Yulong Duan

Sustainable, heat-resistant and flame-retardant cellulose-based composite separator for high-performance lithium ion battery

A sustainable, heat-resistant and flame-retardant cellulose-based composite nonwoven has been successfully fabricated and explored its potential application for promising separator of high-performance lithium ion battery. It was demonstrated that this flame-retardant cellulose-based composite separator possessed good flame retardancy, superior heat tolerance and proper mechanical strength. As compared to the commercialized polypropylene (PP) separator, such composite separator presented improved electrolyte uptake, better interface stability and enhanced ionic conductivity. In addition, the lithium cobalt oxide (LiCoO2)/graphite cell using this composite separator exhibited better rate capability and cycling retention than that for PP separator owing to its facile ion transport and excellent interfacial compatibility. Furthermore, the lithium iron phosphate (LiFePO4)/lithium cell with such composite separator delivered stable cycling performance and thermal dimensional stability even at an elevated temperature of 120°C. All these fascinating characteristics would boost the application of this composite separator for high-performance lithium ion battery.

Rigid-Flexible Coupling High Ionic Conductivity Polymer Electrolyte for an Enhanced Performance of LiMn2O4/Graphite Battery at Elevated Temperature

LiMn2O4-based batteries exhibit severe capacity fading during cycling or storage in LiPF6-based liquid electrolytes, especially at elevated temperatures. Herein, a novel rigid-flexible gel polymer electrolyte is introduced to enhance the cyclability of LiMn2O4/graphite battery at elevated temperature. The polymer electrolyte consists of a robust natural cellulose skeletal incorporated with soft segment poly(ethyl α-cyanoacrylate). The introduction of the cellulose effectively overcomes the drawback of poor mechanical integrity of the gel polymer electrolyte. Density functional theory (DFT) calculation demonstrates that the poly(ethyl α-cyanoacrylate) matrices effectively dissociate the lithium salt to facilitate ionic transport and thus has a higher ionic conductivity at room temperature. Ionic conductivity of the gel polymer electrolyte is 3.3 × 10(-3) S cm(-1) at room temperature. The gel polymer electrolyte remarkably improves the cycling performance of LiMn2O4-based batteries, especially at elevated temperatures. The capacity retention after the 100th cycle is 82% at 55 °C, which is much higher than that of liquid electrolyte (1 M LiPF6 in carbonate solvents). The polymer electrolyte can significantly suppress the dissolution of Mn(2+) from surface of LiMn2O4 because of strong interaction energy of Mn(2+) with PECA, which was investigated by DFT calculation.

1D coaxial platinum/titanium nitride nanotube arrays with enhanced electrocatalytic activity for the oxygen reduction reaction: towards Li-air batteries.

CAT ON A HOT TIN SUPPORT: Coaxial Pt/TiN nanotube arrays are used to achieve a superior electrocatalytic activity of platinum towards the oxygen reduction reaction (ORR). Compared to a commercial Pt/C catalyst, the Pt/TiN NTA materials delivers a higher mass activity and specific activity for the ORR. Hence, these materials are useful as cathodes for hybrid electrolyte Li-air batteries, as demonstrated.

Progress in nitrile-based polymer electrolytes for high performance lithium batteries

Nitrile or cyano-based compounds have aroused interest in high performance battery electrolyte fields due to their unique characteristics such as a high dielectric constant, high anodic oxidization potential and favorable interaction with lithium ions. Particularly, owing to the presence of a unique plastic-crystalline phase, succinonitrile/salt-based solid electrolytes possess an ultra high ionic conductivity of more than 10−3 S cm−1 at room temperature. Herein, recent progress in nitrile-based polymer electrolytes has been reviewed in terms of their potential application in flexible, solid-state or high voltage lithium batteries. Factors affecting the ionic conductivity of nitrile-based electrolytes have also been summarized. We hope that fresh and established researchers can obtain a clear perspective of nitrile based polymer electrolytes and our mini review can spur more extensive interest for the exploration of high performance batteries.

Facile and Reliable in Situ Polymerization of Poly(Ethyl Cyanoacrylate)-Based Polymer Electrolytes toward Flexible Lithium Batteries

Polycyanoacrylate is a very promising matrix for polymer electrolyte, which possesses advantages of strong binding and high electrochemical stability owing to the functional nitrile groups. Herein, a facile and reliable in situ polymerization strategy of poly(ethyl cyanoacrylate) (PECA) based gel polymer electrolytes (GPE) via a high efficient anionic polymerization was introduced consisting of PECA and 4 M LiClO4 in carbonate solvents. The in situ polymerized PECA gel polymer electrolyte achieved an excellent ionic conductivity (2.7 × 10-3 S cm-1) at room temperature, and exhibited a considerable electrochemical stability window up to 4.8 V vs Li/Li+. The LiFePO4/PECA-GPE/Li and LiNi1.5Mn0.5O4/PECA-GPE/Li batteries using this in-situ-polymerized GPE delivered stable charge/discharge profiles, considerable rate capability, and excellent cycling performance. These results demonstrated this reliable in situ polymerization process is a very promising strategy to prepare high performance polymer electrolytes for flexible thin-film batteries, micropower lithium batteries, and deformable lithium batteries for special purpose.