Aprotic Li-O2 batteries have drawn considerable attention owing to their high theoretical energy density, but their sluggish cathode reaction kinetics leads to large overvoltages and poor cycling stability. Herein, freestanding one-dimensional Ni-DABDT (2,5-diaminobenzene-1,4-dithiol) metal-organic frameworks with asymmetric coordination configuration (Ni-N2S2) are synthesized as catalytic cathodes for Li-O2 batteries. The asymmetric Ni-N2S2 coordination stabilizes the low-spin state of the Ni center, and it promotes O2 chemisorption and hybridization between the Ni 3dz2 orbital and the pi* orbital of O2. This accelerates oxygen redox kinetics and promotes the formation of small-sized toroidal Li2O2 particles on Ni-N2S2 during discharge and hence facilitates their reversible decomposition. As a result, the Li-O2 batteries exhibit a low overvoltage gap of 0.61 V, superior rate performance and long-term stability over 450 cycles, while a 50 mAh pouch cell also demonstrates good cycle stability. This work highlights the importance of coordination environment regulation in electrocatalysts for Li-O2 batteries.

Seawater-based Mg-air batteries are promising power source for marine applications, however the inevitable corrosion of Mg anode induced by H2O and chloride ion (Cl-) severely compromises their energy efficiency and anode utilization. Herein, poly(styrenesulfonate) anions (PSS) are introduced as an electrolyte additive to regulate the corrosion kinetics of Mg anode in NaCl solution and natural seawater. At the anode/electrolyte interface, an optimized mass fraction of PSS promotes the formation of a Cl--depleted inner Helmholtz plane (IHP), which enables a dynamically evolving passive layer and allows controlled exposure of fresh Mg surfaces. In the bulk electrolyte, PSS preferentially coordinates with H2O and Mg2+ rather than Cl-, reducing free water content and facilitating the diffusion of Mg2+. These promote corrosion-enhanced discharge and endow seawater-based Mg-air batteries with superior power density, high discharge voltage and improved anode utilization. This work highlights the vital role of corrosion kinetics for high-performance Mg-air batteries in marine environments.

Hard carbon (HC) has emerged as a promising anode material for sodium-ion batteries (SIBs), however, it suffers from low specific capacity and inferior initial Coulombic efficiency (ICE). Herein, an oxygen-driven molecular reconfiguration strategy is proposed to strengthen reversible Na+ storage in HC through synergistic alkali activation and pre-oxidation. The oxygen functional groups on the surface promote the reconstruction of sp2-carbon within the highly cross-linked amorphous macromolecular coal precursor, thereby enabling the coal-based HC featuring with expanded interlayer spacing, increased pseudo-graphitic and closed-pore domains. This effectively facilitates the Na+ transport kinetics and stable Na+ (de)intercalation of HC, simultaneously suppressing the electrolyte decomposition. The resultant HC delivers a high reversible capacity of 317.4 mAh g-1 at 25 mA g-1, an impressive ICE of 88.05%, excellent rate capability of 253.42  mAh g-1 at 1000 mA g-1, and a superior capacity retention of 82.92% over 1000 cycles. This work highlights the crucial role of oxygen-driven microstructural reconstruction in durable sodium storage of HC.

Li-O2 batteries have aroused considerable interest due to high theoretical energy density; however, the singlet oxygen (1O2) generated in both discharge and charge processes induces severe parasitic reactions and leads to their low round-trip efficiency and poor rechargeability. Herein, a universal heavy atom-induced quenching mechanism is proposed to suppress 1O2 and related side reactions. Br in tris(4-bromophenyl)amine (TBPA) induces strong heavy atom-induced spin-orbit coupling (SOC), enhancing the interaction between the spin angular momentum and the orbital angular momentum of the electron. It enables TBPA to capture electrophilic 1O2 to form a singlet complex and then effectively drives the spin-forbidden spin-flip process to form a triplet complex. This accelerates the conversion of 1O2 to ground-state 3O2 through a heavy atom-induced intersystem crossing mechanism, and it efficiently eliminates its attack on organic solvents and carbon cathodes. These endow the Li-O2 battery with reduced overvoltages and prolonged lifespan for over 350 cycles when coupled with a RuO2 catalyst. This work highlights the heavy atom-induced SOC to quench 1O2 in oxygen evolution reaction-related devices.

