Bifunctional Alloy/Solid-Electrolyte Interphase Layer for Enhanced Potassium Metal Batteries Via Prepassivation

Abstract

Potassium (K) metal batteries have attracted great attention owing to their low price, widespread distribution, and comparable energy density. However, the arbitrary dendrite growth and side reactions of K metal are attributed to high environmental sensitivity, which is the Achilles’ heel of its commercial development. Interface engineering between the current collector and K metal can tailor the surface properties for K-ion flux accommodation, dendrite growth inhibition, parasitic reaction suppression, etc. We have designed bifunctional layers via prepassivation, which can be recognized as an O/F-rich Sn–K alloy and a preformed solid-electrolyte interphase (SEI) layer. This Sn–K alloy with high substrate-related binding energy and Fermi level demonstrates strong potassiophilicity to homogeneously guide K metal deposition. Simultaneously, the preformed SEI layer can effectually eliminate side reactions initially, which is beneficial for the spatially and temporally KF-rich SEI layer on K metal. K metal deposition and protection can be implemented by the bifunctional layers, delivering great performance with a low nucleation overpotential of 0.066 V, a high average Coulombic efficiency of 99.1%, and durable stability of more than 900 h (1 mA cm–2, 1 mAh cm–2). Furthermore, the high-voltage platform, energy, and power densities of K metal batteries can be realized with a conventional Prussian blue analogue cathode. This work provides a paradigm to passivate fragile interfaces for alkali metal anodes.

Approaching Microsized Alloy Anodes via Solid Electrolyte Interphase Design for Advanced Rechargeable Batteries

“…[52,54] (3) Metallic tin (Sn) is a low-cost, environmentally friendly material that is abundant in nature. [55][56][57][58] It shows a high theoretical capacity and proper average reaction potential, that is, 994 mAh g −1 and ≈0.55 V versus Li/Li + ; 847 mAh g −1 and ≈ 0.35 V versus Na/Na + . [59,60] (4) Metallic antimony (Sb) for NIBs and KIBs is also a promising anode candidate owing to decent theoretical specific capacity (660 mAh g −1 ), proper reaction potential (≈0.4-0.8 V for Na and ≈0.4-0.5 V for K), and relatively high electronic conductivity (2.5×10 4 S cm −1 ).…”

“…[24,184] Designing a proper artificial protective layer has been deemed an effective approach to regulating and stabilizing the SEI layer through tuning electrolyte reduction kinetics. [58] For example, mechanical buffer layers have been employed to solve the structural stability challenges of microsized alloy anodes. [185,186] The satisfactory mechanical properties of the protective layer are conducive to accommodating the volume change of high-capacity alloy anodes and stabilizing native SEI.…”

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

“…To date, quite a few efforts have been dedicated to solving the issues. − However, the application of a single strategy usually shows limited improvement and sometimes brings about new problems. For example, modified electrolytes generally provide a robust SEI and promote cycling stability for K anodes, but these only endure small current densities and cutoff capacities .…”

“…Taking advantage of the high-loading cathodes and anodeless or anode-free features, K||SPAN and MCNF||PB achieve high areal energy density of 4.87 and 5.72 W h cm –2 and gravimetric energy density of 256 and 362 W h kg –1 , respectively, standing out from previous works (Figure e, Table S6). ,,,,,, …”

“…Taking advantage of the high-loading cathodes and anodeless or anode-free features, K||SPAN and MCNF||PB achieve high areal energy density of 4.87 and 5.72 W h cm −2 and gravimetric energy density of 256 and 362 W h kg −1 , respectively, standing out from previous works (Figure 5e, Table S6). 10,11,13,33,34,55,56 In summary, to design anode-free K metal batteries, it is necessary to optimize both the electrolyte and host structures. Specifically, a TTE-assisted DHCE is introduced to provide an anion-participated solvation structure, improving the electrolyte's oxidation stability and triggering the formation of durable inorganic-rich SEI.…”