Rechargeable Potassium Research Articles

KF-Containing Interphase Formation Enables Better Potassium Ion Storage Capability.

Rechargeable potassium ion batteries have long been regarded as one alternative to conventional lithium ion batteries because of their resource sustainability and cost advantages. However, the compatibility between anodes and electrolytes remains to be resolved, impeding their commercial adoption. In this work, the K-ion storage properties of Bi nanoparticles encapsulated in N-doped carbon nanocomposites have been examined in two typical electrolyte solutions, which show a significant effect on potassium insertion/removal processes. In a KFSI-based electrolyte, the N-C@Bi nanocomposites exhibit a high specific capacity of 255.2 mAh g-1 at 0.5 A g-1, which remains at 245.6 mAh g-1 after 50 cycles, corresponding to a high capacity retention rate of 96.24%. In a KPF6-based electrolyte, the N-C@Bi nanocomposites show a specific capacity of 209.0 mAh g-1, which remains at 71.5 mAh g-1 after 50 cycles, corresponding to an inferior capacity retention rate of only 34.21%. Post-investigations reveal the formation of a KF interphase derived from salt decomposition and an intact rod-like morphology after cycling in K2 electrolytes, which are responsible for better K-ion storage properties.

Designing High-Donicity Anions for Rechargeable Potassium Superoxide/Peroxide Batteries.

A battery cathode based on the superoxide/peroxide redox not only inherits the advantage of oxygen (O2 ) batteries in high capacities and low costs but also overcomes the disadvantages in O2 storage, electrolyte evaporation, and anode deactivation due to O2 crossover. Herein, we report an enhanced potassium superoxide (KO2 )/peroxide (K2 O2 ) conversion by adopting a high-donicity anion additive in the ether-based electrolyte. Such an anion was synthesized via a "Solvent-in-Anion" strategy and validated to enhance the electron donicity of the electrolyte. The use of high-donicity anion could lead to enhanced KO2 utilization (≈90.2 %) by retarding electrode passivation and allow the full charging back of K2 O2 through the solution-mediated pathway without electrocatalysts. No apparent cell degradation is observed during the first 120 cycles by controlling the reversible depth-of-discharge capacity at 292 mAh g-1 within an O2 -free region. The K-KO2 cell delivers a high energy efficiency (>84.4 %) and a lifespan of over 1440 hours.

Designing High‐Donicity Anions for Rechargeable Potassium Superoxide/Peroxide Batteries

AbstractA battery cathode based on the superoxide/peroxide redox not only inherits the advantage of oxygen (O2) batteries in high capacities and low costs but also overcomes the disadvantages in O2 storage, electrolyte evaporation, and anode deactivation due to O2 crossover. Herein, we report an enhanced potassium superoxide (KO2)/peroxide (K2O2) conversion by adopting a high‐donicity anion additive in the ether‐based electrolyte. Such an anion was synthesized via a “Solvent‐in‐Anion” strategy and validated to enhance the electron donicity of the electrolyte. The use of high‐donicity anion could lead to enhanced KO2 utilization (≈90.2 %) by retarding electrode passivation and allow the full charging back of K2O2 through the solution‐mediated pathway without electrocatalysts. No apparent cell degradation is observed during the first 120 cycles by controlling the reversible depth‐of‐discharge capacity at 292 mAh g−1 within an O2‐free region. The K−KO2 cell delivers a high energy efficiency (>84.4 %) and a lifespan of over 1440 hours.

Electrospun carbon-based nanomaterials for next-generation potassium batteries.

Rechargeable potassium (K) batteries that are of low cost, with high energy densities and long cycle lives have attracted tremendous interest in affordable and large-scale energy storage. However, the large size of the K-ion leads to sluggish reaction kinetics and causes a large volume variation during the ion insertion/extraction processes, thus hindering the utilization of active electrode materials, triggering a serious structural collapse, and deteriorating the cycling performance. Therefore, the exploration of suitable materials/hosts that can reversibly and sustainably accommodate K-ions and host K metals are urgently needed. Electrospun carbon-based materials have been extensively studied as electrode/host materials for rechargeable K batteries owing to their designable structures, tunable composition, hierarchical pores, high conductivity, large surface areas, and good flexibility. Here, we present the recent developments in electrospun CNF-based nanomaterials for various K batteries (e.g., K-ion batteries, K metal batteries, K-chalcogen batteries), including their fabrication methods, structural modulation, and electrochemical performance. This Feature Article is expected to offer guidelines for the rational design of novel electrospun electrodes for the next-generation K batteries.

