JP5553170B2 - Lithium ion secondary battery - Google Patents

Description

  The present invention relates to a lithium ion secondary battery that can be used even at higher voltages.

  A lithium ion secondary battery includes positive and negative electrodes capable of reversibly occluding and releasing lithium ions, and a separator interposed between the two electrodes. The separator is impregnated with a nonaqueous electrolytic solution, and charging and discharging are performed by lithium ions in the electrolytic solution moving between the electrodes. Because it is lightweight and has high energy density, it is widely used as a power source for various portable devices. Moreover, utilization is anticipated also in the field | area which requires large capacity | capacitance power supplies, such as a vehicle, and the higher energy density is calculated | required. Patent documents 1 and 2 are mentioned as technical literature about a lithium ion secondary battery.

JP 2007-524204 A JP 2010-205663 A

The increase in energy density can be realized, for example, by increasing the voltage of the battery (increasing the upper limit voltage during use). As a means for increasing the voltage, for example, as a positive electrode material, a potential higher than the upper limit voltage in a typical usage mode of a general lithium ion secondary battery (for example, the positive electrode potential is 4.3 V (vs. Li / Li ⁺ The use of a lithium transition metal compound that can function suitably as a positive electrode active material is also being investigated in the embodiment charged to above). However, when a battery using such a positive electrode active material is fully charged, the potential applied to the separator surface on the side facing the positive electrode is increased, and the material constituting the separator surface (typically a polyolefin resin) is oxidized. The separator may deteriorate. As a result, a decrease in capacity and an increase in DC resistance may occur.

  An object of the present invention is to provide a lithium ion secondary battery that can be suitably used under conditions of a high upper limit voltage value (for example, 4.3 V or more). Another object of the present invention is to provide a power supply device using such a lithium ion secondary battery.

According to the present invention, a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, a separator disposed between these electrodes, a positive electrode side electrolyte composition E _C including a nonaqueous solvent and a supporting salt, _A lithium ion secondary battery comprising a negative electrode side electrolyte composition EA containing an aqueous solvent and a supporting salt is provided. One of the positive and negative electrode side electrolyte compositions E _C and E _A is in the form of a solution, and the other is in the form of a gel. The gel electrolyte composition (hereinafter sometimes referred to as electrolyte gel) is at least partially disposed between the positive electrode and the separator. The oxidation potential of the non-aqueous solvent contained in the positive electrode side electrolyte composition _{E C} (vs. Li / Li ^+), higher than the oxidation potential of the negative electrode side electrolyte composition _{E A} (relative to Li / Li ⁺⁾ or (typically Is 0.1 V or higher, preferably 0.2 V or higher, for example, about 0.3 V to 1.0 V higher).

Here, “positive electrode side electrolyte composition” means “electrolyte composition arranged so as to contact the positive electrode”, and “negative electrode side electrolyte composition” means “electrolyte composition arranged so as to contact the negative electrode” "Means. The electrolyte gel is disposed between the positive electrode and the separator (porous insulating layer). In one embodiment, the positive-side electrolyte composition E _C forms a gel. The lithium ion secondary battery of this aspect, the electrolyte gel E _C is typically in the positive electrode having a porous layer containing a positive electrode active material (positive electrode active material layer), at least on the surface of the porous layer Granted (held; applied). In a preferred embodiment, the electrolyte gel also enters (soaks) in at least a part of the positive electrode active material layer (typically, at least a part close to the surface of the positive electrode active material layer). In another aspect, forming the negative electrode side electrolyte composition E _A gelled. The lithium ion secondary battery of this aspect, the electrolyte gel E _A (typically, a porous olefin resin sheet) porous separator porous layer containing a negative electrode active material from the positive electrode surface facing (negative electrode active material Layer). In a preferred embodiment, fine pores (pores) of the separator and at least a part of the negative electrode active material layer (typically, pores and through-holes near the positive electrode facing surface of the separator, and at least the surface of the negative electrode active material layer) Electrolyte gel also enters the pores in the adjacent part. The "oxidation potential of the non-aqueous solvent contained in the positive electrode side electrolyte composition _{E C} (vs. Li / Li ^+), higher than the oxidation potential of the negative electrode side electrolyte composition _{E A} (relative to Li / Li ⁺⁾ or" (which may be a mixture of non-aqueous solvents of two or more.) a non-aqueous solvent contained in the electrolyte composition E _C oxidation potential measured for a non-aqueous solvent (of two or more contained in the electrolyte composition E _a It may be a mixture of non-aqueous solvents). Here, the oxidation potential (which can also be grasped as the oxidative decomposition start potential) is a case where constant voltage charging is performed while gradually increasing the voltage for the evaluation cell in the oxidation potential measurement method described later. The potential when the current value is greater than 0.1 mA.

In such a lithium ion secondary battery, the gel electrolyte composition is disposed between the positive electrode and the separator, and the situation in which the separator and the positive electrode are in close contact with each other can be avoided (typically, the separator). And a desired distance can be ensured between the positive electrode and the positive electrode). Thus, even when the battery is charged to a high potential, the separator surface is hardly deteriorated (deterioration due to oxidation or the like) due to the influence of the positive electrode potential. In addition, since the electrolyte composition on one electrode side is in a solution state, the electrolyte composition on the other electrode side is in a gel state, and therefore, they can be maintained in a separated state without being mixed. Therefore, it is possible to control the characteristics (oxidation resistance, reduction resistance, etc.) of these electrolyte compositions separately. Moreover, the separation of such electrolyte composition, direct contact with the electrolyte composition E _C and the negative electrode, and direct contact with the electrolyte composition E _A and the positive electrode can be prevented. Thus, for example, by forming the E _C electrolyte composition with high oxidation resistance nonaqueous solvent, reductive decomposition of the solvent in the anode can be substantially avoided. Further, by forming the electrolyte composition E _A with high reduction resistance nonaqueous solvent, said solvent or altered or decomposed by oxidation at the positive electrode (a result, a high-resistance film is formed The phenomenon that the battery performance can be lowered by this or the like can be suppressed. For these reasons, for example, a higher voltage value (for example, 4.3 V or more) than a conventional general lithium ion secondary battery can be suitably used, and even when stored in a fully charged state, a decrease in capacity or direct current is possible. A lithium ion secondary battery with little increase in resistance can be realized.

