JP2017199572A - Lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery superior in rate characteristic.SOLUTION: A lithium ion secondary battery comprises: a positive electrode having a positive electrode current collector, and a positive electrode terminal put in contact with the positive electrode current collector; a negative electrode having a negative electrode current collector, and a negative electrode terminal put in contact with the negative electrode current collector; and an electrolyte solution. The electrolyte solution contains an electrolyte including a lithium salt represented by the general formula (1) below, and an organic solvent including a chain carbonate represented by the general formula (2) below; the chain carbonate is included in a range of a mole ratio of 3-6 to the lithium salt. A contact area of the positive electrode current collector and positive electrode terminal to a battery capacity, or a contact area of the negative electrode current collector and negative electrode terminal to the battery capacity is larger than 3 mm/Ah. (RX)(RSO)NLi General formula (1); and ROCOORGeneral formula (2).SELECTED DRAWING: None

Description

  The present invention relates to a lithium ion secondary battery.

In general, a power storage device such as a secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution as main components. An appropriate electrolyte is added to the electrolytic solution in an appropriate concentration range. For example, a lithium salt such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , CF ₃ SO ₃ Li, or (CF ₃ SO ₂ ) ₂ NLi is added as an electrolyte to the electrolyte solution of a lithium ion secondary battery. Here, the concentration of the lithium salt in the electrolytic solution is generally about 1 mol / L.

  In general, an organic solvent used in the electrolytic solution is mixed with about 30% by volume or more of cyclic carbonate such as ethylene carbonate or propylene carbonate in order to dissolve the electrolyte appropriately.

Actually, Patent Document 1 discloses a lithium ion secondary battery using a mixed organic solvent containing 33% by volume of ethylene carbonate and using an electrolytic solution containing LiPF ₆ at a concentration of 1 mol / L.

  In addition, for the purpose of improving the performance of the secondary battery, researches for adding various additives to an electrolytic solution containing a lithium salt have been actively conducted.

For example, Patent Document 2 describes an electrolytic solution using a mixed organic solvent containing 30% by volume of ethylene carbonate and adding a small amount of a specific additive to an electrolytic solution containing LiPF ₆ at a concentration of 1 mol / L. A lithium ion secondary battery using this electrolytic solution is disclosed.

Patent Document 3 also describes an electrolytic solution in which a small amount of phenylglycidyl ether is added to a solution containing a mixed organic solvent containing 30% by volume of ethylene carbonate and LiPF ₆ at a concentration of 1 mol / L. A lithium ion secondary battery using this electrolytic solution is disclosed.

  As described in Patent Documents 1 to 3, conventionally, in an electrolytic solution used for a lithium ion secondary battery, a mixed organic solvent containing about 30% by volume of cyclic carbonate such as ethylene carbonate or propylene carbonate is used, and It has become common technical knowledge to contain lithium salt at a concentration of approximately 1 mol / L. And as described in Patent Documents 2 to 3, the improvement of the electrolytic solution is generally performed by paying attention to an additive separate from the lithium salt.

  Unlike the conventional points of interest of those skilled in the art, the present inventors have focused on an electrolytic solution containing a metal salt at a high concentration and in which the metal salt and the organic solvent are present in a new state, and patented the results. Reported in Reference 4.

JP 2013-149477 A JP 2013-145724 A JP2013-137873A International Publication No. 2015/045389

  When a lithium ion secondary battery is charged and discharged at a high current rate (hereinafter referred to as a high rate), the capacity is higher than that in a case where charging and discharging is performed at a low current rate (hereinafter referred to as a low rate). Is known to decrease. Therefore, a lithium ion secondary battery excellent in rate characteristics is required from the industry. In the lithium ion secondary battery, being excellent in rate characteristics means that the lithium ion secondary battery can be charged / discharged relatively favorably even when charging / discharging at a high rate. An object of this invention is to provide the lithium ion secondary battery excellent in the rate characteristic.

  Lithium ion secondary batteries are affected by various resistances during charging and discharging. In order to develop a high capacity, it is desired to reduce various resistances as much as possible.

  The resistance that affects charging / discharging is roughly defined by electronic resistance, ion resistance, charge transfer resistance (reaction resistance), and diffusion resistance.

  In particular, regarding ion resistance and diffusion resistance, the ease of movement of lithium ions in the electrolyte (ionic conductivity) and the amount of lithium ions supplied from the electrolyte to the active material have a strong effect. Specifically, the electrolyte solution impregnates the hole portion of the positive electrode active material, the hole portion of the negative electrode active material, and the separator hole portion, and transports lithium ions between the positive electrode active material and the negative electrode active material during charge and discharge. Bear. At this time, if the required moving speed or amount is larger than the moving speed or amount of lithium ions in the actual electrolyte, the supply of lithium ions to the positive electrode active material and the negative electrode active material is delayed, and charging and discharging are sufficiently performed. The reaction does not proceed.

In order to solve the delay in the supply of lithium ions to the positive electrode active material and the negative electrode active material, it is conceivable to increase the mobility of lithium ions in the electrolytic solution and to increase the amount of lithium ions in the electrolytic solution. However, the electrolytic solution used in the conventional lithium ion secondary battery is obtained by dissolving about 1 mol / L of LiPF ₆ in a mixed solvent of ethylene carbonate and chain carbonate, but the LiPF ₆ concentration is increased to 1 mol / L or more. And fluidity | liquidity will fall and ionic conductivity will fall rapidly.

  The inventor conducted further studies on the electrolytic solution described in Patent Document 4. And if it is a lithium ion secondary battery comprising an electrolytic solution containing a specific lithium salt and a specific organic solvent in a specific molar ratio, it can be suitably charged and discharged even at the time of charge and discharge at a high rate. I found out. Furthermore, the inventor of the present invention provides a lithium ion secondary battery comprising the electrolytic solution by setting the contact area between the current collector and the terminal with respect to the battery capacity to be within a certain range or the active material of the current collector. By making the ratio of the contact area between the current collector and the terminal with respect to the area of the layer non-arranged portion more than a certain range, it was found that charging and discharging can be performed relatively favorably even during charging and discharging at a high rate, The present invention has been completed.

That is, the first aspect of the lithium ion secondary battery of the present invention includes a positive electrode having a positive electrode current collector and a positive electrode terminal in contact with the positive electrode current collector, a negative electrode current collector, and a negative electrode current collector. A lithium ion secondary battery comprising a negative electrode having a negative electrode terminal in contact with the electrolyte, and an electrolyte solution,
The electrolytic solution includes an electrolyte containing a lithium salt represented by the following general formula (1) and an organic solvent containing a chain carbonate represented by the following general formula (2), and is in a chain form with respect to the lithium salt. Carbonate is included in a molar ratio of 3-6,
The contact area between the positive electrode current collector and the positive electrode terminal with respect to the battery capacity or the contact area between the negative electrode current collector and the negative electrode terminal with respect to the battery capacity is greater than 3 mm ² / Ah.
(R ¹ X ¹ ) (R ² SO ₂ ) NLi General formula (1)
(R ¹ is hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted with, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, or an alkoxy group which may be substituted with a substituent , An unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, an unsaturated thioalkoxy group that may be substituted with a substituent, CN, SCN, or OCN Is done.
R ² represents hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, an alkoxy group which may be substituted with a substituent, Selected from an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, CN, SCN, OCN The
R ¹ and R ² may be bonded to each other to form a ring.
X ¹ is selected from SO ₂ , C = O, C = S, R ^a P = O, R ^b P = S, S = O, Si = O.
R ^a and R ^b are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a group that may be substituted with a substituent. A saturated alkyl group, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, a heterocyclic group that may be substituted with a substituent, and a substituent An alkoxy group which may be substituted, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, OH , SH, CN, SCN, and OCN.
R ^a and R ^b may combine with R ¹ or R ² to form a ring. )
R ²⁰ OCOOR ²¹ general formula (2)
(R ²⁰ and R ²¹ each independently represent C _n H _a F _b Cl _c Br _d I _e which is a chain alkyl, or C _m H _f F _g Cl _h Br _i I containing a cyclic alkyl in the chemical structure. selected from _j , n is an integer of 1 or more, m is an integer of 3 or more, a, b, c, d, e, f, g, h, i, j are each independently an integer of 0 or more 2n + 1 = a + b + c + d + e, 2m = f + g + h + i + j is satisfied.)

The second aspect of the lithium ion secondary battery of the present invention is a positive electrode current collector, a positive electrode active material layer disposed in a positive electrode active material layer arrangement portion on the surface of the positive electrode current collector, and a positive electrode current collector. A positive electrode having a positive electrode terminal in contact with the positive electrode active material layer non-arranged portion on the surface, a negative electrode current collector, and a negative electrode active material disposed on the negative electrode active material layer arranged portion on the surface of the negative electrode current collector A negative electrode having a material layer, and a negative electrode terminal in contact with the negative electrode active material layer non-arranged portion on the surface of the negative electrode current collector, and a lithium ion secondary battery comprising an electrolyte solution,
The electrolytic solution includes an electrolyte containing a lithium salt represented by the above general formula (1) and an organic solvent containing a chain carbonate represented by the above general formula (2), and has a chain with respect to the lithium salt. In a molar ratio of 3-6,
The ratio of the contact area between the positive electrode current collector and the positive electrode terminal relative to the area of the positive electrode active material layer non-arranged portion, or the contact between the negative electrode current collector and the negative electrode terminal relative to the area of the negative electrode active material layer non-arranged portion The area ratio is 2% to 100%.

  Hereinafter, the first aspect and the second aspect of the lithium ion secondary battery of the present invention will be collectively referred to as the lithium ion secondary battery of the present invention.

  The lithium ion secondary battery of the present invention is excellent in rate characteristics.

It is a cross-sectional schematic diagram explaining the electrode group of the lithium ion secondary battery of this embodiment. It is a graph showing the relationship between the molar ratio of chain carbonate / lithium salt and ionic conductivity. It is an overwriting of the DSC curve obtained in Reference Evaluation Example 5. It is an overwriting of the DSC curve obtained in Reference Evaluation Example 6. 3 is a schematic diagram illustrating a positive electrode of Example 1. FIG. 4 is a schematic diagram illustrating a positive electrode of Example 2. FIG. It is a graph which compares the ratio of the discharge duration for every rate of the lithium ion secondary battery of Example 1, Example 2, Comparative Example 1, and Comparative Example 2. It is a graph which compares the ratio of the charge duration for each rate of the lithium ion secondary battery of Example 1, Example 2, Comparative Example 1, and Comparative Example 2. It is a graph which shows the relationship between the voltage for every 50C rate of the lithium ion secondary battery of the comparative example 1, 75C rate, and 150C rate, and discharge duration (second). It is a graph which shows the relationship between the voltage for every 50C rate of the lithium ion secondary battery of Example 1, 75C rate, and 150C rate, and discharge duration (second). It is a graph which shows the relationship between the voltage (mV) of 150 C rate of the lithium ion secondary battery of Example 1, and discharge duration (second). It is a graph which shows the relationship between the voltage (mV) of 150 C rate of the lithium ion secondary battery of Example 2, and discharge duration (second). It is a graph which compares the ratio of the contact area with respect to battery capacity, and discharge duration. It is a graph which compares the ratio of the contact area of the collector for positive electrodes and the terminal for positive electrodes with respect to the area of the positive electrode active material layer non-arrangement part, and the ratio of discharge duration.

  Below, the form for implementing this invention is demonstrated. Unless otherwise specified, the numerical range “ab” described herein includes the lower limit “a” and the upper limit “b”. The numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from the numerical value range can be used as upper and lower numerical values.

The first aspect of the lithium ion secondary battery of the present invention is a positive electrode having a positive electrode current collector and a positive electrode terminal in contact with the positive electrode current collector, and is in contact with the negative electrode current collector and the negative electrode current collector. And a contact area between the positive electrode current collector and the positive electrode terminal with respect to the battery capacity (hereinafter referred to as “positive electrode current collector and positive electrode”). "Contact area with the terminal for the battery" may be simply referred to as "positive electrode contact area"), or the contact area between the current collector for the negative electrode and the terminal for the negative electrode with respect to the battery capacity (hereinafter referred to as "the current collector for the negative electrode"). The contact area between the negative electrode terminal and the negative electrode terminal ”may be simply referred to as“ negative electrode contact area. ”) Is larger than 3 mm ² / Ah.

  The second aspect of the lithium ion secondary battery of the present invention is a positive electrode current collector, a positive electrode active material layer disposed in a positive electrode active material layer arrangement portion on the surface of the positive electrode current collector, and a positive electrode current collector. A positive electrode having a positive electrode terminal in contact with the positive electrode active material layer non-arranged portion on the surface, a negative electrode current collector, and a negative electrode active material disposed on the negative electrode active material layer arranged portion on the surface of the negative electrode current collector A negative electrode having a material layer, and a negative electrode terminal in contact with the negative electrode active material layer non-arranged portion on the surface of the negative electrode current collector, and an electrolyte described below, and The ratio of the contact area between the positive electrode current collector and the positive electrode terminal to the area of the arrangement part, or the ratio of the contact area between the negative electrode current collector and the negative electrode terminal to the area of the negative electrode active material layer non-arrangement part is 2 % Or more and 100% or less.

  The lithium ion secondary battery of the present invention includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode has a positive electrode current collector, a positive electrode active material layer, and a positive electrode terminal, and the negative electrode has a negative electrode current collector, a negative electrode active material layer, and a negative electrode terminal.

(Current collector)
The current collector refers to a chemically inert electronic conductor that keeps a current flowing through an electrode during discharge or charging of a lithium ion secondary battery.

  The positive electrode current collector is not particularly limited as long as it is a metal that can withstand a voltage suitable for the active material to be used. For example, silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin , Indium, titanium, ruthenium, tantalum, chromium, molybdenum, and metal materials such as stainless steel.

  When the potential of the positive electrode is 4 V or more on the basis of lithium, it is preferable to employ aluminum as the positive electrode current collector.

  Specifically, it is preferable to use a positive electrode current collector made of aluminum or an aluminum alloy. Here, aluminum refers to pure aluminum, and aluminum having a purity of 99.0% or more is referred to as pure aluminum. An alloy obtained by adding various elements to pure aluminum is referred to as an aluminum alloy. Examples of the aluminum alloy include Al—Cu, Al—Mn, Al—Fe, Al—Si, Al—Mg, AL—Mg—Si, and Al—Zn—Mg.

  Specific examples of aluminum or aluminum alloy include A1000 series alloys (pure aluminum series) such as JIS A1085 and A1N30, A3000 series alloys (Al-Mn series) such as JIS A3003 and A3004, JIS A8079, A8021, etc. A8000-based alloy (Al-Fe-based).

  The current collector may be covered with a known protective layer. What collected the surface of the electrical power collector by the well-known method may be used as an electrical power collector.

  The current collector preferably has a shape capable of grasping a surface such as a foil, a sheet, a film, or a mesh. Therefore, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, and a stainless steel foil can be suitably used as the current collector. When the current collector is in the form of foil, sheet or film, the thickness is preferably in the range of 1 μm to 100 μm.

  As the negative electrode current collector, an appropriate one of those described in the positive electrode current collector may be adopted. For example, a copper foil is preferably used as the negative electrode current collector.

(Terminal)
The positive electrode terminal and the negative electrode terminal transfer electrons from the current collector of each electrode to the outside. Each terminal is preferably made of a conductive material. The material of each terminal is preferably the same as the material of each current collector in contact, but may be different from the material of the current collector in contact.

  As the positive electrode terminal and the negative electrode terminal, a metal having a foil shape, a plate shape, a linear shape or a rod shape is preferably used.

  The planar shapes of the positive electrode terminal and the negative electrode terminal are not particularly limited. Examples of the planar shape of the terminal include a strip-like rectangular shape, a T shape having a large contact area with the current collector, and a comb shape having a plurality of contact surfaces with the current collector.

(About contact area)
A contact area means the total area which a collector and a terminal contact in each electrode of a lithium ion secondary battery. A plurality of terminals may be provided for one current collector, and a contact surface of one terminal may be divided into a plurality of terminals for one current collector.

