Rechargeable aluminum batteries (RABs) have gained considerable attention as next-generation energy storage systems due to Al’s high theoretical capacity, natural abundance, and inherent safety advantages. However, several key limitations related to ion transport, electrolyte stability, cathode reversibility, and anode interface remain. Remarkably, this review demonstrates that synergistic multi-ion transport mechanisms (involving Al³⁺, AlCl₄⁻, AlCl₂⁺, and AlCl²⁺) coupled with multi-electron redox reactions offer effective strategies to address these fundamental limitations. Specifically, multi-ion participation improves charge transport pathways and reduces kinetic barriers at the electrode–electrolyte interface, while multi-electron redox processes increase theoretical capacity and enhance energy storage efficiency. These mechanisms collectively provide a rational framework for advancing the electrochemical performance of RABs. We systematically evaluate recent progress across 4 interconnected research domains: (a) innovative cathode materials design enhancing structural stability and redox kinetics; (b) advanced electrolyte formulations widening the voltage window and improving ionic conductivity; (c) engineered anode interfaces mitigating passivation and dendrite formation; and (d) computational elucidation providing atomic-level insights into complex reaction pathways and ion solvation structures. Crucially, this work provides essential design principles for high-performance RABs and paves the way for their practical application by establishing fundamental connections between material properties and electrochemical performance.

Silicon (Si) has emerged as a leading candidate to replace traditional graphite anodes in the next generation of high-energy-density lithium-ion batteries, owing to its exceptionally high theoretical capacity, favorable working voltage, natural abundance, and environmental friendliness. However, substantial challenges, including poor electrical and ionic conductivity, considerable volume changes, and an unstable solid-electrolyte interphase, impede its commercial adoption. To overcome these barriers, various material optimization strategies have been developed for the synthesis of Si-based composites. This review meticulously details recent advancements and prospective studies on Si-based composites, highlighting progress in nanocomposite synthesis strategies, interface adjustments, and advanced prelithiation techniques aimed at enhancing the electrochemical performance of Si-based composite anodes. Special emphasis is placed on the Li–Si alloy storage mechanism, structural and chemical evolution at the Si anode/electrolyte interface, and precise prelithiation regulation. Finally, the practical application of Si-based anodes is discussed, providing feasible reference solutions for the development of high-performance Si-based anodes.

Anode-free lithium metal batteries (AFLMBs), comprising a simple anode collector and a complete lithium cathode, are designed to minimize safety hazards associated with active Li metals, improve energy density, and simplify battery production. However, due to the irreversible loss of active lithium and the limited active lithium on the anode side, it generally leads to a rapid capacity loss of AFLMBs after only a few cycles. To enhance the extended cycling stability of AFLMBs, a thorough investigation spanning from battery components to design principles is required. In this paper, the main factors affecting the lifetime of AFLMBs, such as the induced nucleation relationship between the collector type and deposited Li, the determinative factors of Li deposition and stripping, and the interaction of mechanical and physicochemical properties of solid electrolyte interface (SEI) with the morphological evolution of various lithium deposits were studied. Subsequently, potential approaches and avenues to enhance the extended cycling performance of AFLMBs were deliberated and proposed, including electrolyte formulation adjustment to form SEI layers that promote uniform deposition of Li, cathode compensation for additional active lithium, and lipophilic coating or collection design with low nucleation barrier. And the important role of advanced testing techniques in guiding the development of AFLMBs was summarized. Finally, the further development of AFLMBs is discussed and proposed. The purpose of this review is to deepen the comprehension of AFLMBs and contribute to achieving an unprecedented cycle life in future.

