Hydroxyethyl Cellulose as Water-Soluble Co-Binder for High Mass Loading LiNi_0.5Mn_1.5O₄ Lithium-Ion Battery Cathodes

Combining high-voltage cobalt-free LiNi_0.5Mn_1.5O₄ (LNMO) with fluorine-free water-soluble binders holds the promise of achieving more sustainable and environment-friendly lithium-ion batteries (LIBs). However, achieving high mass loading electrodes with lithium transition metal oxides as the active material remains a challenge. Herein, 2-hydroxyethyl cellulose (HEC) is proposed as suitable binding agent, crosslinked via citric acid with guar gum (GG). The incorporation of HEC is pivotal for realizing a homogeneous dispersion of the electrode components, which is essential for the mechanical properties. Hence, the advantageous combination of co-crosslinked HEC and GG allows for the simultaneous optimization of electrochemical and mechanical properties, enabling the preparation of well performing high mass loading LNMO electrodes with about 15 mg cm^-2, providing a capacity retention as good as reference electrodes employing polyvinylidene difluoride as binder. Coupling these electrodes with graphite-based negative electrodes enables lithium-ion cells with an areal capacity of ~2.2 mAh cm^-2 and a capacity retention of 82 % after 200 cycles, rendering this system promising for the realization of water-processed, F-free, high-voltage cathodes.