Real Time Observation of Lithium Insertion into Pre-Cycled Conversion-Type Materials

Abstract

Conversion-type electrode materials for lithium-ion batteries experience significant structural changes during the first discharge–charge cycle, where a single particle is taken apart into a number of nanoparticles. This structural evolution may affect the following lithium insertion reactions; however, how lithiation occurs in pre-cycled electrode materials is elusive. In this work, in situ transmission electron microscopy was employed to see the lithium-induced structural and chemical evolutions in pre-cycled nickel oxide as a model system. The introduction of lithium ions induced the evolution of metallic nickel, with volume expansion as a result of a conversion reaction. After pre-cycling, the phase evolutions occurred in two separate areas almost at the same time. This is different from the first lithiation, where the phase change takes place successively, with a boundary dividing the reacted and unreacted areas. Structural changes were restricted at the areas having large amount of fluorine, implying the residuals from the decomposition of electrolytes may have hindered the electrochemical reactions. This work provides insights into phase and chemical evolutions in pre-cycled conversion-type materials, which govern electrochemical properties during operation.

Structural evolution and lithium-storage mechanism of the FeTiO3@Fe2TiO5 endogenous heterojunction

“…10,11 However, FeTiO 3 , which is a typical semiconductor, exhibits a low electronic conductivity, which adversely affects its lithium-storage performance. [12][13][14] In recent years, composite formation or doping of FeTiO 3 has been adopted as an effective strategy to increase its conductivity. For example, Nb doping in FeTiO 3 nanosheets introduces impurity energy levels, because of which more charge carriers participate in the conduction process and thus improve the electrochemical performance.…”

In Operando Neutron Scattering Multiple‐Scale Studies of Lithium‐Ion Batteries

“…The extraction process involves the damage of battery condition and the washing treatment of components (typically electrode or separator), implying the possibility of status change in the active compounds and compromising the reliability of the results. [ 22–30 ]…”

“…The extraction process involves the damage of battery condition and the washing treatment of components (typically electrode or separator), implying the possibility of status change in the active compounds and compromising the reliability of the results. [22][23][24][25][26][27][28][29][30] The limitations of ex situ approaches have stimulated the development of the in operando or in situ characterizations for battery research. For example, transmission electron microscopy has been used to study the real-time intercalation process of lithium ions at the atomic scale.…”