Spherical LiMn 0.792 Fe 0.198 Mg 0.010 PO 4 nanocrystals, which are highly dispersed and encapsulated within the interstices of supergrowth (single-walled) carbon nanotubes (SGCNTs), were successfully synthesized by in situ material processing technology called "ultra-centrifuging (UC) treatment". TEM images of these LiMn 0.792 Fe 0.198 Mg 0.010 PO 4 /SGCNT composites suggest the direct attachment of the LiMn 0.792 Fe 0.198 Mg 0.010 PO 4 nanocrystals (10-40 nm) onto the surface of highly conductive SGCNTs. Mgdoping brought out 10% increase of Li + capacity in Mn sites with 200% increase of Li + diffusivity and 50% decrease of electrical resistance owing to such peculiar "nano-nano LiMn 0.792 Fe 0.198 Mg 0.010 PO 4 /SGCNT composites". The synthesized LiMn 0.792 Fe 0.198 Mg 0.010 PO 4 /SGCNT composites overcome the inherent restrictions of one-dimensional diffusion and deliver a high electrochemical capacity density of ca. 54 mA h g À1 per composite (corresponding to 77 mA h g À1 per pure LiMn 0.792 Fe 0.198 Mg 0.010 PO 4 ) at a high rate of 50 C, while showing excellent cycle life, retaining 84% of the initial capacity over 3000 cycles.

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