Stable Cycling of Na Metal Batteries at Ultrahigh Capacity.

The development of sodium metal batteries has long been impeded by dendrite formation issues. State-of-the-art strategies, exemplified by sodiophilic hosting/seeding layers, have demonstrated great success in suppressing dendrite formation. However, addressing high-capacity applications (>10 mAh cm) remains a significant challenge.

Cyclic Ether-Based Electrolyte with a Weak Solvation Structure for Advanced Potassium Metal Batteries.

Potassium metal batteries (PMBs) are promising candidates for large-scale energy storage. Conventional carbonate electrolytes exhibit unsatisfactory thermodynamic stability against potassium (K) metal anode. Linear ether is widely adopted because of its compatibility with K metal, but the poor oxidation stability restricts the application with high-voltage cathodes.

Deciphering the Formation and Accumulation of Solid-Electrolyte Interphases in Na and K Carbonate-Based Batteries.

The continuous solid-electrolyte interphase (SEI) accumulation has been blamed for the rapid capacity loss of carbon anodes in Na and K ethylene carbonate (EC)/diethyl carbonate (DEC) electrolytes, but the understanding of the SEI composition and its formation chemistry remains incomplete. Here, we explain this SEI accumulation as the continuous production of organic species in solution-phase reactions. By comparing the NMR spectra of SEIs and model compounds we synthesized, alkali metal ethyl carbonate (MEC, M = Na or K), long-chain alkali metal ethylene carbonate (LCMEC, M = Na or K), and poly(ethylene oxide) (PEO) oligomers with ethyl carbonate ending groups are identified in Na and K SEIs.

Investigating K Storage Behavior of Highly Graphitized Carbon Fibers as Anodes for a Potassium-Ion Battery.

Many problems of potassium-ion batteries (PIBs) are hidden under a low mass load of the active material. However, developing research based on areal capacity is challenging for PIBs, due to the lack of an anode capable of delivering a stable capacity of more than 1 mAh cm. This work investigates the K storage behavior of highly graphitized carbon fibers (HG-CF), which exhibit automatic structural adjustments to mitigate voltage polarization.

Key Factor Determining the Cyclic Stability of the Graphite Anode in Potassium-Ion Batteries.

Graphite is the most commonly used anode material for not only commercialized lithium-ion batteries (LIBs) but also the emerging potassium-ion batteries (PIBs). However, the graphite anode in PIBs using traditional dilute ester-based electrolyte systems shows obvious capacity fading, which is in contrast with the extraordinary cyclic stability in LIBs. More interestingly, the graphite in concentrated electrolytes for PIBs exhibits outstanding cyclic stability.

Mechanistic Insight into Ultrafast Kinetics of Sodium Cointercalation in Few-Layer Graphitic Carbon.

Fast-charging sodium ion batteries remain deeply challenged by the lack of suitable carbonaceous anodes that exhibit intercalation plateau with fast kinetics. Here we develop a few-layer graphitic carbon with nanoscale architecture, which enables shortened Na ion diffusion path and fast formation of fully intercalated phase at the same time. Combined in situ Raman and electrochemical test reveal that this graphitic carbon with highly crystalline few layers follows surface-controlled intercalation rather than typical diffusion-controlled kinetics observed in natural graphite.

A free-standing 3D porous all-ceramic cathode for high capacity, long cycle life Li-O batteries.

The all-ceramic RuO@LaCaCuO membrane cathode contributes to an ultra-high capacity of 21 518 mA h g over 110 cycles in Li-O batteries. A simple infiltration technique is effective for obtaining a highly active supported RuO catalyst, and a solvent with a high donor number should be preferentially chosen because it contributes to a much higher capacity.

Polyvinylpyrrolidone-Bridged Prussian Blue/rGO Composite as a High-Performance Cathode for K-Ion Batteries.

