Submicron LiFe1−yMnyPO4 solid solutions prepared by mechanochemically assisted carbothermal reduction: The structure and properties

Structure and electrochemical properties of mixed transition-metal pyrophosphates Li2Fe1−yMnyP2O7 (0≤y≤1)

“…10), thus confirming that the Mn 2+ /Mn 3+ redox couple does not operate in the 2.0-4.3 V range, contrary to the mixed-metal olivines LiFe 1-ÀyMny PO 4 [21]. In the latter case, the average operating voltage for the Mn 2+ /Mn 3+ redox couple is 4.1 V; two two-phase plateaus are observed on the charge-discharge profiles of LiFe 1Ày Mn y PO 4 due to Fe 2+ /Fe 3+ and Mn 2+ /Mn 3+ redox couples [21].…”

“…However, the authors [22] suppose that the root is not only in the 'inductive effect', but in the stabilized edge-sharing local structural arrangement and the associated larger Gibbs free energy in charged state. Although similar upshifting of the order of 0.1 V has been noticed in the olivine LiFe 1Ày Mn y PO 4 system [21], but it is still more pronounced in the pyrophosphate system.…”

“…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.…”

Li3V2(PO4)3-coated Li1.17Ni0.2Co0.05Mn0.58O2 as the cathode materials with high rate capability for Lithium ion batteries

“…4a), which are assigned to the asymmetric stretching modes of M-O bonds in MO 6 octahedra and the O-M-O bending modes [32]. For LVP-coated samples (5 wt%), the bands at 1034 cm -1 are attributed to the symmetric non degenerate PO stretching modes (n 1 ) and the bands at 1090 and 1140 cm -1 are attributed to the symmetric, triply degenerate OPO bending modes (n 3 ) in terminal PO 4 units in Nasicon structure respectively [33][34][35][36][37][38]. The bands at 550 cm -1 shifts to lower wavenumber may due to the n 4 modes in PO 4 units.…”

Supervalent doping of LiFePO4 for enhanced electrochemical performance

“…Note that the position of the redox peaks on the dQ/dV plots well corresponds to those of pure LFP, LVP and LTP, evidencing that low degree of substitution and the composite formation do not noticeably influence voltage of the redox processes upon cycling. On the contrary, in the case of the olivine-type solid solutions, e.g., LiFe 1-y Mn y PO 4 [20,21].…”