The current lithium ion battery (LIB) technology has reached a very high degree of development and market share [1, 2]. However, several important bottlenecks still impede further spreading of lithium ion batteries into the EV market [2, 3]. Among them, their relatively high price and negative environmental impact have been addressed in this work. In particular, at the electrode manufacturing stage, the replacement of toxic and expensive N-Methyl-2-pyrrolidone (NMP) solvent by water is considered an innovative and promising approach to reduce both the environmental impact and the final price of the batteries [4] without sacrificing electrochemical performance [5].

Here, we report the development of a large format LiNi_xMn_yCo_zO₂ (NMC) - Graphite (C) pouch cell, with both electrodes prepared via aqueous processes using waterborne binders. The NMC-Graphite electrochemical system was chosen because it is considered as one of the most promising combinations for large format batteries for EV applications, in which both active materials are compatible with aqueous binders [6]. The positive electrode was composed of a commercial NMC (111) material. The negative electrode was prepared on the basis of C-NERGY™ ACTILION_1 graphite (IMERYS Graphite & Carbon) specially developed for better processability in aqueous slurries. Waterborne PVdF latexes (SOLVAY SPECIALTY POLYMERS ITALY) have been used as binders for both electrodes. Commercially available sodium carboxymethyl cellulose has been used as a dispersant for negative and positive electrode slurries. The formulation and design of the positive and negative electrodes was tailored to meet the MAT4BAT European project tasks and cell specifications.

The negative and positive electrode slurries with elaborated formulations have been successfully scaled up to 3 and 6 kg, respectively. Then, more than 100 metres length double-side coated electrode rolls have been manufactured on a coating pilot line. Finally, several NMC/Graphite pouch cells with a stack design were assembled on automated pilot equipment. As shown in Figure 1, the manufactured NMC/C pouch cell with nominal capacity 17 Ah has demonstrated promising C-rate capability and stable long term cyclability with no negative influence of the aqueous processing.

It should be noted that obtained specific energy density of 143 Wh/kg (@ 0.2C discharge) is very close to the commercial benchmark as defined within the MAT4BAT EU project. Thus, presented results allow for the conclusion that aqueous processing is a successful approach for manufacturing large format NMC-Graphite lithium ion cells for EV applications.

The study has been performed within the MAT4BAT project funded by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement #608931. We would like to acknowledge Celaya, Emparanza y Galdós Internacional S.A. for the manufacturing of the NMC/C pouch cells.

References:

1. EUROBAT E-mobility Battery R&D Roadmap 2030, http://www.eurobat.org/sites/default/files/eurobat_emobility_roadmap_lores_2.pdf
2. LUX Research press release: http://www.marketwired.com/press-release/next-generation-batteries-beyond-li-ion-will-be-worth-10-billion-in-2030-2078054.htm
3. R Van Noorden, Nature 507 (7490) 26-28.
4. D.L. Wood et al., J. Power Sources, 275 (2015) 234-242.
5. A. Kvasha et al., C-LiFePO₄ / Graphite pouch cell based on aqueous processed electrodes (P-064), in: Proceedings of the 8^th International Conference on Advanced Lithium Batteries for Automobile Applications; 2015, Sept. 30 – Oct. 2; Bilbao (Spain), p. 115.
6. N. Loeffler et al., J. Power Sources, 248 (2014) 915-922.