ABSTRACT The surface modification of zinc anodes and the development of effective cathode dual‐functional oxygen electrocatalysts remain of paramount interest for enhancing the cycle life of rechargeable zinc‐air batteries. The present work provides a sustainable synthesis of CoNi‐based composites that can be used as cathode and anode side catalysts in Zn‐air batteries. CoNi‐metals with hybrid‐metal organic frameworks (Hybrid‐MOFs) and MOF‐derived composites from curcumin‐melamine (C‐M) and benzene‐1,3,5‐tricarboxylic acid (BTC) were created for cathode and anode composites using reflux and hydrothermal techniques. In this instance, the cathode composite can be referred to as CoNi‐N‐C after annealing, whereas the anode composite can be referred to as CoNi‐BTC without annealing. Thereafter, the formation of CoNi‐N‐C and CoNi‐BTC composites was confirmed by microscopic, X‐ray photoelectron, and X‐ray diffraction techniques. As a result, structurally tailored CoNi‐N‐C and CoNi‐BTC composites perform efficiently in electrochemical processes such as oxygen evolution/reduction reactions (OER/ORR) and energy conversion devices (Zn‐air battery). Primarily, the CoNi‐N‐C catalyst exhibits the lowest overpotential (E i = 10 = 1.48 V) and better half‐wave potential (E 1/2 = 0.781 V) in OER/ORR reactions; secondary CoNi‐BTC composites coated on the Zn anode have the highest specific capacity (756.3 mA h g zn −1 ) and 1000‐cycle charge–discharge stability in Zn‐air batteries.

Potassium-ion batteries (KIBs) are emerging as promising alternatives to lithium-based systems owing to potassium abundance, its low redox potential, and the possibility of using graphite as a stable, low-cost anode. However, competitive KIB development still depends on overcoming electrolyte-related limitations, since electrolyte chemistry governs ion transport, electrode stability, interphase formation, safety, and long-term cell performance. Rather than offering a descriptive catalogue of reported systems, this Review establishes a critical, mechanism-driven framework to rationalize electrolyte behaviour in KIBs and guide future design.Aqueous, non-aqueous, highly concentrated, localized high-concentration, quasi-solid, solid-state, polymeric, and ionic-liquid electrolytes are analysed through a unified perspective linking K⁺ solvation, ion-pairing, desolvation, transport properties, electrochemical stability, and SEI/CEI formation. Recent advances are critically reinterpreted through emerging concepts such as desolvation engineering, dynamic solvation regulation, multifunctional interphase design, and molecular confinement, allowing the identification of structure–property relationships and actionable design rules that extend beyond individual electrolyte chemistries. By integrating molecular-scale interactions, interfacial chemistry, and cell-level validation, this Review highlights performance-limiting mechanisms and proposes strategies to decouple ionic transport, interphase stability, safety, and voltage window, thereby accelerating the development of high-energy, safe, and durable KIB technologies.

The threatening demerits of state-of-the-art lithium-ion batteries, which include poor safety, limited availability of lithium and the presence of expensive elements such as nickel and cobalt, have accelerated extensive research to find alternatives beyond lithium-ion batteries. In the past two decades, lithium-sulfur batteries have been extensively researched, and they have entered a key stage of commercialization. However, critical issues such as self-discharge and lithium polysulfide shuttling, which are intrinsic properties of electrolytes, must be overcome. This mini review comprehensively illustrates the underpinning issues of lithium-sulfur batteries, particularly those related to electrolytes, and the strategies employed to overcome these challenges based on the articles published after 2020.

