The present application is generally directed to composites comprising a hard carbon material and an electrochemical modifier. The composite materials find utility in any number of electrical devices, for example, in lithium ion batteries. Methods for making the disclosed composite materials are also disclosed.

The present application is generally directed to composites comprising a hard carbon material and an electrochemical modifier. The composite materials find utility in any number of electrical devices, for example, in lithium ion batteries. Methods for making the disclosed composite materials are also disclosed.

Microsupercapacitors (MSCs), as well as methods of fabricating the same and methods of using the same, are provided. An MSC can include interdigitated microelectrodes having reduced graphene oxide (rGO) (e.g., vertically aligned nanosheets thereof) disposed on upper surfaces of the microelectrodes. The MSC can be fabricated by preparing a micro-current collector (MCC) comprising the interdigitated microelectrodes using photolithography and then performing a bipolar electrochemistry process on the MCC to deposit rGO on the upper surfaces of the interdigitated microelectrodes (e.g., in a single-step in situ exfoliation, reduction, and deposition).

The formation method of graphene includes the steps of forming a layer including graphene oxide over a first conductive layer; and supplying a potential at which the reduction reaction of the graphene oxide occurs to the first conductive layer in an electrolyte where the first conductive layer as a working electrode and a second conductive layer with a as a counter electrode are immersed. A manufacturing method of a power storage device including at least a positive electrode, a negative electrode, an electrolyte, and a separator includes a step of forming graphene for an active material layer of one of or both the positive electrode and the negative electrode by the formation method.

The formation method of graphene includes the steps of forming a layer including graphene oxide over a first conductive layer; and supplying a potential at which the reduction reaction of the graphene oxide occurs to the first conductive layer in an electrolyte where the first conductive layer as a working electrode and a second conductive layer with a as a counter electrode are immersed. A manufacturing method of a power storage device including at least a positive electrode, a negative electrode, an electrolyte, and a separator includes a step of forming graphene for an active material layer of one of or both the positive electrode and the negative electrode by the formation method.

A subsurface battery comprises an anodic fracture disposed within a subsurface stratum and a cathodic fracture disposed with the subsurface stratum. A first well electrode contacts the anodic fracture and a second well electrode contacts the cathodic fracture.

A subsurface battery comprises an anodic fracture disposed within a subsurface stratum and a cathodic fracture disposed with the subsurface stratum. A first well electrode contacts the anodic fracture and a second well electrode contacts the cathodic fracture.

An aspect of the present invention is an energy storage device including: a negative electrode including a pair of flat portions facing each other and a curved folding portion connecting end portions on one side of the pair of flat portions to each other; and a sheet-like positive electrode disposed between the pair of flat portions of the negative electrode, in which the negative electrode includes a negative electrode substrate and a negative active material layer stacked on a surface of the negative electrode substrate directly or indirectly in a non-pressed or low-pressure pressed state, the negative active material layer contains a negative active material, the negative active material contains solid graphite particles, and the solid graphite particle has an aspect ratio of 1 or more and 5 or less.

The power storage device comprises an electrode assembly including a positive electrode, a separator, and a negative electrode, and an electrolyte solution. The negative electrode comprises a negative electrode current collector and a negative electrode active material layer. The active material layer comprises a surplus region A not facing the positive electrode active material layer, an end region B facing a region in the positive electrode active material layer, the region extending from an end of the positive electrode active material layer toward a center of the positive electrode active material layer by a length of 5% of a length from the center to the end, and a center region C. A negative electrode potential VA and a negative electrode potential VC after the positive electrode and the negative electrode are short-circuited satisfy Formulas below: (1): VA≤2.0 V, (2): VC≤1.0 V, (3): VA/VC≥0.7.

The power storage device comprises an electrode assembly including a positive electrode, a separator, and a negative electrode, and an electrolyte solution. The negative electrode comprises a negative electrode current collector and a negative electrode active material layer. The active material layer comprises a surplus region A not facing the positive electrode active material layer, an end region B facing a region in the positive electrode active material layer, the region extending from an end of the positive electrode active material layer toward a center of the positive electrode active material layer by a length of 5% of a length from the center to the end, and a center region C. A negative electrode potential VA and a negative electrode potential VC after the positive electrode and the negative electrode are short-circuited satisfy Formulas below: (1): VA≤2.0 V, (2): VC≤1.0 V, (3): VA/VC≥0.7.