Naichao Li

A High-Rate, High-Capacity, Nanostructured Sn-Based Anode Prepared Using Sol-Gel Template Synthesis

Li-ion battery anodes derived from oxides of tin have recently received considerable interest because in principle they can store over twice as much Li as graphite. However, large volume changes occur when Li is inserted and removed from these Sn-based materials, and this causes internal damage to the electrode, resulting in loss of capacity and rechargability. We describe here a new nanostructured SnO 2 -based electrode that has extraordinary rate capabilities, can deliver very high capacities (e.g., >700 mAh g -1 at 8 C rate), and still retain the ability to be discharged and recharged through as many as 1400 cycles. These electrodes, prepared via the template method, consist of monodisperse 110 nm diam SnO 2 nanofibers protruding from a current-collector surface like the bristles of a brush.

Rate Capabilities of Nanostructured LiMn2 O 4 Electrodes in Aqueous Electrolyte

Nanostructured LiMn 2 O 4 electrodes consisting of LiMn 2 O 4 nanotubules that protrude from a current collector surface like the bristles of a brush were prepared using the template method. The rate capabilities of these nanostructured electrodes were investigated at the 4 V (vs. Li/Li + ) potential plateau in aqueous LiNO 3 electrolyte. Rate capability improved with decreasing wall thickness of the tubules which formed the electrode. This result is in agreement with our prior investigations of template-synthesized electrode materials which showed that rate capabilities improve with decreasing distance for Li + transport in the solid state. The rate capabilities of electrodes prepared from the smallest-wall-thickness tubules are extraordinary; these electrodes can be cycled at C rates as high as 109 C. In addition, these investigations suggest that the poor cycling performance observed in prior studies of this electrode/electrolyte system results from unwanted oxidation of water during the charging process. By controlling the charge rate and the dimensions of the nanotubules making up the template-synthesized cathodes, this unwanted side reaction can he eliminated and good cycle life is observed. These data show that the nanostructured electrodes offer a unique advantage to this particular electrode/electrolyte system.

A High‐Rate, High‐Capacity, Nanostructured Tin Oxide Electrode

Recently, battery anodes derived from oxides of tin have been of considerable interest because they can, in principle, store more than twice as much as graphite. However, large volume changes occur when is inserted and removed from these materials, and this causes internal damage to the electrode resulting in loss of capacity and rechargeability. We describe here a nanostructured electrode that has extraordinary rate capabilities, can deliver very high capacities , and still retain the ability to be discharged and recharged for as many as 800 cycles. These electrodes, prepared via the template method, consist of monodisperse nanofibers protruding from a current‐collector surface like the bristles of a brush. The dramatically improved rate and cycling performance are related to the small size of the nanofibers that make up the electrode and the small domain size of the grains within the nanofibers. ©2000 The Electrochemical Society

A Nanostructured Honeycomb Carbon Anode

We have been investigating a general template-based method for preparing nanostructured Li-ion battery electrodes. We have shown that these nanostructured electrodes have improved rate capabilities relative to thin-film control electrodes composed of the same material. Improved rate capabilities are observed because the high-rate capacity obtained from Li + -insertion materials is limited by slow solid-state Li + transport in the electrode material, and the nanostructured electrodes decrease the distance that Li + must diffuse in the solid state. We describe here an alternative type of nanostructured electrode material, a honeycomb carbon anode that consists of a thin carbon film containing an ordered array of monodispersed nanoscopic pores. This honeycomb carbon anode shows a low-rate discharge capacity of 325 mA hg - 1 , close to that of graphite. At high discharge rates (10 C), the honeycomb anode, delivers 50 times the capacity of a thin-film control anode that did not contain the honeycomb of nanopores. Improved rate capabilities are obtained because penetration of solvent and Li + electrolyte into the pore structure of the honeycomb anode insures that the distance Li + must diffuse in the solid state is smaller than in the thin-film control electrode.