In one preferred embodiment, the nonaqueous solvent contained in the positive electrode side electrolyte composition E _C, the oxidation potential (vs. Li / Li ⁺⁾ is equal to or higher than 4.3 V. Here, when the non-aqueous solvent is a mixture of two or more kinds of non-aqueous solvents (mixed solvent), “the oxidation potential (vs. Li / Li ⁺ ) of the non-aqueous solvent contained in the positive electrode side electrolyte composition E _C is “Higher than 4.3V” means that the oxidation potential measured for the entire non-aqueous solvent is higher than 4.3V. The lithium ion secondary battery of this aspect can be suitably used under the condition that the upper limit voltage is 4.3 V or higher. In a preferred embodiment, the oxidation potential measured for each component (non-aqueous solvent) contained in the mixed solvent is higher than 4.3V.

In another preferred embodiment, a non-aqueous solvent contained in the positive electrode side electrolyte composition E _C, the oxidation potential (vs. Li / Li ⁺⁾ is, to a positive electrode active material potential (described later in the fully charged state of the cell operation It is characterized by being higher than (vs. Li / Li ⁺ ). In such lithium ion secondary battery, even when fully charged the battery (even when the SOC (State Of Charge) of 100% state), the non-aqueous solvent contained in the electrolyte composition _{E C} is hard to be oxidized and decomposed The increase in resistance of the positive electrode can be suppressed. “Fully charged” refers to charging the battery until the SOC reaches 100% at the upper limit voltage for ensuring a desired capacity (typically, the rated capacity determined by the battery design). “Fully charged state” refers to a state in which the SOC is 100% after charging at the upper limit voltage for securing the desired capacity. Further, “full charge potential (vs. Li / Li ⁺ )” means a positive electrode potential based on metallic lithium at the above upper limit voltage (which can also be grasped as the charge upper limit potential of the charge / discharge control system).

In another preferred embodiment, more than 95% by volume of the nonaqueous solvent contained in the positive electrode side electrolyte composition E _C consists of at least one fluorinated carbonate. Fluorinated carbonates tend to have higher oxidation potentials (vs. Li / Li ⁺ ) than the corresponding carbonates. Therefore, such a lithium ion secondary battery can be used even at a higher upper limit voltage setting, and even when stored in a fully charged state, the capacity can be reduced and the direct current resistance can be increased little.

  In another preferred embodiment, the separator includes polypropylene. In the lithium ion secondary battery of this aspect, it is preferable that at least the positive electrode facing surface of the separator is substantially made of polypropylene. Since polypropylene has high oxidation resistance, there is an advantage that it is difficult to be oxidized even at a higher potential.

  As another aspect of the technology disclosed herein, a power supply comprising the lithium ion secondary battery disclosed herein and a control circuit electrically connected to the battery and defining at least an upper limit voltage value of the battery An apparatus is provided. Here, the upper limit voltage value is set to 4.3 V or higher. Such a power supply device can be one in which the capacity reduction of the lithium ion secondary battery is small even at the relatively high upper limit voltage value.

  As described above, the lithium ion secondary battery disclosed herein can be suitably used even under conditions of an upper limit voltage value higher than that of a conventional general lithium ion secondary battery, for example, even when stored in a fully charged state. Since there is little decrease in capacity and increase in DC resistance, it is suitable as a power source used in vehicles. Therefore, according to this invention, the vehicle provided with one of the lithium ion secondary batteries disclosed here is provided. In particular, a vehicle (for example, an automobile) including such a lithium ion secondary battery as a power source (typically, a power source of a hybrid vehicle or an electric vehicle) is preferable.

It is a perspective view which shows typically the external shape of the lithium ion secondary battery which concerns on one Embodiment. It is the II-II sectional view taken on the line in FIG. It is a side view which shows typically the vehicle (automobile) provided with the lithium ion secondary battery of this invention. It is sectional drawing which shows typically the structural concept of the lithium ion secondary battery which concerns on one embodiment of this invention. It is sectional drawing which shows typically the structural concept of the lithium ion secondary battery which concerns on another one embodiment of this invention. It is a FT-IR chart measured about the separator used in Examples 1-4 with respect to the positive electrode counter surface before use. 5 is an FT-IR chart measured for the separator according to Example 1 with respect to the positive electrode facing surface after the cycle test. It is a FT-IR chart which measured about the separator concerning Example 2 to the cathode opposed side after a cycle test. 5 is an FT-IR chart measured for the separator according to Example 3 with respect to the positive electrode facing surface after the cycle test. It is a FT-IR chart measured about the separator concerning Example 4 with respect to the cathode opposing surface after a cycle test. It is explanatory drawing which shows the power supply system containing the lithium ion secondary battery which concerns on one Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. In the following drawings, members / parts having the same action are described with the same reference numerals, and redundant descriptions may be omitted or simplified. In addition, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships.

  4 and 5, lithium ion secondary batteries 600 and 700 according to an embodiment of the present invention include a positive electrode 530 having a positive electrode active material layer 534 on a positive electrode current collector 532 in a container 510, and A negative electrode 540 having a negative electrode active material layer 544 on a negative electrode current collector 542, a separator (an insulating layer through which a solution-like electrolyte composition can permeate) 550 disposed between both electrodes, an electrolytic solution 586, and an electrolyte gel Layer 587. The positive electrode active material layer 534 is a layer mainly containing the positive electrode active material 534A, and the negative electrode active material layer 544 is a layer mainly containing the negative electrode active material 544A.

FIG. 4 schematically shows a lithium ion secondary battery 600 having a configuration in which an electrolyte gel layer 587 is disposed on the positive electrode side and an electrolyte solution 586 is disposed on the negative electrode side. In other words, electrolyte gel 587 (corresponding to the electrolyte composition _{E C.)} Are coated with a cathode active material layer 534, whereby the positive electrode active material layer 534 and the separator 550 (and thus the anode active material layer 544) and at least an electrolyte The gel 587 is isolated. On the other hand, (corresponding to the electrolyte composition E _A.) The electrolyte solution 586 is disposed is impregnated in the separator 550, thereby directly contact the but positive electrode active material layer 534 in contact with the anode active material layer 544 It is included in the battery 600 so that it does not.