  Moreover, it is desirable that the current collector and the terminal are welded at the contact location. Hereinafter, the contact area may be referred to as a welding area. The method for welding the terminal to the current collector is not particularly limited, but since a metal foil is usually used for the current collector, a welding method that does not cause excessive damage to the metal foil is preferable. For example, a spot welding method, a laser welding method, and an ultrasonic welding method are mentioned as a welding method.

  As the welding method, an ultrasonic welding method is preferable. In ultrasonic welding, vibration is applied while applying moderate pressure to the joint surface, thereby inducing atomic diffusion and causing metal bonding. Since the oxide film and dirt on the metal surface before welding are destroyed and scattered by the initial vibration, the clean surfaces come into contact with each other to form a metal bond. Further, although the temperature of the metal surface that is in contact during welding rises, the metal does not melt during welding. Ultrasonic welding makes it easy to join dissimilar metals.

(First aspect)
In the first aspect, the positive electrode contact area with respect to the battery capacity or the negative electrode contact area with respect to the battery capacity is greater than 3 mm ² / Ah.

When the positive electrode contact area with respect to the battery capacity or the negative electrode contact area with respect to the battery capacity is larger than 3 mm ² / Ah, charge / discharge can be suitably performed even during charge / discharge at a high rate. At the time of charge / discharge of the lithium ion secondary battery, electrons move in each current collector, and electrons move between each current collector and each terminal through each contact point, and between each terminal and the outside of the battery. Electrons move between them. In the first aspect of the lithium ion secondary battery of the present invention, the positive electrode contact area with respect to the battery capacity or the negative electrode contact area with respect to the battery capacity is larger than 3 mm ² / Ah. It is estimated that the rise in On the other hand, if the positive electrode contact area with respect to the battery capacity or the negative electrode contact area with respect to the battery capacity is too small, the electronic resistance may increase and it may be difficult for electrons to move between each current collector and each terminal.

The positive electrode contact area with respect to the battery capacity or the negative electrode contact area with respect to the battery capacity is preferably 5 mm ² / Ah or more, more preferably 300 mm ² / Ah or more, and further preferably 2400 mm ² / Ah or more. preferable.

Moreover, there is no upper limit in particular in the positive electrode contact area with respect to battery capacity, or the negative electrode contact area with respect to battery capacity. However, in each lithium ion secondary battery, the positive electrode contact area or the negative electrode contact area is considered to be physically limited depending on the battery configuration. Therefore, if it dares restrict | limit, 50,000 mm < ² > / Ah or less and 20,000 mm < ² > / Ah or less can be illustrated as an upper limit of the positive electrode contact area with respect to battery capacity or the negative electrode contact area with respect to battery capacity.

  Here, the battery capacity means a maximum charge capacity or a maximum discharge capacity at which the lithium ion secondary battery can be stably charged and discharged. In order to calculate the battery capacity, for example, a discharge capacity obtained by discharging a lithium ion secondary battery charged at the maximum capacity assumed in actual use at a sufficiently low rate may be measured. The battery capacity is preferably 1 to 200 Ah, more preferably 3 to 100 Ah.

  The positive electrode contact area with respect to the battery capacity is the contact area between the positive electrode current collector and the positive electrode terminal divided by the battery capacity, and the negative electrode contact area with respect to the battery capacity is the negative electrode current collector and the negative electrode terminal. The contact area is divided by the battery capacity.

(Second aspect)
In the second aspect, the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion or the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion is 2% or more and 100% or less.

  At the time of charge and discharge of the lithium ion secondary battery, electrons move between each active material layer arrangement part and each active material layer non-arrangement part of each current collector, each active material layer non-arrangement part and each terminal, Electrons move between the terminals and between the terminals and the outside of the battery. In the second aspect of the lithium ion secondary battery of the present invention, the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion or the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion is 2%. Since it is 100% or less, it is estimated that an increase in electronic resistance can be suppressed even during high-rate charge / discharge. Conversely, if the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion or the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion is too small, the electronic resistance increases, There is a possibility that electrons are difficult to move between the material layer non-arranged portion and each terminal.

  A positive electrode active material layer is disposed on the surface of the positive electrode current collector, and a negative electrode active material layer is disposed on the surface of the negative electrode current collector. The part where each active material layer is arranged on the surface of each current collector is called a positive electrode active material layer arrangement part or a negative electrode active material layer arrangement part. Moreover, in the surface where each active material layer of each current collector is disposed, a portion where each active material layer is not disposed is referred to as a positive electrode active material layer non-arranged portion or a negative electrode active material layer non-arranged portion. . Each terminal is in contact with each active material layer non-arranged portion. In each current collector, the area of each active material layer non-arranged portion is obtained by subtracting the area of each active material layer arrangement portion from the area of the entire surface where the active material layer is arranged.

  The ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion or the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion is preferably 3% or more, and preferably 22% or more. Is more preferable.

  It is estimated that the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion or the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion is better from the viewpoint of electronic resistance. If the upper limit is restricted, the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion or the upper limit of the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion is 90% or less, 80 % Or less, 70% or less.

  Hereinafter, the lithium ion secondary battery of the present invention will be described with reference to FIG.

  In FIG. 1, the cross-sectional schematic diagram explaining the electrode group of the lithium ion secondary battery of this embodiment is shown. In FIG. 1, one electrode plate group 12 and an electrolyte solution (not shown) are arranged in a container 13. The electrolytic solution fills the space in the container 13 and also fills the gaps of the electrode plate group 12. The electrode plate group 12 includes a positive electrode 5, a negative electrode 10, and a separator 11 interposed therebetween. The positive electrode 5 includes a positive electrode current collector 1, a positive electrode active material layer 2 disposed on the surface of the positive electrode current collector 1, and a positive electrode terminal 3 that contacts the positive electrode current collector 1 at a contact surface 4. Have. The negative electrode 10 includes a negative electrode current collector 6, a negative electrode active material layer 7 disposed on the surface of the negative electrode current collector 6, a negative electrode terminal 8 that contacts the negative electrode current collector 6 at a contact surface 9, Have

  One end of the positive electrode terminal 3 is in contact with a positive electrode active material layer non-arranged portion in the positive electrode current collector 1 where the positive electrode active material layer 2 is not disposed, and exchanges electrons from the positive electrode 5 to the outside. . The other end of the positive electrode terminal 3 that is not in contact with the positive electrode current collector 1 is electrically connected to an external component (not shown). The other end of the positive electrode terminal 3 may be directly joined to an external component, or may be electrically connected to the external component via a conductive member.

  Similarly, one end of the negative electrode terminal 8 is in contact with the negative electrode active material layer non-arranged portion of the negative electrode current collector 6 where the negative electrode active material layer 7 is not disposed, and electrons from the negative electrode 10 to the outside are contacted. Give and receive. The other end of the negative electrode terminal 8 that is not in contact with the negative electrode current collector 6 is electrically connected to an external component (not shown). The other end of the negative electrode terminal 8 may be directly joined to an external component, or may be electrically connected to the external component via a conductive member.

  As other embodiments of the lithium ion secondary battery of the present invention, the other end of the positive electrode terminal that is not in contact with the positive electrode current collector, and the other end of the negative electrode terminal that is not in contact with the negative electrode current collector An embodiment in which the other end is in the container is mentioned. In that case, each other end is electrically connected to a conductive member communicating with the outside in the container.

  A plurality of electrode plate groups may be stacked in the container. Moreover, the active material layer may be formed on both surfaces of each current collector. A positive electrode having a positive electrode active material layer formed on both sides of the positive electrode current collector, a separator, and a negative electrode having a negative electrode active material layer formed on both sides of the negative electrode current collector are formed as a positive electrode, a separator, a negative electrode, a separator, and a positive electrode. Multiple layers may be laminated in the order of the separator and the negative electrode. Further, a flat plate-shaped positive electrode, a flat plate-shaped separator, and a flat plate-shaped negative electrode may be arranged in the container, or the positive electrode, the separator, and the negative electrode are rolled up in the container. May be arranged.

  The material and form of the container are not particularly limited. Examples of the material of the container include a resin and a metal. Examples of the form of the container include a can shape and a bag shape.

(Electrolyte)
Since the electrolytic solution (hereinafter sometimes referred to as the electrolytic solution of the present invention) included in the lithium ion secondary battery of the present invention has excellent ionic conductivity, the ionic resistance is small among the resistances that affect charging and discharging. Moreover, since the Li salt concentration of the electrolytic solution of the present invention is higher than that of a normal electrolytic solution, the supply amount of lithium ions from the electrolytic solution to the active material is larger than that of the normal electrolytic solution. Therefore, the electrolytic solution of the present invention has an effect of reducing the diffusion resistance among the resistances affecting the charging / discharging.

  The electrolytic solution of the present invention includes an electrolyte containing a lithium salt represented by the general formula (1) and an organic solvent containing a chain carbonate represented by the general formula (2). On the other hand, a chain carbonate is contained in a molar ratio of 3-6.

  The term “may be substituted with a substituent” in the chemical structure represented by the general formula (1) will be described. For example, in the case of “an alkyl group that may be substituted with a substituent”, an alkyl group in which one or more of the hydrogens of the alkyl group are substituted with a substituent, or an alkyl group that does not have a particular substituent Means.

  Examples of the substituent in the phrase “may be substituted with a substituent” include an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an unsaturated cycloalkyl group, an aromatic group, a heterocyclic group, a halogen, and OH. SH, CN, SCN, OCN, nitro group, alkoxy group, unsaturated alkoxy group, amino group, alkylamino group, dialkylamino group, aryloxy group, acyl group, alkoxycarbonyl group, acyloxy group, aryloxycarbonyl group, Acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, sulfinyl group, ureido group, phosphoric acid amide group, sulfo group, carboxyl group, Hydroxamic acid group, Rufino group, a hydrazino group, an imino group, and a silyl group. These substituents may be further substituted. Moreover, when there are two or more substituents, the substituents may be the same or different.

The lithium salt represented by the general formula (1) is preferably represented by the following general formula (1-1).
(R ³ X ² ) (R ⁴ SO ₂ ) NLi General formula (1-1)
(R ³ and R ⁴ are each independently C _n H _a F _b Cl _c Br _d I _e (CN) _f (SCN) _g (OCN) _h .
n, a, b, c, d, e, f, g, and h are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e + f + g + h.
R ³ and R ⁴ may combine with each other to form a ring, in which case 2n = a + b + c + d + e + f + g + h is satisfied.
X ^{2 _{is, SO 2, C = O,}} C = S, R c P = O, R d P = S, S = O, is selected from Si = O.
R ^c and R ^d are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a group that may be substituted with a substituent. A saturated alkyl group, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, a heterocyclic group that may be substituted with a substituent, and a substituent An alkoxy group which may be substituted, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, OH , SH, CN, SCN, and OCN.
R ^c and R ^d may combine with R ³ or R ⁴ to form a ring. )
The meaning of the phrase “may be substituted with a substituent” in the chemical structure represented by the general formula (1-1) is the same as described in the general formula (1).
In the chemical structure represented by the general formula (1-1), n is preferably an integer of 0 to 6, more preferably an integer of 0 to 4, and particularly preferably an integer of 0 to 2. Incidentally, the chemical structure represented by the general formula (1-1), ^{when R 3} and ^{R 4} are joined to form a ring, n is preferably an integer of 1 to 8, 1 to 7 Is more preferable, and an integer of 1 to 3 is particularly preferable.

The lithium salt represented by the general formula (1) is more preferably represented by the following general formula (1-2).
(R ⁵ SO ₂ ) (R ⁶ SO ₂ ) NLi Formula (1-2)
(R ⁵ and R ⁶ are each independently C _n H _a F _b Cl _c Br _d I _e .
n, a, b, c, d, and e are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e.
R ⁵ and R ⁶ may combine with each other to form a ring, in which case 2n = a + b + c + d + e is satisfied. )
In the chemical structure represented by the general formula (1-2), n is preferably an integer of 0 to 6, more preferably an integer of 0 to 4, and particularly preferably an integer of 0 to 2. Incidentally, the chemical structure represented by the general formula (1-2), ^{when R 5} and ^{R 6} are joined to form a ring, n is preferably an integer of 1 to 8, 1 to 7 Is more preferable, and an integer of 1 to 3 is particularly preferable.
In the chemical structure represented by the general formula (1-2), those in which a, c, d, and e are 0 are preferable.

The lithium salt represented by the general formula (1) may be referred to as (CF ₃ SO ₂ ) ₂ NLi (hereinafter sometimes referred to as “LiTFSA”) or (FSO ₂ ) ₂ NLi (hereinafter referred to as “LiFSA”). ), (C ₂ F ₅ SO ₂ ) ₂ NLi, FSO ₂ (CF ₃ SO ₂ ) NLi, (SO ₂ CF ₂ CF ₂ SO ₂ ) NLi, (SO ₂ CF ₂ CF ₂ CF ₂ SO ₂ ) NLi, FSO ₂ (CH ₃ SO ₂ ) NLi, FSO ₂ (C ₂ F ₅ SO ₂ ) NLi, or FSO ₂ (C ₂ H ₅ SO ₂ ) NLi is particularly preferred.

  One type of lithium salt represented by the general formula (1) in the electrolytic solution of the present invention may be used, or a plurality of types may be used in combination.

  The electrolyte in the electrolytic solution of the present invention may contain other electrolytes that can be used in an electrolytic solution such as a lithium ion secondary battery, in addition to the lithium salt represented by the general formula (1).

Examples of other electrolytes include LiXO ₄ , LiAsX ₆ , LiPX ₆ , LiBX ₄ , and LiB (C ₂ O ₄ ) ₂ (wherein X independently represents F, Cl, Br, I, or CN). Is preferred. As a suitable aspect of LiXO ₄ , LiAsX ₆ , LiPX ₆ , LiBX ₄ , LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiBF _y (CN) _z (where y is an integer of 0 to 3, z is 1) It is an integer of ˜4 and satisfies y + z = 4).

  In the electrolytic solution of the present invention, the lithium salt represented by the general formula (1) is preferably contained in an amount of 70% by mass or more or 70% by mol or more based on the total electrolyte contained in the electrolytic solution of the present invention. More preferably, it is contained at 80% by weight or more or 80% by mole or more, more preferably 90% by weight or more or 90% by mole or more, and particularly preferably 95% by weight or more or 95% by mole or more. . All of the electrolyte contained in the electrolytic solution of the present invention may be a lithium salt represented by the general formula (1).

The chemical structure of the lithium salt represented by the general formula (1) includes SO ₂ . And by charging / discharging of the lithium ion secondary battery of this invention, a part of lithium salt represented by General formula (1) decomposes | disassembles, and S and O contain on the surface of the positive electrode and / or negative electrode of a secondary battery A film is formed. The S and O containing coating is presumed to have an S = O structure. Since the electrode is covered with the coating, deterioration of the electrode and the electrolytic solution is suppressed, and as a result, the durability of the lithium ion secondary battery of the present invention is considered to be improved.

  In the electrolytic solution of the present invention, the cation and the anion of the lithium salt are present nearer than the conventional electrolytic solution, and the anion is strongly affected by the electrostatic effect from the cation, so that it is compared with the conventional electrolytic solution. It is thought that it becomes easy to carry out reductive decomposition. In a conventional secondary battery using a conventional electrolyte, a SEI coating (Solid Electrolyte Interface) is formed by a decomposition product generated by reducing and decomposing cyclic carbonates such as ethylene carbonate contained in the electrolyte. . However, as described above, in the electrolytic solution of the present invention contained in the lithium ion secondary battery of the present invention, the anion is easily reduced and decomposed, and the lithium salt is contained at a higher concentration than the conventional electrolytic solution. In addition, the anion concentration in the electrolyte is high. For this reason, it is considered that the SEI coating, that is, the S and O-containing coating in the lithium ion secondary battery of the present invention contains a large amount derived from anions. In the lithium ion secondary battery of the present invention, the SEI film can be formed without using a cyclic carbonate such as ethylene carbonate.

  The S and O-containing coating may be formed only on the negative electrode surface, or may be formed only on the positive electrode surface. The S and O-containing coating is preferably formed on both the negative electrode surface and the positive electrode surface.

