An electrolyte solution containing a solvent. The solvent contains a compound (1) represented by the following formula (1), wherein R.sup.a, R.sup.b, R.sup.c, and R.sup.d are the same as or different from each other, and are each —H, —F, —CH.sub.3, or —CF.sub.3; at least one of R.sup.a, R.sup.b, R.sup.c, or R.sup.d is —F or —CF.sub.3; and at least one of R.sup.a, R.sup.b, R.sup.c, or R.sup.d is —CH.sub.3, and a compound (2) represented by the following formula (2), wherein R.sup.e is a C1-C5 linear or branched alkyl or alkoxy group optionally containing an ether bond; R.sup.f is a C1-C5 linear or branched alkyl group optionally containing an ether bond; and at least one of R.sup.e or R.sup.f contains a fluorine atom. Also disclosed is an electrochemical device including the electrolyte solution, a lithium-ion secondary battery including the electrolyte solution and a module including the electrochemical device. ##STR00001##

An electrolyte solution capable of constituting a secondary battery in which a volume change due to charge and discharge is small and cycle characteristics are excellent is provided. The present example embodiment relates to an electrolyte solution for a lithium ion secondary battery comprising a fluorinated ether and a cyclic dicarboxylic acid ester.

An electrolyte for a lithium secondary battery, and a lithium secondary battery including the same are disclosed herein. In some embodiments, an electrolyte includes a lithium salt having a concentration of 1.6 M to 5 M, an oligomer including a unit represented by Formula A, and an organic solvent including a cyclic carbonate-based compound and an acetate-based compound, wherein the cyclic carbonate-based compound is present in an amount of 6 vol % to 19 vol % based on the total volume of the organic solvent.

Electrolytes are described that involve lithium salt blends and compatible nonaqueous solvents that provide to high rate performance, charging and discharging, of lithium ion cells using silicon-based active materials, such as silicon suboxide composites, for example, silicon oxide/silicon/carbon composites. The lithium salts generally were a blend of LiPF.sub.6, and LiFSI or LiTFSI. The solvents generally comprised fluoroethylene carbonate and dimethyl carbonate with optional cosolvents and/or other additives.

Provided is a lithium metal secondary battery, including: a positive electrode; a negative electrode; and an electrolyte composition between the positive and negative electrodes, the positive electrode including: a positive electrode current collector; and a positive electrode material mixture layer including a lithium composite oxide, the negative electrode including a negative electrode current collector, the electrolyte composition including dimethyl carbonate and lithium bis(fluorosulfonyl)imide, in which the molar ratio of dimethyl carbonate to lithium bis(fluorosulfonyl)imide is 1.0 or more and 3.0 or less.

The disclosed technology relates to a busbar and thermal cut-off device (TCO) sub-assembly. The sub-assembly may be configured to be connected to a first battery cell and a second battery cell. The sub-assembly may comprise a first busbar configured to electrically connect the first battery cell to the second battery cell when the sub-assembly is connected to the first battery cell and the second battery cell. The sub-assembly may comprise a first TCO connected directly to the first busbar. The sub-assembly may not extend above a top surface of the first battery cell when the sub-assembly is connected to the first battery cell.

A nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and a lithium ion conductive nonaqueous electrolyte, wherein the negative electrode contains graphite, an open circuit potential of the negative electrode in a fully charged state is 70 mV or less relative to lithium metal, the nonaqueous electrolyte contains a solvent, a cation, and an anion, the solvent contains a fluorine-containing cyclic carbonic acid ester, the cation includes lithium ions, and the anion includes an oxalate complex anion.

The invention provides an electrolyte solution capable of providing an electrochemical device having low resistance and excellent high-temperature storage characteristics and cycle characteristics. The electrolyte solution contains lithium fluorosulfonate and a solvent containing a compound (1) represented by the following formula (1): CF.sub.2HCOOCH.sub.3.

A purpose of the present invention is to provide a lithium ion secondary battery which has further improved life characteristics. The lithium ion secondary battery of the present invention is characterized by comprising a positive electrode comprising a positive electrode active material that operates at 4.5 V or more with respect to lithium, and an electrolyte solution comprising an electrolyte solvent comprising a fluorinated ether, a cyclic sulfonic acid ester and LiN(FSO.sub.2).sub.2.

A battery includes a positive electrode containing sulfur, a negative electrode containing a material for occluding and releasing a lithium ion, and an electrolytic solution. The electrolytic solution contains at least one of a liquid complex and a liquid salt in which a polysulfide is insoluble or almost insoluble, and a solvent in which a polysulfide is soluble. The electrolytic solution has a Li.sub.2S.sub.8 saturation sulfur concentration of 10 mM or more and 400 mM or less.