FIG. 5 schematically shows a lithium ion secondary battery 700 having a configuration in which an electrolyte gel 587 is disposed on the negative electrode side and an electrolyte solution 586 is disposed on the positive electrode side. Here, electrolyte gel 587 (corresponding to the electrolyte composition _{E A.)} Is coated with a positive electrode opposing surface 550A of separator 550, whereby a positive electrode active material layer 534 and the separator 550 interposed therebetween at least electrolyte gel 587 It has an isolated configuration. Further, (corresponding to the electrolyte composition E _C.) The electrolyte solution 586 is in contact with the positive electrode active material layer 534, are included in the battery 700 to prevent direct contact to the anode active material layer 544 . Since the positive electrode active material layer 534 is impregnated with the electrolytic solution 586, and the electrolytic solution 586 can exist as a liquid film between the positive electrode active material layer 534 and the electrolyte gel layer 587, the electrolyte gel 587 also has the positive electrode active material layer 534. It is difficult to directly contact the material layer 534. In a preferred embodiment, the electrolyte gel 587 penetrates from the positive electrode facing surface 550A of the separator 550 to at least some of the pores inside the separator 550 and the negative electrode facing surface 550B, and is formed so as to be in direct contact with the negative electrode active material layer 544. Has been. More preferably, the electrolyte gel 587 further enters at least the pores near the surface of the negative electrode active material layer 544.

The positive electrode of the lithium ion secondary battery disclosed here is, for example, a lithium ion secondary battery having a general operating potential (vs. Li / Li ⁺ ) in at least a part of SOC 0% to 100% (operating potential). A positive electrode active material whose upper limit is higher than about 4.1 V). For example, a positive electrode active material having an SOC range in which the operating potential (vs. Li / Li ⁺ ) is higher than 4.3V (in other words, the positive electrode active material having the highest operating potential at SOC 0% to 100% higher than 4.3V). Substance) can be preferably used. Examples of the positive electrode active material that can be preferably used include LiNi _P Mn _{2 -P} O ₄ (0.2 ≦ P ≦ 0.6; for example, LiNi _0.5 Mn _1.5 O ₄ ), LiNiPO ₄ , LiCoPO ₄ , Li ₂ MnO ₃ etc. are illustrated.

Here, as the operating potential, a value measured as follows is adopted. That is, a positive electrode containing a positive electrode active material to be measured, metallic lithium as a counter electrode, metallic lithium as a reference electrode, and LiPF ₆ having a concentration of 1 M in a mixed solvent of EC: DMC = 30: 70 (volume basis). A triode cell is constructed using the electrolyte solution. Based on the theoretical capacity of the cell, the SOC is adjusted in increments of 5% from 0% SOC to 100% SOC (for example, adjustment is performed by constant current charging). At this time, after each cell is allowed to stand for 1 hour at each SOC value, the positive electrode potential (vs. Li / Li ⁺ ) is measured to obtain the operating potential at the SOC value of the positive electrode active material.

Normally, the operating potential of the positive electrode active material is highest in a range including SOC 100% between SOC 0% and 100%, so that the operating potential at SOC 100% (that is, fully charged state) is higher than 4.3V. A high positive electrode active material can be grasped as a positive electrode active material having an SOC range in which the operating potential is higher than 4.3V. The operating potential of the positive electrode active material in a fully charged state (vs. Li / Li ⁺ ) (hereinafter sometimes referred to as “the full charge potential of the positive electrode active material”) is more preferably higher than 4.4V. More preferably, it is higher than 5V. The technology disclosed herein is typically preferably applied to a lithium ion secondary battery in which the positive electrode active material has a full charge potential (vs. Li / Li ⁺ ) of 7.0 V or less (for example, 5.0 V or less). The

  The electrolyte gel of the aspect provided to the positive electrode includes, for example, a precursor solution obtained by adding a polymer precursor, a polymerization initiator, and the like to a nonaqueous electrolytic solution containing a supporting salt in a nonaqueous solvent (organic solvent) for the positive electrode. After imparting to a desired positive electrode active material layer, it can be formed by maintaining and gelling under appropriate conditions (for example, by allowing the polymerization reaction to proceed). Typically, the positive electrode active material layer is sufficiently impregnated with the precursor solution, and an excessive amount of the precursor solution is appropriately removed from the active material layer in accordance with a desired amount of the electrolyte gel. It is subjected to the polymerization reaction under the temperature (temperature etc.)

  The electrolyte gel of the aspect provided to the positive electrode opposing surface of the separator has, for example, a nonaqueous electrolytic solution containing a supporting salt in the negative electrode nonaqueous solvent (organic solvent) on the surface of the separator (that is, the positive electrode opposing surface). It can be formed by applying a precursor solution prepared in the same manner and then subjecting it to gelation under appropriate conditions. Typically, the separator is overlaid on the negative electrode with the positive electrode facing side facing up (outside), and the precursor solution is applied, and the precursor solution is applied to the pores of the separator, and further to the negative electrode. The active material layer is sufficiently impregnated, and an excessive amount of the precursor solution is appropriately removed from the separator surface according to the desired amount of electrolyte gel, and then subjected to a polymerization reaction under appropriate conditions (temperature, etc.). Thereby, the battery of the aspect in which this precursor solution electrolyte gel as described above entered at least the surface of the inside of the separator and the negative electrode active material layer can be realized. The battery of this aspect can be one in which the function of the electrolyte gel as the negative electrode side electrolyte composition is sufficiently exhibited, and the decrease in the conductive efficiency in the negative electrode is suppressed.

  In any embodiment, the polymerization temperature at the time of gelation may be appropriately selected, and may be, for example, about 80 to 140 ° C. The polymerization time may be appropriately selected and can be set to, for example, about 5 minutes to 3 hours. The “polymerization reaction” herein may be any one that can contribute to the gelation (curing) of the precursor solution, and may be, for example, a crosslinking reaction, a condensation reaction, or the like. The application of the precursor solution may be performed, for example, under reduced pressure or under vacuum. The excess of the precursor solution is removed by extruding the excess solution while applying an appropriate pressure (for example, about 0.01 MPa to 0.1 MPa) to the solution application surface after the impregnation treatment. Can do.

The thickness of the electrolyte gel layer (the thickness of the portion laminated on the surface of the positive electrode active material layer (distance from the surface of the positive electrode active material layer to the surface of the electrolyte gel layer); or the thickness of the portion laminated on the surface facing the separator positive electrode ( The distance from the positive electrode surface of the separator to the surface of the electrolyte gel layer is not particularly limited, from the viewpoint of increasing the output efficiency (Li ⁺ conductivity) by shortening the lithium ion movement distance; In consideration of these balances, the thickness can be set to about 10 μm to 100 μm, for example.

