Construction of V2O5 buffer layer to optimize interfacial stability of NCA cathode materials and cycle stability of lithium-ion batteries

Abstract

The nickel-rich layered cathode material LiNi_0.80Co_0.15Al_0.05O₂ (NCA) is widely used in lithium-ion batteries because of its reversible capacity and high energy density. However, the interfacial reactions and structural phase transitions arising from its high voltage can limit the cycle life and need to be addressed. In this work, a series of V₂O₅ coated NCA materials is prepared, the introduction of the V₂O₅ coating layer does not impact the structure of NCA or the electrochemical reactions. Owing to its excellent stability, V₂O₅ provides a stable shielding layer that prevents the electrolyte from attacking the cathode material. Thus, the generation of Ni²⁺ is inhibited, reducing cation mixing during the cycling, slowing down the phase change behavior, and thus improving the operating voltage and cycling stability of NCA cathode material. The V₂O₅@NCA cathode material with NCA to V₂O₅ precursor molar ratio of 1:0.002 during preparation (SV2) showed the best cycling performance among these materials. At 25 °C and 1 C, the cycle retention rate of the SV2 sample, after 200 cycles (88.39%), is about 22% higher than that of the NCA sample. This work provides an effective strategy to improve the cycling stability of Ni-rich cathode materials at high voltages.