Engineering a zero-strain CoNb₂O₆ anode via ZIF-67-derived sol-gel pyrolysis for ultra-stable lithium-ion capacitors
Shuo Zhao, Zhen Liu, Ruiyong Chen, Yong Deng, Chunzhen Yang, Peng Zhang
Abstract
The anode in lithium-ion capacitors (LICs) plays a pivotal role in balancing charge/discharge kinetics and determining overall device performance. In this study, we present a novel synthesis strategy for a well-structured CoNb₂O₆ (CNO) anode, utilizing a ZIF-67 precursor and a sol-gel pyrolysis approach. Electrochemical evaluations in half-cell configurations demonstrate that CNO exhibits exceptional cycling stability, retaining 84.1 % of its capacity after 15,000 cycles at a high current density of 10 A g −1 , corresponding to an ultra-low capacity decay of just 0.0011 % per cycle. Combined X-ray diffraction (XRD) and electron microscopy studies reveal that CNO maintains a highly stable crystal structure, qualifying it as an ideal “zero-strain” anode material. Furthermore, synchrotron radiation X-ray absorption fine spectroscopy (XAFS) and X-ray photoelectron spectroscopy (XPS) provide mechanistic insights into the lithium insertion process in CNO. Its excellent cycle stability ranks among the top in all lithium-ion battery anode materials. Notably, when integrated into a full LIC device, the CNO anode enables an outstanding energy density of 155.67 Wh kg −1 at a power density of 200 W kg −1 . These findings offer valuable guidance for the rational design of high-performance anodes, paving the way for the commercial advancement of LIC technology.