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Aqueous all-iron redox flow batteries (RFBs) are promising competitors for next-generation grid-scale energy storage applications. However, the high-performance operation of all-iron RFBs in a wider temperature range is greatly hindered by inferior iron plating/stripping reaction and low solid-liquid transition temperature at Fe anode. Herein, a universal electrolyte additive design strategy for all-iron RFBs is reported, which realizes a highly reversible and dendrite-free Fe anode at low temperatures. Quantum chemistry calculations first screen several organic molecules with oxygen-containing functional groups and identify N,N-Dimethylacetmide (DMAc) as a potential candidate with low cost, high solubility, and strong interactions with Fe2+ and H2 O. Combined experimental characterizations and theoretical calculations subsequently demonstrate that adding DMAc into the FeCl2 solution effectively reshapes the primary solvation shell of Fe2+ via the Fe2+ -O (DMAc) bond and breaks hydrogen-bonding network of water through intensified H-bond interaction between DMAc and H2 O, thereby affording the Fe anode with enhanced Fe/Fe2+ reversibility and lower freezing point. Consequently, the assembled all-iron RFB achieves an excellent combination of high power density (25 mW cm-2 ), long charge-discharge cycling stability (95.59% capacity retention in 103 h), and preeminent battery efficiency at -20 °C (95% coulombic efficiency), which promise a future for wider temperature range operation of all-iron RFBs.
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The reversibility and stability of aqueous zinc-ion batteries (AZIBs) are largely limited by water-induced interfacial parasitic reactions. Here, dimethyl(3,3-difluoro-2-oxoheptyl)phosphonate (DP) is introduced to tailor primary solvation sheath and inner-Helmholtz configurations for robust zinc anode. Informed by theoretical guidance on solvation process, DP with high permanent dipole moments can effectively substitute the coordination of H2O with charge carriers through relatively strong ion-dipolar interactions, resulting in a water-lean environment of solvated Zn2+. Thus, interfacial side reactions can be suppressed through a shielding effect. Meanwhile, lone-pair electrons of oxygen and fluorinated features of DP also reinforce the interfacial affinity of metallic zinc, associated with exclusion of neighboring water to facilitate reversible zinc planarized deposition. Thus, these merits endow the Zn anode with a high-stability performance exceeds 3800â hours at 0.5â mA cm-2 and 0.5â mAh cm-2 for Zn||Zn batteries and a high average Coulombic efficiency of 99.8 % at 4â mA cm-2 and 1â mAh cm-2 for Zn||Cu batteries. Benefiting from the stable zinc anode, the Zn||NH4V4O10 cell maintains 80.3 % of initial discharge capacity after 3000â cycles at 5â A g-1 and exhibits a high retention rate of 99.4 % against to the initial capacity during the self-discharge characterizations.
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LiNO3 is a remarkable additive that can dramatically enhance the stability of ether-based electrolytes at lithium metal anodes. However, it has long been constrained by its incompatibility with commercially used ester electrolytes. Herein, we correlated the fundamental role of entropy with the limited LiNO3 solubility and proposed a new low-entropy-penalty design that achieves high intrinsic LiNO3 solubility in ester solvents by employing multivalent linear esters. This strategy is conceptually different from the conventional enthalpic methods that relies on extrinsic high-polarity carriers. In this way, LiNO3 can directly interact with the primary ester solvents and fundamentally alters the electrolyte properties, resulting in substantial improvements in lithium-metal batteries with high Coulombic efficiency and cycling stability. This work illustrates the significance of regulating the solvation entropy for high-performance electrolyte design.
