Enhanced Electrochemical Performance in Ni‐Doped LiMn 2 O 4 ‐Based Composite Cathodes for Lithium‐Ion Batteries

High‐voltage and high‐performance Ni‐doped LiMn 2 O 4 ‐basedcomposite cathodes have been obtained from the nominal formula of Li 2 Mn 1‐ x Ni x SiO 4 , synthesized by using a citric acid‐assisted sol‐gel method. The spinel Li(Mn,Ni) 2 O 4 and layered Li 2 SiO 3 coexist in the composites with x =0 and 0.05, whereas the materials with x =0.15 and 0.25 consist of Li(Mn,Ni) 2 O 4 , Li 2 SiO 3 and layered LiNiO 2 ; at x ≥ 0.35, the impurity phases of NiO and Ni 6 MnO 8 are detected. A significant improvement in discharge capacity and rate performance of the materials has been caused by the simultaneous existence of LiNiO 2 and Li 2 SiO 3 . The composite with x =0.25 givesa very high initial discharge capacity of 168 mAh g −1 in the potential range of 3–5 V and exhibits an excellent rate performance. Our study shows that the composites consisting of Li(Mn , Ni) 2 O 4 , Li 2 SiO 3 , and LiNiO 2 may be promising candidates for high‐voltage and high‐performance lithium‐ion batteries.