JP2017054736A - Electrolytic solution for lithium ion secondary battery, and method for manufacturing lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic solution for a lithium ion secondary battery, which, when used in a lithium ion secondary battery, a decrease in capacity can be remarkably suppressed even when a charge-and-discharge cycle is repeated.SOLUTION: An electrolytic solution for a lithium ion secondary battery comprises 0.1-20 vol.% of a halogenated disiloxane compound expressed by the formula (1) (Xand Xeach independently represent a halogen atom; Rto Reach independently represent H or a C1-9 carbon hydride group).EFFECT: A strong film including the halogenated disiloxane compound is formed on a negative electrode surface of a lithium ion secondary battery and, by virtue of an effect of the film, a decrease in capacity of the lithium ion secondary battery can be suppressed.SELECTED DRAWING: None

Description

  The present invention relates to an electrolyte solution for a lithium ion secondary battery. The present invention also relates to a method for producing a lithium ion secondary battery using the electrolyte for the lithium ion secondary battery.

  Lithium ion secondary batteries are lighter and have a higher energy density than existing batteries, and have recently been used as so-called portable power sources for vehicles and personal computers and power sources for driving vehicles. Lithium-ion secondary batteries are expected to become increasingly popular as high-output power sources for driving vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV). Yes.

  In order to improve the cycle life of the lithium ion secondary battery, the lithium ion secondary battery is initially charged to form a passive film called a SEI (Solid Electrolyte Interface) film on the negative electrode surface. Yes. The SEI film is generated by reductive decomposition of the electrolyte during initial charging. The SEI film suppresses the decomposition of the electrolytic solution when the lithium ion secondary battery is used, and enables smooth insertion and removal of lithium ions.

  The capacity of a lithium ion secondary battery tends to decrease as charging and discharging are repeated. It is known that the capacity of a lithium ion secondary battery correlates with the amount of movable lithium ions. One of the causes of the decrease in the capacity of the lithium ion secondary battery is that lithium ions are taken into the SEI film formed on the negative electrode surface. On the other hand, Patent Document 1 describes that the cycle characteristics and the like of a lithium ion secondary battery are improved by producing a lithium ion secondary battery using an electrolytic solution containing cyclic siloxane. In Patent Document 1, the cycle characteristics and the like of the lithium ion secondary battery are improved because the cyclic siloxane reacts with the electrode surface or SEI film or is coordinated with the electrode surface or SEI film to insert and desorb lithium ions. It is presumed that the ease of handling is improved.

JP 2004-071458 A

  However, as a result of intensive studies by the present inventors, in a lithium ion secondary battery produced using an electrolytic solution containing cyclic siloxane as described in Patent Document 1, a decrease in capacity is sufficiently suppressed. Found no.

  This invention is made | formed in view of the said situation, The objective is providing the electrolyte solution for lithium ion secondary batteries by which the fall of a capacity | capacitance is suppressed notably when it uses for a lithium ion secondary battery. It is in.

  The electrolyte solution for lithium ion secondary batteries disclosed herein contains a halogenated disiloxane compound represented by the following formula (1) in an amount of 0.1% by volume to 20% by volume.

In the formula, X ₁ and X ₂ each independently represent a halogen atom, and R _{1 to} R ₄ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 9 carbon atoms.
When a lithium ion secondary battery is constructed using the electrolyte for a lithium ion secondary battery having such a configuration, a strong coating containing the halogenated disiloxane compound is formed on the negative electrode surface of the lithium ion secondary battery. The reduction of the capacity of the lithium ion secondary battery is remarkably suppressed by the action of the coating formed.

In one preferred embodiment of the lithium ion secondary battery electrolyte solution as disclosed herein, in the formula _(1), R 1 ~R ₄ are each independently a hydrocarbon group having 1 to 4 carbon atoms .
According to such a configuration, the viscosity of the electrolytic solution can be reduced, and the low temperature resistance of the lithium ion secondary battery can be reduced.

