This chapter focuses on a description of a novel UNCD film-based technology enabling a new generation of Li-ion batteries (LIB) with orders of magnitude longer stable specific capacity vs. charge/discharge cycles and safer performance than current devices, to power a new generation of miniaturized defibrillators/pacemakers to improve the quality of life of people receiving them.The UNCD film technology provides three new key components of the LIB, namely: 1) Electrically conductive Nitrogen atoms-grain boundary incorporated ultrananocrystalline diamond (N-UNCD) films encapsulating natural graphite (NG)/copper composite LIB anodes, providing order of magnitude superior cycle performance and capacity retention than for NG/Cu anodes (the N-UNCD layer suppresses reactions of NG with the electrolyte and the development of insulating solid-electrolyte-interphase (SEI) on the anode, which retards anode conductivity and induces stresses, leading to cracks in the NG particles inducing loss of contact between them); 2) UNCD-coated Si-based membranes with orders of magnitude higher resistance to chemical attack than membranes in current LIBs; and 3) UNCD coatings for the inner walls of battery cases to enable use of less expensive case materials than current ones.