Abstract: Techniques for providing phase change electrolytes that can be used to improve safety of electrochemical devices, such as lithium batteries, are disclosed herein. At normal operation temperature, the phase change electrolyte is capable of switching “on” with high ionic conductivities in a liquid state. When an electrochemical device system (filled with the phase change electrolyte) encounters abnormal high temperature due to overcharge or shorting, the phase change electrolyte inside the device is capable of switching “off” with low ionic conductivities in a gel state and shut down ionic conductive flow to prevent disastrous electrochemical or chemical events, such as thermal runaway and explosion. When temperature of the electrochemical device returns to normal, the phase change material inside the electrochemical device can switch back to “on” with high ionic conductivities in a liquid state, thereby providing electrochemical devices with inherent safety, especially for rechargeable lithium batteries.