1 research outputs found
Dual-Functional Additive for Solid Polymer Electrolytes for Enabling Highly Safe and Long-Life All-Solid-State Lithium Metal Batteries
Solid polymer electrolytes (SPEs) are a promising alternative
to
carbonate-based liquid electrolytes for realizing flexible lithium
batteries with high energy density and safety owing to their advantages
such as lightweight, thinness, no leakage of electrolytes, excellent
flexibility and processability, and good compatibility with Li-metal
electrodes. However, SPEs present new challenges such as poor ionic
conductivity and electrochemical stability as well as flammability,
which are still a concern even though they are less flammable than
liquid electrolytes. Herein, we demonstrate the dual functionalities
of dimethyl methylphosphonate (DMMP) in facilitating Li ion migration
and improving the flame retardancy of a poly(ethylene oxide) (PEO)-based
polymer electrolyte. It acts as a plasticizer that aids the dissociation
of Li salts and alleviates the binding energy between ethylene oxide
(EO) groups and Li ions by counterbalancing the binding force between
EOs and Li ions through the formation of binding interactions of DMMP
molecules and Li ions. This significantly facilitates Li ion migration
within the polymer electrolyte. Consequently, the prepared SPE exhibited
improved ionic conductivity (1.29 × 10–5 S
cm–1 at 25 °C), Li transference number (0.46),
and oxidative stability (>4.3 V). The fabricated Li/Li symmetric
cell
maintained stable cycling performance over 500 cycles with low overpotential
(41 mV) without short circuit. Importantly, the LiFePO4(LFP)/Li battery exhibited a high discharge capacity of 134.1 mAh
g–1 with outstanding capacity retention of 95.4%
after 400 cycles at 1C and excellent rate capability (123.3 mAh g–1 at 2C). Furthermore, stable cycling was confirmed
to be possible at an extended voltage range (2.5–4.1 V) and
low operating temperature (45 °C). Moreover, DMMP effectively
suppressed combustion of the polymer electrolyte owing to its strong
flame retardancy arising from the propensity to capture active radicals