Electrolytic solutions of lithium-ion batteries can be modified with additives to improve their stability and safety. Electroactive molecules can be used as such additives to act as an electron (redox) shuttle between the two electrodes to prevent overcharging. The electroactive ionic liquid, 1-ferrocenylmethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (TFSI), was synthesised and its electrochemical properties were investigated when diluted with ethylene carbonate-diethyl carbonate solvent at various concentrations. Cyclic voltammetry data were gathered to determine the redox potential, diffusion coefficient and heterogeneous rate constants of the electroactive imidazolium TFSI ionic liquid in the carbonate solution. The properties of this molecule as an additive in lithium battery electrolytes were studied in standard coin cells with a metallic Li anode and a Li4Ti5O12 cathode.

We report on the thermal stability of lithium iron phosphate (LiFePO4) cathode material as investigated by accelerating rate calorimetry (ARC). LiFePO4 (LFP) was prepared using three different synthetic methods, namely, solid state (P1), hydrothermal (P2) and molten state (P3) and have different particle sizes (in the range of ∼100 nm–3 μm) and different surface areas (in the range of ∼6–14 m2 g−1). The thermal stability was evaluated, prior and after charging LiFePO4, in the presence of either carbonate solvents (ethylene carbonate (EC): diethyl carbonate (DEC) (1:2 v/v)) or electrolyte (1 M LiPF6 in the same solvent). In the presence of the electrolyte, LiFePO4 is shown to be stable up to 280°C or 220°C for uncharged or charged cathode materials, respectively. The surface area of LiFePO4 is found to affect the initial self-heating rate (SHR) of the charged materials reaction with the electrolyte, while the presence of the LiPF6 salt reduces significantly the SHR of the combustion reaction of carbonates solvent initiated by the oxygen released from the cathodes; forming Fe2P2O7 at elevated temperatures.

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