Miniaturized spectrometers are of considerable interest for their portability. Most designs to date employ a photodetector array with distinct spectral responses or require elaborated integration of micro & nano optic modules, typically with a centimeter-scale footprint. Here, we report a design of a micron-sized near-infrared ultra-miniaturized spectrometer based on two-dimensional van der Waals heterostructure (2D-vdWH). By introducing heavy metal atoms with delocalized electronic orbitals between 2D-vdWHs, we greatly enhance the interlayer coupling and realize electrically tunable infrared photoresponse (1.15 to 1.47 μm). Combining the gate-tunable photoresponse and regression algorithm, we achieve spectral reconstruction and spectral imaging in a device with an active footprint < 10 μm. Considering the ultra-small footprint and simple fabrication process, the 2D-vdWHs with designable bandgap energy and enhanced photoresponse offer an attractive solution for on-chip infrared spectroscopy.
The lithium dendrite issue is a major bottleneck that limits the utilization of lithium metal anodes in high‐energy rechargeable batteries. From the perspective of the dendrite nucleation mechanism, this work develops a new type of cation‐selective (CS) separator with anion immobilization behavior to boost the lithium metal anode. By taking advantage of the poly(vinylidene fluoride) matrix, a strong binding force with anions contributes to an excellent CS property of the separator, which is further confirmed by molecular dynamics simulations. The CS separator developed in this work presents a high lithium‐ion transference number up to 0.81. Considering such a dramatically reduced transference number of anions, it can prolong the nucleation time of lithium dendrite and thus achieve a high‐stable Li plating/stripping cycling for 1000 h at a high applied current density of 3 mA cm−2. The Li metal stabilization function of the CS separator is further studied in detail through both in‐situ and ex‐situ observations of dendrites growth. When integrating into lithium metal batteries (LMBs), the CS separators also contribute to enhanced electrochemical performances including discharge capacity, rate capability, and cycling durability. This work is anticipated to provide considerable insight for the creative design of CS separators toward dendrite‐free LMBs.
Due to the excellent specific capacity and high working voltage, manganese oxide (MnO 2 ) has attracted considerable attention for aqueous zinc-ion batteries (AZIBs). However, the irreversible structural collapse and sluggish ionic diffusion lead to poor rate capability and inferior lifespan. Herein, we proposed a novel organic/inorganic hybrid cathode of carbon-based poly(4,4'-oxybisbenzenamine)/MnO 2 (denoted as C@PODA/MnO 2 ) for AZIBs. Various in/ex situ analyses and theoretical calculations prove that PODA chains with C=N groups can provide a more active surface/ interface for ion/electron mobility and zinc ion storage in the hybrid cathode. More importantly, newly formed MnÀ N interfacial bonds can effectively promote ion diffusion and prevent Mn atoms dissolution, enhancing redox kinetics and structural integrity of MnO 2 . Accordingly, C@PODA/MnO 2 cathode exhibits high capacity (321 mAh g À 1 or 1.7 mAh cm À 2 at 0.1 A g À 1 ), superior rate performance (88 mAh g À 1 at 10 A g À 1 ) and excellent cycling stability over 2000 cycles. Hence, rational interfacial designs shed light on the development of organic/ inorganic cathodes for advanced AZIBs.
Organic electrode materials have
a large variety of types and could
be a replacement for metal compounds in building high-performance
rechargeable Zn-ion batteries. Polymers with redox activity can be
divided into amino-containing aromatics and quinones, and they show
different electrochemical behaviors. Here, we compare two representative
polymers, poly(1,5-naphthalenediamine) and poly(1,5-dihydroxynaphthalene),
that are electrodeposited onto nanoporous carbon to make cathodes
for Zn-ion batteries. Electrochemical energy storage performances
of the two polymers are tested at different temperatures ranging from
20 to −20 °C, and the influence of low temperature on
their capacity loss, charge transfer resistance, and activation energy
is determined. By combining experiment with theory, we unravel key
factors of the polymer that favor energy storage performance. The
entropy change in the Zn-ion uptake process of an organic electrode
material is found to play a key role in the energy storage performance
in terms of cycling stability and capacity retention in a cold environment.
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