In one preferred embodiment of the lithium ion secondary battery electrolyte solution as disclosed herein, in the formula (1), the X ₁ and X _2, a chlorine atom.
According to such a structure, the suppression effect of the capacity | capacitance fall of a lithium ion secondary battery is higher.

The method of manufacturing a lithium ion secondary battery disclosed herein includes a step of manufacturing a lithium ion secondary battery assembly in which an electrode body and the above electrolyte solution for a lithium ion secondary battery are housed in a battery case. Initial charging the lithium ion secondary battery assembly.
According to such a configuration, a lithium ion secondary battery in which a decrease in capacity is remarkably suppressed is provided.

It is sectional drawing which shows typically the internal structure of the lithium ion secondary battery manufactured using the electrolyte solution for lithium ion secondary batteries which concerns on one Embodiment of this invention. It is a schematic diagram which shows the structure of the winding electrode body of the lithium ion secondary battery manufactured using the electrolyte solution for lithium ion secondary batteries which concerns on one Embodiment of this invention. (A) is the schematic diagram of the negative electrode surface of the lithium ion secondary battery of a prior art, (b) is lithium manufactured using the electrolyte solution for lithium ion secondary batteries which concerns on one Embodiment of this invention. It is a schematic diagram of the negative electrode surface of an ion secondary battery. It is a graph which shows the relationship between content of the halogenated disiloxane compound in electrolyte solution, and a capacity | capacitance maintenance factor about the examined coin cell.

  Embodiments according to the present invention will be described below with reference to the drawings. It should be noted that matters other than those specifically mentioned in the present specification and necessary for the implementation of the present invention (for example, electrolytes for lithium ion secondary batteries and lithium ion secondary batteries that do not characterize the present invention) The general configuration and manufacturing process) can be understood as a design matter of a person skilled in the art based on the prior art in the field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Moreover, in the following drawings, the same code | symbol is attached | subjected and demonstrated to the member and site | part which show | plays the same effect | action. In addition, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships.

  In the present specification, the “secondary battery” refers to a general power storage device that can be repeatedly charged and discharged, and is a term including a so-called storage battery such as a lithium ion secondary battery and a power storage element such as an electric double layer capacitor. Further, in the present specification, the “lithium ion secondary battery” refers to a secondary battery that uses lithium ions as a charge carrier and is charged / discharged by movement of charges accompanying the lithium ions between the positive and negative electrodes.

  The electrolytic solution for a lithium ion secondary battery according to this embodiment contains a halogenated disiloxane compound represented by the following formula (1) in an amount of 0.1% by volume to 20% by volume.

In the above formula (1), X ₁ and X ₂ each independently represent a halogen atom, and R _{1 to} R ₄ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 9 carbon atoms. .

Examples of the halogen atom represented by X ₁ and X ₂ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among them, a chlorine atom is preferable because the effect of suppressing the decrease in capacity of the lithium ion secondary battery is higher.

The hydrocarbon group having 1 to 9 carbon atoms represented by R _{1 to} R ₄ may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. Examples thereof include alkyl groups having 1 to 9 carbon atoms, alkenyl groups having 2 to 9 carbon atoms, alkynyl groups having 2 to 9 carbon atoms, phenyl groups, alkylphenyl groups having 7 to 9 carbon atoms, and 7 to 9 carbon atoms. And a phenylalkyl group having 8 to 9 carbon atoms.

The alkyl group having 1 to 9 carbon atoms may be linear, branched or cyclic, and examples thereof include methyl group, ethyl group, n-propyl group, i-propyl group, n- Examples thereof include a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, and a nonyl group.
The alkenyl group having 2 to 9 carbon atoms may be linear, branched or cyclic, and examples thereof include vinyl group, allyl group, 1-propenyl group, butenyl group, pentenyl group and hexenyl. Group, cyclohexenyl group, heptenyl group, octenyl group, nonenyl group and the like.
The alkynyl group having 2 to 9 carbon atoms may be linear, branched or cyclic, and examples thereof include ethynyl group, propynyl group, butynyl group, pentynyl group, hexynyl group, heptynyl group, An octynyl group, a noninyl group, etc. are mentioned.
Examples of the alkylphenyl group having 7 to 9 carbon atoms include a methylphenyl group, an ethylphenyl group, and a dimethylphenyl group.
Examples of the phenylalkyl group having 7 to 9 carbon atoms include a benzyl group.
Examples of the alkylphenylalkyl group having 8 to 9 carbon atoms include a methylbenzyl group.