Rechargeable aluminum batteries hold great promise for high energy density and low-cost energy storage applications but are stalled by severe electrochemical side reactions (e.g., dendrite, passivation, and corrosion) at aluminum (Al) metal anode. Here, we design an aluminum ion battery with an Al-free configuration to circumvent the problems caused by the above side reactions. The feasibility of Al_xMnO₂·nH₂O cathode in aluminum ion batteries is revealed in conjunction with TiO₂ anodes by using the optimal 5 M Al(OTF)₃ electrolyte. The as-assembled aluminum ion battery enables high initial discharge capacity of 370.4 mAh g^–1 at 30 mA g^–1, favorable stability with low irreversible capacity loss, and enhanced safety. Further, the mechanism is intensively elucidated by multiple characterization results, indicative of the Al³⁺ ions (de)intercalation redox chemistry. Revealed by empirical analyses, the capacity contribution of high-voltage plateau, corresponding to the disproportionation reaction of Mn³⁺ in an Al_xMnO₂·nH₂O battery system, tends to increase with the increasing electrolyte concentration. Our findings may provide fresh impetus to the rational design of aluminum ion batteries with excellent electrochemical properties.

As alternatives to conventional rocking-chair lithium-ion batteries (LIBs), novel rechargeable batteries utilizing abundant elements (such as sodium-ion batteries, potassium-ion batteries, and magnesium-ion batteries) have shown excellent performance. Nevertheless, these emerging batteries still face several challenges, including sluggish kinetics, limited reversibility, and a lack of suitable electrode materials. By incorporating carrier ions with different properties, hybrid-ion batteries (HIBs) based on multi-ion strategies have garnered extensive attention for their potential to solve most of these problems. However, with the increasing number of carrier ions that have been demonstrated to be suitable for multi-ion strategies, there exists deficiency in clarity regarding the nomenclature and classification of HIBs. For this reason, this comprehensive review offers an in-depth analysis of the fundamental configurations of HIBs according to the reaction mechanisms of the different carrier ions involved in the electrochemical redox reaction. Then, we systematically review the electrode materials for practical implementation on the basis of the energy storage mechanisms. Moreover, the challenges confronted by the current multi-ion strategies and promising future directions for overcoming these challenges are proposed for further research. The primary objective of this review is to inspire researchers in the rational design of highly efficient electrode materials for advanced HIBs.

Phosphorus, particularly the red phosphorus (RP) allotrope, has been extensively studied as an anode material in both lithium-ion batteries (LIBs) and emerging sodium-ion batteries (SIBs). RP is featured with high theoretical capacity (2,596 mA h g⁻¹), suitable low redox potential (~0.7/0.4 V for LIBs/SIBs), abundant resources, and environmental friendliness. Despite its promises, the inherent poor electrical conductivity of RP (~10⁻¹⁴ S cm⁻¹) and significant volume changes during charge/discharge processes (>300%) compromise its cycling stability. In order to address these issues, various countermeasures have been proposed, focusing on the incorporation of materials that provide high conductivity and mechanical strength in composite-type anodes. In addition, the interfacial instability, oxidation, and safety concerns and the low mass ratio of active material in the electrode need to be addressed. Herein, this review summarizes the up-to-date development in RP materials, outlines the challenges, and presents corresponding countermeasures aimed to enhance the electrochemical performance. It covers aspects such as the structural design of RP, the choice of the additive materials and electrolytes, rational electrode construction, etc. The review also discusses the future prospects of RP for LIBs/SIBs and aims to provide a different perspective on the challenges that must be overcome to fully exploit the potential of RP and meet commercial application requirements.

To meet the demands of high-voltage lithium-ion batteries (LIBs), we develop a novel electrolyte through theoretical calculations and electrochemical characterization. Triphenylphosphine oxide (TPPO) is introduced as a film-forming additive into a sulfone-based electrolyte containing 1 mol L⁻¹ lithium difluoro(oxalate)borate. Density functional theory calculations show that TPPO has a lower reduction potential than the sulfone-based solvent. Hence, TPPO should be oxidized before the sulfone-based solvent and form a cathode electrolyte interphase layer on the Li-rich cathode. Our research findings demonstrate that adding 2 wt% TPPO to the sulfone-based electrolyte considerably enhances the ionic conductivity within a range of 20–60 ℃. In addition, it increases the discharge capacity of LIBs in a range of 2–4.8 V while maintaining excellent rate performance and cycling stability. Flammability tests and thermal gravimetric analysis results indicate excellent nonflammability and thermal stability of the electrolyte.

