Abstract
Smart electronics and wearable devices require batteries with increased energy density, enhanced safety, and improved mechanical flexibility. However, current state‐of‐the‐art Li‐based rechargeable batteries (LBRBs) use highly reactive and flowable liquid electrolytes, severely limiting their ability to meet the above requirements. Therefore, solid polymer electrolytes (SPEs) are introduced to tackle the issues of liquid electrolytes. Nevertheless, due to their low Li+ conductivity and Li+ transference number (LITN) (around 10−5 S cm−1 and 0.5, respectively), SPE‐based room temperature LBRBs are still in their early stages of development. This paper reviews the principles of Li+ conduction inside SPEs and the corresponding strategies to improve the Li+ conductivity and LITN of SPEs. Some representative applications of SPEs in high‐energy density, safe, and flexible LBRBs are then introduced and prospected.
Highlights
PAN is attracting a lot of research attention due to its high Li+ conductivity and excellent physical properties
Oligomers and other active groups can be grafted onto polymer backbones to reduce overall crystallinity, while copolymers can induce regular phase separation
Additives help to enhance the ionic conductivity because the interaction of the particles with the polymer segments provides a favorable environment for Li+ transport in the matrix
Summary
The intensive research effort directed towards SPEs was mainly driven by their enhanced safety and applicability to batteries needing high energy density and good menchanical flexibility.[25] Battery safety is the top priority, especially for high energy storage systems.[26] The safety issues relating to state-of-the-art LBRBs are associated with the use of flammable organic carbonate electrolytes. Liquid electrolytes offer high ionic conductivity and good interfacial contact with the electrode materials,[27] their LITNs are low, being 0.2–0.3.[28] liquid electrolytes exhibit high leakage and reactivity.[29] The exothermic reactions between the electrolyte and the electrode that occur during battery abuse conditions increase the overall battery temperature very quickly, triggering further electrolyte decomposition as well as generating flammable gases.[30] This process is referred to as the notorious thermal runaway. The ease of manufacture of SPEs makes them adaptable to state-of-the-art battery technology and it is believed that such technology will dominate in the field of smart electronics in the future
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