organic sulfonic acid compound having at least one —SO ₃ R group and a carbon skeleton having a triple bond. For example, an aliphatic sulfonic acid represented by the above formula (I) can be preferably used.

In the formula (I), R ¹ represents 1 to 6 carbon atoms (preferably 1 to 1) such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, tert-butyl group, or pentyl group. 3) alkyl group; cycloalkyl group having 3 to 6 carbon atoms (typically 6) such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group; phenyl group, methylphenyl group, dimethylphenyl group, ethyl Aryl groups having 6 to 12 carbon atoms such as phenyl, propylphenyl, butylphenyl, naphthyl, methylnaphthyl and biphenyl; or perfluoroalkyls having 1 to 6 (preferably 1 to 3) carbon atoms Group; In a preferred embodiment, R ¹ in the above formula (I) is an alkyl group having 1 carbon atom (methyl group). That is, the compound represented by the formula (I) preferably has a methanesulfonic acid group (CH ₃ —S (═O) ₂ —O—). In such a case, the film resistance on the active material surface can be further reduced.
R ² , R ³ , R ⁴ , and R ⁵ are each independently a hydrogen atom; an alkyl group having 1 to 4 carbon atoms. In a preferred embodiment, R ^{2 to} R ⁵ in the above formula (I) are all hydrogen atoms. In such a case, reaction resistance in film formation can be reduced.

Examples of such sulfonic acid compounds include 2-butyne-1,4-diol dimethanesulfonate, 2-butyne-1,4-diol diethanesulfonate, 3-hexyne-2,5-diol dimethanesulfonate, 3- Hexin-2,5-diol diethane sulfonate, 2,5-dimethyl-3-hexyne-2,5-diol dimethane sulfonate, 2,5-dimethyl-3-hexyne-2,5-diol diethane sulfonate, etc. Illustrated. Of these, 2-butyne-1,4-diol dimethanesulfonate represented by the following formula (IV) can be preferably used.

  Moreover, various salts are mentioned as a typical example of a sulfonic acid derivative. Examples thereof include lithium salts, sodium salts, ammonium salts, and methyl esters of aliphatic sulfonic acids or aromatic sulfonic acids.

  As the phosphonoacetate compound, phosphonoacetate ester and derivatives thereof can be used, and those prepared by a known method or those obtained by purchasing a commercially available product are not particularly limited, and one or more kinds thereof are used. Can do. Thereby, the concentration of hydrogen fluoride in the non-aqueous electrolyte can be kept low (for example, 35 ppm or less, preferably 25 ppm or less, more preferably 20 ppm or less). As such a phosphonoacetate compound, a compound represented by the above formula (II) can be preferably used.

In the formula (II), R ⁶ and R ⁷ are each independently the number of carbon atoms such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, tert-butyl group, or pentyl group. An alkyl group having 1 to 6 (preferably 1 to 3); a cycloalkyl group having 3 to 6 carbon atoms (typically 6) such as cyclopropyl group, cyclobutyl group, cyclopentyl group and cyclohexyl group; vinyl group and propenyl An alkenyl group having 2 to 6 (preferably 2 to 4) carbon atoms such as a group, butenyl group and pentenyl group; 3 to 6 (preferably 3 to 4) carbon atoms such as propynyl, butynyl and pentynyl groups An alkynyl group; a halogenated alkyl group having 1 to 6 (preferably 1 to 3) carbon atoms; or a phenyl group, a methylphenyl group, a dimethylphenyl group, an ethylphenyl group, A; Ropirufeniru group, butylphenyl group, a naphthyl group, a methylnaphthyl group, an aryl group having 6 to 12 carbon atoms such as a biphenyl group.

In a preferred embodiment, R ⁶ in the above formula (II) is an alkyl group having 1 to 3 carbon atoms (eg, methyl group, ethyl group, propyl group). By using lower alkyl, the resistance of the coating on the active material surface can be further reduced.
In another preferable embodiment, R ⁷ in the above formula (II) is an alkynyl group having 3 carbon atoms (2-propynyl group). By using a 2-propynyl group, the resistance of the coating on the active material surface can be kept small.

Examples of such phosphonoacetate compounds include methyl dimethylphosphonoacetate, methyl diethylphosphonoacetate, ethyl dimethylphosphonoacetate, ethyl diethylphosphonoacetate, propyl dimethylphosphonoacetate, propyl diethylphosphonoacetate, and 2-propynyldimethyl. Examples include phosphonoacetate and 2-propynyl diethylphosphonoacetate. Of these, 2-propynyl diethylphosphonoacetate represented by the following formula (V) can be preferably used.

In a preferred embodiment disclosed herein, the phosphonoacetate compound (which may be in a form in which water is trapped) has the highest reduction potential (vs. Li / Li ⁺ ) among the components contained in the non-aqueous electrolyte. ). According to this aspect, the phosphonoacetate compound can be first reduced and decomposed at the time of the first charge. Thereafter, by reducing and decomposing the sulfonic acid compound and the vinylene carbonate compound, a highly durable coating film derived from the sulfonic acid compound and the vinylene carbonate compound is formed in a region closer to the surface of the negative electrode active material (upper layer portion of the coating film). Can be formed.

