Enhancing cycling stability of Li-rich Mn-based cathode materials via cyano functional additives†

Abstract

Li-rich Mn-based cathode materials (LRMs) have garnered considerable interest for their high specific capacity. Nevertheless, the elevated operating voltage window presents a great hurdle to the high-voltage tolerance of the conventional electrolytes, and the induced issues such as rapid capacity and structure degradation also further impede their industrial application. In this regard, an efficient method to alleviate this problem is proposed via a cyano functional additive. By introducing the trimethylsilyl cyanide (TMS) additive into a carbonate electrolyte to construct a complex with TM–CN bonds on the cathode surface and form a low-impedance and durable cathode/electrolyte interphase (CEI), both electrolyte decomposition and cathode degradation are suppressed effectively. Moreover, harmful substances are also removed through the reaction between TMS and HF to purify the electrolyte. Therefore, the electrochemical performance of the LRM cathode is enhanced with a discharge capacity of 224 mA h g⁻¹ after 200 cycles at 1C. A high discharge capacity of 227 mA h g⁻¹ is also achieved after 50 cycles at 0.5C under a high mass loading of 13 mg cm⁻². This work presents a new path to develop high-voltage electrolytes for LRM cathodes.