Nanocellulose Structured Paper-Based Lithium Metal Batteries

We report for the first time, a lithium metal battery (LMB) design based on low-cost, renewable, and mechanically flexible nanocellulose fibers (NCFs) as the separator as well as substrate materials for both the positive and negative electrodes. Combined with carbon nanofibers, the NCFs yield 3D porous conducting cellulose paper (CCP) current collectors with large surface areas, enabling a low effective current density. The porous structure yields a dendrite-free deposition of lithium (Li), faciliates the mass transport within the electrodes, and also compensates for the volume changes during the cycling. Stable Li electrodes are obtained by electrodepositing Li on CCP substrates while positive electrodes are realized by embedding LiFePO4 (LFP) particles within the flexible CCP matrix. The mesoporous NCF separator features a homogeneous pore distribution which provides uniform current distributions at the electrodes. This effect, which yields a more homogeneous Li deposition on the negative electrode as well as improves the safety, lifespan, and sustainability of the LMB. As a result, the present all-nanocellulose-based LMB demonstrates excellent cycling stability for a Li metal battery obtained to date, with 91% capacity retention after 800 cycles and 85% capacity retention after 1000 cycles at a rate of 2 C (i.e., 1.27 mA cm–2).