As the vinylene carbonate compound, a compound represented by the above formula (III) can be used, and those prepared by a known method or those obtained by purchasing a commercially available product are not particularly limited. The above can be used.
In the formula (III), R ⁸ and R ⁹ are each independently a hydrogen atom; an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group.
Specific examples of the vinylene carbonate compound represented by the formula (III) include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, dimethyl vinylene carbonate, ethyl methyl vinylene carbonate, diethyl vinylene carbonate, propyl vinylene carbonate, butyl vinylene carbonate and the like. .

In a preferred aspect, the non-aqueous electrolyte further contains a gas generating agent that can be decomposed to generate gas when a predetermined battery voltage is exceeded. As the gas generating agent, a compound capable of decomposing to generate a gas when a predetermined battery voltage is exceeded (that is, an oxidation potential (vs. Li / Li ⁺ ) is a charge upper limit potential (vs. Li / Li ⁺ ) of the positive electrode). The above compound can be used without any particular limitation as long as it is a compound that can be decomposed and generate gas when it is overcharged and becomes overcharged. Specific examples include aromatic compounds such as biphenyl compounds, alkylbiphenyl compounds, cycloalkylbenzene compounds, alkylbenzene compounds, organic phosphorus compounds, fluorine atom-substituted aromatic compounds, carbonate compounds, cyclic carbamate compounds, and alicyclic hydrocarbons. .
For example, in a battery in which the upper limit charge potential (vs. Li / Li ⁺ ) of the positive electrode is set to about 4.0 V to 4.3 V, biphenyl (oxidation potential: 4.5 V (vs. Li / Li ⁺ )) Cyclohexylbenzene (oxidation potential: 4.6 V (vs. Li / Li ⁺ )) can be preferably used. Since these gas generating agents have an oxidation potential close to the charge upper limit potential, they can undergo oxidative decomposition at the positive electrode at an early stage of overcharge, and can quickly generate gas (typically hydrogen gas). Further, since such a compound easily takes a conjugated system and easily transfers electrons, a large amount of gas can be generated. As a result, the CID can be operated quickly and accurately, and the reliability of the battery can be further enhanced.

  The concentration of the gas generating agent in the non-aqueous electrolyte is not particularly limited, but from the viewpoint of securing a sufficient gas amount for operating the CID, about 1% by mass or more with respect to 100% by mass of the non-aqueous electrolyte (Typically, 2% by mass or more, for example, 3% by mass or more) is preferable. By setting it as the above range, a sufficient amount of gas can be generated during overcharge, and the CID can be operated accurately. However, since the gas generating agent can be a resistance component of the battery reaction, if it is added excessively, the input / output characteristics may be deteriorated. From this viewpoint, the concentration of the gas generating agent is preferably 7% by mass or less (typically 5% by mass or less, for example, 4% by mass or less). By setting it as the said range, the increase in resistance at the time of normal use can be suppressed, and a high battery characteristic can be maintained and exhibited.

  Although not intended to be particularly limited, in the following, a flat wound electrode body (wound electrode body) and a nonaqueous electrolyte solution are accommodated in a flat rectangular parallelepiped (box) container. The present invention will be described in detail by taking a non-aqueous electrolyte secondary battery as an example. In the following drawings, members / parts having the same action are described with the same reference numerals, and redundant descriptions may be omitted or simplified. Further, the dimensional relationship (length, width, thickness, etc.) in each figure does not necessarily reflect the actual dimensional relationship.

  A schematic configuration of a non-aqueous electrolyte secondary battery according to an embodiment of the present invention is shown in FIG. FIG. 1 is a longitudinal sectional view schematically showing a sectional structure of a nonaqueous electrolyte secondary battery 100. This non-aqueous electrolyte secondary battery 100 is composed of an electrode body (捲) in which a long positive electrode sheet 10 and a long negative electrode sheet 20 are wound flatly via a long separator sheet 40. A rotating electrode body) 80 is housed in a flat box-shaped battery case 50 together with a non-aqueous electrolyte (not shown).

≪Battery case 50≫
The battery case 50 includes a flat rectangular parallelepiped (box-shaped) battery case main body 52 having an open upper end, and a lid 54 that closes the opening. On the upper surface of the battery case 50 (that is, the lid 54), a positive terminal 70 for external connection that is electrically connected to the positive electrode of the wound electrode body 80 and a negative electrode that is electrically connected to the negative electrode of the wound electrode body 80. A terminal 72 is provided. The lid 54 is also provided with a safety valve 55 for discharging the gas generated inside the battery case 50 to the outside of the case 50, similarly to the battery case of the conventional nonaqueous electrolyte secondary battery.

≪Current interruption mechanism 30≫
Inside the battery case 50, a current interrupting mechanism 30 that is activated by an increase in the internal pressure of the battery case is provided. When the internal pressure of the battery case 50 rises, the current interruption mechanism 30 cuts a conductive path from at least one of the electrode terminals (that is, the positive electrode terminal 70 and / or the negative electrode terminal 72) to the electrode body 80, thereby reducing the charging current. It is comprised so that it can interrupt | block. In this embodiment, the current interruption mechanism 30 is provided between the positive electrode terminal 70 fixed to the lid body 54 and the electrode body 80, and reaches from the positive electrode terminal 70 to the electrode body 80 when the internal pressure of the battery case 50 rises. The conductive path is configured to be cut.

