Provided is a positive electrode active material particle including a core that includes lithium cobalt oxide represented by the following Chemical Formula 1; and a shell that is located on the surface of the core and includes lithium cobalt phosphate represented by the following Chemical Formula 2, wherein the shell has a tetrahedral phase:
Li.sub.aCo.sub.(1-x)M.sub.xO.sub.2-yA.sub.y(1) wherein M is at least one of Ti, Mg, Zn, Si, Al, Zr, V, Mn, Nb, or Ni, A is oxygen-substitutional halogen, and 0.95a1.05, 0x0.2, 0y0.2, and 0x+y0.2,
Li.sub.bCoPO.sub.4(2) wherein 0b1.

Provided is a positive electrode active material particle including a core that includes lithium cobalt oxide represented by the following Chemical Formula 1; and a shell that is located on the surface of the core and includes lithium cobalt phosphate represented by the following Chemical Formula 2, wherein the shell has a tetrahedral phase:
Li.sub.aCo.sub.(1-x)M.sub.xO.sub.2-yA.sub.y(1) wherein M is at least one of Ti, Mg, Zn, Si, Al, Zr, V, Mn, Nb, or Ni, A is oxygen-substitutional halogen, and 0.95a1.05, 0x0.2, 0y0.2, and 0x+y0.2,
Li.sub.bCoPO.sub.4(2) wherein 0b1.

A negative electrode active material for a non-aqueous electrolyte secondary battery, containing a negative electrode active material particle, wherein the negative electrode active material particle includes a silicon compound particle containing a silicon compound (SiO.sub.x: 0.5x1.6), the silicon compound particle contains a Li compound, at least a part of the silicon compound particle is coated with a carbon material, and an O-component fragment and a CH-component fragment are detected from the negative electrode active material particle in a measurement by TOF-SIMS, and a ratio of a peak intensity A of the O-component fragment to a peak intensity B of the CH-component fragment is 0.5A/B100. This provides a negative electrode active material for a non-aqueous electrolyte secondary battery capable of increasing battery capacity and improving the cycle characteristics and battery initial efficiency.

The present invention is directed to solid-state composite cathodes that comprise Na.sub.2S or Li.sub.2S, Na.sub.3PS.sub.4, or Li3PS4, and mesoporous carbon. The present invention is also directed to methods of making the solid-state composite cathodes and methods of using the solid-state composite cathodes in batteries and other electrochemical technologies.

Provided is an undercoat layer-forming composition which is for an energy storage device and is characterized by including a conductive carbon material, a dispersant, and a solvent, and having an expected conductivity of 50 S/cm or less when the density of the conductive carbon material is 1 g/cm.sup.3.

An electrode for an electrochemical energy accumulator includes a catalyst layer, where the catalyst layer includes an electrically conductive matrix and a chemically active material which is intercalated into the electrically conductive matrix. A protective coating is disposed on the catalyst layer, where the protective coating includes at least one metal oxide and methionine.

An electrode for an electrochemical energy accumulator includes a catalyst layer, where the catalyst layer includes an electrically conductive matrix and a chemically active material which is intercalated into the electrically conductive matrix. A protective coating is disposed on the catalyst layer, where the protective coating includes at least one metal oxide and methionine.

Presented here are nanocomposites and rechargeable batteries. In certain embodiments, nanocomposites a nanocomposite is resistant to thermal runaway, and useful as an electrode material in rechargeable batteries that are safe, reliable, and stable when operated at high temperature and high pressure. The present disclosure also provides methods of preparing rechargeable batteries. For example, rechargeable batteries that include nanocomposites of the present disclosure as an electrode material have, in some embodiments, an enhanced performance and stability over a broad temperature range from room temperature to high temperatures. These batteries fill an important need by providing a safe and reliable power source for devices operated at high temperatures and pressures such as downhole equipment used in the oil industry.

Presented here are nanocomposites and rechargeable batteries. In certain embodiments, nanocomposites a nanocomposite is resistant to thermal runaway, and useful as an electrode material in rechargeable batteries that are safe, reliable, and stable when operated at high temperature and high pressure. The present disclosure also provides methods of preparing rechargeable batteries. For example, rechargeable batteries that include nanocomposites of the present disclosure as an electrode material have, in some embodiments, an enhanced performance and stability over a broad temperature range from room temperature to high temperatures. These batteries fill an important need by providing a safe and reliable power source for devices operated at high temperatures and pressures such as downhole equipment used in the oil industry.

Presented here are nanocomposites and electrochemical storage systems (e.g., rechargeable batteries and supercapacitors), which are resistant to thermal runaway and are safe, reliable, and stable electrode materials for electrochemical storage systems (e.g., rechargeable batteries and supercapacitors) operated at high temperature and high pressure, and methods of making the same.