The zinc-ion battery (ZIB) is a 2 century-old technology but has recently attracted renewed interest owing to the possibility of switching from primary to rechargeable ZIBs. Nowadays, ZIBs employing a mild aqueous electrolyte are considered one of the most promising candidates for emerging energy storage systems (ESS) and portable electronics applications due to their environmental friendliness, safety, low cost, and acceptable energy density. However, there are many drawbacks associated with these batteries that have not yet been resolved. In this Review, we present the challenges and recent developments related to rechargeable ZIB research. Recent research trends and directions on electrode materials that can store Zn 2+ and electrolytes that can improve the battery performance are comprehensively discussed.

The main obstacles that hinder the development of efficient lithium sulfur (Li-S) batteries are the polysulfide shuttling effect in sulfur cathode and the uncontrollable growth of dendritic Li in the anode. An all-purpose flexible electrode that can be used both in sulfur cathode and Li metal anode is reported, and its application in wearable and portable storage electronic devices is demonstrated. The flexible electrode consists of a bimetallic CoNi nanoparticle-embedded porous conductive scaffold with multiple Co/Ni-N active sites (CoNi@PNCFs). Both experimental and theoretical analysis show that, when used as the cathode, the CoNi and Co/Ni-N active sites implanted on the porous CoNi@PNCFs significantly promote chemical immobilization toward soluble lithium polysulfides and their rapid conversion into insoluble Li 2 S, and therefore effectively mitigates the polysulfide shuttling effect. Additionally, a 3D matrix constructed with porous carbonous skeleton and multiple active centers successfully induces homogenous Li growth, realizing a dendrite-free Li metal anode. A Li-S battery assembled with S/CoNi@PNCFs cathode and Li/CoNi@PNCFs anode exhibits a high reversible specific capacity of 785 mAh g −1 and long cycle performance at 5 C (capacity fading rate of 0.016% over 1500 cycles).

Lithium sulfur (Li-S) batteries offer higher theoretical specific capacity, lower cost and enhanced safety compared to current Li-ion battery technology. However, the multiple reactions and phase changes in the sulfur conversion cathode result in highly complex phenomena that significantly impact cycling life. For the first time to the authors’ knowledge, a multi-scale 3D in-situ tomography approach is used to characterize morphological parameters and track microstructural evolution of the sulfur cathode across multiple charge cycles. Here we show the uneven distribution of the sulfur phase fraction within the electrode thickness as a function of charge cycles, suggesting significant mass transport limitations within thick-film sulfur cathodes. Furthermore, we report a shift towards larger particle sizes and a decrease in volume specific surface area with cycling, suggesting sulfur agglomeration. Finally, we demonstrate the nano-scopic length-scale required for the features of the carbon binder domain to become discernible, confirming the need for future work on in-situ nano-tomography. We anticipate that X-ray tomography will be a powerful tool for optimization of electrode structures for Li-S batteries.

SIBs), for which the reaction chemistries are similar to those of LIBs. [4][5][6][7][8] To reach similar energy densities as LIBs, promising cathode materials for SIBs must possess high capacity to compensate for their intrinsically low operation voltages. As the capacities of cathode materials can reach their limit when using transition metal redox, it is anticipated that redox of oxygen in the crystal structure can contribute additional capacity and boost the resulting energy density. [9,10] Representative works were performed in the early 2000s, specifically, on Li 2 MnO 3 (Li[Li 1/3 Mn 2/3 ]O 2 ) layered material, [11,12] which has the same crystal structure as typical LiTMO 2 (TM = transition metal). Li 2 MnO 3 is electrochemically inactive because Mn 4+ /Mn 5+ redox is not available within the normal cutoff voltage window. However, the material delivered a capacity beyond the theoretical limit attributed to the transition metal redox (300 mAh g −1 ). [12] Earlier works suggested that the delivered capacity could be attributed to oxygen loss from the oxide lattice; [12] however, state-of-the-art characterization later proved that the main contributor to the capacity was associated with the oxygen redox, [13] which triggered the intensive study of oxygen redox. Recently, there are some arguments to verify the chemical state of lattice oxygen during electrochemical reaction. Earlier work by Tarascon et al. [9] demonstrated the oxygen activity using X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and electron paramagnetic resonance (EPR) in Li 2 Ru 1-y Sn y O 3 compound. In situ or operando Raman spectroscopy and surface-enhanced Raman spectroscopy (SERS) become important tools in identifying the formation of peroxolike species (O 2 n− ). [14,15] Yang and Devereaux [16] highlighted the importance of using resonant inelastic X-ray scattering (RIXS) to identify the activity of lattice oxygen in oxide materials. From the above facts, it is considered that combination of the above-mentioned characterization tools with theoretical thermodynamic prediction may provide more reliable results to understand the oxygen redox chemistry.The oxygen redox reaction has also been extensively investigated in SIBs to achieve additional capacity. [17][18][19] For SIBs, Na 2 MnO 3 (Na[Na 1/3 Mn 2/3 ]O 2 ), which has the same crystal structure as Li 2 MnO 3 , has also been considered despite the large difference in the ionic size between sodium and manganese. For Recently, anionic-redox-based materials have shown promising electrochemical performance as cathode materials for sodium-ion batteries. However, one of the limiting factors in the development of oxygen-redoxbased electrodes is their low operating voltage. In this study, the operating voltage of oxygen-redox-based electrodes is raised by incorporating nickel into P2-type Na 2/3 [Zn 0.3 Mn 0.7 ]O 2 in such a way that the zinc is partially substituted by nickel. As designed, the resulting P2-type Na 2/3 [(Ni 0.5 Zn 0.5 ) 0.3 Mn 0.7 ]O 2 electrode ...