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Layered sodium transition metal (TM) oxides exhibit great potential as high energy density cathode materials for sodium-ion batteries (SIBs). The large Na ions, nevertheless, adopts various coordination environments that are dependent of the sodium concentration, giving rise to cyclical gliding of TM layers and P-O phase transitions upon Na extraction/insertion process. The detrimental interlayer-gliding induced phase transformations lead to deteriorated round-trip energy efficiency, rate capability and cycling stability of electrodes. Herein, we demonstrate a shear-resistant interface via the supersaturation of lithium to overcome the interlayer-gliding behavior and inhibit the multiple P-O phase transitions in P2-type Na0.67Mn0.67Ni0.33O2. The results indicate that the nanoscale interface is composed of lithium-enriched O3 nanodomains in the P2 phase matrix, resulting in smooth charge/discharge profiles and superior cycling stability of P2-type Na0.67Mn0.67Ni0.33O2 cathode under a high cut-off voltage of 4.5V. This work highlights the concept of modulating the interfacial shear stress for improving the long-term cycling stability of high-voltage layered cathode materials that suffer from severe phase transformations.

Among various Zn-based batteries, transition metal compounds have been widely studied as cathode materials in alkaline electrolyte. However, the correlation between anion species and the electrochemical performance of corresponding compounds is still not well understood. Here, we construct a 3D-architecrured F doping Ni/Co hydroxides/oxides/phosphides (FNCA, A = H, O, P) as the model materials and deeply explore the effect of anion substitution on cathode material for Zn batteries. Electrochemical measurements are combined with theoretical calculations to reveal the mechanisms of FNCA delivering considerable dissimilarity in electrochemical properties. In-depth analysis suggests that the surface-dominated redox behaviors are greatly affected by the anion substitution, though the reversible capacity is just produced by the valence change of metal cations. The FNCP exhibits the highest capacity among three samples but an inferior cycling stability. As contrast, the FNCO shows a balanced characteristic of good capacity and superior cycling performance. Based on the understanding, we construct FNCA//Zn batteries. As expected, the FNCP//Zn batteries delivers the highest specific capacity of 318 mAh g−1 and a superior energy density of 532.7 Wh kg−1 at a power density of 1.673 kW kg−1, but an inferior cycling stability reserved from the individual FNCP electrode. This work provides a rational insight for deep understanding the behaviors that anions affect electrochemical energy storage but not participate in redox reactions, and offer more effective feasibility to design high capacity and durable cathode materials for aqueous Zn-based batteries.

Electrochemical energy storage systems with high energy/power density are a key technology for the development of intelligent society, especially for portable electronics devices and electric vehicles. The most effective strategy to enhance the energy/power density of batteries is to explore for high-capacity electrode materials. Layered cathode materials with high specific capacity and high operating voltage have attracted great research interests. However, severe surface structural degradation, irreversible oxygen release and interfacial side-reactions occurring in the cycles of layered materials at high voltage, cause undesirable capacity and voltage deterioration, blocking their further development. Interface engineering, in particular constructing stable heteroepitaxial interfaces on layered cathode materials, has been recognized as an effective strategy to solve these abovementioned problems comprehensively. Here, the development history and structural characteristics of layered cathode materials are reviewed, different types of heteroepitaxial interfaces and their construction methods are discussed in detail. Particularly, the mechanism and function of constructing heteroepitaxial interface in layered materials are emphasized. However, some essential issues still remain controversial, especially with regard to understanding of the surface structure and chemistry properties related to the material composition and synthesis process, and charge transfer and ionic transport of the interfacial processes of layered cathodes. A clear understanding of these fundamental mechanisms is therefore essential to optimize the synthesis process and electrochemical performance of layered cathodes.

