RESUMEN
High-voltage sodium metal batteries are a highly intriguing battery technology in view of their resource sustainability, cost efficiency, and ultrahigh energy density. However, developing a high-performance electrolyte, compatible with both high-voltage cathodes and highly reactive sodium metal anodes, is extremely challenging. In this work, we delicately formulate a ternary phosphate electrolyte, composing of a cost-effective sodium bis(trifluoromethane sulfonyl) imide salt, a nonflammable triethyl phosphate (TEP) solvent, and a fluoroethylene carbonate (FEC) co-solvent. By rationally tailoring the TEP/FEC ratio, the ternary phosphate electrolyte displays a well-balanced performance, not only enabling highly efficient sodium deposition (an average Coulombic efficiency of 95.7% for Na//Cu cells) but also inheriting the intrinsic anodic stability (≥4.5 V vs Na+/Na) and nonflammability of phosphates. As a consequence, high-voltage Na3V2(PO4)2F3 cathode-based sodium metal cells (Na3V2(PO4)2F3//Na) deliver remarkable cyclic stability (97.9% capacity retention after 300 cycles), which is among the best for Na3V2(PO4)2F3-based batteries. This work may guide the electrolyte design principles and is highly enlightening in developing high energy density sodium-based batteries.
RESUMEN
V2O5, one of the earliest intercalation-type cathode materials investigated as a Li+ host, is characterized by an extremely high theoretical capacity (441 mAh g-1). However, the fast capacity fading upon cycling in conventional carbonate-based electrolytes is an unresolved issue. Herein, we show that using a LiTFSI/tetraglyme (1:1 in mole ratio) electrolyte yields a highly enhanced cycling ability of V2O5 (from 20% capacity retention to 80% after 100 cycles at 50 mA g-1 within 1.5-4.0 V vs Li+/Li). The improved performance mostly originates from the V2O5 electrode itself, since refreshing the electrolyte and the lithium electrode of the cycled cells does not help in restoring the V2O5 electrode capacity. Electrochemical impedance spectroscopy (EIS), post-mortem scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS) have been employed to investigate the origin of the improved electrochemical behavior. The results demonstrate that the enhanced cyclability is a consequence of a thinner but more stable cathode-electrolyte interphase (CEI) layer formed in LiTFSI/tetraglyme with respect to the one occurring in 1 M LiPF6 in EC/DMC (1:1 in weight ratio, LP30). These results show that the cyclability of V2O5 can be effectively improved by simple electrolyte engineering. At the same time, the uncovered mechanism further reveals the vital role of the CEI on the cyclability of V2O5, which can be helpful for the performance optimization of vanadium-oxide-based batteries.
RESUMEN
Gel-type polymer electrolytes are very promising to replace liquid electrolytes, addressing the leakage concerns in batteries. In this work, we report a concentrated gel polymer electrolyte for aqueous zinc-metal batteries, which manifests superior Zn stripping/plating reversibility and electrolyte stability, combined with a promising electrochemical stability window and robust water-retention ability. Quasi-solid-state Zn/V2O5 batteries employing such an electrolyte reach a specific energy of 326 W h kg-1 at 20 mA g-1 based on the cathode mass and a capacity retention of 93% over 600 cycles at 500 mA g-1. Moreover, the cell performs well in the 0-40 °C temperature range without significant capacity loss. These results represent important steps toward the development of high-energy aqueous zinc batteries.
RESUMEN
Utilization of high-capacity alloying anodes is a promising yet extremely challenging strategy in building high energy density alkali-ion batteries (AIBs). Excitingly, it was very recently found that the (de-)sodiation of tin (Sn) can be a highly reversible process in specific glyme electrolytes, enabling high specific capacities close to the theoretical value of 847 mA h g-1. The unique solid electrolyte interphase (SEI) formed on Sn electrodes, which allows highly reversible sodiation regardless of the huge volume expansion, is herein demonstrated according to a series of in situ and ex situ characterization techniques. The SEI formation process mainly involves NaPF6 decomposition and the polymerization/oligomerization of the glyme solvent, which is induced by the catalytic effect of tin, specifically. This work provides a paradigm showing how solvent, salt, and electrode materials synergistically mediate the SEI formation process and obtains new insights into the unique interfacial chemistry between Na-alloying electrodes and glyme electrolytes, which is highly enlightening in building high energy density AIBs.
RESUMEN
Aluminum is an appealing anode material for high-energy-density lithium-ion batteries (LIBs), owing to its low cost, environmental benignity, high specific capacity, and lower relative volume expansion compared with other alloying materials. However, both, the working and capacity fading processes are not yet consistently and comprehensively understood, which has largely hindered its development. In this study, the electrochemical alloying process of aluminum anodes with lithium is systematically studied by the combination of several inâ situ and exâ situ techniques, providing new insights into phase transitions, electrode dynamics, and surface chemistry. Particular attention is paid to the role of the Li-rich alloys (Li1+x Al). Its existence on the surface of the Al electrode is unexpectedly observed, and its growth in the electrode bulk is found to be strictly correlated with cell failure. Interestingly, cell failure can be delayed by choosing an appropriate electrolyte. This work contributes to a solid and comprehensive understanding of the puzzling Al (de-)lithiation processes, which is fundamental and highly enlightening for future research work on Al and other alloyed anodes.
