Robust Interphases Constructed by an Excellent Ionic Conductivity Versatile Binder System for High-Voltage Li-Rich Mn-Based Layered Oxide Cathode

Abstract

Lithium-Rich Layered Oxide (LRMO) cathode has caused concern for high specific capacity. However, it still suffers from oxygen release, transition metal (TM) ion migration, and interfacial side reactions, leading to accelerated capacity fading, low Coulombic efficiency (CE), and poor rate capability. Herein, a high-voltage binder with excellent ionic conductivity (CPPFPBA) is constructed by combining carboxymethyl cellulose (CMC) and ionic-conductive poly(ethylene oxide) (PEO) through hydrogen bonding, with pentafluorophenylboronic acid (PFPBA) incorporated as an advanced additive. The H-bonding between carboxyl moieties (−COOH) in CMC and terminal hydroxyl (−OH) functionalities on PEO improves cathode adhesion, while the in situ incorporation of PFPBA increases the oxidation potential of the CPPFPBA composite binder to 5.35 V. Crucially, the CPPFPBA binder promotes the formation of a uniform F-rich structure on the LRMO surface. Thus, this modified binder both enhances Li⁺ transport capability and sustains an ionically conductive cathode electrolyte interphase layer during cycling. The artificial LiF-rich cathode electrolyte interphase (CEI) layer can effectively protect the cathode from side reactions and inhibit the dissolution of transition metal ions, thereby enhancing the electrochemical capacity and cycling performance of LRMO batteries. Consequently, the CPPFPBA-modified LRMO cathode not only exhibits high ICE (>84%) and a reversible capacity of 297 mAh g^–1 but also maintains exceptional cycling stability, retaining 102% of its initial capacity after 300 cycles at 200 mA g^–1.