3 ) and better plating/stripping reversibility than Mg, Ca, and Al. [3] In addition, as an earth-abundant metal, the price of Zn is only ≈4% of Li. [4] Therefore, aqueous zinc-ion batteries (AZIBs) have ushered in an unprecedented development in the past few years. Considerable efforts have been made to further improve the reversibility of Zn plating/stripping. [5,6] At the same time, it should be noted that the dendrite growth caused by uneven Zn plating can not only reduce the reversibility, but also directly cause a short circuit after penetrating the separator, seriously limiting the life span of AZIBs. [7,8] Regulating Zn plating behavior at electrolyte-anode interface to realize smooth Zn deposition is necessary to stabilize Zn anode. [9,10] One of the main methods is electrolyte regulation, [11] including designing unique electrolyte systems, [12][13][14] using electrolyte additives, [15,16] developing gel electrolytes, [17] etc. Another key strategy is Zn anode surface modification, namely constructing artificial interface layer on Zn foil. Recently, various materials including organics (polyamide, [18] polyacrylonitrile, [19] poly(vinyl butyral), [20] etc.) and inorganics (TiO 2 , [21] CaCO 3 , [22] ZrO 2 , [23] Al 2 O 3 , [24] etc.) have been constructed as protective interface layers by doctor blading, spin coating, or atomic layer deposition (ALD) methods. However, they face some practical limitations, including difficulty in controlling consistency of layer composition/structure and thickness, or inability to accommodate easy mass production. For example, additional binders are required for doctor-blading Uneven distribution of electric fields at the electrolyte-anode interface and associated Zn dendrite growth is one of the most critical barriers that limit the life span of aqueous zinc-ion batteries. Herein, new-type Zn-A-O (A = Si, Ti) interface layers with thin and uniform thickness, porosity, and hydrophilicity properties are developed to realize homogeneous and smooth Zn plating. For ZnSiO 3 nanosheet arrays on Zn foil (Zn@ZSO), their formation follows an "etching-nucleation-growth" mechanism that is confirmed by a well-designed Zn-island-based identical-location microscopy method, the geometric area of which is up to 1000 cm 2 in one-pot synthesis based on a lowtemperature wet-chemical method. Guided by the structural advantages of the ZSO layer, the Zn 2+ flux gets equalized. Besides ultralow polarization, the life spans of symmetric cells and full cells coupled with a high-mass-loading K 0.27 MnO 2 •0.54H 2 O (8 mg cm −2 ) cathode, are increased by 3-7 times with the Zn@ZSO anode. Moreover, the large-scale preparation of Zn@ZSO foil contributes to a 0.5 Ah multilayer pouch cell with high performance, further confirming its prospects for practical application.
The corrosion, parasitic reactions, and aggravated dendrite growth severely restrict development of aqueous Zn metal batteries. Here, we report a novel strategy to break the hydrogen bond network between water molecules and construct the Zn(TFSI) 2 -sulfolane-H 2 O deep eutectic solvents. This strategy cuts off the transfer of protons/hydroxides and inhibits the activity of H 2 O, as reflected in a much lower freezing point (< À 80 °C), a significantly larger electrochemical stable window (> 3 V), and suppressed evaporative water from electrolytes. Stable Zn plating/stripping for over 9600 h was obtained. Based on experimental characterizations and theoretical simulations, it has been proved that sulfolane can effectively regulate solvation shell and simultaneously build the multifunctional Zn-electrolyte interface. Moreover, the multi-layer homemade modular cell and 1.32 Ah pouch cell further confirm its prospect for practical application.
diffusion courses and would cause significant volume changes of electrode material. [3] Therefore, the design of reliable electrode materials is the major challenge for applications of KIBs, especially anode materials with stable structure, fast kinetics, and excellent electrochemical performance. [4] Recently, substantial efforts have been paid to explore innovative anode materials for KIBs, include alloying type, [5] conversion/alloying type, [6] and carbonaceous materials. [7] Among them, red phosphorus (RP) displays a high theoretical capacity, suitable operating potential, and excellent chemical stability. [8] Unfortunately, the RP anode exhibits poor rate capabilities and electrochemical reversibility because of its extremely large volume expansion during potassiation/depotassiation. [9] Moreover, the poor electrical conductivity (≈10 −14 S cm −1 ) leads to large polarization and sluggish reaction kinetics. [10] Meanwhile, the existence of abundant polymorphs of potassium phosphides (e.g., KP, K 4 P 3 , K 3 P 11 , K 3 P) presents great challenges to determine the exact discharge products, and the mechanism of potassium storage of RP is controversial. [11] To address above issues, the introduction of RP into conductive carbon network is a general approach to accommodate volume effect and facilitate ion diffusion and charge transfer. [12] However, in most of cases, the conductive carbon is subjected to huge stress and strain, which leads to the fatigue of electrode structure and the exposure of active materials. To buffer the stress and strain caused by large volume expansion materials, Red phosphorus (RP), as a promising anode for potassium-ion batteries (KIBs), and has attracted extensive attention due to its high theoretical capacity, low redox potential, and abundant natural sources. However, RP shows dramatic capacity decay and rapid structure degradation caused by huge volume expansion and poor electronic conductivity. Here, a volume strain-relaxation electrode structure is reported, by encapsulating well-confined amorphous RP in 3D interconnected sulfur, nitrogen co-doped carbon nanofibers (denoted as RP@S-N-CNFs). In situ transmission electron microscopy and the corresponding chemo-mechanical simulation reveal the excellent structural integrity and robustness of the N, S carbon matrix. As a freestanding anode for KIBs, the RP@S-N-CNFs electrode exhibits high reversible capacities (566.7 mAh g −1 after 100 cycles at 0.1 A g −1 ) and extraordinary durability (282 mAh g −1 after 2000 cycles at 2 A g −1 ). The highly reversible one-electron transfer mechanism with a final discharge product of KP and faster kinetics are demonstrated through in situ characterizations and density functional theory calculations. This work sheds light on the rational design of large-volumevibration type anodes for next-generation high-performance KIBs.
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