Carrageenan as a Sacrificial Binder for 5 V LiNi<sub>0.5</sub> Mn<sub>1.5</sub> O<sub>4</sub> Cathodes in Lithium-Ion Batteries.

Chang, Barsa; Yun, Dae Hui; Hwang, Insu; Seo, Joon Kyo; Kang, Joonhee; Noh, Gyeongho; Choi, Sunghun; Choi, Jang Wook · Adv Mater · 2023

basic_science · Level V

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Abstract

5 V-class LiNi<sub>0.5</sub> Mn<sub>1.5</sub> O<sub>4</sub> (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 LiSO<sub>x</sub> F, 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.