High‐Performance Li–Se Battery Enabled via a One‐Piece Cathode Design

Abstract

conductivity, and high volumetric energy density. [8][9][10] Moreover, Se is a reasonably priced element, being around $ 32 per kg when purchased in industrial quantities. [4] Comparable to the S cathode, a Se cathode also has major concerns regarding volume expansion of Se (>97%) and shuttle effects by polyselenide intermediates. [11,12] To address these concerns, most studies have focused on the incorporation of functional materials such as porous carbons, conductive polymers, and metal oxides. [5][6][7] In general, the Se cathode is prepared by complicated multistep processes, which are consisted of encapsulating of Se into porous carbon (Se/C composite), slurry preparation using high energy ball-mixing of Se/C composites and other additives, deposition of the slurry on a current collector, and finally pressing the cathode. [11][12][13] In the Se cathode, there exist complex interfaces due to multicomponents system. Furthermore, all the additives do not contribute to electrochemical redox reaction lowering energy density and polymer binder even can increase interfacial resistance. Thus, it would be highly desirable to provide a simple fabrication process and stable cycling to Li-Se battery. [14][15][16] Herein, we introduced a new design of Se cathode, which was simply prepared by electrochemical deposition of Se on Nifoam and subsequent coating of a thin layer of solid polymer electrolyte (SPE). The electrodeposition of Se on Ni-foam is an easy process, and direct contacts of Se on current collector provide facile charge transport. The SPE was easily prepared via crosslinking reaction of poly(ethylene glycol) diglycidyl ether (DE-PEG) and diamino-poly(propylene oxide) (DA-PPG) with subsequent immersion in a LiPF 6 based carbonate electrolyte. The elastic SPE layer is able to protect the delamination problem of Se from the Ni-foam controlling the volume expansion of Se, to provide facile ionic pathway, and to suppress Li-dendrite growth. The designed "One-piece" Se cathode was produced by facile manufacturing process and exhibited an ultrastable cycling performance of 0.001% capacity degradation per cycle for 3000 cycles at 1 C rate.A schematic preparation of the one-piece Se cathode is shown in Figure 1. In the preparation of the one-piece Se cathode, Se was electrodeposited on the Ni-foam and a prepolymer solution of SPE was poured on the Se/Ni-foam to fill the pore. The prepolymer was thermally cross-linked and liquid electrolyte was impregnated. At the bottom of Ni-foam, a thin layer (≈20 µm) of SPE was formed which was directly contacted with Li metal foil. Moreover, the thickness of SPE in A high-performance Li-Se battery is demonstrated by adopting a novel Se cathode design. The Se cathode is a one-piece body combined with a Se deposited current collector and a solid polymer electrolyte (SPE). In the preparation of the Se cathode, Se is electrodeposited on Ni-foam, and the pores are filled with SPE layers. Through this electrodeposition, the cathode is easily fabricated, and charge transports are facile...

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“…S13). For commercial applications, the loading density of sulfur and the C-rate are important factors [4,30]. Furthermore, an increased sulfur loading is important for the commercial application of LSBs.…”

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