Prussian blue (PB) is a very promising cathode for K-ion batteries but its low electronic conductivity and deficiencies in the framework aggravate electrochemical performances. Compositing with conductive reduced graphene oxide (rGO) is an effective solution to address this problem. Nevertheless, little attention was paid to the loss of oxygen-containing functional groups on the rGO substrate during the compositing process, which weakens the interaction between PB and rGO and leads to poor electrochemical performance of PB/rGO.

A highly concentrated electrolyte for high-efficiency potassium metal batteries.

We report a highly concentrated electrolyte consisting of 4 M potassium bis(fluorosulfonyl)imide (KFSI) in diethylene glycol dimethyl ether (DEGDME). This new electrolyte enables stable cycling of K metal anodes with a high CE (over 98% over 400 cycles), and excellent capacity retention (99.7% after 500 cycles) of K||potassium Prussian blue (KPB) batteries.

A Graphite Intercalation Composite as the Anode for the Potassium-Ion Oxygen Battery in a Concentrated Ether-Based Electrolyte.

Nowadays, alkali metal-oxygen batteries such as Li-, Na-, and K-O batteries have been investigated extensively because of their ultrahigh energy density. However, the oxygen crossover of oxygen batteries and the intrinsic drawbacks of the metal anodes (i.e.

Correlation between Microstructure and Potassium Storage Behavior in Reduced Graphene Oxide Materials.

Potassium-ion batteries (PIBs) are considered to be potential alternatives to the conventional lithium-ion batteries (LIBs) due to the similar working mechanism and abundant potassium (K) resource. However, it still remains challenging to directly apply commercial graphite anodes for PIBs owing to the large K ions, which may impede the electrochemical intercalation of K ions into the graphite interlayer and result in a poor cyclic stability and rate capability. Reduced graphene oxide (rGO) has shown remarkable electrochemical performance as an anode material for PIBs due to the fact that rGO possesses more active sites with an enlarged interlayer distance.

Utilizing an autogenously protective atmosphere to synthesize a Prussian white cathode with ultrahigh capacity-retention for potassium-ion batteries.

A facile, low-cost precipitation method, utilizing an autogenously protective atmosphere without the assistance of an inert atmosphere, is proposed to synthesize nano-sized Prussian white K1.62Fe[Fe(CN)6]0.92·0.

Room-temperature liquid metal-based anodes for high-energy potassium-based electrochemical devices.

A liquid Na-K alloy is adsorbed onto a super-aligned carbon nanotube membrane (denoted CM) at room temperature, which is driven by capillary force, fabricating a flexible CM@NaK membrane. The anode directly using the CM@NaK membrane exhibits a smooth electrode-electrolyte (liquid-liquid) interface, contributing to fast ion transport and a dendrite-free stripping/plating process.

Controllable Electrochemical Fabrication of KO-Decorated Binder-Free Cathodes for Rechargeable Lithium-Oxygen Batteries.

Understanding the electrochemical property of superoxides in alkali metal oxygen batteries is critical for the design of a stable oxygen battery with high capacity and long cycle performance. In this work, a KO-decorated binder-free cathode is fabricated by a simple and efficient electrochemical strategy. KO nanoparticles are uniformly coated on the carbon nanotube film (CNT-f) through a controllable discharge process in the K-O battery, and the KO-decorated CNT-f is innovatively introduced into the Li-O battery as the O diffusion electrode.

Molecular Sieve Induced Solution Growth of LiO in the Li-O Battery with Largely Enhanced Discharge Capacity.

The formation of the insulated film-like discharge products (LiO) on the surface of the carbon cathode gradually hinders the oxygen reduction reaction (ORR) process, which usually leads to the premature death of the Li-O battery. In this work, by introducing the molecular sieve powder into the ether electrolyte, the Li-O battery exhibits a largely improved discharge capacity (63 times) compared with the one in the absence of this inorganic oxide additive. Meanwhile, XRD and SEM results qualitatively demonstrate the generation of the toroid LiO as the dominated discharge products, and the chemical titration quantifies a higher yield of the LiO with the presence of the molecular sieve additive.

