Self‐Optimizing Effect in Lithium Storage of GeO2 Induced by Heterointerface Regulation

Herein, a heterostructural hexagonal@tetragonal GeO2 (HT‐GeO2) composite has been designed based on density functional theory (DFT) calculations and synthesized via an acidic‐heating route dealt with rapid cooling, where the inner hexagonal GeO2 (H‐GeO2) phase is covered by a porous layer of tetragonal GeO2 (T‐GeO2) owing to HF etching. Interestingly, the HT‐GeO2 electrode has a self‐optimizing effect in lithium storage induced by heterointerface regulation, where the porous T‐GeO2 layer on the surface of HT‐GeO2 can act as not only a Li+/electron conducting layer, but also a buffer layer, while the inner H‐GeO2 phase can react preferentially with Li ions owing to lower intercalation energy, which is confirmed by operando XRD measurement contributing to thorough lithiation for HT‐GeO2. Moreover, the heterointerface can enhance the pseudocapacitance effect, which can boost the Li storage and accelerate the discharge‐charge process. As a result, a large capacity of 984 mAh g−1 after 500 cycles at 2 A g−1 and a capacity of 430 mAh g−1 at a high current density of 20 A g−1 are delivered. This work provides an easy and efficient way to improve the cycling stability of the GeO2 anode, and the T‐GeO2 phase would be a novel anode material in energy storage devices. A heterostruturally hexagonal@tetragonal GeO2 (HT‐GeO2) is obatined via an acidic‐heating route dealt with rapid cooling, and displays a self‐optimizing effect in lithium‐ion storage induced by heterointerface regulation, in which the kinetics is accelerated and electrochemical properties are enhanced significantly.