  As the polymer precursor, only one kind of material (which may be a monomer or an oligomer) whose characteristics (electrochemical stability, thermal stability, etc.) after gelation are suitable for the desired battery configuration and use conditions is used. It can be used alone or in combination of two or more. The polymer precursor can be multifunctional or monofunctional. Usually, a polymer precursor (polyfunctional polymer precursor) having two or three or more polymerizable (crosslinkable) functional groups is preferably used. Examples of preferred polymer precursors include polyethylene oxide (PEO), polypropylene oxide (PPO), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF). Typically, a polymer precursor having a thermally polymerizable (thermally crosslinkable) functional group is used. Specific examples of the polymer precursor preferably used in the technology disclosed herein include, for example, product number “TA140” manufactured by Daiichi Kogyo Seiyaku Co., Ltd. and similar products. What is necessary is just to select the usage-amount of the said polymer precursor suitably according to the desired degree of gelation etc., for example, can be about 10-17 mass% of the said precursor solution.

  The said polymerization initiator can be suitably selected and used according to the kind of polymer precursor to be used. Typically, a thermal polymerization initiator is used. As the thermal polymerization initiator, various conventionally known initiators such as azo type and peroxide type can be used. Preferred polymerization initiators include azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO) and the like. What is necessary is just to select the usage-amount of the said polymerization initiator suitably, for example, it can be set as about 0.1-3 mass% with respect to the said polymer precursor.

The positive electrode non-aqueous solvent (non-aqueous solvent contained in the positive electrode side electrolyte composition _{E C),} the oxidation potential (vs. Li / Li ⁺⁾ is fully charged potential of the positive electrode active material to be used (relative to Li / Li ⁺⁾ It is preferable to use a high organic solvent as appropriate. Preferably, the oxidation potential (vs. Li / Li ⁺ ) is 0.1 V or higher (eg, 0.2 V or higher, 0.3 V or higher) than the full charge potential (vs. Li / Li ⁺ ) of the positive electrode active material. 0.5V or higher.) High organic solvents can be used. Such organic solvents can be used alone or in combination of two or more. In the lithium ion secondary battery having such a configuration, the oxidation potential (vs. Li / Li ⁺ ) of the organic solvent in the electrolyte composition Q in contact with the positive electrode active material is higher than the positive electrode potential when the SOC of the battery is 100%. Can also be expensive. Therefore, the oxidative decomposition of the solvent at the positive electrode can be suppressed to a higher degree. Of the total amount of the nonaqueous solvent contained in the electrolyte composition E _C, the amount occupied by the organic solvent having high oxidation potential than full charge potential of the positive electrode active material to be used is preferably from an amount of more than 50% by volume, More preferably, it is 75 volume% or more, More preferably, it is 90 volume% or more (for example, 95 volume% or more), and substantially all (for example, 98 volume% or more, typically 100 volume%) may be sufficient.

  As the non-aqueous solvent for the positive electrode, a fluorinated organic solvent is typically used. Preferred fluorinated organic solvents include fluoroethylene carbonate (FEC), trifluorodimethyl carbonate (TFDMC), difluorodimethyl carbonate (methyl difluoromethyl carbonate, di (fluoromethyl) carbonate), fluorinated esters, fluorinated ethers and the like. Examples thereof include carbonates (which may be cyclic, linear, or branched). Of the non-aqueous solvent contained in the electrolyte composition Q, typically 50% by volume or more, for example, 75% by volume or more (more preferably 95% by volume or more, more preferably 99% by volume or more) It is preferable that it is at least one of carbonates. Substantially all of the non-aqueous solvent may be one or more fluorinated carbonates.

In addition, the value measured according to the following method shall be employ | adopted as an oxidation potential (vs. Li / Li ^<+> ) of a nonaqueous solvent.
A working electrode is prepared using LiFePO ₄ . Specifically, LiFePO ₄ , acetylene black (conductive material), and PVDF (binder) are mixed so that the mass ratio thereof is 85: 5: 10, and N-methyl-2-pyrrolidone (NMP To prepare a slurry-like composition. This is applied in the form of an aluminum foil, and dried and roll-pressed to produce a working electrode (positive electrode) sheet. A three-electrode cell is constructed using the working electrode, metallic lithium as a counter electrode, metallic lithium as a working electrode, and an electrolytic solution to be measured. The triode cell is treated to completely desorb Li from the working electrode. Specifically, at a temperature of 25 ° C., constant current charging is performed up to 4.2 V at a current value that is 1/5 of the battery capacity (Ah) predicted from the theoretical capacity of the working electrode, and the current value is initial at 4.2 V. The constant voltage charging is performed until the current value becomes 1/50 of the current value (that is, the current value that is 1/5 of the battery capacity). Next, constant voltage charging is performed for a predetermined time (for example, about 10 hours) at an arbitrary voltage in a voltage range (typically a voltage range higher than 4.2 V) predicted to include the oxidation potential of the electrolyte to be measured. ) And measure the current value at that time. More specifically, the voltage is increased stepwise (for example, in steps of 0.2 V) within the voltage range, and constant voltage charging is performed for a predetermined time (for example, about 10 hours) at each step. Measure the current value. The potential when the current value during constant voltage charging is greater than 0.1 mA is defined as the oxidation potential of the electrolytic solution.

As the support salt of the positive-side electrolyte composition E _C, ordinary lithium salt used in the lithium ion secondary battery as a supporting salt, can be appropriately selected and used. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li (CF ₃ SO ₂ ) ₂ N, LiCF ₃ SO _{3 and the} like. These supporting salts can be used alone or in combination of two or more. A particularly preferred example is LiPF ₆ . (If positive side electrolyte composition E _C is a solution form, equal to the composition E _C.) Positive electrode non-aqueous electrolyte solution prepared from with such supporting salt positive electrode non-aqueous solvents are, for example, the supporting salt The concentration of is preferably in the range of 0.7 to 1.3 mol / L.