Rechargeable Li-CO2 batteries have attracted extensive attention owing to their high theoretical energy density (1876 W h Kg-1). However, their practical application is hindered by large polarization, low coulombic efficiency, and cathode degradation. The electrochemical performance of Li-CO2 batteries is significantly affected by the thermodynamic stability and reaction kinetics of discharge products. Although advances have been achieved in cathode design and electrolyte optimization over the past decade, the reaction mechanism of the CO2 cathode has not yet been clear. In this review, various reaction mechanisms of CO2 reduction and evolution at the cathode interface are discussed, including different reaction routes under mixed O2/CO2 and pure CO2 environments. Furthermore, the regulating strategies of different discharge products, including Li2CO3, Li2C2O6, and Li2C2O4, are summarized to decrease the polarization and improve the cycling performance of Li-CO2 batteries. Finally, the challenges and perspectives are discussed from three aspects: reaction mechanisms, cathode catalysts, and electrolyte engineering, offering insights for the development of Li-CO2 batteries in the future.

Light-assisted Li-O2 batteries exhibit a high round-trip efficiency attributable to the assistance of light-generated electrons and holes in oxygen reduction and evolution reactions. Nonetheless, the excitonic effect arising from Coulomb interaction between electrons and holes impedes carrier separation, thus hindering efficient utilization of photo-energy. Herein, porphyrinic metal-organic frameworks with (Fe2Ni)O(COO)6 clusters are used as photocathodes to accelerate exciton dissociation into charge carriers for light-assisted Li-O2 batteries. The coupling of Ni 3d and Fe 3d orbitals boosts ligand-to-metal cluster charge transfer, and hence drives exciton dissociation and activates O2 for superoxide (•O2 -) radicals, rather than singlet oxygen (1O2) under photoexcitation. These enable the light-assisted Li-O2 batteries with a low total overvoltage of 0.28 V and round-trip efficiency of 92% under light irradiation of 100 mW cm-2. This work highlights the excitonic effect in photoelectrochemical processes and provides insights into photocathode design for light-assisted Li-O2 batteries.

Sodium-ion batteries (SIBs) are recognized as promising energy storage devices. However, they suffer from rapid capacity decay at ultra-low temperatures due to high Na + desolvation energy barrier and unstable solid electrolyte interphase (SEI). Herein, a weakly solvating electrolyte (WSE) with decreased ion-dipole interactions is designed for stable sodium storage in hard carbon (HC) anode at ultra-low temperatures. 2-methyltetrahydrofuran with low solvating power is incorporated into tetrahydrofuran to regulate the interactions between Na + and solvents. The reduced Na + -dipole interactions facilitate more anionic coordination in the first solvation sheath, which consistently maintains anion-enhanced solvation structures from room to low temperatures to promote inorganic-rich SEI formation. These enable WSE with a low freezing point of −83.3 °C and faster Na + desolvation kinetics. The HC anode thus affords reversible capacities of 243.2 and 205.4 mAh g −1 at 50 mA g −1 at −40 and −60 °C, respectively, and the full cell of HC||Na 3 V 2 (PO 4 ) 3 yields an extended lifespan over 250 cycles with high capacity retention of ~100 % at −40 °C. This work sheds new lights on the ion-dipole regulation for ultra-low temperature SIBs.

Recent advances on functional framework materials, including PCFs and IOFs, are summarized to regulate interfacial chemistry in metal batteries, which facilitate cation desolvation and metal nucleation for improved electrochemical performance.

