Customized Electrolyte and Host Structures Enabling High-Energy-Density Anode-Free Potassium–Metal Batteries

Abstract

Potassium shows great potential to replace lithium in energy storage for its high abundance and comparable energy density. However, issues including an unstable interphase, dendrite growth, and volume change restrict the development of potassium metal batteries, and so far, there is no single cure that works once and for all.Here an anode-free potassium metal battery is demonstrated by introducing a customized electrolyte and host structures that simultaneously promote efficiency, reversibility, and energy density. First, a diluted high-concentration electrolyte with fast kinetics and high stability triggers an inorganic-rich durable interphase. Meanwhile, a carbonaceous host containing narrowly distributed mesopores (MCNF) favors reduced surface area but enough inner space. Together, they achieve a high average Coulombic efficiency (CE) of 99.3% and an initial CE of 95.9% at 3 mA cm −2 −3 mA h cm −2 . Anodefree MCNF||Prussian blue (PB) potassium cells are delivered with 100 reversible cycles and a high energy density of 362 W h kg −1 .

Anion‐Reinforced Solvation Structure Enables Stable Operation of Ether‐Based Electrolyte in High‐Voltage Potassium Metal Batteries

“…Besides, the decomposition of FSI − anions is simultaneously detected by the signal of −CF 3 − at 291.6 eV in C 1s spectra and −SO x − species at 532.9 eV in O 1s spectra. As shown in Figure 4b–4d, KF (683.7 eV) and −CF 2 −/−CF 3 − (688.6 eV) in F 1s spectra, KSON (399.4 eV) in N 1s spectra, and K 2 SO 4 (171.0 eV), K 2 SO 3 (170.1 eV), and K 2 S 2 O 3 (168.8 eV) in S 2p spectra are monitored, which are derived from FSI − anions [7a,19d] . And these peaks intensity of inorganic species in MB distinctly exceed than that of DM.…”

Recent Progress of Potassium Metal Anodes: How to Regulate the Growth of Dendrite

“…[171]. In spite of these achievements of the anode-free system in Li and Na, there are only a few reports about anode-free PMBs [76,172,173].…”

“…Hence, comprehensive strategies should be devoted to realizing stable anode-free PMBs. Recently, Li et al reported an anode-free PMB in a diluted high-concentration electrolyte (DHCE) with a mesoporous fibrous host (MCNF) [173]. DHCE contributed to the construction of an anion-derived SEI layer, which was more robust compared to that of 1 M KFSI/DME (further discussed in (3) Highly Concentrated Electrolytes).…”

“…DHCE contributed to the construction of an anion-derived SEI layer, which was more robust compared to that of 1 M KFSI/DME (further discussed in (3) Highly Concentrated Electrolytes). Moreover, MCNF could suppress the volume fluctuations with enough inner room for K storage, providing sufficient capacity of K. As a result, an anode-free MCNF full cell with K 1.18 Fe[Fe(CN) 6 ] 0.82 •0.47H 2 O delivered a high energy density of 362 Wh kg -1 [173].…”

Design Principles of Mediation Layer for Current Collectors Toward High‐Performance Anode‐Free Potassium‐Metal Batteries: A Case Study of Cu6Sn5 on Copper

“…[24] Despite great advances, most of these modification layers introduced by the slurry coating method are prone to peeling off. [25][26][27][28] In addition, the organic binder component can trap K ions, which would decrease the coulombic efficiency and lifespan of the anode-free full-cells. Moreover, a deep theoretical understanding of the functional mechanism of the mediation layers at the atomic level is still scarce in the literature.…”