Potassium Bis Research Articles

Uniform carbon coating and solid electrolyte interphase synergistically enhanced exceptional anodic K‐ion storage properties of stable KTiOPO4 single crystals

AbstractSearching for low‐cost, high‐capacity, high‐power, high‐stability, high‐tap‐density, and inherently safe materials for developing cheap, safe, and high‐performance batteries has always been a research hotspot. Herein, an inherently safe, low‐cost, and low‐strain KTiOPO4 (KTOP) submicron single crystals with a uniform thin layer carbon coating are developed using a ball‐mill assisted solid‐state method. Uniform solid electrolyte interphase, carbon coating, and inherently stable structure synergistically help compact KTOP submicron single crystals achieve an exceptional anodic K‐ion storage performance. The carbon‐coated KTOP single crystals obtained under the carbonization temperature of 400°C (KTOP‐C‐400) can deliver an exceptional potassium ion storage performance of 253.3, 224.0, 175.5, and 131.1 mA h g−1 at the current density of 100, 200, 500, and 1000 mA g−1, respectively, in the electrolyte of 5 M potassium bis(fluorosulfonyl)imide (KFSI) in DIGLYME electrolytes. Even after being cycled at 1000 mA g−1 for 1000 cycles, the capacity was maintained at 182.5 mA h g−1 with a coulombic efficiency of 99.9%.

Highly Concentrated Asymmetric KTFSI for Aqueous Potassium Ion Batteries

AbstractPotassium imide salt (KCTFSI), featuring cyano (C≡N) and trifluoromethanesulfonyl (TFSI) branches, is reported for the first time as a promising electrolyte for aqueous potassium‐ion batteries (KIBs). In contrast to the limited solubility of symmetric KTFSI (1.5m), asymmetric KCTFSI achieves a high saturation concentration of 32.2m within a “water‐in‐salt” region. Experimental and theoretical studies reveal that the remarkable enhancement of solubility is associated with the asymmetry of CTFSI anions and likely the preferential formation of contact‐ion pairs through C≡N coordination. The 32.2m KCTFSI solution not only extends the electrochemical stability window (3.80 V on Al) but also maintains a liquid state at low temperatures (−15 °C) for an extended period, in sharp contrast to the immediate solidification of potassium bis(fluorosulfonyl)imide (KFSI, 30m) and potassium trifluoromethanesulfonate (KOTF, 22m) solutions. Thanks to its wide voltage window and supercooling behavior, KCTFSI demonstrates excellent compatibility with perylene‐3,4,9,10‐tetracarboxylic diimide (PTCDI) anode and KVPO4F (or K2Fe[Fe(CN)6]·2H2O) cathode over a wide temperature range. For instance, full cells of PTCDI/KCTFSI/KVPO4F exhibit reasonable cyclability with an average discharge voltage of 1.7 V over 300 charge/discharge cycles at −15 °C. it is anticipated that this work will inspire new designs of hybrid electrolytes based on CTFSI to advance the realization of viable aqueous KIBs.

Interlayer expansion and conductive networking of MoS2 nanoroses mediated by bio-derived carbon for enhanced potassium-ion storage

Potassium-ion batteries (PIBs) represent a promising battery technology for energy storage applications. Nevertheless, the progress of PIBs is still hindered by the lack of electrode materials that allow rapid and repeatable accommodation of the large K+ ions. Herein, a composite anode material containing interlayered-expanded MoS2 (55.6% larger) nanoroses in carbon nanonets (MoS2/C@CNs) is designed with the assistance of biomass bagasse, of which the dual carbon sources convert into interlayer and skeleton carbon, respectively. The unique structure facilitates electron/ion transport in the entire electrode and offers excellent structural stability, leading to much improved electrochemical performance compared to simple MoS2/C composite and pure MoS2. Furthermore, the role of electrolyte salts (potassium hexafluorophosphate and potassium bis(fluorosulfonyl)imide) and the electrolyte concentration on the interfacial properties in PIBs have been explored. The results indicate that the low-concentration potassium bis(fluorosulfonyl)imide electrolyte helps to produce optimized organic-inorganic solid electrolyte interface films, contributing to a capacity retention of 90% after 1,000 cycles at 2 A g-1.

