Potassium Metal Research Articles

Breaking Anionic Solvation Barrier for Safe and Durable Potassium-ion Batteries Under Ultrahigh-Voltage Operation.

Ultrahigh-voltage potassium-ion batteries (PIBs) with cost competitiveness represent a viable route towards high energy battery systems. Nevertheless, rapid capacity decay with poor Coulombic efficiencies remains intractable, mainly attributed to interfacial instability from aggressive potassium metal anodes and cathodes. Additionally, high reactivity of K metal and flammable electrolytes pose severe safety hazards. Herein, a weakly solvating fluorinated electrolyte with intrinsically nonflammable feature is successfully developed to enable an ultrahigh-voltage (up to 5.5 V) operation. Through breaking the anionic solvation barrier, synergistic interfacial modulation can be achieved by the formation of robust anion-derived inorganic-rich electrode-electrolyte interfaces on both the cathode and anode. As proof of concept, a representative KVPO4F cathode can sustain 1600 cycles with 84.4% of capacity retention at a high cutoff voltage of 4.95 V. Meanwhile, K plating/stripping process in our designed electrolyte also demonstrates optimized electrochemical reversibility and stability with effectively inhibited potassium dendrites. These findings underscore the critical impact of anion-dominated solvation configuration on synergistic interfacial modulation and electrochemical properties. This work provides new insights into rational design of ultrahigh-voltage and safe electrolyte for advanced PIBs.

Insight into the Pyrolysis Mechanism of α-O-4 Linked Lignin: The Role of Alkali Metal Potassium

Insight into the Pyrolysis Mechanism of α-O-4 Linked Lignin: The Role of Alkali Metal Potassium

A Thermally Robust Biopolymeric Separator Conveys K+ Transport and Interfacial Chemistry for Longevous Potassium Metal Batteries.

Potassium metal batteries (KMBs) hold promise for stationary energy storage with certain cost and resource merits. Nevertheless, their practicability is greatly handicapped by dendrite-related anodes, and the target design of specialized separators to boost anode safety is in its nascent stage. Here, we develop a thermally robust biopolymeric separator customized via a solvent-exchange and amino-siloxane decoration strategy to render durable and safe KMBs. Through experimental investigation and theoretical computation, we reveal that the optimized porosity and surface functionalization could manage ion transport and interfacial chemistry, thereby enabling efficient K+ diffusion and a favorable solid electrolyte interphase to achieve prolonged cycling stability (over 3000 h). The thus-assembled full cell retains 80% of its initial capacity after 400 cycles at 0.5 A g-1. The heat-proof property of the designed separator is further demonstrated. Our biopolymeric separator, affording multifunctional features, provides an appealing solution to circumvent instability and safety issues associated with potassium metal batteries.

High-Rate 4.2 V Solid-State Potassium Batteries by In Situ Polymerized Epoxide Ether Electrolyte.

Solid-state metallic potassium batteries (SSMPBs) afresh have attracted incremental attention because of their potential to supplement solid-state metallic lithium batteries. However, SSMPBs suffer poor electrochemical performances due to the low ionic conductivity of solid electrolytes and huge electrode/electrolyte interfacial resistance. Herein, high-rate SSMPBs are achieved by in situ ring-opening polymerization of 1,3-dioxolane with succinonitrile as a plasticizer and Al(OTf)3 as the catalyst, where the succinonitrile enables short-chain polyether electrolytes. The in situ polymerized electrolytes deliver a high ionic conductivity of 4.5 × 10-5 S cm-1 at room temperature and excellent stabilities at high oxidation potentials (4.2 V vs K+/K) and against metallic K anodes. All these result in SSMPBs with a discharge capacity of 69 mAh g-1 under a high rate of 100 mA g-1 and a retention of 88.8% after 100 cycles, and the rate and capacity retention are higher than those in previous work on SSMPBs.

Optimized K+ Deposition Dynamics via Potassiphilic Porous Interconnected Mediators Coordinated by Single-Atom Iron for Dendrite-Free Potassium Metal Batteries.

