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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.

As inexpensive anodes for sodium-ion batteries (SIBs), hard carbons are a highly tunable class of materials that hold promise to alleviate societal reliance on traditional lithium-based battery chemistries. However, the combination of sodium storage mechanisms, ranging from surface adsorption to pore-filling, has led to convoluted structure−function relationships and debate toward optimal desired material properties. To this end, a suite of nitrogen and phosphorus codoped carbons (NPCs) derived from phytic acid cross-linked polyaniline precursors were systematically evaluated as SIB anodes at practical cycling rates. The addition of calcium or zinc salts to the cross-linked polymerization process before pyrolysis ultimately led to nanoporous hard carbons with varied physicochemical properties and subsequent electrochemical performances. A majority of sodium storage capacity in these polyaniline-derived NPCs occurred in a higher-voltage, sloping region and primarily stemmed from sodium-ion adsorption at defective sites. This storage mechanism was also associated with increased stability compared to lower-voltage mechanisms related to bulk sodium insertion, both in cycle life and rate capability. Best-performing NPCs demonstrated an initial capacity of 212.1 mAh g −1 with approximately 77% capacity retention over 300 cycles at a cycling rate of ∼1 C, and high-rate testing revealed a considerable fast charge capacity of 117.8 mAh g −1 (∼8 C, 7.5 min charge time). The superior rate performance and stability of certain NPCs were strongly correlated to the lateral nanocrystalline domain sizes (L a ). Overall, this study outlines a simple and tunable synthetic method for the production of high-performance NPCs for SIBs and sheds light on important considerations for the design of carbon anodes for practical SIBs.

Continually increasing technological demands and widespread adoption of electric vehicles has spurred significant motivation to improve the performance of lithium-ion batteries (LIBs). In addition to improving intrinsic battery chemistry, optimizing electrode morphology and cell design can unlock increased energy density and rate capability to enable the adoption of next generation LIBs for societal decarbonization. Although free-standing electrode (FSE) architectures hold the potential to dramatically increase the gravimetric and volumetric energy density of LIBs by eliminating the parasitic dead weight and volume associated with traditional metal foil current collectors, current FSE fabrication methods suffer from insufficient mechanical stability, electrochemical performance, or industrial adaptability. Here, we demonstrate a scalable camphene-assisted fabrication method that allows simultaneous casting and templating of FSEs comprised of common LIB materials with performance superior to foil-cast counterparts. These porous, lightweight, and robust electrodes simultaneously enable enhanced rate performance by improving mass and ion transport within the percolating conductive carbon pore network and eliminating current collectors for efficient and stable Li+ storage (> 1000 cycle in half-cells) at increased gravimetric and areal energy densities. Compared to conventional foil-cast counterparts, the camphene-derived electrodes exhibit ~1.5x enhanced gravimetric energy density, increased rate capability, and improved capacity retention in coin-cell configurations. A full cell with freestanding anode and cathode cycled for over 250 cycles with greater than 80% capacity retention at an areal capacity of 0.73 mAh/cm2 . This active-material-agnostic electrode fabrication method holds the potential to tailor the morphology of flexible, current-collector-free electrodes to optimize LIBs for high power or high energy density Li+ storage and is applicable to other electrochemical technologies and advanced manufacturing methods