High Electrochemical Performance Silicon Thin-Film Free-Standing Electrodes Based on Buckypaper for Flexible Lithium-Ion Batteries

Abstract

Recently, applications for lithium-ion batteries (LIBs) have expanded to include electric vehicles and electric energy storage systems, extending beyond power sources for portable electronic devices. The power sources of these flexible electronic devices require the creation of thin, light, and flexible power supply devices such as flexile electrolytes/insulators, electrode materials, current collectors, and batteries that play an important role in packaging. Demand will require the progress of modern electrode materials with high capacity, rate capability, cycle stability, electrical conductivity, and mechanical flexibility for the time to come. The integration of high electrical conductivity and flexible buckypaper (oxidized Multi-walled carbon nanotubes (MWCNTs) film) and high theoretical capacity silicon materials are effective for obtaining superior high-energy-density and flexible electrode materials. Therefore, this study focuses on improving the high-capacity, capability-cycling stability of the thin-film Si buckypaper free-standing electrodes for lightweight and flexible energy-supply devices. First, buckypaper (oxidized MWCNTs) was prepared by assembling a free stand-alone electrode, and electrical conductivity tests confirmed that the buckypaper has sufficient electrical conductivity (10−4(S m−1) in LIBs) to operate simultaneously with a current collector. Subsequently, silicon was deposited on the buckypaper via magnetron sputtering. Next, the thin-film Si buckypaper freestanding electrodes were heat-treated at 600 °C in a vacuum, which improved their electrochemical performance significantly. Electrochemical results demonstrated that the electrode capacity can be increased by 27/26 and 95/93 μAh in unheated and heated buckypaper current collectors, respectively. The measured discharge/charge capacities of the USi_HBP electrode were 108/106 μAh after 100 cycles, corresponding to a Coulombic efficiency of 98.1%, whereas the HSi_HBP electrode indicated a discharge/charge capacity of 193/192 μAh at the 100th cycle, corresponding to a capacity retention of 99.5%. In particular, the HSi_HBP electrode can decrease the capacity by less than 1.5% compared with the value of the first cycle after 100 cycles, demonstrating excellent electrochemical stability.

Preparation and characterization of a flexible lithium ion electrode based on carbonized cotton fabric

“…The semicircle in the high frequency region represents the surface resistance of lithium ions passing through the interface, and the oblique line in the low frequency region represents the diffusion resistance of lithium ions. 29,30 It can be seen from the Figure 9 that as the carbonization temperature increased, the AC impedance of the flexible electrode decreased. When the carbonization temperature rised to 1000°C, the AC impedance of the flexible electrode reduced to 5 V. This is because with the increase of carbonization temperature, the better the carbonization effect of cotton fabric and the higher the conductivity.…”

Enhanced LiMn2O4 cathode performance in lithium-ion batteries through synergistic cation and anion substitution

“…For all three cathodes, the capacity decreases momentarily at high current densities with an increase in the proportion of the side reaction as a direct consequence of the Bulter-Volmer equation, resulting in a nonreversible reaction. 58,59 After the high rate (5C), the capacity recovery at the fundamental cycle rate of 0.2C indicates that the crystal structure is preserved. Further, the discharge capacities after 10 cycles at each C rate are 128, 119, 113, 105, 93, and 126 mA h g À1 for LMTO and 140, 138, 133, 125, 115, and 142 mA h g À1 for LMTOS, which are the highest.…”

Electrochemical Performance of Polymer-Derived Silicon-Oxycarbide/Graphene Nanoplatelet Composites for High-Performance Li-Ion Batteries

“…Flexible batteries have received enormous attention recently, especially in healthcare and wearable electronics. 49 Our group previously reported 50 that due to the porous nature of buckypaper, Si nanoparticles adhere well to the buckypaper current collector upon coating.…”

“…Furthermore, with buckypaper electrodes, flexible LIBs showed no signs of cracking, delamination, or structural changes typically observed in rigid LIBs. Flexible batteries have received enormous attention recently, especially in healthcare and wearable electronics . Our group previously reported that due to the porous nature of buckypaper, Si nanoparticles adhere well to the buckypaper current collector upon coating.…”