Potassium metal batteries are emerging as a promising high-energy density storage solution, valued for their cost-effectiveness and low electrochemical potential. However, understanding the role of potassiphilic sites in nucleation and growth remains challenging. This study introduces a single-atom iron, coordinated by nitrogen atoms in a 3D hierarchical porous carbon fiber (Fe─N-PCF), which enhances ion and electron transport, improves nucleation and diffusion kinetics, and reduces energy barriers for potassium deposition. Molten potassium infusion experiments confirm the Fe─N-PCF's strong potassiphilic properties, accelerating adsorption kinetics and improving potassium deposition performance. According to the Scharifker-Hills model, traditional carbon fiber substrates without potassiphilic sites cause 3D instantaneous nucleation, leading to dendritic growth. In contrast, the integration of single-atom and hierarchical porosity promotes uniform 3D progressive nucleation, leading to dense metal deposition, as confirmed by dimensionless i2/imax 2 versus t/tmax plots and real-time in situ optical microscopy. Consequently, in situ X-ray diffraction demonstrated stable potassium cycling for over 1900 h, while the Fe─N-PCF@K||PTCDA full cell retained 69.7% of its capacity after 2000 cycles (72 mAh g-1), with a low voltage hysteresis of 0.876V, confirming its strong potential for high energy density and extended cycle life, paving the way for future advancements in energy storage technology.

Realizing an Energy-Dense Potassium Metal Battery at -40 °C via an Integrated Anode-Free and Dual-Ion Strategy.

Potassium (K)-based batteries hold great promise for cryogenic applications owing to the small Stokes radius and weak Lewis acidity of K+. Nevertheless, energy-dense (>200 W h kg-1cathode+anode) K batteries under subzero conditions have seldom been reported. Here, an over 400 W h kg-1cathode+anode K battery is realized at -40 °C via an anode-free and dual-ion strategy, surpassing these state-of-the-art K batteries and even most Li/Na batteries at low temperatures (LTs). By introduction of a strongly associating salt as an additive to this anode-free K battery, an anion-derived solid electrolyte interphase can be established for a highly reversible, zero-excess K plating/stripping behavior on a bare current collector. Meanwhile, a binary solvent is rationally designed for lowering the cation desolvation energy barrier, which ensures comparably facile cation and desolvation-free anion kinetics in this dual-ion structure even at LTs. Consequently, the K||Al half-cell delivers a high Coulombic efficiency of 99.98% at -40 °C. By pairing with a high-energy cathode, a proof-of-concept anode-free K dual-ion battery (N/P = 0) is fabricated, delivering a record-high energy density of 407 W h kg-1cathode+anode with stable cycling of 183 cycles (80% capacity retention) at -40 °C. This work paves a way toward energy-dense batteries at extreme scenarios.

A bismuth oxide-modified copper host achieving bubble-free and stable potassium metal batteries.

Due to the minimal electrochemical oxidation-reduction potential, the potassium (K) metal anode has emerged as a focal in K-ion batteries. However, the reactivity of the K metal anode leads to significant side reactions, particularly gas evolution. Mitigating gas generation from K metal anodes has been a persistent challenge in the field. In this study, we propose a dual protective layer design through pre-treatment of the K metal anode, employing a Bi2O3 modification layer alongside a stable solid electrolyte interface (SEI) formed during the initial charge-discharge cycle, which significantly suppresses gas evolution. Furthermore, we observe that the Bi2O3 modification layer enhances K nucleation due to its strong potassiophilicity when incorporated into the substrate material. The resultant SEI, consisting of dual inorganic layers of Bi-F and K-F formed through the Bi2O3 modification, effectively mitigates side reactions and gas generation while inhibiting dendrite growth. Utilizing a Cu@BO@K host, we achieve a nucleation overpotential as low as 40 mV, with a stability of 1900 h in a Cu@BO@K‖Cu@BO@K cell and a high average Coulombic efficiency of 99.2% in a Cu@BO@K‖Cu cell at 0.5 mA cm-2/0.5 mA h cm-2. Additionally, Cu@BO@K‖PTCDA also presents a high reversible capacity of 114 mA g-1 at 100 mA g-1 after 200 cycles. We believe that this work presents a viable pathway for mitigating side reactions in K metal anodes.

Entropy-Repaired Solvation Structure Strategy for High-Efficiency Phosphate-Based Localized High-Concentration Electrolytes in Potassium Batteries.

