An anode for a lithium battery comprises a graphene foam structure composed of multiple pores and pore walls and Si nanowires residing in the pores. The Si nanowires are formed in situ inside the pores. The pore walls comprise a 3D network of interconnected graphene planes or stacked graphene planes having an inter-plane spacing d002 from 0.3354 nm to 0.40 nm as measured by X-ray diffraction. The Si nanowires have a diameter from 2 nm to 100 nm and a length-to-diameter aspect ratio of at least 5 and the Si nanowires are in an amount from 0.5% to 99% by weight based on the total weight of the graphene foam and the Si nanowires combined.