SUNY Binghamton researchers show Si/MgO/graphite composite as high-performance Li-ion anode material
Researchers at the State University of New York (SUNY) at Binghamton, led by Stanley Whittingham, have developed a Si/MgO/graphite composite for use as a high-performance durable anode for lithium-ion batteries. They presented their work at the 219th ECS Meeting in May 2011, and report on it in a paper in press in Electrochemistry Communications.
Silicon-based anode materials have received much interest due to their high capacity and suitable working potential. Pure Si loses most of its capacity after a few cycles because the significant volume change during lithium insertion/extraction causes breakdown of the electrode structure. Downsizing the Si particles, alloying Si with metals, and making Si/C composites are some methods proposed to relieve the volume expansion effect. The cycle life of Si anode could be prolonged these ways, but the capacity decay could still not be avoided.
Recently, some Si/oxide/C composites were found to keep excellent capacity retention when used as anode materials. The oxide inside the composite plays a crucial part in stabilizing the capacity by forming a protective layer.— Zhou (2011a, ECS meeting)
The composite delivered an initial capacity of ~ 700 mAh/g and maintained a capacity of 630 mAh/g after 74 cycles at 0.5 mA/cm2; even at 8 mA/cm2 it delivered more than 85% of its capacity. Its volumetric capacity is double that of carbon. The coulombic efficiency climbed from 77% in the first cycle to above 99.5% after 20 cycles, and retained that value.
The researchers synthesized the material by high energy ball-milling; EDX mapping indicated that Si was dispersed homogeneously in the MgO matrix.
The work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the US Department of Energy under Contract No. DE-AC02-05CH11231, under the Batteries for Advanced Transportation Technologies (BATT) Program subcontract # 6807148.
Wenchao Zhou, Shailesh Upreti, and M. Stanley Whittingham (2011a) Si/MgO/C composite material as anode for lithium-ion batteries (219th ECS Meeting)
Wenchao Zhou, Shailesh Upreti, M. Stanley Whittingham (2011b) High performance Si/MgO/graphite composite as the anode for lithium-ion batteries, Electrochemistry Communications, In Press, doi: 10.1016/j.elecom.2011.07.006