The current interrupt mechanism 30 may include a conduction member, for example. In this embodiment, the conducting member is composed of a first member 32 and a second member 34. When the internal pressure of the battery case 50 increases, the first member 32 and / or the second member 34 (here, the first member 32) is deformed and separated from the other, whereby the conductive path can be cut. It is configured as follows. In this embodiment, the first member 32 is a deformed metal plate 32, and the second member 34 is a connection metal plate 34 joined to the deformed metal plate 32. The deformed metal plate (first member) 32 has an arch shape in which a central portion is curved downward, and a peripheral portion thereof is connected to the lower surface of the positive electrode terminal 70 via a current collecting lead terminal 35. Further, the tip of the curved portion 33 of the deformed metal plate 32 is joined to the upper surface of the connection metal plate 34. A positive current collector plate 74 is bonded to the lower surface (back surface) of the connection metal plate 34, and the positive current collector plate 74 is connected to the positive electrode sheet 10 of the electrode body 80. In this way, a conductive path from the positive electrode terminal 70 to the electrode body 80 is formed.
The current interruption mechanism 30 also includes an insulating case 38 formed of plastic or the like. The insulating case 38 is provided so as to surround the deformed metal plate 32, and hermetically seals the upper surface of the deformed metal plate 32. The internal pressure of the battery case 50 does not act on the upper surface of the hermetically sealed curved portion 33. The insulating case 38 has an opening into which the curved portion 33 of the deformed metal plate 32 is fitted, and the lower surface of the curved portion 33 is exposed from the opening to the inside of the battery case 50. The internal pressure of the battery case 50 acts on the lower surface of the curved portion 33 exposed inside the battery case 50.

  In the current interrupt mechanism 30 having such a configuration, when the internal pressure of the battery case 50 increases, the internal pressure acts on the lower surface of the curved portion 33 of the deformed metal plate 32, and the curved portion 33 curved downward is pushed upward. The upward pushing force of the curved portion 33 increases as the internal pressure of the battery case 50 increases. When the internal pressure of the battery case 50 exceeds the set pressure, the curved portion 33 is turned upside down and deformed so as to bend upward. Due to the deformation of the curved portion 33, the joint point 36 between the deformed metal plate 32 and the connection metal plate 34 is cut. As a result, the conductive path from the positive electrode terminal 70 to the electrode body 80 is cut, and the charging current is cut off.

  In this embodiment, the case where the conducting member that is deformed when the internal pressure is increased is composed of the first member 32 and the second member 34 is exemplified, but the present invention is not limited to this. For example, the conducting member is a single member. There may be. The current interrupt mechanism 30 is not limited to the positive terminal 70 side, and may be provided on the negative terminal 72 side. Furthermore, the current interruption mechanism 30 is not limited to the mechanical cutting accompanied by the deformation of the deformed metal plate 32 described above. For example, the internal pressure of the battery case 50 is detected by a sensor, and the charging current is detected when the detected internal pressure exceeds the set pressure. It is also possible to provide an external circuit that cuts off the current as a current cut-off mechanism.

≪Winded electrode body 80≫
FIG. 2 is a schematic diagram showing a configuration of the wound electrode body 80 shown in FIG. As shown in FIG. 2, the wound electrode body 80 according to the present embodiment has a long sheet structure (sheet-like electrode body) in a stage before assembly. The wound electrode body 80 includes a positive electrode sheet 10 in which the positive electrode active material layer 14 is formed along the longitudinal direction on one side or both sides (here, both sides) of the elongate positive electrode current collector 12, and a long elongate electrode body 80. A negative electrode sheet 20 having a negative electrode active material layer 24 formed on one side or both sides (here, both sides) of the negative electrode current collector 22 along the longitudinal direction is overlapped with a long separator sheet 40 to be long. It is formed into a flat shape by winding in the direction and further crushing it from the side direction.

  In the central portion of the wound electrode body 80 in the winding axis direction, there is a wound core portion (that is, the positive electrode active material layer 14 of the positive electrode sheet 10, the negative electrode active material layer 24 of the negative electrode sheet 20, and the separator sheet 40). A densely stacked portion) is formed. In addition, at both ends of the wound electrode body 80 in the winding axis direction, a part of the electrode active material layer non-forming portion of the positive electrode sheet 10 and the negative electrode sheet 20 protrudes outward from the wound core portion. The positive electrode side protruding portion and the negative electrode side protruding portion are respectively provided with a positive electrode current collecting plate 74 and a negative electrode current collecting plate 76, and are electrically connected to the positive electrode terminal 70 (FIG. 1) and the negative electrode terminal 72 (FIG. 1), respectively. Has been.