The focus of this study is to investigate capabilities of gamma lithium vanadium oxide (gamma-LiV2O5) to accommodate ions beyond Li+. The gamma-LiV2O5 has been tested electrochemically as a potential candidate for novel aqueous rechargeable batteries based on multivalent ions, namely Mg2+, Ca2+ and Al3+. The gamma-LiV2O5 is prepared by a simple solid-state reaction and characterized by XRD, SEM, HRTEM, FTIR, Raman, and Impedance methods, before and after CV cycling. Li+ ions can take octahedral cationic sites in the oxide lattice, which leads to gamma H gamma ' reversible phase transition, but their subsequent occupation of tetrahedral sites incites irreversible gamma H zeta transition and capacity fade during extended cycling in LiNO3. In contrast, such irreversible behavior is not observed in Ca(NO3)2 and Mg(NO3)2, where initial repeated cycling, including negative potentials, causes the CV growth. Although Ca2+ and Mg2+ ions weekly intercalate into the structure, as indicated by BVS analysis, the proton coinsertion, during early cycling stage activates the surface, causing large platelets to crumble and boosting pseudocapacitive-type redox behavior. This results in a high specific capacity in bivalent electrolytes, especially in Ca(NO3)2, which amounts to 128 mAh g-1 at 1 A g-1. Although the agglomeration of reduced particles leads to a decline in capacity over extended cycling, the capacity remains high after 150 cycles, reaching 74 mAh g-1. In LiNO3, the identification of gamma' phase after long cycling within the stable potential window, together with agglomerated microplatelets (which are not crushed during initial Li+, thus limiting capacity to approximate to 27 mA hg-1) is linked to the capacity fade. Furthermore, when cycled in Al3+ electrolyte, the material degrades quickly due to the dissolution process at the beginning of cycling. Therefore, the Ca2+ electrolyte is identified as the most promising for the development of rechargeable aqueous batteries with gamma phase V2O5 cathode.

Although silicon-based anodes have been identified as a potential alternative to conventional graphite anodes, the huge volume change (approximately 300%) that occurs in silicon while cycling still impedes this system from practical applications. In the case of silicon-suboxide (SiOx)-based anode materials, both Li2O and LiSiO4 are formed during the initial lithiation processes and act as a natural volume buffer matrix to accommodate volume changes and the formation of a stable SEI layer, which improves the cyclability and capacity retention. In this study, a series of SiOx/Si/C-based electrodes composed of different amorphous SiOx, Si, and graphitic carbon contents were prepared. Among the various investigated compositions, the electrode with a ratio of SiOx-Si-C equal to 70:12.5:12.5 was found to be optimal in terms of discharge capacity. This promising electrode was pre-lithiated prior to cycling. Finally, 2032-type lithium-sulfur (Li-S) coin cells composed of a S-C/SiOx-Si-C (pre-lithiated) configuration were assembled and their cycling performances are reported.

Although lithium-ion batteries (LIBs) have found an unprecedented place among portable electronic devices owing to their attractive properties such as high energy density, single cell voltage, long shelf-life, etc., their application in electric vehicles still requires further improvements in terms of power density, better safety, and fast-charging ability (i.e., 15 min charging) for long driving range. The challenges of fast charging of LIBs have limitations such as low lithium-ion transport in the bulk and solid electrode/electrolyte interfaces, which are mainly influenced by the ionic conductivity of the electrolyte. Therefore, electrolyte engineering plays a key role in enhancing the fast-charging capability of LIBs. Here, we synthesize a novel propionic acid-based viologen that contains a 4,4 '-bipyridinium unit and a terminal carboxylic acid group with positive charges that confine PF6- anions and accelerate the migration of lithium ions due to electrostatic repulsion, thus increasing the overall rate capability. The LiFePO4/Li cells with 0.25% of viologen added to the electrolyte show a discharge capacity of 110 mAh g-1 at 6C with 95% of capacity retention even after 500 cycles. The added viologen not only enhances the electrochemical properties, but also significantly reduces the self-extinguishing time.

Utilizing affordable bifunctional catalysts per strong ORR/OER (oxygen reduction and evolution reactions) ability and superior zinc-air battery performance is yet difficult due to the diverse mechanisms of ORR/OER. This work uses CoNi-MOF (metal-organic framework) as a self-template to yield the CrS doped CoNi/C bifunctional catalyst. Comparable to Pt/C and IrO2 commercial catalysts, the CrS@CoNi/C catalyst exhibits improved electrocatalytic activity toward OER and ORR due to its linked pellet architecture and intact metal sulfide@carbon structure. The CrS@CoNi/C catalyst has the most intriguing ORR/OER performance, with a significantly lower potential and an exceptionally extended cycle duration (E1/2 = 0.72 V and eta 10 = 260 mV). The CrS@CoNi/C-based aqueous zinc-air battery shows long-term charge-discharge stability (more than 100h/600 cycles) together with significant specific capacity (789.7 mAh g-1Zn) and power density (132.2 mW cm-2). Most significantly, after charge-discharge stability, the recharged CrS@CoNi/C-based alkaline zinc-air battery has been employed to exhibit less structural deformation for the cathode and more zincate ion production for the anode side electrodes, which is employed through TEM analysis.

