An Ultralight Composite Current Collector Enabling High-Energy-Density and High-Rate Anode-Free Lithium Metal Battery.

Anode-free lithium (Li) metal batteries are promising alternatives to current Li-ion batteries due to their advantages such as high energy density, low cost, and convenient production. However, the copper (Cu) current collector accounts for more than 25 wt% of the total weight of the anode-free battery without capacity contribution, which severely reduces the energy and power densities. Here, a new family of ultralight composite current collectors with a low areal density of 0.78 mg cm-2, representing significant weight reduction of 49%-91% compared with the Cu-based current collectors for high-energy Li batteries, is presented. Rational molecular engineering of the polyacylsemicarbazide substrate enables enhanced interfacial interaction with the sputtered Cu layer, which results in excellent interfacial stability, flexibility, and safety for the obtained anode-free batteries. The battery-level energy density has been significantly improved by 36%-61%, and a maximum rate capability reaches 5 C (10 mA cm-2) attributed to the homogeneous Li+ flux and smooth Li deposition on the nanostructured Cu layer. The results not only open a new avenue to improve the energy and power densities of anode-free batteries via composite current collector innovation but, in a broader context, provide a new paradigm to pursue high-performance, high-safety, and flexible batteries.

Carbon Nanotube Fiber-Based Flexible Microelectrode for Electrochemical Glucose Sensors.

Electrochemical sensors are gaining significant demand for real-time monitoring of health-related parameters such as temperature, heart rate, and blood glucose level. A fiber-like microelectrode composed of copper oxide-modified carbon nanotubes (CuO@CNTFs) has been developed as a flexible and wearable glucose sensor with remarkable catalytic activity. The unidimensional structure of CNT fibers displayed efficient conductivity with enhanced mechanical strength, which makes these fibers far superior as compared to other fibrous-like materials. Copper oxide (CuO) nanoparticles were deposited over the surface of CNT fibers by a binder-free facile electrodeposition approach followed by thermal treatment that enhanced the performance of non-enzymatic glucose sensors. Scanning electron microscopy and energy-dispersive X-ray analysis confirmed the successful deposition of CuO nanoparticles over the fiber surface. Amperometric and voltammetric studies of fiber-based microelectrodes (CuO@CNTFs) toward glucose sensing showed an excellent sensitivity of ∼3000 µA/mM cm2, a low detection limit of 1.4 µM, and a wide linear range of up to 13 mM. The superior performance of the microelectrode is attributed to the synergistic effect of the electrocatalytic activity of CuO nanoparticles and the excellent conductivity of CNT fibers. A lower charge transfer resistance value obtained via electrochemical impedance spectroscopy (EIS) also demonstrated the superior electrode performance. This work demonstrates a facile approach for developing CNT fiber-based microelectrodes as a promising solution for flexible and disposable non-enzymatic glucose sensors.

Cobalt Ferrite Surface-Modified Carbon Nanotube Fibers as an Efficient and Flexible Electrode for Overall Electrochemical Water Splitting Reactions.

One of the most practical and environmentally friendly ways to deal with the energy crises and global warming is to produce hydrogen as clean fuel by splitting water. The central obstacle for electrochemical water splitting is the use of expensive metal-based catalysts. For electrocatalytic hydrogen production, it is essential to fabricate an efficient catalyst for the counterpart oxygen evolution reaction (OER), which is a four-electron-transfer sluggish process. Here in this study, we have successfully fabricated cobalt-based ferrite nanoparticles over the surface of carbon nanotube fiber (CNTF) that was utilized as flexible anode materials for the OER and overall electrochemical water splitting reactions. Scanning electron microscopy images with elemental mapping showed the growth of nanoparticles over CNTF, while electrochemical characterization exhibited excellent electrocatalytic performance. Linear sweep voltammetry revealed the reduced overpotential value (260 mV@η10mAcm-2) with a small Tafel slope of 149 mV dec-1. Boosted electrochemical double layer capacitance (0.87 mF cm-2) for the modified electrode also reflects the higher surface area as compared to pristine CNTF (Cdl = 0.022 mF cm-2). Charge transfer resistance for the surface-modified CNTF showed the lower diameter in the Nyquist plot and was consequently associated with the better Faradaic process at the electrode/electrolyte interface. Overall, the as-fabricated electrode could be a promising alternative for the efficient electrochemical water splitting reaction as compared to expensive metal-based electrocatalysts.