**Lightweight Polymer-Carbon Composite Current Collector for Lithium-Ion Batteries**

#### **Marco Fritsch 1,\*, Matthias Coeler 1, Karina Kunz 2, Beate Krause 2, Peter Marcinkowski 1, Petra Pötschke 2, Mareike Wolter 1 and Alexander Michaelis 1**


Received: 16 October 2020; Accepted: 30 November 2020; Published: 8 December 2020

**Abstract:** A hermetic dense polymer-carbon composite-based current collector foil (PCCF) for lithium-ion battery applications was developed and evaluated in comparison to state-of-the-art aluminum (Al) foil collector. Water-processed LiNi0.5Mn1.5 O4 (LMNO) cathode and Li4Ti5O12 (LTO) anode coatings with the integration of a thin carbon primer at the interface to the collector were prepared. Despite the fact that the laboratory manufactured PCCF shows a much higher film thickness of 55 μm compared to Al foil of 19 μm, the electrode resistance was measured to be by a factor of 5 lower compared to the Al collector, which was attributed to the low contact resistance between PCCF, carbon primer and electrode microstructure. The PCCF-C-primer collector shows a su fficient voltage stability up to 5 V vs. Li/Li<sup>+</sup> and a negligible Li-intercalation loss into the carbon primer. Electrochemical cell tests demonstrate the applicability of the developed PCCF for LMNO and LTO electrodes, with no disadvantage compared to state-of-the-art Al collector. Due to a 50% lower material density, the lightweight and hermetic dense PCCF polymer collector o ffers the possibility to significantly decrease the mass loading of the collector in battery cells, which can be of special interest for bipolar battery architectures.

**Keywords:** lithium-ion battery; bipolar battery; polymer-carbon composite; current collector; water-based electrode slurries; carbon primer; CNTs; LMNO; LTO
