In situ characterization of electrochemical processes in one dimensional nanomaterials for energy storages devices

Highlights: • Recent advances of in situ characterization of 1D nanomaterials are summarized. • Various energy storage devices based on 1D nanomaterials are involved. • Significances of developing in situ characterization technologies are discussed. • Development trend of in situ characterization in 1D nanomaterials are presented. One dimensional (1D) nanomaterials, which show tremendous potential in constructing high performance energy storage device, have gained considerable research interests. However the electrochemical reaction mechanism is still elusive. The most challenging issue in energy storage is developing insightful operando probes for the electrochemical processes. Notably, the in situ characterization of 1D nanomaterials is crucial to investigate the structural changes and uncover the intrinsic reasons for the capacity fading. Therefore numerous in situ characterization methods have been developed, such as in situ electron microscopy, X-ray detection techniques, spectroscopic techniques, nuclear magnetic resonance techniques, etc. Recent developments on in situ characterization technologies are summarized in this review. Different energy storage devices are involved, including Li-ion batteries, Na-ion batteries, supercapacitors, Li–air batteries and Li–S batteries. A new type of energy storage device, single nanowire device, has been also emphasized in this article. The reported highlights and developments are further discussed in details according to their reaction mechanisms. Through in situ characterization, no completely reversible volume expansion and phase transformation were observed during the lithiation and delithiation process. More structural/morphological damage and different electrochemical mechanisms were caused by the replace of lithium ions with sodium ions. The electron/hole doping of electric double layer capacitive materials and oxidation state of pseudocapacitive materials were focused. The growth and decomposition process of Li₂O₂ and polysulfide were also observed. The optimization mechanisms, including coating and doping of high conductivity materials, were proved to increase the electric/ion conductivity and reduce the cracks. The above mentioned results indicated that 1D nanomaterials with continuous ion/electron channels and short diffusion distance for electrolyte ions showed superior structural stability. Finally, the challenges and perspectives of the in situ characterization of 1D nanomaterials during electrochemical processes are emphasized as the conclusion.