≪Method for manufacturing non-aqueous electrolyte secondary battery≫
The nonaqueous electrolyte secondary battery as described above can be manufactured, for example, as follows.
First, a battery is constructed by housing a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte in a battery case. Here, in addition to the non-aqueous solvent and the supporting salt, the non-aqueous electrolyte contains three types of additives, that is, a sulfonic acid compound having a triple bond, a vinylene carbonate compound, and a phosphonoacetate compound. . The phosphonoacetic acid ester compound can chemically react with the moisture in the battery simultaneously with the addition, and can reduce the amount of moisture remaining in the battery (water content). The addition amount of the three additives is not particularly limited because it may vary depending on, for example, the type and properties of the active material (for example, particle size and specific surface area), battery design parameters, charge / discharge pattern of the initial charge, and the like. For example, with respect to 100% by mass of the non-aqueous electrolyte, each added amount is about 0.1% by mass or more (typically 0.2% by mass or more, eg 0.5% by mass or more) and 10% by mass (typically Specifically, it may be 5% by mass or less, for example, 2% by mass or less.

Next, a charging process is performed so that the voltage between the positive electrode and the negative electrode becomes a predetermined value. In this charging treatment, the potential of the negative electrode (vs. Li / Li ⁺ ) is the sulfonic acid compound and the vinylene carbonate compound (in a preferred embodiment, the phosphonoacetate compound (which may be in a form in which water is trapped)). What is necessary is just to carry out so that it may become below the reduction potential. For example, charging may be performed at an appropriate rate until the voltage between the positive and negative terminals (typically the highest voltage reached) is approximately 3.95V to 4.05V. Thereby, the film derived from the said compound can be formed in the surface of a positive electrode active material and a negative electrode active material.

In a preferred example, first, the phosphonoacetate compound (which may be in a form in which water is trapped) is reduced and decomposed at the negative electrode, and is bonded (attached) to the surface of the negative electrode active material as a film. Next, the sulfonic acid compound having a triple bond and the vinylene carbonate compound are reduced and decomposed at the negative electrode, and a polymer film of these compounds is formed on the surface of the negative electrode active material (typically, the surface of the film derived from the phosphonoacetate compound). Is done. In addition, a part of the sulfonyloxy group (R—SO ₃ ) generated by the reductive decomposition moves to the positive electrode side, and a film derived from a sulfonic acid compound (typically a film having a sulfonyloxy group) on the surface of the positive electrode active material. For example, a film containing a sulfonyloxy group and a charge carrier).

Then, to analyze the film formed on the positive electrode, SO ₃ obtained in the analysis ^- and _SO ⁴ amount of ² to select the positive electrode becomes 3 [mu] mol / ^{m 2} or more 10 .mu.mol / ^{m 2} or less. Similarly, the film formed on the negative electrode is analyzed, and the amount of SO ₃ ⁻ and SO ₄ ²⁻ obtained by the analysis and the amount of CO ₃ ²⁻ are as follows: (1) SO ₃ ⁻ and the amount of _SO ^{4 2-} is at 3 [mu] mol / ^{m 2} or more 10 .mu.mol / ^{m 2} or less; (2) _CO ³ amount of ^2-, the SO ₃ ^- and _SO ⁴ 2 [mu] mol or more with respect to ^2-quantity 1 [mu] mol 7 [mu] mol A negative electrode satisfying any of the following ratios is selected. And the non-aqueous-electrolyte secondary battery can be constructed | assembled by a conventionally well-known method using the selected positive electrode and negative electrode. The selection of the positive electrode and the negative electrode can be omitted if there are no changes in the materials and design parameters used.

  Although the battery disclosed herein can be used for various applications, the effect of the coating formed on the surface of the positive electrode active material and the negative electrode active material is appropriately exhibited, and the battery characteristics (for example, high temperature durability) are higher than conventional ones. ) Can be realized. Moreover, when provided with the current interruption mechanism, it can be excellent in reliability (overcharge resistance) at the time of overcharge as compared with the conventional case. Therefore, taking advantage of such properties, for example, it can be suitably used as a driving power source mounted on a vehicle. The type of vehicle is not particularly limited, and examples thereof include plug-in hybrid vehicles (PHV), hybrid vehicles (HV), electric vehicles (EV), electric trucks, motorbikes, electric assist bicycles, electric wheelchairs, electric railways, and the like. . Therefore, according to the present invention, there is provided a vehicle including any of the nonaqueous electrolyte secondary batteries disclosed herein (which may be in the form of an assembled battery) as a power source.

  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.

[Construction of non-aqueous electrolyte secondary battery]
First, LiNi _0.33 Co _0.33 Mn _0.33 O ₂ (LNCM) was prepared as a positive electrode active material powder. The LNCM, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder are mixed in a kneader so that the mass ratio of these materials is LNCM: AB: PVdF = 90: 8: 2. The slurry was charged and kneaded while adjusting the viscosity with N-methylpyrrolidone (NMP) to prepare a positive electrode active material slurry. This slurry is applied to both surfaces of an aluminum foil (positive electrode current collector) having a thickness of 15 μm so that the basis weight is 30 mg / cm ² (per one surface), and is pressed after drying to be applied onto the positive electrode current collector. A positive electrode sheet (electrode density 3.0 g / cm ³ ) having a positive electrode active material layer was produced.