Hybrid-Solvent Electrolytes for Enhanced Potassium-Oxygen Battery Performance.

Rechargeable potassium-oxygen batteries (KOB) are promising next-generation energy storage devices because of the highly reversible O2/O2- redox reactions during battery charge and discharge. However, the complicated cathode reaction processes seriously jeopardize the battery reaction kinetics and discharge capacity. Herein, we propose a hybrid-solvent strategy to effectively tune the K+ solvation structure, which demonstrates a critical influence on the charge-transfer kinetics and cathode reaction mechanism. The cosolvation of K+ by 1,2-dimethoxyethane (DME) and dimethyl sulfoxide (DMSO) could greatly decrease overpotentials for the cathode processes and increase the cathode discharge capacity. Furthermore, the Coulombic efficiency for the cathode could be significantly improved with the enhanced solution-mediated KO2 growth and stripping during cycling. This work provides a promising electrolyte design approach to improve the electrochemical performance of the KOB.

A Fast-Charging and High-Temperature All-Organic Rechargeable Potassium Battery.

Developing fast-charging, high-temperature, and sustainable batteries is critical for the large-scale deployment of energy storage devices in electric vehicles, grid-scale electrical energy storage, and high temperature regions. Here, a transition metal-free all-organic rechargeable potassium battery (RPB) based on abundant and sustainable organic electrode materials (OEMs) and potassium resources for fast-charging and high-temperature applications is demonstrated. N-doped graphene and a 2.8mpotassium hexafluorophosphate (KPF6 ) in diethylene glycol dimethyl ether (DEGDME) electrolyte are employed to mitigate the dissolution of OEMs, enhance the electrode conductivity, accommodate large volume change, and form stable solid electrolyte interphase in the all-organic RPB. At room temperature, the RPB delivers a high specific capacity of 188.1 mAh g-1 at 50mA g-1 and superior cycle life of 6000 and 50000 cycles at 1 and 5 A g-1 , respectively, demonstrating an ultra-stable and fast-charging all-organic battery. The impressive performance at room temperature is extended to high temperatures, where the high-mass-loading (6.5mg cm-2 ) all-organic RPB exhibits high-rate capability up to 2 A g-1 and a long lifetime of 500 cycles at 70-100°C, demonstrating a superb fast-charging and high-temperature battery. The cell configuration demonstrated in this work shows great promise for practical applications of sustainable batteries at extreme conditions.

Low-Temperature High-Areal-Capacity Rechargeable Potassium-Metal Batteries.

High mass loading and high areal capacity are key metrics for commercial batteries, which are usually limited by the large charge-transfer impedance in thick electrodes. This can be kinetically deteriorated under low temperatures, and the realization of high-areal-capacity batteries in cold climates remains challenging. Herein, a low-temperature high-areal-capacity rechargeable potassium-tellurium (K-Te) battery is successfully fabricated by knocking down the kinetic barriers in the cathode and pairing it with stable anode. Specifically, the in situ electrochemical self-reconstruction of amorphous Cu1.4 Te in a thick electrode is realized simply by coating micro-sized Te on the Cu collector, significantly improving its ionic conductivity. Meanwhile, the optimized electrolyte enables fast ion transportation and a stable K-metal anode at a large current density and areal capacity. Consequently, this K-Te battery achieves a high areal capacity of 1.25mAhcm-2 at -40°C, which greatly exceeds those of most reported works. This work highlights the significance of electrode design and electrolyte engineering for high areal capacity at low temperatures, and represents a critical step toward practical applications of low-temperature batteries.