R _{1 to} R ₄ are preferably a hydrocarbon group having 1 to 9 carbon atoms, and are preferably an alkyl group having 1 to 9 carbon atoms and a carbon number, because the capacity reduction effect of the lithium ion secondary battery is higher. More preferably, it is a 2-9 alkenyl group or a phenyl group.

On the other hand, R _{1 to} R ₄ are preferably hydrocarbon groups having 1 to 4 carbon atoms because the viscosity of the electrolytic solution can be reduced and the low temperature resistance of the lithium ion secondary battery can be reduced.

  Content of the said halogenated disiloxane compound in the electrolyte solution for lithium ion secondary batteries which concerns on this embodiment is 0.1 volume% or more and 20 volume% or less. When the content of the halogenated disiloxane compound is within this range, a reduction in the capacity of the lithium ion secondary battery can be remarkably suppressed.

The electrolytic solution for a lithium ion secondary battery according to the present embodiment usually contains a nonaqueous solvent and a supporting salt (electrolyte salt) as components other than the halogenated disiloxane compound.
As the non-aqueous solvent, those conventionally used for lithium ion secondary batteries can be used, and examples thereof include carbonates, ethers, esters, nitriles, sulfones, lactones and the like. It is done. Of these, carbonates are preferred. The carbonates may be linear or cyclic. Examples thereof include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and the like. Is mentioned. These can be used alone or in combination of two or more.

As the supporting salt, those conventionally used in lithium ion secondary batteries can be used, and examples thereof include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , and LiC ₄ F _9. Examples of the lithium salt include SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , and LiI. These can be used alone or in combination of two or more. Supporting salt is preferably a LiPF _6.
The concentration of the supporting salt in the electrolytic solution is, for example, from 0.1 mol / L to 5 mol / L, and preferably from 0.7 mol / L to 1.3 mol / L.

  The electrolyte solution for a lithium ion secondary battery according to the present embodiment is a film forming agent, an overcharge additive, a surfactant, a dispersant, in addition to the above components, for the purpose of further improving the characteristics of the lithium ion secondary battery. And additives such as thickeners may be included.

  By producing a lithium ion secondary battery using the electrolytic solution for a lithium ion secondary battery according to this embodiment, a lithium ion secondary battery in which a decrease in capacity is remarkably suppressed can be obtained.

  A preferred method for manufacturing a lithium ion secondary battery includes a step of producing a lithium ion secondary battery assembly in which the electrode body and the electrolyte for a lithium ion secondary battery according to the above-described embodiment are accommodated in a battery case (lithium An ion secondary battery assembly manufacturing step) and a step of initially charging the manufactured lithium ion secondary battery assembly (initial charging step).

  Hereinafter, as a specific example of the manufacturing method, a method for manufacturing a flat rectangular lithium ion secondary battery including a wound electrode body will be described in detail with reference to the drawings. However, the lithium ion secondary battery manufactured by the manufacturing method is not limited to a flat rectangular lithium ion secondary battery, and may be a cylindrical lithium ion secondary battery, a coin type lithium ion secondary battery, or the like. Good. The electrode body of the lithium ion secondary battery is not limited to the wound electrode body, and may be a laminated electrode body.

  FIG. 1 is a cross-sectional view schematically showing the internal structure of a lithium ion secondary battery 100 manufactured by the manufacturing method. FIG. 2 is a schematic diagram showing a configuration of the wound electrode body 20 of the lithium ion secondary battery 100 manufactured by the manufacturing method.

