Nanocarbon/Inorganic Nanoparticle Hybrid Materials for Energy Storage and Fuel Cells

Researchers in Prof. Hongjie Dai's laboratory have combined graphene with metals and other inorganic elements to create a variety of hybrid materials that can be used for high performance electrocatalytic or electrochemical devices such as batteries and fuel cells. One type of hybrid material is formed from nanocrystals grown on graphene nanoplates or nanorods. This material is designed for use as an electrode for fast, efficient energy storage and conversion. Another type is formed from nanocrystals grown on reduced graphene oxide to produce high-performance, bi-functional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). A third type is a unique ORR catalyst formed from carbon nanotube-graphene complexes.

The inventors have demonstrated the technology in the following applications:

Pseudocapacitor materials - Ni(OH)2 nanocrystals grown on graphene sheets showed a specific capacitance of ~1335 F/g at charge and discharge current density of 2.8 A/g and ~953 F/g at 45.7 A/g with excellent cycling ability.
High capacity anode for Lithium Ion batteries - Mn₃O₄ on reduced graphene oxide showed specific capacity up to ~900 mAh/g with good rate capability and cycling stability.
ORR/OER catalyst - Co₃O₄/N-doped graphene that has catalytic activity similar to platinum but with superior stability in alkaline solutions. This material also has high OER activity. The unusual catalytic activity arises from synergetic chemical coupling effects between Co₃O₄ and graphene.
ORR catalyst - Carbon nanotube-graphene complexes with small amounts of irons and nitrogen impurities have high ORR activity and superior stability in acidic solution; and in alkaline solution this material shows a ORR activity that closely approaches that of platinum.
Ultrafast Nickel-Iron battery - Ni(OH)₂/multiwall nanotube and FeOx/graphene electrodes increased charging and discharging rates nearly 1000x over traditional Ni-Fe batteries. The battery can be charged in ~2 min. and discharged within 30s to deliver a specific energy of 120 Wh/kg and specific power of 15kW/kg.
Zinc-air battery - An electrode with CoO/carbon nanotube hybrid ORR catalyst and Ni-Fe-layered double hydroxide OER catalyst had higher catalytic activity and durability in concentrated alkaline than platinum and iridium catalysts. The battery had peak power density ~265 mW/cm², current density ~200 mA/cm² at 1 V, and energy density of >700 Wh/kg; with unprecedented small charge-discharge voltage polarization of ~0.70 V at 20 mA/cm² with high reversibility and stability over long charge and discharge cycles.

Stage of Development:
The technology has been applied in various devices with promising results

Please see related docket S11-094.