The Fukyokuyo nonaqueous solvent (nonaqueous solvent contained in the negative electrode side electrolyte composition E _A), used in the common electrolyte of lithium ion secondary batteries, as appropriate reductive decomposition occurs hardly organic solvent at the negative electrode You can select and use. These organic solvents can be used alone or in combination of two or more. For example, carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), diethyl carbonate (DEC), and propylene carbonate (PC) (which may be cyclic, linear or branched). May be used). It is preferable to use at least one of these carbonates. For example, a mixed solvent of EC and DMC can be preferably used. In addition, some of these solvents form a surface coating (SEI; Solid Electrolyte Interface) having a function of suppressing side reactions (such as reductive decomposition) on the negative electrode surface by reductive decomposition on the negative electrode surface. obtain.

As the support salt of the anode side electrolyte composition E _A, described above can be used similarly to the supporting salt contained in the positive electrode side electrolyte composition E _C, common supporting salt for lithium ion secondary batteries. Typically, the same supporting salt as that used in the electrolyte composition E _C is used. A particularly preferred example is LiPF ₆ . Negative electrode for non-aqueous electrolyte prepared from and according supporting salt Fukyokuyo nonaqueous solvent (if negative electrode side electrolyte composition E _A is a solution form is equal to the composition E _A.), For example, the support The salt concentration is preferably in the range of 0.7 to 1.3 mol / L.

  The matter disclosed in this specification includes any of the lithium ion secondary batteries disclosed herein having an upper limit voltage value of 4.3 V or higher (typically 4.5 V or higher, for example, 4.7 V or higher. ) And a method for use under the charge / discharge conditions set. Further, such a lithium ion secondary battery (may be in the form of an assembled battery in which a plurality of batteries are connected in series and / or in parallel) and the battery is set so as to be the above upper limit voltage value. And a power supply device including a control mechanism (control device) that controls the charging / discharging conditions.

  The power supply device, for example, as in the power supply device 800 shown in FIG. 11, operates the load 802 according to the state of the lithium ion secondary battery 600, the load 802 connected thereto, and the lithium ion secondary battery 600. The electronic control unit (ECU) 804 to be adjusted may be included. The load 802 may include a power consumer that consumes the power stored in the lithium ion secondary battery 600 and / or a power supply device (charger) that can charge the battery 600. Based on the predetermined information, the ECU 804 controls the load 802 so that the upper limit voltage value of the battery 600 becomes a predetermined value (for example, 4.5 V) of 4.3 V or higher. A typical configuration of the ECU 804 includes at least a ROM (Read Only Memory) storing a program for performing such control, and a CPU (Central Processing Unit) capable of executing the program. As the predetermined information, for example, one or more information among the voltage of the battery 600, each electrode potential, charge / discharge history, and the like can be used. A lithium ion secondary battery 600 disclosed herein includes, for example, a vehicle (typically an automobile, particularly a hybrid automobile, an electric automobile) as shown in FIG. 3 as a component of a power supply device 800 as shown in FIG. , An automobile equipped with an electric motor such as a fuel cell automobile).

Hereinafter, for a lithium ion secondary battery disclosed herein with reference to the drawings, a battery case in which an electrode body including positive and negative electrodes and electrolyte compositions E _A and E _C on the positive electrode side and the negative electrode side are square-shaped. The lithium ion secondary battery 100 (FIG. 1) of the aspect accommodated in FIG. Here it is employed a mode in which E _C positive side electrolyte composition is gelled, not intended to be limited to the embodiments according to the application of the present invention. That is, the shape of the lithium ion secondary battery according to the present invention is not particularly limited, and the battery case, electrode body, and the like can be appropriately selected in terms of material, shape, size, and the like according to the application and capacity. For example, the battery case may have a rectangular parallelepiped shape, a flat shape, a cylindrical shape, or the like. The negative electrode side electrolyte composition E _A can also be a gelled manner.

As shown in FIGS. 1 and 2, the lithium ion secondary battery 100 includes a wound electrode body 20 together with an electrolyte composition E _C (electrolyte) (represented by reference numeral 66) and the shape of the electrode body 20. It can be constructed by accommodating the inside of the flat box-shaped battery case 10 corresponding to the above and opening the opening 12 of the case 10 with the lid 14. The lid body 14 is provided with a positive terminal 38 and a negative terminal 48 for external connection so that a part of the terminals protrudes to the surface side of the lid body 14.

In the electrode body 20, a positive electrode active material layer 34 is formed on the surface of a long sheet-like positive electrode current collector 32, and an electrolyte composition E _C (electrolyte gel) (represented by reference numeral 67) is applied. A sheet 30 and a negative electrode sheet 40 having a negative electrode active material layer 44 formed on the surface of a long sheet-like negative electrode current collector 42 are typically stacked together with two long sheet-like separators 50. It is formed into a flat shape by winding and crushing the obtained wound body from the side surface direction.

  The positive electrode sheet 30 has a positive electrode current collector 32 exposed at one end along the longitudinal direction. Similarly, in the negative electrode sheet 40 to be wound, the negative electrode current collector 42 is exposed at one end portion along the longitudinal direction. Then, the positive electrode terminal 38 is joined to the exposed end portion of the positive electrode current collector 32, and the negative electrode terminal 48 is joined to the exposed end portion of the negative electrode current collector 42, respectively. The positive electrode sheet 30 or the negative electrode sheet 40 is electrically connected. The positive and negative terminals 38 and 48 and the positive and negative current collectors 32 and 42 can be joined by, for example, ultrasonic welding, resistance welding, or the like.

As described above, for example, the positive electrode sheet 30 is formed by using a suitable solvent (for example, N-methyl-2-pyrrolidone (NMP), etc.) together with the above-described positive electrode active material as necessary, together with a conductive material, a binder, and the like. The paste-like or slurry-like composition (positive electrode mixture) dispersed in () is applied to the positive electrode current collector 32, and the positive electrode active material layer is formed by drying the composition. , according to the above-described method was sufficiently impregnated with the precursor solution, after removing it if any precursor solution of excess, subjected to polymerization reaction to impart a gel phase 67 consisting of electrolytic composition E _C This can be preferably produced. The amount of the positive electrode active material contained in the positive electrode active material layer can be, for example, about 69 to 98% by mass.

As the conductive material, a conductive powder material such as carbon powder or carbon fiber is preferably used. As the carbon powder, various carbon blacks such as acetylene black, furnace black, ketjen black, and graphite powder are preferable. A conductive material can be used alone or in combination of two or more.
What is necessary is just to select suitably the quantity of the electrically conductive material contained in a positive electrode active material layer according to the kind and quantity of a positive electrode active material, for example, can be about 1-30 mass%.

