Dong Sui

Flexible and Transparent Electrothermal Film Heaters Based on Graphene Materials

High-performance and novel graphene-based electrothermal films are fabricated through a simple yet versatile solution process. Their electrothermal performances are studied in terms of applied voltage, heating rate, and input power density. The electrothermal films annealed at high temperature show high transmittance and display good heating performance. For example, the graphene-based film annealed at 800 °C, which shows transmittance of over 80% at 550 nm, can reach a saturated temperature of up to 42 °C when 60 V is applied for 2 min. Graphene-based films annealed at 900 and 1000 °C can exhibit high steady-state temperatures of 150 and 206 °C under an applied voltage of 60 V with a maximum heating rate of over 7 °C s(-1) . For flexible heating films patterned on polyimide, a steady-state temperature of 72 °C could be reached in less than 10 s with a maximum heating rate exceeding 16 °C s(-1) at 60 V. These excellent results, combined with the high chemical stability and mechanical flexibility of graphene, indicate that graphene-based electrothermal elements hold great promise for many practical applications, such as defrosting and antifogging devices.

Investigation of Gas Storage Properties of Graphene Material Prepared by Microwave-assisted Reduction of Graphene Oxide

Porous graphene material, named as MWRGO, has been prepared by microwave-assisted reduction method. Ex- tensive characterizations indicate that graphene oxide was effectively reduced and MWRGO has a porous and disordered stacking structure. It has a special surface area of 461.6 m 2 /g with pore size centered at 0.67 nm. H2 and CO2 adsorption properties of MWRGO were investigated, showing a H2 uptake of 0.52 wt% at 77 K and 1 atm and an absolute adsorption amount as high as 10.7 wt% at a higher pressure of 60 bar. The amount of CO2 adsorption at 273 K and 1 atm is 7.1 wt%. Keywords graphene; carbon materials; gas storage; microwave reduction; porous materials

Tailoring the oxygenated groups of graphene hydrogels for high-performance supercapacitors with large areal mass loadings

High-performance electrodes with high areal capacitances are highly desired for the practical applications of supercapacitors. Herein, we report such electrodes prepared from hydroxyl-rich graphene hydrogels (HRGHs). The hydroxyl groups on graphene sheets contribute to pseudo-capacitance and improve the wettability of HRGHs to aqueous electrolyte, ensuring fast ion transport within the electrodes, especially for the electrodes with high mass loadings. The supercapacitor based on mechanically compressed HRGHs shows a high gravimetric capacitance (260 F g−1) and volumetric capacitance (312 F cm−3) at 1 A g−1, good rate capability (∼78% at 100 A g−1), and excellent cycling stability (∼100% after 10 000 cycles). Moreover, an ultrahigh areal capacitance of 2675 mF cm−2 at 1 mA cm−2 is achieved at the mass loading of 10 mg cm−2. Even at a high current density of 50 or 100 mA cm−2, the areal capacitance is still retained at 2140 or 1768 mF cm−2, demonstrating the outstanding scalability of the HRGH electrodes.

A Hierarchical Silver‐Nanowire–Graphene Host Enabling Ultrahigh Rates and Superior Long‐Term Cycling of Lithium‐Metal Composite Anodes

Metallic lithium (Li) is a promising anode for next-generation high-energy-density batteries, but its applications are still hampered due to the limited charging/discharging rate and poor cycling performance. Here, a hierarchical 3D porous architecture is designed with a binary network of continuous silver nanowires assembled on an interconnected 3D graphene skeleton as the host for Li-metal composite anodes, which offers a significant boost in both charging/discharging rates and long-term cycling performance for Li-metal batteries. This unique hierarchical binary network structure in conjunction with optimized material combination provides ultrafast, continuous, and smooth electron transportation channel and non-nucleation barrier sites to direct and confine Li deposition. It also offers outstanding mechanical strength and toughness to support massive Li deposition and buffer the internal stress fluctuations during long-term repeated Li stripping/plating thereby minimizing fundamental issues of dendrite formation and volume change even under ultrafast charging/discharging rates. As a result, the composite anode using this hierarchical host can work smoothly at an unprecedented high current density of 40 mA cm-2 over 1000 plating/stripping cycles with low overpotential (<120 mV) in symmetric cells. The as-constructed full cell, paired with LiNi0.5 Co0.2 Mn0.3 O2 cathode, also exhibits excellent rate capability and high-rate cycling stability.