  First, the lithium ion secondary battery assembly manufacturing process will be described. First, the wound electrode body 20 is prepared. In the wound electrode body 20, for example, as shown in FIGS. 1 and 2, a positive electrode active material layer 54 is formed along the longitudinal direction on one side or both sides (here, both sides) of an elongated positive electrode current collector 52. The positive electrode sheet 50 and the negative electrode sheet 60 in which the negative electrode active material layer 64 is formed along the longitudinal direction on one side or both sides (here, both sides) of the long negative electrode current collector 62 are two long sheets. It has a form of being rolled up in the longitudinal direction by being overlapped via a scale-like separator sheet 70. The positive electrode sheet 50 has a positive electrode active material non-formation portion 52a where the positive electrode active material layer 54 is not provided and the positive electrode current collector 52 is exposed at one end along the longitudinal direction. The negative electrode sheet 60 has a negative electrode active material non-formation portion 62a in which the negative electrode active material layer 64 is not provided and the negative electrode current collector 62 is exposed at one end along the longitudinal direction. A positive electrode active material non-formation portion 52a and a negative electrode active material layer non-formation portion 62a are located at both ends of the winding electrode body 20 in the winding axis direction (referred to as a width direction orthogonal to the longitudinal direction). ing. Such a wound electrode body 20 can be produced according to a conventional method. Specifically, the positive electrode sheet 50 and the negative electrode sheet 60 are first produced. Moreover, the separator 70 is prepared.

  The positive electrode sheet 50 is prepared by mixing a positive electrode active material, a conductive material, a binder, and the like in a suitable solvent (for example, N-methyl-2-pyrrolidone) to prepare a positive electrode paste (including positive electrode slurry and positive electrode ink). In addition, the positive electrode paste can be produced by applying the positive electrode paste onto one or both surfaces of the positive electrode current collector 52 and then drying it. After drying, the positive electrode sheet 50 may be appropriately pressed.

Examples of the positive electrode current collector 52 constituting the positive electrode sheet 50 include aluminum foil. Examples of the positive electrode active material included in the positive electrode active material layer 54 include lithium transition metal oxides (eg, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNiO ₂ , LiCoO ₂ , LiFeO ₂ , LiMn ₂ O). ₄ , LiNi _0.5 Mn _1.5 O ₄ etc.), lithium transition metal phosphate compounds (eg, LiFePO ₄ etc.) and the like. As the conductive material, for example, carbon black such as acetylene black (AB) and other (eg, graphite) carbon materials can be suitably used. As the binder, for example, polyvinylidene fluoride (PVDF) can be used.

  The negative electrode sheet 60 is prepared by mixing a negative electrode active material, a binder, a thickener and the like in an appropriate solvent (for example, water) to prepare a negative electrode paste (including negative electrode slurry and negative electrode ink). The negative electrode current collector 62 can be produced by applying it on one or both sides and then drying. After drying, the negative electrode sheet 60 may be appropriately pressed.

  Examples of the negative electrode current collector 62 constituting the negative electrode sheet 60 include copper foil. As the negative electrode active material contained in the negative electrode active material layer 64, for example, a carbon material such as graphite, hard carbon, or soft carbon can be used. As the binder, for example, styrene butadiene rubber (SBR) can be used. As the thickener, for example, carboxymethyl cellulose (CMC) can be used.

  Examples of the separator 70 include a porous sheet (film) formed using a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Such a porous sheet may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). A heat resistant layer (HRL) may be provided on the surface of the separator 70.

  The obtained positive electrode sheet 50 and negative electrode sheet 60 are superposed through two separators 70 to produce a laminate. At this time, the positive electrode sheet 50 and the negative electrode sheet 60 are shifted and overlapped so that the positive electrode active material non-formation part 52a and the negative electrode active material layer non-formation part 62a are exposed at both ends in the width direction of the laminate. The electrode body 20 can be obtained by winding the laminate in the longitudinal direction and crushing it from the side surface direction. In addition, the electrode body 20 may be manufactured by winding the laminated body itself so that the winding cross section has a flat shape.

  Next, the wound electrode body 20 is accommodated in the battery case 30 according to a known method. Specifically, a main body of the battery case 30 having an opening and a lid of the battery case 30 that closes the opening are prepared. The lid of the battery case 30 is provided with a thin safety valve 36 set so as to release the internal pressure when the internal pressure of the battery case 30 rises above a predetermined level. In addition, the lid of the battery case 30 is provided with an inlet (not shown) for injecting an electrolytic solution. As the material of the battery case 30, for example, a light metal material having good thermal conductivity such as aluminum is used.