  The lithium ion secondary battery of the present invention has an S and O-containing coating on the electrode, and the S and O-containing coating has an S═O structure and contains many lithium ions. And it is thought that the lithium ion contained in a coating film containing S and O is preferentially supplied to the electrode. Therefore, since the lithium ion secondary battery of the present invention has an abundant lithium ion source in the vicinity of the electrode, it is considered that the transport rate of lithium ions is improved also in this respect. Therefore, in the lithium ion secondary battery of this invention, it is thought that the outstanding battery characteristic is exhibited by cooperation with the electrolyte solution of this invention, and the S and O containing film of an electrode.

The electrolytic solution of the present invention contains an organic solvent containing a chain carbonate represented by the general formula (2).
R ²⁰ OCOOR ²¹ general formula (2)
(R ²⁰ and R ²¹ each independently represent C _n H _a F _b Cl _c Br _d I _e which is a chain alkyl, or C _m H _f F _g Cl _h Br _i I containing a cyclic alkyl in the chemical structure. selected from _j , n is an integer of 1 or more, m is an integer of 3 or more, a, b, c, d, e, f, g, h, i, j are each independently an integer of 0 or more 2n + 1 = a + b + c + d + e, 2m = f + g + h + i + j is satisfied.)
In the chain carbonate represented by the general formula (2), n is preferably an integer of 1 to 6, more preferably an integer of 1 to 4, and particularly preferably an integer of 1 to 2. m is preferably an integer of 3 to 8, more preferably an integer of 4 to 7, and particularly preferably an integer of 5 to 6.

Of the chain carbonates represented by the general formula (2), those represented by the following general formula (2-1) are particularly preferred.
R ²² OCOOR ²³ general formula (2-1)
(R ²² and R ²³ are each independently selected from either C _n H _a F _b which is a chain alkyl or C _m H _f F _g containing a cyclic alkyl in the chemical structure. N is 1 (The above integers, m is an integer of 3 or more, and a, b, f, and g are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b and 2m = f + g.)
In the chain carbonate represented by the general formula (2-1), n is preferably an integer of 1 to 6, more preferably an integer of 1 to 4, and particularly preferably an integer of 1 to 2. m is preferably an integer of 3 to 8, more preferably an integer of 4 to 7, and particularly preferably an integer of 5 to 6.

  Among the chain carbonates represented by the general formula (2-1), dimethyl carbonate (hereinafter sometimes referred to as “DMC”), diethyl carbonate (hereinafter sometimes referred to as “DEC”), ethylmethyl Carbonate (hereinafter sometimes referred to as "EMC"), fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, bis (difluoromethyl) carbonate, bis (trifluoromethyl) Carbonate, fluoromethyldifluoromethyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, pentafluoroethyl methyl carbonate, ethyl trifluoromethyl carbonate, bis (2,2,2-trifluoroethyl) ) Carbonate is particularly preferred.

  One kind of the chain carbonate described above may be used for the electrolyte solution, or a plurality of the chain carbonates may be used in combination. By using a plurality of chain carbonates in combination, it is possible to suitably ensure the low temperature fluidity of the electrolyte and the lithium ion transportability at low temperatures.

  In addition to the chain carbonate, the organic solvent in the electrolytic solution of the present invention may be another organic solvent that can be used in an electrolytic solution such as a lithium ion secondary battery (hereinafter simply referred to as “other organic solvent”). .) May be included.

  In the electrolytic solution of the present invention, the chain carbonate is preferably contained in an amount of 70% by mass or more or 70% by mol or more, based on the total organic solvent contained in the electrolytic solution of the present invention. More preferably, it is contained in an amount of not less than mol%, more preferably not less than 90% by mass or not less than 90% by mol, and particularly preferably not less than 95% by mass or not less than 95% by mol. All the organic solvents contained in the electrolytic solution of the present invention may be the chain carbonate.

  In addition, the electrolytic solution of the present invention containing other organic solvents in addition to the chain carbonate has a higher viscosity or lower ionic conductivity than the electrolytic solution of the present invention that does not contain other organic solvents. There is a case. Furthermore, the reaction resistance of the secondary battery using the electrolytic solution of the present invention containing another organic solvent in addition to the chain carbonate may increase.

  Specific examples of other organic solvents include nitriles such as acetonitrile, propionitrile, acrylonitrile, malononitrile, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane, 1, Ethers such as 3-dioxane, 1,4-dioxane, 2,2-dimethyl-1,3-dioxolane, 2-methyltetrahydropyran, 2-methyltetrahydrofuran and crown ether, and cyclic carbonates such as ethylene carbonate and propylene carbonate Amides such as formamide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, isocyanates such as isopropyl isocyanate, n-propyl isocyanate, chloromethyl isocyanate, , Ethyl acetate, propyl acetate, butyl acetate, methyl propionate, methyl formate, ethyl formate, vinyl acetate, methyl acrylate, methyl methacrylate, and other esters, glycidyl methyl ether, epoxy butane, 2-ethyloxirane, and other epoxies, Oxazoles such as oxazole, 2-ethyloxazole, oxazoline, 2-methyl-2-oxazoline, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acid anhydrides such as acetic anhydride and propionic anhydride, dimethyl sulfone, sulfolane, etc. Sulfones, sulfoxides such as dimethyl sulfoxide, nitros such as 1-nitropropane and 2-nitropropane, furans such as furan and furfural, γ-butyrolactone, γ-valerolactone, δ-valerolactone Cyclic esters, aromatic heterocycles such as thiophene and pyridine, heterocycles such as tetrahydro-4-pyrone, 1-methylpyrrolidine and N-methylmorpholine, phosphate esters such as trimethyl phosphate and triethyl phosphate There can be mentioned.

  The chain carbonate represented by the general formula (2) has a lower polarity than cyclic carbonates such as ethylene carbonate that have been used in conventional electrolyte solutions. Therefore, it is considered that the affinity between the chain carbonate and the metal ion is inferior to the affinity between the cyclic carbonate and the metal ion. Then, when the electrolytic solution of the present invention is used as an electrolytic solution for a secondary battery, it is difficult for the aluminum and transition metal constituting the electrode of the secondary battery to dissolve as ions in the electrolytic solution of the present invention. It can be said that there is.

  Here, in the conventional secondary battery using a general electrolytic solution, aluminum and transition metal constituting the positive electrode are in a highly oxidized state particularly in a high voltage charging environment, and the electrolytic solution is used as a metal ion which is a cation. When the metal ions dissolved in the electrolyte (anode elution) and attracted to the electron-rich negative electrode due to electrostatic attraction and are combined with electrons on the negative electrode are reduced and deposited as metal It is known that there is. It is known that when such a reaction occurs, the capacity of the positive electrode may be reduced or the electrolytic solution may be decomposed on the negative electrode. However, since the electrolytic solution of the present invention has the characteristics described in the previous paragraph, in the secondary battery using the electrolytic solution of the present invention, elution of metal ions from the positive electrode and metal deposition on the negative electrode are suppressed.

  In the electrolytic solution of the present invention, the chain carbonate represented by the general formula (2) is contained in a molar ratio of 3 to 6 with respect to the lithium salt represented by the general formula (1). The ionic conductivity of the electrolytic solution of the present invention is suitable if the molar ratio is within the above range. In the present specification, the molar ratio is a value obtained by dividing the former by the latter, that is, (the number of moles of the chain carbonate represented by the general formula (2) contained in the electrolytic solution of the present invention) / (the present invention. The number of moles of the lithium salt represented by the general formula (1) contained in the electrolyte solution (hereinafter, sometimes simply referred to as “chain carbonate / lithium salt molar ratio”). As a more preferable molar ratio in the electrolytic solution of the present invention, a range of 4 to 5.5, a range of 3.2 to 4.8, and a range of 3.5 to 4.5 can be exemplified. In addition, the conventional electrolyte solution has a molar ratio of the organic solvent to the electrolyte of about 10.

  In the electrolytic solution of the present invention, the concentration of the lithium salt is higher than that of the conventional electrolytic solution. Furthermore, the electrolytic solution of the present invention has an advantage that the fluctuation of the ionic conductivity is small with respect to a slight fluctuation of the lithium salt concentration, that is, it is excellent in robustness. Moreover, the chain carbonate represented by the general formula (2) is excellent in stability against oxidation and reduction. In addition, the chain carbonate represented by the general formula (2) has many free-rotatable bonds and has a flexible chemical structure. Therefore, the electrolytic solution of the present invention using the chain carbonate has a high concentration. Even when a lithium salt at a concentration is contained, a significant increase in the viscosity is suppressed, and high ionic conductivity can be obtained.

  In addition, it can be said that the electrolytic solution of the present invention is different from the conventional electrolytic solution in the presence environment of the lithium salt and the organic solvent. Therefore, in the lithium ion secondary battery comprising the electrolytic solution of the present invention, the lithium ion transport rate in the electrolytic solution is improved, the reaction rate at the interface between the electrode and the electrolytic solution is improved, and the secondary battery is charged and discharged at a high rate. It can be expected to ease the uneven distribution of the lithium salt concentration of the electrolytic solution, to improve the liquid retention of the electrolytic solution at the electrode interface, and to suppress the so-called withered state where the electrolytic solution is insufficient at the electrode interface. Furthermore, in the electrolytic solution of the present invention, the vapor pressure of the organic solvent contained in the electrolytic solution is lowered. As a result, volatilization of the organic solvent from the electrolytic solution of the present invention can be reduced.

  In the electrolytic solution of the present invention, the distance between adjacent lithium ions is extremely close. When lithium ions move between the positive electrode and the negative electrode during charging / discharging of the secondary battery, the lithium ions closest to the destination electrode are first supplied to the electrode. Then, another lithium ion adjacent to the lithium ion moves to the place where the supplied lithium ion was present. That is, in the electrolyte solution of the present invention, it is expected that a domino-like phenomenon occurs in which adjacent lithium ions change their positions one by one toward the electrode to be supplied. For this reason, it is thought that the movement distance of the lithium ion at the time of charging / discharging is short, and the movement speed of the lithium ion is high correspondingly. And it originates in this and it is thought that the reaction rate of the secondary battery which has the electrolyte solution of this invention is high.

The density d (g / cm ³ ) of the electrolytic solution of the present invention will be described. In addition, in this specification, a density means the density in 20 degreeC. The density d (g / cm ³ ) of the electrolytic solution of the present invention is preferably 1.0 ≦ d, and more preferably 1.1 ≦ d.

For reference, typical organic solvent densities (g / cm ³ ) are listed in Table 1.

  Regarding the viscosity η (mPa · s) of the electrolytic solution of the present invention, a range of 3 <η <50 is preferable, a range of 4 <η <40 is more preferable, and a range of 5 <η <30 is more preferable.

  Further, the higher the ionic conductivity σ (mS / cm) of the electrolytic solution, the easier the ions move in the electrolytic solution. For this reason, such an electrolyte can be an excellent battery electrolyte. The ion conductivity σ (mS / cm) of the electrolytic solution of the present invention is preferably 1 ≦ σ. Regarding the ionic conductivity σ (mS / cm) of the electrolytic solution of the present invention, when a suitable range including the upper limit is shown, a range of 2 ≦ σ <100 is preferable, and a range of 3 ≦ σ <50 is more preferable. A range of 4 ≦ σ <30 is more preferable.

  When the electrolytic solution of the present invention is mixed with a polymer or an inorganic filler to form a mixture, the mixture contains the electrolytic solution and becomes a pseudo solid electrolyte. By using the pseudo-solid electrolyte as the battery electrolyte, leakage of the electrolyte in the battery can be suppressed.

  As said polymer, the polymer used for batteries, such as a lithium ion secondary battery, and the general chemically crosslinked polymer are employable. In particular, a polymer that can absorb an electrolyte such as polyvinylidene fluoride and polyhexafluoropropylene to gel, or a polymer such as polyethylene oxide in which an ion conductive group is introduced is preferable.

  Specific polymers include polymethyl acrylate, polymethyl methacrylate, polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyvinylidene fluoride, polyethylene glycol dimethacrylate, polyethylene glycol acrylate, polyglycidol, polytetrafluoroethylene, polyhexafluoropropylene, Polycarboxylic acid such as polysiloxane, polyvinyl acetate, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyitaconic acid, polyfumaric acid, polycrotonic acid, polyangelic acid, carboxymethylcellulose, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene , Polycarbonate, unsaturated polyester copolymerized with maleic anhydride and glycols, substituted It can be exemplified polyethylene oxide derivative, a copolymer of vinylidene fluoride and hexafluoropropylene having. Further, as the polymer, a copolymer obtained by copolymerizing two or more monomers constituting the specific polymer may be selected.

  Polysaccharides are also suitable as the polymer. Specific examples of the polysaccharide include glycogen, cellulose, chitin, agarose, carrageenan, heparin, hyaluronic acid, pectin, amylopectin, xyloglucan, and amylose. Moreover, you may employ | adopt the material containing these polysaccharides as said polymer, The agar containing polysaccharides, such as agarose, can be illustrated as the said material.

  As said inorganic filler, inorganic ceramics, such as an oxide and nitride, are preferable.

  Inorganic ceramics have hydrophilic and hydrophobic functional groups on their surfaces. Therefore, when the functional group attracts the electrolytic solution, a conductive path can be formed in the inorganic ceramic. Furthermore, the inorganic ceramics dispersed in the electrolytic solution can form a network between the inorganic ceramics by the functional groups and serve to contain the electrolytic solution. With such a function of the inorganic ceramics, it is possible to more suitably suppress the leakage of the electrolytic solution in the battery. In order to suitably exhibit the above functions of the inorganic ceramics, the inorganic ceramics preferably have a particle shape, and particularly preferably have a particle size of nano level.

Examples of the inorganic ceramics include general alumina, silica, titania, zirconia, and lithium phosphate. It is also possible but the inorganic ceramic itself has lithium conductivity, _{specifically, Li 3 N, LiI, LiI} -Li 3 N-LiOH, LiI-Li 2 S-P 2 O 5, LiI-Li 2 S _{-P 2 S 5, LiI-Li} 2 S-B 2 S 3, Li 2 O-B 2 S 3, Li 2 O-V 2 O 3 -SiO 2, Li 2 O-B 2 O 3 -P 2 O ₅ , Li ₂ O—B ₂ O ₃ —ZnO, Li ₂ O—Al ₂ O ₃ —TiO ₂ —SiO ₂ —P ₂ O ₅ , LiTi ₂ (PO ₄ ) ₃ , Li-βAl ₂ O ₃ , LiTaO ₃ Can be illustrated.

Glass ceramics may be employed as the inorganic filler. Since glass ceramics can contain an ionic liquid, the same effect can be expected for the electrolytic solution of the present invention. Things as glass _{ceramics, xLi 2 S- (1-x} ) P 2 S 5 ( however, 0 <x <1) compound represented by the well, obtained by replacing a part of S of the compound with other elements And what substituted a part of P of the said compound by germanium can be illustrated.

  Moreover, you may add a well-known additive to the electrolyte solution of this invention in the range which does not deviate from the meaning of this invention. Examples of known additives include cyclic carbonates having unsaturated bonds typified by vinylene carbonate (VC), vinyl ethylene carbonate (VEC), methyl vinylene carbonate (MVC), and ethyl vinylene carbonate (EVC); fluoroethylene carbonate, Carbonate compounds represented by trifluoropropylene carbonate, phenylethylene carbonate and erythritan carbonate; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic acid Carboxylic anhydrides represented by acid anhydrides, cyclopentanetetracarboxylic dianhydrides, phenylsuccinic anhydrides; γ-butyrolactone, γ-valerolactone, γ-caprolac , Lactones represented by δ-valerolactone, δ-caprolactone, ε-caprolactone; cyclic ethers represented by 1,4-dioxane; ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, methane Sulfur-containing compounds typified by methyl sulfonate, busulfan, sulfolane, sulfolene, dimethyl sulfone, tetramethylthiuram monosulfide; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, Nitrogen-containing compounds typified by 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide; phosphates typified by monofluorophosphate and difluorophosphate; typified by heptane, octane and cycloheptane Saturated hydrocarbon compounds; biphenyl, al Le biphenyl, terphenyl, partially hydrogenated embodying terphenyl, cyclohexylbenzene, t- butyl benzene, t-amyl benzene, diphenyl ether, unsaturated hydrocarbon compounds and the like typified by dibenzofuran.

  Next, the positive electrode, the negative electrode, and the separator will be described.

(Positive electrode)
The positive electrode has a positive electrode current collector, a positive electrode active material layer disposed on the surface of the positive electrode current collector, and a positive electrode terminal that contacts the surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material and, if necessary, a binder and / or a conductive aid.