A novel imidazolium-based small molecule matching with unique solvation structure electrolyte for superior K-storage stability

Organic anodes for K-storage have attracted much attention because of high theoretical capacity, low cost and extensive natural resource although facing serious dissolving issues with conventional electrolytes and persistent capacity decay. Therefore, 2-methylimidazole (mIm), an imidazolium-based small molecule restricted with high electronic conductivity carbon nanotubes (mIm/CNTs) is applied for potassium-ion batteries (PIBs). Furthermore, this as-prepared anode is accompanied to the potassium bis(fluorosulfonyl)imide (KFSI)-ethylene carbonate (EC) and diethyl carbonate (DEC) electrolytes (KFSI/EC + DEC) with modifiable solvation structures. At current density of 50 mA g−1, the mIm/CNTs composite coupled with the optimized 3 mol L−1 KFSI/EC + DEC electrolyte provides an average reversible capacity of 240 mAh g−1 (composites) with coulombic efficiency (CE) of 99.5 %. After 500 cycles, a high sustained capacity of 200 mAh g−1 (composites) is attained at 200 mA g−1. This enhanced K-storage performance of mIm/CNTs in 3 mol L−1 KFSI/EC + DEC electrolyte can be attributed to distinctive solvation structure, which is dominated by contact ion pairs (CIPs) and aggregates (AGGs). This structure intensively mitigates dissolution issues and greatly promotes K+ reaction kinetics. This work emphasizes the significance of electrolyte regulation for organic anodes and will supply a comprehensive appreciating of electrochemistry performance for advanced energy storage systems.

Ring Contraction by Rearrangement of Sterically Congested Cyclic (Amino)(aryl)carbenes.

The rearrangement of sterically congested cyclic (amino)(aryl)carbenes (CAArCs) by the reaction of related iminium salts with potassium bis(trimethylsilyl)amide is reported, allowing for forming benzocyclobutanimines via a ring contraction process. Mechanistic studies by theoretical calculations indicate that the formation of conjugated ketenimines as intermediates could be considered, in which steric hindrance caused by N-alkyl motifs of CAArCs plays an important role in promoting the ring-opening by the cleavage of C-N bond.

Synthesizing hard carbon anodes for potassium-ion batteries from black liquor and deinking sludge

Porous hard carbon anodes, with large interlayer space and high adsorption ability, can offer much better cycle stability and higher discharge capacity for potassium-ion batteries compared to commercial graphite anodes. However, most commercial hard carbons are synthesized from relatively expensive high-molecular polymers. In this study, pulping and papermaking wastes were utilized as precursors for producing hard carbons and pore-enlarging agent, respectively. Specifically, after thorough mixing through ball milling, black liquor solids and deinking sludge were utilized to produce porous hard carbon anodes via co-pyrolysis. The results show that direct pyrolysis of black liquor can produce hard carbons efficiently, eliminating the need to extract lignin from black liquor. Moreover, it is shown that the pore-enlarging agent derived from deinking sludge can enlarge much portion of pores on hard carbons, resulting in abundant mesopores. Electrochemical tests demonstrate that the synthesized porous hard carbon anodes can achieve highest specific capacity of 303.5 mAh g−1 at 100 mA g−1 using a 1.0 M potassium hexafluorophosphate electrolyte in a mixture of diethyl carbonate and ethylene carbonate. Additionally, the synthesized porous hard carbon anodes exhibit low average capacity decay per cycle of 0.06 % at 100 mA g−1 when tested with a 1.0 M potassium bis(fluorosulfonyl)imide electrolyte in the same solvent mixture after 500 cycles. Therefore, recycling black liquor and deinking sludge to produce porous hard carbon anodes for potassium-ion batteries is a promising approach for environmental and energy sustainability.

