In a capacitor using a capacitor element having an anode foil and a cathode foil wound with a separator interposed between the anode foil and the cathode foil, the separator includes a low insulation part having a low insulation function between the anode foil and the cathode foil, and the low insulation part may be included within a range of 90% in a central portion in a height direction of the capacitor element and within a range of 5 to 90% in a diametrical direction from the center of the capacitor element.

There is provided a method for producing a separator for an electricity storage device that includes a step of contacting a porous body formed from a silane-modified polyolefin-containing molded sheet with a base solution or acid solution, and a separator for an electricity storage device comprising a microporous film with a melted film rupture temperature of 180° C. to 220° C. as measured by thermomechanical analysis (TMA).

Electrolytes and electrolyte additives for energy storage devices comprising a sulfonate ester compound are disclosed. The energy storage device comprises a first electrode and a second electrode, wherein at least one of the first electrode and the second electrode is a Si-based electrode, a separator between the first electrode and the second electrode, an electrolyte, and at least one electrolyte additive selected from a sulfonate ester compound.

Electrolytes and electrolyte additives for energy storage devices comprising a sulfonate ester compound are disclosed. The energy storage device comprises a first electrode and a second electrode, wherein at least one of the first electrode and the second electrode is a Si-based electrode, a separator between the first electrode and the second electrode, an electrolyte, and at least one electrolyte additive selected from a sulfonate ester compound.

Disclosed is a hybrid electrochemical cell with a first conductor having at least one portion that is both a first capacitor electrode and a first battery electrode. The hybrid electrochemical cell further includes a second conductor having at least one portion that is a second capacitor electrode and at least one other portion that is a second battery electrode. An electrolyte is in contact with both the first conductor and the second conductor. In some embodiments, the hybrid electrochemical cell further includes a separator between the first conductor and the second conductor to prevent physical contact between the first conductor and the second conductor, while facilitating ion transport between the first conductor and the second conductor.

Disclosed is a hybrid electrochemical cell with a first conductor having at least one portion that is both a first capacitor electrode and a first battery electrode. The hybrid electrochemical cell further includes a second conductor having at least one portion that is a second capacitor electrode and at least one other portion that is a second battery electrode. An electrolyte is in contact with both the first conductor and the second conductor. In some embodiments, the hybrid electrochemical cell further includes a separator between the first conductor and the second conductor to prevent physical contact between the first conductor and the second conductor, while facilitating ion transport between the first conductor and the second conductor.

Electrodes are formed with a porous layer of particulate electrode material bonded to each of the two major sides of a compatible metal current collector. In one embodiment, opposing electrodes are formed with like lithium-ion battery anode materials or like cathode materials or capacitor materials on both sides of the current collector. In another embodiment, a battery electrode material is applied to one side of a current collector and capacitor material is applied to the other side. In general, the electrodes are formed by combining a suitable grouping of capacitor layers with un-equal numbers of anode and cathode battery layers. One or more pairs of opposing electrodes are assembled to provide a combination of battery and capacitor energy and power properties in a hybrid electrochemical cell. The cells may be formed by stacking or winding rolls of the opposing electrodes with interposed separators.

Electrolytes and electrolyte additives for energy storage devices comprising functional thiophene compounds are disclosed. The energy storage device comprises a first electrode and a second electrode, wherein at least one of the first electrode and the second electrode is a Si-based electrode, a separator between the first electrode and the second electrode, an electrolyte, and at least one electrolyte additive selected from a thiophene compound.

Electrolytes and electrolyte additives for energy storage devices comprising functional thiophene compounds are disclosed. The energy storage device comprises a first electrode and a second electrode, wherein at least one of the first electrode and the second electrode is a Si-based electrode, a separator between the first electrode and the second electrode, an electrolyte, and at least one electrolyte additive selected from a thiophene compound.

An energy storage device according to one aspect of the present invention includes: a negative electrode including a negative electrode substrate and a negative active material layer layered directly or indirectly on a surface of the negative electrode substrate; and a positive electrode. The negative active material layer contains a negative active material. The negative active material contains non-graphitizable carbon. In one direction of the negative electrode substrate, at least one end edge side of the negative active material layer is thicker than a central portion present between the one end edge side and the other end edge side facing the one end edge side. When a true density of the non-graphitizable carbon is A [g/cm.sup.3], an amount of charge B [mAh/g] of the negative electrode in a fully charged state satisfies the following formula 1.

[1]$-173\text{XA+1588}\le \text{B}\le \text{-830A+1800}$