With the increased penetration of energy storage devices in daily life, safety hazard and energy density issues are attracting greater and greater interest. Conventional liquid electrolytes suffer from leakage, flammability, gas evolution, dendrite hazards, and so on, especially when matching with high-energy-density metal anodes. Though solid-state electrolytes (SSEs) are promising candidates for the next-generation safe and high energy density energy storage system, individual SSE fails to meet the asynchronous demands of cathode and anode, because of their intrinsic solid chemistry properties. Among numerous modified approaches related to SSEs chemistry, asymmetric SSEs (ASSEs) which have more than one SSE and multilayer structure take advantage of individual SSE layers and complement each other’s disadvantages, showing Janus abilities. However, there are few reviews about ASSEs. Also, the problem of interface compatibility the between different electrolytes as well as the interface of electrodes and electrolytes is hindering the development of ASSEs. This review comprehensively outlines the state of the art of ASSEs. Additionally, it summarizes the advantages and functions of ASSEs with the unique structure for different energy storage. Furthermore, the interfacial compatibility and corresponding evaluation methods are discussed. Finally, an outlook on how ASSEs will develop in the future energy storage applications is proposed.

Efficient energy storage devices with suitable electrode materials, that integrate high power and high energy, are the crucial requisites of the renewable power source, which have unwrapped new possibilities in the sustainable development of energy and the environment. Herein, a facile collagen microstructure modulation strategy is proposed to construct a nitrogen/oxygen dual-doped hierarchically porous carbon fiber with ultrahigh specific surface area (2788 m² g⁻¹) and large pore volume (4.56 cm³ g⁻¹) via local microfibrous breakage/disassembly of natural structured proteins. Combining operando spectroscopy and density functional theory unveil that the dual-heteroatom doping could effectively regulate the electronic structure of carbon atom framework with enhanced electric conductivity and electronegativity as well as decreased diffusion resistance in favor of rapid pseudocapacitive-dominated Li⁺-storage (353 mAh g⁻¹ at 10 A g⁻¹). Theoretical calculations reveal that the tailored micro−/mesoporous structures favor the rapid charge transfer and ion storage, synergistically realizing high capacity and superior rate performance for NPCF-H cathode (75.0 mAh g⁻¹ at 30 A g⁻¹). The assembled device with NPCF-H as both anode and cathode achieves extremely high energy density (200 Wh kg⁻¹) with maximum power density (42600 W kg⁻¹) and ultralong lifespan (80% capacity retention over 10000 cycles).