Microbial electrosynthesis (MES) is an emerging technology that enables the synthesis of value-added chemicals from carbon dioxide (CO2) or inorganic carbon compounds by coupling renewable electricity to microbial metabolism. However, MES still faces challenges in achieving high production of value-added chemicals due to the limited extracellular electron transfer efficiency at the biotic-abiotic interfaces. To overcome this bottleneck, it is crucial to develop novel cathodes and modified materials. This review systematically summarizes recent advancements in cathode materials in the field of electrocatalyst-assisted and photocatalyst-assisted MES. The effects of various material types are further investigated by comparing metal-free and metal materials and photocatalyst materials of different semiconductor types. Additionally, the review introduces the maximum production rate of value-added chemicals and conversion efficiency achieved by these cathode materials while highlighting the advantages and disadvantages of different material types. To the best of our knowledge, in electrocatalyst-assisted systems, the maximum CH4 yield on graphene aerogel/polypyrrole cathode achieved 1,672 mmol m-2 d-1, and the maximum Faraday efficiency (FE) of CH4 reached up to 97.5% on graphite plate. Meanwhile, the maximum acetate yield achieved 1,330 g m-2 d-1 with CO2 conversion efficiency into acetate close to 100% on carbon nanotube cathodes. In photocatalyst-assisted systems, the maximum acetate yield could reach 0.51 g L-1 d-1 with the coulombic efficiency of 96% on the MnFe2O4/g-C3N4 photocathode. Finally, prospects for future development and practical applications of MES are discussed, offering theoretical guidance for the fabrication of cathode materials that can improve production efficiency and reduce energy input.
Rechargeable potassium-ion batteries (PIBs) have gained attention as sustainable, environmentally friendly, and cost-effective large-scale stationary energy storage technology. However, although this technology was assumed to perform in a manner similar to that of its monovalent counterparts, huge anode volume expansion and sluggish kinetics are posing challenges in up-scaling it. Apart from the efforts to develop and optimise electrode materials, recent research endeavours have also focussed on the essential role of sustainability. These attempts have often relied on bio-derived and bio-inspired materials to mimic the effectiveness of nature. Furthermore, the use of materials with self-healing properties can alleviate electrode degradation after cycling and augment its electrochemical performance. This review summarises the development of smart materials with self-healing properties that aid in overcoming the present issues of PIBs and highlights the relevance of the interphases. In addition, state-of-the-art design strategies for bio-derived and bio-inspired materials are presented and discussed. The incorporation of recycled and sustainable materials into the manufacturing of PIBs is expected to contribute towards the ultimate goal of achieving truly circular economy ecosystems. Finally, perspectives for further advancements are provided to kindle new ideas and open questions regarding the use of new-generation materials in the development of PIBs.
Metal-organic frameworks (MOFs) have attracted increasing attention in electrochemistry due to their inherent characteristics, such as large specific surface area, high porosity, and structural flexibility. Defects can be designed and generated during the synthesis of MOFs, and their presence gives MOF materials excellent properties in terms of electrochemical energy conversion and storage. This review focuses on the types of defects in MOFs and presents recent and important advances in the methods for introducing defects into MOFs and the effects of defects on the physicochemical properties of MOFs, with emphasis on the application of defective MOFs as catalysts for electrochemical energy conversion and storage. On this basis, the current advantages and disadvantages of defective MOFs in electrochemical energy conversion and storage are presented and future research directions for defective MOFs construction in electrochemical applications are proposed.
The energy density of lithium-ion batteries based on intercalated electrode materials has reached its upper limit, which makes it challenging to meet the growing demand for high-energy storage systems. Electrode materials based on conversion reactions such as sulfur, organosulfides, and oxygen involving breakage and reformation of chemical bonds can provide higher specific capacity and energy density. In addition, they usually consist of abundant elements, making them renewable. Although they have the aforementioned benefits, they face numerous challenges for practical applications. For example, the cycled products of sulfur and molecular organosulfides could be soluble in a liquid electrolyte, resulting in the shuttle effect and significant capacity loss. The discharged product of oxygen is Li2O2, which could result in high charge overpotential and decomposition of the electrolyte. In this review, we present an overview of the current strategies for improving the performances of lithium-sulfur, lithiumorganosulfide, and lithium-oxygen batteries. First, we summarize the efforts to overcome the issues facing sulfur and organosulfide cathodes, as well as the strategies to increase the capacity of organosulfides. Then, we introduce the latest research progress on catalysts in lithium-oxygen batteries. Finally, we summarize and provide outlooks for the conversion of electrode materials.