Rechargeable lithium-oxygen(Li-O2)batteries have attracted wide attention due to their high energy density.However,the sluggish cathode kinetics results in high overvoltage and poor cycling performance.Ruthenium(Ru)-based elec-trocatalysts have been demonstrated to be promising cathode catalysts to promote oxygen evolution reaction(OER).It facilitates decomposition of lithium peroxide(Li2O2)by adjusting Li2O2 morphologies,which is due to the strong interaction between Ru-based catalyst and superoxide anion(O2-)intermediate.In this review,the design strategies of Ru-based electrocatalysts are introduced to enhance their OER catalytic kinetics in Li-O2 batteries.Different configu-rations of Ru-based catalysts,including metal particles(Ru metal and alloys),single-atom catalysts,and Ru-loaded compounds with various substrates(carbon materials,metal oxides/sulfides),have been summarized to regulate the electronic structure and the matrix architecture of the Ru-based electrocatalysts.The structure-property relationship of Ru-based catalysts is discussed for a better understanding of the Li2O2 decomposition mechanism at the cathode interface.Finally,the challenges of Ru-based electrocatalysts are proposed for the future development of Li-O2 batteries.

Li-O-2 batteries have garnered much attention due to their high theoretical energy density. However, the irreversible lithium plating/stripping on the anode limits their performance, which has been paid little attention. Herein, a solvation-regulated strategy for stable lithium anodes in tetraethylene glycol dimethyl ether (G4) based electrolyte is attempted in Li-O-2 batteries. Trifluoroacetate anions (TFA(-)) with strong Li+ affinity are incorporated into the lithium bis(fluorosulfonyl)imide (LiTFSI)/G4 electrolyte to attenuate the Li+-G4 interaction and form anion-dominant solvates. The bisalt electrolyte with 0.5 M LiTFA and 0.5 M LiTFSI mitigates G4 decomposition and induces an inorganic-rich solid electrolyte interphase (SEI). This contributes to decreased desolvation energy barrier from 58.20 to 46.31 kJ mol(-1), compared with 1.0 M LiTFSI/G4, for facile interfacial Li+ diffusion and high efficiency. It yields extended lifespan of 120 cycles in Li-O-2 battery with a limited Li anode (7 mAh cm(-2)). This work gains comprehensive insights into rational electrolyte design for Li-O-2 batteries.

Aprotic Li-O-2 battery has attracted considerable interest for high theoretical energy density, however the disproportionation of the intermediate of superoxide (O-2(-)) during discharge and charge leads to slow reaction kinetics and large voltage hysteresis. Herein, the chemically stable ruthenium tris(bipyridine) (RB) cations are employed as a soluble catalyst to alternate the pathway of O-2(-) disproportionation and its kinetics in both the discharge and charge processes. RB captures O-2(-) dimer and promotes their intramolecular charge transfer, and it decreases the energy barrier of the disproportionation reaction from 7.70 to 0.70 kcal mol(-1). This facilitates the discharge and charge processes and simultaneously mitigates O-2(-) and singlet oxygen related side reactions. These endow the Li-O-2 battery with reduced discharge/charge voltage gap of 0.72 V and prolonged lifespan for over 230 cycles when coupled with RuO2 catalyst. This work highlights the vital role of superoxide disproportionation for Li-O-2 battery.

Non-aqueous Li-O2 batteries have aroused considerable attention because of their ultrahigh theoretical energy density, but they are severely hindered by slow cathode reaction kinetics and large overvoltages, which are closely associated with the discharge product of Li2O2. Herein, hexagonal conductive metal-organic framework nanowire arrays of nickel-hexaiminotriphenylene (Ni-HTP) with quadrilateral Ni-N4 units are synthesized to incorporate Ru atoms into its skeleton for NiRu-HTP. The atomically dispersed Ru-N4 sites manifest strong adsorption for the LiO2 intermediate owing to its tunable d-band center, leading to its high local concentration around NiRu-HTP. This favors the formation of film-like Li2O2 on NiRu-HTP with promoted electron transfer and ion diffusion across the cathode electrolyte interface, facilitating its reversible decomposition during charge. These allow the Li-O2 battery with NiRu-HTP to deliver a remarkably reduced charge/ discharge polarization of 0.76 V and excellent cyclability. This work will enrich the design philosophy of electrocatalysts for regulation of kinetic behaviors of oxygen redox.

