This study presents a cobalt-free composite-structured cathode material, LiNi₀.₉₅Mn₀.₀₅O₂ (NM9505), with controlled lithium stoichiometry for sustainable lithium-ion batteries. The material is synthesized from hydroxide precursors with varying lithium content, leading to a composite structure consisting of a major layered phase and a minor rock salt (RS) phase. The Li-deficient NM9505 (x=0.95) exhibits superior electrochemical performance, including 90% first-cycle Coulombic efficiency, 90% capacity retention, and negligible voltage fade after 100 deep cycles. The key to this performance is the controlled lithium stoichiometry, which suppresses the RS-to-layered phase transformation and crystal growth, resulting in small-sized composites with low anisotropic lattice expansion/contraction during cycling. This structural design enhances the stability and cycling performance of the cathode, making it a promising candidate for Co-free cathodes in sustainable lithium-ion batteries. The study also highlights the role of lithium stoichiometry in tuning the structural and morphological properties of the cathode, offering a new route to stabilize Co-free cathodes through precise control of lithium content. The findings demonstrate that Li-deficient NM9505 provides a cost-effective and efficient strategy for developing high-performance, sustainable lithium-ion batteries.This study presents a cobalt-free composite-structured cathode material, LiNi₀.₉₅Mn₀.₀₅O₂ (NM9505), with controlled lithium stoichiometry for sustainable lithium-ion batteries. The material is synthesized from hydroxide precursors with varying lithium content, leading to a composite structure consisting of a major layered phase and a minor rock salt (RS) phase. The Li-deficient NM9505 (x=0.95) exhibits superior electrochemical performance, including 90% first-cycle Coulombic efficiency, 90% capacity retention, and negligible voltage fade after 100 deep cycles. The key to this performance is the controlled lithium stoichiometry, which suppresses the RS-to-layered phase transformation and crystal growth, resulting in small-sized composites with low anisotropic lattice expansion/contraction during cycling. This structural design enhances the stability and cycling performance of the cathode, making it a promising candidate for Co-free cathodes in sustainable lithium-ion batteries. The study also highlights the role of lithium stoichiometry in tuning the structural and morphological properties of the cathode, offering a new route to stabilize Co-free cathodes through precise control of lithium content. The findings demonstrate that Li-deficient NM9505 provides a cost-effective and efficient strategy for developing high-performance, sustainable lithium-ion batteries.