Investigations of Si Thin Films as Anode of Lithium-Ion Batteries.

Amorphous silicon thin films having various thicknesses were investigated as a negative electrode material for lithium-ion batteries. Electrochemical characterization of the 20 nm thick thin silicon film revealed a very low first cycle Coulombic efficiency, which can be attributed to the silicon oxide layer formed on both the surface of the as-deposited Si thin film and the interface between the Si and the substrate. Among the investigated films, the 100 nm Si thin film demonstrated the best performance in terms of first cycle efficiency and cycle life.

Dendrite-Free Potassium-Oxygen Battery Based on a Liquid Alloy Anode.

The safety issue caused by the dendrite growth is not only a key research problem in lithium-ion batteries but also a critical concern in alkali metal (i.e., Li, Na, and K)-oxygen batteries where a solid metal is usually used as the anode.

A lithium-oxygen battery based on lithium superoxide.

Batteries based on sodium superoxide and on potassium superoxide have recently been reported. However, there have been no reports of a battery based on lithium superoxide (LiO2), despite much research into the lithium-oxygen (Li-O2) battery because of its potential high energy density. Several studies of Li-O2 batteries have found evidence of LiO2 being formed as one component of the discharge product along with lithium peroxide (Li2O2).

The Effect of Potassium Impurities Deliberately Introduced into Activated Carbon Cathodes on the Performance of Lithium-Oxygen Batteries.

Rechargeable lithium-air (Li-O2) batteries have drawn much interest owing to their high energy density. We report on the effect of deliberately introducing potassium impurities into the cathode material on the electrochemical performance of a Li-O2 battery. Small amounts of potassium introduced into the activated carbon (AC) cathode material in the synthesis process are found to have a dramatic effect on the performance of the Li-O2 cell.

Raman Evidence for Late Stage Disproportionation in a Li-O2 Battery.

Raman spectroscopy is used to characterize the composition of toroids formed in an aprotic Li-O2 cell based on an activated carbon cathode. The trends in the Raman data as a function of discharge current density and charging cutoff voltage provide evidence that the toroids are made up of outer LiO2-like and inner Li2O2 regions, consistent with a disproportionation reaction occurring in the solid phase. The LiO2-like component is found to be associated with a new Raman peak identified in the carbon stretching region at ∼1505 cm(-1), which appears only when the LiO2 peak at 1123 cm(-1) is present.

Interfacial effects on lithium superoxide disproportionation in Li-O₂ batteries.

During the cycling of Li-O2 batteries the discharge process gives rise to dynamically evolving agglomerates composed of lithium-oxygen nanostructures; however, little is known about their composition. In this paper, we present results for a Li-O2 battery based on an activated carbon cathode that indicate interfacial effects can suppress disproportionation of a LiO2 component in the discharge product. High-intensity X-ray diffraction and transmission electron microscopy measurements are first used to show that there is a LiO2 component along with Li2O2 in the discharge product.

Disproportionation in Li-O2 batteries based on a large surface area carbon cathode.

In this paper we report on a kinetics study of the discharge process and its relationship to the charge overpotential in a Li-O2 cell for large surface area cathode material. The kinetics study reveals evidence for a first-order disproportionation reaction during discharge from an oxygen-rich Li2O2 component with superoxide-like character to a Li2O2 component. The oxygen-rich superoxide-like component has a much smaller potential during charge (3.

Evidence for lithium superoxide-like species in the discharge product of a Li-O2 battery.

We report on the use of a petroleum coke-based activated carbon (AC) with very high surface area for a Li-O(2) battery cathode without the use of any additional metal catalysts. Electrochemical measurement in a tetra(ethylene) glycol dimethyl ether-lithium triflate (TEGDME-LiCF(3)SO(3)) electrolyte results in two voltage plateaus during charging at 3.2-3.