Rechargeable lithium-oxygen batteries (LOBs) are considered to be the next-generation energy technology owing to their high theoretical energy density. However, the sluggish cathode kinetics and degradation of Li anodes result in large voltage hysteresis and low coulombic efficiency. Various materials have been applied to promote the electrochemical performance of LOBs. Metal-organic frameworks (MOFs) possessing porous structures, open active sites and adjustable pore sizes have been attempted as promising materials for catalysts and separators of LOBs. This concept presents an overview of different MOF-based catalysts for LOBs, including traditional, conductive, semi-conductive and soluble MOFs, as well as our recently proposed photo-involved LOBs. Recent advances in MOF-based separators to restrain the shuttling of redox mediators between cathodes and anodes and suppress the formation of lithium dendrites are also discussed. Finally, perspectives on the development of MOF-based LOBs for future research are presented.

Aprotic Li-O2batteries are a promising energy storage technology, however severe side reactions during cycles lead to their poor rechargeability. Herein, highly reactive singlet oxygen (1O2) is revealed to generate in both the discharging and charging processes and is deterimental to battery stability. Electron-rich triphenylamine (TPA) is demonstrated as an effective quencher in the electrolyte to mitigate1O2and its associated parasitic reactions, which has the tertiary amine and phenyl groups to manifest excellent electrochemical stability and chemical reversibility. It reacts with electrophilic1O2to form a singlet complex during cycles, and it then quickly transforms to a triplet complex through nonradiative intersystem crossing (ISC). This efficiently accelerates the conversion of1O2to the ground-state triplet oxygen to eliminate its derived side reactions, and the regeneration of TPA. These enable the Li-O2battery with obviously reduced overvoltages and prolonged lifetime for over 310 cycles when coupled with a RuO2catalyst. This work highlights the ISC mechanism to quench1O2in Li-O2battery.

Lithium metal batteries (LMBs) have gained increasing attention owing to high energy density for large-scale energy storage applications. However, serious side reactions between Li anodes and organic electrolytes lead to low Columbic efficiency and Li dendrites. Although progress has been achieved in constructing electrode structures, the interfacial instability of Li anodes is still challenging. Solvation chemistry significantly affects the electrolyte properties and interfacial reactions, but the reaction mechanisms and the roles of each component in electrolytes are still vague. This review spotlights the recent development of electrolyte regulation with concentration and composition adjustments, aiming to understanding the correlation between solvation structures and Li anode stability. Further perspectives on the solvation design are provided in light of anode interfacial stability in LMBs.

Lithium-oxygen batteries promise ultrahigh energy density, yet one of the key barriers toward applications is the rapid performance decay during cycling especially at high rates, owing to the sluggish redox kinetics and severe parasitic reactions under elevated overpotentials within the cathode. In face of the above challenge, here we present a carbon nanotube sponge-based high-performance lithium-oxygen cathode by a series of approaches such as tailoring discharge product morphology to lower the overpotential, controlled sponge-compression for high mass loading to facilitate high-rate cycling, gradient electrolyte-immersion to rationally utilize its interior for efficient multiphase transport, and water treating for regenerated use. These 4 methods target different aspects of the electrochemical behavior in a Li-O-2 cathode, thus constituting a complementary and integrated strategy to overcome the challenges in this field. As a result, we achieve simultaneously an ultralong cycle life (1423 cycles, 2846 h) at high rate (0.5 mA cm(-2)) under low overpotential (charging below 4.0 V throughout 1100 cycles), also with an areal capacity over 20 mAh cm(-2) and extended 500 cycles after regeneration. Such an overall performance is much superior to recently developed 3D metal foam or carbon-based cathodes. Our designed sponge cathode represents a promising candidate for developing durable, high-energy and high-power metal-air battery systems, pushing forward their practical application.

Anionic redox reaction (ARR) in layered manganese-based oxide cathodes has been considered as an effective strategy to improve the energy density of sodium-ion batteries. Mn-vacancy layered oxides deliver a high ARR-related capacity with small voltage hysteresis, however, they are limited by rapid capacity degradation and poor rate capability, which arise from inferior structure changes due to repeated redox of lattice oxygen. Herein, redox-inactive Ti4+ is introduced to substitute partial Mn4+ to form Na2Ti0.5Mn2.5O7 (Na-4/7[square 1/7Ti1/7Mn5/7]O-2, h for Mn vacancies), which can effectively restrain unfavorable interlayer gliding of Na2Mn3O7 at high charge voltages, as reflected by an ultralow-strain volume variation of 0.11%. There is no irreversible O-2 evolution observed in Na2Ti0.5Mn2.5O7 upon charging, which stabilizes the lattice oxygen and ensures the overall structural stability. It exhibits increased capacity retention of 79.1% after 60 cycles in Na2Ti0.5Mn2.5O7 (17.1% in Na2Mn3O7) and good rate capability (92.1 mAh g(-1) at 0.5 A g(-1)). This investigation provides new insights into designing high-performance cathode materials with reversible ARR and structural stability for SIBs. (C) 2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