Next, spheroidized graphite (C) was prepared as a negative electrode active material. Such spheroidized graphite (C), styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a dispersant have a mass ratio of C: SBR: CMC = 98: 1: 1. The mixture was put into a kneader and kneaded while adjusting the viscosity with ion-exchanged water to prepare a negative electrode active material slurry. This slurry was applied to both sides of a long copper foil (negative electrode current collector) having a thickness of 10 μm so that the basis weight was 15 mg / cm ² (per one side), and pressed after drying, thereby negative electrode current collector. A negative electrode sheet (electrode density 1.4 g / cm ³ ) having a negative electrode active material layer on the body was produced.

The positive electrode sheet and the negative electrode sheet produced above are wound together with two separator sheets (here, a three-layer structure in which polypropylene (PP) is laminated on both surfaces of polyethylene (PE) is used). An electrode body was produced by molding into a flat shape. Next, a positive electrode terminal and a negative electrode terminal were attached to the lid of the battery case, and these terminals were welded to the positive electrode current collector and the negative electrode current collector exposed at the ends of the wound electrode body, respectively. The wound electrode body thus connected to the lid body was housed inside the battery case from the opening, and the opening and the lid were welded. And the non-aqueous electrolyte solution was inject | poured from the electrolyte solution injection hole provided in the cover body.
As a non-aqueous electrolyte, a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of EC: DMC: EMC = 30: 40: 30 is used as a supporting salt. Of LiPF ₆ at a concentration of 1.1 mol / L, cyclohexylbenzene (CHB) and biphenyl (BP) as gas generating agents, and the types of additives shown in Table 1 (ie, sulfonic acid compounds and / or A vinylene carbonate compound and / or a phosphonoacetic acid ester compound) was used. The CHB was added to 4% by mass with respect to the non-aqueous electrolyte, and the BP was added to 1% by mass with respect to the non-aqueous electrolyte. In Table 1, “BDMS” represents 2-butyne-1,4-diol dimethanesulfonate, “VC” represents vinylene carbonate, and “PDEPA” represents 2-propynyl diethylphosphonoacetate. ing.

For the batteries of Examples 1 to 7 constructed as described above, under a 25 ° C. environment, after performing constant current charging (CC charging) until the voltage between the positive and negative electrode terminals reaches 3.95 V, the current value becomes 0. 0. Constant voltage charging (CV charging) was performed until the temperature reached 02C. Next, the battery after the charge treatment was aged by leaving it in a constant temperature bath at a temperature of 60 ° C. for 24 hours. In this way, lithium ion secondary batteries (Examples 1 to 7) having a theoretical capacity of 285 kWh / m ³ were obtained. In addition, at least three batteries (for quantitative determination of hydrogen fluoride, for high temperature storage durability test, and for film analysis) were prepared for each example.

[Measurement of initial characteristics (initial capacitance and IV resistance)]
With respect to the obtained battery, the initial capacity was measured according to the following procedures 1 to 3 in a voltage range of 3.0 V to 4.1 V under an environment of 25 ° C.
(Procedure 1) After reaching 3.0 V by 1/3 C constant current discharge, discharge by constant voltage discharge for 2 hours and then rest for 10 minutes.
(Procedure 2) After reaching 4.1 V by 1/3 C constant current charging, constant voltage charging is performed until the current reaches 1/100 C, and then resting for 10 minutes.
(Procedure 3) After reaching 3.0 V by 1/3 C constant current discharge, constant voltage discharge is performed until the current becomes 1/100 C, and then stopped for 10 minutes.
Then, the discharge capacity (CCCV discharge capacity) in the discharge from the constant current discharge to the constant voltage discharge in the procedure 3 was set as the initial capacity.
Next, IV resistance was measured in an environment of 25 ° C. Specifically, the battery was first adjusted to a state of SOC 20%, CC discharge to 3 V was performed on the battery at a discharge rate of 10 C, and a voltage drop for 10 seconds from the discharge was measured. The measured voltage drop value (V) was divided by the corresponding current value to calculate the IV resistance (Ω), and the average value was taken as the initial resistance.

[Electrode film analysis]
The battery after the initial characteristic evaluation was discharged to a state of SOC 0%, then disassembled, the electrode was taken out, and the coating amount of the electrode was quantified.
Specifically, the battery after the initial capacity measurement was first disassembled in a moisture-controlled glove box, and the positive electrode and the negative electrode were taken out. Next, after immersing the positive electrode and the negative electrode in EMC using a non-aqueous electrolyte for about 10 minutes, 10 pieces each were cut out at an appropriate size (here, Φ40 mm) to obtain a measurement sample. It was. Next, the sample for measurement (the cut out positive electrode and the negative electrode) was immersed in a 50% acetonitrile (CH ₃ CN) aqueous solution for about 10 minutes, respectively, and a coating component derived from 2-butyne-1,4-diol dimethanesulfonate Extracted. Next, the amount of SO ₃ ⁻ and SO ₄ ²⁻ (μmol / cm ² ) was measured by quantitative analysis of the solution by IC. As an analyzer, an ion chromatograph (ICS-3000) manufactured by Nippon Dionex Co., Ltd. was used. The amount of SO ₃ ⁻ and SO ₄ ²⁻ (μmol / cm ² ) obtained is the product of the BET specific area (m ² / g) of the active material and the basis weight of the active material (g / cm ² ). By dividing, the coating amount (μmol / m ² ) per unit specific surface area (1 m ² ) of the active material in each of the positive and negative electrodes was calculated. The results are shown in the column of “Coating amount derived from sulfonic acid” in Table 1. In Table 1, “-” in the column of the coating indicates that the compound that is the origin of the coating was not added.