The safety and cycling stability of potassium-ion batteries (PIBs) are deeply associated with potassium-ion electrolytes. However, due to the weak Lewis acidity of potassium ions, localized high-concentration electrolytes in PIBs are prone to excessive weak solvation. Herein, we propose an entropy repair strategy for the solvation structure of potassium ions and systematically design a moderately weakly solvated high-entropy localized high-concentration electrolyte. The repaired electrolyte can achieve an average stable Coulombic efficiency of 99.4% on the Cu collector surface. The potassium symmetric battery can be stably cycled for over 10000 h under a high current density of 0.5 mA cm-2 and a large deposition capacity of 1 mAh cm-2. The potassium metal pouch cell, using K1.92Fe[Fe(CN)6]0.94∙0.5H2O as the cathode, maintains a capacity retention of 87.5% after 2000 cycles at a current density of 0.5 A g-1. Even when the current density is increased tenfold from 0.1 A g-1, the battery still retains 67.1% of its capacity. Additionally, due to the introduction of multiple solvents, the potassium metal battery with perylene-3,4,9,10-tetracarboxylic dianhydride as the cathode can maintain reversible capacities of 94.0 and 77.3 mAh g-1 and operate stably at ambient temperatures of -20 and -40 ℃, respectively.

A comparative meta-analysis of structural magnetic resonance imaging studies and gene expression profiles revealing the similarities and differences between late life depression and mild cognitive impairment.

Late-life depression (LLD) predisposes individuals to cognitive decline, often leading to misdiagnoses as mild cognitive impairment (MCI). Voxel-based morphometry (VBM) can distinguish the profiles of these disorders according to gray matter (GM) volumes. We integrated findings from previous VBM studies for comparative analysis and extended the research into molecular profiles to facilitate inspection and intervention. We comprehensively searched PubMed and Web of Science for VBM studies that compared LLD and MCI cases with matched healthy controls (HCs) from inception to 31st December 2023. We included 13 studies on LLD (414 LLDs, 350 HCs) and 50 on MCI (1878 MCIs, 2046 HCs). Seed-based d Mapping with Permutation of Subject Images (SDM-PSI) was used for voxel-based meta-analysis to assess GM atrophy, spatially correlated with neuropsychological profiles. We then used multimodal and linear-model analysis to assess the similarities and differences in GM volumetric changing patterns. Partial least squares (PLS) regression and gene enrichment were employed for transcription-neuroimaging associations. GM volumes in the left hippocampus and right parahippocampal gyrus are more affected in MCI, along with memory impairment. MCI was spatially correlated with a more extensive reduction in the levels of neurotransmitters and a severe downregulation of genes related to cellular potassium ion transport and metal ion transmembrane transporter activity. Compared to LLD, MCI exhibited more GM atrophy in the hippocampus and parahippocampal gyrus and lower gene expression of ion transmembrane transport. Our findings provided imaging-transcriptomic-genetic integrative profiles for differential diagnosis and precise intervention between LLD and MCI.

Potassium Alloy Reference Electrodes for Potassium-Ion Batteries

Potassium-ion batteries (KIBs) represent a promising complementary technology to lithium-ion batteries due to the availability and low cost of potassium. KIBs could also be produced with graphite anodes and Prussian blue analogue (PBA) cathodes, reducing the demand for rare, costly elements necessary in LIBs.1 However, accurate characterization of KIB electrode materials is currently impeded by a lack of suitable reference electrodes. A reference electrode should have a stable rest potential, should be chemically inert, and should operate within the electrochemical stability window of KIB electrolytes.Many studies currently use potassium metal as a reference electrode out of necessity, which does not satisfy any of the above criteria. The potential of potassium metal has been shown to be irreproducible and it can drift over time,2 which we demonstrated may be caused by the high concentrations of sodium and other impurities present in commercially available potassium metal.3 Potassium metal pre-treatment has therefore been necessary to achieve satisfactory reliability of rest potential.2,3 Potassium metal is also highly reactive, decomposing electrolyte on contact and forming resistive solid electrolyte interphase (SEI) layers. Electrolyte decomposition products formed at potassium metal electrodes have further been observed to travel across cells and deposit on the other electrode as a result of crosstalk.4 The development of a stable reference electrode for KIBs is therefore of critical importance.Here, we explore the K-In and K-Bi binary alloy systems as potential reference electrode materials and synthesize promising two-phase alloys. These are metallic, and hence electronically conductive, and the two-phase nature should provide a stable potential, independent of random composition fluctuations. The In-KIn4 system displays a rest potential of 0.64 V vs. K+/K but takes tens of hours to stabilize, indicating a kinetic limitation. On the other hand, the Bi-KBi2 system displays a rest potential of 1.07 V vs. K+/K, greatly reducing the driving force for electrolyte reduction, and stabilizes within a few hours.5 We therefore demonstrate the merits and use of Bi-KBi2 as a stable K-ion reference electrode.5 Its implementation in three-electrode cells would enable the accurate assignment of electrochemical behaviour to the correct electrode, facilitating the development of KIB electrode materials.

