Realizing Ultralong-Term Cyclicability of 5 Volt-Cathode-Material Graphite Flakes by Uniformly Comodified TiO2/Carbon Layer Inducing Stable Cathode-Electrolyte Interphase.

Abstract

A common issue the high-voltage cathode materials of secondary batteries suffered from is oxidative electrolyte decomposition inducing rapid capacity fading with discharge/charge cycling. Herein, a highly efficient strategy realizing stable cathode-electrolyte interphase (CEI) and ultralong-term cyclicability of 5 volt-cathode-material graphite flakes (GFs) for dual-ion batteries is demonstrated. The TiO2/carbon-comodified GF (TO/GF) cathode material with uniform distribution and tight bonding of the nanosized TiO2/carbon layer on the GF surface is synthesized, in which the GF surface is partitioned into nanodomains by the uniformly distributed TiO2 nanoparticles. Meanwhile, the amorphous carbon layer acts as a gummed tape bonding tightly the TiO2 nanoparticles on the graphite flake surface. Serial electrochemical impedance spectroscopy and structural/chemical analyses demonstrate that these unique structural characteristics of the TiO2/carbon comodification endow the TO/GF cathode material with a stable CEI layer coupled with much reduced electrolyte decomposition. Consequently, extremely high cyclicability of 10,000 stable discharge/charge cycles with an extremely low capacity fading rate of 0.0021% for anion PF6- storage is realized. This efficient strategy has a potential to be extended to other high-voltage cathode materials and further scaled to the industrial level.