Although some strategies have been triggered to address the intrinsic drawbacks of zinc (Zn) anodes in aqueous Zn‐ion batteries (ZIBs), the larger issue of Zn anodes unable to cycle at a high current density with large areal capacity is neglected. Herein, the zinc phosphorus solid solution alloy (ZnP) coated on Zn foil (Zn@ZnP) prepared via a high‐efficiency electrodeposition method as a novel strategy is proposed. The phosphorus (P) atoms in the coating layer are beneficial to fast ion transfer and reducing the electrochemical activation energy during Zn stripping/plating processes. Besides, a lower energy barrier of Zn2+ transferring into the coating can be attained due to the additional P. The results show that the as‐prepared Zn@ZnP anode in the symmetric cell can be cycled at a current density of 15 mA cm−2 with an areal capacity of 48 mAh cm−2 (depth of discharge, DOD ≈ 82%) and even at an ultrahigh current density of 20 mA cm−2 and DOD ≈ 51%. Importantly, a discharge capacity of 154.4 mAh g−1 in the Zn/MnO2 full cell can be attained after 1000 cycles at 1 A g−1. The remarkable effect achieved by the developed strategy confirms its prospect in the large‐scale application of ZIBs for high‐power devices.
There is ever-increasing interest yet grand challenge in developing programmable untethered soft robotics. Here we address this challenge by applying the asymmetric elastoplasticity of stacked graphene assembly (SGA) under tension and compression. We transfer the SGA onto a polyethylene (PE) film, the resulting SGA/PE bilayer exhibits swift morphing behavior in response to the variation of the surrounding temperature. With the applications of patterned SGA and/or localized tempering pretreatment, the initial configurations of such thermal-induced morphing systems can also be programmed as needed, resulting in diverse actuation systems with sophisticated three-dimensional structures. More importantly, unlike the normal bilayer actuators, our SGA/PE bilayer, after a constrained tempering process, will spontaneously curl into a roll, which can achieve rolling locomotion under infrared lighting, yielding an untethered light-driven motor. The asymmetric elastoplasticity of SGA endows the SGA-based bi-materials with great application promise in developing untethered soft robotics with high configurational programmability.
The aqueous zinc-ion batteries (ZIBs) have been considered as a promising energy storage device. However, the ion transfer at the Zn metal anode–electrolyte interface is limited by the sluggish kinetics resulting in high interface resistance. Herein, mesoporous TiO2 (m-TiO2) is coated on the Zn foil (Zn-TiO2) driving the ion’s faster transfer to reduce interface resistance (70.1 Ω vs 799.3 Ω of bare Zn). The lower interface resistance is ascribed to shortening the ion transfer path provided by the mesoporous structure and the smaller Zn2+ absorption energy barrier of the surface of the Zn-TiO2 anode as well as the unobstructed ion transfer path at the crystal planes (100) of TiO2, which have been supported by the density functional theory (DFT) calculation and experiments. Therefore, the Zn-TiO2 anodes in the symmetrical cells display a low voltage hysteresis (36.5 mV) and long-term cycling stability (500 h at 4.4 mA cm–2). Especially, the Zn-TiO2/MnO2 full cells show superior cycling performance with a high capacity of 269.8 mAh g–1 after 50 cycles at 0.2 A g–1 and 210.9 mAh g–1 after 1000 cycles at 0.5 A g–1. The analysis of ion-transfer kinetics at the interface provides deep enlightenment and reference for the study of the metal anodes.
The essence of Zn dendrite formation is ultimately derived from Zn nucleation and growth during the repeated Zn plating/stripping process. Here, the nucleation process of Zn has been analyzed using ex situ scanning electron microscopy to explore the formation of the initial Zn dendrite, demonstrating that the formation of tiny protrusions (the initial state of Zn dendrites) is caused by the inhomogeneity of Zn nucleation. Based on this, the uniform Zn nucleation is promoted by the Ni5Zn21 alloy coating (ZnNi) on the surface of Zn foil by electrodeposition, and the mechanism of ZnNi-promoted even nucleation is further analyzed with the assistance of density functional theory (DFT). The DFT results indicate that the ZnNi displays a stronger binding ability to Zn compared to the bare Zn, suggesting that Zn nuclei will preferentially form around ZnNi instead of continuing to grow on the surface of the initial Zn nuclei. Therefore, the designed Zn metal anode (Zn@ZnNi) can be ultra-stable for over 2200 h at a current density of 2 mA cm–2 in the symmetric cell. Even at a much higher current density of 20 mA cm–2, the extra-long life of over 2200 cycles (over 530 h) can be achieved. Moreover, the full cell with the Zn@ZnNi anode exhibits extra-long cycling performance for 500 cycles with a capacity of 207.7 mA h g–1 and 1100 cycles (148.5 mA h g–1) at a current density of 0.5 and 1 A g–1, respectively.
expansion coefficient in a wide temperature range. [2] CFs can not only be used as efficient thermal-management materials to maintain the functionality and reliability of microelectronic components with high heat flux, but also be used as high-performance composites for thermal protection of flight devices in the aerospace field. [3] In spite of their wide uses, the specific pitch-based CFs are the only commercial species of highly thermally conductive CFs with high cost. [4] As a comparison, the other commercial PAN-based CFs have strong mechanical properties but poor thermal conductivity due to their limited graphitic crystallinity, determining their confined application as lightweight structural materials. [2a,5] In this context, it is necessary to expand alternative sources of highly thermally conductive fibers beyond the sole pitch-based CFs. [2b,6] An intuitive option is translating PAN-based CFs to highly thermally conductive species, but remains a forbidden task that is challenged by the intrinsic incompatibility between the 1D topology of linear polymers and the 2D topology of target graphitic crystallinity. [5b,7] The thermal conductivity of graphitic materials is determined by their complicated nano textures and spans a wide range from ≈6 W m −1 K −1 in glassy carbon to ≈2000 W m −1 K −1 in pyrolytic graphite at room temperature. [8] In principle, the Highly thermally conductive carbon fibers (CFs) have become an important material to meet the increasing demand for efficient heat dissipation. To date, high thermal conductivity has been only achieved in specific pitch-based CFs with high crystallinity. However, obtaining high graphitic crystallinity and high thermal conductivity beyond pitch-CFs remains a grand challenge. Here, a 2D-topology-seeded graphitization method is presented to mediate the topological incompatibility in graphitization by seeding 2D graphene oxide (GO) sheets into the polyacrylonitrile (PAN) precursor. Strong mechanical strength and high thermal conductivity up to 850 W m −1 K −1 are simultaneously realized, which are one order of magnitude higher in conductivity than commercial PAN-based CFs. The self-oxidation and seeded graphitization effect generate large crystallite size and high orientation to far exceed those of conventional CFs. Topologically seeded graphitization, verified in experiments and simulations, allows conversion of the non-graphitizable into graphitizable materials by incorporating 2D seeds. This method extends the preparation of highly thermally conductive CFs, which has great potential for lightweight thermal-management materials.
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