Confining Dendrite Growth Enabled By Ionically Conductive Interphase for Highly Stable Potassium Metal Anode

Potassium metal has been considered as one of the ultimate anode for rechargeable potassium batteries because of its high theoretical capacity (686 mAh g-1) and low electrode potential (~2.93 V vs. SHE). However, K metal is thermodynamically instable in aprotic electrolyte and uneven K plating usually leads to dendritic K metal deposition, resulting in low Coulombic efficiency and safety concerns.1,2In this study, we introduce potential strategy to stabilize the K metal anode via simple chemical interface control. The robust and ionically conductive passivation layer can be controllably designed by the spontaneous chemical reaction when a K metal foil kept in contact with a liquid phase potassium-polysulfide (0.05M K2S5 dissolved in DEGDME);3 this provides a strong guiding effect to form an electronically and ionically conductive solid electrolyte interphase (SEI) layer, enabling a dense K plating with dendrite-free morphology. The unique characteristics of the functionalized K-metal is fully evidenced by the Operando optical microscopy and phase field modeling in electrodeposition process. Under practical constraints (i.e. using lean electrolyte and thin polymer separator), the functionalized K-metal anode exhibits the ultra-long-term K plating-stripping cycles over 1200 h in a symmetrical cells and further highlights a practical applicability with high areal capacity and fast charging-discharging capability in full-cells using TiS2 cathode. References U.-H. Kim, G.-T. Park, B.-K. Son, G. W. Nam, J. Liu, L.-Y. Kuo, P. Kaghazchi, C. S. Yoon and Y.-K. Sun, Nat. Energy, 2020, 5, 860. J.-Y. Hwang, S.-T. Myung and Y.-K. Sun, Adv. Funct. Mater., 2018, 28, 1802938.J.-Y. Hwang, H. M. Kim, C. S. Yoon and Y.-K. Sun, ACS Energy Lett., 2018, 3, 540-541.

Effects of Interfacial Solvation Structures on the Morphological Stability of Potassium Metal Anodes Revealed by Operando Diagnosis

Rechargeable potassium (K) metal batteries have been considered promising candidates for low-cost energy storage. However, they suffer from severe side reactions and the poor morphological stability of the metal anode that jeopardize cell safety and cycle life. Here, we report a whisker-free nonporous K metal anode with superior morphological stability that can self-modulate into ingot-type deposits on a standard current collector. Comparative investigations confirm the importance of interfacial solvation structures in achieving the ideal morphological stability and facile charge transfer kinetics. Further operando diagnosis revealed that the electrochemically refined K metal anode can enable stable K metal full-cell cycling.

Abnormal-stoichiometric KxCl crystal decoration: A new strategy to improve K-Ion storage performance of graphene paper

Carbonaceous materials are the most attractive choices for rechargeable potassium ion batteries (PIBs), but many K-ion batteries exhibit low specific capacity, limited cycling stability, and disappointed rate capability for the poor K-ions intercalation performance. Here, we chose graphene paper as the research object, fabricated a freestanding K–Cl―graphene paper electrode with abnormal-stoichiometric KxCl crystals (KxCl-rGO), and proposed a novel universal design strategy by using this electrode to achieve a high-efficiency K-graphene battery. Compared with pure rGO, KxCl-rGO displays a high reversible capacity of 318 mAh g−1 at 20 mA g−1 (38.9% higher than rGO) and can retain a reversible capacity of 157 mAh g−1 at 100 mA g−1 after 500 cycles. The increased K-ion diffusion and enhanced electrical conductivity (the conductivity increased 83% than rGO) play a significant role in improving the potassium storage performance of KxCl-rGO. What's more, for graphene with more functional groups, this pre-treatment improves the potassium storage performance of carbon materials more significantly (approximately doubled).

