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Nano/Micro-Structured Silicon-Graphite Composite Anode for High-Energy Density Li-Ion Battery Peng Li, Jang-Yeon Hwang, and Yang-Kook Sun ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.9b00169 • Publication Date (Web): 13 Feb 2019 Downloaded from http://pubs.acs.org on February 14, 2019
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ACS Nano
Nano/Micro-Structured Silicon-Graphite Composite Anode for High-Energy Density Li-Ion Battery Peng Lia, Jang-Yeon Hwanga and Yang-Kook Suna* a Department
of Energy Engineering, Hanyang University, Seoul 133-791, Republic of Korea
* Corresponding author. E-mail:
[email protected] ABSTRACT: With the ever-increasing demand for lithium ion batteries (LIBs) with higher energy density, tremendous attention has been paid to design various silicon active materials as alternative electrodes due to its high theoretical capacity (ca. 3579 mAh g-1). However, replacing the commercially utilized graphite totally with silicon is still insurmountable owing to bottlenecks such as low electrode loading and insufficient areal capacity. Thus, in this study, we turn eyes back on enhanced graphite electrode through the cooperation of modified silicon via a facile and scalable blending process. The modified nano/micro-structured silicon with boron doping and carbon nanotube wedging (B-Si/CNT) can provide improved stability (88.2% retention after 200 cycles at 2000 mA g-1) and high reversible capacity (approximately 2426 mAh g-1), while the graphite can act as a tough framework for high loading. Owing to the synergistic effect, the resultant B-Si/CNTgraphite composite (B-Si/CNT@G) shows an high areal capacity of 5.2 mAh cm-2 and excellent cycle retention of 83.4 % over 100 cycles even with ultra-high active mass loading of 11.2 mg cm2,which
could significantly surpass the commercially used graphite electrode. Notably, the
composite also exhibits impressive application in Li-ion full battery using 2 mol% Al-doped full concentration gradient Li[Ni0.76Co0.09Mn0.15]O2 (Al2-FCG76) as cathode with excellent capacity retention of 82.5% even after 300 cycles and an outstanding energy density (8.0 mWh cm-2) based 1 ACS Paragon Plus Environment
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on the large mass loading of cathode (12.0 mg cm-2).
KEYWORDS: silicon, graphite, electrode loading, areal capacity, lithium ion battery
To address global climate change issues, electric vehicles, hybrid electric vehicles, and energy storage systems equipped with lithium-ion batteries (LIBs) are intensively used nowadays.1 Graphite has been used as the most common active material for negative electrodes in commercially available LIBs because of its low potential, abundant reserves, and good stability.2 However, its limited theoretical capacity (372 mAh g−1) still falls short of the energy density and capability required to meet ever-growing demands and cannot surpass the excellent mileage of internal combustion vehicles (approximately 400 miles).3,4 Thus, the development of advanced anodes with high Li+ storage capacity at low working voltage has long been pursued to overcome this limitation and realize high energy and power density. To date, various active materials with higher theoretical capacities have been proposed to replace graphite, e.g., silicon, tin, and germanium.3 Owing to its high theoretical gravimetric capacity (ca. 4200 mAh g-1 at 415 °C in the form of Li22Si5; 3579 mAh g-1 at room temperature in the form of Li15Si4), relatively low redox voltage (
