Inhibiting Mn Migration by Sb-Pinning Transition Metal Layers in Lithium-Rich Cathode Material for Stable High-Capacity Properties.

Abstract

Owing to the interacted anion and cation redox dynamics in Li2 MnO3 , the high energy density can be obtained for lithium-rich manganese-based layered transition metal (TM) oxide [Li1.2 Ni0.2 Mn0.6 O2 , LNMO]. However, irreversible migration of Mn ions and oxygen release during highly de-lithiation can destroy its layered structure, leading to voltage and capacity decline. Herein, non-TM antimony (Sb) is pinned to the TM layer of LNMO by a facile sol-gel method. High-resolution ex and in situ characterization technologies manifest that the introduction of trace Sb inhibits the migration of Mn ions, forming a more stable structure. Sb can impressively adjust the Mn-O interaction between anions and cations, beneficial to decrease the energy level of Mn 3d and O 2p orbitals and expand their band gap according to the theoretical calculation results. As a result, the discharge specific capacity and the energy density for SbLi1.2 [Ni0.2 Mn0.6 ]O2 (SLNMO) reaches as high as 301 mAh g-1 and 1019.6Wh kg-1 at 0.1 C, respectively. Moreover, the voltage decay is reduced by 419.8mV compared with LNMO. The regulative interaction between Mn 3d and isolated O 2p bands provides an accurate guidance for solving electrochemical performance deficiencies of lithium-rich manganese-based cathode oxide.