The electrochemical insertion properties of the monoclinic Li3V2-xAlx(PO4)(3) (x=0.00, 0.10, 0.25, and 0.50) phases are presented. Aluminum incorporation induces a modification of the lithium insertion reaction, consistent with increased alkali-ion disorder within the Nasicon structure. Although the reversible specific capacity decreased with aluminum content, the results suggest that the substituted phases may offer some important beneficial properties. Preliminary cycle testing of prototype lithium-ion cells indicated encouraging performance with high material utilization and comparatively low discharge-capacity fade. The highest Al content phase demonstrated the best capacity retention, albeit at the expense of initial specific capacity.