RESUMEN
Aluminum, a cost-effective and abundant metal capable of alloying with Li up to around 1000â mAh g-1 , is a very appealing anode material for high energy density lithium-ion batteries (LIBs). However, despite repeated efforts in the past three decades, reports presenting stable cycling performance are extremely rare. This study concerns recent findings on the highly reversible (de)lithiation of a micro-sized Al anode (m-Al) by using bis(fluorosulfonyl)imide (FSI)-based electrolytes. By using this kind of electrolyte, m-Al can deliver a specific capacity over 900â mAh g-1 and superior Coulombic efficiency (96.8 %) to traditional carbonate- and glyme-based electrolytes (87.8 % and 88.1 %, respectively), which represents the best performance ever obtained for an Al anode without sophisticated structure design. The significantly improved electrochemical performance, which paves the way to realizing high-performance Al-based high energy density LIBs, can be attributed the peculiar solid-electrolyte interphase (SEI) formed by the FSI-containing electrolyte.
RESUMEN
Aqueous Na-ion batteries may offer a solution to the cost and safety issues of high-energy batteries. However, substantial challenges remain in the development of electrode materials and electrolytes enabling high performance and long cycle life. Herein, we report the characterization of a symmetric Na-ion battery with a NASICON-type Na2 VTi(PO4 )3 electrode material in conventional aqueous and "water-in-salt" electrolytes. Extremely stable cycling performance for 1000â cycles at a high rate (20â C) is found with the highly concentrated aqueous electrolytes owing to the formation of a resistive but protective interphase between the electrode and electrolyte. These results provide important insight for the development of aqueous Na-ion batteries with stable long-term cycling performance for large-scale energy storage.
RESUMEN
Tin oxide (SnO) is considered one of the most promising metal oxides for utilization as anode material in sodium ion batteries (SIBs), because of its ease of synthesis, high specific gravimetric capacity, and satisfactory cycling performance. However, to aim at practical applications, the Coulombic efficiency during cycling needs to be further improved, which requires a deeper knowledge of its working mechanism. Here, a microflower-shaped SnO material is synthesized by means of an ultrafast ionic liquid-assisted microwave method. The as-prepared SnO anode active material exhibits excellent cycling performance, good Coulombic efficiency as well as a large capacity delivered at low potential, which is fundamental to maximize the energy output of SIBs. These overall merits were never reported before for pure SnO anodes (i.e., not in a composite with, for example, graphene). Additionally, by combining ex situ XRD and XPS, it is clearly demonstrated for the first time that the Sn-Na alloy, which is formed during the initial sodium sodiation, desodiates in two successive but fully separated steps. Totally different from the previous report, the pristine SnO phase is not regenerated upon desodiation up to 3 V vs Na/Na+. The newly disclosed reaction route provides an alternative view of the complex reaction mechanism of these families of metal oxides for sodium ion batteries.
RESUMEN
LiMn2O4-based batteries exhibit severe capacity fading during cycling or storage in LiPF6-based liquid electrolytes, especially at elevated temperatures. Herein, a novel rigid-flexible gel polymer electrolyte is introduced to enhance the cyclability of LiMn2O4/graphite battery at elevated temperature. The polymer electrolyte consists of a robust natural cellulose skeletal incorporated with soft segment poly(ethyl α-cyanoacrylate). The introduction of the cellulose effectively overcomes the drawback of poor mechanical integrity of the gel polymer electrolyte. Density functional theory (DFT) calculation demonstrates that the poly(ethyl α-cyanoacrylate) matrices effectively dissociate the lithium salt to facilitate ionic transport and thus has a higher ionic conductivity at room temperature. Ionic conductivity of the gel polymer electrolyte is 3.3 × 10(-3) S cm(-1) at room temperature. The gel polymer electrolyte remarkably improves the cycling performance of LiMn2O4-based batteries, especially at elevated temperatures. The capacity retention after the 100th cycle is 82% at 55 °C, which is much higher than that of liquid electrolyte (1 M LiPF6 in carbonate solvents). The polymer electrolyte can significantly suppress the dissolution of Mn(2+) from surface of LiMn2O4 because of strong interaction energy of Mn(2+) with PECA, which was investigated by DFT calculation.
RESUMEN
Inspired by Taichi, we proposed rigid-flexible coupling concept and herein developed a highly promising solid polymer electrolyte comprised of poly (ethylene oxide), poly (cyano acrylate), lithium bis(oxalate)borate and robust cellulose nonwoven. Our investigation revealed that this new class solid polymer electrolyte possessed comprehensive properties in high mechanical integrity strength, sufficient ionic conductivity (3 × 10(-4) S cm(-1)) at 60°C and improved dimensional thermostability (up to 160°C). In addition, the lithium iron phosphate (LiFePO4)/lithium (Li) cell using such solid polymer electrolyte displayed superior rate capacity (up to 6 C) and stable cycle performance at 80°C. Furthermore, the LiFePO4/Li battery could also operate very well even at an elevated temperature of 160°C, thus improving enhanced safety performance of lithium batteries. The use of this solid polymer electrolyte mitigates the safety risk and widens the operation temperature range of lithium batteries. Thus, this fascinating study demonstrates a proof of concept of the use of rigid-flexible coupling solid polymer electrolyte toward practical lithium battery applications with improved reliability and safety.
RESUMEN
A sustainable, heat-resistant and flame-retardant cellulose-based composite nonwoven has been successfully fabricated and explored its potential application for promising separator of high-performance lithium ion battery. It was demonstrated that this flame-retardant cellulose-based composite separator possessed good flame retardancy, superior heat tolerance and proper mechanical strength. As compared to the commercialized polypropylene (PP) separator, such composite separator presented improved electrolyte uptake, better interface stability and enhanced ionic conductivity. In addition, the lithium cobalt oxide (LiCoO2)/graphite cell using this composite separator exhibited better rate capability and cycling retention than that for PP separator owing to its facile ion transport and excellent interfacial compatibility. Furthermore, the lithium iron phosphate (LiFePO4)/lithium cell with such composite separator delivered stable cycling performance and thermal dimensional stability even at an elevated temperature of 120°C. All these fascinating characteristics would boost the application of this composite separator for high-performance lithium ion battery.