  The positive electrode current collector and the positive electrode terminal have been described above.

(Positive electrode active material)
As the positive electrode active material, a material capable of inserting and extracting lithium ions can be used. For example, as a positive electrode active material, a layered compound Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1.2, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr Cu, Zn, Ca, Mg, S, Si, Na, K, Al, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W, La, at least one element, 1.7 ≦ f ≦ 2.1) and Li ₂ MnO ₃ . Further, as a positive electrode active material, a metal oxide having a spinel structure such as LiMn ₂ O ₄ and a solid solution composed of a mixture of a metal oxide having a spinel structure and a layered compound, LiMPO ₄ , LiMVO _4, or Li ₂ MSiO ₄ (formula M in the middle is selected from at least one of Co, Ni, Mn, and Fe). Furthermore, as the positive electrode active material, tavorite compound (the M a transition metal) LiMPO ₄ F, such as LiFePO ₄ F represented by, Limbo ₃ such LiFeBO ₃ (M is a transition metal) include borate-based compound represented by be able to. Any metal oxide used as the positive electrode active material may have the above composition formula as a basic composition, and a metal element contained in the basic composition may be substituted with another metal element. Moreover, you may use as a positive electrode active material the thing which does not contain a charge carrier (for example, lithium ion which contributes to charging / discharging). For example, sulfur alone (S), a compound in which sulfur and carbon are compounded, a metal sulfide such as TiS ₂ , an oxide such as V ₂ O ₅ and MnO ₂ , a compound containing polyaniline and anthraquinone, and these aromatics in the chemical structure In addition, conjugated materials such as conjugated diacetate-based organic substances and other known materials can also be used. Further, a compound having a stable radical such as nitroxide, nitronyl nitroxide, galvinoxyl, phenoxyl, etc. may be adopted as the positive electrode active material. When using a positive electrode active material that does not contain a charge carrier such as lithium, it is necessary to add a charge carrier to the positive electrode and / or the negative electrode in advance by a known method. The charge carrier may be added in an ionic state or in a non-ionic state such as a metal. For example, when the charge carrier is lithium, it may be integrated by attaching a lithium foil to the positive electrode and / or the negative electrode.

As specific positive electrode active materials, LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ having a layered rock salt structure, LiNi _0.5 Mn _0. Examples include ₅ O ₂ , LiNi _0.75 Co _0.1 Mn _0.15 O ₂ , LiMnO ₂ , LiNiO ₂ , and LiCoO ₂ . As another specific positive electrode active material, Li ₂ MnO ₃ —LiCoO ₂ can be exemplified.

Specific positive electrode active _{material, Li x A y Mn 2-} y O 4 (A spinel structure, Ca, Mg, S, Si , Na, K, Al, P, Ga, at least one selected from Ge An element and / or at least one metal element selected from transition metal elements, such as 0 <x ≦ 2.2 and 0 ≦ y ≦ 1). More specifically, LiMn ₂ O ₄ and LiNi _0.5 Mn _1.5 O ₄ can be exemplified.

Specific examples of the positive electrode active material include LiFePO ₄ , Li ₂ FeSiO ₄ , LiCoPO ₄ , Li ₂ CoPO ₄ , Li ₂ MnPO ₄ , Li ₂ MnSiO ₄ , and Li ₂ CoPO ₄ F.

From the viewpoint of excellent and high capacity, and durability, as the positive electrode active material, the general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, At least one element selected from Rh, Zr, Fe, Ge, Zn, Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P, V, 1.7 ≦ f ≦ 3) It is preferable to employ the lithium composite metal oxide represented.

In the above general formula, the values of b, c, and d are not particularly limited as long as the above conditions are satisfied, but those in which 0 <b <1, 0 <c <1, 0 <d <1 are satisfied. And at least one of b, c, and d is in the range of 10/100 <b <90/100, 10/100 <c <90/100, 5/100 <d <70/100. More preferably, the ranges are 20/100 <b <80/100, 12/100 <c <70/100, 10/100 <d <60/100, 30/100 <b <70/100, More preferably, the ranges are 15/100 <c <50/100 and 12/100 <d <50/100.
About a, e, and f, what is necessary is just a numerical value within the range prescribed | regulated by the said general formula, Preferably 0.5 <= a <= 1.5, 0 <= e <0.2, 1.8 <= f <= 2 0.5, more preferably 0.8 ≦ a ≦ 1.3, 0 ≦ e <0.1, 1.9 ≦ f ≦ 2.1, respectively.

  The average particle diameter of the positive electrode active material is preferably in the range of 1 μm to 20 μm, more preferably in the range of 2 μm to 15 μm, and still more preferably in the range of 3 μm to 10 μm. In addition, an average particle diameter means D50 at the time of measuring with a general laser diffraction scattering type particle size distribution measuring apparatus.

The positive electrode active material is preferably in the range BET specific surface area of 0.1m ² / g~5m ² / ^g, more preferably in the range of ^{0.2m 2 / g~3m 2 / g,} 0.3m 2 Those having a range of / g to ² m ² / g are more preferable.

  In the positive electrode active material layer, the positive electrode active material is preferably contained in the range of 70% by mass to 100% by mass, more preferably in the range of 80% by mass to 99% by mass, and 88% by mass to More preferably, it is contained within the range of 98% by mass, and particularly preferably within the range of 92% by mass to 97% by mass.

  Hereinafter, the binder and the conductive additive for both the positive electrode and the negative electrode will be described.

(Binder)
The binder plays a role of tying an active material, a conductive aid, and the like to the surface of the current collector.

  Binders include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, and styrene butadiene. What is necessary is just to employ | adopt well-known things, such as rubber | gum.

  Moreover, you may employ | adopt the polymer which has a hydrophilic group as a binder. The lithium ion secondary battery of the present invention comprising a polymer having a hydrophilic group as a binder for the negative electrode may be able to maintain the capacity more suitably. Examples of the hydrophilic group of the polymer having a hydrophilic group include a phosphate group such as a carboxyl group, a sulfo group, a silanol group, an amino group, a hydroxyl group, and a phosphate group. Among them, a polymer containing a carboxyl group in a molecule such as polyacrylic acid, carboxymethylcellulose, or polymethacrylic acid, or a polymer containing a sulfo group such as poly (p-styrenesulfonic acid) is preferable.

  A polymer containing many carboxyl groups and / or sulfo groups such as polyacrylic acid or a copolymer of acrylic acid and vinyl sulfonic acid becomes water-soluble. The polymer having a hydrophilic group is preferably a water-soluble polymer, and in terms of chemical structure, a polymer containing a plurality of carboxyl groups and / or sulfo groups in one molecule is preferable.

  The polymer containing a carboxyl group in the molecule can be produced by, for example, a method of polymerizing an acid monomer or a method of imparting a carboxyl group to the polymer. Acid monomers include acrylic acid, methacrylic acid, vinyl benzoic acid, crotonic acid, pentenoic acid, angelic acid, tiglic acid, etc., acid monomers having one carboxyl group in the molecule, itaconic acid, mesaconic acid, citraconic acid, fumaric acid , Maleic acid, 2-pentenedioic acid, methylene succinic acid, allyl malonic acid, isopropylidene succinic acid, 2,4-hexadiene diacid, acetylenedicarboxylic acid, etc., acid monomers having two or more carboxyl groups in the molecule Is done.

  A copolymer obtained by polymerizing two or more acid monomers selected from the above acid monomers may be used as a binder.

  Further, for example, a polymer containing an acid anhydride group formed by condensation of carboxyl groups of a copolymer of acrylic acid and itaconic acid, as described in JP 2013-065493 A, in the molecule It is also preferable to use as a binder. When the binder has a structure derived from a highly acidic monomer having two or more carboxyl groups in one molecule, it becomes easier for the binder to trap lithium ions etc. before the electrolyte decomposition reaction occurs during charging. It is considered. Furthermore, since the polymer has more carboxyl groups per monomer than polyacrylic acid or polymethacrylic acid, the acidity is increased, but since the predetermined amount of carboxyl groups is changed to acid anhydride groups, the acidity is increased. Is not too high. Therefore, the lithium ion secondary battery of the present invention having a negative electrode using the polymer as a binder has improved initial efficiency and improved input / output characteristics.

  The blending ratio of the binder in the active material layer is preferably a mass ratio of active material: binder = 1: 0.005 to 1: 0.3. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.

(Conductive aid)
The conductive assistant is added to increase the conductivity of the electrode. Therefore, the conductive auxiliary agent may be added arbitrarily when the electrode conductivity is insufficient, and may not be added when the electrode conductivity is sufficiently excellent. The conductive auxiliary agent may be any chemically inert electronic high conductor such as carbon black, graphite, vapor grown carbon fiber (VGCF), and various metal particles. Illustrated. Examples of carbon black include acetylene black, ketjen black (registered trademark), furnace black, and channel black. These conductive assistants can be added to the active material layer alone or in combination of two or more. The blending ratio of the conductive assistant in the active material is preferably a mass ratio of active material: conductive assistant = 1: 0.01 to 1: 0.5. This is because if the amount of the conductive aid is too small, an efficient conductive path cannot be formed, and if the amount of the conductive aid is too large, the formability of the negative electrode active material layer is deteriorated and the energy density of the electrode is lowered.

  In addition, a conductive aid having a shape such as a fiber shape, a scale shape, or a plate shape (hereinafter, these shapes may be collectively referred to as “non-spherical”) or a non-spherical conductive aid may be used. It is preferable to use together with the conductive auxiliary. If it is a non-spherical conductive support agent, a long conductive path can be ensured compared with a spherical conductive support agent. Therefore, in a preferred embodiment of the lithium ion secondary battery of the present invention that prescribes that the thickness of the active material layer is thick, more suitable charge / discharge can be achieved by employing a non-spherical conductive assistant. .

  The average particle size of the non-spherical conductive assistant is preferably in the range of 1 μm to 30 μm, and more preferably in the range of 2 μm to 20 μm. In addition, an average particle diameter means D50 at the time of measuring with a general laser diffraction scattering type particle size distribution measuring apparatus. Non-spherical means that when the conductive additive is represented in three dimensions of the X axis, the Y axis, and the Z axis, the longest length with respect to the minimum length in the lengths a, b, and c in each axial direction. It means that the ratio of is 2 or more.

(Negative electrode)
The negative electrode has a negative electrode current collector, a negative electrode active material layer disposed on the surface of the negative electrode current collector, and a negative electrode terminal in contact with the surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material and, if necessary, a binder and / or a conductive aid.

  The negative electrode current collector and the negative electrode terminal have been described above.

(Negative electrode active material)
As the negative electrode active material, a material capable of inserting and extracting lithium ions can be used. Accordingly, there is no particular limitation as long as it is a simple substance, alloy, or compound that can occlude and release lithium ions. For example, as a negative electrode active material, Li, group 14 elements such as carbon, silicon, germanium and tin, group 13 elements such as aluminum and indium, group 12 elements such as zinc and cadmium, group 15 elements such as antimony and bismuth, magnesium , Alkaline earth metals such as calcium, and group 11 elements such as silver and gold may be employed alone. When silicon or the like is used for the negative electrode active material, a silicon atom reacts with a plurality of lithiums, so that it becomes a high-capacity active material. However, there is a problem that volume expansion and contraction due to insertion and extraction of lithium becomes significant. In order to reduce the fear, it is also preferable to employ an alloy or compound in which another element such as a transition metal is combined with a simple substance such as silicon as the negative electrode active material. Specific examples of the alloy or compound include tin-based materials such as Ag-Sn alloy, Cu-Sn alloy, Co-Sn alloy, carbon-based materials such as various graphites, SiO _x (disproportionated to silicon simple substance and silicon dioxide). Examples thereof include silicon-based materials such as 0.3 ≦ x ≦ 1.6), silicon alone, or composites obtained by combining silicon-based materials and carbon-based materials. In addition, as the negative electrode active material, oxides such as Nb ₂ O ₅ , TiO ₂ , Li ₄ Ti ₅ O ₁₂ , WO ₂ , MoO ₂ , Fe ₂ O ₃ , or Li _3-x M _x N (M = A nitride represented by (Co, Ni, Cu) may be employed. One or more of these materials can be used as the negative electrode active material.

  In view of the possibility of increasing the capacity, preferred negative electrode active materials include graphite, silicon-based materials, and tin-based materials.

As a more specific negative electrode active material, graphite having a G / D ratio of 3.5 or more can be exemplified. The G / D ratio is a ratio of G-band and D-band peaks in a Raman spectrum. In the Raman spectrum of graphite, G-band 'is in the vicinity of 1590cm ^-1, D-band is observed as each peak around 1350 cm ^-1. G-band is derived from a graphite structure, and D-band is derived from a defect. Therefore, the higher the G / D ratio, which is the ratio of G-band and D-band, means that the graphite has fewer defects and higher crystallinity. Hereinafter, graphite having a G / D ratio of 3.5 or more may be referred to as high crystalline graphite, and graphite having a G / D ratio of less than 3.5 may be referred to as low crystalline graphite.

  As the highly crystalline graphite, either natural graphite or artificial graphite can be employed. In the classification method by shape, scaly graphite, spherical graphite, massive graphite, earthy graphite, etc. can be adopted. Also, coated graphite in which the surface of graphite is coated with a carbon material or the like can be employed.

  As a specific negative electrode active material, a carbon material having a crystallite size of 20 nm or less, preferably 5 nm or less can be exemplified. A larger crystallite size means a carbon material in which atoms are arranged periodically and accurately according to a certain rule. On the other hand, it can be said that a carbon material having a crystallite size of 20 nm or less is in a state of poor atomic periodicity and alignment accuracy. For example, if the carbon material is graphite, the size of the graphite crystal is 20 nm or less, or due to the influence of strain, defects, impurities, etc., the regularity of the arrangement of the atoms constituting the graphite becomes poor. The size is 20 nm or less.

  Typical examples of the carbon material having a crystallite size of 20 nm or less include non-graphitizable carbon that is so-called hard carbon and graphitizable carbon that is so-called soft carbon.

In order to measure the crystallite size of the carbon material, an X-ray diffraction method using CuKα rays as an X-ray source may be used. With the X-ray diffraction method, the crystallite size can be calculated using the following Scherrer equation based on the half-value width and diffraction angle of the diffraction peak detected at the diffraction angle 2θ = 20 degrees to 30 degrees.
L = 0.94λ / (βcosθ)
here,
L: Crystallite size λ: Incident X-ray wavelength (1.54 mm)
β: half width of peak (radian)
θ: Diffraction angle

As a specific negative electrode active material, a material containing silicon can be exemplified. More specifically, SiO _x (0.3 ≦ x ≦ 1.6) disproportionated into two phases of Si phase and silicon oxide phase can be exemplified. The Si phase in SiO _x can occlude and release lithium ions, and changes in volume as the secondary battery is charged and discharged. The silicon oxide phase has less volume change associated with charge / discharge than the Si phase. That is, SiO _x as the negative electrode active material realizes a high capacity by the Si phase and suppresses the volume change of the entire negative electrode active material by having the silicon oxide phase. If x is less than the lower limit value, the Si ratio becomes excessive, so that the volume change during charging and discharging becomes too large, and the cycle characteristics of the secondary battery deteriorate. On the other hand, when x exceeds the upper limit value, the Si ratio becomes too small and the energy density decreases. The range of x is more preferably 0.5 ≦ x ≦ 1.5, and further preferably 0.7 ≦ x ≦ 1.2.

In the SiO _x as described above, it is believed to alloying reaction with the silicon lithium and Si phase during charging and discharging of the lithium ion secondary battery may occur. And it is thought that this alloying reaction contributes to charging / discharging of a lithium ion secondary battery. Similarly, it is considered that a negative electrode active material containing tin described later can be charged and discharged by an alloying reaction between tin and lithium.

As a specific negative electrode active material, a material containing tin can be exemplified. More specifically, examples include Sn alone, tin alloys such as Cu—Sn and Co—Sn, amorphous tin oxide, and tin silicon oxide. The amorphous tin oxide can be exemplified a _SnB 0.4 _P 0.6 _{O 3.1,} as the Suzukei containing oxide can be exemplified SnSiO _3.