(Invited) Unified Interphase Design for Electrochemical Stability of Metal Anodes with Liquid-Based and All Solid-State Electrolytes

Lithium metal battery systems (LMBs) are being sought as an ultimate replacement to lithium ion batteries (LIBs), potentially increasing the cell energy by over fifty percent due to the high capacity and low voltage of the metal anode. Analogous improvement in energy is possible with sodium metal batteries (NMBs) and with potassium metal batteries (KMBs), where existing ion insertion anodes can be replaced by plating/stripping metal. However, in all three cases safety and performance are compromised by an unstable solid electrolyte interphase (SEI) that consumes metal ions and electrolyte, and ultimately leads to dendrites. This presentation provides a series of case studies derived from the group's LMB, NMB and KMB liquid and solid-state research on the microstructural design principles that provide for long-term cycling and fast-charge stability of metal anodes. The approaches may be categorized as the following: a) design of plating/stripping supports and templates with tuned geometry and functionality; b) design of secondary interlayers placed between the metal anode and the separator; and c) design of multifunctional hybrid separators to replace the conventional polymer separators employed with LIBs. It is demonstrated that despite appearing distinct, the efficacy of each in enabling electrochemical stability originates from three fundamental features that are directly interrelated. The wetting behavior of the electrolyte on the anode must be optimized, the wetting/stripping behavior of the metal anode on the current collector must be controlled, and a geometrically and chemically modified SEI must be established. Simultaneously achieving all three leads to stable plating/stripping, while missing even one leads to rapid dendrite growth. Cryogenic FIB cross sections and cryo-TEM are combined to yield new insight regarding film wetting behavior and early dendrite formation in optimized versus baseline specimens, analyzing growth in several representative electrolytes.

Advanced Potassium-Sulfur Batteries Using High-Concentration Electrolytes and Sulfurized Polyacrylonitrile Cathodes

Potassium–sulfur (K–S) batteries are emerging as promising technology due to their cost-effectiveness and high theoretical energy density.1 However, traditional K–S batteries face two significant challenges: (1) uncontrollable of potassium polysulfide (KPS) dissolution into the liquid electrolyte, and (2) the highly chemical and electrochemical reactive of the K-metal anode that leads to dendrite growth. These issues cause critical performance degradation, result in sudden death. Herein, I introduce a high-areal capacity, unprecedented cycle life of K–S battery that incorporates a high-concentration electrolyte (HCE) (4.34 mol∙kg⁻¹ potassium bis(fluorosulfonyl)imide in 1,2-dimethoxyethane). The introduction of HCE improves the interfacial stability between the K metal anode and electrolyte, as shown by operando optical microscopy and phase field modeling. Through dynamics simulations and Raman spectroscopy, changes in the solvation structure of the electrolyte were confirmed. The formation of a stable solid electrolyte interface was observed, which effectively suppresses the growth of potassium dendrites, as demonstrated by X-ray photoelectron spectroscopy. Furthermore, I propose the synergetic effect of K-S battery using sulfurized polyacrylonitrile cathode, where sulfur is covalently bonded to the carbon backbone, effectively inhibiting KPS dissolution. A. Manthiram, Y. Fu, S.-H. Chung, C. Zu, Y.-S. Su, Rechargeable Lithium-Sulfur batteries, Chem. Rev.114 (2014) 11751.J. Park, J. Lee, M. H. Alfaruqi, W.-J. Kwak, J. Kim, J.-Y. Hwang, Initial investigation and evaluation of potassium metal as an anode for rechargeable potassium batteries, J. Mater. Chem. A.8 (2020) 16718.

