Co<sub>3</sub>O<sub>4</sub> Nanosheets as Battery-Type Electrode for High-Energy Li-Ion Capacitors: A Sustained Li-Storage <i>via</i> Conversion Pathway.

Sennu, Palanichamy; Madhavi, Srinivasan; Aravindan, Vanchiappan; Lee, Yun-Sung · ACS Nano · 2020

basic_science · Level V

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Abstract

We report the excellent charge storage performance of high-energy Li-ion capacitors (LIC) fabricated from the mesoporous Co<sub>3</sub>O<sub>4</sub> nanosheets as the conversion-type battery component and Jack fruit (<i>Artocarpus heterophyllus</i>) derived activated carbon as a supercapacitor electrode, especially at high temperatures (50 and 40 °C). Prior to the fabrication, the electrochemical prelithiation strategy was applied to Co<sub>3</sub>O<sub>4</sub> to alleviate the irreversibility and enrich the Li-ions for electrochemical reactions (Co<sup>0</sup> + Li<sub>2</sub>O). The LIC delivered a maximum energy density of ∼118 Wh kg<sup>-1</sup> at a high temperature of 50 °C. The significant difference is observed at a high rate of 2.6 kW kg<sup>-1</sup> at 50 °C with excellent cycle stability up to 3000 cycles, with a retention of ∼87% compared with the LIC cycled at room temperature (∼74%). The magnificent electrochemical performance clearly demonstrates that the mesoporous structure and residual carbon synergistically facilitated the Li<sup>+</sup>/electron transport and hinder undesirable side reactions with electrolytes to realize high-energy density at high temperatures.