  The material containing silicon and the material containing tin are preferably combined with a carbon material to form a negative electrode active material. Due to the composite, the structure of silicon and / or tin is particularly stabilized, and the durability of the negative electrode is improved. The above compounding may be performed by a known method. As the carbon material used for the composite, graphite, hard carbon, soft carbon or the like may be employed. The graphite may be natural graphite or artificial graphite.

As a specific negative electrode active material, lithium titanate having a spinel structure such as Li _{4 + x} Ti _{5 + y} O ₁₂ (−1 ≦ x ≦ 4, −1 ≦ y ≦ 1)), and ramsdellite structure such as Li ₂ Ti ₃ O ₇ The lithium titanate can be illustrated.

  Specific examples of the negative electrode active material include graphite having a major axis / minor axis value of 1 to 5, preferably 1 to 3. Here, the long axis means the length of the longest portion of the graphite particles. The short axis means the length of the longest portion in the direction orthogonal to the long axis. The graphite corresponds to spherical graphite or mesocarbon microbeads. Spherical graphite is a carbon material such as artificial graphite, natural graphite, graphitizable carbon, and non-graphitizable carbon, and has a spherical shape or a substantially spherical shape.

  Spherical graphite is obtained by pulverizing graphite with an impact pulverizer having a relatively small crushing force to form flakes, and then compressing and spheroidizing the flakes. Examples of the impact pulverizer include a hammer mill and a pin mill. It is preferable to perform the above operation with the outer peripheral linear velocity of the hammer or pin of the mill set to about 50 m / second to 200 m / second. It is preferable that graphite is supplied to and discharged from the mill while being accompanied by an air current such as air.

Graphite, BET specific surface area is preferably in the range of 0.5~15m ² / g, more preferably in the range of 2~12m ² / g. If the BET specific surface area is too large, the side reaction between the graphite and the electrolyte solution may be accelerated, and if the BET specific surface area is too small, the reaction resistance of the graphite may be increased.

  The average particle diameter of graphite is preferably in the range of 2 to 30 μm, and more preferably in the range of 5 to 20 μm. In addition, an average particle diameter means D50 at the time of measuring with a general laser diffraction scattering type particle size distribution measuring apparatus.

  In the negative electrode active material layer, the negative electrode active material is preferably contained within a range of 90% by mass to 100% by mass, more preferably within a range of 95% by mass to 99.5% by mass, and 96% by mass. It is more preferable that it is contained in the range of% -99 mass%, and it is especially preferable that it is contained in the range of 97 mass% -98.5 mass%.

(Active material layer forming method)
In order to form the positive electrode active material layer on the surface of the current collector for positive electrode or to form the negative electrode active material layer on the surface of the current collector for negative electrode, roll coating method, die coating method, dip coating method, doctor blade method Each active material may be applied to the surface of each current collector using a conventionally known method such as spray coating or curtain coating. Specifically, a slurry-like composition containing each active material, a solvent, and, if necessary, a binder and a conductive additive is prepared, and this is applied to the surface of each current collector, dried, and then dried. The electrode. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. Moreover, you may add a dispersing agent to the said slurry-like composition. The positive electrode active material layer or the negative electrode active material layer may be formed on one surface of the positive electrode current collector or the negative electrode current collector, or may be formed on both surfaces of each current collector. In order to increase the electrode density, the dried electrode is preferably compressed.

In particular, as a positive electrode active material, a layered compound of Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1.2, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr, At least one element selected from Cu, Zn, Ca, Mg, S, Si, Na, K, Al, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W, La, 1.7 ≦ f In one aspect of the lithium ion secondary battery of the present invention having ≦ 2.1) and having spherical graphite as the negative electrode active material, in order to achieve both high capacity and high input / output characteristics, The lithium ion secondary battery preferably satisfies any of the following rules (A) to (H).

  In order to suitably manufacture the positive electrode or the negative electrode of one aspect of the above-described preferred lithium ion secondary battery of the present invention, the coating amount of the slurry-like composition is set so as to meet the following (A) to (H) regulations: In addition, the compression pressure for each electrode may be set appropriately.

(A) The porosity of the positive electrode active material layer included in the positive electrode is 50% or less. (B) The density of the positive electrode active material layer included in the positive electrode is 2.5 g / cm ³ or more. (C) One existing on the positive electrode current collector. (D) The thickness of one positive electrode active material layer present on the positive electrode current collector is 15 μm or more. (E) The porosity of the negative electrode active material layer included in the negative electrode is at least 3 mg / cm ^2. 50% or less (F) The density of the negative electrode active material layer of the negative electrode is 1.1 g / cm ³ or more (G) The amount of one negative electrode active material layer present on the negative electrode current collector is 2 mg / cm ² or more ( H) The thickness of one negative electrode active material layer present on the negative electrode current collector is 30 μm or more. In order to increase the capacity of both the positive electrode and the negative electrode, the positive electrode active material layer present on the positive electrode current collector is The negative electrode active material layer satisfying any of the above (A) to (D) and present on the negative electrode current collector is the above (E) to Any one of (H) may be satisfied.

  Regarding the positive electrode, the positive electrode active material layer may satisfy any of the above (A) to (D), but preferably satisfies two of the above (A) to (D). It is more preferable to satisfy three of (D), and it is more preferable to satisfy all of the above (A) to (D).

  The porosity defined in (A) is preferably 40% or less, and more preferably 30% or less. As the porosity defined in (A) is smaller, the positive electrode active material layer is more densely filled with components. When the lower limit value of the porosity defined by (A) is exemplified, 10%, 15%, and 20% can be mentioned.

  The porosity defined in (A) can be calculated from the mass ratio and true density of the components contained in the positive electrode active material layer, and the mass and volume of the positive electrode active material layer. The same applies to other void ratios described in this specification.

Density defined in (B) is, 2.6 g / cm ³ or more, and further preferably 2.7 g / cm ³ or more, 2.8 g / cm ³ or more is particularly preferable. Examples of the upper limit value of the density defined by (B) are 3.5 g / cm ³ , 4.0 g / cm ³ , and 4.5 g / cm ³ . For example, the true density of LiNi _5/10 Co _2/10 Mn _3/10 O ₂ , which is one kind of positive electrode active material, is 4.8 g / cm ³ .

The “amount of one positive electrode active material layer present on the positive electrode current collector” in (C) is a rule relating to one positive electrode active material layer existing in contact with the positive electrode current collector. It means the mass of the positive electrode active material layer existing on an area of 1 square centimeter on one side of the electric body (hereinafter, sometimes referred to as “positive electrode weight”). The basis weight of the positive electrode is preferably 4 mg / cm ² or more, and more preferably 5 mg / cm ² or more. If the upper limit of the amount of positive electrode is illustrated daringly, 30 mg / cm < ² >, 40 mg / cm < ² >, 50 mg / cm < ² > can be mentioned.

  The “thickness of one positive electrode active material layer existing on the positive electrode current collector” in (D) is a rule relating to one positive electrode active material layer existing in contact with the positive electrode current collector. It means the thickness of the positive electrode active material layer existing on one side of the electric body (hereinafter, simply referred to as “the thickness of the positive electrode active material layer”). The thickness of the positive electrode active material layer is preferably 20 μm or more, more preferably 30 μm or more, and further preferably 50 μm or more. The upper limit of the thickness of the positive electrode active material layer can be exemplified by 150 μm, 300 μm, and 500 μm.

  Regarding the negative electrode, the negative electrode active material layer may satisfy any of the above (E) to (H), but preferably satisfies two of the above (E) to (H). It is more preferable that three of (H) are satisfied, and it is more preferable that all of the above (E) to (H) are satisfied.

  The porosity defined by (E) is preferably 45% or less. As the porosity defined in (E) is smaller, the negative electrode active material layer is more densely packed with components. When the lower limit value of the porosity defined by (E) is exemplified, 20%, 25%, and 30% can be mentioned.

The density defined by (F) is preferably 1.2 g / cm ³ or more, and more preferably 1.3 g / cm ³ or more. To illustrate dare the upper limit of the density specified in ^{(F), 1.6g / cm 3} , 1.8g / cm 3, can be mentioned 2.0 g / cm ^3. For example, the true density of graphite, which is one type of negative electrode active material, is 2.25 g / cm ³ .

The “amount of one negative electrode active material layer present on the negative electrode current collector” in (G) is a rule relating to one negative electrode active material layer existing in contact with the negative electrode current collector. It means the mass of the negative electrode active material layer present on an area of 1 square centimeter on one side of the electric body (hereinafter, also referred to as “amount of negative electrode weight”). The basis weight of the negative electrode is preferably 3 mg / cm ² or more, and more preferably 4 mg / cm ² or more. Dare, To illustrate the upper limit of the basis weight of the negative ^electrode, can be given ^{15mg / cm 2, 20mg / cm} 2, 30mg / cm 2.

  The “thickness of one negative electrode active material layer present on the negative electrode current collector” in (H) is a rule relating to one negative electrode active material layer existing in contact with the negative electrode current collector. It means the thickness of the negative electrode active material layer existing on one side of the electric body (hereinafter, simply referred to as “the thickness of the negative electrode active material layer”). The thickness of the negative electrode active material layer is preferably 35 μm or more, more preferably 50 μm or more, and further preferably 60 μm or more. If the upper limit of the thickness of a negative electrode active material layer is illustrated dare, 150 micrometers, 300 micrometers, and 500 micrometers can be mentioned.

(Separator)
The separator separates the positive electrode and the negative electrode and allows lithium ions to pass while preventing a short circuit due to contact between the two electrodes. Any known separator may be employed, such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (Aromatic polyamide), polyester, polyacrylonitrile and other synthetic resins, cellulose, amylose and other polysaccharides, fibroin. And porous materials, nonwoven fabrics, woven fabrics, and the like using one or more electrical insulating materials such as natural polymers such as keratin, lignin, and suberin, and ceramics. The separator may have a multilayer structure. For example, the separator made of synthetic resin may have a single layer structure using a single synthetic resin or a laminated structure in which a plurality of synthetic resin layers are stacked.

  The separator preferably has an appropriate gap, and the porosity is preferably 20% to 50%, more preferably 30% to 45%. The thickness of the separator is preferably in the range of 5 μm to 100 μm, more preferably in the range of 10 μm to 50 μm, and still more preferably in the range of 15 μm to 30 μm.

  The shape of the lithium ion secondary battery of the present invention is not particularly limited, and various shapes such as a cylindrical shape, a square shape, a coin shape, and a laminate shape can be adopted.

  The lithium ion secondary battery of this invention should just perform charging / discharging in the voltage range suitable for the kind of active material contained in an electrode.

  The lithium ion secondary battery of the present invention can be suitably charged / discharged even during charge / discharge at a high rate.

  It is preferable that the charging method of the lithium ion secondary battery of the present invention is charged at a rate higher than 30C rate. The charging method of the lithium ion secondary battery of the present invention is more preferably charged at a rate of 40 C or higher, more preferably charged at a rate of 50 C or higher, and particularly preferably charged at a rate of 75 C or higher. If the upper limit of the charging rate is exemplified, a 200C rate, a 300C rate, and a 500C rate can be exemplified.

  It is preferable that the discharge method of the lithium ion secondary battery of this invention discharges at a rate larger than 30C rate. The discharge method of the lithium ion secondary battery of the present invention is more preferably discharged at a rate of 40C or higher, more preferably discharged at a rate of 50C or higher, and particularly preferably discharged at a rate of 75C or higher. If the upper limit of a discharge rate is illustrated dare, a 200C rate, a 300C rate, and a 500C rate can be mentioned.

  The lithium ion secondary battery of the present invention may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy generated by a lithium ion secondary battery for all or a part of its power source. For example, the vehicle may be an electric vehicle or a hybrid vehicle. When a lithium ion secondary battery is mounted on a vehicle, a plurality of lithium ion secondary batteries may be connected in series to form an assembled battery. Examples of devices equipped with lithium ion secondary batteries include various home appliances driven by batteries such as personal computers and portable communication devices, office devices, and industrial devices in addition to vehicles. Furthermore, the lithium ion secondary battery of the present invention includes wind power generation, solar power generation, hydroelectric power generation and other power system power storage devices and power smoothing devices, power supplies for ships and / or auxiliary power supply sources, aircraft, Power supply for spacecraft and / or auxiliary equipment, auxiliary power supply for vehicles that do not use electricity as a power source, power supply for mobile home robots, power supply for system backup, power supply for uninterruptible power supply, You may use for the electrical storage apparatus which stores temporarily the electric power required for charge in the charging station for electric vehicles.

  As mentioned above, although embodiment of the lithium ion secondary battery of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to a following example.

<Electrolyte>
(Production Example 1-1)
(FSO ₂ ) ₂ NLi was dissolved in dimethyl carbonate to produce an electrolytic solution of Production Example 1-1 in which the concentration of (FSO ₂ ) ₂ NLi was 3.0 mol / L. In the electrolytic solution of Production Example 1-1, the chain carbonate is contained at a molar ratio of 3 with respect to the lithium salt.

(Production Example 1-2)
(FSO ₂ ) ₂ NLi was dissolved in dimethyl carbonate to produce an electrolytic solution of Production Example 1-2 in which the concentration of (FSO ₂ ) ₂ NLi was 2.7 mol / L. In the electrolytic solution of Production Example 1-2, the chain carbonate is included at a molar ratio of 3.5 with respect to the lithium salt.

(Production Example 1-3)
(FSO ₂ ) ₂ NLi was dissolved in dimethyl carbonate to produce an electrolytic solution of Production Example 1-3 in which the concentration of (FSO ₂ ) ₂ NLi was 2.3 mol / L. In the electrolytic solution of Production Example 1-3, the chain carbonate is included at a molar ratio of 4 with respect to the lithium salt.

(Production Example 1-4)
(FSO ₂ ) ₂ NLi was dissolved in dimethyl carbonate to produce an electrolytic solution of Production Example 1-4 in which the concentration of (FSO ₂ ) ₂ NLi was 2.0 mol / L. In the electrolytic solution of Production Example 1-4, the chain carbonate is included at a molar ratio of 5 with respect to the lithium salt.

(Production Example 2-1)
Production Example 2 in which (FSO ₂ ) ₂ NLi is dissolved in a mixed solvent in which dimethyl carbonate and diethyl carbonate are mixed at a molar ratio of 9: 1 and the concentration of (FSO ₂ ) ₂ NLi is 2.9 mol / L 1 electrolyte was produced. In the electrolytic solution of Production Example 2-1, chain carbonate is included at a molar ratio of 3 with respect to the lithium salt.

(Production Example 2-2)
Production Example 2 in which (FSO ₂ ) ₂ NLi is dissolved in a mixed solvent in which dimethyl carbonate and diethyl carbonate are mixed at a molar ratio of 7: 1 and the concentration of (FSO ₂ ) ₂ NLi is 2.9 mol / L 2 electrolytes were produced. In the electrolytic solution of Production Example 2-2, the chain carbonate is contained in a molar ratio of 3 with respect to the lithium salt.

(Production Example 2-3)
Production Example 2 in which (FSO ₂ ) ₂ NLi is dissolved in a mixed solvent in which dimethyl carbonate and diethyl carbonate are mixed at a molar ratio of 9: 1 and the concentration of (FSO ₂ ) ₂ NLi is 2.3 mol / L 3 electrolyte was produced. In the electrolytic solution of Production Example 2-3, the chain carbonate is included at a molar ratio of 4 with respect to the lithium salt.

(Production Example 3)
(FSO ₂ ) ₂ NLi was dissolved in ethyl methyl carbonate to produce an electrolytic solution of Production Example 3 in which the concentration of (FSO ₂ ) ₂ NLi was 2.2 mol / L. In the electrolytic solution of Production Example 3, chain carbonate is included at a molar ratio of 3.5 with respect to the lithium salt.

(Production Example 4)
(FSO ₂ ) ₂ NLi was dissolved in diethyl carbonate to produce an electrolytic solution of Production Example 4 in which the concentration of (FSO ₂ ) ₂ NLi was 2.0 mol / L. In the electrolytic solution of Production Example 4, chain carbonate is contained at a molar ratio of 3.5 with respect to the lithium salt.

