From 0D to 3D: Dimensional Control of Bismuth for Potassium Storage with Superb Kinetics and Cycling Stability

Abstract

energy storage systems. [7][8][9] Thus, it is highly desired to develop new energy storage systems based on more abundant elements (such as sodium and potassium). [10,11] Compared with LIBs and sodium-ion batteries (NIBs), potassiumion batteries (KIBs) are one of the most ideal alternatives due to abundant potassium resources, lower redox potential of K + /K than that of Na + /Na (−2.93 V vs −2.71 V), similar "rocking-chair" reaction mechanism, and smaller Stokes radius in common electrolyte (K + (3.6 Å) < Na + (4.6 Å) < Li + (4.8 Å)). [12,13] Therefore, KIBs have lower production cost which has been considered as potential candidates for large-scale energy storage systems. [14] The biggest challenge for the development of KIBs is to find suitable electrode materials, because the repeated insertion/extraction of large K-ion radius would result in sluggish diffusion kinetics and electrode destruction. [15,16] Until now, many efforts have been devoted to pursue suitable electrode materials for highperformance K-ion storage. Among all kinds of anode materials, alloy-type anodes have been distinguished as promising candidates owing to its suitable voltage platform, high theoretical capacity, and high energy density. [17,18] Bismuth (Bi), an environment-friendly alloy anode material, has demonstrated a bright prospect in KIBs. [19][20][21] Based on the complete alloying reaction (Bi → K 3 Bi), it can deliver a high theoretical capacity of 385 mA h g −1 and a low reaction voltage of 0.34 V. However, huge volumetric change (506% for forming K 3 Bi) during charging/discharging and the derived electrode pulverization lead to poor cyclability and short cycle-life. [22] To address these issues, enormous efforts have been made to optimize the electrochemical properties of Bi-based anodes via appropriate structure design, such as hybridizing with carbonaceous matrix, [23] alloying with other metal, [24] and designing ultra-small nanoparticles. [25] Generally, the dimensionality of the reported Bi-based materials can be categorized into 0D, 1D, 2D, and 3D morphologies. [26] Different-dimensional structures show their unique performances based on surface and structural characteristics. Compared to 3D microsized materials, 0D-structured nanoparticles possess short diffusion length in all directions and large electrolyte-electrode contact area. Lu's group reported 0D Bi nanoparticles embedded in carbon matrix, delivering high capacity and steady long cycle (121 mA h g −1 after 700 cycles at 1 A g −1 ). [27] The 1D nanostructure exhibits Bismuth-based anode for potassium ion batteries (KIBs) has gained great attention due to its high volumetric specific capacity (3800 mA h mL −1 ). However, the Bi-based materials face a huge volumetric change upon the cycling process. Herein, the dimensionality manipulation in the Bi-anode is focused to realize superior electrochemical performance. The morphological evolution rules of 0D, 1D, 2D, and 3D Bi anodes upon the potassiation/depotassiation process are clarified. Thereinto, the 2D-Bi tran...

High-efficiency cathode potassium compensation and interfacial stability improvement enabled by dipotassium squarate for potassium-ion batteries

“…5d). 9,11,31,46–51 Unlike the serious loss of output energy in the KMO||SC full cell, the KCO@KMO||SC full cell still maintains a high energy density of 158 W h kg −1 after 100 cycles (Fig. S23, ESI†).…”

Boosting Interfacial Ion Transfer in Potassium-Ion Batteries via Synergy Between Nanostructured Bi@NC Bulk Anode and Electrolyte

“…35 Appropriate content of KF with high modulus can make SEI tolerate the volume fluctuation, whereas its excess would increase the interfacial resistance. 24 This should be responsible for slow reaction kinetics but moderate cycling life in the KFSI-EC/DEC electrolyte. Moreover, the peak intensities of KF and K 2 CO 3 (288.5 eV in C 1s spectra) increase remarkably after etching, manifesting that inorganic components are prioritized to deposit in the interior of both SEIs.…”

“…55 As depicted in C 1s spectra, the peaks at 286.6, 286.3, 288.2, and 289.3 eV are associated with polyester, polyether, C�O, and C−F, respectively. 13,24,56 The polyether composition possessed high ion conductivity and superior mechanical elasticity, guaranteeing fast K + transport and stabilizing Bi anode's interphase. 24,56,57 As demonstrated by the evolution of peaks intensities with etching time, the organic layer is mainly concentrated in the outer region of both SEIs, and KPF 6 -DME electrolyte is preferred to induce much thinner SEI film than KFSI-EC/DEC one.…”

“…13,24,56 The polyether composition possessed high ion conductivity and superior mechanical elasticity, guaranteeing fast K + transport and stabilizing Bi anode's interphase. 24,56,57 As demonstrated by the evolution of peaks intensities with etching time, the organic layer is mainly concentrated in the outer region of both SEIs, and KPF 6 -DME electrolyte is preferred to induce much thinner SEI film than KFSI-EC/DEC one. Notably, the most striking discrepancy is observed in Bi spectra.…”

“…Similarly, other anode materials (e.g., transition-metal sulfide, alloy-type, and carbonaceous anodes) could also benefit from the robust SEI feature using KFSI-based electrolytes . Exceptionally, a few recent studies have demonstrated that KPF 6 /ether electrolytes could exclusively endow Bi-based anode materials with excellent potassium-storage performances. ,− Nevertheless, the underlying interfacial mechanism and interplay between electrolytes and Bi electrodes seem elusive, and contradictory results exist in the literature. For example, Chen’s group has ascribed the enhanced performance to the transition from bulky Bi to porous one during cycling in ether electrolytes .…”