This study evaluated the effects of bio-based carbon materials on methane production by anaerobic digestion. The results showed that biochar and hydrochar can promote cumulative methane yield by 15% to 29%. However, there was no statistical significance (p > 0.05) between hydrochar and biochar produced at different temperature on methane production. 16S rRNA gene sequencing and bioinformatics analysis showed that biochar and hydrochar enriched microorganism that might participate in direct interspecies electron transfer (DIET) such as Pseudomonadaceae, Bacillaceae, and Clostridiaceae. The the surface properties of the modified biochar were characterized with BET, Raman, FTIR and XPS. Bio-based carbon materials with uniform dispersion provided a stable environment for the DIET of microorganisms and electrons are transferred through aromatic functional groups on the surface of materials. This study reveals bio-based carbon materials surface properties on methane production in anaerobic digestion and provides a new approach to recycling spent coffee grounds.

The reaction mechanism of non-aqueous Li-O-2 batteries is based on the deposition and decomposition of Li2O2. The polarization of Li-O-2 batteries can be rapidly increased by operation under a high rate condition, resulting in the early capacity fade of the cells. Therefore, a well-designed catalyst with a unique structure and excellent catalytic ability is an important way to boost the round-trip performance of Li-O-2 batteries, especially under high current density. In this work, a unique nanoflower structure assembled with Co3O4 nanosheets is synthesized by using 2-methylimidazole (2-MIM) as a structural directing agent. X-ray photoelectron spectroscopy (XPS) and Raman spectra reveal abundant oxygen vacancies on the surface of the Co3O4 nanoflower, which are beneficial for oxygen reduction and evolution reactions and long round-trip lifetime. Density functional theory results demonstrate that Co3O4 catalyst with oxygen vacancies could promote the wetting of Li2O2 on substrate and formation of a Li2O2 nanofilm, thereby boosting the discharge capacity of Li-O-2 batteries. On account of the synergistic effect of abundant oxygen vacancies, the unique structure, and excellent oxygen evolution reaction, Co(3)O(4 )nanoflower-based cells could deliver ultralong lifetime of 276 and 248 cycles with a discharge capacity of 1000 mAh g(-1) under charge/discharge current densities of 0.5 A g(-1) and 1 A g(-1), respectively. This study has shed light on a new strategy for catalyst preparation for long lifetime Li-O-2 batteries.

Solid polymer electrolytes can be used to construct solid-state lithium batteries (SSLBs) using lithium metals as the anode. However, the lifespan and safety problems of SSLBs caused by lithium dendrite growth have hindered their practical application. Here, we have designed and prepared a rigid-flexible asymmetric solid electrolyte (ASE) that is used in building SSLBs. The ASE can inhibit efficiently the growth of lithium dendrites and lead to a long cycle life of SSLBs due to the hierarchical structure of a combination of "polymer-in-ceramic" (i.e., rigid ceramic layer of Li6.4La3Zr1.4Ta0.6O12) and "LiBOB-in-polymer" (i.e., soft polymer-layer of polyethylene oxide and LiBOB components). The results demonstrated that a symmetrical battery with ASE (Li|ASE|Li) can be steadily cycled for more than 2000 h and yielded a flat plating/stripping voltage profile under a current density of 0.1 mA cm(-2). As a consequence, the SSLB of LiFePO4 vertical bar ASE|Li delivered a specific capacity of 155.1 mA h g(-1) with a capacity retention rate up to 90.2% after 200 cycles with the Coulombic efficiency over 99.6% per cycle. This asymmetric structure combines the advantages of ceramics and polymers, providing an ingenious solution for building rigid and flexible solid electrolytes.