<p>This work reports a novel synthesis of two-dimensional LiNiO₂ nanosheets using NiCO₃ nanosheets as a precursor. The as-prepared LiNiO₂ nanosheets, evaluated as a cathode active material for lithium-ion batteries, demonstrate exceptional electrochemical performance. The material delivers a high initial discharge capacity of 207.7 mAh g^-1 at 0.5 C, coupled with outstanding cycling stability (90.3% capacity retention after 200 cycles, referenced to the 20th cycle charge capacity). Remarkable rate capability is achieved, retaining 69.7 mAh g^-1 even at a high rate of 5 C. Furthermore, the nanosheets exhibit rapid lithium-ion diffusion kinetics, with a calculated diffusion coefficient of 3.6 × 10^-10 cm² s^-1, highlighting their structural and electrochemical advantages. This study not only introduces a unique precursor-driven synthesis route for LiNiO₂ but also underscores its potential as a high-performance cathode material for advanced energy storage systems.</p>