Cathode materials with significantly higher specific capacities than what is currently available are critical to meeting the DOEs goals of 350 Wh/kg and 750 Wh/L at the cell-level. New materials that are capable of accommodating more than one lithium ion per transition metal can have a transformational impact on the energy density. Manganese-based cathode compositions, while being low cost and environmentally friendly, are also capable of multi-electron transfer. The proposed Phase I effort aims to advance the state the art by demonstrating manganese-based cathode materials with ultrahigh capacity and cycling stability. The objective of the Phase 1 program is to develop and demonstrate at the pouch cell level, a new high energy density cathode material that is capable of meeting DOEs target of 350 Wh/kg cell-level energy density. Building on previous work, the Phase I feasibility effort will show that novel ionic substitutions in the crystal structure of manganese-based cathode materials can lead to a high capacity cathode material that is stable to long term cycling. Stabilized manganese based cathode materials will be synthesized in gram quantities and characterized for composition, phase purity, particle size, surface area and thermal stability. Select batches with the desired particle characteristics will then be tested for electrochemical properties (e.g., specific capacity, rate capability and cycle life) in a coin cell format. A large batch of the most promising candidate material will be produced to demonstrate scalability, and the powder will be used to fabricate and test pouch cells with a capacity of at least 200 mAh. The market for lithium ion batteries is growing rapidly driven by the growth in electric vehicles and grid-based storage. The availability of low cost and high performance battery materials, particularly cathode powder, is key to enabling battery manufacturing infrastructure in our country. The proposed program, when successfully implemented, will lead to rechargeable lithium-ion batteries with significantly higher energy density than what is currently possible today.