Synergistic Electrode and Electrolyte Polarities Lead to Outstanding Organic Potassium-based Batteries.

Organic materials are promising as battery electrodes due to their flexible design, low cost, and sustainability. Although high electrolyte concentrations are known to suppress organic cathode dissolution, the organic cathode solubility depends on the interplay between the electrode and electrolyte polarities, which remains unexplored. Here, we elucidate the delicate interplay of electrode and electrolyte polarities to achieve stable cycling of organic cathode.

Multiple Electron Transfers Enable High-Capacity Cathode Through Stable Anionic Redox.

Single-electron transfer, low alkali metal contents, and large-molecular masses limit the capacity of cathodes. This study uses a cost-effective and light-molecular-mass orthosilicate material, KFeSiO, with a high initial potassium content, as a cathode for potassium-ion batteries to enable the transfer of more than one electron. Despite the limited valence change of Fe ions during cycling, KFeSiO can undergo multiple electron transfers via successive oxygen anionic redox reactions to generate a high reversible capacity.

Commercial Cellulosic Paper-Based Solid Electrolyte for High-Temperature Lithium-Sulfur Batteries.

Solid-state lithium-sulfur (Li-S) batteries show promise for future electric mobility due to their high energy density potential. However, high internal impedance, Li polysulfide shuttling, and dendrite formation exist. Herein, we present a Li-rich cellulosic solid-state electrolyte (SSE) that, when paired with a sulfurized polyacrylonitrile (SPAN) cathode, leads to durable Li-S batteries for use in the room temperature to 50 °C range.

Cosolvent electrolyte chemistries for high-voltage potassium-ion battery.

The poor oxidation resistance of traditional electrolytes has hampered the development of high-voltage potassium-ion battery technology. Here, we present a cosolvent electrolyte design strategy to overcome the high-voltage limitations of potassium-ion electrolyte chemistries. The cosolvent electrolyte breaks the dissolution limitation of the salt through ion-dipole interactions, significantly enlarging the anion-rich solvation clusters, as verified by the synchrotron-based wide-angle X-ray scattering experiments.

Structural, Optical, and Magnetic Properties of Brownmillerite KBiFeO and KBiFeTiO via Reactive Templated Method.

Brownmillerite KBiFeO (KBFO) and KbiFeTiO (KBFTO) ceramics were synthesized using the prereacted nanopowders of KFeO (KFO) and BiFeO (BFO), and KFO and BiFeTiO (BFTO), respectively, via the reactive templated method. The powder X-ray diffraction patterns confirmed the monoclinic phase of the KBFO and KBFTO samples. The incorporation of Ti at Fe site prevented the formation of a secondary phase (BiFeO) in the KBFTO sample.

Permeable void-free interface for all-solid-state alkali-ion polymer batteries.

All-solid-state batteries suffer from a loss of contact between the electrode and electrolyte particles, leading to poor cyclability. Here, a void-free ion-permeable interface between the solid-state polymer electrolyte and electrode is constructed in situ during cycling using charge/discharge voltage as the stimulus. During the charge-discharge, the permeation phase fills the voids at the interface and penetrates the electrode, forming strong bonds with the cathode and effectively mitigating the contact problem.

Rational Regulation of High-Voltage Stability in Potassium Layered Oxide Cathodes.

Layered oxide cathode materials may undergo irreversible oxygen loss and severe phase transitions during high voltage cycling and may be susceptible to transition metal dissolution, adversely affecting their electrochemical performance. Here, to address these challenges, we propose synergistic doping of nonmetallic elements and in situ electrochemical diffusion as potential solution strategies. Among them, the distribution of the nonmetallic element fluorine within the material can be regulated by doping boron, thereby suppressing manganese dissolution through surface enrichment of fluorine.

Sustainable Electrolytes: Design Principles and Recent Advances.

Today, rechargeable batteries are omnipresent and essential for our existence. In order to improve the electrochemical performance of electric fields, the introduction of electrolytes with fluorine (F)-based inorganic elemental compositions is a direction of exploration. However, most fluorocarbons have a high global warming potential and ozone depletion potential, which do not meet the sustainability requirements of the battery industry.

Bio-inspired carbon electrodes for metal-ion batteries.

