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The development of high-performance battery technologies necessitates ultrathin separators with superior mechanical strength and electrochemical properties. We present an innovative 1 µm thick, pinhole-free zeolitic imidazolate framework-8 (ZIF-8) layer, cathodically deposited on an 8 µm thick commercial polypropylene (PP) film in a rapid process, resulting in a ZIF-8@8-µm PP flexible membrane. This crack-free ZIF-8 layer, featuring angstrom-scale pores and chemical polar groups, functions as a Li+ sieve, regulating Li+ transport, controlling Li deposition, and blocking dissolved active cathode materials. It also enhances Li+ diffusion and transference number, extending the Sand’s time for Li dendrite formation. Consequently, the ZIF-8@8-µm PP separator addresses polysulfide shuttling in Li-S batteries and Li dendrite formation in Li-metal batteries, significantly improving their performance compared to conventional separators. Our findings indicate that while the 8-μm PP alone is unsuitable as a battery separator, the ZIF-8@8-μm PP, possesses the mechanical strength and electrochemical properties necessary for developing both Li-S and Li-metal batteries, as well as application in conventional Li-ion batteries with enhanced volumetric energy densities. 

Many transition-metal-oxide-based catalysts have been investigated to chemically bind soluble lithium polysulfides and accelerate their redox kinetics in lithium-sulfur (Li-S) battery chemistry. However, the intrinsic poor electrical conductivities of these oxides restrict their catalytic performance, consequently limiting the sulfur utilization and the rate performance of Li-S batteries. Herein, we report a freestanding electrocatalytic sulfur host consisting of hydrogen-treated VO2 nanoparticles (H-VO2) anchored on nitrogen-doped carbonized bacterial cellulose aerogels (N-CBC). The hydrogen treatment enables the formation and stabilization of the rutile VO2(R) phase with metallic conductivity at room temperature, significantly enhancing its catalytic capability compared to the as-synthesized insulative VO2(M) phase. Several measurements characterize the electrocatalytic performance of this unique H-VO2@N-CBC structure. In particular, the two kinetic barriers between S8, polysulfides, and Li2S are largely reduced by 28.2 and 43.3 kJ/mol, respectively. Accordingly, the Li-S battery performance, in terms of sulfur utilization and charge/discharge rate, is greatly improved. This work suggests an effective strategy to develop conductive catalysts based on a typical transition metal oxide (VO2) for Li-S batteries. 

Abstract Electrochemical capacitors (ECs) offer superior specific capacitance for energy storage compared to traditional electrolytic capacitors but face limitations in alternating current (AC) filtering due to the need for balancing fast response and high capacitance. This study addresses these challenges by developing a freestanding nanostructured carbon electrode, derived from the rapid carbonization of bacterial cellulose (BC) embedded with zeolitic imidazolate framework 8 (ZIF‐8) and in situ formed carbon nanotubes (CNTs). The electrode exhibits an exceptionally low area resistance of 9.8 mΩ cm²and a high specific capacitance of 2.1 mF cm⁻²at 120 Hz, maintaining performance even at high frequencies. Stacking these electrodes enhances the capacitance to 5.3 mF cm⁻², with the phase angle degrading to −74.4° at 120 Hz; however, they retain a phase angle below −45° up to ≈50 kHz, demonstrating excellent high‐frequency performance. Furthermore, connecting three aqueous units in series as an integrated cell or utilizing organic electrolytes extends the voltage window to 2.4 V, enhancing their suitability for high‐voltage applications. Ripple voltage analysis under various loads and frequencies indicates effective filtering capabilities, highlighting the potential of these nanostructured ECs for next‐generation electronic applications. 

Polysulfide shuttle effect, causing extremely low Coulombic efficiency and cycling stability, is one of the toughest challenges hindering the development of practical lithium sulfur batteries (LSBs). Introducing catalytic nanostructures to stabilize the otherwise soluble polysulfides and promote their conversion to solids has been proved to be an effective strategy in attacking this problem, but the heavy mass of catalysts often results in a low specific energy of the whole electrode. Herein, by designing and synthesizing a free-standing edge-oriented NiCo 2 S 4 /vertical graphene functionalized carbon nanofiber (NCS/EOG/CNF) thin film as a catalytic overlayer incorporated in the sulfur cathode, the polysulfide shuttle effect is largely alleviated, revealed by the enhanced electrochemical performance measurements and the catalytic function demonstration. Different from other reports, the NiCo 2 S 4 nanosheets synthesized here have a 3-D edge-oriented structure with fully exposed edges and easily accessible in-plane surfaces, thus providing a high density of active sites even with a small mass. The EOG/CNF scaffold further renders the high conductivity in the catalytic structure. Combined, this novel structure, with high sulfur loading and high sulfur fraction, leads to high-performance sulfur cathodes toward a practical LSB technology. 

Core-shell structured sulfur composite nanoparticles (NPs) and their various derivatives have been widely inves- tigated as a promising cathode material for Li-S batteries (LSBs) thanks to their unique features in suppressing the lithium polysulfides shuttle effect, accommodating the sulfur electrode volume change, and providing abundant electrochemically active sites. The commonly used infiltration strategy falls short in producing a near ideal core- shell structure. Accordingly, the strategy of encapsulation, in which the prefabricated sulfur or sulfur precursor nanocore is encapsulated by a subsequently formed host shell has attracted broad interest, and this technique has significantly accelerated the LSB development. To advance the state of the art in producing encapsulated sulfur NPs, it becomes necessary to systematically survey the past relevant works and sum up research gaps. This review first takes an excursion to the infiltration strategy to highlight its limitations, followed by surveys on studies of synthesizing sulfur NPs, encapsulating sulfur NPs, and producing encapsulated sulfur NPs from metal sulfides. The strengths and weaknesses of each method, the resulted NPs, their electrochemical properties and the associated LSB performances are particularly emphasized. The rationales to design and the results of applying structural derivatives of the conventional core-shell configuration are then assessed. The encapsulated sulfur NPs applied in aqueous batteries are also discussed. This comprehensive review on sulfur encapsulation is concluded by a summary on further challenges and opportunities as well as our perspectives on possible future research directions, towards fundamental understanding and practical development of encapsulated sulfur NP-based LSB technology.