Potassium Metal Research Articles

Advanced 3D-structured electrode for potassium metal anodes

The potassium (K) metal anode, following the "Holy Grail" Li metal anode, is one of the most promising anode materials for next-generation batteries. In comparison with Li, K exhibits even more pronounced energy storage properties. However, it suffers from similar challenges as most alkali metal anodes, such as safety and cyclability issues. Borrowing strategies from Li/Na metal anodes, the three-dimensional (3D)-structured current collector has proven to be a universal and effective strategy. This study examines the recent research progress of 3D-structured electrodes for K metal anodes, focusing on the most commonly used host materials, including carbon-, metal-, and MXene-related electrode materials. Finally, existing challenges, various perspectives on the rational design of K metal anodes, and the future development of K batteries are presented.

Design of a potassiophilic 3D conductive scaffold potassium anode (3D-CTZ@K) with dendrite-free and high energy-power density in potassium metal batteries

A 3D-CTZ@K anode was constructed by infusion of molten K metal into a 3D-CTZ scaffold to achieve extraordinary cycle stability with high rate capability. The 3D-CTZ@K//PB full battery exhibits an unprecedented energy and power densities.

Allosteric and Electrostatic Cooperativity in a Heteroditopic Halogen Bonding Receptor System.

A halogen bonding (XB) heteroditopic receptor, consisting of a 1,3-bis-iodo-triazole benzene XB anion binding site covalently appended via a flexible methylene group with two benzo-15-crown-5 (B15C5) cation binding moieties, and its hydrogen bonding receptor analogue, are used to delineate the mechanisms of cooperativity for alkali metal halide ion-pair recognition. Extensive cation, anion and ion-pair 1 H NMR titration investigations demonstrate the combination of allosteric pre-organisation, via 1 : 1 stoichiometric intramolecular potassium and rubidium metal cation bis-B15C5 sandwich complexation, in concert with favourable electrostatics and XB potency, results in a remarkable enhancement of halide anion binding affinity by a factor of at least 700. By contrast, a notably diminished halide anion affinity enhancement factor of just 15 is observed with the corresponding 1 : 1 stoichiometric sodium cation complexed receptor system, where the smaller sized cation singly occupies one B15C5 unit and only an electrostatic contribution to cooperativity is possible. These observations serve to illustrate that allosteric pre-organisation capability, electrostatic attraction and XB mediated anion recognition are important strategic design features to incorporate in future high-fidelity heteroditopic ion-pair receptor development.

Stable Solid Electrolyte Interface Achieved by Separator Surface Modification for High-Performance Anode-free Potassium Metal Batteries

Anode-free lithium and sodium metal batteries (N:P = 0:1) are regarded as a promising method to significantly improve the energy density of rechargeable batteries. Studies concerning separator modification of anode-free K metal batteries (AF-KMBs) are rare. Herein, reduced graphene oxide (rGO) served as a special coating layer with high conductivity and porosity to achieve high-performance AF-KMBs with good dynamic characteristics. In addition, the porosity of rGO can help form a stable solid electrolyte interface (SEI) as a soft host on Cu foil for the “K-free” anode and improve the cycling life of the AF-KMBs. As a result, the obtained AF-KMBs paired with a K0.51V2O5 cathode (Cu/rGO/K0.51V2O5) can maintain a high specific capacity of 65 mAh g–1 even after 70 cycles at 0.5 A g–1. Thus, the feasibility of AF-KMBs is a proposed future research direction.

Processable Potassium-Carbon Nanotube Film with a Three-Dimensional Structure for Ultrastable Metallic Potassium Anodes.

K metal holds great promise as the ultimate anode candidate for K-ion batteries because of its high theoretical capacity and low operating potential. However, due to its high viscosity and poor mechanical processability, it remains challenging to manufacture potassium anodes with precise parameters by a simple and executable method. In this work, a high-performance potassium-carbon nanotubes (K@CNTs) composite film electrode with a three-dimensional (3D) skeleton and superior processability is prepared by simply incorporating CNTs into molten potassium. The in situ potassiation reaction between CNTs and molten K formed potassium carbide (KC8) so as to obtain a solid-liquid mixture, which can reduce the surface tension of molten potassium and promote the preparation of the K@CNTs film electrode. The composite electrode can be molded into a variety of shapes and thicknesses in accurate dimensions. The porous, well-conducting CNTs act as a 3D skeleton uniformly distributed in the K metal, providing adequate surface and space to accommodate and attract K metal, thereby inhibiting the growth of the potassium dendrites and the volume expansion upon cycling. As a result, the K@CNTs composite anode exhibits excellent cyclability and rate capability in both symmetric and full cells. The superior processability and excellent electrochemical performance make this composite an ideal anode candidate for commercial applications in potassium metal batteries.

