Occlusion and release of lithium ion are likely to one-dimensionally occur in the b-axis direction of a crystal in a lithium-containing composite oxide having an olivine structure. Thus, a positive electrode in which the b-axes of lithium-containing composite oxide single crystals are oriented vertically to a surface of a positive electrode current collector is provided. The lithium-containing composite oxide particles are mixed with graphene oxide and then pressure is applied thereto, whereby the rectangular parallelepiped or substantially rectangular parallelepiped particles are likely to slip. In addition, in the case where the rectangular parallelepiped or substantially rectangular parallelepiped particles whose length in the b-axis direction is shorter than those in the a-axis direction and the c-axis direction are used, when pressure is applied in one direction, the b-axes can be oriented in the one direction.

Occlusion and release of lithium ion are likely to one-dimensionally occur in the b-axis direction of a crystal in a lithium-containing composite oxide having an olivine structure. Thus, a positive electrode in which the b-axes of lithium-containing composite oxide single crystals are oriented vertically to a surface of a positive electrode current collector is provided. The lithium-containing composite oxide particles are mixed with graphene oxide and then pressure is applied thereto, whereby the rectangular parallelepiped or substantially rectangular parallelepiped particles are likely to slip. In addition, in the case where the rectangular parallelepiped or substantially rectangular parallelepiped particles whose length in the b-axis direction is shorter than those in the a-axis direction and the c-axis direction are used, when pressure is applied in one direction, the b-axes can be oriented in the one direction.

A method of synthesizing rubidium uranium fluoride crystals. The method includes combining uranium-based feedstock with a mineralizer solution that includes a rubidium fluoride. The feedstock and mineralizer solution are pressurized and a thermal gradient applied thereto such that a first portion of the feedstock and the mineralizer solution is heated to a temperature that is greater than a temperature of a second portion of the feedstock and the mineralizer solution. Uranium nutrient enters the mineralizer solution from the feedstock in the first portion and uranium nutrient precipitates to spontaneously form crystals in the second portion.

A method of synthesizing rubidium uranium fluoride crystals. The method includes combining uranium-based feedstock with a mineralizer solution that includes a rubidium fluoride. The feedstock and mineralizer solution are pressurized and a thermal gradient applied thereto such that a first portion of the feedstock and the mineralizer solution is heated to a temperature that is greater than a temperature of a second portion of the feedstock and the mineralizer solution. Uranium nutrient enters the mineralizer solution from the feedstock in the first portion and uranium nutrient precipitates to spontaneously form crystals in the second portion.

A method of synthesizing uranium dioxide crystals. The method of synthesizing includes combining a uranium-based feedstock with a mineralizer solution. The uranium-based feedstock is selected from uranium dioxide, uranium tetrafluoride, uranium tetrachloride, triuranium octoxide, and uranium trioxide. The feedstock and mineralizer solution are pressurized, and then a thermal gradient is applied thereto such that a first portion of the feedstock and the mineralizer solution is heated to a temperature that is greater than a temperature of a second portion of the feedstock and the mineralizer solution. The uranium nutrient enters the mineralizer solution from the feedstock in the first portion and uranium nutrient precipitates to spontaneously form crystals in the second portion.

A method of synthesizing uranium dioxide crystals. The method of synthesizing includes combining a uranium-based feedstock with a mineralizer solution. The uranium-based feedstock is selected from uranium dioxide, uranium tetrafluoride, uranium tetrachloride, triuranium octoxide, and uranium trioxide. The feedstock and mineralizer solution are pressurized, and then a thermal gradient is applied thereto such that a first portion of the feedstock and the mineralizer solution is heated to a temperature that is greater than a temperature of a second portion of the feedstock and the mineralizer solution. The uranium nutrient enters the mineralizer solution from the feedstock in the first portion and uranium nutrient precipitates to spontaneously form crystals in the second portion.

A method of synthesizing alkali uranium fluorophosphate crystals. The method includes combining a uranium-based feedstock with a mineralizer solution. The mineralizer solution includes an alkali nutrient, a phosphate, and a fluoride. The feedstock and mineralizer solution are pressurized and a thermal gradient applied thereto such that a first portion of the feedstock and the mineralizer solution is heated to a temperature that is greater than a temperature of a second portion of the feedstock and the mineralizer solution. Uranium nutrient enters the mineralizer solution from the feedstock in the first portion and uranium nutrient precipitates to spontaneously form crystals in the second portion.

A method of synthesizing alkali uranium fluorophosphate crystals. The method includes combining a uranium-based feedstock with a mineralizer solution. The mineralizer solution includes an alkali nutrient, a phosphate, and a fluoride. The feedstock and mineralizer solution are pressurized and a thermal gradient applied thereto such that a first portion of the feedstock and the mineralizer solution is heated to a temperature that is greater than a temperature of a second portion of the feedstock and the mineralizer solution. Uranium nutrient enters the mineralizer solution from the feedstock in the first portion and uranium nutrient precipitates to spontaneously form crystals in the second portion.

Occlusion and release of lithium ion are likely to one-dimensionally occur in the b-axis direction of a crystal in a lithium-containing composite oxide having an olivine structure. Thus, a positive electrode in which the b-axes of lithium-containing composite oxide single crystals are oriented vertically to a surface of a positive electrode current collector is provided. The lithium-containing composite oxide particles are mixed with graphene oxide and then pressure is applied thereto, whereby the rectangular parallelepiped or substantially rectangular parallelepiped particles are likely to slip. In addition, in the case where the rectangular parallelepiped or substantially rectangular parallelepiped particles whose length in the b-axis direction is shorter than those in the a-axis direction and the c-axis direction are used, when pressure is applied in one direction, the b-axes can be oriented in the one direction.

Occlusion and release of lithium ion are likely to one-dimensionally occur in the b-axis direction of a crystal in a lithium-containing composite oxide having an olivine structure. Thus, a positive electrode in which the b-axes of lithium-containing composite oxide single crystals are oriented vertically to a surface of a positive electrode current collector is provided. The lithium-containing composite oxide particles are mixed with graphene oxide and then pressure is applied thereto, whereby the rectangular parallelepiped or substantially rectangular parallelepiped particles are likely to slip. In addition, in the case where the rectangular parallelepiped or substantially rectangular parallelepiped particles whose length in the b-axis direction is shorter than those in the a-axis direction and the c-axis direction are used, when pressure is applied in one direction, the b-axes can be oriented in the one direction.