Preceramic Polymer Derived Ceramic Hybrid Anodes for Extreme Rate Capable LIBs

Abstract

Lithium ion batteries (LIB) are, by far, the most promising energy storage devices that find application in numerous equipment of varying utility and dimension, from hand held systems to automotive. Growing demand for high energy density and high power density batteries has shifted the attention from graphitic anodes to many oxides, alloys, and hybrid materials with higher specific capacity. Preceramic polymer derived silicon oxycarbide (SiOC) materials have evolved to be an important candidate for next generation anodes. Polymer derived ceramics (PDC) are known for their exceptional heat resistance, zero creep strain rate, piezoresistivity, photoluminescence, and Li ion intercalablity. The unique nanostructure comprising of SiO2 nanodomains and graphene type carbon layers, and regions of mixed bond tetrahedral, of these materials exhibit specific capacity in the range of 800-1000 mA h g-1, which is excellent for anode applications in Li ion batteries.

However, demanding applications in current generation hybrid electric vehicles and power tools underscore the importance of instant power delivery. Therefore, novel design of materials chemistry, morphology, and nanostructure must be adopted to control the kinetics of Li ion sequestration in and out of the electrodes, enabling high current rate charge and discharge. In the current work we have proposed a generic method in which a nanodimensional coating of the SiOC ceramics was processed around a nanostructured ceramic template (eg. TiO2). The hybrid ceramic afforded enhanced specific surface area, from <1 of the PDC to >200 m2 g-1 for the hybrid. The synthesized hybrid materials exhibited extreme rate capability with symmetric cycling up to current rate of 20,000 mA g-1. Based on the easy accessibility of the liquid electrolyte at the hybrid interface the diffusion path of Li ions was significantly reduced. Furthermore, the cells exhibited excellent cyclic stability under extreme electrochemical cycling. The abused anode assembly was found in tact and exhibited no material recession. The process is generic in that a host of different types of organic/inorganic templates can be used with an ability to control the PDC coating thickness. The presentation will expose new approaches to the processing of nanostructured hybrid ceramics for their exploitation as anodes in high energy and high power density LIBs.