(Production Example 5-1)
Production Example 5 in which (FSO ₂ ) ₂ NLi is dissolved in a mixed solvent in which dimethyl carbonate and ethyl methyl carbonate are mixed at a molar ratio of 9: 1, and the concentration of (FSO ₂ ) ₂ NLi is 2.9 mol / L -1 electrolyte was produced. In the electrolytic solution of Production Example 5-1, the chain carbonate is contained in a molar ratio of 3 with respect to the lithium salt.

(Production Example 5-2)
Production Example 5 in which (FSO ₂ ) ₂ NLi is dissolved in a mixed solvent in which dimethyl carbonate and ethyl methyl carbonate are mixed at a molar ratio of 9: 1, and the concentration of (FSO ₂ ) ₂ NLi is 2.6 mol / L. -2 electrolyte was produced. In the electrolytic solution of Production Example 5-2, the chain carbonate is included in a molar ratio of 3.6 with respect to the lithium salt.

(Production Example 5-3)
Production Example 5 in which (FSO ₂ ) ₂ NLi is dissolved in a mixed solvent in which dimethyl carbonate and ethyl methyl carbonate are mixed at a molar ratio of 9: 1, and the concentration of (FSO ₂ ) ₂ NLi is 2.4 mol / L. -3 electrolyte was produced. In the electrolytic solution of Production Example 5-3, the chain carbonate is included at a molar ratio of 4 with respect to the lithium salt.

(Comparative Production Example 1-1)
(FSO ₂ ) ₂ NLi was dissolved in dimethyl carbonate to produce an electrolytic solution of Comparative Production Example 1-1 in which the concentration of (FSO ₂ ) ₂ NLi was 4.5 mol / L. In the electrolytic solution of Comparative Production Example 1-1, the chain carbonate is included at a molar ratio of 1.6 with respect to the lithium salt.

(Comparative Production Example 1-2)
(FSO ₂ ) ₂ NLi was dissolved in dimethyl carbonate to produce an electrolytic solution of Comparative Production Example 1-2 in which the concentration of (FSO ₂ ) ₂ NLi was 3.9 mol / L. In the electrolytic solution of Comparative Production Example 1-2, the chain carbonate is contained in a molar ratio of 2 with respect to the lithium salt.

(Comparative Production Example 1-3)
(FSO ₂ ) ₂ NLi was dissolved in dimethyl carbonate to produce an electrolytic solution of Comparative Production Example 1-3 in which the concentration of (FSO ₂ ) ₂ NLi was 1.0 mol / L. In the electrolytic solution of Comparative Production Example 1-3, the chain carbonate is included at a molar ratio of 11 with respect to the lithium salt.

(Comparative Production Example 2)
Comparative production example in which LiPF ₆ as an electrolyte is dissolved in a mixed solvent obtained by mixing ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 3: 3: 4, and the concentration of LiPF ₆ is 1.0 mol / L. 2 electrolytes were produced. In the electrolytic solution of Comparative Production Example 2, the organic solvent is included at a molar ratio of about 10 with respect to the electrolyte.

(Comparative Production Example 3)
LiPF ₆ as an electrolyte is dissolved in a mixed solvent in which diethyl carbonate and ethylene carbonate are mixed at a volume ratio of 7: 3 to produce an electrolytic solution of Comparative Production Example 3 in which the concentration of LiPF ₆ is 1.0 mol / L. did. In the electrolytic solution of Comparative Production Example 3, the organic solvent is included at a molar ratio of about 10 with respect to the electrolyte.

  Table 2 shows a list of manufactured electrolytes.

  The meanings of the abbreviations in Table 2 and the following tables are as follows.

LiFSA: (FSO ₂ ) ₂ NLi
DMC: Dimethyl carbonate EMC: Ethyl methyl carbonate DEC: Diethyl carbonate EC: Ethylene carbonate

(Reference Evaluation Example 1: Ionic conductivity)
The ionic conductivity of the electrolytes of Production Example 1-1, Production Example 1-4, Comparative Production Example 1-1, Comparative Production Example 1-2, Comparative Production Example 1-3, and Comparative Production Example 3 was measured under the following conditions. did. The results are shown in Table 3. Moreover, the result of the electrolyte solution of manufacture example 1-1, manufacture example 1-4, comparative manufacture example 1-1, comparative manufacture example 1-2, and comparative manufacture example 1-3 is shown with a graph in FIG.

Ionic conductivity measurement conditions In an Ar atmosphere, an electrolytic solution was sealed in a glass cell with a platinum constant and a known cell constant, and impedance at 30 ° C. and 1 kHz was measured. The ion conductivity was calculated from the impedance measurement result. As the measuring instrument, Solartron 147055BEC (Solartron) was used.

All of the electrolytic solutions of the present invention exhibited suitable ionic conductivity. Further, from the relationship between the chain carbonate / lithium salt molar ratio and the ionic conductivity in FIG. 2, the maximum value of the ionic conductivity is within the range of the chain carbonate / lithium salt molar ratio of 3 to 6. It is suggested. On the other hand, the conventional electrolyte containing EC as the organic solvent and LiPF ₆ as the metal salt has an ionic conductivity maximized at an organic solvent / metal salt molar ratio of about 10, and the ionic conductivity rapidly increases when the molar ratio is lowered. It is known to decline. That is, the electrolytic solution of the present invention has excellent ionic conductivity even in a high lithium ion concentration region as compared with the conventional electrolytic solution.

(Reference evaluation example 2: density)
The density at 20 ° C. of the electrolyte was measured. The results are shown in Table 4. The blank in the table means no measurement.

(Reference Evaluation Example 3: Viscosity)
The viscosity of the electrolyte solutions of Production Example 1-1, Production Example 1-4, Comparative Production Example 1-1, Comparative Production Example 1-2, and Comparative Production Example 1-3 was measured under the following conditions. The results are shown in Table 5.

Viscosity measurement conditions Using a falling ball viscometer (Lovis 2000 M manufactured by Anton Paar GmbH (Anton Paar)), an electrolytic solution was sealed in a test cell under an Ar atmosphere, and the viscosity was measured at 30 ° C.

  If the viscosity of the electrolytic solution is too low, there is a concern that a large amount of the electrolytic solution leaks when a lithium ion secondary battery including such an electrolytic solution is damaged. On the other hand, if the viscosity of the electrolyte is too high, the ionic conductivity of the electrolyte may decrease, and the productivity of the electrolyte may decrease due to poor permeability of the electrolyte to electrodes, separators, etc. during the manufacture of lithium ion secondary batteries. There is. It can be seen that an electrolyte having a chain carbonate / lithium salt molar ratio of about 3 to 6 does not have a too low or too high viscosity.

(Reference Evaluation Example 4: Low temperature storage test)
The electrolytic solutions of Production Example 1-1, Production Example 1-3, Production Example 1-4, Comparative Production Example 1-2, and Comparative Production Example 1-3 were placed in containers, filled with an inert gas, and sealed. These were stored in a −20 ° C. freezer for 2 days. Each electrolyte was observed after storage. The results are shown in Table 6.

  It can be seen that the larger the value of the chain carbonate / lithium salt molar ratio, that is, the closer to the conventional value, the easier it is to solidify at a low temperature. In addition, although the electrolyte solution of the manufacture example 1-4 solidified by storing at -20 degreeC for 2 days, it is hard to solidify compared with the electrolyte solution of the comparative manufacture example 1-3 which is an electrolyte solution of the conventional density | concentration. It can be said.

(Reference Evaluation Example 5: DSC measurement)
The electrolytic solution of Production Example 1-1 was put in an aluminum pan, and the pan was sealed. Using an empty sealed pan as a control, differential scanning calorimetry was performed under a nitrogen atmosphere with the following temperature program. A Rigaku DSC8230 was used as a differential scanning calorimeter.

Temperature program 5 ° C / min. And kept for 10 minutes → 5 ° C / min. The temperature is lowered and held for 10 minutes → up to 70 ° C. at 3 ° C./min. Temperature rise from −120 ° C. to 70 ° C. at 3 ° C./min. The DSC curve was observed when the temperature was raised at. Differential scanning calorimetry was similarly performed on the electrolytic solution of Production Example 1-4, the electrolytic solution of Comparative Production Example 1-3, and DMC. FIG. 3 shows the overwriting of each DSC curve.

  From the DSC curve of the DMC of FIG. 3 and the electrolyte solution of Comparative Production Example 1-3, a melting peak was observed around 0 to 10 ° C. On the other hand, no melting peak was clearly observed from the DSC curves of Production Example 1-1 and Production Example 1-4. This result suggests that an electrolytic solution having a chain carbonate / lithium salt molar ratio of about 3 to 6 is hardly solidified or crystallized in a low temperature environment. Therefore, it is speculated that the electrolytic solution of the present invention can suppress a decrease in ionic conductivity to some extent in a low temperature environment. In the electrolytic solution of the present invention, when importance is attached to use in a low temperature environment, not only DMC having a melting point of about 4 ° C. but also EMC having a melting point of about −55 ° C. or a melting point of −43 ° C. as a chain carbonate. It is preferable to use a nearby DEC in combination.

(Reference Evaluation Example 6: DSC measurement <2>)
The electrolytic solution of Production Example 2-3 was put in an aluminum pan, and the pan was sealed. Using an empty sealed pan as a control, differential scanning calorimetry was performed under a nitrogen atmosphere with the following temperature program. As the differential scanning calorimeter, DSC Q2000 (manufactured by TA Instruments) was used.
Temperature program 5 ° C / min. From room temperature to -75 ° C. The temperature is lowered and held for 10 minutes → 5 ° C / min. Temperature rise at

  From -75 ° C to 70 ° C, 5 ° C / min. The DSC curve was observed when the temperature was raised at. The differential scanning calorimetry was similarly performed on the electrolytic solution of Production Example 5-3 and the electrolytic solution of Comparative Production Example 2. FIG. 4 shows the overwriting of each DSC curve.

  In FIG. 4, from the DSC curve of the electrolytic solution of Comparative Production Example 2, an endothermic peak presumed to be derived from the melting point was observed around −50 to −20 ° C. On the other hand, no endothermic peak was observed from the DSC curves of Production Example 2-3 and Production Example 5-3. It was confirmed that the electrolytic solution of the present invention combined with a chain carbonate is hardly solidified or crystallized in a low temperature environment. Therefore, the lithium ion secondary battery using the electrolytic solution of the present invention is presumed to operate suitably even under extremely low temperature conditions.

Example 1
A lithium ion secondary battery of Example 1 using the electrolytic solution of Production Example 5-2 was produced as follows.

(Preparation of positive electrode)
90 parts by mass of a lithium-containing metal oxide represented by LiNi _0.5 Co _0.35 Mn _0.15 O ₂ which is a positive electrode active material, 5 parts by mass of acetylene black which is a conductive additive, 3 parts by mass of graphite, 2 parts by mass of polyvinylidene fluoride (hereinafter referred to as PVDF) as an adhesive was mixed. This mixture was dispersed in an appropriate amount of N-methyl-2-pyrrolidone (hereinafter referred to as NMP) to prepare a slurry. An aluminum foil corresponding to JIS A1000 series having a thickness of 15 μm was prepared as a positive electrode current collector. The slurry was applied on one surface of the aluminum foil using a doctor blade so that the slurry became a film. The aluminum foil coated with the slurry was dried at 80 ° C. for 20 minutes to remove NMP by volatilization to obtain an aluminum foil on which the positive electrode active material layer was formed. The aluminum foil on which this positive electrode active material layer was formed was used as the positive electrode. The density of the positive electrode active material layer was 2.7 g / cm ³ . The porosity of the positive electrode active material layer was 38%. The basis weight of the positive electrode was 5.6 mg / cm ² , and the thickness of the positive electrode active material layer was 20 μm.

  The porosity of the positive electrode active material layer is a value obtained by subtracting the theoretical volume of each component calculated from the blending amount and true density of each component contained in the positive electrode active material layer from the apparent volume of the positive electrode active material layer. Was divided by the apparent volume of the positive electrode active material layer.

  The apparent volume of the positive electrode active material layer was calculated from the following formula.

  Apparent volume of positive electrode active material layer = actual thickness of positive electrode active material layer × area of surface on which positive electrode active material layer is formed

The sum of theoretical volumes of each component of the positive electrode active material layer was calculated from the following formula.
True density of the positive electrode active mass of the sum _{= LiNi 0.5 Co 0.35 Mn 0.15 O} 2 of the volume of the theoretical for each component of the material layer _{÷ LiNi 0.5 Co 0.35 Mn 0.15 O} 2 + Mass of acetylene black ÷ true density of acetylene black + mass of graphite ÷ true density of graphite + mass of PVDF ÷ true density of PVDF

The true density of LiNi _0.5 Co _0.35 Mn _0.15 O ₂ is 4.7 g / cm ³ , the true density of acetylene black is 1.3 g / cm ³ , and the true density of graphite is 2.2 g / cm ^3. The true density of PVDF was calculated as 1.7 g / cm ³ .

(Preparation of negative electrode)
98 parts by mass of spherical graphite as a negative electrode active material, 1 part by mass of styrene butadiene rubber as a binder, and 1 part by mass of carboxymethyl cellulose were mixed. This mixture was dispersed in an appropriate amount of ion-exchanged water to prepare a slurry. A copper foil having a thickness of 10 μm was prepared as a negative electrode current collector. The slurry was applied in a film form on one surface of the copper foil using a doctor blade. The copper foil coated with the slurry was dried to remove water, and then the copper foil was pressed to obtain a bonded product. The obtained joined product was heat-dried at 120 ° C. for 6 hours with a vacuum dryer to obtain a copper foil having a negative electrode active material layer formed thereon. The density of the negative electrode active material layer was 1.1 g / cm ³ . The porosity of the negative electrode active material layer was 49%. The basis weight of the negative electrode was 4.2 mg / cm ² , and the thickness of the negative electrode active material layer was 37 μm.

The porosity of the negative electrode active material layer was calculated in the same manner as the method for calculating the porosity of the positive electrode active material layer. The true density of natural graphite was 2.2 g / cm ³ , the true density of styrene butadiene rubber was 1.6 g / cm ³ , and the true density of carboxymethylcellulose was 1.0 g / cm ³ .

(Separator)
A polyolefin porous membrane with a ceramic coat having a thickness of 20 μm and a porosity of 45% was prepared as a separator.

(Laminated lithium ion secondary battery)
A separator was sandwiched between the positive electrode and the negative electrode to form an electrode plate group. The electrode plate group was covered with a set of two laminated films, and the three sides were sealed. Then, the electrolytic solution of Production Example 5-2 was injected into the bag-like laminated film. By sealing the remaining one side, a lithium ion secondary battery in which the four sides were hermetically sealed and the electrode plate group and the electrolyte solution were sealed was obtained. This battery was used as the lithium ion secondary battery of Example 1. The battery capacity of the lithium ion secondary battery of Example 1 was 5 mAh.

  In the lithium ion secondary battery of Example 1, the positive electrode terminal was ultrasonically welded to the positive electrode current collector in the positive electrode, and the negative electrode terminal was ultrasonically welded to the negative electrode current collector in the negative electrode. Part of the positive electrode terminal and the negative electrode terminal extended to the outside of the lithium ion secondary battery.

  In FIG. 5, the schematic diagram explaining the positive electrode of the lithium ion secondary battery of Example 1 is shown. In the positive electrode 51, the positive electrode active material layer 2 is disposed on the positive electrode current collector 1, and the positive electrode terminal 3 is in contact with the positive electrode current collector 1 at the contact surface 41. At this time, the contact surface 41 was ultrasonically welded.

The positive electrode terminal was made of aluminum and had a strip shape with a width of 5 mm, a length of 60 mm, and a thickness of 0.1 mm. In the lithium ion secondary battery of Example 1, the area of the positive electrode active material layer arrangement part was 750 mm ² and the area of the positive electrode active material layer non-arrangement part was 300 mm ² .

In the lithium ion secondary battery of Example 1, the positive electrode contact area was 12 mm ² . In the lithium ion secondary battery of Example 1, the positive electrode contact area with respect to the battery capacity was 2400 mm ² / Ah, and the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion was 4%.

The negative electrode terminal was made of nickel and had a strip shape with a width of 5 mm, a length of 60 mm, and a thickness of 0.1 mm. In the lithium ion secondary battery of Example 1, the area of the negative electrode active material layer arrangement part was 864 mm ² and the area of the negative electrode active material layer non-arrangement part was 320 mm ² .

