Presented in the present disclosure are nanocomposites and rechargeable batteries which are resistant to thermal runaway and are safe, reliable, and stable electrode materials for rechargeable batteries operated at high temperature and high pressure. The nanocomposites include a plurality of transition metal oxide nanoparticles, a plurality of ultrathin sheets of a first two-dimensional (2D) material, and a plurality of ultrathin sheets of a different 2D material, which act in synergy to provide an improved thermal stability, an increased surface area, and enhanced electrochemical properties to the nanocomposites. For example, rechargeable batteries that include the nanocomposites as an electrode material have 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.