The state-of-the-art lithium-ion batteries (LIBs) with graphitic anode and lithium transition metal oxide cathode activated by a nonaqueous liquid electrolyte are unable to achieve fast-charging ability without adversely affecting the electrochemical performance and safety issues. The realization of extremely fast charging with a goal of 15 min recharging time is expected to accelerate the adoption of lithium-ion batteries in electric vehicles. Nevertheless, the utilization of such a goal requires further research and development with advanced materials at multiple levels. Reformulation of nonaqueous liquid electrolytes has been identified as an effective strategy to conquer these challenges. Herein, lithium difluoro oxalaborate (LiDFOB) and bis(2,2,2-trifluoroethyl) ether (BTFE) were added as electrolyte additives in the routinely employed electrolytes, and their charge-discharge performances were evaluated with the LiFePO4 cathode at different C rates. Further, the experimental results are correlated to the LUMO and HOMO values. The cathode/electrolyte interfacial properties were investigated by XPS and FT-IR. Results confirmed that the incorporation of electrolyte additives not only facilitated the formation of a robust and stable cathode/electrolyte interface but also appreciably minimized the self-extinguishing time and corrosion of the aluminum current collector.

Preparation of in-situ composites with carbon by pyrolysis of an organic precursor is an effective strategy to improve performances of insulating and semiconducting cathode materials. However, due to the property of organic precursor to act as a strong reductive agent during carbonization process, the in-situ synthesis of LiV 2 O 5 / C composite cathode material is delicate and presents a challenge for researchers, since vanadium in LiV 2 O 5 coexists in two oxidation states, V 4 + and V 5 + . In our research, we utilized an adopted conventional solid state method for the in-situ preparation of Li x V 2 O 5 /C composite ( x approximate to 0.86). By using methylcellulose polymer as a carbon source, Li x V 2 O 5 /C was synthesized via two-step solid state reaction at elevated temperatures. Li x V 2 O 5 crystallized as gamma polymorph phase, and the amount of in-situ formed carbon does not exceed 3wt%. The electrochemical characteristics of the as-prepared Li x V 2 O 5 /C were investigated in aqueous and non-aqueous electrolyte via cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) tests and electrochemical impedance spectroscopy (EIS). On lithium insertion/removal, the Li x V 2 O 5 /C composite exhibits stable cycling performance and achieves significant storage capacity enhancement when compared to pristine Li x V 2 O 5 obtained under similar conditions. Under current densities of 0.1, 0.2, 0.3 and 1 A/g, the specific capacity enhancement is around 112, 91, 80 and 62 %, respectively. Replacing the organic electrolyte with the aqueous one has a negligible effect on the mechanism and efficiency of lithium intercalation within the Li x V 2 O 5 /C, which opens up the possibility of using this material in aqueous as well as in organic-electrolyte batteries. The decay of cathode's activity evidenced during electrochemical exchange of lithium with sodium in aqueous environment comes as a result of the formation of electrochemically inactive 8-Na x V 2 O 5 .

Silicon (Si) -based materials have been identified as a potential alternative anode owing to their superior theoretical capacity compared to conventional graphitic carbon. Nevertheless, the huge volume change (approximately 300%) that occurs while cycling still hampers this system from 100% practical applications. Silicon-monoxide (SiOx)-based anode materials, on the other hand, are being explored extensively due to their unique properties such as high theoretical capacity, formation of Li2O and LiSiO4 during initial lithiation process that act as a natural volume buffer matrix to accommodate volume changes and formation of a stable solid electrolyte interphase layer, which improves the cyclability and capacity retention. Although poly (vinylidene fluoride) (PVdF) is widely used as a binder, the weak van der Waals forces between PVdF and silicon-based particles fail to bind particles effectively, when substantial volume change occurs. Herein, we prepare a series of SiOx-Si-C electrodes with different binders poly (acrylic acid) (PAA), carboxyl methyl cellulose (CMC) and their blends as binder. The prepared polymeric blends are subjected to thermal, morphological, mechanical and physico-chemical analyses. The Li/ SiOx-Si-C cell assembled with 100% PAA as binder delivered a discharge capacity of 1908 mAh g−1 on its first cycle and 724 mAh g−1 on its 100th cycle with a fade in capacity of 11.8 mAh g−1 per cycle. Upon the incorporation of CMC in the PAA blend the cycling performance was found to be poor. Among the various investigated compositions, the electrode with sole poly (acrylic acid) as a binder offers the highest discharge capacity and this is attributed to the high concentration of the functional (carboxylic) group which forms strong hydrogen bonds with - OH groups on the SiOx or carbon surface. The interfacial properties of the polymeric binders are thoroughly investigated by spectroscopies and electrochemical tests. Graphical abstract