The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) for dual-functional non-precious metal electrocatalysts are promising alternatives for Pt/Ru-based materials in rechargeable zinc-air batteries (ZABs). However, how to achieve dual-functional oxygen electrocatalytic activity on single-component catalysts and identify the sites responsible for ORR and OER still face many challenges. Herein, an efficient and stable dual-functional electrocatalyst is fabricated by a two-step hydrothermal method with iron phthalocyanine (FePc) π-π stacking on nickel-iron selenide layered hydroxide derivatives (Se/Ni3Se4/Fe3O4). The as-prepared multi-component catalyst (named as FePc/Se@NiFe) exhibits better oxygen electrocatalytic properties than Pt/Ru-based catalysts, with a half-wave potential (E1/2) of 0.90 V and an overpotential of 10 mA cm-2 (Ej10) of 320 mV. More importantly, chronoamperometry (I-T) and accelerated durability tests (ADT) show the unordinary stability of the catalyst. Both physical characterization and experimental results verify that the Fe-N4 moieties and Ni3Se4 crystalline phase are the main active sites for ORR and OER activities, respectively. The small potential gap (ΔE = Ej10 - E1/2 = 0.622 V) represents superior dual-functional activities of the FePc/Se@NiFe catalyst. Subsequently, the ZABs assembled using FePc/Se@NiFe exhibit excellent performances. This study offers a promising design concept for promoting further development of high-performance ORR and OER electrocatalysts and their application in ZAB.
The energy density of conventional graphite anode batteries is insufficient to meet the requirement for portable devices, electric cars, and smart grids. As a result, researchers have diverted to lithium metal anode batteries. Lithium metal has a theoretical specific capacity (3,860 mAh·g-1) significantly higher than that of graphite. Additionally, it has a lower redox potential of -3.04 V compared to standard hydrogen electrodes. These properties make high-energy lithium metal batteries a promising candidate for next-generation energy storage devices, which have garnered significant interest for several years. However, the high activity of lithium metal anodes poses safety risks (e.g., short circuits and thermal runaway) that hinder their commercial growth. Currently, modification of reversible lithium anodes is the primary focus of lithium metal batteries. This article presents conceptual models and numerical simulations that address failure processes and offer specific techniques to mitigate the challenges of lithium metal anodes, including electrolyte design, interface engineering, and electrode modification. It is expected that lithium metal batteries will recover and become a feasible energy storage solution.
The effect of confining a liquid electrolyte into a polymer matrix was studied by means of Raman spectroscopy, differential scanning calorimetry, temperature-modulated differential scanning calorimetry, dielectric spectroscopy, and rheology. The polymer matrix was obtained from thermal curing ethoxylated bisphenol A dimethacrylate while the liquid electrolyte consisted of a protic ionic liquid based on the ethyl-imidazolium cation [C2HIm] and the bis(trifluoromethanesulfonyl)imide [TFSI] anion, doped with LiTFSI salt. We report that the confined liquid phase exhibits the following characteristics: (i) a distinctly reduced degree of crystallinity; (ii) a broader distribution of relaxation times; (iii) reduced dielectric strength; (iv) a reduced cooperativity length scale at the liquid-to-glass transition temperature (T g); and (v) up-speeded local T g-related ion dynamics. The latter is indicative of weak interfacial interactions between the two nanophases and a strong geometrical confinement effect, which dictates both the ion dynamics and the coupled structural relaxation, hence lowering Tg by about 4 K. We also find that at room temperature, the ionic conductivity of the structural electrolyte achieves a value of 0.13 mS/cm, one decade lower than the corresponding bulk electrolyte. Three mobile ions (Im+, TFSI-, and Li+) contribute to the measured ionic conductivity, implicitly reducing the Li+ transference number. In addition, we report that the investigated solid polymer electrolytes exhibit the shear modulus needed for transferring the mechanical load to the carbon fibers in a structural battery. Based on these findings, we conclude that optimized microphase-separated polymer electrolytes, including a protic ionic liquid, are promising for the development of novel multifunctional electrolytes for use in future structural batteries.
