Feasibility of Chemically Modified Cellulose Nanofiber Membranes as Lithium-Ion Battery Separators

Hyeyun Kim; Ulriika Mattinen; Valentina Guccini; Haidong Liu; Germán Salazar-Alvarez; Rakel Wreland Lindström; Göran Lindbergh; Ann Cornell

doi:10.1021/acsami.0c08820

Feasibility of Chemically Modified Cellulose Nanofiber Membranes as Lithium-Ion Battery Separators

ACS Appl Mater Interfaces. 2020 Sep 16;12(37):41211-41222. doi: 10.1021/acsami.0c08820. Epub 2020 Sep 2.

Authors

Hyeyun Kim^{1

2}, Ulriika Mattinen², Valentina Guccini³, Haidong Liu⁴, Germán Salazar-Alvarez⁵, Rakel Wreland Lindström², Göran Lindbergh², Ann Cornell²

Affiliations

¹ Wallenberg Wood Science Centre, Royal Institute of Technology, KTH Royal Institute of Technology, Teknikringen 56-58, Stockholm SE-100 44, Sweden.
² Department of Chemical Engineering, KTH Royal Institute of Technology, Teknikringen 42, Stockholm SE-100 44, Sweden.
³ Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, P.O. Box 16300, Aalto 00076, Finland.
⁴ Department of Chemistry-Ångström Laboratory, Uppsala University, Lägerhyddsvägen 1, Uppsala SE-751 21, Sweden.
⁵ Department of Materials Science and Engineering-Ångström Laboratory, Uppsala University, Lägerhyddsvägen 1, Uppsala SE-751 21, Sweden.

PMID: 32812731
DOI: 10.1021/acsami.0c08820

Abstract

Chemical modification of cellulose is beneficial to produce highly porous lithium-ion battery (LIB) separators, but introduction of high charge density adversely affects its electrochemical stability in a LiNi_1/3Mn_1/3Co_1/3O₂ (NMC)/graphite full cell. In this study, the influence of carboxylate functional groups in 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated oxidized cellulose nanofibers (TOCNs) on the electrochemical performances of the LIB separator was investigated. X-ray photoelectron spectroscopy and in operando mass spectrometry measurements were used to elucidate the cause of failure of the batteries containing TOCN separators in the presence and absence of sodium counterions in the carboxylate groups and additives. For the TOCN separator with sodium carboxylate functional groups, it seems that Na deposition is the dominant reason for poor electrochemical stability of the cell thereof. The poor performance of the protonated TOCN separator, attributed to a high amount of gas evolution, is dramatically improved by adding 2 wt % of vinylene carbonate (VC) because of suppressed gas evolution. Unveiling the failure mechanism of the TOCN separators and successively implementing the strategies to improve performance, for example, removing Na, adding VC, and adjusting cycling rates, enable a remarkable cycling performance in the NMC/graphite full cell at ≈2 C (3 mA/cm²) of a fast discharging rate. Despite the aforementioned efforts and compromises required, an increased charge density of the TOCN is beneficial to acquire a mechanically stronger separator. In conclusion, the manufacturing process of cellulose nanofibers needs to be carefully adjusted to acquire a desired separator property. To the best of our knowledge, it is first reported to perform operando gas evolution measurements to systematically investigate the electrochemical stability of nanocellulose as an LIB separator material. The results elucidate not only the challenges for extensive applications of hygroscopic biomaterials for commercial LIBs but also the practical solutions to achieve high electrochemical stability of the materials.

Keywords: Li-ion batteries; cellulose; gas evolution; in operando mass spectrometry; separator.