Silicon oxide and its derivatives (SiO x , 0 < x < 2) are drawing significant interest as electrode material for Li-ion and Li–S batteries owing to their unique properties of high specific capacity, low working potential, high abundance, and environmental friendliness. In-depth research is done on the effects of electrolyte additives on the electrochemical and interfacial characteristics of SiO x -based anodes for Li–S batteries. Two different electrolyte additives namely lithium bis (fluorosulfonyl imide) (LiFSI) and lithium bis (oxalatoborate) (LiBOB) were incorporated in the supporting electrolyte containing 1 M lithium bis (trifluoromethanesulfonyl imide) (LiTFSI) in tetraethylene glycol dimethyl ether (TEGDME): 1,3 dioxolane (DOL) in the ratio of 1:1 (v/v). The Li/SiO x –Si–C 2032-type half-cells were assembled, and their charge–discharge properties were explored at 0.1 C-rate. Surface morphology and electrochemical impedance investigations of the electrode materials have been performed after cycling. The interfacial properties of SiO x -based electrodes were examined by FTIR and XPS. Among the electrolytes studied LiFSI-added electrolytes offer superior charge–discharge properties, which was attributed to the formation of a stable solid electrolyte interphase (SEI) layer on the electrode surface. The surface chemistry studies revealed the formation of Li 2 CO 3 and ROCO 2 Li peaks on the lithium metal surface. The formation of Li 2 CO 3 and ROCO 2 Li compounds are identified on lithium surface by XPS data and complemented by NMR analysis.

Hybrid solid polymer electrolytes (HSPE) comprising poly(ethyleneoxide) (PEO), LiTFSI, barium titanate (BaTiO3), and viologenare prepared by a facile hot press. The physical properties of theHSPE membranes are studied by using small-angle and wide-angle X-rayscattering, thermogravimetric analysis, differential scanning calorimetry,and tensile strength. The prepared hybrid solid polymer electrolytesare also investigated by means of ionic conductivity and transportnumber measurements. The employed analyses collectively reveal thateach additive in the PEO host contributes to a specific property:LiTFSI is essential in providing ionic species, while BaTiO3 and viologen enhance the thermal stability, ionic conductivity,and transport number. The enhanced value in the Li+-transportnumber of HSPE are presumably attributed to the electrostatic attractionof TFSI anions and the positive charges of viologen. Synergistically,the added BaTiO3 and viologen improve the electrochemicalproperties of HSPE for the applications in all-solid-state-lithiumpolymer batteries.

The performance of lithium batteries is mainly determined by the microstructure of cathode, electrolyte, anode materials, and the solid electrode/electrolyte interfaces. The further advancement in batteries requires an in-depth understanding of the complex chemical reactions, phase transformations, and charge transfer. X-ray diffraction study is a powerful tool for directly visualizing these complex processes at different scales, providing information on the structural evolution, redox mechanism, solid-electrolyte interphase (SEI) formation, and Li-ion transport properties during the charge-discharge process. Beyond lithium-ion, systems such as lithium-air/O2, lithium-sulfur, and sodium-ion batteries are considered as potential alternatives to the state-of-the-lithium-ion batteries. The recent advancements in the characterization of sodium-ion and lithium-sulfur battery systems have also been discussed. Finally, the remained challenges and perspectives in the characterization of battery materials are also presented.

Although lithium-sulfur (Li-S) batteries are expected to replace lithium-ion batteries due to their high theoretical capacity, low cost, and environmental friendliness, the poor electronic conductivity of sulfur, shuttling of lithium polysulfide (LiPS) between the electrodes, and tendency to self-discharge have delayed attempts to commercialize the technology. Introduction of a permselective and functionalized membrane has been recognized as a potential strategy to mitigate LiPS shuttling. Earlier reports found that biphenyl groups form a passive layer that improves the performance of Li-S batteries and that Pd(PPh3)(4) can serve as an efficient catalyst for the conversion of LiPS. In this study, a porous organic polymer comprising both biphenyls and Pd(PPh3)(4) interconnected via a Friedel-Crafts alkylation reaction (BP-POP) was synthesized and coated onto a commercially available porous Celgard 2320 membrane, and its electrochemical performance was investigated. For comparison purposes, a phenyl derivative (instead of biphenyl), MP-POP, was also synthesized and evaluated. The introduced membrane not only blocked the shuttling of LiPS and prevented self-discharge but also accelerated the catalytic conversion of LiPS. The superior performance of the BP-POP-coated membrane compared with the MP-POP-coated and uncoated Celgard 2320 membranes can be attributed to the synergistic effects of the catalytic activities of the biphenyl group and Pd(PPh3)(4).

