Ever‐increasing energy demands call for alternative energy storage technologies with balanced performance and cost characteristics to meet current and emerging applications. Dual‐ion batteries (DIBs) ...are considered particularly attractive owing to the potentially high specific energy, a rich variety of charge carrier combinations, and the applicability of metal‐free cathode and earth‐abundant anode materials. However, their performance falls far below expectations because of a large excess of solvent needed to dissolve electroactive species that induces side reactions and contributes parasitic weight, which penalizes the reversible capacity and cell‐level energy density. Herein, a solvent‐free DIB utilizing a binary alkali metal molten salt based on bis(fluorosulfonyl)amide as the electrolyte to solve these issues is demonstrated. The cell (NaK‐DIB) operates in a temperature range of 90–120 °C and exhibits high theoretical energy densities of 246 Wh kg−1 and 533 Wh L−1 based on active materials and capacity‐matched electrolyte, far surpassing those of reported DIBs. Further improvements could realize affordable grid‐scale energy storage.
Solvent‐free dual‐ion batteries of both high energy density and high safety are demonstrated with the utilization of an inorganic molten salt as the electrolyte. The new cell chemistry inherits the dendrite‐free characteristic of liquid metal anodes and the favored electrode kinetics and thermal robustness of molten‐salt batteries, paving the way for affordable large‐scale energy storage.
Halogen redox couples offer several advantages for energy storage such as low cost, high solubility in water, and high redox potential. However, the operational complexity of storing halogens at the ...oxidation state via liquid‐phase media hampers their widespread application in energy‐storage devices. Herein, an aqueous zinc–dual‐halogen battery system taking the advantages of redox flow batteries (inherent scalability) and intercalation chemistry (high capacity) is designed and fabricated. To enhance specific energy, the designed cell exploits both bromine and chlorine as the cathode redox couples that are present as halozinc complexes in a newly developed molten hydrate electrolyte, which is distinctive to the conventional zinc–bromine batteries. Benefiting from the reversible uptake of halogens at the graphite cathode, exclusive reliance on earth‐abundant elements, and membrane‐free and possible flow‐through configuration, the proposed battery can potentially realize high‐performance massive electric energy storage at a reasonable cost.
A new aqueous zinc‐based battery exploiting dual redox couples of Br0/Br− and Cl0/Cl− at a graphite cathode is presented. The battery achieves both a high average working voltage of 1.71 V and a remarkable capacity of 257 mAh g−1 at 0.1 A g−1. This work provides an affordable, easily scalable, membrane‐free, and high‐performance energy‐storage system.
The limited cyclability and inferior Coulombic efficiency of graphite negative electrodes have been major impediments to their practical utilization in potassium-ion batteries (PIBs). Herein, for the ...first time, potassium difluorophosphate (KDFP) electrolyte additive is demonstrated as a viable solution to these bottlenecks by facilitating the formation of a stable and K+-conducting solid–electrolyte interphase (SEI) on graphite. The addition of 0.2 wt % KDFP to the electrolyte results in significant improvements in the (de)potassiation kinetics, capacity retention (76.8% after 400 cycles with KDFP vs 27.4% after 100 cycles without KDFP), and average Coulombic efficiency (∼99.9% during 400 cycles) of the graphite electrode. Moreover, the KDFP-containing electrolyte also enables durable cycling of the K/K symmetric cell at higher efficiencies and lower interfacial resistance as opposed to the electrolyte without KDFP. X-ray diffraction and Raman spectroscopy analyses have confirmed the reversible formation of a phase-pure stage-1 potassium–graphite intercalation compound (KC8) with the aid of KDFP. The enhanced electrochemical performance by the KDFP addition is discussed based on the analysis of the SEI layer on graphite and K metal electrodes by X-ray photoelectron spectroscopy.
Sodium manganese orthosilicate, Na2MnSiO4, was synthesized by a sol–gel method and investigated for use as a positive electrode material for Na secondary batteries using NaFSA–C3C1pyrrFSA ...(FSA=bis(fluorosulfonyl)amide anion and C3C1pyrr=N-methyl-N-propylpyrrolidinium cation) ionic liquid electrolyte in the temperature range 298–363K. Carbon coating and elevation of operational temperatures significantly improved the electrode performance. A reversible capacity of 125mAhg−1 (90% of the theoretical value based on a one-electron transfer process) was found at a rate of C/10 (13.9mAg−1) within 2.0–4.0V at 363K, with an acceptably high rate capability. Na2MnSiO4 became amorphous upon the electrochemical removal of sodium, exhibiting a similar behavior as its lithium equivalent. Both Na2MnSiO4 and its desodiated form (Na0.8MnSiO4) possess remarkable thermal stability, suggesting their safety characteristic.
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Lithium (Li) metal anodes (LMAs) are considered to be the holy grail of electrodes to enable advanced battery chemistry for energy‐intensive applications. However, the formation of Li dendrites and ...their intricate interplay with the solid electrolyte interphase (SEI) remain unclear to date. Herein, a simple yet efficient methodology for in situ transmission electron microscopy (TEM) observation is reported, and the relationship between the SEI chemistry and the morphology of LMAs is unraveled by a combination of TEM imaging and selected area electron diffraction analysis in an unprecedented way. The authors find that the coexistence of LiF and Li3N in the SEI layer helps realize dendrite‐free Li deposition and directly visualize the deposition–dissolution behavior of individual Li deposits with different microstructures. The approach should be applicable to scrutinize a broad range of interfacial reactions in nonvolatile electrolytes (e.g., ionic liquid, glass‐, and ceramic‐based electrolytes) relevant to future energy storage devices, including magnesium secondary batteries.
A new transmission electron microscopy methodology is presented to accurately monitor the morphology evolution of lithium metal anodes and their solid electrolyte interphases (SEIs) under realistic operation conditions. This method combines the advantages of conventional open‐cell (high‐resolution visualization) and liquid‐cell approaches (better mimicking a real battery), which will expedite the development of next‐generation electrode materials.
Abstract
Honeycomb layered oxides constitute an emerging class of materials that show interesting physicochemical and electrochemical properties. However, the development of these materials is still ...limited. Here, we report the combined use of alkali atoms (Na and K) to produce a mixed-alkali honeycomb layered oxide material, namely, NaKNi
2
TeO
6
. Via transmission electron microscopy measurements, we reveal the local atomic structural disorders characterised by aperiodic stacking and incoherency in the alternating arrangement of Na and K atoms. We also investigate the possibility of mixed electrochemical transport and storage of Na
+
and K
+
ions in NaKNi
2
TeO
6
. In particular, we report an average discharge cell voltage of about 4 V and a specific capacity of around 80 mAh g
–1
at low specific currents (i.e., < 10 mA g
–1
) when a NaKNi
2
TeO
6
-based positive electrode is combined with a room-temperature NaK liquid alloy negative electrode using an ionic liquid-based electrolyte solution. These results represent a step towards the use of tailored cathode active materials for “dendrite-free” electrochemical energy storage systems exploiting room-temperature liquid alkali metal alloy materials.
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