Stretchable energy-storage devices are required to power next-generation wearable electronics intimately integrated with the human body. The microbatteries and microsupercapacitors represent promising candidates featuring small footprints and facile system integration. This perspective reviews common strategies to convert conventional rigid devices into stretchable forms. Several prototype soft electronic systems are presented utilizing microbatteries and microsupercapacitors as power sources. We discuss the current challenges and perspectives of the stretchable microbattery and microsupercapacitor. Stretchable forms of miniaturized energy-storage devices often show a significant trade-off between mechanical deformability and electrochemical performances, which present attractive opportunities for the material and engineering community.
Despite extensive research efforts to develop non-aqueous sodium-ion batteries (SIBs) as alternatives to lithium-based energy storage battery systems, their performance is still hindered by electrode-electrolyte side reactions. As a feasible strategy, the engineering of electrolyte additives has been regarded as one of the effective ways to address these critical problems. In this review, we provide a comprehensive overview of recent progress in electrolyte additives for non-aqueous SIBs. We classify the additives based on their effects on specific electrode materials and discuss the functions and mechanisms of each additive category. Finally, we propose future directions for electrolyte additive research, including studies on additives for improving cell performance under extreme conditions, optimizing electrolyte additive combinations, understanding the effect of additives on cathode-anode interactions, and understanding the characteristics of electrolyte additives.
As the peculiar element in the Periodic Table of Elements, fluorine gas owns the highest standard electrode potential of 2.87 V vs. F-, and a fluorine atom has the maximum electronegativity. Benefiting from the prominent property, fluorine plays an important role in the development of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) in terms of cathode materials (transition metal fluorides, fluorinated polyanionic compounds), electrolytes, and interfaces. In cathode materials, the highly electronegative renders enhanced ionic character of transition metal fluorine bonds and correspondingly high working potential in electrolytes; fluorinated electrolytes possess good antioxidant ability and flame retardance, which can significantly improve the thermal safety of a battery. On an electrode-electrolyte interface, the fluorine-rich inorganic component (such as LiF and NaF) is essential for the formation of a robust and stable solid electrolyte interface on anodes. Despite the remarkable advances achieved in fluorinated cathodes, electrolytes, and interfaces, there is still a lack of comprehensive understanding of the function of fluorides in LIBs and SIBs. Accordingly, this review briefly summarized the recent progress of fluorine-based electrodes, electrolytes, and interfaces and highlighted the correlation between the composition, property, and function to reveal the fluorine chemistry in LIBs and SIBs. This review will provide guidance for the rational design and targeted regulation of fluorine-dominated high-performance electrode materials, functionalized electrolytes, and consolidated interfaces.
Covalently bonded two-dimensional (2D) self-intercalated transition metal chalcogenides (i.e., ic-2Ds) have been recently fabricated experimentally, and their properties are highly tunable by stoichiometry and composition. Inspired by this progress, we focus on the applications of ic-2Ds in the field of electrochemistry and systematically investigate their performance in lithium-ion batteries (LIBs) and electrocatalytic hydrogen evolution reactions (HER). By means of density functional theory calculations, seven 3d-metal ic-2Ds are confirmed to be thermodynamically, mechanically, and thermally stable. The metallicity and abundant active sites endow these ic-2Ds with the potential as excellent electrode materials and HER catalysts. Among them, Ti7S12 and V7S12 exhibit the potential as anode materials for LIBs, showing low Li diffusion energy barriers, suitable open-circuit voltages, and ultrahigh capacity of 745.6 and 723.9 mA hg-1, respectively; Cr7S12 and Co7S12 show promises for HER with moderate hydrogen adsorption strengths. This theoretical study provides a new avenue for the application of newly reported ic-2Ds in various electrochemical energy conversion and storage applications.
Potassium-ion batteries (PIBs) have attracted significant attention as a complement to lithium-ion and sodium-ion batteries (SIBs). PIBs can theoretically provide higher specific energy and power density than SIBs due to lower standard electrode potential of K/K+ and faster K+ ion diffusion, maintaining the benefits of low-cost and sustainability. However, research on PIBs is in its infancy; therefore, further efforts are necessary to enhance their performance and position them as a competitive technology. In this perspective, the remaining challenges and possible strategies to advance the development of PIBs are presented.
