Effects of Different Manufacturing Processes on TEMPO-oxidized CNF Performance as binder for Flexible Lithium-ion Batteries

Huiran Lu, Valentina Guccini, Hyeyun Kim, German Salazar-Alvarez, Göran Lindbergh, and Ann Cornell*

ACS Appl. Mater. Interfaces (2017)
DOI: 10.1021/acsami.7b10307

Abstract:
Carboxylated cellulose nanofibers (CNF) prepared using the TEMPO-route are good binders of electrode components in flexible lithium-ion batteries (LIB). However, the different parameters employed for the defibrillation of CNF, such as charge density and degree of homogenization, affect its properties when used as binder. This work presents a systematic study of CNF prepared with different surface charge densities and various degrees of homogenization and their performance as binder for flexible LiFePO4 electrodes. The results show that the CNF with high charge density had shorter fiber lengths compared with the CNF with low charge density, as observed with atomic force microscope (AFM). Also, CNF processed with a large number of passes in the homogenizer showed a better fiber dispersibility, as observed with rheological measurements. The electrodes fabricated with highly charged CNF exhibited the best mechanical and electrochemical properties. The CNF at the highest charge density (1550 µmol g-1) and lowest degree of homogenization (3+3 passes in the homogenizer) achieved the overall best performance, including a high Young’s modulus of approximately 311 MPa and a good rate capability with a stable specific capacity of 116 mAh g-1 even up to 1C. This work allows a better understanding of the influence of the processing parameters of CNF on their performance as binder for flexible electrodes. The results can also contribute to the understanding of the optimal processing parameters of CNF to fabricate other materials, e.g., membranes or separators.