Camphene-Assisted Fabrication of Free-Standing Lithium-Ion Battery Electrode Composites

Abstract

Free-standing electrode (FSE) architectures hold the potential to dramatically increase the gravimetric and volumetric energy density of lithium-ion batteries (LIBs) by eliminating the parasitic dead weight and volume associated with traditional metal foil current collectors. However, current FSE fabrication methods suffer from insufficient mechanical stability, electrochemical performance, or industrial adoptability. Here, we demonstrate a scalable camphene-assisted fabrication method that allows simultaneous casting and templating of FSEs comprising common LIB materials with a performance superior to their foil-cast counterparts. These porous, lightweight, and robust electrodes simultaneously enable enhanced rate performance by improving the mass and ion transport within the percolating conductive carbon pore network and eliminating current collectors for efficient and stable Li+ storage (>1000 cycles in half-cells) at increased gravimetric and areal energy densities. Compared to conventional foil-cast counterparts, the camphene-derived electrodes exhibit ∼1.5× enhanced gravimetric energy density, increased rate capability, and improved capacity retention in coin-cell configurations. A full cell containing both a free-standing anode and cathode was cycled for over 250 cycles with greater than 80% capacity retention at an areal capacity of 0.73 mA h/cm2. This active-material-agnostic electrode fabrication method holds potential to tailor the morphology of flexible, current-collector-free electrodes, thus enabling LIBs to be optimized for high power or high energy density Li+ storage. Furthermore, this platform provides an electrode fabrication method that is applicable to other electrochemical technologies and advanced manufacturing methods.

Camphene as a Mild, Bio-Derived Porogen for Near-Ambient Processing and 3D Printing of Porous Thermoplastics

“…The printed filament also possesses a fairly uniform 15–20 μm skin layer of dense polymer at the air-interface of the filament. The formation of a skin layer has been observed in other camphene-based processes as well . However, when printing over a larger area (i.e., multiple filament widths), this layer forms between print layers instead of around individual filaments (as observed by SEM in Figure S12).…”

“…The formation of a skin layer has been observed in other camphene-based processes as well. 33 However, when printing over a larger area (i.e., multiple filament widths), this layer forms between print layers instead of around individual filaments (as observed by SEM in Figure S12). We expect this is due to the coupling of the geometry and cooling rates; a single filament is exposed on all sides and can cool both convectively and through sublimation, while larger 3D printed parts have decreased surface area per volume and increased thermal mass and therefore cool more slowly.…”

“…As for chemical hazards, the proposed system is a two-component system containing only camphene and a commercial thermoplastic material. This is advantageous to systems where the polymers are polymerized in situ, requiring the use of volatile monomers and incorporation of initiating systems. , Furthermore, freeze-casting using camphene is a robust and versatile method which could therefore be compatible with a wide range of materials systems including various homopolymers, copolymers, and composite systems. ,− Here, we present the use of camphene as both a solvent and a porogen for the generation of porous thermoplastic parts via conventional compression molding and the common additive manufacturing technique known as direct ink writing (DIW).…”

Hierarchical Electrode Architecture Enabling Ultrahigh-Capacity LiFePO4 Cathodes with Low Tortuosity

“…In order to construct a better energy storage system, higher energy density, longer life, and stricter safety requirements have been put forward for battery-type energy storage devices. − Today, many studies have focused on developing new synthetic electrode materials, whereas less effort has been dedicated to improving the design of electrodes and devices without changing the underlying chemistry of the electrode materials. To meet energy requirements to the maximum extent, electrode architecture engineering is of great importance for advanced energy storage devices. − …”

A Balancing Act: Experimental Insights into the Volume Fraction of Conductive Additive in Lithium-Ion Battery Electrodes

“…This study aims to help fill that gap. We focus on experimentally varying the volumetric loading of SuperP in a LIB electrode by using our previously developed freestanding electrode platform 26 to demonstrate the importance of balancing the conductive additive volume fraction in electrodes of different thicknesses and active material loadings. While this study does not aim to produce a comprehensive quantitative model, it is simple and straightforward in providing an experimental demonstration of how approaching LIB electrode design from a volume rather than mass basis may be more informative for gathering research insight.…”