K₃SbS₄ as a Potassium Superionic Conductor with Low Activation Energy for K–S Batteries

Abstract

Solid-state K-ion conducting electrolytes are key elements to address the current problems in K secondary batteries. Here, we report a sulfide-based Kion conductor K 3 SbS 4 with a low-activation energy of 0.27 eV. W-doped K 3À x Sb 1À x W x S 4 (x = 0.04, 0.06, 0.08, 0.10 and 0.12) compounds were also explored for increasing vacancy concentrations and improving ionic conductivity. Among them, K 2.92 Sb 0.92 W 0.08 S 4 exhibits the highest conductivity of 1.4 × 10 À 4 S cm À 1 at 40 °C, which is among the best reported potassium-ion conductors at ambient temperature. In addition, K 2.92 Sb 0.92 W 0.08 S 4 is electrochemically stable with long-chained potassium polysulfide of K 2 S x . A room-temperature solid potassium-sulfur (KÀ S) battery system has therefore been successfully demonstrated, which is the first KÀ S battery prototype using non-commercial inorganic-based electrolyte to block the polysulfide shuttle.

Uniform P2-K0.6CoO2 Microcubes as a High-Energy Cathode Material for Potassium-Ion Batteries

“…As shown in Figure 3h, potassium ions in the KCO microcubes shift through two-dimensional diffusion pathway, which can promote K + diffusion kinetics and conform to the characteristics of layered TM oxides. The mean square displacements of K + for the KCO microcubes at different temperatures are used to obtain the diffusion energy barrier (E a ), 39,40 as depicted in Figure S20. According to the slope of Arrhenius plot (Figure 3i), E a is calculated to be 286 meV.…”

Aprotic Sulfur–Metal Batteries: Lithium and Beyond

“…(d) Pictorial scheme of the structure of a potassium superionic conductor and (e, f) its experimental validation as a solid-state ceramic electrolyte in K-S batteries. [Adapted with permission from ref . Copyright 2022 Wiley.…”

“…In the past 10 years, the exploration of innovative chemistries for the exploitation of sulfur as the positive electrode active material in aprotic batteries has experienced a remarkable boom. ,,− Among all the possible variants, the Li-S formulation is the most advanced one and has been already demonstrated in pre-commercial prototypes. ,, There are several advantages in the technological shift from lithium-ion battery chemistry to lithium–sulfur in terms of the volumetric and gravimetric specific energies and specific capacities as well as the costs. The theoretical gravimetric and volumetric specific capacities of a Li-S cell (1167 mAh g –1 and 1216 mAh mL –1 , normalized by the masses and volumes of the active materials at both electrodes) are respectively 11 and 3 times larger compared to the LiCoO 2 /​graphite benchmarks or 7 and 2 times larger compared to a hypothetical advanced Li-ion battery formulation of LiFePO 4 /​silicon.…”

Achieving Fast and Reversible Sulfur Redox by Proper Interaction of Electrolyte in Potassium Batteries

“…During the electrochemical reduction of solid sulfur, stable potassium polysulfides (KPSs; K 2 S x , x = 5–6) are formed at high voltages and subsequently reduced to insoluble ones (K 2 S x , x = 1–3) at low voltages in the commonly used ether-based electrolyte. − Soluble KPSs enable sufficient extraction of sulfur species into electrolytes at a high capacity in the “solid–liquid–solid” pathway . However, it gives rise to the unfavorable polysulfide “shuttling effect”, whereby sulfur is irreversibly lost, which also occurs in other alkali metal–sulfur batteries. , Carbonate-based and solid-state electrolytes could reduce this issue because of the absence of long-chain KPSs along “solid–solid” or “quasi-solid” pathways. − Cleaving long-chain S 8 into short molecules was also effective to avoid the participation of long-chain KPSs. − But they caused critical problems, such as low voltage, low capacity, and unstable solid electrolyte interphase (SEI) on the K metal anode.…”