Direct synthesis of a lithium carboxymethyl cellulose binder using wood dissolving pulp for high-performance LiFePO4 cathodes in lithium-ion batteries

Abstract

Lithium carboxymethyl cellulose (CMC-Li) is a promising novel water-based binder for lithium-ion batteries. The direct synthesis of CMC-Li was innovatively developed using abundant wood dissolving pulp materials from hardwood (HW) and softwood (SW). The resulting CMC-Li-HW and CMC-Li-SW binders possessed a suitable degree of substitutions and excellent molecular weight distributions with an appropriate quantity of long- and short-chain celluloses, which facilitated the construction of a reinforced concrete-like bonding system. When used as cathode binders in LiFePO₄ batteries, they uniformly coated and dispersed the electrode materials, formed a compact and stable conductive network with high mechanical strength and showed sufficient lithium replenishment. The prepared LiFePO₄ batteries exhibited good mechanical stability, low charge transfer impedance, high initial discharge capacity (∼180 mAh/g), high initial Coulombic efficiency (99 %), excellent cycling performance (<3% loss over 200 cycles) and good rate capability, thereby outperforming CMC-Na and the widely used cathode binder polyvinylidene fluoride.

Keywords: Cathode binder; Dissolving pulp; LiFePO(4); Lithium carboxymethyl cellulose; Water-based binder.