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Solid polymer electrolytes are promising electrolytes for safe and high-energy-density lithium metal batteries. However, traditional ether-based polymer electrolytes are limited by their low lithium-ion conductivity and narrow electrochemical window because of the well-defined and intimated Li+-oxygen binding topologies in the solvation structure. Herein, we proposed a new strategy to reduce the Li+-polymer interaction and strengthen the anion-polymer interaction by combining strong Li+-O (ether) interactions, weak Li+-O (ester) interactions with steric hindrance in polymer electrolytes. In this way, a polymer electrolyte with a high lithium ion transference number (0.80) and anion-rich solvation structure is obtained. This polymer electrolyte possesses a wide electrochemical window (5.5â V versus Li/Li+) and compatibility with both Li metal anode and high-voltage NCM cathode. Li||LiNi0.5Co0.2Mn0.3O2 full cells with middle-high active material areal loading (~7.5â mg cm-2) can stably cycle at 4.5â V. This work provides new insight into the design of polymer electrolytes for high-energy-density lithium metal batteries through the regulation of ion-dipole interactions.
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Aqueous zinc ion batteries (AZIBs) show a great potential for next-generation energy storage due to their high safety and high energy density. However, the severe side reactions of zinc negative electrode largely hinder the further application of AZIBs. Herein, trace tris(hydroxymethyl)aminomethane (Tris) additive with rich lone-pair-electrons and zincophilic sites is firstly introduced to achieve long-term and highly reversible Zn plating/stripping. Specifically, Tris not only regulates the solvation structure of Zn2+, but is also adsorbed vertically on the Zn anode surface with a changed coordination intensity during the plating/stripping process of Zn to generate an in situ dynamic adsorption layer for the first time. The dynamic adsorption layer could successively attract the solvated Zn2+ and then promote the de-solvation of the solvated Zn2+ owing to the orientation polarization with regularly-changed applied electric field, the volume rejection effect, and strong intermolecular force towards H2O of the vertically-adsorbed Tris. Therefore, an improved Zn2+-transport kinetics as well as the inhibition of side reactions of Zn anode are successfully realized. Accordingly, the Zn||Zn symmetric cell provides an ultra-long cycle life of 2600â h. Furthermore, the Zn||MnO2 full cell with Tris could demonstrate a high capacity and structural stability for practical applications.
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Integral equation theory (IET) provides an effective solvation model for chemical and biological systems that balances computational efficiency and accuracy. We present a new software package, the expanded package for IET-based solvation (EPISOL), that performs 3D-reference interaction site model (3D-RISM) calculations to obtain the solvation structure and free energies of solute molecules in different solvents. In EPISOL, we have implemented 22 different closures, multiple free energy functionals, and new variations of 3D-RISM theory, including the recent hydrophobicity-induced density inhomogeneity (HI) theory for hydrophobic solutes and ion-dipole correction (IDC) theory for negatively charged solutes. To speed up the convergence and enhance the stability of the self-consistent iterations, we have introduced several numerical schemes in EPISOL, including a newly developed dynamic mixing approach. We show that these schemes have significantly reduced the failure rate of 3D-RISM calculations compared to AMBER-RISM software. EPISOL consists of both a user-friendly graphic interface and a kernel library that allows users to call its routines and adapt them to other programs. EPISOL is compatible with the force-field and coordinate files from both AMBER and GROMACS simulation packages. Moreover, EPISOL is equipped with an internal memory control to efficiently manage the use of physical memory, making it suitable for performing calculations on large biomolecules. We demonstrate that EPISOL can efficiently and accurately calculate solvation density distributions around various solute molecules (including a protein chaperone consisting of 120,715 atoms) and obtain solvent free energy for a wide range of organic compounds. We expect that EPISOL can be widely applied as a solvation model for chemical and biological systems. EPISOL is available at https://github.com/EPISOLrelease/EPISOL.