A room-temperature-stable electride and its reactivity: Reductive benzene/pyridine couplings and solvent-free Birch reductions

<h2>Summary</h2> In this work, we report the synthesis of a room-temperature-stable electride (RoSE) reagent, namely K⁺(LiHMDS)e⁻ (<b>1</b>) (HMDS: 1,1,1,3,3,3-hexamethyldisilazide), from accessible starting materials (potassium metal and LiHMDS) via mechanochemical ball milling at 20 mmol scale. Despite its amorphous nature, the presence of anionic electrons in <b>1</b>, key diagnostic criteria for an electride, was confirmed by both experimental and computational studies. Therefore, by definition, <b>1</b> is an electride. Utilizing its anionic electrons, electride reagent <b>1</b> exhibited a versatile reactivity profile that includes (1) mediation of C–H activation and C–C coupling of benzene and pyridine and (2) mediation of solvent-free Birch reduction. This work proves the concept of facile mechanochemical synthesis of a room-temperature-stable electride, and it introduces electride <b>1</b> to the synthetic chemistry community as a versatile reagent.

Magnetic Hydrogel Composite for Wastewater Treatment.

Nanocomposite hydrogels are highly porous colloidal structures with a high adsorption capacity, making them promising materials for wastewater treatment. In particular, magnetic nanoparticle (MNP) incorporated hydrogels are an excellent adsorbent for aquatic pollutants. An added advantage is that, with the application of an external magnetic field, magnetic hydrogels can be collected back from the wastewater system. However, magnetic hydrogels are quite brittle and structurally unstable under compact conditions such as in fixed-bed adsorption columns. To address this issue, this study demonstrates a unique hydrogel composite bead structure, providing a good adsorption capacity and superior compressive stress tolerance due to the presence of hollow cores within the beads. The gel beads contain alginate polymer as the matrix and MNP-decorated cellulose nanofibres (CNF) as the reinforcing agent. The MNPs within the gel provide active adsorption functionality, while CNF provide a good stress transfer phenomenon when the beads are under compressive stress. Their adsorption performance is evaluated in a red mud solution for pollutant adsorption. Composite gel beads have shown high performance in adsorbing metal (aluminium, potassium, selenium, sodium, and vanadium) and non-metal (sulphur) contaminations. This novel hybrid hydrogel could be a promising alternative to the conventionally used toxic adsorbent, providing environmentally friendly operational benefits.

A systematic theoretical study the active sites of potassium promoter on the activity of water-gas shift reaction over Pt(1 1 1)

Alkali metals play an important role as promoters in heterogeneous catalytic reactions, but the systematic study of the nature (or active sites) of promoter is far away from enough. Thepossible active sites of potassium promoter such as metallic potassium (K), hydroxyl species stabilized potassium (KOH), and partially oxidized potassium (K2O) species on the Pt-catalyzed water–gas shift reaction (WGSR) wassystematically theoretical studied in this work. The calculation results indicated that the adsorption strength follows the trend K2O/Pt(111) > KOH/Pt(111) ≈ K/Pt(111) > Pt(111), and the K2O additive enhances the adsorption properties largest because of more K ions can be availed to bind with adsorbed species. On the other hand, the promotion effect for WGSR with the order: KOH/Pt(111〉 K2O/Pt(111) > K/Pt(111) ≈ Pt(111), and the KOH species displays the promising promotion effect due to the facile of O–H/C–H bond cleavage as well as the C-O bond formation. Interestingly, it was shown that the high promotion effect of KOH (or K2O) on WGSR is related to the strong activation properties of water dissociation assisted by the OH (or O) group involved in KOH (or K2O). It might be pointed out that the metallic K additive atoms almost have no promotion effect on the Pt-catalyzed WGSR owing to the more difficult in the formation of C-O bond formation compared to that of pure Pt(111), and the active site of potassium promoter is the KOH-like species. The promotion properties of potassium on the adsorption strength of oxygen-containing species such H2O could be ascribed to the strong short-ranged direct interaction between the K-species through space. Microkinetic modeling analysis indicated that the carboxyl mechanism is the dominant mechanism of the whole WGSR, followed by the redox mechanism and formate mechanism. It is desirable for that the present work may extend to the alkali promotion character on WGSR to other situation like metal oxide-supported metal clusters.

