Enhanced rate performance and high current cycle stability of LiNi_0.8Co_0.1Mn_0.1O₂ by sodium doping

Abstract

Sodium ions have been successfully doped into LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) by solid phase method. The influences of Na doping on the electrochemical properties of the electrode at high current intensities were studied. The experimental results show that 3% Na modified LiNi 0.8 Co 0.1 Mn 0.1 O 2 has superior rate performance and cycling behavior due to the cation mixing is suppressed and the structural stability is enhanced by Na doping. The capacity retention of Li 0.97 Na 0.03 Ni 0.8 Co 0.1 Mn 0.1 O 2 is 64.33% after 100th cycles at 10 C (1 C = 200 mA · g –1 ) in the potential range from 2.8 V to 4.3 V, which is greatly higher than the pristine NCM (only 35.01%). Li 0.97 Na 0.03 Ni 0.8 Co 0.1 Mn 0.1 O 2 also shows excellent rate performance of 140.5 mAh · g –1 at 10 C, and the discharge capacity of 3% Na-NCM is higher than that of the pristine NCM when the current intensity is returned from 10 C to 0.5 C. The analysis of the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements confirm that the Na doping plays an important role in inhibiting the electrochemical polarization of LiNi 0.8 Co 0.1 Mn 0.1 O 2 and improving the diffusion of lithium ions.