  Li-ion rechargeable batteries have enabled the wireless revolution
transforming global communication. Future challenges, however, demands
distributed energy supply at a level that is not feasible with the current
energy-storage technology. New materials, capable of providing higher energy
density are needed. Here we report a new class of lithium-ion batteries based
on a graphene ink anode and a lithium iron phosphate cathode. By carefully
balancing the cell composition and suppressing the initial irreversible
capacity of the anode, we demonstrate an optimal battery performance in terms
of specific capacity, i.e. 165 mAhg-1, estimated energy density of about 190
Whkg-1 and life, with a stable operation for over 80 charge-discharge cycles.
We link these unique properties to the graphene nanoflake anode displaying
crystalline order and high uptake of lithium at the edges, as well as to its
structural and morphological optimization in relation to the overall battery
composition. Our approach, compatible with any printing technologies, is cheap
and scalable and opens up new opportunities for the development of
high-capacity Li-ion batteries.
