Quenching-Induced Defects Liberate the Latent Reversible Capacity of Lithium Titanate Anode.

Interest in defect engineering for lithium-ion battery (LIB) materials has been sparked by its ability to tailor electrical conductivity and introduce extra active sites for electrochemical reactions. However, harvesting excessive intrinsic defects in the bulk of the electrodes rather than near their surface remains a long-standing challenge. Here we demonstrate a versatile strategy of quenching, which is exercised in lithium titanate (Li4 Ti5 O12 , LTO), a renowned anode for LIBs, to achieve off-stoichiometry in the interior region. In-situ synchrotron analysis and atomic-resolution microscopy reveal the enriched oxygen vacancies and cation redistribution after ice-water quenching, which can facilitate the native unextractable Li ions to participate in reversible cycling. The fabricated LTO anode delivers a sustained capacity of 202 mAh g-1 in the 1.0-2.5 V range with excellent rate capability, and overcomes the poor cycling stability seen in conventional defective electrodes. We also demonstrate the feasibility of tuning the degree of structural defectiveness via quenching agents, which can open up an intriguing avenue of research to harness the intrinsic defects for improving the energy density of rechargeable batteries. This article is protected by copyright. All rights reserved.