This paper describes the possible evolution of Li-ion technology, and evaluates the expected improvements, arising from new materials to cell technology. New active materials under investigation and electrode process improvements may allow an ultimate final energy density of more than 500Wh/l and 200Wh/kg, in the next 5–10 years, while maintaining sufficient power densities. A new rechargeable battery technology cannot be foreseen today that surpasses this. The possible use of small fuel cells is also discussed. The only solution would be direct methanol fuel cell (DMFC) technology, providing that the remaining important technological issues are solved. The association with a rechargeable battery could provide an optimised energy + power, hybrid power source. Several simulated comparisons for small- to medium-sized power sources are described, between fuel cells and batteries. Hybrid Li-ion/DMFC is a good option for systems larger than 1kWh. The hybrid concept of high-energy–low-power primary lithium (as the fuel) with high-power Li-ion (as the cell stack) is an already available, cost effective solution where long run times are required.