In the lithium ion secondary battery of Example 1, the negative electrode contact area was 12 mm ² . In the lithium ion secondary battery of Example 1, the negative electrode contact area with respect to the battery capacity was 2400 mm ² / Ah, and the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion was 3.75%.

(Example 2)
The lithium ion secondary of Example 2 was changed in the same manner as the lithium ion secondary battery of Example 1, except that the welding direction of the positive electrode terminal and the negative electrode terminal was changed and the positive electrode contact area and the negative electrode contact area were as follows. A battery was manufactured.

  In FIG. 6, the schematic diagram explaining the positive electrode of the lithium ion secondary battery of Example 2 is shown. In the positive electrode 52, the positive electrode active material layer 2 is disposed on the positive electrode current collector 1, and the positive electrode terminal 3 is in contact with the positive electrode current collector 1 on the contact surface 42. At this time, the contact surface 42 was ultrasonically welded.

In the lithium ion secondary battery of Example 2, the positive electrode contact area was 72 mm ² . In the lithium ion secondary battery of Example 2, the positive electrode contact area with respect to the battery capacity was 14400 mm ² / Ah, and the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion was 24%.

The negative electrode contact area of the lithium ion secondary battery of Example 2 was 72 mm ² . In the lithium ion secondary battery of Example 2, the negative electrode contact area with respect to the battery capacity was 14400 mm ² / Ah, and the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion was 22.5%.

(Comparative Example 1)
A lithium ion secondary battery of Comparative Example 1 was produced in the same manner as the lithium ion secondary battery of Example 1 except that the electrolytic solution of Comparative Production Example 2 was used as the electrolytic solution. In the lithium ion secondary battery of Comparative Example 1, the positive electrode contact area with respect to the battery capacity was 2400 mm ² / Ah, and the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion was 4%.

In the lithium ion secondary battery of Comparative Example 1, the negative electrode contact area with respect to the battery capacity was 2400 mm ² / Ah, and the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion was 3.75%. .

(Comparative Example 2)
A lithium ion secondary battery of Comparative Example 2 was produced in the same manner as the lithium ion secondary battery of Example 2 except that the electrolyte solution of Comparative Production Example 2 was used as the electrolytic solution. In the lithium ion secondary battery of Comparative Example 2, the positive electrode contact area with respect to the battery capacity was 14400 mm ² / Ah, and the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion was 24%.

In the lithium ion secondary battery of Comparative Example 2, the negative electrode contact area with respect to the battery capacity was 14400 mm ² / Ah, and the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion was 22.5%. It was.

(Example 3)
(Wind-type prismatic lithium-ion secondary battery)
(Preparation of positive electrode)
90 parts by mass of a lithium-containing metal oxide represented by LiNi _0.5 Co _0.35 Mn _0.15 O ₂ which is a positive electrode active material, 5 parts by mass of acetylene black which is a conductive additive, 3 parts by mass of graphite, 2 parts by mass of PVDF which is an adhesive was mixed. This mixture was dispersed in an appropriate amount of NMP to prepare a positive electrode active material layer slurry. An aluminum foil corresponding to JIS A1000 series having a thickness of 15 μm was prepared as a positive electrode current collector.

The slurry for positive electrode active material layer was apply | coated to both surfaces of the aluminum foil. At this time, uncoated portions of the positive electrode active material layer slurry were provided on both sides in the width direction of the current collector. This uncoated portion finally becomes the positive electrode active material layer non-arranged portion. This was dried to obtain a sheet-like positive electrode of Example 3. In the positive electrode of Example 3, the density of the positive electrode active material layer was 2.7 g / cm ³ , the porosity of the positive electrode active material layer was 38%, and the basis weight of the positive electrode was 5.6 mg / cm ^{2 on} one side, The thickness was 11.2 mg / cm ^{2 on} both sides, and the thickness of the positive electrode active material layer was 20 μm on one side.

(Preparation of negative electrode)
98 parts by mass of spherical graphite as a negative electrode active material, 1 part by mass of styrene butadiene rubber as a binder, and 1 part by mass of carboxymethyl cellulose were mixed. This mixture was dispersed in an appropriate amount of ion-exchanged water to prepare a negative electrode active material layer slurry. A copper foil having a thickness of 10 μm was prepared as a negative electrode current collector.

The negative electrode active material layer slurry was applied to both sides of the copper foil. At this time, uncoated portions of the negative electrode active material layer slurry were provided on both sides in the width direction of the copper foil. This uncoated portion finally becomes the negative electrode active material layer non-arranged portion. This was dried to obtain the negative electrode of Example 3. In the negative electrode of Example 3, the density of the negative electrode active material layer was 1.1 g / cm ³ , the porosity of the negative electrode active material layer was 49%, and the basis weight of the negative electrode was 4.2 mg / cm ^{2 on} one side. a 8.4 mg / cm ² on both sides, the thickness of the negative electrode active material layer on one surface was 37 [mu] m.

  A separator was sandwiched between the positive electrode of Example 3 and the negative electrode of Example 3, and wound 30 times to produce an electrode plate group. A positive electrode terminal was welded to the positive electrode active material layer non-arranged portion of the positive electrode group using an ultrasonic welding machine. This positive electrode terminal had a strip shape with a width of 7 mm, a thickness of 1.5 mm, and a length of 35 mm made of aluminum, and one end was previously welded to an aluminum lid and integrated with the lid. As will be described later, the aluminum lid serves as a lid for a can, which is a container for holding the electrode plate group. Similarly, a negative electrode terminal was welded to the negative electrode active material layer non-arranged portion of this negative electrode group using an ultrasonic welding machine. The negative electrode terminal had a strip shape with a copper width of 7 mm, a thickness of 1.5 mm, and a length of 35 mm, and one end was previously welded to an aluminum lid and integrated with the lid. The electrode plate group to which each terminal was welded was placed in a square aluminum can, and the fitting portion between the lid and the can was welded using a laser welding machine. The electrolytic solution of Production Example 5-2 was injected into the can, and a lithium ion secondary battery of Example 3 was produced. The battery capacity of the lithium ion secondary battery of Example 3 was 4.3 Ah.

In the lithium ion secondary battery of Example 3, the area of the positive electrode active material layer non-arranged part was 56322 mm ² in the whole positive electrode. In the lithium ion secondary battery of Example 3, the positive electrode contact area with respect to the battery capacity was 388.5 mm ² / Ah, and the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion was 2.97%. .

In the lithium ion secondary battery of Example 3, the area of the negative electrode active material layer non-arranged part was 56787.5 mm ² in the whole negative electrode. In the lithium ion secondary battery of Example 3, the negative electrode contact area with respect to the battery capacity was 401.4 mm ² / Ah, and the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion was 3.04%. .

Example 4
An example was obtained in the same manner as the lithium ion secondary battery of Example 3, except that a separator was sandwiched between the positive electrode of Example 3 and the negative electrode of Example 3, and the electrode group was produced by winding 27 times. No. 4 lithium ion secondary battery was produced. The battery capacity of the lithium ion secondary battery of Example 4 was 3.9 Ah.

In the lithium ion secondary battery of Example 4, the area of the positive electrode active material layer non-arranged part was 50418.0 mm ² for the entire positive electrode. In the lithium ion secondary battery of Example 4, the positive electrode contact area with respect to the battery capacity was 385.5 mm ² / Ah, and the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion was 2.98%. .

In the lithium ion secondary battery of Example 4, the area of the negative electrode active material layer non-arranged part was 51047.5 mm ² for the entire negative electrode. In the lithium ion secondary battery of Example 4, the negative electrode contact area with respect to the battery capacity was 399.8 mm ² / Ah, and the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion was 3.05% .

(Example 5)
(Stacked prismatic lithium-ion secondary battery)
(Preparation of positive electrode)
94 parts by mass of a lithium-containing metal oxide represented by LiNi _0.5 Co _0.2 Mn _0.3 O _{2 as} a positive electrode active material, 3 parts by mass of acetylene black as a conductive additive, and PVDF3 as a binder Mass parts were mixed. This mixture was dispersed in an appropriate amount of NMP to prepare a positive electrode active material layer slurry. An aluminum foil corresponding to JIS A1000 series having a thickness of 15 μm was prepared as a positive electrode current collector.

The slurry for positive electrode active material layer was apply | coated to both surfaces of the aluminum foil. This can be dried to obtain the positive electrode of Example 5. In the positive electrode of Example 5, the density of the positive electrode active material layer is 3.0 g / cm ³ , the porosity of the positive electrode active material layer is 26%, and the basis weight of the positive electrode is 18.2 mg / cm ^{2 on} one side. The thickness of both surfaces was 36.4 mg / cm ² , and the thickness of the positive electrode active material layer was 60 μm on one side.

(Preparation of negative electrode)
98 parts by mass of spherical graphite as a negative electrode active material, 1 part by mass of styrene butadiene rubber as a binder, and 1 part by mass of carboxymethyl cellulose were mixed. This mixture was dispersed in an appropriate amount of ion-exchanged water to prepare a negative electrode active material layer slurry. A copper foil having a thickness of 10 μm was prepared as a negative electrode current collector.

The negative electrode active material layer slurry was applied to both sides of the copper foil. This can be dried to obtain the negative electrode of Example 5. In the negative electrode of Example 5, the density of the negative electrode active material layer was 1.3 g / cm ³ , the porosity of the negative electrode active material layer was 30%, and the basis weight of the negative electrode was 9.7 mg / cm ^{2 on} one side, The thickness was 19.4 mg / cm ^{2 on} both sides, and the thickness of the negative electrode active material layer was 73 μm on one side.

  An electrode plate group was produced by using 66 positive electrodes of Example 5 and 67 negative electrodes of Example 5 and laminating them with a separator interposed therebetween. A positive electrode terminal was welded to the positive electrode active material layer non-arranged portion of the positive electrode group using an ultrasonic welding machine. The positive electrode terminal had a strip shape made of aluminum having a width of 20 mm, a thickness of 1.5 mm, and a length of 44 mm, and one end was previously welded to an aluminum lid and integrated with the lid. As will be described later, the aluminum lid serves as a lid for a can, which is a container for holding the electrode plate group. Similarly, a negative electrode terminal was welded to the negative electrode active material layer non-arranged portion of this negative electrode group using an ultrasonic welding machine. The negative electrode terminal had a strip shape with a width of 20 mm, a thickness of 1.5 mm, and a length of 44 mm made of copper, and one end was previously welded to an aluminum lid and integrated with the lid. The electrode plate group to which each terminal was welded was put into a square aluminum can, and the fitting portion between the lid and the can was welded using a laser welding machine.

  The lithium ion secondary battery of Example 5 can be manufactured by injecting the electrolytic solution of Production Example 5-2 into the can. The battery capacity of the lithium ion secondary battery of Example 5 is assumed to be 45 Ah.

In the positive electrode of Example 5, the area of the positive electrode active material layer non-arranged part was 891 mm ² for the entire positive electrode. In the positive electrode of Example 5, the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion was 51.85%. In the positive electrode of Example 5, the positive electrode contact area with respect to the battery capacity is assumed to be 10.3 mm ² / Ah.

In the negative electrode of Example 5, the area of the negative electrode active material layer non-arranged part was 767.8 mm ^{2 as a} whole. In the negative electrode of Example 5, the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion was 34.9%. In the negative electrode of Example 5, the negative electrode contact area with respect to the battery capacity is assumed to be 6.0 mm ² / Ah.

(Example 6)
A positive electrode of Example 6 was produced in the same manner as the positive electrode of Example 5 except that the positive electrode active material was LiNi _0.5 Co _0.35 Mn _0.15 O ₂ . In the positive electrode of Example 6, the density of the positive electrode active material layer is 3.0 g / cm ³ , the porosity of the positive electrode active material layer is 26%, and the basis weight of the positive electrode is 18.2 mg / cm ^{2 on} one side. The thickness of both surfaces was 36.4 mg / cm ² , and the thickness of the positive electrode active material layer was 60 μm on one side.

The negative electrode of the basis weight of the single-sided 10.5 mg / cm ^2, and 21.0 mg / cm ² on both sides, except that the thickness of the negative electrode active material layer was on one side 82 .mu.m, the negative electrode of Example 6 in the same manner as in Example 5 Produced. In the negative electrode of Example 6, the density of the negative electrode active material layer was 1.3 g / cm ³ , and the porosity of the negative electrode active material layer was 30%.

  Except that a positive electrode group was prepared by stacking electrodes using 68 positive electrodes of Example 6 and 69 negative electrodes of Example 6, a lithium ion secondary battery of Example 5 was used. A lithium ion secondary battery can be obtained. The battery capacity of the lithium ion secondary battery of Example 6 is assumed to be 45 Ah.

In the positive electrode of Example 6, the area of the positive electrode active material layer non-arranged part was 891 mm ² for the entire positive electrode. In the positive electrode of Example 6, the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion was 53.42%. In the positive electrode of Example 6, the positive electrode contact area with respect to the battery capacity is assumed to be 10.6 mm ² / Ah.

In the negative electrode of Example 6, the total area of the negative electrode active material layer non-arranged part was 767.8 mm ² . In the negative electrode of Example 6, the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion was 35.95%. In the negative electrode of Example 6, the negative electrode contact area with respect to the battery capacity is assumed to be 6.1 mm ² / Ah.

  In Table 7, the specification of the lithium ion secondary battery of Examples 1-4 and Comparative Examples 1-2 and the specification assumed of the lithium ion secondary battery of Examples 5-6 are shown collectively.

<Rate characteristic evaluation of lithium ion secondary battery>
(Evaluation example 1: discharge duration measurement)
The discharge duration of the lithium ion secondary batteries of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 was measured. Each lithium ion secondary battery was charged to a voltage of 4.1 V at a 1C rate. Here, 1C means a current value required for fully charging or discharging a battery in one hour at a constant current. For each lithium ion secondary battery with a voltage of 4.1V, up to a voltage of 3V, which is a cut-off voltage, at 25 ° C, 1C rate, 5C rate, 10C rate, 15C rate, 30C rate, 50C rate, 75C rate, 150C rate Each was discharged.

  The discharge time from 4.1 V to 3 V at each rate was measured and used as the discharge duration.

  The discharge duration of the lithium ion secondary battery of Comparative Example 1 was set to 1 at each rate, and the ratio of the discharge durations of the lithium ion secondary batteries of Example 1, Example 2 and Comparative Example 2 at each rate was calculated. The results are shown in FIG. FIG. 7 is a graph comparing the discharge duration ratios of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 for each rate. In FIG. 7, the bar graph of each rate shows the results of Comparative Example 1, Comparative Example 2, Example 1, and Example 2 from the left.

  As shown in FIG. 7 and Table 8, the discharge durations of the lithium ion secondary batteries of Example 1 and Example 2 are longer than the discharge durations of the lithium ion secondary batteries of Comparative Example 1 and Comparative Example 2. It was. In particular, at high rates exceeding 30 C, the discharge durations of the lithium ion secondary batteries of Example 1 and Example 2 were significantly longer than the discharge durations of the lithium ion secondary batteries of Comparative Example 1 and Comparative Example 2. .

  In the lithium ion secondary battery of Comparative Example 2, the positive electrode contact area and the negative electrode contact area were increased as compared with the lithium ion secondary battery of Comparative Example 1, but the discharge duration was hardly changed. In contrast, when the discharge durations of the lithium ion secondary batteries of Example 1 and Example 2 are compared, the lithium ion secondary battery of Example 2 in which the positive electrode contact area and the negative electrode contact area are increased is more discharged. Longer duration. Therefore, in the lithium ion secondary battery using the electrolytic solution of the present invention, increasing the positive electrode contact area and the negative electrode contact area with respect to the battery capacity has an effect of extending the discharge duration, and the effect is particularly high. It was found that this was remarkable during charging and discharging.

  FIG. 9 shows a graph showing the relationship between the 50 C rate, 75 C rate, and 150 C rate voltages of the lithium ion secondary battery of Comparative Example 1 and the discharge duration (seconds), and FIG. 10 shows the lithium ion secondary battery of Example 1. The graph which shows the relationship between the voltage of 50C rate of a secondary battery, 75C rate, and 150C rate, and discharge duration (second) is shown.