The lithium-sulfur (Li-S) battery has been attracting much more attention in recent years due to its high theoretical capacity and low cost, although various issues, such as the “shuttle effect” and the low use ratio of active materials, have been hindering the development and application of Li-S batteries. The separator is an important part of Li-S batteries, and its modification is a simple and effective strategy to improve the electrochemical performance of Li-S batteries. In this work, we explore separators with different functions on their two sides that have been produced by a step-by-step electrospinning method. The multifunctional separator on one side is pure gelatin, and the other side is zeolitic imidazolate framework-67 (ZIF-67)-C60-gelatin. The ZIF-67-C60-gelatin layer on the cathode side is of great importance. The chemisorption sites on it are provided by ZIF-67, and the transformation sites of lithium polysulfide are provided by C60. Gelatin, which is on the anode side, as an admirable separator material, makes the lithium flux uniform and thus prevents the generation of lithium dendrites. This type of multifunctional nanofiber separator based on double gelatin layers plays an important role in the adsorption and conversion of polysulfides, and it improves the overall performance of the Li-S battery. As a result, the Li-S batteries assembled with the prepared separator can still maintain the capacity of 888 mAh g-1 after 100 cycles at 0.2 C, and the capacity retention rate of the Li-S batteries is 72.9% after 400 cycles at 2 C. This simple preparation method and high-performance bilayer membrane structure provide a new route for commercial application.
Potassium-ion batteries (PIBs) are considered as promising alternatives to lithium-ion batteries (LIBs) due to their abundant potassium resources, cost-effectiveness, and comparable electrochemical performance to LIBs. However, the practical application of PIBs is hindered by the slow dynamics and large volume expansion of anode materials. Owing to their unique morphology, rich pores, abundant active sites, and tunable composition, metal-organic framework (MOF)-derived carbon and its composites have been widely studied and developed as PIB anodes. In this review, the basic configuration, performance evaluation indicators, and energy storage mechanisms of PIBs were first introduced, followed by a comprehensive summary of the research progress in MOF-derived carbon and its composites, especially the design strategies and different types of composites. Moreover, the advances of in situ characterization techniques to understand the electrochemical mechanism during potassiation/depotassiation were also highlighted, which is crucial for the directional optimization of the electrochemical performance of PIBs. Finally, the challenges and development prospects of MOF-derived carbon and its composites for PIBs are prospected. It is envisioned that this review will guide and inspire more research efforts toward advanced MOF-derived PIB anode materials in the future.
Aluminum (Al) foil, serving as the predominant current collector for cathode materials in lithium batteries, is still unsatisfactory in meeting the increasing energy density demand of rechargeable energy storage systems due to its severe corrosion under high voltages. Such Al corrosion may cause delamination of cathodes, increasement of internal resistance, and catalysis of electrolyte decomposition, thus leading to premature failure of batteries. Hence, a systematic understanding of the corrosion mechanisms and effective anticorrosion strategies are necessary to enhance overall performance of lithium batteries. In this review, the corrosive mechanisms related to Al current collectors are systematically summarized and clarified. In addition, an overview on recent progress and advancement of strategies toward inhibiting Al corrosion is presented. In the end, we also provide a perspective with motivation to stimulate new ideas and research directions to further inhibit Al corrosion to achieve high energy density, long cycle life, and high safety of lithium batteries.
Lithium-ion batteries (LIBs) are the predominant power source for portable electronic devices, and in recent years, their use has extended to higher-energy and larger devices. However, to satisfy the stringent requirements of safety and energy density, further material advancements are required. Due to the inherent flammability and incompatibility of organic solvent-based liquid electrolytes with materials utilized in high energy devices, it is necessary to transition to alternative conductive mediums. The focus is shifting from molecular materials to a class of materials based on ions, including ionic liquids (ILs) and their derivatives such as zwitterionic ILs, polymerized ILs, and solvated ILs, which possess high levels of safety, stability, compatibility, and the ability to rationally design ILs for specific applications. Ion design is crucial to achieve superior control of electrode/electrolyte interphases (EEIs) both on anode and cathode surfaces to realize safer and higher-energy lithium-metal batteries (LMBs). This review summarizes the different uses of ILs in electrolytes (both liquid and solids) for LMBs, reporting the most promising results obtained during the last years and highlighting their role in the formation of suitable EEIs. Furthermore, a discussion on the use of deep-eutectic solvents is also provided, which is a class of material with similar properties to ILs and an important alternative from the viewpoint of sustainability. Lastly, future prospects for the optimization of IL-based electrolytes are summarized, ranging from the functional design of ionic structures to the realization of nanophases with specific features.