  The positive terminal 42 and the positive current collector plate 42a, the negative terminal 44 and the negative current collector plate 44a are attached to the lid of the battery case 30. The positive electrode current collector plate 42a and the negative electrode current collector plate 44a are welded to the positive electrode active material non-formation part 52a and the negative electrode active material layer non-formation part 62a exposed at both ends of the wound electrode body 20, respectively. In this way, the positive electrode terminal 42 and the positive electrode sheet 50 are electrically connected via the positive electrode current collector plate 42a, and the negative electrode terminal 44 and the negative electrode sheet 60 are electrically connected via the negative electrode current collector plate 44a. The And the winding electrode body 20 is accommodated in the inside from the opening part of the battery case 30 main body, and the main body and cover body of the battery case 30 are welded.

  Subsequently, the electrolytic solution for a lithium ion secondary battery according to the above-described embodiment is injected from the injection port. After injecting the electrolytic solution, the injection port is sealed to obtain a lithium ion secondary battery assembly.

  Next, the initial charging process will be described. The initial charging step can be performed according to a known method. For example, an external power source is connected between the positive electrode terminal 42 and the negative electrode terminal 44 of the manufactured lithium ion secondary battery assembly, and initial charging (typically constant current charging) is performed to a predetermined voltage. As a result, a part of the electrolytic solution is reduced and decomposed in the negative electrode 60, and a film is formed on the surface of the negative electrode active material.

  The ultimate voltage (typically the highest ultimate voltage) between the positive electrode terminal 42 and the negative electrode terminal 44 in the initial charging is not particularly limited. For example, the SOC (State Of Charge) of the lithium ion secondary battery assembly is 65%. It can be a voltage range that can be shown when it is in the range of ~ 110% (typically 80% to 110%, for example 80% to 105%).

  The charging method is not particularly limited. For example, charging may be performed at a constant current (CC charging) until the voltage is reached, and charging is performed at a constant voltage after charging at a constant current until the voltage is reached. You may carry out by the method (CCCV charge) to do. The rate at the time of CC charging is not particularly limited, but if it is too low, the processing efficiency (working efficiency) tends to decrease. On the other hand, if it is too high, the denseness of the formed film may be insufficient, or the positive electrode active material may be deteriorated. For this reason, for example, 0.1C to 5C, preferably 0.5C to 2C.

  After the initial charging step, an aging step may be performed according to a known method in order to modify the film formed on the surface of the negative electrode active material.

