Pristine and yttrium-doped LiNi_0.5-xY_xMn_1.5O₄ spinel powders (x=0, 0.005, 0.01, 0.02, 0.04) were synthesized by a facile solid-state method. The effect of yttrium doping content on the electrochemical properties of LiNi_0.5-xY_xMn_1.5O₄ was investigated by using half-cells paired with lithium metal and full-cells paired with graphite. XRD and FT-IR analysis shows that the cation disordering degree (Mn³⁺ content) first increase (x≤0.02) and then decrease with Y doping content and the Y doping can effectively inhibit the formation of Li_xNi_1-xO impurity phase. Electrochemical results show that in half-cells, appropriate Y doping (x=0.01) exhibits optimal rate capability and cycling stability of LiNi_0.5Mn_1.5O₄ cathode material, due to higher phase purity, enlarged lattice parameter, higher disordering degree, higher structural stability by introducing Y-O bond, lower charge transfer resistance and higher lithium ion diffusion coefficient, although the 0.2 C discharge capacity is slightly lower than pristine LiNi_0.5Mn_1.5O₄. However, in full-cells, the yttrium doping effect on the improvement of battery performance is not obvious as half-cells.