In view of the drawbacks of rechargeable batteries, such as low mass and volumetric energy densities, as well as slow charging rate, proton exchange membrane fuel cells (PEMFCs) are reckoned to be promising alternative devices for energy conversion. Currently, commercial PEMFCs mainly use H₂ as the fuel, but the challenges in generation, storage, and handling of H₂ limit their further development. Among the liquid fuels, formic acid possesses the merits of low flammability, low toxicity, slow crossover rate, faster reaction kinetics, and high volumetric H₂ storage capacity, thus being considered as the most promising energy carrier. It can be used as the energy source for direct formic acid fuel cells (DFAFCs) and formic acid-based H₂-PEMFCs, which are also called indirect formic acid fuel cells (IFAFCs). A common issue hindering their commercialization is lacking efficient electrocatalysts. In DFAFCs, the anodic electrocatalysts for formic acid oxidation are suffering from stability issue, whereas the cathodic electrocatalysts for oxygen reduction are prone to poisoning by the permeated formic acid. As for IFAFCs, CO and CO₂ impurities generated from formic acid dehydrogenation will cause rapid decay in the catalytic activity. High working temperature can improve the CO and CO₂ tolerance of catalysts but will accelerate catalyst degradation. This review will discuss the mitigation strategies and recent advances from the aspect of electrocatalysts to overcome the above challenges. Finally, some perspectives and future research directions to develop more efficient electrocatalysts will be provided for this promising field.

Sodium superionic conductor (NASICON) is a class of compounds with robust polyanionic frameworks and high thermal stability, which are regarded as prospective cathodes candidates for secondary batteries. However, NASICON cathodes typically have low discharge plateaus and low practical capacities in aqueous electrolytes. Here, Na₃V_1.75Fe_0.25(PO₄)₂F₃ is investigated as a cathode material for the aqueous zinc/sodium batteries. While the addition of F helps with the improvement of NASICON structural stability, the low-cost Fe substitution has a positive impact on the capacity increment, reaction voltage increases, and cycling stability improvement. Because the Fe³⁺ substitution could induce a change in the spin magnetic moments of the 3d orbitals of the VO₄F₂ and FeO₄F₂ octahedra, the 2-electron reaction of V is activated, which are V⁴⁺/V³⁺ and V⁵⁺/V⁴⁺ redox couples. As a result, the novel Na₃V_1.75Fe_0.25(PO₄)₂F₃ cathode delivers a high operating voltage of 1.7 V, a high energy density of 209 W·h·kg⁻¹ and stable lifespan (83.5% capacity retention after 6,000 cycles at 1 A·g⁻¹) in the aqueous zinc/sodium batteries. This research demonstrates the practicality of activating multielectron reactions to optimize the electrochemical properties of NASICON cathodes for aqueous secondary batteries.

The continuous development of the global energy structure transformation has put forward higher demands upon the development of batteries. The improvements of the energy density have become one of the important indicators and hot topic for novel secondary batteries. The energy density of existing lithium-ion battery has encountered a bottleneck due to the limitations of material and systems. Herein, this paper introduces the concept and development of multi-electron reaction materials over the past twenty years. Guided by the multi-electron reaction, light weight electrode and multi-ion effect, current development strategies and future trends of high-energy-density batteries are highlighted from the perspective of materials and structure system innovation. Typical cathode and anode materials with the multi-electron reactions are summarized from cation-redox to anion-redox, from intercalation-type to alloying-type, and from liquid systems to solid-state lithium batteries. The properties of the typical materials and their engineering prospects are comprehensively discussed, and additionally, the application potential and the main challenges currently encountered by solid-state batteries are also introduced. Finally, this paper gives a comprehensive outlook on the development of high-energy-density batteries.