The rapid advancement of all-solid-state battery (ASSB) technology has positioned sulfide electrolyte/silicon-based anode systems as promising alternatives in both the academic and industrial sectors, with such systems receiving considerable attention recently. Given the high reactivity and strain accommodation challenges involved in this newly emerging system, ensuring its interface compatibility is highly important. This review presents an in-depth discussion of recent developments in the stability and design of the interface between sulfide electrolytes and silicon-based anodes, as well as related perspectives. Major interface behaviors and the mechanisms underlying chemical/electrochemical and mechanical instability at the interface are discussed, underscoring how these intertwined factors contribute to the complexity of interface failure. Moreover, sulfide electrolyte and silicon-based anode modification methods are highlighted. Advancements in in situ/operando advanced characterization methods in interface analysis are emphasized. Further breakthroughs require precise interface regulation, as well as the deployment of multimodal, multiscale, and advanced intelligent characterization techniques, which may provide new insights into interfacial phenomena. These advancements will inform rational material designs, increase interfacial compatibility, and accelerate the practical implementation of sulfide electrolyte/silicon-based anode ASSBs. This review provides a comprehensive overview of the interface failure mechanisms and modification strategies in sulfide electrolyte|silicon-based anode systems, aiming to improve interfacial compatibility. It also emphasizes the pivotal role of advanced intelligent interface characterization techniques in unveiling interfacial evolution processes and guiding the rational design of high-performance solid-state batteries.
Sodium-ion batteries (SIBs) represent a compelling alternative to lithium-ion batteries (LIBs) for large-scale industrialization, primarily due to their cost-effectiveness, enhanced safety profiles, and superior performance in cold climates. Within the spectrum of cathode materials, sodium-based layered transition-metal oxides (NaxTMO2) stand out for their high energy density and manufacturing scalability. Nevertheless, practical deployment is severely impeded by surface and interfacial instabilities triggered by environmental exposure and electrolyte interactions. This paper offers a comprehensive review of the interfacial instability mechanisms in NaxTMO2, encompassing their origins, evolutionary pathways, mitigation strategies, and cutting-edge characterization techniques. We begin by elucidating the fundamental thermodynamics and kinetics governing surface and interfacial behaviors, demonstrating how the coupling of bulk and interface evolution induces structural degradation and capacity decay. Subsequently, we systematically classify stabilization strategies—including bulk-phase engineering, interfacial architecture design, and electrolyte optimization—evaluating their efficacy in addressing specific failure modes. The critical roles of in situ and operando characterization in decoding interfacial evolution under coupled electrochemical, mechanical, and chemical stresses are also analyzed. Finally, we propose future research directions for interface stabilization, highlighting the imperative to translate fundamental insights into actionable design principles for SIBs and next-generation energy storage systems.
Aqueous zinc-iodine batteries (AZIBs) have emerged as highly promising energy storage systems because of their inherent safety and low cost. However, conventional two-electron AZIBs (2eZIBs) are limited by their relatively low energy density (211 mAh g−1 based on the I−/I2 2e reaction), while four-electron AZIBs (4eZIBs) can potentially double the capacity to 422 mAh g−1 but still face critical challenges, including polyiodide shuttling, I+ hydrolysis, and zinc dendrite growth. Here, we systematically analyze the energy storage mechanisms of AZIBs, focusing on the differences and stability issues between two-electron (I−/I2) and four-electron (I−/I2/I+) redox pathways. To address these challenges, this review comprehensively summarizes electrolyte optimization strategies (e.g., functional additives and gel electrolytes) and separator modification approaches for suppressing polyiodide shuttles, stabilizing I+ oxidation states, and optimizing zinc deposition behavior. Additionally, we evaluate the practical energy density of AZIBs and suggest future research directions, including the design of functionalized asymmetric electrolytes and the implementation of interface engineering approaches to optimize separators, thereby facilitating the practical application of AZIBs in large-scale energy storage systems. This review systematically elaborates the energy storage mechanisms and key challenges facing both the cathode and anode in AZIBs, while also providing an in-depth discussion of regulatory strategies such as electrolyte optimization and separator modification. Collectively, these insights offer theoretical guidance for the development of high energy density and long cycle life AZIB systems.
Iridium-based catalysts remain the benchmark catalysts for the oxygen evolution reaction (OER) in acidic media, a critical half-reaction in proton exchange membrane water electrolyzers (PEMWEs), yet their large-scale deployment is limited by high cost, restricted availability, and progressive degradation under severe operating conditions. This review delivers a comprehensive evaluation of advances in catalytic mechanistic understanding, structural design, and practical implementation of Ir-based electrocatalysts. In acidic electrolytes, the OER has been primarily interpreted through the adsorbate evolution mechanism (AEM) and the lattice oxygen-mediated mechanism (LOM). However, growing evidence highlights the significance of complementary pathways, including oxygen vacancy site-mediated processes, oxygen path (direct O–O radical coupling), acid–base and direct coupling pathways, coupled oxygen evolution, multi-hole (local high concentration of OH) oxygen evolution, sequential oxygen kinetics, and electrochemical-thermal mechanisms. These additional models provide more detailed insights into reaction intermediates, active-site dynamics and kinetic bottlenecks, thereby further clarifying the activity-stability trade-off. Key degradation routes including lattice dissolution, surface reconstruction, and support corrosion are reviewed, together with the structure–function relationships derived from morphology regulation, alloying, heteroatom incorporation, phase and lattice engineering, and integration with conductive supports. Representative systems ranging from elemental Ir and IrO2 polymorphs to single-atom catalysts and perovskites are critically assessed with respect to their electronic structure, active-site configuration, and long-term durability. Industrial application aspects are also discussed in detail, encompassing the industrial-level development of PEMWE technology, regional progress toward large-scale implementation, major research organizations and enterprises, potential application domains, and recent developments in industrial devices. In addition, the accelerating role of artificial intelligence and machine learning in catalyst discovery is also discussed. Persisting challenges and research opportunities are further outlined to guide the rational design of robust, scalable, and cost-efficient Ir-based electrocatalysts for next-generation acidic water electrolysis.
The physicochemical properties of cathode‒electrolyte interfaces (CEIs) play a key role in determining long-term cycling and reliable electrochemical behaviors, which are critically important in high-voltage batteries. Increasing the operating voltage improves the energy density of a battery but accelerates cathode degradation and destabilizes the CEI. Currently, the interface dynamics and working mechanism of CEIs are still under evaluation and debated. In this review, we first summarize the key CEI-related challenges and the principal structural and chemical degradation mechanisms of high-voltage cathode materials, underscoring their intrinsic inconsistencies, stochasticity, and failure modes. We then explore the intrinsic correlation between CEI degradation and electrochemical deterioration and propose targeted strategies for regulating CEIs. Furthermore, we highlight the recent advances in characterization techniques for tracking dynamic structural and compositional changes. Through this comprehensive review, we aim to deepen the understanding of CEI behavior and offer valuable insights for guiding the design and development of more reliable and sustainable next-generation high-energy batteries.