Furthermore, about the negative electrode, after immersing in the said EMC, 10 sheets were cut out separately by appropriate magnitude | size, and the sample for a measurement was obtained. The sample for measurement was immersed in ion-exchanged water for about 10 minutes to extract a film component derived from vinylene carbonate and a film component derived from 2-propynyl diethylphosphonoacetate compound. Next, the amount of CO ₃ ²⁻ (μmol / cm ² ) and the amount of RO ₂ —P (═O) —CH ₂ —C (═O) —O ⁻ ( μmol / cm ² ) was measured. The resulting _CO ³ amount of ^{2- _{(μmol / cm 2) SO 3}} - is divided by and _SO ⁴ amount of ^2- ([mu] mol / cm ^2), was calculated abundance ratio in the mixed film (the existence ratio) . This is shown in the “VC ratio” column of Table 1. In Table 1, “VC only” in the column of VC ratio means that a VC-derived film is formed on the surface of the negative electrode active material without using 2-butyne-1,4-diol dimethanesulfonate. It shows that the same amount as Example 4 was formed.
Further, the amount of the coating derived from 2-propynyl diethylphosphonoacetate compound is divided by the product of the BET specific area (m ² / g) of the active material and the basis weight of the active material (g / cm ² ), thereby obtaining the negative electrode active The coating amount (μmol / m ² ) per unit specific surface area (1 m ² ) of the substance was calculated. The results are shown in the column of “Amount of coating derived from phosphonoacetate” in Table 1.

[Quantitative determination of hydrogen fluoride]
The battery after the initial characteristic evaluation was disassembled, and the amount (ppm) of hydrogen fluoride contained in the nonaqueous electrolytic solution was measured by a titration method. The results are shown in the corresponding column of Table 1.

  As shown in Table 1, in Example 1 and Example 7 in which the phosphonoacetate compound was not added, the concentration of hydrogen fluoride was relatively high at 60 ppm to 70 ppm. On the other hand, in Examples 2 to 6 in which the phosphonoacetate compound was added, the concentration of hydrogen fluoride was 35 ppm or less (preferably 25 ppm or less, more preferably 20 ppm or less), compared to when no phosphonoacetate compound was added. It was found that it was suppressed to about half or less. The reason for this is that, as described above, the inclusion of the phosphonoacetic acid ester compound caused the reaction between the compound and moisture, and the moisture was trapped in the structure of the compound.

[High temperature storage durability test]
In addition, after the internal pressure sensor was attached to the battery after the above initial characteristic evaluation, the battery was adjusted to an SOC of 85% in an environment of 25 ° C. and stored in a thermostatic bath at a temperature of 60 ° C. for about 100 days.
For the battery after the high temperature storage durability test, the elution amount of Mn from the positive electrode active material was measured. In general, it is considered that the metal element eluted from the positive electrode active material moves in the non-aqueous electrolyte and precipitates on the negative electrode. Further, among the materials used for battery construction, the material containing Mn is only the positive electrode active material. For this reason, the negative electrode was taken out from the battery after the above high-temperature storage durability, and the amount of Mn deposited on the negative electrode active material layer was measured to obtain the Mn elution amount from the positive electrode active material. Specifically, the battery after the high-temperature storage durability was first discharged to a SOC of 0%, disassembled, and the negative electrode portion located on the outermost periphery of the wound electrode body was cut out. Next, the negative electrode was lightly washed 2 to 3 times with a non-aqueous solvent used as a non-aqueous electrolyte solution, and then punched into an arbitrary size to obtain a measurement sample for ICP-AES analysis. The amount of manganese (Mn) element (μmol) was measured by dissolving the sample for measurement in an acidic solvent (here, using sulfuric acid) by heating and analyzing the solution by ICP-AES. The obtained measured value (μmol) was divided by the area (cm ² ) of the negative electrode active material layer of the sample to be analyzed to obtain the Mn elution amount (μmol / cm ² ) per unit area of the measured sample. By dividing this value by the product of the basis weight of the negative electrode active material (g / cm ² ) and the BET specific surface area (m ² / g) of the negative electrode active material, “Mn from the positive electrode active material per 1 m ^{2 of} specific surface area” The amount of elution was calculated. The results are shown in the corresponding column of Table 1.

As shown in Table 1, in Examples 1 and 7 where the hydrogen fluoride concentration in the non-aqueous electrolyte was high, the Mn elution amount from the positive electrode active material was about 0.2 μmol / m ^{2, which} is a relatively high value. showed that. This is because the water in the battery reacts with the non-aqueous electrolyte (typically the supporting salt) to generate a lot of hydrogen fluoride (the acidity of the non-aqueous electrolyte increases) It is conceivable that the elution of the constituent element (Mn) of the alloy accelerated. Further, in Example 5 in which no sulfonic acid compound was added, the Mn elution amount from the positive electrode active material was about 0.15 μmol / m ^2, which was a relatively high value. This is probably because the interface with the non-aqueous electrolyte was unstable because a film derived from a sulfonic acid compound was not formed on the surface of the positive electrode active material. On the other hand, in Examples 2 to 4 and Example 6, it was found that the elution amount of Mn was suppressed to as low as about 0.05 μmol / m ² .

