Design of Surface Doping for Mitigating Transition Metal Dissolution in LiNi_0.5 Mn_1.5 O₄ Nanoparticles

In lithium-ion batteries (LIBs) comprising spinel cathode materials, the dissolution of transition metals (TMs) in the cathodes causes severe cyclic degradation. We investigate the origin and mechanism of surface TM dissolution in high-voltage spinel oxide (LiNi_0.5 Mn_1.5 O₄ ) nanoparticles to find a practical method for its mitigation. Atomic structures of the LiNi_0.5 Mn_1.5 O₄ surfaces are developed, and the electronic structures are investigated by first-principles calculations. The results indicate that titanium is a promising dopant for forming a more stable surface structure by reinforcing metal-oxygen bonds in LiNi_0.5 Mn_1.5 O₄ . Experimentally synthesized LiNi_0.5 Mn_1.5 O₄ with titanium surface doping exhibits improved electrochemical performance by suppressing undesirable TM dissolution during cycles. The theoretical prediction and experimental validation presented here suggest a viable method to suppress TM dissolution in LiNi_0.5 Mn_1.5 O₄ .