Effect of Cu Doping on the Structural and Electrochemical Performance of LiNi_1/3Co_1/3Mn_1/3O₂ Cathode Materials

Abstract

The structural and electrochemical performance of Cu-doped, Li[Ni_1/3−xCo_1/3 Mn_1/3Cu_x]O₂ (x = 0–0.1) cathode materials obtained by means of the sol-–gel method are discussed; we used critic acid as gels and spent mixed batteries as the raw materials. The effects of the sintering time, sintering temperature, and Cu doping ratio on the phase structure, morphology, and element composition and the behavior in a galvanostatical charge/discharge test have been systemically studied. The results show that the Cu-doped material exhibits better galvanostatic charge/discharge cycling performance. At 0.2 C, its original discharge specific capacity is 180.4 mAh g⁻¹ and its Coulomb efficiency is 90.3%. The Cu-doped material demonstrate an outstanding specific capacity at 0.2 C, 0.5 C, and 2.0 C. In comparison with the original capacities of 178 mAh g⁻¹, 159.5 mAh g⁻¹, and 119.4 mAh g⁻¹, the discharge capacity after 50 cycles is 160.8 mAh g⁻¹, 143.4 mAh g⁻¹, and 90.1 mAh g⁻¹, respectively. This obvious improvement relative to bare Li[Ni_1/3Co_1/3Mn_1/3]O₂ cathode materials arises from an enlarged Li layer spacing and a reduced degree of cation mixing. Therefore, Cu-doped cathode materials have obvious advantages in the field of lithium-ion batteries and their applications.