UC Riverside

As the development of consumer devices and the application of electric vehicles, high energy-density lithium ion batteries (LIBs) are required. However, the energy density and capacity of current commercial LIBs are very limited because of the electrodes. Therefore, high energy-density and specific capacity electrodes materials are needed. Silicon is considered as the most promising next generation anode materials for LIBs due to their high energy density, high theoretical capacities (3600 mAh g-1) and abundance. In this work, we synthesized coral-like Si powders with a three-dimensionally-interconnected structure via a facile and scalable maghesiothermic reduction method. The high porosity of the Si nanospheres can accommodate the volume expansion and release strain-stress within structure during lithiation and delithiation process, respectively. Besides, the coral-like and interconnected structure offers shorter Li+ diffusion path. The Si nanospheres based anode demonstrates a reversible capacity of 3172 mAh g-1 at high rate of C/2. After 500 cycles, the capacity retention is 1018 mAh/g, showing a fading rate 57%, with columbic efficiency more than 99%. We believe that, this low cost, facile and scalable synthesizing of porous Si nanospheres with interconnected network materials be widely used as Si based anodes for LIBs.

Since the capacity of lithium ion battery is decided by capacities of both electrodes, next-generation cathode materials also attract lots of interests. The sulfur-based cathode has attracted extensive attention because of its high capacity of 1672 mAh g-1 and its high abundance. However, the sulfur shuttling effects and the loss of active material during lithiation hinder its commercial application. To tackle these issues, we introduced polymerized organo-sulfur units to the elemental sulfur materials. The composite with 86% sulfur content was prepared using 1,3-diethynylbenzen and sulfur particles via scalable invers vulcanization. The sulfur content in copolymer sulfur was achieved as high as 86%. Our copolymer-sulfur composite cathode showed excellent cycling performance with a capacity of 454 mAh g-1 at 0.1 C after 300 cycles. We demonstrate that the organosulfur-DEB units in the sulfur cathode serve as the ‘plasticizer’ to effectively prevent the polysulfide shuttling.