Lithium-sensing riboswitch classes regulate expression of bacterial cation transporter genes

Lithium is rare in Earth’s crust compared to the biologically relevant alkali metal cations sodium and potassium but can accumulate to toxic levels in some environments. We report the experimental validation of two distinct bacterial riboswitch classes that selectively activate gene expression in response to elevated Li+ concentrations. These RNAs commonly regulate the expression of nhaA genes coding for ion transporters that weakly discriminate between Na+ and Li+. Our findings demonstrated that the primary function of Li+ riboswitches and associated NhaA transporters is to prevent Li+ toxicity, particularly when bacteria are living at high pH. Additional riboswitch-associated genes revealed how some cells defend against the deleterious effects of Li+ in the biosphere, which might become more problematic as its industrial applications increase.

Ridge regression and artificial neural network to predict the thermodynamic properties of alkali metal Rankine cycles for space nuclear power

The alkali metal Rankine cycle system has great advantages in space nuclear power system. The investigation of thermodynamic properties of alkali metals is fundamental to develop thermodynamic model of thermoelectric conversion system. This paper build models for predicting the thermodynamic properties of alkali metals (potassium, sodium, cesium, rubidium) by statistics and machine learning. Pearson correlation analysis is performed to explain the correlation between measurable variables (temperature, pressure, specific volume, specific heat capacity) and unmeasurable variables (enthalpy, entropy). Ridge regression and radial basis artificial neural network models are established for the enthalpy and entropy of alkali metals respectively. Five evaluation indicators: residual, SSE, MSE, ME and R2 are selected to evaluate the accuracy of different types of prediction models. The practicability and extensibility of the prediction model are proved by case analysis. The results show that the prediction model of enthalpy and entropy based on radial basis neural network has high accuracy, and R2 can reach above 0.9. The entropy prediction model can even be stable at 0.999 when applied to different operating conditions and alkali metals. The new method proposed in this work solves the difficulty of experimental measurement in high temperature section to some extent, and opens a new idea for studying the properties of working medium. At the same time, the validation of the extrapolation feasibility of this method is of great significance to improve the thermodynamic properties database of alkali metals in the whole temperature range.

Potassium-enriched graphite for use as stable hybrid anodes in high-efficiency potassium batteries

Potassium-ion batteries (PIBs) have attracted significant attention due to their low cost and high energy density. Despite being a promising anode candidate for PIBs, graphite is still plagued by limited capacity and fast capacity degradation with low coulombic efficiency (CE). Herein, we propose a high-capacity and highly stable potassium-enriched graphite (KRG) anode which surpasses the limitation of parent graphite. The KRG is characteristic of possessing the potassium-graphite intercalation compounds as a potassiophilic host for uniform and high-efficiency plating/stripping of potassium metal. The robust mixed conducting network possessed by the KRG is beneficial for mitigating drastic volume change of the electrode and improving ion/electron transport. A specific capacity of ∼520 mAh/g was demonstrated for KRG anode as the optimized value to maximize the capacity storage while suppressing dendrites growth. With a stable solid-electrolyte interphase buildup, the KRG/Prussian blue full cell with a controlled anode/cathode capacity ratio of 1.1:1 can deliver a high capacity of 108 mAh/g with a CE of 99% after 180 cycles at 1C. Our results provide valuable insights into the rational design of graphitic anodes for high-energy-density PIBs.

An ultra-low concentration electrolyte with fluorine-free bulky anions for stable potassium metal batteries

An ultra-low concentration electrolyte with fluorine-free bulky anions for stable potassium metal batteries

Intercalation-deposition mechanism induced by aligned carbon fiber toward dendrite-free metallic potassium batteries