Fundamental Investigations on the Ionic Transport and Thermodynamic Properties of Potassium-Ion Electrolytes

Potassium-ion batteries (KIBs) represent a promising complementary technology to lithium-ion batteries (LIBs) due to the availability and low cost of potassium. KIBs could also be produced with graphite (G) anodes and Prussian blue analog (PBA) cathodes, reducing the demand for rare, costly elements necessary in LIBs.1 However, there is currently no electrolyte capable of providing practical coulombic efficiencies in high-voltage G||PBA cells, requiring further electrolyte development.2 Current research primarily focuses on developing electrolytes able to simultaneously passivate Al current collectors, resist oxidation at the high voltage of the cathode, and form a stable solid electrolyte interphase (SEI) on the anode,2 but frequently neglects electrolyte transport properties. Ionic transport in the electrolyte influences cell rate capability, low-temperature performance, and degradation, as the formation of concentration gradients introduces additional overpotentials and promotes irreversible side reactions.3 Accurate electrolyte transport property characterization is therefore critical to understand and optimize electrolyte performance.Through optimization of potassium metal electrode preparation, we conducted the first full characterization of a non-aqueous K-ion electrolyte, providing the concentration-dependent salt diffusivity, transference number, ionic conductivity, and thermodynamic factor of the potassium bis(fluorosulfonyl)imide (KFSI) in 1,2-dimethoxyethane (DME) system. We further compare these properties with those from the equivalent Li-ion electrolyte (LiFSI in DME), demonstrating that the K-ion electrolyte displays superior transport properties due to the lower charge density of K+ compared to Li+.4 However, full electrolyte characterization is traditionally a slow and laborious process, requiring large volumes of electrolyte and separate experimental setups to measure each property. An alternative approach is to utilize techniques capable of electrolyte concentration gradient visualization during polarization, which, when combined with measurement of the concentration overpotential, enable the full suite of transport and thermodynamic properties to be determined in a single experiment.5 This approach was implemented in a technique called operando Raman gradient analysis (ORGA) to characterize KFSI in triethyl phosphate (TEP), another promising K-ion electrolyte. ORGA gives results in agreement with the conventional state-of-the-art methods, while proving to be more electrolyte- and time-efficient.6 Full-cell modeling with these two K-ion electrolytes reveals the significant impact of transport properties on accessible capacity at high rates,7 demonstrating the need to consider electrolyte transport when designing future K-ion electrolytes, and highlighting the importance of fast and accurate techniques to measure these properties, such as ORGA.

Optimization of silica-doped BxCyNz monolayer anode for high-performance potassium metal batteries through modeling study

Within this piece of research, the performances of pure B2CN3 nanosheet (PB2CN3NS) and its doped structure with Si atoms (SB2CN3NS) as the anode materials of K-ion batteries (KIBs) were investigated using DFT. The findings showed that PB2CN3NS and SB2CN3NS are highly capable of adsorbing K with acceptable adhesion energy (AE). Also, because of the negative adhesion of K+, in comparison with K, K+ donated more electrons on PB2CN3NS and SB2CN3NS. Based on the results, SB2CN3NS provided an ideal condition for the K atoms to migrate on the surfaces of PB2CN3NS and SB2CN3NS because of their lower energy barrier. The computed theoretical storage capacity was approximately 1347 mAh.g−1 after the adhesion maximum K atoms onto PB2CN3NS and SB2CN3NS. This value is higher the values reported for many anodes materials fabricant in recent years. The open circuit voltage (VOC) of PB2CN3NS and SB2CN3NS were also found to be low, which were 0.19 and 0.25 V, respectively. The outcomes within this study can provide useful insights into producing highly efficient anodes for KIBs.

Sonochemical Synthesis of Potassium-Intercalated Carbon Allotropes: Bulk Formation at Ambient Room Temperature.

Intercalation can be used to alter the electronic properties of graphitic materials. Intercalation is, however, a notoriously brute-force process typically carried out at a high temperature in an inert environment for an extended period. As an exception to this, a simple sonication-assisted intercalation of potassium into graphite at ambient room temperature (RT) has been reported. Here we extend this approach to intercalation of potassium into other carbon allotropes, including planar graphene nanoplatelets (GNPs) and curved graphitic tubes and shells, such as multiwalled carbon nanotubes (MWCNTs) and nanodiamond-derived carbon nano-onions (NCNOs). We report the rapid room-temperature sonication-assisted potassium metal intercalation of GNPs, MWCNTs, and NCNOs. Powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and electron dispersive X-ray spectroscopy (EDS) were used to visualize the location of potassium in the intercalated products.