Graphene/Phosphorene nano-heterostructure as a potential anode material for (K/Na)-ion batteries: Insights from DFT and AIMD

Rechargeable Potassium and Sodium-ion batteries started to receive a vast amount of attention in recent years against their Lithium-ion counterparts. However, the development of a high-performing anode material for these ion batteries is still to be explored. In this work, we conduct a first-principles study on the adsorption and diffusion behaviors of Potassium (K) and Sodium (Na) in a Graphene/Phosphorene (G/P) van der Waals nano-heterostructure, in order to assess its suitability as an anode for both K-ion and Na-ion batteries. We investigate the electrochemical properties of the system, including binding energies, band structure, ion diffusivity out-side and in-side the G/P system, as well as the heterostructure’s stability at a high metallic coverage. The calculated binding energies for K and Na are −2.69 eV and −2.42 eV, respectively, which are strong enough to prevent metallic clustering during the cycling. The diffusion of K/Na within G/P’s regions shows strong directional anisotropy with a low diffusion barrier of 0.04 eV for K and 0.05 eV for Na along the zigzag direction. We also observe that the addition of K/Na atoms into the G/P system turns its semi-metallic nature into a metallic one. Moreover, we demonstrate that the intercalation of K/Na atoms within the G/P structure give low operating potentials of approximately 0.29 V for K and 0.58 V for Na. Thus, the nano-heterostructure can provide a theoretical storage capacity of 433 mAh/g and 580 mAh/g respectively for K and Na. Finally, the thermal stability of a fully potassiated/sodiated G/P system at room temperature is revealed by the ab-initio Molecular-Dynamics (AIMD) calculations. Considering all these properties, we conclude that the G/P nano-heterostructure can be considered as a good candidate for negative-electrode-materials for both K- and Na-ion batteries.

Mechanistic Insights into the Intercalation and Interfacial Chemistry of Mesocarbon Microbeads Anode for Potassium Ion Batteries.

Mesocarbon microbeads (MCMB) are highly desirable as anode materials for rechargeable potassium ion batteries (PIBs) due to their commercially availability, high stability and low-cost. However, their charge storage and interfacial mechanisms are still unclear. In this work, the intercalation mechanisms and the solid-electrolyte-interphase (SEI) formation of the MCMB in four different electrolytes is comprehensively studied. The MCMB anodes exhibit superior rate and cycle performances via a naked K-ions sequentially staging intercalation mechanism, realizing the complete transformation from graphite to KC8 . Whereas a solvated K-ions co-intercalation mechanism of the MCMB occurs in ether-based electrolytes, which might induce graphite exfoliation and result in unsatisfied specific capacity and capacity decay. Nevertheless, this co-intercalation behavior could be effectively suppressed by a highly concentrated electrolytes. Interfacial analyses unveil the distinct SEI components, which vary with the electrolyte chemistries. These SEI components also varies from surface to bulk and especially attention should be paid to the accurate control of the concentration of the fluoroethylene carbonate additives. This work provides a panoramic understanding of the intercalation and interfacial mechanisms on the MCMB anodes for PIBs.

Tuning the Linkers in Polymer-Based Cathodes to Realize High Sulfur Content and High-Performance Potassium–Sulfur Batteries

The development of effective rechargeable potassium–sulfur (K–S) batteries has been retarded by a severe polysulfide shuttle effect and low sulfur content in the cathode (generally less than 40 wt ...

Highly stable potassium metal batteries enabled by regulating surface chemistry in ether electrolyte

Rechargeable potassium (K) metal batteries (PMBs) remain deeply challenged by the lack of suitable electrolytes that are stable against both highly reactive K anodes and 4 V-class cathodes. Despite their good reductive stability with K metal, classic potassium bis(fluorosulfonyl)amide (KFSI)-based ether electrolytes are typically used only in <4.0 V PMBs due to their limited oxidation stability. Herein, a potassium nitrate (KNO3)-containing ether electrolyte, at a moderate KFSI concentration (2.3 M) rather than a high concentration (normally, >3 M), is reported for the first time to be used in 4 V-class PMBs. A stable N/F-rich solid electrolyte interphase (SEI) is formed, enabling dense and uniform K deposition, especially under high current density. Remarkably, the PMBs with Prussian blue cathode exhibits an unprecedented cycle life (1000 cycles, 122 days). This work provides new perspectives of electrolyte design for 4 V-class PMBs.

