Ultra-Stable Performance of Ni-Rich Layered Oxide Cathodes for Lithium-Ion Batteries Using Ionic Liquid Electrolyte

摘要

High energy density lithium-ion batteries (LIBs) have continually been of great research interest amplified by the exponentially growing demand for electric vehicles. Among the investigated systems, nickel-rich transition metal oxides appear very promising owing to their high specific capacity, and low cobalt content, according to necessity of reducing the cobalt proportion in LIB cathodes due to its severe shortage and strong environmental and ecological concerns. However, the increased nickel content also introduces previously overcome challenges of poor capacity retention and thermal stability due to the vulnerability of the nickel rich oxide towards interfacial side reactions. Herein, a low volatility and non-flammable ionic liquid-based (IL) electrolyte consisting of 0.8Pyr_(14)FSI-0.2LiTFSI is employed to overcome those challenges faced by a Ni-rich LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2 positive electrode. The cathode exhibits remarkable electrochemical performance in half-cell configuration, delivering a specific capacity of approximately 200 mAh g~(-1) and practically no capacity fading after 100 cycles at 0.1C at room temperature. After 600 cycles at 0.5C the cathode has an outstanding capacity retention of 97%, which is substantially higher than with the conventional organic carbonate-based electrolyte used for reference, attributed to a much more stable electrode-electrolyte interfacial layer. Even at elevated temperature (40°C) the LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2 in combination with the IL electrolyte offers a specific capacity of more than 200 mAh g~(-1) as well as a capacity retention around 99% after 100 cycles at 0.5C. To the best of our knowledge these results exceed the state-of-the-art performance reported for any Ni-rich positive electrode.