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Software , Termodinâmica , Solventes/química , Soluções , Simulação por ComputadorRESUMO
The electrochemical performances of lithium metal batteries are determined by the kinetics of interfacial de-solvation and ion transport, especially at low-temperature environments. Here, a novel electrolyte that easily de-solvated and conducive to interfacial film formation is designed for low-temperature lithium metal batteries. A fluorinated carboxylic ester, diethyl fluoromalonate (DEFM), and a fluorinated carbonate, fluoroethylene carbonate (FEC) are used as solvents, while high concentrated lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is served as the solute. Through tailoring the electrolyte formulation, the lithium ions in the high concentrated fluorinated carboxylic ester electrolyte are mainly combined with anions, which weakens the bonding strength of lithium ions and solvent molecules in the solvation structure, beneficial to the de-solvation process at low temperature. The fluorinated carboxylic ester (FCE) electrolyte enables the LiFePO4 (LFP) | Li half-cell achieves a high capacity of 91.9 mAh g-1 at -30 °C, with high F content in the interface. With optimized de-solvation kinetics, the LFP | Li full cell remains over 100 mAh g-1 at 0 °C after cycling 100 cycles. Building new solvents with outstanding low-temperature properties and weaker solvation to match with Li metal anode, this work brings new possibilities of realizing high energy density and low temperature energy storage batteries.
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Lithium metal batteries (LMBs) are promising for next-generation high-energy-density batteries owing to the highest specific capacity and the lowest potential of Li metal anode. However, the LMBs are normally confronted with drastic capacity fading under extremely cold conditions mainly due to the freezing issue and sluggish Li+ desolvation process in commercial ethylene carbonate (EC)-based electrolyte at ultra-low temperature (e.g., below -30 °C). To overcome the above challenges, an anti-freezing carboxylic ester of methyl propionate (MP)-based electrolyte with weak Li+ coordination and low-freezing temperature (below -60 °C) is designed, and the corresponding LiNi0.8 Co0.1 Mn0.1 O2 (NCM811) cathode exhibits a higher discharge capacity of 84.2 mAh g-1 and energy density of 195.0 Wh kg-1 cathode than that of the cathode (1.6 mAh g-1 and 3.9 Wh kg-1 cathode ) working in commercial EC-based electrolytes for NCM811â Li cell at -60 °C. Molecular dynamics simulation, Raman spectra, and nuclear magnetic resonance characterizations reveal that rich mobile Li+ and the unique solvation structure with weak Li+ coordination are achieved in MP-based electrolyte, which collectively facilitate the Li+ transference process at low temperature. This work provides fundamental insights into low-temperature electrolytes by regulating solvation structure, and offers the basic guidelines for the design of low-temperature electrolytes for LMBs.
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The dendrite growth and parasitic reactions that occur on Zn metal anode (ZMA)/electrolyte interface hinder the development of aqueous zinc ion batteries (AZIBs) in next-generation renewable energy storage systems. Fortunately, reconstructing the inner Helmholtz layer (IHL) by introducing an electrolyte additive, is viewed as one of the most promising strategies to harvest the stable ZMA. Herein, (4-chloro-3-nitrophenyl) (pyridin-4-yl) methanone (CNPM) with quadruple functional groups is introduced into the ZnSO4 electrolyte to reshape the interface between ZMA and electrolyte and change the solvation structure of Zn2+ . Density functional theory (DFT) calculations manifest that the âCâO, âCl, âCâNâ, and âNO2 functional groups of CNPM interact with metallic Zn simultaneously and adsorb on the ZMA surface in a parallel arrangement manner, thus forming a water-poor IHL and creating well-arranged ion transportation channels. Furthermore, theoretical calculations and experimental results demonstrate that CNPM absorbed on the Zn anode surface can serve as zincophilic sites for inducing uniform Zn deposition along the (002) plane. Benefiting from the synergistic effect of these functions, the dendrite growth and parasitic reactions are suppressed significantly. As a result, ZMA exhibits a long cycle life (2900 h) and high coulombic efficiency (CE) (500 cycles) in the ZnSO4 +CNPM electrolyte.
