Rescue the cycle life of LiNi0.5Mn1.5O4 cathode on high voltage via glyceryl triacetate as the multifunction additive

Abstract

The poor cyclic stability is the key point to restricting the commercial application of LNi0.5Mn1.5O4-based lithium-ion batteries (LNMO-based LIBs) on high voltage (5 V-class). Once the working voltage is over 4.3 V, the parasitic reactions on the LNMO interphase will be the trigger for a series of problems such as the continuous decomposition of electrolytes and dissolution of transition metal ions. The glyceryl triacetate (GT) has been used as a functional additive to reconstruct a cathode electrolyte interphase (CEI) film to suppress the parasitic reactions and safeguard the LNMO structure. Compared to the influence of GT and propionic anhydride (PA) on the electrochemical performance of LNMO on high voltage, the LNMO/Li cell with GT exhibits exciting discharge capacity retention of 84.9 % compared with PA (17.6 %) and base electrolyte (BE, 8.6 %) after 500 cycles at 1C. The LNMO/Li cell with GT also has a remarkable rate performance in which capacity retention of 5C/2C is 85.7%, higher than 0.5 wt% PA (75.5%) and BE (62.1%). By characterizations, it is reasoningly demonstrated that the GT not only can be preferentially oxidized to form a robust CEI film on the LNMO surface to prevent the parasitic reaction but also rapidly capture the free transition metal ions and bind trace H2O in the electrolyte to improve the stability of LIBs. Simultaneously, the electrons from the carboxyl group of GT occupy the d-orbital of transition metal from LNMO, further effectively reducing the activity of LNMO. Particularly, the glycerol generated by the reaction of GT with H2O can effectively capture HF, H2O, and other small molecules under hydrogen-bond interaction, thereby improving the stability of LNMO LIBs.