The provision of efficient electron and ion transport is a critical issue in an exciting new group of materials based on lithium metal phosphates that are important as cathodes for lithium-ion batteries. Much interest centres on olivine-type LiFePO4, the most prominent member of this family(1). Whereas the one-dimensional lithium-ion mobility in this framework is high(2), the electronically insulating phosphate groups that benefit the voltage also isolate the redox centres within the lattice. The pristine compound is a very poor conductor (sigmasimilar to10(-9) S cm(-1)), thus limiting its electrochemical response. One approach to overcome this is to include conductive phases, increasing its capacity to near-theoretical values(3-6). There have also been attempts to alter the inherent conductivity of the lattice by doping it with a supervalent ion. Compositions were reported to be black p-type semiconductors with conductivities of similar to10(-2) S cm(-1) arising from minority Fe3+ hole carriers(7). Our results for doped (and undoped) LiMPO4 (M = Fe, Ni) show that a percolating nano-network of metal-rich phosphides are responsible for the enhanced conductivity. We believe our demonstration of non-carbonaceous-network grain-boundary conduction to be the first in these materials, and that it holds promise for other insulating phosphates.