Ion Transport in Porous Electrodes Obtained by Impedance Using a Symmetric Cell with Predictable Low-Temperature Battery Performance.

The decline of lithium-ion battery (LIB) performance at low temperatures, caused by the nonuniform occurrence of electrochemical reactions during cycling and the resulting irreversible capacity loss, significantly hinders further LIB commercialization. Herein, we report the first solution by analyzing the impedance using symmetric cells in the absence of charge-transfer reactions to obtain a parameter quantitatively describing ion transport in porous electrodes and thus modeling the effects of nonuniform reaction occurrence. The reciprocal of ionic resistance in porous electrodes () is found to be positively correlated with capacity retention during low-temperature cycling and is approximated as the product of maximum capacitance related to electric double-layer formation () and the associated frequency ().

Li-ion diffusion in Li intercalated graphite CLi and CLi probed by μSR.

In order to study a diffusive behavior of Li in Li intercalated graphites, we have measured muon spin relaxation (μSR) spectra for CLi and CLi synthesized with an electrochemical reaction between Li and graphite in a Li-ion battery. For both compounds, it was found that Li ions start to diffuse above 230 K and the diffusive behavior obeys a thermal activation process. The activation energy (E) for CLi is obtained as 270(5) meV, while E = 170(20) meV for CLi.