Moreover, about the battery after a high-temperature storage durability test, the precipitation amount of lithium fluoride (LiF) in a positive electrode was measured. Specifically, first, similarly to the measurement of the Mn elution amount, the battery after high-temperature storage durability was discharged to a SOC of 0%, disassembled, and the positive electrode was taken out. Next, after lightly washing the positive electrode 2-3 times with a non-aqueous solvent used as a non-aqueous electrolyte, it is punched into an arbitrary size and immersed in ion-exchanged water for a predetermined time (for example, about 1 to 30 minutes). As a result, the film component (F ⁻ ) to be measured was extracted into water. This solution was subjected to IC measurement, and the content (μmol) of ions (F ⁻ ) to be measured was quantified. The obtained measurement value (μmol) was divided by the area (cm ² ) of the positive electrode active material layer of the sample to be analyzed, to obtain the LiF precipitation amount (μmol / cm ² ) per unit area of the measurement sample. Then, by dividing this value by the product of the basis weight (g / cm ² ) of the positive electrode active material and the BET specific surface area (m ² / g) of the positive electrode active material, “LiF precipitation per 1 m ² of specific surface area of the positive electrode” "Amount" was determined. The results are shown in the corresponding column of Table 1.

As shown in Table 1, the LiF precipitation amount and the above-described Mn elution amount showed the same tendency. That is, in Example 1 and Example 7 where the phosphonoacetate compound was not added and the hydrogen fluoride concentration in the non-aqueous electrolyte was high, a relatively large amount of lithium fluoride was confirmed at the positive electrode. In Example 5 where no sulfonic acid compound was added, a relatively large amount of lithium fluoride was confirmed.
In contrast, Examples 2 4 and Example 6, it was found that the precipitation amount of lithium fluoride is suppressed to 2.6μmol / ^{m 2} or less (e.g., 2.5 .mu.mol / ^{m 2} or less).

  Further, the battery after completion of the test was taken out from the thermostat, and the battery capacity and IV resistance were measured in the temperature environment of 25 ° C. in the same manner as the initial characteristics. Then, the capacity retention rate (%) and the IV resistance increase rate (%) were calculated by dividing the value after the high temperature storage durability test by the initial value. Moreover, the increase value of the internal pressure was read from the internal pressure sensor attached to the battery, and the amount of gas generated was calculated from the state equation (PV = nRT). The results are shown in the corresponding column of Table 1.

As shown in Table 1, in Examples 1 and 7, the amount of LiF deposited after the high-temperature storage durability test was large, and the IV resistance increase rate was relatively high. Moreover, the capacity maintenance rate was relatively low. The reason for this is considered that the generated HF attacked the surface of the negative electrode (negative electrode active material) and promoted the decomposition of the coating on the negative electrode surface. Furthermore, it is considered that the amount of gas generated is relatively increased due to such a side reaction.
In Example 5, the amount of LiF deposited after the high temperature storage durability test was large, and the IV resistance increase rate was relatively high. This may be because the positive electrode active material was susceptible to HF attack because no sulfonic acid compound was added. In addition, it is considered that the gas generation amount relatively increased due to this.
In Example 6, the capacity retention rate was low. The reason for this is considered that since no vinylene carbonate compound was added, the stability and durability of the coating on the negative electrode (negative electrode active material) surface was insufficient, and the reductive decomposition of the electrolytic solution advanced. In addition, it is considered that the gas generation amount relatively increased due to this.

For these, batteries of Examples 2 to 4 according to the present invention, i.e. in the coating of the positive electrode active material and the anode active material SO ₃ ^- and _SO ^{4 2-respectively} 3 [mu] mol / ^{m 2} or more 10 .mu.mol / ^{m 2} or less In addition, in the coating film of the negative electrode active material, CO ₃ ^{2− in} a ratio of 2 μmol to 7 μmol with respect to the amount of SO ₃ ⁻ and SO ₄ ²⁻ of 1 μmol, and phosphonoacetate ions derived from the phosphonoacetate compound The battery provided with (RO ₂ —P (═O) —CH ₂ —C (═O) —O ⁻ ) exhibited relatively excellent high-temperature storage durability. According to such a configuration, generation of HF can be suppressed, and generation of LiF on the surface of the positive electrode (positive electrode active material) can be suppressed, so that the non-aqueous electrolyte secondary solution with a low IV resistance increase rate and a high capacity retention rate can be obtained. The battery could be realized. Further, by suppressing the useless reductive decomposition reaction of the non-aqueous electrolyte as described above, the amount of gas generated can be reduced. Therefore, the operability of the pressure type current interruption mechanism can be improved, and a highly reliable non-aqueous electrolyte secondary battery can also be realized.

