Probing the Additional Capacity and Reaction Mechanism of the RuO2 Anode in Lithium Rechargeable Batteries

The structural changes and electrochemical behavior of RuO2 are investigated by using in situ XRD, X‐ray absorption spectroscopy, and electrochemical techniques to understand the electrochemical reaction mechanism of this metal oxide anode material. Intermediate phase‐assisted transformation of RuO2 to LiRuO2 takes place at the start of discharge. Upon further lithiation, LiRuO2 formed by intercalation decomposes to nanosized Ru metal and Li2O by a conversion reaction. A reversible capacity in addition to its theoretical capacity is observed on discharging below 0.5 V during which no redox activity involving Ru is observed. TEM, X‐ray photoelectron spectroscopy, and the galvanostatic intermittent titration technique are used to probe this additional capacity. The results show that the additional capacity is a result of Li storage in the grain boundary between nanosized Ru metal and Li2O. Findings of this study provide a better understanding of the quantitative share of capacity by a unique combination of intercalation, conversion, and interfacial Li storage in a RuO2 anode. Add this, RuO2: The electrochemical reaction mechanism of RuO2 as anode is investigated to determine the source of capacity found in addition to its known theoretical capacity by using X‐ray‐based characterization and electrochemical techniques. The results show that 4 mol of Li atoms are stored by a conversion reaction whereas the additional capacity is achieved through a fast Li‐ion storage in the grain boundary. This forms the basis of advanced Li‐ion batteries capable of high energy and power densities.