Understanding Li-ion battery processes at the atomic- to nano-scale

Review—Promises and Challenges of In Situ Transmission Electron Microscopy Electrochemical Techniques in the Studies of Lithium Ion Batteries

“…This defect limits their development in designing a new generation of LIBs with higher energy density and longer cycle life, in order to achieve high-energy storage targets in hybrid electric vehicles (HEVs) and electric vehicles (EVs). 18 The fundamental phase-transformation mechanisms in the lithiation and delithiation processes are still under debate. 32 Purushothaman, et al, predicted that Li may build up at the interface between the anode and electrolyte upon charging when the Li flux from the charge-transfer reaction at the interface of graphite and solid electrolyte interphase (SEI) layer was quicker than the Li diffusion flux into the graphite.…”

“…35,36 Thirdly, fracture of the active electrode material uncovers more surfaces to the electrolyte, resulting in spontaneous formation of additional SEI layers which accelerate the loss of capacity-though they also act as a protective film against electrolyte decomposition at the electrode-electrolyte interface. 12,18 One method to overcome detrimental effect like the huge volume changes that occur in the new high-capacity electrode materials is the use of nanoscale or nanostructured materials, such as nanorods, 37,38 nanowires, [39][40][41] and nanotubes [42][43][44] to substitute for the micrometersized materials that were used in the first generation of LIBs. A good example of the use of nanoscale electroactive materials is the Ge-nanoparticle (NP) anode that retains high capacity without any noticeable cracking through ∼260% volume changes after multiple cycles.…”

“…The small dimensions and size-dependent properties of nanomaterials demand use of detection techniques with nanometer or even better spatial resolution, which is crucial to unveil the mechanisms of charge-storage or capacity-loss at a single-particle level, instead of averaging over an ensemble of particles. 18 The challenge remains for LIBs to provide a higher energy density for a cathode and anode, to deliver a long cycle life and safety.…”

“…[17][18][19][20] Achievements in the area of in situ microscopy in the past five years have brought material characterization techniques to the point where these questions may be studied. 21 Over 100 papers relating to the application of in situ TEM electrochemistry in LIB z E-mail: zhxie@cwnu.edu.cn; jzhang@gamry.com each year have been published according to an analysis by Web of Science.…”

“…14 Recently, in situ electrochemical transmission electron microscopy (TEM) techniques have been invented as a powerful tool to unveil the dynamic (real-time) electrochemical reaction processes and degradation mechanisms of electrode materials at atomic and nanoscale under typical operating conditions. [17][18][19][20] Achievements in the area of in situ microscopy in the past five years have brought material characterization techniques to the point where these questions may be studied. 21 Over 100 papers relating to the application of in situ TEM electrochemistry in LIB z E-mail: zhxie@cwnu.edu.cn; jzhang@gamry.com each year have been published according to an analysis by Web of Science.…”