  Hybrid electrolyte materials comprising polymer-ionic salt matrixes embedded
with garnet particles constitute a promising class of materials for the
realization of all-solid-state batteries. In addition to providing solutions to
the safety issues inherent to current liquid electrolytes, hybrid polymer
electrolytes offer advantages over other solid-state electrolytes. This is
because their functional properties such as ionic conductivity, electrochemical
stability, mechanical and thermal properties can be tailored to a particular
application by independently optimizing the properties of the constituent
materials. Thereby, providing a rational approach to solving bottlenecks
currently preventing solid-state electrolytes from practical implementation
into battery devices. This review starts with a survey of solid-state
electrolytes, focusing on their materials and ion transport limitations. Next,
we summarize the current understanding of transport mechanisms in composite
polymer electrolytes (CPEs) with the purpose of identifying materials solutions
for further improving their properties. The overall goal of the review is to
foster heightened research interest in these hybrid structures to rapidly
advance development of future all-solid-state battery devices.