Long-life potassium metal batteries enabled by anion-derived solid electrolyte interphase using concentrated ionic liquid electrolytes

Potassium metal batteries (PMBs) show great potential as next-generation energy storage systems yet face challenges such as the dendritic growth of the potassium anode, leading to issues with cycle life and safety. This study reports a potassium salt-concentrated ionic liquid electrolyte (PCIL) consisting of potassium bis(fluorosulfonyl)imide (KFSI) and 1-methyl-1-propyl pyrrolidinium bis(fluorosulfonyl)imide (Pyr13FSI) to achieve long-life and, safe PMBs. PCIL presents several advantages including outstanding oxidation stability (≈5.2 V), decent ionic conductivity (4.0 mS cm−1 at 25 °C), and negligible flammability. Moreover, PCIL promotes the development of anion-derived solid-electrolyte interphase (SEI) with high inorganic content. This not only hinders the growth of potassium dendrites but also facilitates facile interfacial charge transfer kinetics. Benefiting from these advantages, PMBs (K||KVPO4F) employing PCIL exhibit remarkable cycle performances at both ambient and elevated temperatures (capacity retention after 300 cycles: 74.8% at 25 °C and 82.9% at 45 °C), surpassing the performance of conventional carbonate (1 M KPF6 EC/PC) and dilute potassium ionic liquid electrolyte (PIL). This work demonstrates the tangible capability of PCIL in realizing practical PMBs.

Enabling High‐Performance Potassium‐Ion Batteries by Manipulating Interfacial Chemistry

AbstractAs a promising candidate for the flame‐retardant electrolyte, triethyl phosphate (TEP)/potassium bis(fluorosulfonyl)amide (KFSI)‐based electrolyte has drawn much attention in the K‐ion battery community. Although the TEP/KFSI formula at a moderate main salt concentration (normally, <3 m) enables the compatibility of the reactive K metal anode, the long‐standing oxidative instability of KFSI salt remains unsolved. Here, an additive strategy is reported to address the high‐voltage issue in the TEP/KFSI electrolyte, and generalize it to the other KFSI‐based electrolytes. The addition of potassium nitrate changes the surface charge distribution and effectively suppresses the decomposition of KFSI toward the high‐voltage cathode. The nitrate‐containing electrolyte enables superior stability of a 4.3 V‐class K‐ion battery, as evidenced by its 80% capacity retention over 2000 cycles (≈6 months) at the 1 C rate. Moreover, the long‐cycling stability of the graphite‐based full cell with Prussian Blue cathode is demonstrated.

Interior-Confined Vacancy in Potassium Manganese Hexacyanoferrate for Ultra-Stable Potassium-Ion Batteries.

Metal hexacyanoferrates (HCFs) are viewed as promising cathode materials for potassium-ion batteries (PIBs) because of their high theoretical capacities and redox potentials. However, the development of an HCF cathode with high cycling stability and voltage retention is still impeded by the unavoidable Fe(CN)6 vacancies (VFeCN) and H2O in the materials. Here, a repair method is proposed that significantly reduces the VFeCN content in potassium manganese hexacyanoferrate (KMHCF) enabled by the reducibility of sodium citrate and removal of ligand H2O at high temperature (KMHCF-H). The KMHCF-H obtained at 90 °C contains only 2% VFeCN, and the VFeCN is concentrated in the lattice interior. Such an integrated Fe-CN-Mn surface structure of the KMHCF-H cathode with repaired surface VFeCN allows preferential decomposition of potassium bis(fluorosulfonyl)imide (KFSI) in the electrolyte, which constitutes a dense anion-dominated cathode electrolyte interphase (CEI) , inhibiting effectively Mn dissolution into the electrolyte. Consequently, the KMHCF-H cathode exhibits excellent cycling performance for both half-cell (95.2 % at 0.2 Ag-1 after 2000 cycles) and full-cell (99.4 % at 0.1 Ag-1 after 200 cycles). This thermal repair method enables scalable preparation of KMHCF with a low content of vacancies, holding substantial promise for practical applications of PIBs.