In particular, in Examples 2 and 3, the amount of phosphonoacetate ions contained in the coating film of the negative electrode active material is 3 μmol / m ^{2 to} 12 μmol / m ² , thereby suppressing the generation of HF to 35 ppm or less. And the production of LiF on the surface of the positive electrode (positive electrode active material) could be suppressed to 0.06 μmol / m ² or less. FIG. 3 shows the relationship between the amount of phosphonoacetate ions in the coating and the high-temperature storage durability characteristics (capacity retention rate and IV resistance increase rate). By setting the amount of phosphonoacetate ions contained in the coating film of the negative electrode active material to 3 μmol / m ^{2 to} 12 μmol / m ² , the IV resistance increase rate is 15% even when stored at 60 ° C. for 100 days, for example. It was found that the capacity retention rate could be maintained at 94% or more. Furthermore, it was found that the amount of gas generated can be suppressed to 20 cm ³ or less. Such a result indicates the technical significance of the present invention.

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

10 Positive electrode sheet (positive electrode)
12 Positive electrode current collector 14 Positive electrode active material layer 20 Negative electrode sheet (negative electrode)
22 Negative electrode current collector 24 Negative electrode active material layer 30 Current interruption mechanism 32 Deformed metal plate (conductive member; first member)
33 curved portion 34 connecting metal plate (conducting member; second member)
35 Current collecting lead terminal 36 Joint point 38 Insulating case 40 Separator sheet (separator)
DESCRIPTION OF SYMBOLS 50 Battery case 52 Battery case main body 54 Cover body 55 Safety valve 70 Positive electrode terminal 72 Negative electrode terminal 80 Winding electrode body 100 Nonaqueous electrolyte secondary battery

Claims (10)

A positive electrode having a positive electrode active material made of a lithium composite metal oxide, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte are non-aqueous electrolyte secondary batteries housed in a battery case,
The non-aqueous electrolyte includes a sulfonic acid compound having a triple bond, a vinylene carbonate compound, and a phosphonoacetate compound at the time of battery construction,
The positive electrode active material and the negative electrode active material each have a coating,
Coating the positive electrode active material, the SO ₃ derived from a sulfonic acid compound ^- a and _SO ^{4 2-,} contained in the positive electrode active 10 .mu.mol / ^{m 2} specific surface area 1 m ² per 3 [mu] mol / ^{m 2} or more substances less,
The negative active material of the coating, the SO ₃ derived from a sulfonic acid compound ^- a and _SO ^{4 2-,} contained in the negative active ratio of material surface area 1 m ² per 3 [mu] mol / ^{m 2} or more 10 .mu.mol / ^{m 2} or less, and A non-aqueous electrolyte secondary battery containing CO ₃ ²⁻ derived from the vinylene carbonate compound at a ratio of 2 μmol to 7 μmol with respect to 1 μmol of SO ₃ ⁻ and SO ₄ ²⁻ . The coating of the positive electrode active material, the SO ₃ ^- and _SO ^{4 2-a} contains at the positive electrode active ratio of material surface area 1 m ² per 3 [mu] mol / ^{m 2} or more 8 [mu] mol / ^{m 2} or less,
The coating film of the negative electrode active material contains the SO ₃ ⁻ and SO ₄ ²⁻ at 5 μmol / m ² or more and 10 μmol / m ² or less per 1 m ² of the specific surface area of the negative electrode active material,
2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the amount of SO ₃ ⁻ and SO ₄ ²⁻ is greater in the negative electrode active material coating than in the positive electrode active material coating. The coating film of the negative electrode active material contains phosphonoacetate ions derived from the phosphonoacetate compound at 3 μmol / m ² or more and 12 μmol / m ² or less per 1 m ² of the specific surface area of the negative electrode active material. The nonaqueous electrolyte secondary battery as described.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the lithium composite metal oxide contains a manganese element (Mn). The lithium composite metal oxide is a lithium nickel cobalt manganese composite oxide,
The proportion of manganese is 30 mol% or more and 40 mol% or less when the total of nickel, cobalt, and manganese in the lithium nickel cobalt manganese composite oxide is 100 mol%, according to any one of claims 1 to 4. The nonaqueous electrolyte secondary battery as described.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein the battery case includes a pressure-type current interruption mechanism. When the film of the negative electrode active material is divided in the thickness direction for 2 minutes, the components of the film are different between the upper layer part and the lower layer part,
In the upper layer portion, the amount of the coating derived from the sulfonic acid compound and the vinylene carbonate compound is large,
The non-aqueous electrolyte secondary battery according to any one of claims 3 to 6, wherein in the lower layer portion, the amount of the coating derived from the phosphonoacetate compound is large. The non-aqueous electrolyte secondary battery according to claim 1, wherein the sulfonic acid compound is a compound represented by the following formula (I).

(Wherein R ¹ is an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a perfluoroalkyl having 1 to 6 carbon atoms. R ² , R ³ , R ⁴ and R ⁵ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.) The nonaqueous electrolyte secondary battery according to any one of claims 1 to 8, wherein the phosphonoacetic acid ester compound is a compound represented by the following formula (II).

(Here, R ⁶ and R ⁷ are each independently an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or the number of carbon atoms. 3 to 6 alkynyl groups, halogenated alkyl groups having 1 to 6 carbon atoms, or aryl groups having 6 to 12 carbon atoms.) The non-aqueous electrolyte secondary battery according to any one of claims 1 to 9, wherein the vinylene carbonate compound is a compound represented by the following formula (III).

(Here, R ⁸ and R ⁹ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

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