Compacted N-Doped 3D Bicontinuous Nanoporous Graphene/Carbon Nanotubes@Ni-Doped MnO2 Electrode for Ultrahigh Volumetric Performance All-Solid-State Supercapacitors at Wide Temperature Range.

Developing wide temperature range flexible solid-state supercapacitors with high volumetric energy density is highly desirable to meet the demands of the rapidly developing field of miniature consumer electronic devices and promote their widespread adoption. Herein, high-quality dense N-doped 3D porous graphene/carbon nanotube (N-3DG/CNTs) hybrid films are prepared and used as the substrate for the growth of Ni-doped MnO2 (Ni-MnO2 ). The integrated and interconnected architecture endows N-3DG/CNTs@Ni-MnO2 composite electrodes' high conductivity and fast ion/electron transport pathway. Subsequently, 2.4 V solid-state supercapacitors are fabricated based on compacted N-3DG/CNTs@Ni-MnO2 positive electrodes, which exhibit an ultrahigh volumetric energy density of 78.88 mWh cm-3 based on the entire device including electrodes, solid-state electrolyte, and packing films, excellent cycling stability up to 10 000 cycles, and a wide operating temperature range from -20 to 70 °C. This work demonstrates a design of flexible solid-state supercapacitors with exceptional volumetric performance capable of operation under extreme conditions.

Class of Solid-like Electrolytes for Rechargeable Batteries Based on Metal-Organic Frameworks Infiltrated with Liquid Electrolytes.

A new family of solid-like electrolytes was developed by infiltrating MIL-100(Al), an electrochemically stable metal-organic-framework (MOF) material, with liquid electrolytes that contain cations from the 3rd period (Na+, Mg2+, and Al3+) and the 1st group (Li+, Na+, K+, and Cs+). The anions were immobilized within the MOF scaffolds upon complexing with the open metal sites, allowing effective transport of the cations in the nanoporous channels with high conductivity (up to 1 mS cm-1) and low activation energy (down to 0.2 eV). This general approach enables the fabrication of superior conductive solid-like electrolytes beyond lithium ions.

Covalently Bonded Si-Polymer Nanocomposites Enabled by Mechanochemical Synthesis as Durable Anode Materials.

Silicon is one of the most promising anode materials for lithium-ion batteries due to its high theoretical capacity and low cost. However, significant capacity fading caused by severe structural degradation during cycling limits its practical implication. To overcome this barrier, we design a covalently bonded nanocomposite of silicon and poly(vinyl alcohol) (Si-PVA) by high-energy ball-milling of a mixture of micron-sized Si and PVA. The obtained Si nanoparticles are wrapped by resilient PVA coatings that covalently bond to the Si particles. In such nanostructures, the soft PVA coatings can accommodate the volume change of the Si particles during repeated lithiation and delithiation. Simultaneously, as formed covalent bonds enhance the mechanical strength of the coatings. Due to the significantly improved structural stability, the Si-PVA composite delivers a lifespan of 100 cycles with a high capacity of 1526 mAh g-1. In addition, a high initial Coulombic efficiency of over 86% and an average value of 99.2% in subsequent cycles can be achieved. This reactive ball-milling strategy provides a low-cost and scalable route to fabricate high-performance anode materials.

Electrolyte Membranes with Biomimetic Lithium-Ion Channels.

High-performance lithium-ion batteries (LIBs) demand efficient and selective transport of lithium ions. Inspired by ion channels in biology systems, lithium-ion channels are constructed by chemically modifying the nanoporous channels of metal-organic frameworks (MOFs) with negatively charged sulfonate groups. Analogous to the biological ion channels, such pendant anionic moieties repel free anions while allowing efficient transport of cations through the pore channels. Implementing such MOFs as an electrolyte membrane doubly enhances the lithium-ion transference number, alleviates concentration polarization, and affords striking durability of high-rate LIBs. This work demonstrates an ion-selective material design that effectively tunes the ion-transport behavior and could assist with more efficient operation of LIBs.

Porous carbon microspheres with highly graphitized structure for potassium-ion storage.

Porous carbon materials are promising candidates for anode materials in rechargeable potassium-ion batteries. However, their high surface area and low crystallinity usually cause side reactions with electrolytes and slanted charge/discharge profiles. Herein, we report the synthesis of porous carbon microspheres with highly graphitized structure and enhanced potassium-ion storage properties. The prepared carbon microspheres exhibit a low working potential of ~0.2 V, high Coulombic efficiency, and a stable reversible capacity of 292.0 mAh/g after 100 cycles, which is significantly higher than that of commercial graphite (137.5 mAh/g after 100 cycles). These desirable performances are attributed to the high crystallinity of carbon and its porous structure, which provide active sites for potassium-ion storage and alleviate the stress caused by the large volume change during the insertion and extraction of potassium ions.

A Powder Metallurgic Approach toward High-Performance Lithium Metal Anodes.

The development of lithium metal anodes capable of sustaining large volume changes, avoiding lithium dendrite formation, and remaining stable in ambient air is crucial for commercially viable lithium metal batteries. Toward this goal, the fabrication of porous and lithiophilic copper scaffolds via a powder metallurgy strategy is reported. Infiltrating the scaffolds with molten lithium followed by exposure to Freon R134a produces lithium metal anodes with dramatically improved rate performance and cycling stability. This work provides a simple yet effective route for the fabrication of safe, low-cost lithium metal batteries with high energy density.