Balancing salt concentration and fluorinated cosolvent for graphite cathode-based dual-ion batteries

High-concentration electrolytes (HCEs) are favored in graphite cathode-based dual-ion batteries (DIBs) due to their high oxidative stability and good interphase compatibility with both anode and cathode. Although a localized high-concentration electrolyte (LHCE) with the similar solvation structure as HCE is proposed for graphite cathode by adding weakly solvated fluorinated cosolvents, the balance between salt concentration and fluorinated cosolvent has not been investigated. Herein, various electrolytes were prepared by introducing tris(2,2,2-trifluoroethyl) phosphate (FTEP) into the HCE composed of potassium bis(fluorosulfonyl)imide (KFSI) and triethyl phosphate (TEP), and the moderate concentrated electrolyte at the TEP/FTEP volume ratio of 5:1 can stabilize K/graphite DIBs with the capacity of 45 mAh g−1 after 300 cycles at 0.5 A g−1. The abundant ion–solvent complexes as HCE and the entrance of FTEP contribute to building stable FSI−-derived cathode/electrolyte interphase with the KF-rich inner layer. Importantly, FTEP replaces partial TEP solvents to coordinate with FSI−, enhancing the electrolyte oxidative stability, whereas their weak interaction further suppresses the solvent co-intercalation. As a proof, this electrolyte enables high output voltage (3.75 V) and good cyclability of dual-ion full cells coupled with tellurium anode. This work will promote the development of fluorinated cosolvent-modified LHCEs for high-performance DIBs.

Polyimide-Based Aqueous Potassium Energy Storage Systems Using Concentrated WiSE Electrolyte.

Aqueous batteries are considered as promising alternative power sources due to their eco-friendly, cost-effective, and nonflammable attributes. Employing organic-based electrode materials offers further advantages toward building greener and sustainable systems, owing to their tunability and environmental friendliness. In order to enhance the energy and power densities, superconcentrated aqueous electrolytes, such as water-in-salt electrolytes (WiSE), have renewed the interest in aqueous batteries due to their enhanced stability and much wider electrochemical stability window (>1.23 V) compared with the traditional aqueous electrolytes. Here, we present a perylene diimide-based electrode material (PDI-Urea) as an appealing anode for aqueous potassium energy storage systems and investigate their electrochemical performance in three WiSE electrolytes, namely, 30 M potassium acetate, 40 M potassium formate and 30 M potassium bis(fluorosulfonyl)imide (KFSI). To explore the potential of PDI-Urea for potassium-based electrochemical energy systems, we fabricated full cell devices such as aqueous potassium dual-ion battery (APDIB) and aqueous K-ion battery (AKIB) and studied their electrochemical properties with 30 M KFSI electrolyte. The full cell K-ion battery, using a PBA cathode, exhibited excellent electrochemical performance with good rate capability and impressive capacity retention of 91% upon 1000 cycles. Further, the reaction mechanism of the electrodes is systematically analyzed using ex-situ studies.

An inorganic molten salt electrolyte-based Li-CO2 battery with moderate working temperature and enhanced performance.

Herein, a binary inorganic molten salt electrolyte based on lithium bis(fluorosulfonyl)imide (LiFSI) and potassium bis(fluorosulfonyl)imide (KFSI) is applied to Li-CO2 batteries that can operate under 80 °C. Benefiting from the intrinsic nonvolatility, electrochemical stability, raised ionic conductivity, sufficient solubility and safety, the molten electrolyte endows the Li-CO2 battery with a large discharge capacity of 4612 mA h g-1 and superior rate capability. The introduction of the Ru@Super P carbon cathode further optimizes the discharge capacity (9503 mA h g-1), overpotential (1.15 V), and rate capability.

