I'm not one for the Lithium Ion scene but many of those devices limit how low your build or atomizer can be. For example most won't let you build under .30ohms and if you go even that low your available wattage scaling is near to nothing. I hear the CF Aspire Sub-Ohm Lithium battery mod is pretty impressive, and supports low ohms. For a box mod that is USB chargeable the Jelly Fish is also pretty cool, but I believe it has 18650s in it.