Lithium batteries with hybrid cathodes of Ag2V4O11 and CFx have been developed that combine the best features of both cathode components. They can offer power density and energy density that are competitive with or superior to other developed battery chemistries, along with the stability and reliability needed for implantable medical applications. More than 100,000 have been used in human implants since introduction in 1999. (c) 2005 Elsevier B.V. All rights reserved.