Effects of conductive binder on the electrochemical performance of lithium titanate anodes

An eco-friendly water-based binder consisting of a combination of intrinsically conducting polymer poly-3,4-ethylenedioxythiopene:polystyrene sulfonate (PEDOT:PSS) dispersion and carboxymethylcellulose (CMC) proposed as component of Li4Ti5O12-based negative electrode has been studied at different compositions and compared with conventional PVDF binder. Morphology and structure of the composite materials were investigated by X-ray diffraction, scanning electron microscopy and EDX analysis. Electrochemical characterization was performed by galvanostatic charge-discharge experiments, cyclic voltammetry and impedance spectroscopy. The electrode with combined PEDOT:PSS/CMC binder has superior properties, in particular increased specific capacity and improved C-rate performance during charge-discharge. By using PEDOT:PSS/CMC binder instead of PVDF, the practical specific capacity was increased up to 14% (157 mAh g(-1) at 0.2 C, normalized to total electrode mass). Highest stability during long cycling was observed for Li4Ti5O12-electrode with this binder at < 1% decay after 100 cycles at 1 C. Electrochemical impedance spectra reveal a significant decrease of interfacial resistance and an increase of apparent diffusion coefficients for Li4Ti5O12 anode material with this binder, which supports improved functional characteristics of the electrode. As combined polyelectrolyte dispersion, the proposed conductive binder is an efficient alternative to the non-conductive PVDF binder for commercial lithium ion batteries.