Using a simple mathematical model, we demonstrate that statistical kinetics of phasetransforming nanoparticles in porous electrodes results in macroscopic non-monotonic transient currents, which could be misinterpreted as the nucleation and growth mechanism by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory. Our model decouples the roles of nucleation and surface reaction in the electrochemically driven phase-transformation process by a special activation rate and the mean particle-filling speed of active nanoparticles, which can be extracted from the responses of porous electrodes to identify the dynamics in single composing nanoparticles.

Nano-sized ceramic fillers provide a promising approach to enhancing polymer electrolytes in terms of the interfacial chemistry, ionic conductivity, and C-rate performance of Li-ion cells, if their dispersibility and compatibility in a polymer matrix can be well managed. In this work, a nano-crystalline TiO 2 -PMMA hybrid is prepared by in situ crystallization, and its structure and properties are characterized by XRD, FTIR, TG and HRTEM. The enhancements provided by the nano-crystalline TiO 2 -PMMA hybrid as an additive in a PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) based composite polymer electrolyte, including in the pore distribution, electrolyte uptake, ionic conductivity, and electrochemical properties, are confirmed by SEM, linear sweep voltammetry (LSV), charge-discharge cycle testing and AC impedance measurements. The results obtained in this work show that, after the process of annealing, the nano-crystalline TiO 2 -PMMA hybrid can retain a good dispersibility in PVDF-HFP.Moreover, the nanohybrid doped PVDF-HFP CPE exhibits improved pore distribution, electrolyte uptake and ionic conductivity. Even more importantly, LiCoO 2 /Li cells with doped CPE exhibit good C-rate performances, which is confirmed by AC impedance results, which show a remarkable enhancement in the interfacial compatibility between the doped CPE and the electrode.

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