Covalently Joined Electrode Architectures for Extreme Fast Charging Li-Ion Batteries
Authors: Rangom Yverick , Pope Michael 
Published: February 2024

Li-ion batteries are the backbone of all electric vehicles (EVs) in production today [1]. However, they compete poorly against the few-minute refueling time of fossil fuel powered vehicles [2, 3]. To successfully replace fossil fuel powered vehicles, the EV batteries must support charging rates under the 15-minute mark as determined by the eXtreme Fast Charging (XFC) standard defined by the U.S. Department of Energy [4]. When subjected to XFC charging rates, well-known problems of lithium plating and delamination plague graphite anodes due to local potential gradients and binder degradation respectively [5].

Our work replaces the traditional polymer binder with conductive titanium carbide interconnects that covalently join graphite particles as well as bond them to the current collector [6]. This new architecture demonstrates ~400% increase in electrical conductivity compared to traditional architectures with polymer binders while maintaining interparticle integrity and improving adhesion. The adhesion and mechanical properties are provided by conductive chemical bonds mitigating delamination as these novel bonds suffer less mechanical and chemical degradation under high current rates than adhesion provided by polymer binders. The improved conductivity was also utilized to form a solid electrolyte interphase (SEI) at rates up to 4C reducing the ionic impedance of the SEI interface significantly [7]. The improved graphite electrodes can sustain 15-minute charge maintaining 80% of the specific capacity of the graphite particles for 800 cycles at commercially relevant loadings. Our studies introduce an effective strategy to engineer Li-ion battery electrode architectures that simultaneously improve electrical and ionic conductivity mitigating lithium plating and delamination under XFC charging rate needed for the mass adoption of EVs.

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