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

Abstract 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.