To provide a power storage device whose charge and discharge characteristics are unlikely to be degraded by heat treatment. To provide a power storage device that is highly safe against heat treatment The power storage device includes a positive electrode, a negative electrode, a separator, an electrolytic solution, and an exterior body. The separator is located between the positive electrode and the negative electrode. The separator contains polyphenylene sulfide or solvent-spun regenerated cellulosic fiber The electrolytic solution contains a solute and two or more kinds of solvents. The solute contains LiBETA. One of the solvents is propylene carbonate.

Provided herein is a negative electrode or anode for an electrochemical cell, the anode comprising nanoscale silicon. The nanoscale silicon facilitates the formation of vertical cracks in the anode layer when the anode is cycled in an electrochemical cell, which improves cell performance as compared to a silicon anode that forms random or horizontal cracks when the anode is cycled.

To provide a power storage device whose charge and discharge characteristics are unlikely to be degraded by heat treatment. To provide a power storage device that is highly safe against heat treatment. The power storage device includes a positive electrode, a negative electrode, a separator, an electrolytic solution, and an exterior body. The separator is located between the positive electrode and the negative electrode. The separator contains polyphenylene sulfide or solvent-spun regenerated cellulosic fiber. The electrolytic solution contains a solute and two or more kinds of solvents. The solute contains LiBETA. One of the solvents is propylene carbonate.

Provided is a battery cell sheet and a secondary battery that can prevent a variation in an electrolyte composition due to volatilization and do not cause a decrease in battery performance even in a case where a component with high volatility is used. The battery cell sheet includes: an electrode that includes an electrode current collector, and electrode mixture layers respectively formed on both upper and lower surfaces of the electrode current collector; a first semi-solid electrolyte layer and a second semi-solid electrolyte layer that are respectively laminated on upper and lower surfaces of the electrode; a first sealing sheet and a second sealing sheet that respectively adhere to and cover a surface of each semi-solid electrolyte layer opposite to a surface thereof laminated with the electrode, and seal the electrode with both of the first semi-solid electrolyte layer and the second semi-solid electrolyte layer; a non-aqueous solution that is provided between each of the electrode mixture layers of the electrode and each semi-solid electrolyte layer; and a sealing portion that is provided at an end side portion of each of the first sealing sheet and the second sealing sheet.

The present invention provides a one-sided electrode for a secondary battery comprising a current collector, an electrode mixture layer applied to one surface of the current collector, and an electrode distortion-preventing layer formed on the other surface of the current collector to which no electrode mixture is applied. The one-sided electrode according to the present invention exhibits significantly reduced warping or curling after a rolling process and has the advantages of facilitating subsequent processes and enabling enhanced productivity.

A battery cell includes a first current collector and a cathode electrode arranged adjacent to the first current collector and including lithium active material. A separator is arranged adjacent to the cathode electrode. The battery cell includes a second current collector. A porous conductive layer is arranged on the second current collector between the second current collector and the separator.

To provide a power storage device whose charge and discharge characteristics are unlikely to be degraded by heat treatment. To provide a power storage device that is highly safe against heat treatment. The power storage device includes a positive electrode, a negative electrode, a separator, an electrolytic solution, and an exterior body. The separator is located between the positive electrode and the negative electrode. The separator contains polyphenylene sulfide or solvent-spun regenerated cellulosic fiber. The electrolytic solution contains a solute and two or more kinds of solvents. The solute contains LiBETA. One of the solvents is propylene carbonate.

A metal support for an electrochemical element where the metal support includes a plate face, has a plate shape as a whole, and has a warping degree of 1.5?10.sup.?2 or less determined by calculating a least square value through the least squares method using at least three points in the plate face of the metal support, calculating a first difference between the least square value and a positive-side maximum displacement value on a positive side with respect to the least square value and a second difference between the least square value and a negative-side maximum displacement value on a negative side that is opposite to the positive side with respect to the least square value, and dividing the sum of the first difference and the second difference by a maximum length of the plate face of the metal support that passes through a center of gravity.

A secondary battery of the present disclosure includes a positive electrode, an electrolyte layer, a negative electrode current collector, and metallic lithium as a negative electrode active material that is deposited between the electrolyte layer and the negative electrode current collector by charging, an intermediate layer is present between the electrolyte layer and the negative electrode current collector, and the intermediate layer contains hydrogen boride.

Provided are an aqueous composition with which the surface of stainless steel is adequately roughened in an efficient manner with few steps, a method for roughening stainless steel, etc. The problem mentioned above is solved by an aqueous composition for roughening the surface of stainless steel, the aqueous composition including 0.1-20 mass % of hydrogen peroxide with reference to the total amount of the aqueous composition, 0.25-40 mass % of copper ions with reference to the total amount of the aqueous composition, and 1-30 mass % of halide ions with reference to the total amount of the aqueous composition.