Novel single-ion conducting polymer electrolytes with high toughness and high resistance against lithium dendrites

Solid-state polymer electrolytes are considered as an alternative to classic liquid electrolytes, particularly for application in high-energy lithium metal batteries. With respect to common dual-ion conductors, single-ion conducting polymer electrolytes (SIC-PEs) are less affected by lithium dendrites growth and thus are particularly interesting for application in lithium metal batteries. In this work, novel SIC-PEs are developed, based on an ionomer having poly(ethylene- alt -maleimide) backbone and lithium phenylsulfonyl(trifluoromethanesulfonyl)imide pendant moieties, further blended with poly(ethylene oxide) (PEO) and poly(ethylene glycol) dimethyl ether (PEGDME). These SIC-PEs exhibit ionic conductivity around ∼ 7 × 10 −6 S·cm −1 at 70 °C, lithium transference number close to unity, and excellent mechanical properties, with fracture toughness over 30 J·cm −3 . Additionally, the electrolytes show very high resistance against lithium dendrites growth, by cycling for more than 1200 h in Li° symmetric cells at a current density of 0.1 mA·cm −2 . LiFePO 4 ∥Li° cells with these SIC-PEs were cycled at 70 °C and C/10, showing initial capacity of almost 160 mAh·g −1 and residual capacity of 45% after 100 cycles. This work shows that single-ion conducting polymer electrolytes based on poly(ethylene- alt -maleimide) backbone are promising materials for application as electrolytes or catholytes in lithium metal polymer batteries.