The demand for high power and fast-charging lithium-ion batteries motivates the discovery of electrochemically stable next-generation electrolytes. High lithium transference number (tLi+) electrolytes, in which the current is carried primarily by Li+, are specifically useful in avoiding lithium dendrite growth and catastrophic battery failure at fast cell (dis)charge rates. This contribution will describe the synthesis of lithium bis(nonenylmalonato) borate (LiBNMB) and its polymerization by acyclic diene metathesis (ADMET) polymerization to produce the polymeric salt poly(lithium bis (nonenylmalonato) borate) (P(LiBNMB)) with molecular weights Mn = 2.7–55.4 kg/mol and dispersities Mw/Mn = 1.6-3.2. Using cyclic voltammetry, we demonstrate that LiBNMB and P(LiBNMB) solutions in propylene carbonate at 22 °C exhibit remarkably little decomposition after the first cycle upon sweeping between 0–8 V (v. Li/Li+). The diffusivities of both the Li+ and the polymeric anions were determined using 7Li and 1H pulsed–field gradient NMR (PFG-NMR), from which the transference numbers tLi+ and conductivities of these electrolytes were determined. Notably, tLi+ ≥ 0.95 when the degree of polymerization is greater than Nn ≥ 50. Electrolyte conductivities were further corroborated using electrochemical impedance spectroscopy measurements. These studies demonstrate that the polymeric salt P(LiBNMB) exhibits high transference numbers even at low degrees of polymerizations.

High lithium–ion transference number electrolytes based on poly(lithium bis(alkenylmalonato)borate) solutions

2019 Spring National Meeting

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