Lithium-rich layered oxides (LLOs) are regarded as one of the most promising cathode materials for next generation Li-ion batteries (LIBs) due to their high energy density. However, the associated oxygen release and structure collapse resulting from the intrinsic anion and cation redox reactions lead to performance degradation, particularly the characteristic voltage fading which has prohibited the commercialization of LLOs for more than a decade. Herein, we have developed a dual-doping technique to overcome the longstanding structure and voltage instabilities of Co-free Li1.2Mn0.533Ni0.267O2, through the concurrent introduction of neodymium (Nd) and aluminum (Al) ions. Selective atomic substitution of Ni/Mn with Nd/Al ions and the preconstructed heteroepitaxial interface significantly enhance the voltage and capacity retention by regulating Ni ion activity and suppressing the phase transformation and Mn dissolution, thereby improving rate performance through tuning the electronic structure and promoting Li+ migration. The dual-doped material exhibits a superior cycling stability, with over 90% voltage retention and 82% capacity retention after 200 cycles, and excellent rate performance (150 mAh g−1 at 10 C).

Lithium-sulfur (Li-S) batteries are considered as a promising candidate of next generation lithium batteries by virtue of high theoretical energy density, low cost and eco-friendliness, yet their commercialization still suffers from undesirable polysulfide shuttling and uncontrollable Li dendrites growth. Herein, a dual-engineered separator is designed through double-side construction of ammonium alcohol polyvinyl phosphate/carbon black (AAPP/CB) constituted “polysulfide stockroom” and Li1.5Al0.5Ge1.5(PO4)3 (LAGP) based “ion guider” on a commercial polypropylene (PP) substrate. Such functional separator AAPP/CB@PP@LAGP enables highly robust, all-climate Li-S batteries, which is attributed to the efficient polysulfide-absorption/conversion function of the AAPP/CB layer and uniform Li ion distribution/transport capacity induced by the LAGP layer. It is anticipated that this work may provide a promising strategy for interface engineering of separators and promote the wide-temperature application of Li-S batteries.

Lithium and oxygen activities can have substantial influences on the kinetics of ion and electron transport and the structural integrity of Li-rich layered oxide (LLO) cathodes, since reversible oxygen redox is ascribed to the extra capacity beyond the theoretical capacity from transition metal redox at high voltages. Herein, we demonstrate a liquid-solid interfacial reaction to generate a heteroepitaxial interface with tunable Li/O activities on LLOs using molten boric acid. The experimental and theoretical analyses indicate that the atomic scale interface is comprised of a disordered rock salt structure containing substantial Li/O vacancies along the layered structure, associated with a segregation tendency of Ni and Co. The formation of this heteroepitaxial interface with Li/O vacancies improves the ionic/electronic conduction and electrochemical/structural stability, leading to a high discharge capacity of 283 mA h g-1 with initial Coulombic efficiency of 91.7% (0.1 C, 2.0–4.7 V vs. Li+/Li), excellent rate performance (246 and 159.7 mAh g-1 at 1 C and 10 C, respectively) and enhanced cyclic performance with a capacity retention of 92% after 100 cycles. The findings highlight the importance of a well-engineered interface for the design of high performance layered cathode materials for Li storage.

The constantly increasing demands on sustainable and high-performance energy storage devices generate tremendous research attentions on novel battery systems. Rechargeable magnesium battery (RMB), which possesses the advantages of low cost, natural abundance, has emerged as a considerable candidate. The fascinating features of high volumetric capacity, dendrites free and earth abundance also made it more fascinating. However, owing to the strong polarization of Mg ions, the existing electrodes and electrolyte cannot fully facilitate the Mg2+ ion insertion/extraction. In this regard, finding suitable electrode materials and electrolytes with high Mg insertion kinetics, excellent reversibility and costless are still the challenges that hinder the practical application of RMB. In this review, we mainly attempt to accumulate the recently advances in the development of electrodes, as well as development of advanced hybrid RMB systems. The review specifically aimed to provide new perspectives on the construction of novel electrode materials. Moreover, the challenges and perspective of RMBs are also discussed to highlight the limitations and the future direction. These may inspire more efforts on future work and accelerate the development process.