(Invited) All-Solid-State Na- and K-Ion Batteries with Dry Polymer Electrolytes

The development of sodium-ion and potassium-ion batteries has gained increasing attention as a sustainable and cost-effective alternative to lithium-ion batteries, due to the abundance of their constituent elements.[1]-[3] All-solid-state batteries offer high safety advantages in high-temperature conditions, as their solid composition reduces the risk of leakage or ignition of the organic electrolyte. As large-scale and stationary batteries for energy storage applications require safety and durability in wide-temperature operations, all-solid-state sodium-ion and potassium-ion batteries can provide a potential solution.This study presents the fabrication of all-solid-state sodium batteries, using dry polymer electrolytes, optimized for stable operation at 60 °C.[4] A composite electrode with uniformly dispersed conductive carbon and binder polymer is essential to achieve a stable charge-discharge reaction in all-solid-state cell, due to the absence of the liquid electrolyte penetrated in the electrode pores. The use of a polymer electrolyte as a binder polymer provides an effective ionic conduction path inside the electrode, which allows stable charge-discharge reaction even at the thick composite electrodes. The fabricated all-solid-state Na // P2-Na2/3[Ni1/3Mn2/3]O2 cell exhibits superior cycle performance at 60 °C, compared to the liquid electrolyte. Furthermore, coating P2-Na2/3[Ni1/3Mn2/3]O2 with Al-oxide enhances the capacity retention of the P2-Na2/3[Ni1/3Mn2/3]O2 // hard carbon full cell, with a mean discharge voltage of 3.11 V and energy density of 148 Wh (kg of active material)−1. To the best of our knowledge, this is the highest value ever reported for full-cell operation of an all-solid-state sodium-ion battery using a dry-polymer electrolyte.The study also reports the fabrication of all-solid-state potassium batteries, where the effects of K metal pretreatment on the K metal/solid polymer electrolyte interface were investigated.[5] The use of K metal chunk, pretreated with the electrolytes containing potassium bis(fluorosulfonyl)amide (KFSA), effectively suppressed polarization and interfacial resistance during continuous K metal stripping-deposition reactions in the cross-linked polymer electrolyte, poly[ethylene oxide-co-2-(2-methoxyethoxy)ethyl glycidyl ether-co-allyl glycidyl ether] (P(EO/MEEGE/AGE)). The addition of 1,3,2-dioxathiolane 2,2-dioxide (DTD) to the pretreatment solution further decreased polarization and interfacial resistance, due to the formation of a stable passivation layer on K metal by FSA− ions and DTD. The efficient operation of the potassium iron hexacyanoferrate positive electrode and graphite negative electrode in P(EO/MEEGE/AGE), with the K metal counter electrode, was achieved by effectively suppressing interfacial resistance through pretreatment. Stable K metal counter electrode for all-solid-state potassium cell was also beneficial to design full cell of all-solid-state potassium-ion cell, enabling us to fabricate the first 3 V-class all-solid-state K-ion battery operated at room temperature.

Perylene-Tetracarboxylic Diimide (PTCDI) Organic Cathode for Nonflammable K-Ion Batteries

3,4,9,10-Perylene-tetracarboxylic diimide (PTCDI) is an advanced and low-cost organic small-molecule electrode with 2-electron reaction (theoretical specific capacity CT=137 mAh g-1) in potassium ion batteries (PIBs). However, K metal anode is exceedingly active and risky. In order to eliminate security risks of K-metal batteries, triethyl phosphate (TEP) as a kind of cheap and nonflammable electrolyte is used for an extinguisher in K-ion batteries. In this paper, using 2 mol L-1 potassium bis(fluoromethanesulfonyl)imide (KFSI)/TEP electrolyte, PTCDI can show a highly stable cycle of 134 mAh g-1 after 100 cycles at 50 mA g-1 with a capacity retention radio of 98% (1.5-3.5 V). At a large current density of 500 mA g-1 (3.65 C), PTCDI also can deliver the capacity of 60 mAh g-1. And the safety of K-metalIIPTCDI PIBs is demonstrated by the fact that the used separator does not produce an open flame after ignition. These results of PTCDI can represent the advanced properties of organic cathode using TEP in PIBs.