Carbon has been widely used as an electrode material in commercial metal-ion batteries (MIBs) because of its desirable electrical, mechanical, and physical properties. Still, traditional carbon electrodes suffer from limited mechanical stability and electrochemical performance in MIBs. Drawing inspiration from biological species, the carbon allotropes, such as fullerenes, carbon nanotubes, and graphene, can be engineered into mechanically robust, highly conductive frameworks with enhanced ion storage and transport capabilities for MIBs.

Molecular modulation strategies for two-dimensional transition metal dichalcogenide-based high-performance electrodes for metal-ion batteries.

In the past few decades, great efforts have been made to develop advanced transition metal dichalcogenide (TMD) materials as metal-ion battery electrodes. However, due to existing conversion reactions, they still suffer from structural aggregation and restacking, unsatisfactory cycling reversibility, and limited ion storage dynamics during electrochemical cycling. To address these issues, extensive research has focused on molecular modulation strategies to optimize the physical and chemical properties of TMDs, including phase engineering, defect engineering, interlayer spacing expansion, heteroatom doping, alloy engineering, and bond modulation.

Building Stable Solid-State Potassium Metal Batteries.

Solid-state potassium metal batteries (SPMBs) are promising candidates for the next generation of energy storage systems for their low cost, safety, and high energy density. However, full SPMBs are not yet reported due to the K dendrites, interfacial incompatibility, and limited availability of suitable solid-state electrolytes. Here, stable SPMBs using a new iodinated solid polymer electrolyte (ISPE) are presented.

Green Ether Electrolytes for Sustainable High-voltage Potassium Ion Batteries.

Ether-based electrolytes are promising for secondary batteries due to their good compatibility with alkali metal anodes and high ionic conductivity. However, they suffer from poor oxidative stability and high toxicity, leading to severe electrolyte decomposition at high voltage and biosafety/environmental concerns when electrolyte leakage occurs. Here, we report a green ether solvent through a rational design of carbon-chain regulation to elicit steric hindrance, such a structure significantly reducing the solvent's biotoxicity and tuning the solvation structure of electrolytes.

Entropy-Tuned Layered Oxide Cathodes for Potassium-Ion Batteries.

The manganese-based layered oxides as a promising cathode material for potassium ion batteries (PIBs) have attracted considerable interest owing to their simple synthesis, high specific capacity, and low cost. However, due to the irreversible phase transition and the Jahn-Teller distortion of the Mn , its application in potassium ion batteries is limited, leading to slow potassium ion kinetics and severe capacity attenuation. Here, entropy-tuning by changing the content of cathode material composition is proposed to address the above challenges.

Trimming the Degrees of Freedom via a K Flux Rectifier for Safe and Long-Life Potassium-Ion Batteries.

High degrees of freedom (DOF) for K movement in the electrolytes is desirable, because the resulting high ionic conductivity helps improve potassium-ion batteries, yet requiring support from highly free and flammable organic solvent molecules, seriously affecting battery safety. Here, we develop a K flux rectifier to trim K ion's DOF to 1 and improve electrochemical properties. Although the ionic conductivity is compromised in the K flux rectifier, the overall electrochemical performance of PIBs was improved.

Ultrafast Carrier Drift Transport Dynamics in CsPbI Perovskite Nanocrystalline Thin Films.

We study the early time carrier drift dynamics in CsPbI nanocrystal thin films with a sub 25 ps time resolution. Prior to trapping, carriers exhibit band-like transport characteristics, which is similar to those of traditional semiconductor solar absorbers including Si and GaAs due to optical phonon and carrier scattering at high temperatures. In contrast to the popular polaron scattering mechanism, the CsPbI nanocrystal thin film demonstrates the strongest optical phonon scattering mechanism among other inorganic-organic hybrid perovskites, Si, and GaAs.

Co-activation for enhanced K-ion storage in battery anodes.

The relative natural abundance of potassium and potentially high energy density has established potassium-ion batteries as a promising technology for future large-scale global energy storage. However, the anodes' low capacity and high discharge platform lead to low energy density, which impedes their rapid development. Herein, we present a possible co-activation mechanism between bismuth (Bi) and tin (Sn) that enhances K-ion storage in battery anodes.

Electrochemical Performance of Polymer-Derived Silicon-Oxycarbide/Graphene Nanoplatelet Composites for High-Performance Li-Ion Batteries.

