This content will become publicly available on August 1, 2023
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- Nature Electronics
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- National Science Foundation
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Lenders, Jos (Ed.)A major challenge for graphene applications is the lack of mass production technology for large-scale and high-quality graphene growth and transfer. Here, a roll-to-roll (R2R) dry transfer process for large-scale graphene grown by chemical vapor deposition is reported. The process is fast, controllable, and environmentally benign. It avoids chemical contamination and allows the reuse of graphene growth substrates. By controlling tension and speed of the R2R dry transfer process, the electrical sheet resistance is achieved as 9.5 kΩ sq−1, the lowest ever reported among R2R dry transferred graphene samples. The R2R dry transferred samples are used to fabricate graphene-based field-effect transistors (GFETs) on polymer. It is demonstrated that these flexible GFETs feature a near-zero doping level and a gate leakage current one to two orders of magnitude lower than those fabricated using wet-chemical etched graphene samples. The scalability and uniformity of the R2R dry transferred graphene is further demonstrated by successfully transferring a 3 × 3 in2 sample and measuring its field-effect mobility with 36 millimeter-scaled GFETs evenly spaced on the sample. The field-effect mobility of the R2R dry transferred graphene is determined to be 205 ± 36 cm2 V−1.
Design principles of pseudocapacitive carbon anode materials for ultrafast sodium and potassium-ion batteriesSodium- and potassium-ion batteries are one of the most promising electrical energy storage devices at low cost, but their inferior rate and capacity have hampered broader applications such as electric vehicles and grids. Carbon nanomaterials have been demonstrated to have ultrafast surface-dominated ion uptake to drastically increase the rate and capacity, but trial-and-error approaches are usually used to find desired anode materials from numerous candidates. Here, we developed guiding principles to rationally screen pseudocapacitive anodes from numerous candidate carbon materials to create ultrafast Na- and K-ion batteries. The transition from pseudocapacitive to metal-battery mechanisms on heteroatom-doped graphene in charging process was revealed by the density functional theory methods. The results show that the graphene substrate can guide the preferential growth of K and Na along graphene plane, which inhibits dendrite development effectively in the batteries. An intrinsic descriptor is discovered to establish a volcano-shaped relationship that correlates the capacity with the intrinsic physical qualities of the doping structures, from which the best anode materials could be predicted. The predictions are in good agreement with the experimental results. The strategies for enhancing both the power and energy densities are proposed based on the predictions and experiments for the batteries.
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