Zhen Meng

Effect of Boron-Doping on the Graphene Aerogel Used as Cathode for the Lithium-Sulfur Battery.

A porous interconnected 3D boron-doped graphene aerogel (BGA) was prepared via a one-pot hydrothermal treatment. The BGA material was first loaded with sulfur to serve as cathode in lithium-sulfur batteries. Boron was positively polarized on the graphene framework, allowing for chemical adsorption of negative polysufide species. Compared with nitrogen-doped and undoped graphene aerogel, the BGA-S cathode could deliver a higher capacity of 994 mA h g(-1) at 0.2 C after 100 cycles, as well as an outstanding rate capability, which indicated the BGA was an ideal cathode material for lithium-sulfur batteries.

Ultrasmall Sn nanodots embedded inside N-doped carbon microcages as high-performance lithium and sodium ion battery anodes

Sn based materials are promising anodes both in Li-ion batteries and Na-ion batteries due to their high theoretical capacities (994 mA h g−1 for LIBs and 847 mA h g−1 for SIBs, respectively). In order to improve the cycle performance, Sn/N-doped carbon microcage composites (Sn/NMCs) with Sn nanodots uniformly embedded inside the N-doped carbon microcages are synthesized through a simple spray drying process, followed by thermal treatment. When used as electrodes, Sn/NMCs exhibit an initial reversible capacity of 780 mA h g−1 at 200 mA g−1, and maintain 472 mA h g−1 after 500 cycles in LIBs. For Na-ion batteries, Sn/NMCs deliver an initial reversible capacity of 439 mA h g−1 at 50 mA g−1 and maintain 332 mA h g−1 after 300 cycles. The remarkable electrochemical performance is mainly owing to the advanced structure of Sn/NMCs, which could be attributed to the pore-formation using NaCl, and the grain size inhibition of Sn using N-doped carbon. Moreover, this preparation method is accessible to scale up and can be extended to fabricate other electrode materials.

A composite with SiOx nanoparticles confined in carbon framework as an anode material for lithium ion battery

A composite with ultrafine SiOx (x = 1.57, around 2 nm) nanoparticles confined in a carbon framework is synthesized by a simple thermopolymerization process and subsequent heat treatment. In the composite, the carbon framework can provide a consecutive network to improve the electrical conductivity of the composite and cushion the volume expansion to prevent the active material peeling from the current collector. The ultrafine SiOx nanoparticles can alleviate mechanical strain and shorten the diffusion/transport distance of lithium ions and electrons. In consequence, the as-synthesized composite delivers a high reversible capacity of 540 mA h g−1 at a current density of 500 mA g−1 after 200 cycles. The composite delivers good electrochemical performance, making it a promising candidate for the next-generation high-energy LIBs.

Polyiodide-Shuttle Restricting Polymer Cathode for Rechargeable Lithium/Iodine Battery with Ultralong Cycle Life

Rechargeable lithium/iodine (Li/I2) batteries have attracted much attention because of their high gravimetric/volumetric energy densities, natural abundance and low cost. However, problems of the system, such as highly unstable iodine species under high temperature, their subsequent dissolution in electrolyte and continually reacting with lithium anode prevent the practical use of rechargeable Li/I2 cells. A polymer-iodine composite (polyvinylpyrrolidone-iodine) with high thermostability is employed as cathode material in rechargeable Li/I2 battery with an organic electrolyte. Because of the chemical interaction between polyvinylpyrrolidone (PVP) and polyiodide, most of the polyiodide in the cathode could be effectively trapped during charging/discharging. In-situ Raman observation revealed the evolution of iodine species in this system could be controlled during the process of I5- ↔ I3- ↔ I-. Herein, the Li/I2 battery delivered a high discharge capacity of 278 mAh g-1 at 0.2 C and exhibited a very low capacity decay rate of 0.019% per cycle for prolonged 1100 charge/discharge cycles at 2 C. More importantly, a high areal capacity of 4.1 mAh cm-2 was achieved for the electrode with high iodine loading of 21.2 mg cm-2. This work may inspire new approach to design the Li/I2 (or Li/polyiodide) system with long cycle life.

Naturally abundant high-performance rechargeable aluminum/iodine batteries based on conversion reaction chemistry

Rechargeable multivalent ion (Al3+, Mg2+ and Zn2+) batteries provide a viable alternative to lithium ion batteries because of the supply risk of lithium resources and safety concern. In this study, rechargeable metal–iodine batteries, particularly aluminum/iodine batteries, were fabricated with novel active carbon cloth/polyvinylpyrrolidone (ACC/PVPI) composite cathodes prepared via a facile solution-adsorption method combined with freeze-drying. The use of active carbon cloth (ACC) endows the composites superior electronic conductivity, and significantly decreases the weight of the electrode due to its function as a current collector. Hydrogen bonding interaction between PVP and iodine in PVPI guarantees the depression of the shuttle effect of polyiodide, thus lengthening the cycle life. The density functional theory (DFT) analysis shows that such shuttle depression occurs due to the hydrogen-bonded iodine species, and the relatively large formation energy hints at higher conversion reaction efficiency of Al ion batteries. These characteristics make the composites an ideal electrode in various metal ion batteries. To be specific, the Al/I2 battery with a distinct working potential window achieves a high capacity of 180.1 mA h g−1 at 0.2C and can remain stable after 500 cycles with a stable capacity of 127 mA h g−1 at 0.6C. Moreover, at higher current density of 1C, the battery delivers a capacity of 102.7 mA h g−1 for up to 1050 cycles. These above-mentioned characteristics of metal–iodine (Li, Mg and Al/I2) batteries, related electrochemical performance measurements and theoretical modeling analysis show that the rechargeable iodine-based batteries provide a promising direction in designing high-performance energy storage/transfer systems.