Exploring the mechanism of alkali metal K-catalyzed biomass char gasification using in-situ DRIFTS and molecular simulation

Although alkali metal potassium (K)-catalyzed char gasification has been widely studied, the detailed mechanism of this process is still not fully understood. To study this catalytic mechanism in more detail, high-temperature in-situ DRIFTS experiments were carried out for the gasification of cellulose char with K and cellulose char without K under H2O and O2 atmospheres, transient gasification experiment of char with K under H2O atmosphere, and char with K gasification under isotope water atmospheres. Peaks at 1945 cm−1 and 2020 cm−1 were observed. Combined with the theoretical spectra obtained by quantum chemical simulations and the prediction of catalytic gasification intermediates by molecular dynamics simulations, these two peaks were confirmed to represent char-polyynes species. Based on this result, a new mechanism is proposed: K interacts with carboxyl groups and aromatic ketones to promote desorption, thereby exposing active sites. Then, K reacts with the edge of the activated char to form numerous highly active char-polyynes species. The polyynes edge of this char-polyynes phase provides ideal adsorption–desorption sites, enabling further reaction with the gasifier. Thus, gas desorption is promoted. The adsorption and desorption peaks of catalytic gasification under the H2O atmosphere were located at 1400 cm−1 and 1300 cm−1, and these peaks represented stable adsorption states and unstable desorption precursors, respectively. Based on this, adsorption–desorption theory was analyzed more comprehensively, and the adsorption–desorption process was divided into three stages: initial adsorption, intermediate conversion, and desorption. The comprehensive new mechanism proposed in this paper provides a better understanding of the nature of char catalytic gasification at a deeper level.

Facile Synthesis of Potassium Decahydrido‐Monocarba‐closo‐Decaborate Imidazole Complex Electrolyte for All‐Solid‐State Potassium Metal Batteries

AbstractAll‐solid‐state potassium metal batteries have caught increasing interest owing to their abundance, cost‐effectiveness, and high energy/power density. However, their development is generally constrained by the lack of suitable solid‐state electrolytes. Herein, we report a new complex KCB9H10 ⋅ 2C3H4N2, synthesized by grinding and heating the mixture of potassium decahydrido‐monocarba‐closo‐decaborate (KCB9H10) and imidazole (C3H4N2) under mild conditions, to achieve the K‐ion superionic solid‐state electrolyte. The crystal structure was revealed as an orthorhombic lattice with the space group of Pna21 by FOX software. The diffusion properties for K+ in the crystal structure were calculated using the climbing image nudged elastic band (CI‐NEB) method. KCB9H10 ⋅ 2C3H4N2 exhibited a high ionic conductivity of 1.3×10−4 S cm−1 at 30 °C, four orders of magnitude higher than that of KCB9H10. This ionic conductivity is also the highest value of hydridoborate‐based K+ conductors reported. Moreover, KCB9H10 ⋅ 2C3H4N2 demonstrated a K+ transference number of 0.96, an electrochemical stability window of 1.2 to 3.2 V vs. K/K+, and good stability against the K metal coated by a layer of potassium imidazolate (KIm). These great performances make KCB9H10 ⋅ 2C3H4N2 a promising K‐ion solid‐state electrolyte.

Boosting K+‐Ionic Conductivity of Layered Oxides via Regulating P2/P3 Heterogeneity and Reciprocity for Room‐Temperature Quasi‐Solid‐State Potassium Metal Batteries

