if they are li-ion cells regulated down to 3.0v, capacity is likely to be small indeed. Your best bet is likely to be choosing a bulb that is appropriate for either one or two li-ion cells (nominal 3.6 or 7.2v), and foregoing the "3.0v li-ion" concept. LiFePO4cells, nominally 3.2v, also have limited capacity compared to LiCo and even IMR cells.