  As the binder, one or two or more selected from various binding polymers can be used. For example, an organic solvent-soluble polymer such as polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene oxide-propylene oxide copolymer (PEO-PPO) is used. It can be preferably used. Examples of other usable binders include carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC), hydroxypropylmethylcellulose phthalate (HPMCP), polyvinyl alcohol ( Water-soluble polymers such as PVA); polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoro Fluorine resin such as ethylene copolymer (ETFE), vinyl acetate copolymer, styrene butadiene block copolymer (SBR), acrylic acid modified SBR resin (SBR latex), polymer Rubber such as Biagomu (water dispersible polymer); and the like. What is necessary is just to select the quantity of the binder contained in a positive electrode active material layer suitably according to the kind and quantity of a positive electrode active material and a electrically conductive material, for example, it can be set as about 1-10 mass%.

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

  The negative electrode sheet 40 includes, for example, a paste or slurry composition (negative electrode mixture) in which a negative electrode active material is dispersed in an appropriate solvent together with a binder (binder) as necessary. It can be preferably prepared by forming the negative electrode active material layer 44 by drying the resultant and drying it.

  As the negative electrode active material, one type or two or more types of materials conventionally used in lithium ion secondary batteries can be used without any particular limitation. For example, a particulate carbon material (carbon particles) including a graphite structure (layered structure) at least in part can be used. Any of so-called graphitic (graphite), non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), and those having a combination of these may be preferably used. Specific examples include natural graphite.

  As the binder, one kind or two or more kinds selected from those similar to the above-described positive electrode can be used. The amount of the binder contained in the negative electrode active material layer is not particularly limited, and may be appropriately selected according to the type and amount of the negative electrode active material.

  As the negative electrode current collector 42, a conductive member made of a metal having good conductivity is preferably used. For example, copper or an alloy containing copper as a main component can be used. In addition, the shape of the negative electrode current collector 42 may vary depending on the shape of the lithium ion secondary battery and the like, and thus is not particularly limited, and may be various forms such as a rod shape, a plate shape, a sheet shape, a foil shape, and a mesh shape. possible. In the present embodiment, a sheet-like copper negative electrode current collector 42 is used, and can be preferably used for the lithium ion secondary battery 100 including the wound electrode body 20. In this embodiment, for example, a copper sheet having a thickness of about 6 μm to 30 μm can be preferably used.

The separator 50 (corresponding to the porous plastic layer described above) is a layer interposed between the positive electrode sheet 30 and the negative electrode sheet 40 and typically has a sheet shape, and the surface of the positive electrode sheet 30 (electrolyte composition). The positive electrode active material layer 34) whose surface is coated with E _C and the negative electrode sheet 40 surface (negative electrode active material layer 44) are arranged in contact with each other. The short-circuit preventing or accompanying the contact of the electrodes active material layer 34, 44 in the positive electrode sheet 30 and negative electrode sheet 40, the inter-electrode by impregnating a solution like electrolyte composition E _A described above in the pores of the separator 50 It plays a role of forming a conduction path (conduction path). As this separator 50, a conventionally well-known thing can be especially used without a restriction | limiting. For example, a porous sheet made of resin (a microporous resin sheet) can be preferably used. A porous polyolefin resin sheet such as polyethylene (PE), polypropylene (PP), and polystyrene is preferred. Either a single layer structure sheet or a multilayer structure sheet may be used. Preferable examples of such porous plastic layers include porous polyolefin films such as PP / PE / PP trilayer films and PE single layer films. It is particularly preferable to use a porous polyolefin film having a PP layer with high oxidation resistance on at least the positive electrode side surface. The thickness of the separator is preferably set within a range of approximately 10 μm to 40 μm, for example.

Here, when adopting a mode in which negative electrode side electrolyte composition E _A is gelled, using the negative electrode sheet in which the electrolyte gel comprising on each side a separator granted, the positive electrode sheet in which the electrolyte gel is not added Thus, a lithium ion secondary battery provided with the wound electrode body can be constructed. Such a separator / negative electrode sheet composite with an electrolyte gel, for example, impregnates a first separator with a precursor solution prepared using a non-aqueous electrolyte for a negative electrode, and places the separator facing the positive electrode facing down. A negative electrode sheet having a negative electrode active material layer is stacked on each surface, and a second separator is stacked with the positive electrode facing surface facing upward, and the above precursor solution is further impregnated on the upper surface, followed by gelation. It can produce by providing. Alternatively, it can also be produced by superposing a separator on one surface of the negative electrode sheet with the positive electrode facing surface facing up, applying an electrolyte gel to this surface, turning it over, and applying the same treatment.

  Hereinafter, some examples relating to the present invention will be described, but the present invention is not intended to be limited to such examples. In the following description, “parts” and “%” are based on mass unless otherwise specified.

<Example 1>
As a positive electrode mixture, LiNi _0.5 Mn _1.5 O ₄ (positive electrode active material), acetylene black (conductive material), and PVDF (binder) so that the mass ratio thereof becomes 87: 10: 3 And a slurry composition was prepared by dispersing in NMP. This positive electrode mixture was applied to one side of an aluminum foil (positive electrode current collector) having a thickness of 15 μm and then dried to form a positive electrode active material layer, which was roll pressed to produce a positive electrode sheet. The positive electrode sheet was cut into a 5 cm × 5 cm square with a 10 mm wide strip protruding at one corner. The active material layer was removed from the belt-like portion, the aluminum foil was exposed to form a terminal portion, and a positive electrode sheet with a terminal portion was obtained.

  As a negative electrode mixture, natural graphite (negative electrode active material; average particle size 20 μm, graphitization degree ≧ 0.9), CMC (thickener), and SBR (binder) have a mass ratio of 98: 1. : 1 was mixed and dispersed in ion-exchanged water to prepare a slurry composition. This negative electrode mixture was applied to one side of a 10 μm thick copper foil (negative electrode current collector) so that the applied amount after drying was about 1: 1.5 in terms of the theoretical capacity ratio between the positive electrode and the negative electrode. After being dried, roll pressing was performed to prepare a negative electrode sheet. This negative electrode sheet was processed into the same area and shape as the above-described positive electrode sheet with terminal portions to obtain a negative electrode sheet with terminal portions.