Currently, intensive research is underway to develop stable electrolyte systems that can significantly enhance the performance of rechargeable batteries. Recent advances in solid electrolytes have led to new types of promising systems owing to their high conductivity. This has generated considerable interest in the practical applications of safe batteries. Considering the safety concerns associated with rechargeable batteries, solid electrolytes have become indispensable for the advancement of next-generation battery technologies. However, the increased interfacial resistance at solid-solid interfaces has become a critical challenge. To address this problem, room-temperature ionic liquids (RTILs) have been investigated as functional materials for mitigating the interfacial resistance in solid-state batteries (SSBs). The special properties of RTILs, such as their non-volatility, non-flammability, and high safety characteristics, make them highly promising candidates for safe batteries. Various approaches have been explored for the effective utilization of ionic liquids in SSBs. This review provides a comprehensive discussion on the application of RTILs as electrolytes, considering their electrochemical properties and incorporation into composites to minimize resistance in SSBs.
The application of Li-S batteries (LSBs) is hindered by the undesired shuttle effect that leads to the fast consumption of active materials. The separator modification by using the carbon matrix with embedded metal nitride as catalyst can ease the problem. However, the previous synthesis processes of metal nitride catalysts are difficult to achieve a balance between their high-density production, homogenous distribution and excellent electronic contact with conductive substrates. Herein, we propose a bond scissoring strategy based on g-C3N4 to prepare NbN catalyst domains with high-density loading uniformly embedded in mesoporous thin-layer conductive carbon network (NbN/C) for durable LSBs. The molten salt reaction process is favorable for the diffusion of Nb cations into a porous g-C3N4 precursor to break the C-N bond and immobilize the N element. The residual monolithic carbon framework with space confinement effect limits the irregular growth and stacking of NbN precipitates. The NbN catalytic domains exhibit a strong adsorption effect on lithium polysulfides (LiPSs) and accelerate their liquid-solid conversion reactions. The LSBs utilizing an NbN/C-modified separator show superior cycling and rate performance, with a high-capacity retention of 72.7% after 1,000 cycles under 2 C and a high areal capacity of ~7.08 mA h cm-2 under a high sulfur loading of 6.6 mg cm-2. This g-C3N4-assisted strategy opens a new gate for the design of an integrated catalysis-conduction network for high-performance LSBs.
Given the fast-growing demand for lithium-ion batteries (LIBs) and the upcoming climax of LIB retirement, efficient recycling of spent LIBs has shown increasing importance in both economic benefit and environmental conservation. The LIBs with LiFePO4 (LFP) cathodes account for half of the LIB market, so developing an appropriate recycling way for spent LFP (SLFP) batteries is imperative. In this work, a closed-loop regeneration of SLFP cathodes is proposed, in which a facile cold stimulation route is invented to peel the SLFP layer from Al foil, and then Li and Fe elements are selectively and efficiently extracted from the peeling SLFP layer under mild conditions based on an oxidant of NaClO. The leaching rate of elemental Li could reach 98.3%, and the regenerated LFP synthesized by recovered Li2CO3 and FePO4 shows exceptional performance with a discharge capacity of 162.6 mAh g-1 at 0.5 C. This regeneration route has greatly reduced the use of chemical reagents, shortened the process of impurity removal, and, therefore, realized the closed-loop regeneration of SLFP batteries.
Phase change materials (PCMs) are considered one of the most promising energy storage methods owing to their beneficial effects on a larger latent heat, smaller volume change, and easier controlling than other materials. PCMs are widely used in solar energy heating, industrial waste heat utilization, energy conservation in the construction industry, and other fields. To avoid leakage, phase separation, and volatile problems of PCMs, the encapsulation technique typically uses organic polymer materials as shell structures of microcapsules. Furthermore, using inorganic materials to enhance the thermal property of phase change microcapsules is a popular approach in recent research. Especially, graphene oxide (GO) with high thermal conductivity was used as a common thermal conducting additive to improve the thermal performance of phase change microcapsules. Due to its amphiphilic property, GO combined with PCM microcapsules can achieve a variety of nanostructures for thermal energy storage. In this paper, four aspects have been summarized: configuration of PCMs, methods of combining GO with phase change microcapsules, position and content of GO, and applications of PCM/GO microcapsules. This work attempts to discuss preparation methods and heat-conducting properties of the PCM/GO microcapsules, which helps to better promote the application-targeted design and greatly improve the thermal properties of PCM microcapsules for various applications.