In the lithium ion secondary battery 100 obtained as described above, the decrease in capacity is remarkably suppressed. The reason is presumed as follows. FIG. 3A is a schematic view of a negative electrode surface of a lithium ion secondary battery of the prior art, that is, a lithium ion secondary battery manufactured using an electrolytic solution not containing the halogenated disiloxane compound. FIG.3 (b) is a schematic diagram of the negative electrode surface of the lithium ion secondary battery manufactured using the electrolyte solution for lithium ion secondary batteries which concerns on this embodiment. In FIG. 3A, the SEI film 192 is formed on the surface of the negative electrode 160 (negative electrode active material layer 164). In the SEI film 192 as shown in FIG. 3A, lithium ions 80 are easily taken in. When the lithium ions 80 are taken into the SEI film 192, the amount of movable lithium ions decreases, and the capacity of the lithium ion secondary battery decreases. On the other hand, in FIG. 3B, the SEI film 92 is formed on the surface of the negative electrode 60 (negative electrode active material layer 64). The halogenated disiloxane compound 94 is incorporated into the SEI film 92 by coordination or reaction with the SEI film 92 or the like. For this reason, in the SEI film 92 as shown in FIG. 3B, it is difficult for lithium ions 80 to be taken in. Further, the halogenated disiloxane compound 94 has a silicon-halogen bond (Si—X ₁ bond and Si—X ₂ bond). The silicon-halogen bond has a higher polarization than the Si—R ₁ bond, the Si—R ₂ bond, the Si—R ₃ bond, and the Si—R ₄ bond. That is, δ ⁺ of the silicon atom of the silicon-halogen bond is large. Therefore, by adding the halogenated disiloxane compound having a silicon-halogen bond to the electrolytic solution, a strong film is formed on the surface of the negative electrode.
However, if the amount of the halogenated disiloxane compound taken into the SEI film is too small, the effect of preventing lithium ions from being taken into the SEI film is small. On the other hand, if the amount of the above-mentioned rogenated disiloxane compound taken into the SEI film is too large, the movement of lithium ions is hindered, and the insertion and desorption of lithium ions at the negative electrode are hindered. Therefore, the amount of the above-mentioned rogenated disiloxane compound taken into the SEI film has an appropriate range, and the content of the above-mentioned halogenated disiloxane compound in the electrolytic solution before the coating is formed is in an appropriate range. There is.
Therefore, in the lithium ion secondary battery manufactured using the electrolytic solution for a lithium ion secondary battery containing an appropriate amount of the halogenated disiloxane compound according to the present embodiment, the coating formed on the negative electrode surface is lithium ion. Is difficult to take in and does not hinder the movement of lithium ions. Further, the coating film formed on the negative electrode surface is strong (high durability). For this reason, in the lithium ion secondary battery having such a coating on the negative electrode surface, the decrease in capacity is remarkably suppressed.

  The lithium ion secondary battery 100 obtained as described above can be used for various applications. Suitable applications include driving power sources mounted on vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV). The lithium ion secondary battery 100 can also be used in the form of a battery pack typically formed by connecting a plurality of lithium ion secondary batteries 100 in series and / or in parallel.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not limited to this Example.

<Test Example 1>
[Production of coin cell]
Stainless steel is used as the working electrode, metallic lithium as the counter electrode, and these are assembled into a stainless steel container together with the separator and the electrolyte, and a coin cell (half-cell for performance evaluation) A1 to A17 having a diameter of 20 mm and a thickness of 3.2 mm (CR2032 type). Built. A porous polyolefin sheet was used as the separator. As an electrolytic solution, for cells A1 to A16, a mixed solvent of EC and EMC (EC: EMC = 3: 7 (mass ratio)) as a nonaqueous solvent, LiPF ₆ having a concentration of 1 mol / L as a supporting salt, An additive containing a compound shown in Table 1 having a concentration of 6% by volume was used. For the cell A17, a nonaqueous solvent containing a mixed solvent of EC and EMC (EC: EMC = 3: 7 (mass ratio)) and a supporting salt having a concentration of 1 mol / L LiPF ₆ was used.

[Capacity maintenance rate after 50 cycles]
50 for each cell at a temperature of 60 ° C. and a current density of 0.5 mA / cm ² and a cut voltage of −2.0 V to 1.5 V (E / V vs. (Li ⁺ / Li)). The cycle was charged and discharged. Then, the charge capacity at the first cycle (charge capacity obtained by charging Li ions into stainless steel as Li metal) was taken as 100%, and the maintenance ratio (%) of the charge capacity at the 50th cycle was determined. The results are shown in Table 1.

<Test Example 2>
[Production of coin cell]
Stainless steel is the working electrode, metallic lithium is the counter electrode, and these are assembled in a stainless steel container together with the separator and electrolyte solution. Built. A porous polyolefin sheet was used as the separator. As the electrolytic solution, the cell B1 contains a mixed solvent of EC and EMC (EC: EMC = 3: 7 (mass ratio)) as a nonaqueous solvent and LiPF ₆ having a concentration of 1 mol / L as a supporting salt. It was used. Regarding the cells B2 to B7, a mixed solvent of EC and EMC (EC: EMC = 3: 7 (mass ratio)) as a nonaqueous solvent, LiPF ₆ having a concentration of 1 mol / L as a supporting salt, and Table 2 as additives. The thing containing the halogenated disiloxane compound represented by the said Formula (1) of the density | concentration shown to was used. The halogenated disiloxane compound used in this test example is a compound in which X ₁ and X ₂ are chlorine atoms and R _{1 to} R ₄ are methyl groups in the above formula (1).