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The practical application of Zn metal anodes in electronic devices is hindered by dendrite growth and parasitic reactions. Electrolyte optimization, particularly the introduction of organic co-solvents, is widely used to circumvent these challenges. Various organic solvents in a wide range of concentrations have been reported; however, their influences and corresponding working mechanisms at different concentrations are largely unexplored in the same organic species. Herein, economical, low-flammable ethylene glycol (EG) is used as a model co-solvent in aqueous electrolytes to examine the relationship between its concentration, anode-stabilizing effect, and mechanism. Two maximal values are observed for the lifetime of Zn/Zn symmetric batteries under EG concentrations from 0.05 vol% to 48 vol%. Zn metal anodes can stably run for over 1700 h at a low EG content (0.25 vol%) and high EG content (40 vol%). Based on the complementary experimental and theoretical calculations, the enhancements in low- and high-content EG are ascribed to the specific surface adsorption for suppressed dendrite growth and the regulated solvation structure for inhibited side reactions, respectively. Intriguingly, a similar concentration-reliant bimodal phenomenon is observed in other low-flammable organic solvents (e.g., glycerol and dimethyl sulfoxide), thereby suggesting universality of this study and providing insight into electrolyte optimization.
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The practical applications of aqueous zinc ion batteries are hindered by the formation of dendrites on the anode, the narrow electrochemical window of electrolyte, and the instability of the cathode. To address all these challenges simultaneously, a multi-functional electrolyte additive of 1-phenylethylamine hydrochloride (PEA) is developed for aqueous zinc ion batteries based on polyaniline (PANI) cathode. Experiments and theoretical calculations confirm that the PEA additive can regulate the solvation sheath of Zn2+ and form a protective layer on the surface of the Zn metal anode. This broadens the electrochemical stability window of the aqueous electrolyte and enables uniform deposition of Zn. On the cathode side, the Cl- anions from PEA enter the PANI chain during charge and release fewer water molecules surrounding the oxidized PANI, thus suppressing harmful side reactions. When used in a Zn||PANI battery, this cathode/anode compatible electrolyte exhibits excellent rate performance and long cycle life, making it highly attractive for practical applications.
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The electrode/electrolyte interfaces play an important role in the electrochemical reaction kinetics to alleviate the severe polarization and voltage hysteresis in lithium primary batteries. Herein, C5 F5 N is proposed as an electrolyte additive to tune the characteristics of the electrode/electrolyte interfaces. The Li/CFx primary battery with C5 F5 N additive exhibits an excellent discharge-specific capacity of 981.4 mAh g-1 (0.1 C), a remarkable high-rate capability of 598 mAh g-1 (15 C), and an outstanding energy/power density of 1068.7 Wh kg-1 /24362.5 W kg-1 . It also shows remarkable storage performance with 717.2 mAh g-1 at 0.1 C after storage at 55 °C for 2 months. The excellent performance of the Li/CFx batteries is closely related to the improved and stable Li3 N/LiF-rich homogeneous interfaces induced by the C5 F5 N additive, which results in uniform distribution of Li+ flux, facilitated electrochemical kinetics, and increased rate capability of Li/CFx battery. Therefore, C5 F5 N is expected to be a promising electrolyte additive, and the related electrode/electrolyte interface engineering provides an effective and facile strategy to increase the performance of the lithium primary battery.
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The introduction of electrolyte additives is one of the most potential strategies to improve the performance of potassium metal batteries (PMBs). However, designing an additive that can alter the K+ solvation shell and essentially inhibit K dendrite remains a challenge. Herein, the amyl-triphenyl-phosphonium bromide was introduced as an additive to build a stable solid electrolyte interphase layer. The amyl-TPP cations can form a cation shielding layer on the metal surface during the nucleation stage, preventing K+ from gathering at the tip to form K dendrites. Besides, the cations can be preferentially reduced to form Kx Py with fast K+ transport kinetics. The Br- anions, as Lewis bases with strong electronegativity, can not only coordinate the Lewis acid pentafluoride to inhibit the formation of HF, but also change the K+ solvation structure to reduce solvent molecules in the first solvation structure. Therefore, the symmetrical battery exhibits a low deposition overpotential of 123 mV at 0.1 mA cm-2 over 4200 h cycle life. The full battery, paried with a perylene-tetracarboxylic dianhydride (PTCDA) cathode, possesses a cycle life of 250 cycles at 2 C and 81.9% capacity retention. This work offers a reasonable electrolyte design to obtain PMBs with long-term stablity and safety.