Non-aqueous electrolyte A was prepared by dissolving LiPF ₆ in a mixed solvent containing FEC and TFDMC (FH ₂ CO (C═O) CHF ₂ ) at a volume ratio of 1: 1 to a concentration of 1 mol / L. Was prepared. According to the above-described method, the voltage is changed by 0.2 V in the range of 4.2 V to 5.2 V, and constant voltage charging is performed for 10 hours at each voltage value. When the oxidation potential was measured, the oxidation potential of the electrolytic solution A was 5.0 to 5.2V.
The positive electrode sheet with terminal part, a separator (porous PP / PE / PP three-layer sheet) cut out to an appropriate size and impregnated with the electrolytic solution A, and the negative electrode sheet with terminal part are stacked in this order. Combined and covered with laminate film. The electrolyte solution A was further injected here, and the film was sealed to construct a laminated cell type battery having a theoretical capacity (1C capacity; 1C is a current value that can be fully charged and discharged in 1 hour) of 30 mAh.

<Example 2>
LiPF ₆ was dissolved to a concentration of 1 mol / L in a mixed solvent containing EC and DMC at a volume ratio of 1: 1 to prepare a non-aqueous electrolyte B. A laminated cell battery having a 1 C capacity of 30 mAh was constructed in the same manner as in Example 1 except that the nonaqueous electrolyte B was used instead of the nonaqueous electrolyte A. In addition, the oxidation potential of the electrolytic solution B measured in the same manner as described above was 4.6 to 4.8V.

<Example 3>
To a mixture of 90 parts of electrolyte A and 10 parts of PEO polymer precursor (Daiichi Kogyo Seiyaku Co., Ltd., product number “TA140”), 0.1 part of AIBN (thermal polymerization initiator) was added and stirred. A precursor solution was obtained. After applying this precursor solution onto the positive electrode active material layer of the positive electrode sheet of Example 1 at an extrusion pressure of 0.05 MPa, the positive electrode sheet was held in a drying furnace at a temperature of 60 ° C. for 120 minutes to proceed the polymerization reaction, A positive electrode sheet provided with the electrolyte gel pA was produced. The distance from the positive electrode sheet surface to the pA gel layer surface (the thickness of the gel pA layer) was 50 μm. This positive electrode sheet with pA gel was processed into the same area and shape as in Example 1 to provide a terminal portion.

  The positive electrode sheet with pA gel with terminal part, the separator impregnated with electrolyte B (porous PP / PE / PP three-layer sheet), and the negative electrode sheet with terminal part similar to Example 1 are laminated in this order and laminated. Covered with film. Electrolytic solution B was further injected here, and the film was sealed to construct a laminated cell type battery having a 1 C capacity of 30 mAh.

<Example 4>
To a mixture of 90 parts of electrolyte B and 10 parts of PEO polymer precursor (Daiichi Kogyo Seiyaku Co., Ltd., product number “TA140”), 0.1 part of AIBN (thermal polymerization initiator) was added and stirred. A precursor solution was obtained. A separator (porous PP / PE / PP three-layer sheet) having a thickness of 20 μm is disposed on the negative electrode active material layer of the negative electrode sheet with terminal portion of Example 1, and the precursor solution is extruded onto the separator at a pressure of 0.05 MPa. Then, the polymerization reaction was allowed to proceed in a drying furnace at a temperature of 60 ° C. for 120 minutes to produce a separator / negative electrode sheet composite to which the electrolyte gel pB was applied. The combined thickness of the separator and the pB gel layer was 70 μm (that is, the distance from the separator surface to the pB gel layer surface (pB gel layer thickness) was 50 μm).

  The positive electrode sheet with terminal portions similar to Example 1 and the above-described separator / negative electrode sheet composite with pB gel were overlapped so that the pB gel layer faced the positive electrode active material layer surface of the positive electrode sheet, and covered with a laminate film. It was. The electrolyte solution A was injected between the positive electrode sheet and the gel pB layer, and the film was sealed to construct a laminated cell type battery having a 1 C capacity of 30 mAh.

[Conditioning process]
Each battery cell was sandwiched between two plates and restrained in a state where a load of 350 kgf (350 kg / 25 cm ² ) was applied. For each restrained battery cell, an operation of charging to 4.9 V at a rate of 1/3 C and an operation of discharging to 3.5 V at a rate of 1/3 C were repeated three times. The following measurements and the like were performed on the battery cells that were restrained unless otherwise specified.

[Initial capacity]
For each battery cell according to Examples 1 to 6, CC charging was performed at a temperature of 25 ° C. at a rate of 1/5 C until the voltage between both terminals became 4.9 V, and then the current value was 1/50 C. The battery was charged at a constant voltage (CV) until it became a fully charged state. Next, CC discharge was performed at a rate of 1/5 C until the voltage reached 3.5 V, and the discharge capacity at this time was measured to obtain an initial capacity. Note that the voltage between both terminals when the charger was removed after completion of charging (the state where the overvoltage was released) was about 4.7 to 4.8 V in all cases.

[Initial DC resistance]
Each battery cell after the initial capacity measurement was CC charged at a temperature of 25 ° C. at a rate of 1/5 C until the SOC reached 60%. For each battery cell adjusted to SOC 60%, the battery was charged and discharged at a rate of 1 / 3C, 1C, 3C, and the overvoltage at that time was measured. The resistance was calculated by dividing the measured overvoltage value by the corresponding current value (for example, 10 mA for 1/3 C) to obtain the initial DC resistance.

[Charge / discharge cycle characteristics]
After each battery cell was fully charged by CC-CV charging as in the initial capacity measurement, each battery cell was CC charged to 4.9 V at a rate of 2C at a temperature of 40 ° C. After resting for a minute, CC discharge to 3.5 V at the same rate and a charge / discharge cycle of resting for 10 minutes were repeated 200 cycles. The discharge capacities at the first cycle and the 200th cycle were measured, and the percentage of the 2C discharge capacity at the 200th cycle to the 2C discharge capacity at the first cycle was determined as a capacity retention rate (%). Further, after the completion of 200 cycles, the DC resistance was measured in the same procedure as the initial DC resistance. The resistance increase rate (%) was calculated from the percentage of the DC resistance after the cycle test with respect to the initial DC resistance.

