“…Beyond tuning the operation voltage toward higher values, the mixed metal systems can activate the single-phase behavior during lithium (de) intercalation. Indeed, according to ex situ XRD analysis, a single-phase (solid-solution like) mechanism of (de) intercalation was established for Li 2 Fe 1Ày Mn y P 2 O 7 (this work), LiFe 1Ày Mn y PO 4 [21], LiCo 1Ày Fe y PO 4 [26], thus proving that doping is one of the most viable approach, besides nanosizing, to trigger such a mechanism. The highest discharge capacity is observed for the Li 2 Fe 0.75-Mn 0.25 P 2 O 7 composition (87 mA h g À1 at C/10), which is equal to its theoretical value delivered by the Fe 2+ /Fe 3+ redox couple.…”