Flexible and Lightweight Lithium-Ion Batteries Based on Cellulose Nanofibrils and Carbon Fibers

Abstract

Flexible, low-weight electrodes with integrated current collectors based on chopped polyacrylonitrile carbon fibers (CF) were produced using an easy, aqueous fabrication process, where only 4 wt% of TEMPO-oxidized cellulose nanofibrils (CNF) were used as the binder. A flexible full cell was assembled based on a LiFePO 4 (LFP) positive electrode with a CF current collector and a current collector-free CF negative electrode. The cell exhibited a stable specific capacity of 121 mAh g −1 based on the LFP weight. The CF in the negative electrode acted simultaneously as active material and current collector, which has a significant positive impact on energy density. Stable specific capacities of the CF/CNF negative electrode of 267 mAh g −1 at 0.1 C and 150 mAh g −1 at 1 C are demonstrated. The LFP/CNF with CF/CNF, as the current collector positive electrode (LFP-CF), exhibited a good rate performance with a capacity of~150 mAh g −1 at 0.1 C and 133 mAh g −1 at 1 C. The polarization of the LFP-CF electrode was similar to that of a commercial Quallion LFP electrode, while much lower compared to a flexible LFP/CNF electrode with Al foil as the current collector. This is ascribed to good contact between the CF and the active material.

Effects of Different Manufacturing Processes on TEMPO-Oxidized Carboxylated Cellulose Nanofiber Performance as Binder for Flexible Lithium-Ion Batteries

“…CNF is a biomaterial, not from fossil sources, which is the case for conventional binders such as polyvinylidene fluoride (PVDF). Another advantage is the possibility to produce papers with several layers (compare multiply paper), where the individual layers can be current collectors, 25 electrodes, or separator 22,23 integrated in a single paper sheet. The binder is an inactive material which increases the polarization of the electrodes.…”

A review of current collectors for lithium-ion batteries

“…7b-d shows a flexible Li4Ti5O12 anode on a carbon fibre paper current collector, which delivers a capacity higher than 150 mAh g -1 after repeated bending [205]. A similar study for developing flexible current collectors based on carbonaceous materials can be found in [206]. Fourthly, carbonaceous current collectors can improve electron and ion transfer kinetics.…”

Toward Low-Cost All-Organic and Biodegradable Li-Ion Batteries

“…To maintain good electronic conductivity without affecting film integrity, a mixture of cellulose fibers with 2D or 1D carbons are often reported in literature as a less expensive option for fabricating self-standing electrode films. Cornell et al fabricated an LFP composite electrode made of 1D polyacrylonitrile carbon fibers (CF) and TEMPO-oxidized cellulose nanofibrils as binder 29 . The electrode exhibits a high Young's modulus of approximately 201±12.7 MPa and an electrical conductivity of 95S•cm −1 ; it delivers ~121 mAh•g −1 when cycled at C/10 versus a self-standing CF electrode.…”

“…Interestingly, the paper-making process also allowed the electrodes (cathode and anode) and the separator to be integrated into a single flexible and strong structure resulting from successive filtration steps 31 . Numerous examples of cathodes (LFP 29,32 ), anodes (MoS 2 33 , graphite 34 , Si 35 ), and even full Li-ion cells (LFP/graphite 31 , LFP/ LTO 36 ) have been successfully prepared through the paper-making process using different forms of cellulose as binder. Finally, several works have reported flexible electrodes for batteries and supercapacitors that employ cellulose as substrate [37][38][39] or binder 40,41 .…”