Improving the Electrochemical Performance of High-Nickel Cobalt-Free Cathode Coated with N-Doped Carbon Quantum Dots

Lithium-ion batteries (LIBs) are widely used as essential power sources for electric vehicles and energy storage systems. Among various cathode materials, Li[Ni_0.9Mn_0.1]O₂ (NM90) has gained significant attention for enhancing the performance of LIBs due to its high energy density and nontoxicity. However, increasing the nickel content introduces challenges, including structural instability and cation mixing. To address these issues, we propose a surface coating strategy using nitrogendoped carbon quantum dots (NCQDs). NCQDs provide high electrical conductivity and electrochemically active sites, so the NCQDs coating effectively enhanced both structural stability and electrical/ionic conductivity. The NCQDs were synthesized via a hydrothermal method, and NM90 were synthesized by co-precipitation. The fabricated NCQD/NM_5 electrode exhibited superior electrochemical properties, including a high initial capacity of 189.6 mAh/g, excellent rate performance, and an outstanding capacity retention of 81.5 % after 200 cycles in 1C. These superior results demonstrate that surface modification using the NCQDs strategy for Li[Ni_0.9Mn_0.1]O₂ cathode materials will contribute to the further development of cycle stability and ultrafast performance in energy storage systems.