Hydroxyl group of cellulose derivatives in promoting Li+ transport mechanism in solid polymer electrolyte membrane†

The incorporation of nanocellulose (NC) with cellulose derivatives, specifically hydroxypropyl methylcellulose (HPMC), hydroxypropyl cellulose (HPC), and hydroxyethyl cellulose (HEC), resulting in a solid polymer electrolyte (SPE). The impact of the hydroxyl group on these cellulose derivatives on the nano cellulose-based solid polymer electrolyte (SPE) was examined in terms of its physical characteristics and electrochemical efficiency. Molecular docking simulations were employed to examine the interaction between LiTFSI and hydroxyl groups in the polymer matrix, seeking to gain a greater understanding of the dissociation mechanism of LiTFSI and facilitate the mobility of the Li cation. The XPS and FTIR spectra prove that the HPMC/NC composite solid polymer electrolyte (SPE) polymer chain forms a novel interaction bond with the TFSI anion. Consequently, it enables simple transport of a large number of free Li⁺ ions, leading to a significant ionic conductivity of 1.05 × 10⁻³ S cm⁻¹. The lithium transfer number for the composite of HPMC, HPC, and HEC in NC composite was 0.59, 0.35, and 0.49, respectively. The HPMC/NC composite (4 V) exhibits a more excellent lithium battery potential range compared to HPC (2.5 V) and HEC (3 V) as identified through linear sweep voltammetry (LSV). The aforementioned discoveries suggest that the presence of a hydroxyl structure in the HPMC/NC composition led to the highest mechanical qualities and enhanced electrochemical performance. This indicates that the hydroxyl group in HPMC/NC can serve as a solid polymer electrolyte for lithium-ion batteries and effective energy storage.