RESUMEN
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 (Rion-1) 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 (Cdl,max) and the associated frequency (f0). Consequently, these ion-transport parameters can be used to predict capacity retention during low-temperature cycling, and the adopted approach therefore can help to mitigate low-temperature LIB performance degradation and thus contribute to the fabrication of next-generation rechargeable batteries.
RESUMEN
In order to study a diffusive behavior of Li+ in Li intercalated graphites, we have measured muon spin relaxation (µ+SR) spectra for C6Li and C12Li 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 (Ea) for C6Li is obtained as 270(5) meV, while Ea = 170(20) meV for C12Li. Assuming a jump diffusion of Li+ in the Li layer of C6Li and C12Li, a self-diffusion coefficient DLi at 310 K was estimated as 7.6(3) × 10-11 (cm2 s-1) in C6Li and 14.6(4) × 10-11 (cm2 s-1) in C12Li.