Fig. 1. XRD patterns of Li_1.2M_yV_3−yO₈ obtained by solid state reaction: (a) Li_1.2V₃O₈ (undoped), (b) M=Mo, y=0.10, (c) M=Mo, y=0.25 (d) M=W, y=0.10, (e) M=W, y=0.25.

Fig. 2. Lattice parameters of Li_1.2M_yV_3−yO₈: (a) M=Mo, (b) M=W.

Fig. 3. Discharge curves at C/8 rate for Li_n+xMo_yV_3−yO₈, n=f(y) (see text for discussion), (0) Li_1+xV₃O₈ (undoped), (1) y=0.05, (2) y=0.10, (3) y=0.15, (4) y=0.20, (5) y=0.25.

Fig. 4. OCP plot (left coordinate system) and cyclic voltammograms at 0.01 mV s⁻¹ scan rate (right coordinate system) for Li_n+xM_yV_3−yO₈, (a) y=0.25, (b) 0.20≤y<0.25, (c) y<0.20.

Fig. 5. Possible sites in the Li_1+xV₃O₈-like host structure: (a) candidate tetrahedral sites for low lithiated oxide, (b) candidate octahedral sites in high lithiated defect rock salt structure. Lithium positions are labeled as in [4]. (See text for discussion).

Fig. 6. XRD patterns of Li_0.92+xM_0.20V_2.80O₈ obtained by electrochemical lithium insertion: (a) Li_1.2V₃O₈ (untreated), (b) x=1.40, (c) x=2.70.

Fig. 7. Lattice parameters of electrochemically lithiated Li_0.92+xM_0.20V_2.80O₈.

Fig. 8. Possible routes for phase transition from low lithiated to high lithiated Li_n+xMo_yV_3−yO₈: (route I) y<0.20; (route II) 0.20≤y<0.25.

Fig. 9. Discharge curves at C/8 rate and OCP plots for Li_n+xW_yV_3−yO₈, n=f(y) (see text for discussion), (squares) OCP for y=0.05, (circles) OCP for y=0.25, (0) galvanostatic discharge, y=0, (1) y=0.05, (2) y=0.15, (3) y=0.20, (4) y=0.25.

Table 1. Lithium insertion limits for Li_nM_y⁺⁶V_3−yO₈, where M⁺⁶=Mo, W; n=1±z