Significant Improvement of LiMn₂O₄ Cathode Capacity by Introducing Trace Ni During Rapid Microwave-induced Solution Combustion

Abstract

HRTEM image and cycle curves at 5C and 20C of LiMn 1.975 Ni 0.025 O 4 sampleLiMn 2 O 4 cathodes are prepared by a rapid microwave-induced solution combustion method. Their initial discharge capacity is significantly improved by introducing trace Ni. For example, the LiMn 1.975 Ni 0.025 O 4 (LMNO-0.025) cathode releases an initial discharge capacity of 134.1 mAh g −1 at 1 C, even 144.5 mAh g −1 at 0.5 C, which is far higher than of the pristine LiMn 2 O 4 cathode (119.7 mAh g −1 at 1 C) and close to its theoretical capacity of 148.2 mAh g −1 . After 1000 cycles, the capacity retention of the LMNO-0.025 sample reaches 56.53% at 1 C, and it can be presented the higher capacity retentions of 66.79% at 5 C and 66.89% at 20 C. The robust structure stability proved by XRD, SEM and HRTEM data, and the good kinetics testified by CV and EIS data of the Ni-doped material are responsible to improve the high-rate capability and long cycle properties.

Optimal design of LiMn2O4 for high-rate applications by means of citric acid aided route and microwave heating

“…Interestingly, the results of existing high-rate tests of LiMn2O4 synthesized in a similar way (microwave-assisted citric acid aided route) [46] are quite close to our data obtained without postheating and are significantly inferior to those attained for MW-2 and MW-4 samples, see Figure 5d. This clearly shows that MW post-heating is advantageous for improving the electrochemical performance of lithium-manganese spinels, i.e., apparently, small action greatly affects the properties of a material.…”

“…The same is true for LiMn2O4 obtained by means of a citric acid aided route and MW heating [44,45]. Only very recently, LiMn2O4 synthesized in this manner has been subjected to detailed electrochemical tests [46]. It appears, however, that in spite of quite similar particle size, its high-rate properties are much worse than those of a material made with the help of conventional thermal treatment [17,20].…”