Hybrid Sn3O2(OH)2/Graphene Nanomaterials: From Solid Li-Ion Battery Anode to Flowable Nanoelectrofuel
This study focuses on comparative characterization of solid casted and nanoelectrofuel anodes from the same type of hybrid nanomaterial composed of Sn3O2(OH)2nanoparticles that were deposited directly onto graphene nano-platelets (GnP). By using this hybrid particle morphology, we achieved good electrical conductivity to an ensemble of individual anode nanoparticles and kept the size of individual particles under the self-healing threshold to address degradation of Sn nanoparticles due to the well-known volume expansion mechanism.
Electrochemical behavior (galvanostatic charge/discharge curves) were measured in pouch and coin cells for solid-casted hybrid anodes and for the same nanomaterials formulated into nanoelectrofuels the tests were conducted in a custom nanoelectrofuel test cell simulating flow with magnetic stirrer. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for characterization of starting nanomaterials as well as current collectors and nanomaterials after electrochemical tests.
In situ x-ray absorption spectroscopy, specifically extended x-ray absorption fine structure (EXAFS) spectroscopy measurements were made to determine local structural changes around Sn atoms during several charge/discharge cycles of a solid casted electrode in a pouch cell. A new degradation mechanism for these materials different from well-known volume expansion is proposed based on EXAFS modeling, and correlating observed structural changes to electrochemical performance.
Although nanoelectrofuel electrodes are very complex systems that require significant efforts in formulation as well as cell engineering, we were able to achieve a respectable reversible capacity compared to solid casted electrodes. Initial electrochemical and material characterization will be presented along with plans for future improvement.