Exploring the action of rare-earth yttrium dopant on enhancing electrochemical performance of LiNi_0.5Mn_1.5O₄ material

Spinel LiNi_0.5Mn_1.5O₄ (LNMO) has been considered as an appropriate cathode material for lithium-ion batteries because of its non-toxicity, high voltage platform and high energy density. Whereas, an occurrence of Jahn–Teller distortion in disordered structure of spinel is inevitable due to the presence of Mn³⁺ ion and the cycling behavior is inadequate. Hence, a citric acid-aided method is used to address above question by adding yttrium dopant. A series of characterization methods are measured. Characterization results display that Y³⁺ doping decreases lattice parameter and Mn³⁺ content, and results in a decrease in grain size for Y-doped LNMO samples. These changes by Y³⁺ doping can reduce the degree of electrochemical polarization and enhance insertion and extraction reaction of Li⁺. On the other hand, the changes can also improve structural stability and retard the Jahn–Teller distortion. Therefore, the effect of Y³⁺ doping on crystalline structure, grain morphology and Mn³⁺ concentration is revealed and displayed a positive effect on enhancing rate performance and cycling stability of LNMO. Compared to other three LNMO samples, LiNi_0.49Mn_1.49Y_0.02O₄ LNMO sample exhibits best rate capacity and delivers highest discharge retention rate of 98.8% after 100 cycles at 1 C. Our research demonstrates that yttrium doping to enhance the electrochemical properties of LiNi_0.5Mn_1.5O₄ cathode materials is an efficacious route.