Amorphous polymer-derived silicon-oxycarbide (SiOC) ceramics have a high theoretical capacity and good structural stability, making them suitable anode materials for lithium-ion batteries. However, SiOC has low electronic conductivity, poor transport properties, low initial Couloumbic efficiency, and limited rate capability. Therefore, there is an urgent need to explore an efficient SiOC-based anode material that could mitigate the abovementioned limitations.

Quasi-Solid Aqueous Electrolytes for Low-Cost Sustainable Alkali-Metal Batteries.

Aqueous electrolytes are highly important for batteries due to their sustainability, greenness, and low cost. However, the free water molecules react violently with alkali metals, rendering the high-capacity of alkali-metal anodes unusable. Here, water molecules are confined in a carcerand-like network to build quasi-solid aqueous electrolytes (QAEs) with reduced water molecules' freedom and matched with the low-cost chloride salts.

Selective Potassium Deposition Enables Dendrite-Resistant Anodes for Ultrastable Potassium-Metal Batteries.

Instability at the solid electrolyte interface (SEI) and uncontrollable growth of potassium dendrites have been pressing issues for potassium-ion batteries. Herein, a self-supporting electrode composed of bismuth and nitrogen-doped reduced graphene oxide (Bi /NrGO) is designed as an anode host for potassium-metal batteries. Following the molten potassium diffusion into Bi /NrGO, the resulting K@Bi /NrGO exhibits unique hollow pores that provide K -diffusion channels and deposition space to buffer volume expansion, thus maintaining the electrode structure and SEI stability.

Phase-engineered cathode for super-stable potassium storage.

The crystal phase structure of cathode material plays an important role in the cell performance. During cycling, the cathode material experiences immense stress due to phase transformation, resulting in capacity degradation. Here, we show phase-engineered VO as an improved potassium-ion battery cathode; specifically, the amorphous VO exhibits superior K storage ability, while the crystalline M phase VO cannot even store K ions stably.

Cyclic-anion salt for high-voltage stable potassium-metal batteries.

Electrolyte anions are critical for achieving high-voltage stable potassium-metal batteries (PMBs). However, the common anions cannot simultaneously prevent the formation of 'dead K' and the corrosion of Al current collector, resulting in poor cycling stability. Here, we demonstrate cyclic anion of hexafluoropropane-1,3-disulfonimide-based electrolytes that can mitigate the 'dead K' and remarkably enhance the high-voltage stability of PMBs.

Generating and Capturing Secondary Hot Carriers in Monolayer Tungsten Dichalcogenides.

It remains challenging to capture and investigate the drift dynamics of primary hot carriers because of their ultrashort lifetime (∼200 fs). Here we report a new mechanism for hot carrier (∼25 ps) generation in monolayer transition metal dichalcogenides such as WS and WSe, triggered by the Auger recombination of trions and biexcitons. Using ultrafast photocurrent spectroscopy, we measured and characterized the photocurrent stemming from the Auger recombination of trions and biexcitons in WS and WSe.

Infrared Transmission Characteristics of Phase Transitioning VO on Various Substrates.

Infrared transmission characteristics of VO thin films synthesized on multiple substrates, using a low-pressure direct oxidation technique, have been characterized. Material characterization of these films indicates high material quality, which resulted in large variation of electrical and optical properties at phase transition. A change in optical transmissivity greater than 80% was observed for these films utilizing infrared (IR) laser illumination at 1550 nm.

High-Potential Cathodes with Nitrogen Active Centres for Quasi-Solid Proton-Ion Batteries.

Although proton-ion batteries have received considerable attention owing to their reliability, safety, toxin-free nature, and low cost, their development remains in the early stages because of lacking proper electrolytes and cathodes for facilitating a high output voltage and stable cycle performance. We present a novel cathode based on active nitrogen centre, which provides a flat discharge plateau at 1 V with a capacity of 115 mAh g and excellent stability. Moreover, a quasi-solid electrolyte was developed to overcome the issue of corrosion, broaden the potential window of the electrolyte, and prevent the active material from dissolving.

Prospects of Electrode Materials and Electrolytes for Practical Potassium-Based Batteries.

Potassium-ion batteries (PIBs) have attracted tremendous attention because of their high energy density and low-cost. As such, much effort has focused on developing electrode materials and electrolytes for PIBs at the material levels. This review begins with an overview of the high-performance electrode materials and electrolytes, and then evaluates their prospects and challenges for practical PIBs to penetrate the market.