Carrageenan as a Sacrificial Binder for 5 V LiNi0.5Mn1.5O4 Cathodes in Lithium‐Ion Batteries

5 V‐class LiNi0.5Mn1.5O4 (LNMO) with its spinel symmetry is a promising cathode material for lithium‐ion batteries. However, the high‐voltage operation of LNMO renders it vulnerable to interfacial degradation involving electrolyte decomposition, which hinders long‐term and high‐rate cycling. Herein, this longstanding challenge presented by LNMO is overcome by incorporating a sacrificial binder, namely, λ‐carrageenan (CRN), a sulfated polysaccharide. This binder not only uniformly covers the LNMO surface via hydrogen bonding and ion‐dipole interaction but also offers an ionically conductive cathode–electrolyte interphase layer containing LiSOxF, a product of the electrochemical decomposition of the sulfate group. Taking advantage of these two auspicious properties, the CRN‐based electrode exhibits cycling and rate performance far superior to that of its counterparts based on the conventional poly(vinylidene difluoride) and sodium alginate binders. This study introduces a new concept, namely “sacrificial” binder, for battery electrodes known to deliver superior electrochemical performance but be adversely affected by interfacial instability. λ‐Carrageenan (CRN) is introduced as a “sacrificial” binder to produce a desired LiSOxF‐rich cathode–electrolyte interphase on 5 V‐class LiNi0.5Mn1.5O4 from its innate sulfate functionality. CRN also protects the cathode surface from indiscriminate side reactions by its uniform coverage involving hydrogen bonding and ion‐dipole interaction, thereby catching two challenging rabbits of stable cyclability and high‐rate performance simultaneously.