Bimodal AFM-Based Nanocharacterization of Cycling-Induced Topographic and Mechanical Evolutions of LiMn₂O₄ Cathode Films

Abstract

Evolution of LiMn2O4 mechanical property during charge/discharge cycles is a critical issue because it is closely related to the performance of lithium-ion batteries. Extensive studies have been conducted by first-principles calculations/molecular dynamics simulation at the atomic level and by the nanoindentation technique at the micron scale. In this study, cycling-induced topographic and mechanical evolutions of the LiMn2O4 films are investigated at the nanoscale using the bimodal atomic force microscopy (AFM), which provides a complementary approach to bridge the gap between atomic-level calculation and micron-scale measurement. The topographic change and elastic modulus degradation of the LiMn2O4 films during the charge/discharge cycles are found to occur simultaneously and irreversibly. Moreover, a dramatic decrease in the elastic modulus of the films takes place at the first 10 cycles, which is consistent with the significant loss of the capacity and the change of the Coulombic efficiency measured by the galvanostatic method. By considering the nanoscale phenomena and the macroscopic measurement results, the reasons for the elastic modulus degradation are discussed. This study would be a valuable addition to a better understanding of the degradation mechanisms of this cathode material.

Review—Multiscale Characterization of Li-Ion Batteries through the Combined Use of Atomic Force Microscopy and X-ray Microscopy and Considerations for a Correlative Analysis of the Reviewed Data

“…This was related to the concomitant loss of capacity and was ascribed to decrease in the Li concentration [24]. Analogous results were obtained on Li-rich and LiCoO 2 film cathodes, where cycling resulted in the reduction of the elastic modulus [25,27].…”

“…For example, topographical imaging allowed to reveal nanoscale irreversible changes in the surface of LiMn 2 O 4 cathode films after different charge/discharge cycles. These observations could be related to the ageing of the material [24]. Topographical analysis has been used to investigate the effect of repeated charge/discharge cycles on LiCoO 2 cathode films.…”

“…In this context AFM can afford the mapping of the conductivity variations on sample surface through the employment of the conductive AFM (C-AFM) version. Yang et al [24] used C-AFM to investigate the reduction of conductivity due to the nonconductive SEI layer on LiMn 2 O 4 cathode films. C-AFM allowed the mapping of the nanoscale conductivity of lithium-rich thin film cathodes and determined a diminution in conductivity for these cathodes with charge/discharge cycles.…”

Boosting the Electrochemical Performance of a Spinel Cathode with the In Situ Transformed Allogenic Li-Rich Layered Phase

“…The sintering temperature will have a key effect on the crystal morphology and particle size distribution of the sample. 32 Figure 4a−c is the SEM image of the spinel material at different sintering temperatures. It can be seen from the figure that the primary particles of the S800 sample are mainly spherical particles around 200 nm.…”

“…The sintering temperature will have a key effect on the crystal morphology and particle size distribution of the sample Figure a–c is the SEM image of the spinel material at different sintering temperatures.…”