Abstract:
To form graphene to a practically even thickness on an object having an uneven surface or a complex surface, in particular, an object having a surface with a three-dimensional structure due to complex unevenness, or an object having a curved surface. The object and an electrode are immersed in a graphene oxide solution, and voltage is applied between the object and the electrode. At this time, the object serves as an anode. Graphene oxide is attracted to the anode because of being negatively charged, and deposited on the surface of the object to have a practically even thickness. A portion where graphene oxide is deposited is unlikely coated with another graphene oxide. Thus, deposited graphene oxide is reduced to graphene, whereby graphene can be formed to have a practically even thickness on an object having surface with complex unevenness.
Abstract:
A material that can be used in a wide temperature range and a manufacturing method thereof are provided. A graphene compound has a substituted or unsubstituted chain group. The chain group has one or more ester groups or carboxyl groups and contains a Si atom. The chain group is bonded to a graphene layer through the Si atom. A method for forming a graphene compound includes a step of stirring graphene oxide and a Lewis base and a step of mixing a silicon compound having one or more ester groups or carboxyl groups into the mixed solution and stirring the obtained mixed solution. The Lewis base is butylamine, pentylamine, hexylamine, diethylamine, dipropylamine, dibutylamine, triethylamine, tripropylamine, or pyridine.
Abstract:
To improve the reliability of a power storage device. A granular active material including carbon is used, and a net-like structure is formed on part of a surface of the granular active material. In the net-like structure, a carbon atom included in the granular active material is bonded to a silicon atom or a metal atom through an oxygen atom. Formation of the net-like structure suppresses reductive decomposition of an electrolyte solution, leading to a reduction in irreversible capacity. A power storage device using the above active material has high cycle performance and high reliability.
Abstract:
A lithium-ion secondary battery with a high capacity retention rate is provided. In addition, a fabricating method of a lithium-ion secondary battery with a high capacity retention rate is provided. The lithium-ion secondary battery includes a positive electrode, a negative electrode, and an electrolyte solution. The negative electrode includes a negative electrode active material layer. The electrolyte solution includes at least one of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and lithium bis(fluorosulfonyl)amide (LiFSA). The electrolyte solution includes vinylene carbonate (VC). A coating film including lithium oxide is on a surface of the negative electrode active material layer. A fabricating method of a lithium-ion secondary battery includes a first step of enclosing a positive electrode, a negative electrode, and an electrolyte solution in an exterior body, and a second step of annealing the exterior body enclosing the positive electrode, the negative electrode, and the electrolyte solution for 24 hours or longer after the first step. The annealing in the second step is performed at a temperature higher than or equal to 80° C. and lower than or equal to 100° C.
Abstract:
A lithium-ion storage battery with a high capacity retention rate is provided. A lithium-ion storage battery with a longer lifetime is provided. A method for fabricating a lithium-ion storage battery with a high capacity retention rate is provided. A lithium-ion storage battery includes a positive electrode, a negative electrode, and an electrolyte solution. A coating film which includes lithium oxide is provided over the surface of the negative electrode. The electrolyte solution may include LiTFSA or LiFSA. The method for fabricating a lithium-ion storage battery includes a first step of enclosing a positive electrode, a negative electrode, and an electrolyte solution in an exterior body and a second step of keeping the exterior body including the positive electrode, the negative electrode, and the electrolyte solution at temperature higher than or equal to 70 degrees Celsius for longer than or equal to 24 hours after the first step.
Abstract:
To achieve a power storage unit that can be repeatedly bent without a large decrease in charge and discharge capacity. In the flexible power storage unit, the content of a binder in an active material layer containing an active material is greater than or equal to 1 wt % and less than or equal to 10 wt %, preferably greater than or equal to 2 wt % and less than or equal to 8 wt %, and more preferably greater than or equal to 3 wt % and less than or equal to 5 wt %.
Abstract:
An object is to provide an electrochemical device in which lithium deposition and reduction in battery capacity can be inhibited even when the concentration of a lithium salt in an electrolytic solution is lower than 1.0 M. Lithium deposition can be inhibited and lithium whiskers can be dissolved by applying an inversion pulse current for a short time more than once in a charging period of a secondary battery which deteriorates. By applying the inversion pulse current more than once, deterioration of a lithium-ion secondary battery due to repeated charging can be suppressed even when it is a secondary battery in which the concentration of a lithium salt in an electrolytic solution is lower than 1.0 M and therefore lithium is easily deposited.
Abstract:
An electrode for a power storage device with good cycle characteristics and high charge/discharge capacity is provided. In addition, a power storage device including the electrode is provided. The electrode for the power storage device includes a conductive layer and an active material layer provided over the conductive layer, the active material layer includes graphene and an active material including a plurality of whiskers, and the graphene is provided to be attached to a surface portion of the active material including a plurality of whiskers and to have holes in part of the active material layer. Further, in the electrode for the power storage device, the graphene is provided to be attached to a surface portion of the active material including a plurality of whiskers and to cover the active material including a plurality of whiskers. Further, the power storage device including the electrode is manufactured.
Abstract:
Provided is a layer for preventing a short circuit between a positive electrode and a negative electrode in a solid battery using a layer containing a solid electrolyte. As the solid electrolyte between the positive electrode and the negative electrode, a layer containing a graphene compound is used. Lithium ions can pass through the layer containing the graphene compound. Lithium ions are added in advance in the layer containing the graphene compound. Specifically, a modifier is used, and a graphene compound chemically modified with a functional group such as ether and ester with an increased interlayer distance is used.
Abstract:
A positive electrode active material in which the number of defects that cause deterioration is small or progress of the defect is suppressed is provided. The positive electrode active material is used for a secondary battery. The positive electrode active material contains lithium cobalt oxide containing an additive element. After a cycle test is performed on a cell that uses the positive electrode active material for a positive electrode and a lithium electrode as a counter electrode, the positive electrode active material includes a defect and contains at least the same element as the additive element in a region in the vicinity of the defect. The additive element is contained also in a surface portion of the positive electrode active material.