Suppressing Dynamic Interphase Degradation via a λ ‐Carrageenan Binder for Robust Wide‐Voltage Cycling of LiNi 0.5 Mn 1.5 O 4 Cathodes

Lithium nickel manganese oxide (LiNi0.5Mn1.5O4, LNMO) is a promising cobalt-free cathode operating at ∼4.7 V primarily through the Ni4+/Ni2+ redox couple. Deep discharging to 2.30 V can activate the electrochemically inert Mn, which contributes additional capacity and improves energy density. However, repeated cycling over such a wide-voltage window (2.30-4.95 V) imposes severe mechanical stress and dynamic interphase degradation. Here, we demonstrate that these challenges are effectively mitigated by employing λ-carrageenan (CGN) as a multifunctional binder that maintains the electrode integrity and regulates cathode-electrolyte interphase (CEI) evolution. The resulting LNMO cathode achieves a high specific capacity of 186 mAh g-1 and an energy density of 755 Wh kg-1 within 2.30-4.95 V through simultaneous activation of Ni and Mn redox. Notably, the CGN/LNMO electrode retains 87.7% of its capacity after 200 cycles at 0.5C, compared to only 29.6% for a conventional PVDF/LNMO electrode. This binder-enabled interfacial regulation strategy establishes an effective pathway toward stable wide-voltage operation of high-energy-density cathode materials.