Ultrastable Dendrite-Free Potassium Metal Batteries Enabled by Weakly-Solvated Electrolyte.

Potassium (K) metal is considered one of the most promising anodes for potassium metal batteries (PMBs) because of its abundant and low-cost advantages but suffers from serious dendritic growth and parasitic reactions, resulting in poor cyclability, low Coulombic efficiency (CE), and safety concerns. In this work, we report a localized high-concentration electrolyte (LHCE) consisting of potassium bis(fluorosulfonyl)imide (KFSI) in a cosolvent of 1,2-dimethoxyethane (DME) and 1,1,2,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) to solve the problems of PMBs. TTE as a diluent not only endows LHCE with advantages of low viscosity, good wettability, and improved conductivity but also solves the dendrite problem pertaining to K metal anodes. Using the formulation of LHCE, a CE of 98% during 800 cycles in the K||Cu cell and extremely stable cycling of over 2000 h in the K||K symmetric cell are achieved at a current density of 0.1 mA cm-2. In addition, the LHCE shows good compatibility with a Prussian Blue cathode, allowing almost 99% CE for the K||KFeIIFeIII(CN)6 full cell during 100 cycles. This promising electrolyte design realizes high-safety and energy-dense PMBs.

Boosting the “Solid–Liquid–Solid” Conversion Reaction via Bifunctional Carbonate‐Based Electrolyte for Ultra‐long‐life Potassium–Sulfur Batteries

AbstractPotassium–sulfur (K−S) batteries have attracted wide attention owing to their high theoretical energy density and low cost. However, the intractable shuttle effect of K polysulfides results in poor cyclability of K−S batteries, which severely limits their practical application. Herein, a bifunctional concentrated electrolyte (3 mol L−1 potassium bis(trifluoromethanesulfonyl)imide in ethylene carbonate (EC)) with high ionic conductivity and low viscosity is developed to regulate the dissolution behavior of polysulfides and induce uniform K deposition. The organic groups in the cathode electrolyte interphase layer derived from EC can effectively block the polysulfide shuttle and realize a “solid–liquid–solid” reaction mechanism. The KF‐riched solid‐electrolyte interphase inhibits K dendrite growth during cycling. As a result, the achieved K−S batteries display a high reversible capacity of 654 mAh g−1 at 0.5 A g−1 after 800 cycles and a long lifespan over 2000 cycles at 1 A g−1.

Boosting the "Solid-Liquid-Solid" Conversion Reaction via Bifunctional Carbonate-Based Electrolyte for Ultra-long-life Potassium-Sulfur Batteries.

Potassium-sulfur (K-S) batteries have attracted wide attention owing to their high theoretical energy density and low cost. However, the intractable shuttle effect of K polysulfides results in poor cyclability of K-S batteries, which severely limits their practical application. Herein, a bifunctional concentrated electrolyte (3 mol L-1 potassium bis(trifluoromethanesulfonyl)imide in ethylene carbonate (EC)) with high ionic conductivity and low viscosity is developed to regulate the dissolution behavior of polysulfides and induce uniform K deposition. The organic groups in the cathode electrolyte interphase layer derived from EC can effectively block the polysulfide shuttle and realize a "solid-liquid-solid" reaction mechanism. The KF-riched solid-electrolyte interphase inhibits K dendrite growth during cycling. As a result, the achieved K-S batteries display a high reversible capacity of 654 mAh g-1 at 0.5 A g-1 after 800 cycles and a long lifespan over 2000 cycles at 1 A g-1 .

