Guihuan Chen

While conversion-type metal selenides are highly promising for fast-charging batteries, the microscopic origin of their ultrafast interfacial kinetics has remained largely unclear. Here, we developed a spatially confined CoSe@N-C architecture as a well-defined model platform. Using advanced operando magnetometry, we achieved quantitative decoupling of the space-charge storage contribution from conventional diffusion-controlled processes, providing direct insight into the interfacial charge storage mechanism of conversion-type metal selenides. The rigid porous carbon framework not only mitigates volume expansion but, more importantly, enforces intimate, atomic-scale contact between the in situ generated electronic (Co) and ionic (Li2Se/Na2Se) phases, maximizing the density of space-charge interfaces. Driven by this enhanced spin-electronic and ionic coupling, the spatially confined CoSe@N-C anodes deliver exceptional fast-charging capabilities and stable wide-temperature stability (from −20 to 50 °C) in both Li- and Na-ion batteries. In addition to demonstrating a high-performance electrode, this work offers quantitative insights into the space-charge mechanism, establishing a crucial physical perspective for designing next-generation ultrafast energy storage materials.

This study developed a mild heat treatment strategy (120 °C) that effectively reduces the lattice water content of Prussian blue analogues (PBAs) from 3.24H ₂ O to 1.78H ₂ O, achieving a remarkable capacity retention rate of 80% even after 750 cycles.

Titanium dioxide (TiO ₂ ) is an extremely promising anode material for lithium‐ion batteries due to its low cost, minimal volume change, and extended cycle life. However, its electrochemical performance is severely hindered by inherent issues such as poor ionic and electronic conductivity. Here, we design a dual‐phase conductor Co@TiO ₂ , which contributes a synergistic storage mode consisting of a Li‐accepting and an electron‐accepting phase. In situ magnetic characterization and experimental results reveal the space charge storage mechanism in addition to traditional insertion mechanisms. Based on these mechanisms, the specific capacity and rate performance of the Co@TiO ₂ electrode have been greatly enhanced. Under a current density of 200 mA·g ⁻¹ , the specific capacity of Co@TiO ₂ reaches 397.2 mAh·g ⁻¹ . Upon increasing the current density to 10 A·g ⁻¹ , the electrode still maintains a capacity of 83.1 mAh·g ⁻¹ after 900 cycles. This result offers a fresh perspective on the structural design of new anode materials to achieve high energy density.

Extra capacity beyond a theoretically predicted value has been widely acknowledged in transition metal-based anodes for application in lithium batteries, but the precise definition of their charge storage behaviors remains elusive owing to the intricate and dynamic interior space. Herein, an urchin-like FeOOH nanostructure is fabricated to reveal the dynamic electrochemical evolution of extra capacity. It is found that electrons continually accumulate at the interface between Fe and the Li₂O/LiOH matrix at a narrow discharge voltage range of 1–0 V, forming a space-charge storage region, thus enabling extra capacity besides the capacity from the reversible conversion reaction. Moreover, using advanced operando magnetometry technology, the significant interfacial space-charge storage behavior could be accurately quantified to be 239.1 mA h g⁻¹. In contrast, the evolution of the partially reversible solid-state electrolyte interface (SEI) functions as a diminished additional source of capacity, significantly lowering the coulombic efficiency and stability of batteries. Further, by fully exploiting the potential of the reversible interfacial space-charge storage mechanism, a well-designed lithium-ion hybrid capacitor is constructed using a reduced FeOOH anode and commercial AC cathode, achieving a high energy density of 140.4 W h kg⁻¹ and a remarkable capacity retention of ∼100% after 1000 cycles at 1 A g⁻¹. This study offers a broad insight into the extended utilization of extra capacity, paving the way for a sustainable strategy in the development of new energy batteries.

Batteries with intercalation-conversion-type electrodes tend to achieve high-capacity storage, but the complicated reaction process often suffers from confusing electrochemical mechanisms. Here, we reinterpreted the essential issue about the potential of the conversion reaction and whether there is an intercalation reaction in a lithium/sodium-ion battery (LIB/SIB) with the FeP anode based on the evolution of the magnetic phase. Especially, the ever-present intercalation process in a large voltage range followed by the conversion reaction with extremely low potential was confirmed in FeP LIB, while it is mainly the conversion reaction for the sodium storage mechanism in FeP SIB. The insufficient conversion reaction profoundly limits the actual capacity to the expectedly respectable value. Accordingly, a graphene oxide modification strategy was proposed to increase the reversible capacity of FeP LIB/SIB by 99% and 132%, respectively. The results facilitate the development of anode materials with a high capacity and low operating potential.

In this study, we construct an yolk-shell Ni@TiO2 nanosphere to investigate its performance in lithium-ion batteries. The composite possesses a synergistic storage mode consisting of a Li+-accepting and an electron-accepting phase. Used as an anode material, it delivers ultra-high specific capacity with excellent rate performance and cycling stability. In situ magnetic characterization and thermodynamic simulation reveal the existence of space charge storage mechanism. We propose an overall view on the Li storage mechanism of the Ni@TiO2 and demonstrate the importance of space charge storage for performance improvement in Li-ion batteries.

In situ magnetometry is used to verify the formation and reveal the stabilizer role of Si/Si–Co multilayer film. The resultant Si/Si–Co anode delivers an initial coulomb efficiency of 93.4% at 1 A g ⁻¹ and 85.07% capacity retention after 100 cycles.

Transition metal fluoride (TMF) conversion cathodes, with high energy density, are recognized as promising candidates for next-generation high-energy Li/Na-ion batteries (LIBs/SIBs). Unfortunately, the poor electronic conductivity and detrimental active material dissolution of TMFs seriously limit the performance of TMF-LIBs/SIBs. A variety of FeF₃-based composites are designed to improve their electrochemical characteristics. However, the storage mechanism of the conversion-type cathode for Li⁺ and Na⁺ co-storage is still unclear. Here, the storage mechanism of honeycomb iron (III) fluoride and carbon (FeF₃@C) as a general cathode for LIBs/SIBs is analyzed by kinetics. In addition, the FeF₃@C cathode shows high electrochemical performance in a full-cell system. The results show that the honeycomb FeF₃@C shows excellent long-term cycle stability in LIBs (208.3 mA h g⁻¹ at 1.0 C after 100 cycles with a capacity retention of 98.1%). As a cathode of SIBs, the rate performance is unexpectedly stable. The kinetic analysis reveals that the FeF₃@C cathode exhibit distinct ion-dependent charge storage mechanisms and exceptional long-durability cyclic performance in the storage of Li⁺/Na⁺, benefiting from the synergistic contribution of pseudocapacitive and reversible redox behavior. The work deepens the understanding of the conversion-type cathode in Li⁺/Na⁺ storage.

A new rapid bottom-up colloidal synthetic route has been developed to synthesize SnSe₂nanosheets within 5 min. A SnSe₂nanosheet-based flexible photodetector is fabricated for the first time and the resulting device displays a wide photodetection range and high flexibility.