Impact of Nickel and Manganese Content on the Electrochemical Properties of Li1.13Mn0.54-X Ni0.27+X Co0.06O2 As Lithium Ion Battery Cathodes

Abstract

Introduction In recent years, Li-rich, Mn-based Li[Li1-x-y Me x Mn y ]O2 (Me=Co, Fe, Cr, Ni, etc.) cathode materials have received world-wide attention for their high capacity (>250 mAhg-1) when operating at high voltage [1]. However, the cathode materials still suffer from poor rate capability and gradual capacity degradation during cycling, accompanied with hysteresis and voltage fade [2]. In order to overcome those issues, extensive studies have been performed to improve the electrochemical performance of Li[Li1-x-yMexMny]O2 cathode materials. Among all the factors investigated, it was found that Mn/Ni content of Li[Li1-x-yMexMny]O2 could be an important factor that limits the rate capability and influences the capacity/voltage fade [3]. As such, in this paper, we study the effects of Mn/Ni content of Li1.13Mn0.54-x Ni0.27+x Co0.06O2on structure, morphology, rate capability, capacity degradation and voltage fade during cycling. Fig.1. The cycle performance of Li1.13Mn0.54-x Ni0.27+x Co0.06O2in the voltage range of 2.5-4.6 V at 1.0 C after three formation cycles in the voltage of 2.0-4.8 V at 0.1 C, (a) discharge capacity and (b) median voltage of discharge Results and Discussion Fig. 1 shows the capacity cycling performance (Fig. 1 (a)) and median voltage of discharge (Fig. 1 (b) of Li1.13Mn0.54-x Ni0.27+x Co0.06O2 (x=0, 0.02, 0.04, 0.06) in the voltage range of 2.5-4.6 V at 1.0 C after three formation cycles in the voltage of 2.0-4.8 V at 0.1 C. As shown in Fig. 1(a), it can be seen that initial discharge capacities decrease with x value increasing in the voltage of 2.0-4.8 V at 0.1 C ,during the formation cycles. Meanwhile, Li1.13Mn0.54-x Ni0.27+x Co0.06O2 (x=0, 0.02, 0.04, 0.06) delivers the initial discharge capacity of 181.0, 178.4, 157.6, 142.7 mAhg-1 in the voltage of 2.5-4.6 V at 1.0 C and capacity retention are 75.0, 87.2, 90.0 and 88.9% of an initial discharge capacity after 200 cycles, respectively. Fig. 1(b) shows the variation of median voltage of discharge of Li1.13Mn0.54-x Ni0.27+x Co0.06O2 (x=0, 0.02, 0.04, 0.06) over 200 cycles. It is noted that Li1.13Mn0.54-x Ni0.27+x Co0.06O2 shows much smaller voltage fade with x value increasing. Our results indicate that the Li1.13Mn0.54-x Ni0.27+x Co0.06O2 with lower Mn content and higher Ni content demonstrates much better electrochemical performance with high capacity retention and small voltage fade comparing to Li1.13Mn0.54Ni0.27Co0.06O2.