Transition from Vogel-Fulcher-Tammann to Arrhenius Ion-Conducting Behavior in Poly(Ethyl Acrylate)-Based Solid Polymer Electrolytes via Succinonitrile Plasticizer Addition

Abstract

Solid polymer electrolytes (SPEs) offer potential advantages over liquid electrolytes, including flexibility, safety, and processability. However, they suffer from low room-temperature ionic conductivity. Recently, it has been reported a poly(ethyl acrylate) based (polyEA) SPE, by incorporating 50 wt% of succinonitrile (SN) solid plasticizer, 30 wt% of lithium salt and 5 wt% of fluoroethylene carbonate additive, which achieves a high room-temperature ionic conductivity of 1.01 × 10−3 S cm−1 (Nat. Nanotechnol, 2022, 17, 768-776). This novel SPE exhibits stability against Li0 and anodic stability up to 4.9 V vs Li+/Li. However, the specific mechanism responsible for its high ionic conductivity remains elusive. In this work, by adjusting the weight ratio of SN in the SPE, a transition from Vogel-Fulcher-Tammann to Arrhenius ion-conducting behavior is observed. It is demonstrated that the addition of SN leads to the gradual decoupling of Li-ion from the polymer backbone and its coordination with SN, as revealed by 6Li solid-state nuclear magnetic resonance spectroscopy. As a result, Li-ion migration primarily occurs through SN rather than the segmental motion of the polymer backbone. Performances of the SPE in Cu||Li, Li||Li and a LiFePO4||Li pouch cells are shown to demonstrate the commercial viability of this SPE in Li0-anode solid-state batteries.

Broadening solid ionic conductor selection for sustainable and earth-abundant solid-state lithium metal batteries

“…S4, ESI†). Owing to the highly crosslinked polyacrylate backbone, its restricted chain mobility, and lower solvating ability towards Li + , an Arrhenius-type ion conduction mechanism 25,26 was realized in UVEA, consistent with the temperature-dependent conductivity curve (a linear relationship between log σ and 1000/ T , Fig. S7, ESI†).…”

Making Plasticized Polymer Electrolytes Stable Against Sodium Metal for High‐Energy Solid‐State Sodium Batteries

“…The temperature-dependent ionic conductivity curve (Figure S2a) indicates the Arrhenius-type ion-conducting mechanism in FEC/SN-PCE, which is due to the decoupling of Na + ions conduction from the polymer segmental relaxation and the strong coordination of SN and FEC to the Na + ion. [11] At the same time, the strong solvation ability of SN and FEC toward NaPF 6 also leads to a high ionic conductivity but a low Na + transference number, similar to the case in liquid electrolytes. Compared with SN-PCE, FEC addition in FEC/ SN-PCE would facilitate sodium ion solvation, [12] thereby improving the Na + transference number due to the possible "fluorous effect" where FEC interacts significantly with PF 6…”

Computational approach inspired advancements of solid-state electrolytes for lithium secondary batteries: from first-principles to machine learning

“…151–153 Recent advancements in MD and DFT simulations have provided insights into the working principles of SN as a plasticizer. 154,155 The calculated radial distribution functions ( g ( r )) and coordination numbers ( n ( r )) (Fig. 3(h)) revealed that the interaction between SN and lithium salt was primarily dominated by Li + and the N atom of SN, while the Li + ⋯C and Li + ⋯polymer interactions were comparatively insignificant.…”