Metallic potassium (K) anodes are highly desirable for high energy density batteries. However, challenges lie in uncontrollable dendrite growth and/or inevitable generation of dead K. Here, composite anodes are constructed by covering a layer of aligned carbon fiber on the surface of each metallic K anode (K-ACF). Symmetrical K-ACF//K-ACF cells can work stably without short circuit for over 600 h, which is quite longer than cells using composite anodes with unaligned carbon fiber (K-UCF) and bare metallic K anodes. Comprehensive characterizations reveal a stepwise intercalation-deposition process on the K-ACF anode during the K plating, and the intercalation is proved to be necessary for the uniform K+ flux due to the improved potassiophility of potassiated ACF. Besides, the aligned structure of ACF offers a uniform current density and K+ ion flux on the surface of composite anodes, promoting the stable K stripping/plating. The K-ACF//Prussian blue (PB) cell exhibits a high discharge capacity of 83.6 mAh g−1 (267.4 Wh kg−1 based on the mass of PB) under a charge/discharge rate of 200 mA g−1 with a capacity loss rate of 0.044% per cycle. This work opens up a new avenue toward high energy and dendrite-free potassium batteries.

CoZn Nanoparticles@Hollow Carbon Tubes Enabled High-Performance Potassium Metal Batteries.

Potassium-metal batteries (PMBs) are attractive candidates for low-cost and large-scale energy storage systems due to the abundance of potassium. However, its application is hampered by large volume change and serious dendrite growth. Herein, a CoZn semicoherent structure nanoparticle-embedded nitrogen-doped hollow carbon tube (CoZn@HCT) electrode is prepared via coaxial electrospinning. Due to the high potassiophilic CoZn semicoherent structure nanoparticles and large potassium metal storage space, the free-standing CoZn@HCT host for K metal exhibits uniform K nucleation and stable plating/stripping (stable cycling 1000 h at 1 mA cm-2 with 1 mA h cm-2). Furthermore, enhanced electrochemical performance with good cycling stability and rate capability is achieved in (CoZn@HCT@K||PTCDA) full batteries. Our results highlight a promising strategy for dendrite-free K metal anodes and high-performance PMBs.

Insights into Cationic Transference Number Values and Solid Electrolyte Interphase Growth in Liquid/Solid Electrolytes for Potassium Metal Batteries.

Liquid/solid battery electrolytes make separators dispensable and enable a high cationic transference number with liquid-like room temperature ionic conductivity. This work gives insights into electrochemical behavior (galvanostatic polarization and time-dependent impedance spectroscopy) of liquid/solid electrolytes containing potassium salts in battery cells enclosing potassium metal anodes. Very high potassium transference numbers (t K = 0.88) are observed in carbonate-based electrolytes, linked with long-term mechanical instability of the solid electrolyte interphase on the potassium anode. In the case of glyme-based electrolytes, electrochemical behavior indicates the existence of the highly porous solid electrolyte interphase and additional surface porosity of the potassium electrode.

Atomic and Molecular Layer Deposition as Surface Engineering Techniques for Emerging Alkali Metal Rechargeable Batteries.

Alkali metals (lithium, sodium, and potassium) are promising as anodes in emerging rechargeable batteries, ascribed to their high capacity or abundance. Two commonly experienced issues, however, have hindered them from commercialization: the dendritic growth of alkali metals during plating and the formation of solid electrolyte interphase due to contact with liquid electrolytes. Many technical strategies have been developed for addressing these two issues in the past decades. Among them, atomic and molecular layer deposition (ALD and MLD) have been drawing more and more efforts, owing to a series of their unique capabilities. ALD and MLD enable a variety of inorganic, organic, and even inorganic-organic hybrid materials, featuring accurate nanoscale controllability, low process temperature, and extremely uniform and conformal coverage. Consequently, ALD and MLD have paved a novel route for tackling the issues of alkali metal anodes. In this review, we have made a thorough survey on surface coatings via ALD and MLD, and comparatively analyzed their effects on improving the safety and stability of alkali metal anodes. We expect that this article will help boost more efforts in exploring advanced surface coatings via ALD and MLD to successfully mitigate the issues of alkali metal anodes.

Bifunctional separator with a light-weight coating for stable anode-free potassium metal batteries

The anode-free potassium metal battery (AF-KMBs, N : P = 0 : 1) with liquid electrolyte has been proposed through a separator composite directing strategy. A facile and feasible lithium niobate/Graphene (LiNbO3@G) composite was exploited to modify the glass fiber separator, which can realize high-performance AF-KMBs comprising a configuration of Cu||LiNbO3@G||K0.51V2O5. Due to the ferroelectric and polarization of LiNbO3, a stable solid electrolyte interface (SEI) was steadily formed at the anode interface after preliminary electrochemical activation. Combined with morphology observation and electrochemical characterization, it was proved that potassium was uniformly nucleated and selectively deposited on copper foil without obvious K dendrite. Attributed to the high conductivity of potassium ions and stable SEI, good Coulombic efficiency and long cycle life of the obtained AF-KMBs have been achieved. Consequently, our work demonstrates of great necessity to further explore the high-performance potential of anode-free potassium metal battery.

