Redox shuttle is a promising mechanism for intrinsic overcharge protection in lithium-ion cells and batteries. Two lithium borate cluster salts are reported to function as both the main salt for a nonaqueous electrolyte and the redox shuttle for overcharge protection. Lithium borate cluster salts with a tunable redox potential are promising candidates for overcharge protection for most positive electrodes in state-of-the-art lithium-ion cells. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3299251] All rights reserved.