Fused ring and linking groups effect on overcharge protection for lithium-ion batteries

The derivatives of 1,3-benzodioxan (DBBD1) and 1,4-benzodioxan (DBBD2) bearing two tert-butyl groups have been synthesized as new redox shuttle additives for overcharge protection of lithium-ion batteries. Both compounds exhibit a reversible redox wave over 4V vs Li/Li+ with better solubility in a commercial electrolyte (1.2 M LiPF6 dissolved in ethylene carbonate/ethyl methyl carbonate (EC/EMC 3/7) than the di-tert-butyl-substituted 1,4-dimethoxybenzene (DDB). The electrochemical stability of DBBD1 and DBBD2 was tested under charge/discharge cycles with 100% overcharge at each cycle in MCMB/LiFePO4 and Li4Ti5O12/LiFePO4 cells. DBBD2 shows significantly better performance than DBBD1 for both cell chemistries. The structural difference and reaction energies for decomposition have been studied by density functional calculations (C) 2010 Elsevier B.V. All rights reserved.