Electrochemical Performance of LixSiON Polymer Electrolytes Derived from an Agriculture Waste Product, Rice Hull Ash

Richard Laine

Eleni Temeche, Xinyu Zhang, and Richard Laine (2021)

ACS Applied Polymer Materials, 3:2144-2152.

The electrochemical performance of LixSiON (x = 2, 4, and 6) polymer electrolytes derived from the agricultural waste, rice hull ash (RHA, 80–90 wt % SiO2), is reported. Silica can be extracted from RHA by base-catalyzed reaction with hexylene glycol forming the spirosiloxane [(C6H12O2)2Si, SP] that distills from the reaction solution. LixSiON polymer electrolytes form on reacting SP with xLiNH2, offering a low-cost, low-temperature, and green synthesis route. The effect of N and Li+ concentrations in the polymer electrolytes are correlated with ionic and electrical conductivity. X-ray photoelectron spectroscopy studies confirm that N and Li contents increase with increasing LiNH2 content. The amorphous nature and high Li+ contents of the Li6SiON electrolyte provide an optimal ionic conductivity (6.5 × 10–6) at ambient temperature when coated on Celgard. Furthermore, the LixSiON polymer electrolytes offer high Li+ transference numbers (∼0.75–1), enabling assembly of Li symmetric cells with high critical current densities (3.75 mA cm–2). Finally, Li-SPAN (sulfurized, carbonized polyacrylonitrile) half-cells with Li6SiON polymer electrolytes deliver discharge capacities of ∼765 and 725 mAh/g at 0.25 and 0.5 C rates over 50 cycles.

Lithium ion battery, Solid electrolyte, polymer precursor, rice hull ash

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