A highly concentrated electrolyte for high-efficiency potassium metal batteries

Abstract

A highly concentrated electrolyte enables dendrite-free cycling of K metal anodes with a high CE (over 98% over 400 cycles).

Critical Roles of Mechanical Properties of Solid Electrolyte Interphase for Potassium Metal Anodes

“…66 eV) peaks in F 1s spectra (Figure 4c) and the KHSO 4 /KFSI (169.89 eV), K 2 SO 4 (168.64 eV) and K 2 SO 3 (166.76 eV) peaks in S 2p spectra originate mainly from the decomposition of KFSI and all become more intense as the electrolyte concentration increases. [ 8a,23a ] As shown in Figure 4e, the carbon content of the SEI increases from 70.5 to 84.9 at% as the KFSI concentration decreases from 2 to 0.25 m . [ 8a ] Such high carbon contents indicate that the SEIs formed in the four concentrations of KFSI/EC‐DEC electrolyte are all dominated by organic components.…”

“…[ 8a,23a ] As shown in Figure 4e, the carbon content of the SEI increases from 70.5 to 84.9 at% as the KFSI concentration decreases from 2 to 0.25 m . [ 8a ] Such high carbon contents indicate that the SEIs formed in the four concentrations of KFSI/EC‐DEC electrolyte are all dominated by organic components. With the increasing concentration of KFSI, an increment in the inorganic component content is verified in the percentages of inorganic matter in the SEI (Figure 4f) and is also reflected in the percentage of elements like N, F, S, K (Figure 4e).…”

“…[ 3b,4d,7 ] High‐concentration electrolytes (HCE) are intensively exploited in both aqueous and organic systems. [ 4b,8 ] The substantially altered ion solvation structure in HCE breeds a variety of unique bulk and interfacial features, [ 2b,9 ] which benefit battery performance in many aspects, such as improving electrolyte stability at high voltages and forming more protective SEIs [ 10 ] for alloy and metal anodes. However, the high viscosity, low wettability, and high cost of HCE greatly hinder their practical application.…”

“…The stability of the SEI contributes directly to the coulombic efficiency (CE) and continuance of the battery and is one of the most important criteria in electrolyte design. [ 2d,4c,d,8e,g,15 ] However, among the many qualities of SEI, the orienting role of its mechanical properties in electrolyte regulation has rarely been reported. More drastic volume changes during charging and discharging increase the dependence of emerging metal batteries on the mechanical stability of SEI.…”

“…K metal batteries have become a strong contender for large‐scale energy storage due to their advantages in sustainability and cost. [ 2c,d,3b,8d,16 ] Previous achievements in the stabilization of K‐metal anodes have mainly been achieved using 3D porous collectors, [ 16a,17 ] artificial SEI layers, [ 15a,b ] surface modification of potassium or copper plates, [ 18 ] modified test protocols, [ 19 ] and mostly in ether‐based electrolytes. [ 3b,20 ] In contrast, the progress with carbonate‐based electrolytes is not satisfactory.…”