[Capacity maintenance rate after 50 cycles]
50 for each cell at a temperature of 60 ° C. and a current density of 0.5 mA / cm ² and a cut voltage of −2.0 V to 1.5 V (E / V vs. (Li ⁺ / Li)). The cycle was charged and discharged. Then, the charge capacity at the first cycle (charge capacity obtained by charging Li ions into stainless steel as Li metal) was taken as 100%, and the maintenance ratio (%) of the charge capacity at the 50th cycle was determined. The results are shown in Table 2 and FIG.

  As can be seen from Table 1, the cells A1 to A13 prepared using the electrolytic solution containing the halogenated disiloxane compound represented by the above formula (1) use an electrolytic solution containing other additives. The capacity retention rate was higher than that of the produced cells A14 to A16 and the cell A17 produced using the electrolytic solution containing no additive. This is because, during the first charge, the halogenated disiloxane compound represented by the above formula (1) formed a strong film on the surface of the negative electrode of the cell, making it difficult for lithium ions to be taken into the film. Conceivable.

  Further, as can be seen from Table 2 and FIG. 4, the cell B2 in which the content of the halogenated disiloxane compound represented by the above formula (1) in the electrolytic solution used is 0.1% by volume or more and 20% by volume or less. ~ B5 is a cell B1 in which the halogenated disiloxane compound represented by the above formula (1) was not added to the electrolytic solution, and the halogenated disiloxane compound represented by the above formula (1) in the electrolytic solution used. The capacity retention rate was higher than those of the cells B6 and B7, in which the content of A exceeded 20% by volume. This is represented by the above formula (1) contained in the coating formed on the negative electrode surface of the cell when the content of the halogenated disiloxane compound represented by the above formula (1) in the electrolytic solution is excessive. This is presumably because the amount of the halogenated disiloxane compound is too large, preventing the insertion and desorption of lithium ions at the negative electrode.

  From the above consideration, the capacity retention improvement effect obtained by adding an appropriate amount of the halogenated disiloxane compound represented by the above formula (1) to the electrolytic solution in these cells is A lithium ion secondary battery having a configuration (for example, a lithium ion secondary battery including a positive electrode including a lithium transition metal oxide as a positive electrode active material and a negative electrode including a carbon material as a negative electrode active material) can be similarly exhibited. Is understood.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

20 wound electrode body 30 battery case 36 safety valve 42 positive electrode terminal 42a positive electrode current collector plate 44 negative electrode terminal 44a negative electrode current collector plate 50 positive electrode sheet (positive electrode)
52 Positive Electrode Current Collector 52a Positive Electrode Active Material Layer Non-Forming Portion 54 Positive Electrode Active Material Layer 60 Negative Electrode Sheet (Negative Electrode)
62 Negative electrode current collector 62a Negative electrode active material layer non-formed portion 64 Negative electrode active material layer 70 Separator sheet (separator)
100 Lithium ion secondary battery

Claims (4)

The electrolyte solution for lithium ion secondary batteries which contains the halogenated disiloxane compound represented by following formula (1) 0.1 volume% or more and 20 volume% or less.

(In the formula, X ₁ and X ₂ each independently represent a halogen atom, and R _{1 to} R ₄ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 9 carbon atoms.) 2. The electrolyte solution for a lithium ion secondary battery according to claim 1, wherein in the formula (1), R _{1 to} R ₄ are each independently a hydrocarbon group having 1 to 4 carbon atoms. In the formula (1), X ₁ and X ₂ is a chlorine atom, according to claim 1 or 2 for a lithium ion secondary battery electrolyte according to. Producing a lithium ion secondary battery assembly in which the electrode body and the electrolyte for a lithium ion secondary battery according to any one of claims 1 to 3 are housed in a battery case;
A method for producing a lithium ion secondary battery, comprising: initial charging the produced lithium ion secondary battery assembly.

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