  Comparing FIG. 9 and FIG. 10, in the lithium ion secondary battery of Comparative Example 1 and the lithium ion secondary battery of Example 1, the voltage near 0 second was obtained at any of the 50C rate, 75C rate, and 150C rate. The fall of was almost the same. However, at any of the 50C rate, the 75C rate, and the 150C rate, the slope of the voltage drop after the vicinity of 0 second is higher than that of the lithium ion secondary battery of Comparative Example 1 in the lithium ion secondary battery of Example 1. The battery was more gradual. Therefore, it can be considered that the discharge duration of the example became longer because the slope of the voltage drop after 0 seconds was gentle.

  FIG. 11 shows a graph showing the relationship between the 150 C rate voltage and discharge duration of Example 1, and FIG. 12 shows a graph showing the relationship between the 150 C rate voltage and discharge duration of Example 2.

  Comparing FIG. 11 and FIG. 12, in the lithium ion secondary battery of Example 1, the voltage near 0 seconds is smaller than 3600 mV, but in the lithium ion secondary battery of Example 2, the voltage near 0 seconds is 3600 mV. It was bigger. From this, it can be said that when the contact area between the terminal and the current collector increases, the voltage drop in the vicinity of 0 seconds decreases. Moreover, when the contact area of a terminal and an electrical power collector becomes large, it is guessed that the electronic resistance between a terminal and an electrical power collector becomes small.

  FIG. 13 shows a graph comparing the contact area with respect to the battery capacity and the ratio of the discharge duration at the 75C rate.

  Here, the “contact area with respect to the battery capacity” refers to a positive electrode contact area with respect to the battery capacity or a negative electrode contact area with respect to the battery capacity. In the lithium ion secondary batteries of Example 1, Example 2, Comparative Example 1 and Comparative Example 2, the positive electrode contact area with respect to the battery capacity and the negative electrode contact area with respect to the battery capacity were the same. Therefore, the “contact area with respect to the battery capacity” in FIG. 13 may be a positive electrode contact area with respect to the battery capacity or a negative electrode contact area with respect to the battery capacity.

  As shown in FIG. 13, in the lithium ion secondary battery of Comparative Example 1 and the lithium ion secondary battery of Comparative Example 2 using a conventional electrolyte, the discharge duration is increased even when the contact area with respect to the battery capacity increases. In contrast, in the lithium ion secondary battery of Example 1 and the lithium ion secondary battery of Example 2 using the electrolytic solution of the present invention, when the contact area with respect to the battery capacity increases, the discharge sustains. It turns out that time is long. From this, for the first time by using the electrolytic solution of the present invention and lowering the ionic resistance, especially the diffusion resistance, in the lithium ion secondary battery, when the contact area per battery capacity is increased and the electronic resistance is reduced, the lithium ion It can be said that the discharge duration of the secondary battery can be increased.

  FIG. 14 shows a graph comparing the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion and the ratio of the discharge duration at the 75C rate. As can be seen in FIG. 14, in the lithium ion secondary battery of Comparative Example 1 and the lithium ion secondary battery of Comparative Example 2 using a conventional electrolyte, the positive electrode contact area relative to the area of the positive electrode active material layer non-arranged portion In the lithium ion secondary battery of Example 1 and the lithium ion secondary battery of Example 2 using the electrolytic solution of the present invention, while the discharge duration hardly changes even when the ratio increases, the positive electrode active If the ratio of the positive electrode contact area to the area of the material layer non-arranged portion was increased, the discharge duration of the lithium ion secondary battery could be increased. In other words, in the lithium ion secondary battery using the electrolytic solution of the present invention, in order to increase the discharge duration, the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion may be increased. It can be said.

  Further, in FIG. 14, the ratio of the positive electrode contact area to the area of the positive electrode active material layer non-arranged portion and the ratio of the discharge duration were compared. The same was true when compared with the ratio of the positive electrode contact area to the ratio of the charge duration. Further, the same can be said by comparing the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion and the ratio of the discharge duration, and the ratio of the negative electrode contact area to the area of the negative electrode active material layer non-arranged portion. And the same can be said when compared to the ratio of charge duration.

(Evaluation Example 2: Charging duration measurement)
The charge duration measurement of the lithium ion secondary batteries of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 was performed. Each lithium ion secondary battery was discharged at a 1C rate to a voltage of 3V. For each lithium ion secondary battery with a voltage of 3V, up to a voltage of 4.1V, which is a cutoff voltage, at 25 ° C, 1C rate, 5C rate, 10C rate, 15C rate, 30C rate, 50C rate, 75C rate, 150C rate Each was charged with.

The charging time from 3 V to 4.1 V at each rate was measured and used as the charging duration.
The charging duration of the lithium ion secondary battery of Comparative Example 1 was set to 1 at each rate, and the ratio of the charging duration of the lithium ion secondary batteries of Comparative Example 2, Example 1, and Example 2 for each rate was calculated. The results are shown in FIG. FIG. 8 is a graph comparing the charge duration ratios of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 for each rate.

  As shown in FIG. 8 and Table 9, the charging duration of the lithium ion secondary batteries of Example 1 and Example 2 is longer than the charging duration of the lithium ion secondary batteries of Comparative Example 1 and Comparative Example 2. It was. In particular, at a high rate exceeding 30 C rate, the charging duration of the lithium ion secondary batteries of Example 1 and Example 2 is significantly longer than the charging duration of the lithium ion secondary batteries of Comparative Example 1 and Comparative Example 2. It was. Moreover, in the lithium ion secondary battery of Comparative Example 2, the positive electrode contact area and the negative electrode contact area were increased as compared with the lithium ion secondary battery of Comparative Example 1, but the charge duration was hardly changed. On the other hand, when the charge durations of the lithium ion secondary batteries of Example 1 and Example 2 are compared, the lithium ion secondary battery of Example 2 in which the positive electrode contact area and the negative electrode contact area are increased is more charged. Longer duration. From this, in the lithium ion secondary battery using the electrolytic solution of the present invention, increasing the positive electrode contact area and the negative electrode contact area with respect to the battery capacity has the effect of extending the charge duration, and the effect is particularly high. It was found that this was remarkable during charging and discharging.

  From the results of Evaluation Example 1 and Evaluation Example 2, the following can be inferred. In the electrolytic solution of the present invention, the lithium ion concentration is higher than that of the conventional electrolytic solution. Therefore, in the lithium ion secondary batteries of Examples 1 and 2 using the electrolytic solution of the present invention, Compared to the lithium ion secondary batteries of Comparative Example 1 and Comparative Example 2 using the electrolyte solution, the ionic resistance during charging / discharging, in particular, the diffusion resistance, is suppressed, and the discharge duration and charge duration of the lithium ion secondary battery are suppressed. It is assumed that the time has become longer.

  Moreover, in the lithium ion secondary battery using the conventional electrolyte solution, even if the contact area between the terminal and the current collector is increased, the discharge duration and the charge duration cannot be increased. It can be said that the discharge duration and the charge duration can be lengthened only when the contact area between the terminal and the current collector is increased by suppressing the ionic resistance and the diffusion resistance by using the electrolytic solution of the present invention.

1: current collector for positive electrode, 2: positive electrode active material layer, 3: terminal for positive electrode, 4: contact surface, 5: positive electrode, 6: current collector for negative electrode, 7: negative electrode active material layer, 8: terminal for negative electrode , 9: contact surface, 10: negative electrode, 11: separator, 12: electrode plate group, 13: container.

Claims (11)

A positive electrode having a positive electrode current collector and a positive electrode terminal in contact with the positive electrode current collector;
A negative electrode having a negative electrode current collector and a negative electrode terminal in contact with the negative electrode current collector;
An electrolyte,
A lithium ion secondary battery comprising:
The electrolytic solution includes an electrolyte containing a lithium salt represented by the following general formula (1) and an organic solvent containing a chain carbonate represented by the following general formula (2), and with respect to the lithium salt The chain carbonate is included in a molar ratio of 3 to 6,
A contact area between the positive electrode current collector and the positive electrode terminal with respect to a battery capacity or a contact area between the negative electrode current collector and the negative electrode terminal with respect to a battery capacity is greater than 3 mm ² / Ah, Lithium ion secondary battery.
(R ¹ X ¹ ) (R ² SO ₂ ) NLi General formula (1)
(R ¹ is hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted with, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, or an alkoxy group which may be substituted with a substituent , An unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, an unsaturated thioalkoxy group that may be substituted with a substituent, CN, SCN, or OCN Is done.
R ² represents hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, an alkoxy group which may be substituted with a substituent, Selected from an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, CN, SCN, OCN The
R ¹ and R ² may be bonded to each other to form a ring.
X ¹ is selected from SO ₂ , C = O, C = S, R ^a P = O, R ^b P = S, S = O, Si = O.
R ^a and R ^b are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a group that may be substituted with a substituent. A saturated alkyl group, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, a heterocyclic group that may be substituted with a substituent, and a substituent An alkoxy group which may be substituted, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, OH , SH, CN, SCN, and OCN.
R ^a and R ^b may combine with R ¹ or R ² to form a ring. )
R ²⁰ OCOOR ²¹ general formula (2)
(R ²⁰ and R ²¹ each independently represent C _n H _a F _b Cl _c Br _d I _e which is a chain alkyl, or C _m H _f F _g Cl _h Br _i I containing a cyclic alkyl in the chemical structure. selected from _j , n is an integer of 1 or more, m is an integer of 3 or more, a, b, c, d, e, f, g, h, i, j are each independently an integer of 0 or more 2n + 1 = a + b + c + d + e, 2m = f + g + h + i + j is satisfied.) Contact with the positive electrode current collector, the positive electrode active material layer disposed on the positive electrode active material layer arrangement part on the surface of the positive electrode current collector, and the positive electrode active material layer non-arrangement part on the surface of the positive electrode current collector A positive electrode terminal, and a positive electrode having
Contact with the negative electrode current collector, the negative electrode active material layer disposed in the negative electrode active material layer arrangement part on the surface of the negative electrode current collector, and the negative electrode active material layer non-arrangement part on the surface of the negative electrode current collector A negative electrode having a negative electrode terminal,
An electrolyte,
A lithium ion secondary battery comprising:
The electrolytic solution includes an electrolyte containing a lithium salt represented by the following general formula (1) and an organic solvent containing a chain carbonate represented by the following general formula (2), and with respect to the lithium salt The chain carbonate is included in a molar ratio of 3 to 6,
The ratio of the contact area between the positive electrode current collector and the positive electrode terminal to the area of the positive electrode active material layer non-arranged portion, or the negative electrode current collector and the area of the negative electrode active material layer non-arranged portion and the area A lithium ion secondary battery, wherein a ratio of a contact area with the negative electrode terminal is 2% or more and 100% or less.
(R ¹ X ¹ ) (R ² SO ₂ ) NLi General formula (1)
(R ¹ is hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted with, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, or an alkoxy group which may be substituted with a substituent , An unsaturated alkoxy group that may be substituted with a substituent, a thioalkoxy group that may be substituted with a substituent, an unsaturated thioalkoxy group that may be substituted with a substituent, CN, SCN, or OCN Is done.
R ² represents hydrogen, halogen, an alkyl group which may be substituted with a substituent, a cycloalkyl group which may be substituted with a substituent, an unsaturated alkyl group which may be substituted with a substituent, or a substituent. An unsaturated cycloalkyl group which may be substituted, an aromatic group which may be substituted with a substituent, a heterocyclic group which may be substituted with a substituent, an alkoxy group which may be substituted with a substituent, Selected from an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, CN, SCN, OCN The
R ¹ and R ² may be bonded to each other to form a ring.
X ¹ is selected from SO ₂ , C = O, C = S, R ^a P = O, R ^b P = S, S = O, Si = O.
R ^a and R ^b are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a group that may be substituted with a substituent. A saturated alkyl group, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, a heterocyclic group that may be substituted with a substituent, and a substituent An alkoxy group which may be substituted, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, OH , SH, CN, SCN, and OCN.
R ^a and R ^b may combine with R ¹ or R ² to form a ring. )
R ²⁰ OCOOR ²¹ general formula (2)
(R ²⁰ and R ²¹ each independently represent C _n H _a F _b Cl _c Br _d I _e which is a chain alkyl, or C _m H _f F _g Cl _h Br _i I containing a cyclic alkyl in the chemical structure. selected from _j , n is an integer of 1 or more, m is an integer of 3 or more, a, b, c, d, e, f, g, h, i, j are each independently an integer of 0 or more 2n + 1 = a + b + c + d + e, 2m = f + g + h + i + j is satisfied.)   The lithium ion secondary battery according to claim 1 or 2, wherein the chain carbonate is contained in an amount of 80% by volume or more or 80% by mole or more based on the organic solvent.   The lithium ion secondary battery according to any one of claims 1 to 3, wherein the lithium salt is contained in an amount of 80 mass% or more or 80 mol% or more based on the electrolyte. The lithium ion secondary battery according to any one of claims 1 to 4, wherein a chemical structure of the lithium salt is represented by the following general formula (1-1).
(R ³ X ² ) (R ⁴ SO ₂ ) NLi General formula (1-1)
(R ³ and R ⁴ are each independently C _n H _a F _b Cl _c Br _d I _e (CN) _f (SCN) _g (OCN) _h .
n, a, b, c, d, e, f, g, and h are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e + f + g + h.
R ³ and R ⁴ may combine with each other to form a ring, in which case 2n = a + b + c + d + e + f + g + h is satisfied.
X ^{2 _{is, SO 2, C = O,}} C = S, R c P = O, R d P = S, S = O, is selected from Si = O.
R ^c and R ^d are each independently hydrogen, halogen, an alkyl group that may be substituted with a substituent, a cycloalkyl group that may be substituted with a substituent, or a group that may be substituted with a substituent. A saturated alkyl group, an unsaturated cycloalkyl group that may be substituted with a substituent, an aromatic group that may be substituted with a substituent, a heterocyclic group that may be substituted with a substituent, and a substituent An alkoxy group which may be substituted, an unsaturated alkoxy group which may be substituted with a substituent, a thioalkoxy group which may be substituted with a substituent, an unsaturated thioalkoxy group which may be substituted with a substituent, OH , SH, CN, SCN, and OCN.
R ^c and R ^d may combine with R ³ or R ⁴ to form a ring. ) The lithium ion secondary battery according to any one of claims 1 to 5, wherein a chemical structure of the lithium salt is represented by the following general formula (1-2).
(R ⁵ SO ₂ ) (R ⁶ SO ₂ ) NLi Formula (1-2)
(R ⁵ and R ⁶ are each independently C _n H _a F _b Cl _c Br _d I _e .
n, a, b, c, d, and e are each independently an integer of 0 or more, and satisfy 2n + 1 = a + b + c + d + e.
R ⁵ and R ⁶ may combine with each other to form a ring, in which case 2n = a + b + c + d + e is satisfied. ) The lithium salt is (CF ₃ SO ₂ ) ₂ NLi, (FSO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) ₂ NLi, FSO ₂ (CF ₃ SO ₂ ) NLi, (SO ₂ CF ₂ CF ₂ SO ₂ The lithium ion secondary battery according to claim 1, which is NLi) or (SO ₂ CF ₂ CF ₂ CF ₂ SO ₂ ) NLi.   The lithium ion secondary battery according to any one of claims 1 to 7, wherein the chain carbonate is one type, two types, or three types selected from dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. The lithium ion secondary battery according to any one of claims 1 to 8, which satisfies any of the following (A) to (H).
(A) The porosity of the positive electrode active material layer included in the positive electrode is 50% or less. (B) The density of the positive electrode active material layer included in the positive electrode is 2.5 g / cm ³ or more. (C) One existing on the current collector of the positive electrode. (D) The thickness of one positive electrode active material layer present on the positive electrode current collector is 15 μm or more. (E) The porosity of the negative electrode active material layer of the negative electrode is at least 3 mg / cm ^2. 50% or less (F) The density of the negative electrode active material layer of the negative electrode is 1.1 g / cm ³ or more. (G) The amount of one negative electrode active material layer present on the negative electrode current collector is 2 mg / cm ² or more. H) The thickness of one negative electrode active material layer present on the negative electrode current collector is 30 μm or more.   The method for charging a lithium ion secondary battery according to claim 1, wherein charging is performed at a rate greater than a 30 C rate. 10. The method for discharging a lithium ion secondary battery according to claim 1, wherein discharging is performed at a rate higher than a 30C rate.