This paper presents research on solid-state thin-film lithium and lithium-ion batteries developed at Oak Ridge National Laboratory over the past decade. These batteries, less than 15 micrometers thick, have potential applications in consumer and medical products and serve as research tools for studying lithium intercalation compounds. The batteries consist of crystalline or nanocrystalline oxide-based lithium intercalation compounds as cathodes, lithium metal or inorganic compounds as anodes, and a glassy lithium phosphorus oxynitride ('Lipon') electrolyte. Crystalline LiCoO₂ cathodes deliver up to 30% of their maximum capacity between 4.2 and 3 V at 10 mA/cm² discharge currents. Thin films of crystalline lithium manganese oxide (Li₁+xMn₂−yO₄) exhibit significant capacity at 5 V and, depending on deposition, at 4.6 V due to manganese deficiency and lithium excess. The 5-V plateau is attributed to oxidation of Mn ions to higher valence states. The gap between discharge-charge curves of nanocrystalline Li₁+xMn₂−yO₄ cathodes is due to true hysteresis, not kinetic hindrance. Extended cycling at 25 and 100°C leads to grain growth and evolution of charge-discharge profiles toward those of well-crystallized films. Lithium-ion cells with Sn₃N₄ and Zn₃N₂ anodes show improved performance compared to lithium anodes. Lithium-free cells, with a Cu current collector and lithium plated on the cathode during initial charge, exhibit performance similar to lithium anode cells. These cells can tolerate solder reflow conditions up to 250–260°C. Nanocrystalline Li₁+xMn₂−yO₄ films exhibit hysteresis in the 3-V spinel-tetragonal two-phase region. The hysteresis is due to phase boundary motion at the cathode-electrolyte interface. Doping with Ni²+ ions improves the capacity above 4.5 V in Li₁+xMn₂−yO₄ films. The paper discusses the performance, structure, and electrochemical properties of thin-film lithium and lithium-ion batteries, and their potential applications in consumer and medical products. Manufacturing scale-up is underway, with potential applications including implantable medical devices, CMOS-based integrated circuits, and RFID tags. The batteries can be integrated into devices by direct fabrication on IC packages or chips. The paper concludes with a discussion of the status of manufacturing scale-up and future research directions.This paper presents research on solid-state thin-film lithium and lithium-ion batteries developed at Oak Ridge National Laboratory over the past decade. These batteries, less than 15 micrometers thick, have potential applications in consumer and medical products and serve as research tools for studying lithium intercalation compounds. The batteries consist of crystalline or nanocrystalline oxide-based lithium intercalation compounds as cathodes, lithium metal or inorganic compounds as anodes, and a glassy lithium phosphorus oxynitride ('Lipon') electrolyte. Crystalline LiCoO₂ cathodes deliver up to 30% of their maximum capacity between 4.2 and 3 V at 10 mA/cm² discharge currents. Thin films of crystalline lithium manganese oxide (Li₁+xMn₂−yO₄) exhibit significant capacity at 5 V and, depending on deposition, at 4.6 V due to manganese deficiency and lithium excess. The 5-V plateau is attributed to oxidation of Mn ions to higher valence states. The gap between discharge-charge curves of nanocrystalline Li₁+xMn₂−yO₄ cathodes is due to true hysteresis, not kinetic hindrance. Extended cycling at 25 and 100°C leads to grain growth and evolution of charge-discharge profiles toward those of well-crystallized films. Lithium-ion cells with Sn₃N₄ and Zn₃N₂ anodes show improved performance compared to lithium anodes. Lithium-free cells, with a Cu current collector and lithium plated on the cathode during initial charge, exhibit performance similar to lithium anode cells. These cells can tolerate solder reflow conditions up to 250–260°C. Nanocrystalline Li₁+xMn₂−yO₄ films exhibit hysteresis in the 3-V spinel-tetragonal two-phase region. The hysteresis is due to phase boundary motion at the cathode-electrolyte interface. Doping with Ni²+ ions improves the capacity above 4.5 V in Li₁+xMn₂−yO₄ films. The paper discusses the performance, structure, and electrochemical properties of thin-film lithium and lithium-ion batteries, and their potential applications in consumer and medical products. Manufacturing scale-up is underway, with potential applications including implantable medical devices, CMOS-based integrated circuits, and RFID tags. The batteries can be integrated into devices by direct fabrication on IC packages or chips. The paper concludes with a discussion of the status of manufacturing scale-up and future research directions.