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.

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.

It is of great significance to design and innovate electrode materials with unique structures to effectively optimize the electrochemical properties of the secondary battery. Herein, inspired by neuron networks, an ingenious synthesis is proposed to fabricate NiSe with multidimensional micro-nano structures, followed by in situ construction of NiSe/NiO heterostructures via a temporary calcination. The major structure of bulk NiSe synthesized by the solvothermal method is 3-dimensional micron cluster spherical particles interwoven by uniform one-dimensional nanofibers. Such structures possess the synergistic advantages of nano and micro materials. After a temporary calcination in air, NiSe/NiO heterostructures should be formed in the bulk NiSe, which provides a built-in electric field to enhance diffusion kinetics of sodium ions. This special neural-like network and heterojunction structures ensure the excellent structural stability combined with rapid kinetics of the electrode, releasing 310.9 mAh g⁻¹ reversible capacity after 2,000 cycles at 10 A g⁻¹. Furthermore, the electrochemical storage and ion transport mechanisms are elaborated by electrochemical analysis and theoretical calculation in more detail.