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High-voltage potassium-based batteries are promising alternatives for lithium-ion batteries as next-generation energy storage devices. The stability and reversibility of such systems depend largely on the properties of the corresponding electrolytes. This review first presents major challenges for high-voltage electrolytes, such as electrolyte decomposition, parasitic side reactions, and current collector corrosion. Then, the state-of-the-art modification strategies for traditional ester and ether-based organic electrolytes are scrutinized and discussed, including high concentration, localized high concentration/weakly solvating strategy, multi-ion strategy, and addition of high-voltage additives. Besides, research advances of other promising electrolyte systems, such as potassium-based ionic liquids and solid-state-electrolytes are also summarized. Finally, prospective future research directions are proposed to further enhance the oxidative stability and non-corrosiveness of electrolytes for high-voltage potassium batteries.
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Eletrólitos , Potássio , Corrosão , Fontes de Energia Elétrica , ÉsteresRESUMO
High-voltage lithium metal batteries (LMBs) pose severe challenges for the matching of electrolytes with aggressive electrodes, especially at low temperatures. Here, we report a rational modification of the Li+ solvation structure to extend the voltage and temperature operating ranges of conventional electrolytes. Ion-ion and ion-dipole interactions as well as the electrochemical window of solvents were tailored to improve oxidation stability and de-solvation kinetics of the electrolyte. Meanwhile, robust and elastic B and F-rich interphases are formed on both electrodes. Such optimization enables Li||LiNi0.5 Mn1.5 O4 cells (90.2 % retention after 400 cycles) and Li||LiNi0.6 Co0.2 Mn0.2 O2 (NCM622) cells (74.0 % retention after 200 cycles) to cycle stably at an ultra-high voltage of 4.9â V. Moreover, NCM622 cells deliver a considerable capacity of 143.5â mAh g-1 at -20 °C, showing great potential for practical uses. The proposed strategy sheds light on further optimization for high-voltage LMBs.
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Redox-active organic materials, as a new generation of sustainable resources, are receiving increasing attention in zinc-ion batteries (ZIBs) due to their resource abundance and tunable structure. However, organic molecules with high potential are rare, and the voltage of most reported organic cathode-based ZIBs is less than 1.2â V. Herein, we explored the redox process of p-type organics and figured out the relationship between energy change and voltage output during the process. Then, we proposed a dual-step strategy to effectively tune the energy change and eventually improve the output voltage of the organic electrode. Combining the regulation of the electron cloud of organic molecules and the manipulation of the solvation structure, the output voltage of an organosulfur compound based ZIB was greatly increased from 0.8â V to 1.7â V. Our results put forward a specific pathway to improve the working voltage and lay the foundation for the practical application of organic electrodes.
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Metal-metal batteries such as the 3 V Cu-Al system are highly desirable for large-scale energy storage owing to their low cost and excellent scalability of Cu and Al foils. However, the dissolved Cu cations will crossover from the cathode to the anode leading to poor electrochemical performance. In this work, it is demonstrated that the reversibility of the Cu-Al battery depends strongly on the interaction of the Cu ions with the electrolyte solvent and subsequently the affinity of the solvated Cu ion with the membrane separator. Specifically, a series of common carbonate-based electrolyte solvents are investigated via molecular dynamics and contact angle measurements to understand the interaction between the solvents and a polypropylene (PP) membrane, as well as that between cations and solvent. Among different solvents, fluoroethylene carbonate (FEC) is shown to drastically enhance the coulombic efficiency to 97%, compared to that of 27% with dimethyl carbonate. Remarkable cyclability of a 3 V Cu-Al battery with 3 m LiTFSI FEC and PP membrane up to 1000 cycles is further demonstrated. This finding opens new opportunities for the development of low-cost, high performance Cu-Al systems for stationary applications.
