A composite electrode is provided having a collector, the collector is coated with an electrode composition containing an active electrode material, a binding agent, and a conductivity additive such as conductive carbon black. The electrode composition has a concentration gradient along the direction of the electrode thickness in respect of the active electrode material and the conductivity additive, with the concentration gradient of the active electrode material increasing toward the collector, and the concentration gradient of the conductivity additive and the binder decreasing toward the collector. Two different methods of producing the composite electrode are also provided. A lithium-ion battery is further provided which includes a composite electrode having a collector, the collector is coated with an electrode composition containing an active electrode material, a binding agent, and a conductivity additive.

Irreversible capacity which causes a decrease in the charge and discharge capacity of a power storage device is reduced, and electrochemical decomposition of an electrolyte solution and the like on a surface of an electrode is inhibited. Further, the cycle characteristics of the power storage device is improved by reducing or inhibiting a decomposition reaction of the electrolyte solution and the like occurring as a side reaction in repeated charging and discharging of the power storage device. A power storage device electrode includes a current collector and an active material layer that is over the current collector and includes a binder and an active material. A coating film is provided on at least part of a surface of the active material. The coating film is spongy.

Irreversible capacity which causes a decrease in the charge and discharge capacity of a power storage device is reduced, and electrochemical decomposition of an electrolyte solution and the like on a surface of an electrode is inhibited. Further, the cycle characteristics of the power storage device is improved by reducing or inhibiting a decomposition reaction of the electrolyte solution and the like occurring as a side reaction in repeated charging and discharging of the power storage device. A power storage device electrode includes a current collector and an active material layer that is over the current collector and includes a binder and an active material. A coating film is provided on at least part of a surface of the active material. The coating film is spongy.

A power storage module comprises: an electrode stacked body including a stacked body in which a plurality of bipolar electrodes are stacked, a pair of terminal electrodes located on an outer side of the stacked body in a stacking direction of the bipolar electrodes, and a plurality of metal plates which constitute the stacked body and the pair of terminal electrodes; and a sealing body provided to surround a side surface of the electrode stacked body. The sealing body includes a plurality of first sealing portions coupled to edge portions of the plurality of metal plates, and a second sealing portion that couples the first sealing portions to each other. A thickness adjustment member that adjusts the thickness of the electrode stacked body in the stacking direction is disposed in the electrode stacked body at a position of overlapping the first sealing portions when viewed from the stacking direction.

The present invention aims to provide an electrolyte solution containing a quaternary ammonium salt as an electrolyte salt and is capable of providing an electrochemical device having a high capacitance retention and reducing generation of gas. The electrolyte solution of the present invention contains a solvent, a quaternary ammonium salt, and a nitrogen-containing unsaturated cyclic compound. The unsaturated cyclic compound is a nitrogen-containing unsaturated heterocyclic compound. The unsaturated cyclic compound excludes salts of the unsaturated cyclic compound and ionic liquids obtainable from the unsaturated cyclic compound.

The present invention aims to provide an electrolyte solution containing a quaternary ammonium salt as an electrolyte salt and is capable of providing an electrochemical device having a high capacitance retention and reducing generation of gas. The electrolyte solution of the present invention contains a solvent, a quaternary ammonium salt, and a nitrogen-containing unsaturated cyclic compound. The unsaturated cyclic compound is a nitrogen-containing unsaturated heterocyclic compound. The unsaturated cyclic compound excludes salts of the unsaturated cyclic compound and ionic liquids obtainable from the unsaturated cyclic compound.

An electricity storage device includes an electrode assembly and a load applying mechanism. The load applying mechanism applies, to the electrode assembly, a load in a direction in which the positive electrode and the negative electrode are stacked in the electrode assembly. The negative electrode includes a metal foil and an active material layer that covers at least part of the metal foil and contains a carbon-based material as an active material. The density of the carbon-based material in the active material layer is 1.2 g/cm.sup.3 or higher. The degree of orientation that is defined as a ratio (I(100)/I(002)) of an X-ray diffraction intensity I(100) of a (100) plane to a diffraction intensity I(002) of a (002) plane in the active material layer is lower than or equal to 0.3. The load applied by the load applying mechanism is greater than or equal to 0.22 MPa.

An electricity storage device includes an electrode assembly and a load applying mechanism. The load applying mechanism applies, to the electrode assembly, a load in a direction in which the positive electrode and the negative electrode are stacked in the electrode assembly. The negative electrode includes a metal foil and an active material layer that covers at least part of the metal foil and contains a carbon-based material as an active material. The density of the carbon-based material in the active material layer is 1.2 g/cm.sup.3 or higher. The degree of orientation that is defined as a ratio (I(100)/I(002)) of an X-ray diffraction intensity I(100) of a (100) plane to a diffraction intensity I(002) of a (002) plane in the active material layer is lower than or equal to 0.3. The load applied by the load applying mechanism is greater than or equal to 0.22 MPa.

Disclosed herein is a method of manufacturing a secondary battery electrode containing a positive temperature coefficient (PTC) material, the method including (a) applying first slurry including a first mixture and a solvent mixed with each other to one surface of a planar current collector to generate a PTC material after drying, (b) applying second slurry including a second mixture, including an electrode active material, and a solvent mixed with each other to the first slurry applied to the current collector, which is in a non-dried state, and (c) drying the first slurry and the second slurry applied to the current collector.

As an electrode for a power storage device, an electrode including a current collector, a first active material layer over the current collector, and a second active material layer that is over the first active material layer and includes a particle containing niobium oxide and a granular active material is used, whereby the charge-discharge cycle characteristics and rate characteristics of the power storage device can be improved. Moreover, contact between the granular active material and the particle containing niobium oxide makes the granular active material physically fixed; accordingly, deterioration due to expansion and contraction of the active material which occur along with charge and discharge of the power storage device, such as powdering of the active material or its separation from the current collector, can be suppressed.