Characterising the Ionic Transport and Thermodynamic Properties of Potassium-Ion Electrolytes

The lithium price has increased more than sevenfold since the start of 2021 (as of May 2022), reaching unprecedented price levels and demonstrating significant challenges for the security of supply of lithium for lithium-ion batteries (LIBs)1. With forecasts showing a potential significant lithium supply deficit by 20301, the case for alternative chemistries based on abundant minerals which can fulfil some LIB functions has never been stronger. Sodium-ion batteries (NIBs) and potassium-ion batteries (KIBs) are emerging as promising complementary technologies to lithium-ion batteries (LIBs) due to the availability and low cost of sodium and potassium, and the minerals comprising their leading electrodes2 , 3. KIBs have a significant advantage over NIBs as K+ can reversibly intercalate into the graphite electrodes used in LIBs, thus one of the primary components of KIBs is already available at commercial scale, unlike for NIBs2. The lower charge density of K+ compared to Li+ has also been suggested to result in superior ion transport in the electrolyte with KIBs potentially able to deliver superior rate capability and low-temperature performance. However, a comprehensive characterisation of the ionic transport and thermodynamic properties of nonaqueous K-ion electrolytes, critical to the development of KIBs, has not yet been reported. Here, for the first time, we fully characterise the ionic transport and thermodynamic properties of a nonaqueous K-ion electrolyte4, potassium bis(fluorosulfonyl)imide (KFSI) in 1,2-dimethoxyethane (DME) and compare it with its Li-ion equivalent (LiFSI in DME) over the concentration range 0.25–2 m. This was realised by developing a K metal preparation protocol enabling sufficient K metal stability for electrolyte characterisation. Our results demonstrate that the K-ion electrolyte indeed displays significantly higher salt diffusion coefficients and transference numbers than the Li-ion electrolyte, evidencing the potential for high-power applications of KIBs. IEA. Global EV Outlook 2022. (IEA, 2022).Dhir, S., Wheeler, S., Capone, I. & Pasta, M. Outlook on K-Ion Batteries. Chem vol. 6 2442–2460 (2020). doi: 10.1016/j.chempr.2020.08.012Hosaka, T., Kubota, K., Hameed, A. S. & Komaba, S. Research Development on K-Ion Batteries. Chem. Rev. acs.chemrev.9b00463 (2020) doi:10.1021/acs.chemrev.9b00463.Dhir, S., Jagger, B., Maguire, A. & Pasta, M. Characterising the Ionic Transport and Thermodynamic Properties of Potassium-ion Electrolytes. Res. Sq. (2022) doi:10.21203/RS.3.RS-2310020/V1. Figure 1

Regulating anion chemistry with F-containing bonds enable superior potassium ions storage in hard carbon

The high reactivity of potassium metal and the large potassium ion radius lead to increased side reactions and poor stability at the electrode/electrolyte interface. Constructing a stable electrode/electrolyte interface is essential to develop high-performance potassium ion storage devices. Herein, we propose an anion chemistry strategy to enhance interfacial stability by modulating the F-containing bonds in electrolyte potassium salts. Compared to C-F and P-F bonds, the experimental results, together with theoretical calculations, revealed that the S-F bonds are more likely to break to facilitate the formation of dense, robust, stable and KF-rich SEI films with high ionic conductivity. Meanwhile, the electrochemical impedance spectroscopy reveals the unique role of S-F-containing potassium bis(fluorosulfonyl)imide (K((FSO2)2N), KFSI) electrolytes in stabilizing potassium metal, which inhibits electrolyte decomposition and potassium dendrite formation. The synergistic stabilization of electrode and potassium metal by KFSI electrolyte effectively boosts the Coulomb efficiency, rate capability (4.7 and 1.8 times higher than those obtained with P-F and C-F-containing electrolytes) and cycling performance (capacity retentions of 80.4%, 1.4% and 47.7% for S-F, P-F and C-F-containing electrolytes after 1000 cycles at 1 A g−1, respectively) of hard carbon anode. This work reveals the importance of anion chemistry in regulating interfacial properties and provides a valuable insight into the rational design of interfacial chemistry.

Potassium Bis(fluorosulfonyl)imide Is an Effective Additive for Improving Anode Cyclability in Sulfolane-Based Electrolytes for Li–S Batteries

Potassium Bis(fluorosulfonyl)imide Is an Effective Additive for Improving Anode Cyclability in Sulfolane-Based Electrolytes for Li–S Batteries