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- ItemStamping Fabrication of Flexible Planar Micro‐Supercapacitors Using Porous Graphene Inks(Hoboken : Wiley, 2020) Li, Fei; Qu, Jiang; Li, Yang; Wang, Jinhui; Zhu, Minshen; Liu, Lixiang; Ge, Jin; Duan, Shengkai; Li, Tianming; Bandari, Vineeth Kumar; Huang, Ming; Zhu, Feng; Schmidt, Oliver G.High performance, flexibility, safety, and robust integration for micro‐supercapacitors (MSCs) are of immense interest for the urgent demand for miniaturized, smart energy‐storage devices. However, repetitive photolithography processes in the fabrication of on‐chip electronic components including various photoresists, masks, and toxic etchants are often not well‐suited for industrial production. Here, a cost‐effective stamping strategy is developed for scalable and rapid preparation of graphene‐based planar MSCs. Combining stamps with desired shapes and highly conductive graphene inks, flexible MSCs with controlled structures are prepared on arbitrary substrates without any metal current collectors, additives, and polymer binders. The interdigitated MSC exhibits high areal capacitance up to 21.7 mF cm−2 at a current of 0.5 mA and a high power density of 6 mW cm−2 at an energy density of 5 µWh cm−2. Moreover, the MSCs show outstanding cycling performance and remarkable flexibility over 10 000 charge–discharge cycles and 300 bending cycles. In addition, the capacitance and output voltage of the MSCs are easily adjustable through interconnection with well‐defined arrangements. The efficient, rapid manufacturing of the graphene‐based interdigital MSCs with outstanding flexibility, shape diversity, and high areal capacitance shows great potential in wearable and portable electronics.
- ItemAntifreezing Hydrogel with High Zinc Reversibility for Flexible and Durable Aqueous Batteries by Cooperative Hydrated Cations(Weinheim : Wiley-VCH, 2020) Zhu, Minshen; Wang, Xiaojie; Tang, Hongmei; Wang, Jiawei; Hao, Qi; Liu, Lixiang; Li, Yang; Zhang, Kai; Schmidt, Oliver G.Hydrogels are widely used in flexible aqueous batteries due to their liquid-like ion transportation abilities and solid-like mechanical properties. Their potential applications in flexible and wearable electronics introduce a fundamental challenge: how to lower the freezing point of hydrogels to preserve these merits without sacrificing hydrogels' basic advantages in low cost and high safety. Moreover, zinc as an ideal anode in aqueous batteries suffers from low reversibility because of the formation of insulative byproducts, which is mainly caused by hydrogen evolution via extensive hydration of zinc ions. This, in principle, requires the suppression of hydration, which induces an undesirable increase in the freezing point of hydrogels. Here, it is demonstrated that cooperatively hydrated cations, zinc and lithium ions in hydrogels, are very effective in addressing the above challenges. This simple but unique hydrogel not only enables a 98% capacity retention upon cooling down to −20 °C from room temperature but also allows a near 100% capacity retention with >99.5% Coulombic efficiency over 500 cycles at −20 °C. In addition, the strengthened mechanical properties of the hydrogel under subzero temperatures result in excellent durability under various harsh deformations after the freezing process. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemApplications of nanogenerators for biomedical engineering and healthcare systems(Weinheim : Wiley, 2021) Wang, Wanli; Pang, Jinbo; Su, Jie; Li, Fujiang; Li, Qiang; Wang, Xiaoxiong; Wang, Jingang; Ibarlucea, Bergoi; Liu, Xiaoyan; Li, Yufen; Zhou, Weijia; Wang, Kai; Han, Qingfang; Liu, Lei; Zang, Ruohan; Rümmeli, Mark H.; Li, Yang; Liu, Hong; Hu, Han; Cuniberti, GianaurelioThe dream of human beings for long living has stimulated the rapid development of biomedical and healthcare equipment. However, conventional biomedical and healthcare devices have shortcomings such as short service life, large equipment size, and high potential safety hazards. Indeed, the power supply for conventional implantable device remains predominantly batteries. The emerging nanogenerators, which harvest micro/nanomechanical energy and thermal energy from human beings and convert into electrical energy, provide an ideal solution for self‐powering of biomedical devices. The combination of nanogenerators and biomedicine has been accelerating the development of self‐powered biomedical equipment. This article first introduces the operating principle of nanogenerators and then reviews the progress of nanogenerators in biomedical applications, including power supply, smart sensing, and effective treatment. Besides, the microbial disinfection and biodegradation performances of nanogenerators have been updated. Next, the protection devices have been discussed such as face mask with air filtering function together with real‐time monitoring of human health from the respiration and heat emission. Besides, the nanogenerator devices have been categorized by the types of mechanical energy from human beings, such as the body movement, tissue and organ activities, energy from chemical reactions, and gravitational potential energy. Eventually, the challenges and future opportunities in the applications of nanogenerators are delivered in the conclusive remarks. The combination of nanogenerator and biomedicine have been accelerating the development of self‐powered biomedical devices, which show a bright future in biomedicine and healthcare such as smart sensing, and therapy.
- ItemStress‐Actuated Spiral Microelectrode for High‐Performance Lithium‐Ion Microbatteries(2020) Tang, Hongmei; Karnaushenko, Dmitriy D.; Neu, Volker; Gabler, Felix; Wang, Sitao; Liu, Lixiang; Li, Yang; Wang, Jiawei; Zhu, Minshen; Schmidt, Oliver G.Miniaturization of batteries lags behind the success of modern electronic devices. Neither the device volume nor the energy density of microbatteries meets the requirement of microscale electronic devices. The main limitation for pushing the energy density of microbatteries arises from the low mass loading of active materials. However, merely pushing the mass loading through increased electrode thickness is accompanied by the long charge transfer pathway and inferior mechanical properties for long‐term operation. Here, a new spiral microelectrode upon stress‐actuation accomplishes high mass loading but short charge transfer pathways. At a small footprint area of around 1 mm2, a 21‐fold increase of the mass loading is achieved while featuring fast charge transfer at the nanoscale. The spiral microelectrode delivers a maximum area capacity of 1053 µAh cm−2 with a retention of 67% over 50 cycles. Moreover, the energy density of the cylinder microbattery using the spiral microelectrode as the anode reaches 12.6 mWh cm−3 at an ultrasmall volume of 3 mm3. In terms of the device volume and energy density, the cylinder microbattery outperforms most of the current microbattery technologies, and hence provides a new strategy to develop high‐performance microbatteries that can be integrated with miniaturized electronic devices.