The influence of electrolyte additives on the electrochemical and interfacial properties of SiOx-based anodes for lithium-sulfur batteries (Li-S) was systematically investigated. Four different electrolyte additives, namely, lithium nitrate, vinylene carbonate (VC), vinyl ethylene carbonate, and fluoroethylene carbonate (FEC), were added to the bare electrolyte comprising 1 M LiTFSI in tetraethylene glycol dimethyl ether/1,3 dioxolane in a ratio of 1:1 (v/v). The self-extinguishing time (SET) of the liquid electrolytes was measured. The 2032-type half-cells composed of Li/SiOx/Si/C were assembled, and their charge -discharge studies were analyzed at the 0.1 C-rate. Upon cycling, the electrode materials were subjected to surface morphology and differential scanning calorimetry analyses. The interfacial properties of SiOx-based electrodes were investigated by electrochemical impedance spectroscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy studies. Among the electrolytes examined, FEC-added electrolytes offered the lowest SET and interfacial resistance values. The superior charge-discharge properties of FEC-added electrolytes were attributed to the formation of a stable solid electrolyte interface layer on the electrode surface. The surface chemistry studies revealed the formation of Li2CO3 and ROCO2Li peaks on the electrode surface.

Sodium-ion batteries (SIBs) are promising alternatives to lithium-based energy storage devices for large-scale applications, but conventional lithium-ion battery anode materials do not provide adequate reversible Na-ion storage. In contrast, conversion-based transition metal sulfides have high theoretical capacities and are suitable anode materials for SIBs. Iron sulfide (FeS) is environmentally benign and inexpensive but suffers from low conductivity and sluggish Na-ion diffusion kinetics. In addition, significant volume changes during the sodiation of FeS destroy the electrode structure and shorten the cycle life. Herein, we report the rational design of the FeS/carbon composite, specifically FeS encapsulated within a hierarchically ordered mesoporous carbon prepared via nanocasting using a SBA-15 template with stable cycle life. We evaluated the Na-ion storage properties and found that the parallel 2D mesoporous channels in the resultant FeS/carbon composite enhanced the conductivity, buffered the volume changes, and prevented unwanted side reactions. Further, high-rate Na-ion storage (363.4 mAh g−1 after 500 cycles at 2 A g−1, 132.5 mAh g−1 at 20 A g−1) was achieved, better than that of the bare FeS electrode, indicating the benefit of structural confinement for rapid ion transfer, and demonstrating the excellent electrochemical performance of this anode material at high rates.

The Li-S battery commercialization has been hampered owing to challenging problems such as poor conductivity of elemental sulfur, volume change upon cycling, and shuttling of lithium polysulfide between the electrodes. To conquer these issues, a sensible electrode structure design is crucial. The incorporation of carbonaceous materials and metal oxides has been identified as an effective tool to foster the electrochemical properties of Li-S batteries. In this work, to confine polysulfide shuttling and to improve the conductivity of sulfur, MnFe2O4-seated rGO-sulfur composite was prepared and used as a cathode. The lithium-sulfur cell with MnFe2O4-seated rGO-sulfur composite cathode showed outstanding electrochemical performance delivering a discharge capacity of 1300 mAh g(-1) at 0.1 C-rate on its first cycle and a stable cycling was attained at 0.5 C-rate. In the composite cathode, each component functions for a specific reason: the rGO in the composite improves the conductivity of sulfur, while added- MnFe2O4 not only confines polysulfides appreciably but also provides integrity to the cathode as evidenced by SEM analysis. The self-discharge studies showed that the Li-S cell with MnFe2O4 was capable of retaining its charge even after 90 h which has overhead the earlier reports. The Li-S system with MnFe2O4 -laden cathode material exhibited better electrochemical properties than the un-laden one.

This review analyses the role of viologens, a unique class of redox-active molecules in various energy storage devices and the nature of chemical interactions in enhancing their overall performances.