The Steric Effect in Preparations of Vanadium(II)/(III) Dinitrogen Complexes of Triamidoamine Ligands Bearing Bulky Substituents.

The reactions of newly designed lithiated triamidoamines Li3LR (R = iPr, Pen, and Cy2) with VCl3(THF)3 under N2 yielded dinitrogen–divanadium complexes with a μ-N2 between vanadium atoms [{V(LR)}2(μ-N2)] (R = iPr (1) and Pen (2)) for the former two, while not dinitrogen–divanadium complexes but a mononuclear vanadium complex with a vacant site, [V(LCy2)] (R = Cy2 (3)), were obtained for the third ligand. The V–NN2 and N–N distances were 1.7655(18) and 1.219(4) Å for 1 and 1.7935(14) and 1.226(3) Å for 2, respectively. The ν(14N–14N) stretching vibrations of 1 and 2, as measured using resonance Raman spectroscopy, were detected at 1436 and 1412 cm–1, respectively. Complex 3 reacted with potassium metal in the presence of 18-crown-6-ether under N2 to give a hetero-dinuclear vanadium complex with μ-N2 between vanadium and potassium, [VK(LCy2)(μ-N2)(18-crown-6)] (4). The N–N distance and ν(14N–14N) stretching for 4 were 1.152(3) Å and 1818 cm−1, respectively, suggesting that 4 is more activated than complexes 1 and 2. The complexes 1, 2, 3, and 4 reacted with HOTf and K[C10H8] to give NH3 and N2H4. The yields of NH3 and N2H4 (per V atom) were 47 and 11% for 1, 38 and 16% for 2, 77 and 7% for 3, and 80 and 5% for 4, respectively, and 3 and 4, which have a ligand LCy2, showed higher reactivity than 1 and 2.

Codoped porous carbon nanofibres as a potassium metal host for nonaqueous K-ion batteries

Potassium metal is an appealing alternative to lithium as an alkali metal anode for future electrochemical energy storage systems. However, the use of potassium metal is hindered by the growth of unfavourable deposition (e.g., dendrites) and volume changes upon cycling. To circumvent these issues, we propose the synthesis and application of nitrogen and zinc codoped porous carbon nanofibres that act as potassium metal hosts. This carbonaceous porous material enables rapid potassium infusion (e.g., < 1 s cm−2) with a high potassium content (e.g., 97 wt. %) and low potassium nucleation overpotential (e.g., 15 mV at 0.5 mA cm−2). Experimental and theoretical measurements and analyses demonstrate that the carbon nanofibres induce uniform potassium deposition within its porous network and facilitate a dendrite-free morphology during asymmetric and symmetric cell cycling. Interestingly, when the potassium-infused carbon material is tested as an active negative electrode material in combination with a sulfur-based positive electrode and a nonaqueous electrolyte solution in the coin cell configuration, an average discharge voltage of approximately 1.6 V and a discharge capacity of approximately 470 mA h g−1 after 600 cycles at 500 mA g−1 and 25 °C are achieved.

Robust potassium metal anodes realized by ferroelectricity and high conductivity separator

Low-cost potassium (K) metal batteries (KMBs) have drawn broad attention due to the prospect of wide applications. However, the applications of KMBs have been severely troubled by the problems from the K dendrites and dead K. The disordered K dendrite growth causes repeated fracture and repair of solid electrolyte interphase (SEI), and the aggregation of dead K detached from current collectors around the cathode region leads to rapid capacity attenuation in KMBs. Herein, a barium titanate/reduced graphene oxide (BaTiO3@rGO) composite on glass fiber (GF) separator was prepared with ferroelectrically spin-polarized and high conductive, which highly effective in inhibiting disorderly K dendrite growth and activate the inactive dead K by improving electrochemical performance without affecting the transport of positively charged K ions. The capacity retention ratio (CRR) and attenuation rate of full-cell of KMBs adopting BaTiO3@rGO separator are 87% and 0.02% after 380 cycles at 0.5A g−1, respectively. This research defines an effective strategy to inhibit K dendrites and activate dead K in KMBs.