Lithium insertion into titanium dioxide (anatase) electrodes: microstructure and electrolyte effects

Insertion characteristic:; of anatase electrodes were studied on single-cry stal and polycrystalline electrodes of different microstructures. The lithi um incorporation from propylene carbonate solution containing LiClO4 and Li (CF3SO2)(2)N was studied by means of cyclic voltammetry (CV), the quartz cr ystal microbalance (QCM) and the galvanostatic intermittent titration techn ique (GITT). The electrode microstructure affects both the accessible coeff icient x and the reversibility of the process. The highest insertion activi ty was observed for electrodes composed of crystals with characteristic dim ensions of similar to 10(-8) m. The insertion properties deteriorate for hi gher as well as for smaller crystal sizes. Enhanced insertion was observed in Li(CF3SO2)(2)N-containing solutions. Lithium insertion is satisfactorily reversible for mesoscopic electrodes; the reversibility in the case of com pact polycrystalline and single-crystal electrodes is poor. The reversibili ty: of the insertion improves with increasing electrolyte concentration. Th e lithium diffusion coefficient decreases with increasing x and ranges betw een 10(-15) and 10(-18) cm(-2) s(-1).