Electron delocalization-driven high dielectric electrolyte for solid-state lithium metal batteries

Solid-state polymer electrolytes hold significant promise for solid-state lithium metal batteries but have been severely plagued by how to simultaneously achieve high ionic conductivity and construct a stable interphase. Here, we propose an electron delocalization engineering strategy by introducing the conducting polymer with the conjugated system into solid-state polymer electrolytes to solve the above issue. The electron delocalization of conducting polymer such as proton-doped polyaniline can generate tremendous “micro-capacitors” to increase dielectric constant, which significantly facilitate the dissociation of Li salts to enhance the Li+ transport, meanwhile they can accelerate the bond-cleavage dynamics of anions to form an inorganic-rich interphase. Solid-state polymer electrolytes with proton-doped polyaniline deliver a high ionic conductivity at a wide temperature range (0.892 mS cm−1 at 25 °C and 0.053 mS cm−1 at −40 °C), which enables Li electrode to achieve a large critical deposition areal capacity of 26.3 mAh cm−2. The Li | |LiNi0.8Co0.1Mn0.1O2 cells operate effectively over a wide temperature range from −40 °C to 45 °C and exhibit a life span of over 13000 cycles at 1800 mA g−1, which is highly desired for practical solid-state lithium metal batteries due to the inaccessible design for the current polymer electrolytes. One of the main challenges in solid-state polymer electrolytes is to simultaneously achieve high ionic conductivity and a stable interphase. Here, authors propose an electron delocalization engineering strategy by introducing the conducting polymer into polymer electrolytes to realise a high ionically conducting and stable polymer electrolyte.