Xunliang Cheng

Flexible and Stretchable Lithium‐Ion Batteries and Supercapacitors Based on Electrically Conducting Carbon Nanotube Fiber Springs

The construction of lightweight, flexible and stretchable power systems for modern electronic devices without using elastic polymer substrates is critical but remains challenging. We have developed a new and general strategy to produce both freestanding, stretchable, and flexible supercapacitors and lithium-ion batteries with remarkable electrochemical properties by designing novel carbon nanotube fiber springs as electrodes. These springlike electrodes can be stretched by over 300 %. In addition, the supercapacitors and lithium-ion batteries have a flexible fiber shape that enables promising applications in electronic textiles.

Aligned carbon nanotube/molybdenum disulfide hybrids for effective fibrous supercapacitors and lithium ion batteries

An aligned carbon nanotube/MoS2 nanosheet hybrid fiber was synthesized to display combined remarkable mechanical, electronic and electrochemical properties. It was used to fabricate flexible fibrous supercapacitors and lithium ion batteries with a high specific capacitance of 135 F cm−3 and a high specific capacity of 1298 mA h g−1, respectively.

Realizing both High Energy and High Power Densities by Twisting Three Carbon‐Nanotube‐Based Hybrid Fibers

Energy storage devices, such as lithium-ion batteries and supercapacitors, are required for the modern electronics. However, the intrinsic characteristics of low power densities in batteries and low energy densities in supercapacitors have limited their applications. How to simultaneously realize high energy and power densities in one device remains a challenge. Herein a fiber-shaped hybrid energy-storage device (FESD) formed by twisting three carbon nanotube hybrid fibers demonstrates both high energy and power densities. For the FESD, the energy density (50 mWh cm(-3) or 90 Wh kg(-1) ) many times higher than for other forms of supercapacitors and approximately 3 times that of thin-film batteries; the power density (1 W cm(-3) or 5970 W kg(-1) ) is approximately 140 times of thin-film lithium-ion battery. The FESD is flexible, weaveable and wearable, which offers promising advantages in the modern electronics.

An all-solid-state fiber-type solar cell achieving 9.49% efficiency

Flexible and wearable solar cells represent a promising direction in the advancement of next-generation energy-harvesting electronics. However, the solar cells in a planar structure cannot meet the requirements of complicated deformations. On the other hand, solar cells based on the one-dimensional structure attract increasing interest as they can stably work under both bending and twisting. Here, a family of fiber-type perovskite solar cells has been designed with impressive photovoltaic performance. They exhibit a high power conversion efficiency of 9.49% that is stable under both bending and twisting. A combination of large crystals of perovskite and aligned carbon nanotube sheets contributes to their excellent properties. Due to their unique fiber shape, they can be further woven into flexible and lightweight power textiles that are promising as the next-generation portable and wearable electronics.

Elastic and wearable ring-type supercapacitors

The development of flexible energy storage devices is critical while it remains challenging for wearable electronics. Herein, a new family of elastic and wearable ring-type supercapacitors is fabricated by winding aligned carbon nanotube/poly(3,4-ethyl-enedioxythiophene):poly(styrene sulfonate) composite sheets onto an elastic polymer ring. The supercapacitor delivers a high specific capacitance of 134.8 F g−1 at a current density of 1 A g−1. Importantly, the specific capacitance has been well maintained after expanding and pressing, which endows the supercapacitor with unique advantages, e.g., it can be used for substrates with different sizes and shapes and may satisfy a variety of wearable applications as well as other fields.

A smart, stretchable resistive heater textile

A new kind of flexible and stretchable strip-shaped thermochromic resistive heater (TRH) has been fabricated by incorporating an aligned carbon nanotube sheet and a thermochromic silicone elastomer. This strip-shaped TRH demonstrates rapid thermal response and high stability even under stretching at a speed of 2 mm s−1. The resulting TRH textiles woven from the strip-shaped TRHs are flexible, stretchable, and breathable, and they can stably work under various deformations such as twisting. The temperatures of TRH textiles during working can be visually evaluated from the designed patterns for both high efficiency and safety. The weaving structure in the TRH textile is available for local heating, which has been demonstrated for thermal therapy.

A one‐dimensional fluidic nanogenerator with a high power conversion efficiency

Electricity generation from flowing water has been developed for over a century and plays a critical role in our lives. Generally, heavy and complex facilities are required for electricity generation, while using these technologies for applications that require a small size and high flexibility is difficult. Here, we developed a fluidic nanogenerator fiber from an aligned carbon nanotube sheet to generate electricity from any flowing water source in the environment as well as in the human body. The power conversion efficiency reached 23.3 %. The fluidic nanogenerator fiber was flexible and stretchable, and the high performance was well-maintained after deformation over 1 000 000 cycles. The fiber also offered unique and promising advantages, such as the ability to be woven into fabrics for large-scale applications.

Designing one-dimensional supercapacitors in a strip shape for high performance energy storage fabrics

With the advancement of miniaturized portable and wearable electronic devices, fiber-shaped energy-storage systems have attracted intensive attention due to their merits of flexibility, integratability and weavability. However, the inferior energy storage performance and relatively low stability derived from the curved fiber interface under severe deformations have largely limited their development. Here, we report a one-dimensional supercapacitor in a strip shape by mimicking bamboo strips of Chinese bed-mats. The strip-shaped supercapacitor is flexible with decent electrochemical performances. It delivers both a high energy density of 9.56 mW h cm−3 and a high power density of 2.91 W cm−3 that are sustainable to various deformations and outperforms other fiber-shaped counterparts. Such strip-shaped supercapacitors are further woven into a fabric that demonstrates both high structural and electrochemical stability under various deformations such as bending and twisting. The capability for high energy storage and feasibility for large-scale production provide an efficient platform in powering micro-electronic devices.

A Li-Air Battery with Ultralong Cycle Life in Ambient Air

The Li-air battery represents a promising power candidate for future electronics due to its extremely high energy density. However, the use of Li-air batteries is largely limited by their poor cyclability in ambient air. Herein, Li-air batteries with ultralong 610 cycles in ambient air are created by combination of low-density polyethylene film that prevents water erosion and gel electrolyte that contains a redox mediator of LiI. The low-density polyethylene film can restrain the side reactions of the discharge product of Li2 O2 to Li2 CO3 in ambient air, while the LiI can facilitate the electrochemical decomposition of Li2 O2 during charging, which improves the reversibility of the Li-air battery. All the components of the Li-air battery are flexible, which is particularly desirable for portable and wearable electronic devices.

Textile Display for Electronic and Brain‐Interfaced Communications

Textile displays are poised to revolutionize current electronic devices, and reshape the future of electronics and related fields such as biomedicine and soft robotics. However, they remain unavailable due to the difficulty of directly constructing electroluminescent devices onto the textile-like substrate to really display desired programmable patterns. Here, a novel textile display is developed from continuous electroluminescent fibers made by a one-step extrusion process. The resulting displaying textile is flexible, stretchable, three-dimensionally twistable, conformable to arbitrarily curved skins, and breathable, and can dynamically display a series of desired patterns, making it useful for bioinspired electronics, soft robotics, and electroluminescent skins, among other applications. It is demonstrated that these displaying textiles can also communicate with a computer and mouse brain for smart display and camouflage applications. This work may open up a new direction for the integration of wearable electroluminescent devices with the human body, providing new and promising communication platforms.