P2‐K0.76Fe0.2Mg0.1Mn0.7O2made from earth‐abundant elements for rechargeable potassium ion battery

AbstractDue to the large volume change, limited energy density, large safety problems, and other factors restricting the development of potassium ion battery in the process of charge and discharge, the research on the cathode materials of potassium ion battery is an indispensable part. In this article, we designed and predicted P2‐type structures by introducing “cationic potential” that captures the key interactions of the layered materials. The precursors of the designed potassium ion battery cathode materials were obtained by co‐precipitation method. Through component analysis, the experimental conditions most in line with the theoretical content of precursors were found. The cathode material was synthesized by solid phase method. This material has a highly reversible K+insertion/deinsertion effect. The initial discharge specific capacity of the battery appears at about 47 mAh/g. After 30 charge‐discharge cycle tests, the discharge specific capacity of the battery drops to about 33 mAh/g, and the retention rate is about 70%.

Novel Quasi-Liquid K-Na Alloy as a Promising Dendrite-Free Anode for Rechargeable Potassium Metal Batteries.

Rechargeable potassium metal batteries are promising energy storage devices with potentially high energy density and markedly low cost. However, eliminating dendrite growth and achieving a stable electrode/electrolyte interface are the key challenges to tackle. Herein, a novel “quasi‐liquid” potassium‐sodium alloy (KNA) anode comprising only 3.5 wt% sodium (KNA‐3.5) is reported, which exhibits outstanding electrochemical performance able to be reversibly cycled at 4 mA cm–2 for 2000 h. Moreover, it is demonstrated that adding a small amount of sodium hexafluorophosphate (NaPF6) into the potassium bis(fluorosulfonyl)imide electrolyte allows for the formation of the “quasi‐liquid” KNA on electrode surface. Comprehensive experimental studies reveal the formation of an unusual metastable KNa2 phase during plating, which is believed to facilitate simultaneous nucleation and suppress the growth of dendrites, thereby improving the electrode's cycle lifetime. The “quasi‐liquid” KNA‐3.5 anode demonstrates markedly enhanced electrochemical performance in a full cell when pairing with Prussian blue analogs or sodium rhodizonate dibasic as the cathode material, compared to the pristine potassium anode. Importantly, unlike the liquid KNA reported before, the “quasi‐liquid” KNA‐3.5 exhibits good processability and can be readily shaped into sheet electrodes, showing substantial promise as a dendrite‐free anode in rechargeable potassium metal batteries.

Novel Quasi-Liquid K-Na Alloy as a Dendrite-Free Anode for Potassium Metal Batteries

Rechargeable potassium metal batteries are promising energy storage devices with potentially high energy density and markedly low cost. However, there are key challenges to eliminate dendrite growth and achieve a stable electrode/electrolyte interface. While liquid potassium-sodium alloy (KNA) has recently been demonstrated to be able to address the dendrite growth issue, it has poor mechanical processability due to its high degree of fluidity, which is difficult to be processed for use in practical potassium batteries. In this presentation, we report a novel “quasi-liquid” KNA comprising only 3.5 wt% Na, which exhibits superior electrochemical performance able to be repeatedly plated and stripped on the copper substrate at 0.5 mA cm-2 up to 220 cycles with a high Coulombic efficiency of above 89%. Moreover, an unusual metastable KNa2 phase is captured during the K-Na plating by in-situ X-ray diffractometry, which may assist in the nucleation of K and Na continually during plating, helping to suppress the formation of dendrites. The “quasi-liquid” KNA-3.5 anode demonstrates markedly enhanced electrochemical performance in a full cell when pairing with Prussian blue analogues or sodium rhodizonate dibasic as the cathode material, compared to the pristine potassium anode. Importantly, unlike the liquid KNA reported before, the “quasi-liquid” KNA-3.5 exhibits good processability and can be readily shaped into sheet electrodes, showing substantial promise as a dendrite-free anode in rechargeable potassium metal batteries.

