Encapsulating carboxymethyl substituted chitosan on LiNi0.5Mn1.5O4 cathode for enhanced charge/discharge performances

In this paper, two kinds of water-soluble carboxymethyl chitosan with different degrees of substitution (O-CCTS and O,N-CCTS) are synthesized for assembling high-performance cathode of lithium-nickel-manganate (LNMO) battery. The results show that the first round specific capacities of O-CCTS-LNMO, O,N-CCTS-LNMO and PVDF-LNMO are 123.2, 112.9 and 115.7 mAh center dot g(-1), respectively. Owing to abundant hydrogen bond in the water-soluble O-CCTS, the powder LiNi0.5Mn1.5O4 can be tightly wrapped by the linear polymer and uniformly coated on the electrode sheets. Meanwhile, the hydrogen bond and -NH2 can strongly chelate with transition metal ions (Mn2+, Ni2+), and suppress free direct entry into the electrolyte and thereby affect the migration of negative lithium particles. After 100 cycles at 0.2 C, the discharge capacity of O-CCTS-LNMO still reaches to 120.4mAh/g with 97.7% of the specific capacity retention rate, which is higher than that of the O,N-CCTS-LNMO (95.5%) and PVDF-LNMO (91.6%). Simultaneously, the impedance and cyclic performance of O-CCTS-LNMO cathode is significantly better than those of the latter two. Furthermore, the electrochemical performance improvement mechanism of these cathodes is discussed in details.

Automated summary

Two types of water-soluble carboxymethyl chitosan with different degrees of substitution were synthesized and used to assemble high-performance cathodes in lithium-nickel-manganese oxide (LNMO) batteries. The water-soluble O-CCTS provided abundant hydrogen bonding and chelation with metal ions, resulting in better wrapping and uniform coating of the cathode material on the electrode sheets. The O-CCTS-LNMO cathode exhibited higher discharge capacity and better impedance and cyclic performance compared to O,N-CCTS-LNMO and PVDF-LNMO.