A combination of hierarchical pore and buffering layer construction for ultrastable nanocluster Si/SiO x anode
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en Key Laboratory of Power Battery Safety Research and Shenzhen Geim Graphene Center, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China 2 Tsinghua-Berkeley Shenzhen Institute (TBSI), Tsinghua University, Shenzhen 518055, China 3 School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China § Kun Zeng and Tong Li contributed equally to this work. © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 8 May 2020 / Revised: 28 June 2020 / Accepted: 29 June 2020
ABSTRACT Porous Si can be synthesized from diverse silica (SiO2) via magnesiothermic reduction technology and widely employed as potential anode material in lithium ion batteries. However, concerns regarding the influence of residual silicon oxide (SiOx) component on resulted Si anode after reduction are still lacked. In this work, we intentionally fabricate a cauliflower-like silicon/silicon oxide (CF-Si/SiOx) particles from highly porous SiO2 spheres through insufficient magnesiothermic reduction, where residual SiOx component and internal space play an important role in preventing the structural deformation of secondary bulk and restraining the expansion of Si phase. Moreover, the hierarchically structured CF-Si/SiOx exhibits uniformly-dispersed channels, which can improve ion transport and accommodate large volume expansion, simultaneously. As a result, the CF-Si/SiOx-700 anode shows excellent electrochemical performance with a specific capacity of ~1,400 mA·h·g−1 and a capacity retention of 98% after 100 cycles at the current of 0.2 A·g−1.
KEYWORDS highly-porous, Si/SiOx anodes, magnesiothermic reduction, lithium ion battery
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Introduction
At present, lithium-ion batteries (LIBs) have become a necessarily integral part of electronic equipment, electric vehicles, and largescale energy storage systems [1, 2]. However, the limited capacity of commercial graphite anode in LIBs (372 mA·h·g−1) fails to meet the ever-increasing demands of high energy density for energy storage devices. Si, a promising anode material, has many advantages over other candidates, such as the highest specific capacity of 3,579 mA·h·g−1 (corresponding to the formation of Li15Si4) at room temperature [3] and low discharge potential ~ 0.37 V (vs. Li/Li+). Unfortunately, the large volume change (> 300%) during lithiation/delithiation process and relatively poor electronic conductivity limit its further application and potential commercialization [3–6]. Worse still, the large volume change inevitably results in electrode pulverization and unstable solid electrolyte interface (SEI) issues, leading to rapid capacity decay, large lithium consumption, and low coulombic efficiency [3–8]. Intensive efforts have been made to solve the issues caused by huge volume change recently, such as minimizing the particle size, building porous structure, and coupling with carbonaceous materials, etc. [9–13] In common, nano-sized Si has been employed to alleviate the strain in charge/discharg
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