Rechargeable Potassium–Selenium Batteries

AbstractRechargeable potassium–selenium (K–Se) batteries, as an emerging electrochemical energy storage system, has recently captured intensive attention due to the desirable natural abundance and low redox potential of elemental potassium as well as the relatively high electronic conductivity and impressive theoretical volumetric capacity of elemental selenium. Although great progress on cathode materials design and electrochemical performance improvement has been made, K–Se batteries are still confronted with a series of key challenges, including low reactive activity, shuttle effect, volume expansion, potassium dendrite growth, and high chemical activity of potassium metal. The recent advances in rechargeable K–Se batteries are comprehensively summarized with an emphasis on discussing the electrochemical mechanisms and central challenges, presenting the synthesis, properties, and electrochemical performance of selenium‐based cathode materials, and extending potential tactics for tackling the key issues and developmental directions for future research.

In situ visualizing the interplay between the separator and potassium dendrite growth by synchrotron X-ray tomography

Abstract Rechargeable potassium (K) batteries are a promising next-generation technology for low-cost grid scale energy storage applications. Nevertheless, the undesirable interfacial instabilities originating from the interplay between the employed separators and electrodes largely compromise the battery’s performance, and the underlying mechanism of which remains elusive. Herein, the interfacial stability between three types of commercial separators (Celgard 2325, Celgard 2400 and GF/D) and the K electrodeposits is investigated in K|K symmetric cells via in-situ Synchrotron X-ray tomography technique. It is demonstrated that the cell built with a Celgard 2400 separator can achieve a stable cycling performance due to its high mechanical strength and integrity along the thickness direction, thus alleviating the K dendrites growth. In contrast, a GF/D membrane of low mechanical cohesion and excessive porosity is found to be easily deformed and filled with deciduous potassium dendritic aggregates during battery cycling. Similarly, the tri-layer Celgard 2325 separators, which are weakly bonded by interlaminar forces, are found to be severely delaminated by the overgrowth of K dendrites. Furthermore, it is revealed that the delamination failure behaviors of Celgard 2325 is driven by the local stress induced by the spatially and heterogeneously formed dead K dendrites. Our work provides direct visualization of morphological evolvement of the separators in presence of potassium dendrites in K|K symmetric cells and highlights the significance of mechanical cohesion, porosity distribution and mechanical integrity of separators in dictating the battery’s performance under realistic battery operation conditions. As a result, these discoveries provide an in-depth understanding that is needed to design next-generation high performance separators to mitigate the formation of potassium dendrite in KMBs.

Status of rechargeable potassium batteries

Future renewable energy integrated grid systems require rechargeable batteries with low cost, high safety, and long cycle life. The much higher abundance of sodium and potassium compared to lithium in earth crust indicates that rechargeable sodium and potassium batteries are attractive replacements for lithium-ion batteries. Rechargeable potassium batteries have gained tremendous attention during the past decade. However, the development of rechargeable potassium batteries is still in its infancy. This review summarizes the recent technological developments in rechargeable potassium batteries. First, we summarize the latest achievements of active materials design, mechanistic understanding, and exploration of new active materials. We propose new directions in tuning the architecture and enhancing the electrochemical performances of high-performance anodes and cathodes. Second, we also summarize the advances that have been achieved in the new configurations of rechargeable potassium battery systems (potassium-ion capacitors, potassium dual ion batteries, potassium-sulfur batteries, and potassium-oxygen batteries). Finally, we propose future directions and design strategies that could be employed to advance rechargeable potassium batteries toward commercial applications. In this review, a large family of rechargeable batteries based on potassium as charge carrier are summarized. Rechargeable potassium ion batteries include potassium-ion batteries, potassium-ion capacitors, potassium-ion-based dual ion batteries, potassium-sulfur batteries, and potassium-oxygen batteries. Future directions and design strategies that could be employed to advance rechargeable potassium batteries toward commercial applications are proposed. • Rechargeable potassium ion battery as a promising rechargeable battery system. • Current status and future research trends of rechargeable potassium batteries. • Strategies for developing practical anodes and cathodes for potassium batteries. • Recent advances of different configurations of rechargeable potassium batteries.