Well-dispersed Si nanocrystals with sizes of approximately 5, 10, and 20 nm were prepared in reverse micelles at high pressure and 380°C and investigated as anode materials for lithium batteries. The 10 nm sized nanocrystals show a first charge capacity y of 3380 mAhg -1 and the highest capacity retention of 81 % after 40 cycles, which can be increased to 96% by carbon coating (see picture). "Chemical Equation Presented".