AbstractSolid‐state potassium metal batteries are promising candidates for grid‐scale energy storage due to their low cost, high energy density and inherent safety. However, solid state K‐ion conductors struggle with poor ionic conductivity due to the large ionic radius of K+‐ions. Herein, we report precise regulation of phase heterogeneity and reciprocity of the P2/P3‐symbiosis K0.62Mg0.54Sb0.46O2 solid electrolyte (SE) for boosting a high ionic conductivity of 1.6×10−4 S cm−1 at 25 °C. The bulk ionic conducting mechanism is explored by elucidating the effect of atomic stacking mode within the layered framework on K+‐ion migration barriers. For ion diffusion at grain boundaries, the P2/P3 biphasic symbiosis property assists in tunning the SE microstructure, which crystallizes in rod‐like particles with lengths of tens of micrometers facilitating long‐distance ion transport and significantly decreasing grain boundary resistance. Potassium metal symmetric cells using the modified SE deliver excellent cycling life over 300 h at 0.1 mA cm−2 and a high critical current density of 0.68 mA cm−2. The quasi‐solid‐state potassium metal batteries (QSSKBs) coupled with two kinds of layered oxide cathodes demonstrate remarkable stability over 300 cycles, outperforming the liquid electrolyte counterparts. The QSSKB system provides a promising strategy for high‐efficiency, safe, and durable large‐scale energy storage.

Boosting K+-Ionic Conductivity of Layered Oxides via Regulating P2/P3 Heterogeneity and Reciprocity for Room-Temperature Quasi-Solid-State Potassium Metal Batteries.

Solid-state potassium metal batteries are promising candidates for grid-scale energy storage due to their low cost, high energy density and inherent safety. However, solid state K-ion conductors struggle with poor ionic conductivity due to the large ionic radius of K+-ions. Herein, we report precise regulation of phase heterogeneity and reciprocity of the P2/P3-symbiosis K0.62Mg0.54Sb0.46O2 solid electrolyte (SE) for boosting a high ionic conductivity of 1.6×10-4 S cm-1 at 25 °C. The bulk ionic conducting mechanism is explored by elucidating the effect of atomic stacking mode within the layered framework on K+-ion migration barriers. For ion diffusion at grain boundaries, the P2/P3 biphasic symbiosis property assists in tunning the SE microstructure, which crystallizes in rod-like particles with lengths of tens of micrometers facilitating long-distance ion transport and significantly decreasing grain boundary resistance. Potassium metal symmetric cells using the modified SE deliver excellent cycling life over 300 h at 0.1 mA cm-2 and a high critical current density of 0.68 mA cm-2. The quasi-solid-state potassium metal batteries (QSSKBs) coupled with two kinds of layered oxide cathodes demonstrate remarkable stability over 300 cycles, outperforming the liquid electrolyte counterparts. The QSSKB system provides a promising strategy for high-efficiency, safe, and durable large-scale energy storage.

Fabrication and performance assessment of coin cell supercapacitors with multiwalled carbon nanotube-supported mixed metal oxide nanocomposites and redox additive electrolyte

In the realm of supercapacitor applications, the fabrication of coin cell supercapacitors with superior performances played a crucial role. In this work, an asymmetrical type coin supercapacitor was fabricated with multiwalled carbon nanotube supported mixed metal oxide (CuO/CoO@MWCNT - CCM) nanocomposites (NCs) and potassium ferrocyanide incorporated KOH based redox additive electrolyte (RAE). The synergistic effect and the enhanced conductivity by the mixed metal oxides and MWCNT, respectively, were acted as the performance enhancer for electrode performances. On the other hand, RAE with optimized concentration provided additional redox active sites for superior performances. The combined effect of CCM NCs and RAE, were responsible for the superior performances. CCM NCs were prepared by one-pot hydrothermal technique and characterized. Working electrodes with CCM NCs were fabricated by doctor blade method and evaluated in KOH and RAE. It exhibited 1838.55 Fg−1 of specific capacitance (Csp) in RAE. Assembled asymmetrical supercapacitors with CCM NCs modified working electrode and activated carbon based anode, delivered 123.91 Fg−1 of Csp at 2.75 Ag−1 in RAE. The assembled supercapacitors delivered the highest energy density of 27.53 Wh kg−1 and power density of 1875 W kg−1 in RAE with an impressive 82.89 % of cyclic retention after 5000 GCD cycles. Finally, an asymmetric coin cell supercapacitor (CR2302) was fabricated with CCM NCs and RAE. The fabricated coin cell delivered the charge and discharge capacities of 157.72 and 55.99 mAh g−1, respectively in KOH, whereas these values were significantly improved 172.46 and 126.2 mAh g−1 respectively, in RAE. It proved that the fabricated coin cell supercapacitors performed well in terms of maximum charge and discharge performances in RAE compared to conventional KOH.