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Due to the intrinsic safety and cost effectiveness, aqueous Zn-ion batteries (AZIBs) are considered a promising candidate for future energy storage systems. However, the widespread implementation of AZIBs faces significant obstacles due to various undesirable side reactions, including hydrogen evolution reaction (HER), corrosion, and uncontrolled dendrite growth at the anodes. Here, 4-hydroxybenzoic acid sodium salt (PHB) is employed in the ZnSO4 electrolyte to enable highly-reversible zinc anodes. PHB has a greater tendency to bind with the Zn surface, resulting in increased steric effects within the electrolyte. As a result, it hinders the direct interaction between anode and water while facilitating the uniform plating of Zn2+ . Zn/Zn batteries with PHB additives realized more than 1600â h stable cycling life under 1â mA cm-2 and 1â mAh cm-2 . Moreover, Zn/Cu batteries with PHB additives achieved a reversible plating/stripping process for over 500â cycles with high average CE of 98.6 %. In addition, the assembled Zn/NH4 V4 O10 batteries with PHB additive yielded 80.5â mAh g-1 after 1000â cycles at 10â A g-1 . The inexpensive and effective application of PHB as an electrolyte additive has the potential to significantly enhance the stability and dependability of ZIBs.
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With the merits of the high energy density of batteries and power density of supercapacitors, the aqueous Zn-ion hybrid supercapacitors emerge as a promising candidate for applications where both rapid energy delivery and moderate energy storage are required. However, the narrow electrochemical window of aqueous electrolytes induces severe side reactions on the Zn metal anode and shortens its lifespan. It also limits the operation voltage and energy density of the Zn-ion hybrid supercapacitors. Using 'water in salt' electrolytes can effectively broaden their electrochemical windows, but this is at the expense of high cost, low ionic conductivity, and narrow temperature compatibility, compromising the electrochemical performance of the Zn-ion hybrid supercapacitors. Thus, designing a new electrolyte to balance these factors towards high-performance Zn-ion hybrid supercapacitors is urgent and necessary. We developed a dilute water/acetonitrile electrolyte (0.5 m Zn(CF3SO3)2 + 1 m LiTFSI-H2O/AN) for Zn-ion hybrid supercapacitors, which simultaneously exhibited expanded electrochemical window, decent ionic conductivity, and broad temperature compatibility. In this electrolyte, the hydration shells and hydrogen bonds are significantly modulated by the acetonitrile and TFSI- anions. As a result, a Zn-ion hybrid supercapacitor with such an electrolyte demonstrates a high operating voltage up to 2.2 V and long lifespan beyond 120,000 cycles.
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For electrolytes with conventional lithium salt concentration, it is not easy to generate sufficient anion-derived beneficial inorganic components to stabilize the electrolyte-lithium metal anode interface due to the repulsion of the free-state anions by the anode. In this study, the above issues are solved through the strong interaction between electronegative materials and lithium ions (Li+ ). A locally high Li+ concentration strategy is proposed by preparing micro-arrays of electronegative nano-hydroxyapatite (nHA) on the Cu foil. It is found that the oxygen atoms in the phosphate group (-PO4 ) of the nHA can strongly adsorb Li+ to form a locally Li+ -rich region, which increases the probability of anions interacting with Li+ . The formation of more Li+ -coordinated anions at the electrolyte-anode interface can reduce the Li+ de-solvation energy barrier, and enable the anions to completely decompose into lithium fluoride (LiF) and lithium nitride (Li3 N) on the Li metal anode. The interfacial transfer dynamics is accelerated and the Li dendrites are effectively suppressed. Under high current density, the anode exhibits a long lifespan with high Coulombic efficiency and small polarization voltage. The nHA micro-arrays achieve the targeted solvation structure at the electrolyte-anode interface while ensuring conventional lithium salt concentration in the bulk electrolyte.