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The theoretically high energy densities and wide availability of active materials have led to great interest in the development of magnesium‑sulfur (MgS) batteries. However, poor electronic conductivity of sulfur, active material dissolution, polysulfide shuttling, and poor cycling stability are major challenges that need to be tackled. Herein we observed the pristine MgS cell faces significant overcharging issues and cell failure is common within 30 cycles with significant capacity decay. With the help of XRD and elemental mapping realized that the dissolved liquid polysulfides are metastable in nature. Due to the high sulfophilic nature of the separator, polysulfide absorption leads to slow crystal growth inside the separator. This active material trapping might be the reason for quick capacity decay. We attempted to revive the dissolved polysulfides by introducing conductive nitrogen-doped graphene (N-gpn)@Carbon cloth(CC) interlayer between the electrodes and separator. This interlayer has a high polysulfide absorption nature, which allows the battery to demonstrate an initial capacity of 1075 mAh g−1and increased cycling stability to 100 cycles. However, this stability was further enhanced to 300 cycles by protecting the anode. Theoretical considerations suggest that among all polysulfides, MgS8, has the strongest interaction with N-gpn and can be trapped most favorably in a defective N-gpn. This leads to enhanced utilization of the active material and improved cycling stability.

The constant search for cost-effective and high-performance materials for Li-ion batteries (LIBs) has increased with time. Here, we synthesized low-cost multi-heteroatom co-doped carbon from biowaste bagasse [N, S, and O co-doped carbon (NSOC-10)]. We also investigated the influence of heteroatom doping in the carbon matrix and its effect on the electrochemical properties when used in Li-ion and Li–S batteries. Interestingly, the NSOC-10 sample shows a capacity of 574 mAh g–1even after 1000 cycles, which is much higher than the theoretical capacity of a traditional graphite anode (372 mAh g–1), while undoped carbon degrades quickly (pristine bagasse) and displays only 26.6% capacity retention within 250 cycles. The excellent capacity retention of NSOC-10 could be attributed to a highly porous carbon matrix that tends to increase Li+percolation, shorten the Li+diffusion path, and boost the lithium-ion storage capability. Further, we studied the use of the heteroatom-doped NSOC-10 carbon matrix as a carbon host for the sulfur cathode in a Li–S battery. Indeed, the Li–S cell showed an initial capacity of 1200 mAh g–1with a capacity retention of 79% by the end of 250 cycles and maintained high coulombic efficiency of >99%. This is attributed to the heteroatom (N, S, and O) doping in the activated carbon scaffold that resulted in better electrode wettability, high Li+diffusion rate, and good electron conductivity of the carbon matrix, and this polar carbon adsorbs polar polysulfides through polar–polar interactions and maintains its capacity. Hence, the designed cost-effective co-doped NSOC-10 was identified to be a promising candidate as an anode material in LIBs and also as a potential sulfur host in Li–S batteries.

In the loop of numerous challenges and ambiguities, Li–O2batteries are crawling to reach their commercialization phase. To achieve the progressive milestones, along with the developments in the architecture of cathodes, anodes, and electrolytes, understanding its failure mode is equally important. Under an unrestricted charge–discharge protocol, cyclability of nonaqueous Li–O2batteries are limited to only a few cycles. This report examines an additive-free ether-based Li–O2battery in the perspective of identifying the origin of possible side reactions and their affiliations to integral components of the battery. Structural and compositional changes during every charge–discharge sequence are studied using bottom-up sequential tear-down analysis. The substantial increase in impedance and corresponding decrease in capacities after every cycle are interrelated to the amount of electrode passivation resulting from the discharge products and electrolyte decomposition. From the tear-down analysis, it is approximated that, among the total capacity loss, ≈55% is attributed to the cathode, ≈28% of the loss corresponds to the anode, and ≈17% is attributed to the electrolyte, given that battery failure instigates from the “reactive oxygen species”. Electrochemically formed Li2O2via the superoxide pathway induces large decomposition overpotentials up to 4.6 V versus Li/Li+because of its overrated reactivity with electrolytes and carbon supports. On the contrary, efficient decomposition of chemically formed Li2O2below 3.9 V proves that the extra charge potential observed for electrochemically formed Li2O2is in fact consumed for the decomposition of irreversibly formed side products via the superoxide pathway. Spontaneous reactivity of Li2O2and trivial reactivity of Li2O highlight the need of advanced strategies to maneuver oxygen red-ox in selective pathways that unalter the electrolyte and electrodes, and the necessity of their synchronized performance for the evolution of practical Li–O2batteries.

Energy storage in a rechargeable chloride ion battery by tungsten oxytetrachloride cathode material. This class of material is used, as an electrode for the first time in batteries, and paves way for the employment of abundant chloride‐based materials, for energy storage applications. More details can be found in article number 2200193, Guruprakash Karkera, Maximilian Fichtner and co‐workers.

Rechargeable chloride‐ion batteries (CIBs) are a new emerging battery technology that can potentially provide high theoretical volumetric capacities at lower cost and higher abundance. However, research on CIBs is in its early stages, and the current challenge lies in finding suitable electrodes and electrolytes. Herein, tungsten oxychloride is introduced for the first time as a cathode candidate for use in CIB. WOCl4enables the reversible transfer of nearly one Cl−per formula unit during electrochemical cycling, corresponding to an initial discharge capacity of 120 mAh g−1. A reversible capacity of 90 mAh g−1(75%) is retained after 50 cycles. Postmortem analysis of cycled electrodes by X‐ray diffraction, X‐ray photoelectron spectroscopy, and Raman spectroscopy reveals the reversible chloride‐ion transfer between the electrodes through a conversion mechanism. This work paves the way for the use of tungsten chloride‐based electrode materials for battery applications. A novel chloride‐ion battery containing tungsten oxytetrachloride as a new cathode material, lithium metal as anode, and 3 M Pyr14Cl in EC:PC (1:1) as the electrolyte is presented. WOCl4displays a reversible chloride‐ion transfer, corresponding to an initial capacity of 120 and 90 mAh g−1after 50 cycles.

Calcium (Ca) batteries represent an attractive option for electrochemical energy storage due to physicochemical and economic reasons. The standard reduction potential of Ca (−2.87 V) is close to Li and promises a wide voltage window for Ca full batteries, while the high abundance of Ca in the earth’s crust implicates low material costs. However, the development of Ca batteries is currently hindered by technical issues such as the lack of compatible electrolytes for reversible Ca2+plating/stripping and high-capacity cathodes with fast kinetics. Herein, we employed FeS2as a conversion cathode material and combined it with a Li+/Ca2+hybrid electrolyte for Ca batteries. We demonstrate that Li+ions ensured reversible Ca2+plating/stripping on the Ca metal anode with a small overpotential. At the same time, they enable the conversion of FeS2, offering high discharge capacity. As a result, the Ca/FeS2cell demonstrated an excellent long-term cycling performance with a high discharge capacity of 303 mAh g–1over 200 cycles. Even though the practical application of such an approach is questionable due to the high quantity of electrolytes, we believe that our scientific findings still provide new directions for studying Ca batteries with long-term cycling.