[IR analysis of separator surface]
After completion of the cycle test, each battery was disassembled, the separator was taken out and washed, and then the surface of the separator (the surface on the side opposite to the positive electrode sheet) was subjected to Fourier transform infrared spectroscopy (manufactured by Thermo Fisher Scientific, model “Nicolet 6700”. FT-IR "(germanium prism), analysis was performed under the conditions of microscopic ATR method (total reflection absorption method), 128 scans, and a resolution of 8 cm- ¹ . For the unused separator, the surface used facing the positive electrode was similarly analyzed. These results are shown in FIGS.

  Table 1 shows the configurations of the batteries of Examples 1 to 4, and Table 2 shows the results of the evaluation tests.

As shown in Tables 1 and 2, the battery cell of Example 1 in which the electrolyte gel layer does not exist between the positive electrode and the separator and the same electrolyte solution A is used on both electrode sides has an initial DC resistance after the cycle test. As is apparent from the comparison between FIG. 6 and FIG. 7, in the IR chart of the separator surface measured after the cycle test, C = O (1700-1900 cm ⁻¹ ), C = C ^{(1550~1700cm -1), C-O} (1000~1300cm -1), a new peak was observed corresponding to ^{C-O-C (1000~1300cm -1} ) and the like. Similarly, in the battery cell of Example 2 in which the electrolyte gel layer does not exist between the positive electrode and the separator and the same electrolyte solution B is used on both electrode sides, the DC resistance after the cycle test increases by 64% of the initial value. As is clear from the comparison between FIG. 6 and FIG. 8, a new peak was observed in the IR chart after the cycle test as in Example 1. These results indicate that the separator surface contains a functional group generated by the oxidation reaction, suggesting that a side reaction (oxidation reaction) occurred on the separator surface, and a highly resistant oxide was formed. To do. The higher rate of increase in resistance in the battery of Example 2 was not only due to the deterioration of the separator, but also that the positive electrode resistance was remarkably increased by forming a film by oxidizing the organic solvent in the electrolyte B on the positive electrode surface. It is thought to be due to.
In addition, the 2C capacity at the 200th cycle decreased by 25% in Example 1 and nearly 40% in Example 2 compared to the 1st cycle. The result of Example 1 is considered to be due to the fact that the organic solvent in the electrolytic solution A was reduced and decomposed on the negative electrode surface in the fully charged battery, resulting in a large irreversible capacity. The result of Example 2 is considered to result from the oxidative decomposition of the electrolyte solution B component on the positive electrode surface.

  On the other hand, in the batteries of Examples 3 and 4 in which the electrolyte gel is arranged between the positive electrode and the separator, the capacity decrease after the cycle test is as small as 10% or less (more specifically, 8% or less), and further the direct current The rate of increase in resistance was 45% or more smaller than that of Example 2, and 10% or more smaller than Example 1 was shown. Further, as is clear from comparison between FIG. 6 and FIGS. 9 and 10, the IR chart measured after the cycle test shows only substantially the same peak as the IR chart measured on the separator surface before use, A new peak indicating that an oxidation reaction occurred on the positive electrode facing surface of the separator was not observed. These results indicate that in the batteries of Examples 3 and 4, the separator was not oxidized by the high potential of the positive electrode, and the deterioration of the battery performance was small. Furthermore, the positive electrode side electrolyte composition and the negative electrode side electrolyte composition are separated by gelling one electrolyte composition, and the organic solvent contained in one electrode side electrolyte composition is also separated from the other. By preventing the electrode surface from being decomposed, it is considered that it contributed to the increase in DC resistance and the suppression of irreversible capacity.

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

DESCRIPTION OF SYMBOLS 1 Vehicle 20 Winding electrode body 30 Positive electrode sheet 32 Positive electrode collector 34 Positive electrode active material layer 38 Positive electrode terminal 40 Negative electrode sheet 42 Negative electrode collector 44 Negative electrode active material layer 48 Negative electrode terminal 50 Separator 66 Electrolytic solution 67 Electrolyte gel 100,600 , 700 Lithium ion secondary battery 530 Positive electrode 534 Positive electrode active material layer 534A Positive electrode active material 540 Negative electrode 544 Negative electrode active material layer 544A Negative electrode active material 550 Separator 550A Separator positive electrode facing surface 550B Separator negative electrode facing surface 586 Electrolyte 587 Electrolyte gel 800 Power supply device 804 Electronic control unit (control device)

Claims (6)

A positive electrode having a positive electrode active material;
A negative electrode having a negative electrode active material;
A separator disposed between these electrodes;
A positive electrode side electrolyte composition E _C containing the non-aqueous solvent and a supporting salt,
_A negative electrode side electrolyte composition EA containing a nonaqueous solvent and a supporting salt;
With
Of the electrolyte compositions E _C and E _A , one is in the form of a solution and the other is in the form of a gel. The gel electrolyte composition is at least partially disposed between the positive electrode and the separator. And
The oxidation potential of the non-aqueous solvent contained in the positive electrode side electrolyte composition _{E C} (vs. Li / Li ^+), the rather high than the oxidation potential of the negative electrode side electrolyte composition _{E A} (relative to Li / Li ⁺⁾ or,
The 75 vol% or more of the non-aqueous solvent contained in the positive electrode side electrolyte composition E _C, of at least one consisting of a lithium ion secondary battery of fluorinated carbonate. The nonaqueous solvent contained in the positive electrode side electrolyte composition E _C, the oxidation potential (vs. Li / Li ⁺⁾ is higher than 4.3 V, the lithium ion secondary battery according to claim 1. The nonaqueous solvent contained in the positive electrode side electrolyte composition E _C has an oxidation potential (vs. Li / Li ⁺ ) higher than the potential of the positive electrode active material (vs. Li / Li ⁺ ) in the fully charged state of the battery. The lithium ion secondary battery according to claim 1 or 2. The non-aqueous 95% by volume or more of the solvent contained in the positive electrode side electrolyte composition E _C, consisting of at least one fluorinated carbonate, a lithium ion secondary according to any one of claims 1 3 battery.   The lithium ion secondary battery according to any one of claims 1 to 4, wherein the separator contains polypropylene. A lithium ion secondary battery according to any one of claims 1 to 5;
A control circuit electrically connected to the battery and defining at least an upper limit voltage value of the battery;
With
The power supply device in which the upper limit voltage value is set to 4.3 V or more.

Images