Although Li-ion batteries have emerged as the battery of choice for electric vehicles and large-scale smart grids, significant research efforts are devoted to identifying materials that offer higher energy density, longer cycle life, lower cost, and/or improved safety compared to those of conventional Li-ion batteries based on intercalation electrodes. By moving beyond intercalation chemistry, gravimetric capacities that are 2–5 times higher than that of conventional intercalation materials (e.g., LiCoO2 and graphite) can be achieved. The transition to higher-capacity electrode materials in commercial applications is complicated by several factors. This Review highlights the developments of electrode materials and characterization tools for rechargeable lithium-ion batteries, with a focus on the structural and electrochemical degradation mechanisms that plague these systems.

We describe here the metal-templated transformation of carbon nitride (C 3 N 4 ) into nitrogencontaining carbons as anodes for Li-ion batteries (LIBs). Changing the template from the carbon-and nitrogenimmiscible Cu powder to the carbon-and nitrogenmiscible Fe powder yields different carbons; while Fe templating produces graphitized carbons of low (<10%) nitrogen content and moderate pore volume, Cu templating yields high defect-density carbons of high (32−24%) nitrogen content and larger pore volume. The Li + storage capacity of the high nitrogen content and larger pore volume Cu-templated carbons exceeds that of the more graphitic Fe-templated carbons due to added contribution from Li + insertion/extraction from pores and defects and to reversible faradaic Li + reaction with nitrogen atoms. The Cutemplated carbon annealed at 750 °C delivers the highest specific capacity of 900 mAh g −1 at 0.1 A g −1 and 275 mAh g −1 at 20 A g −1 , while also achieving a 96% capacity retention after 2000 cycles at 2 A g −1 . The fabrication of higher mass loading electrodes (4.5 mg cm −2 ) provided a maximum areal capacity of 2.6 mAh cm −2 at 0.45 mA cm −2 (0.1 A g −1 ), comparable to the capacities of commercial LIB cells and favorable compared to other reported carbon materials.

The optical and catalytic properties of metal nanoparticles have attracted significant attention for applications in a wide variety of fields, thus prompting interest in developing sustainable synthetic strategies that leverage the redox properties of natural compounds or extracts. Here, we investigate the surface chemistry of nanoparticles synthesized using coffee as a biogenic reductant. Building on our previously developed synthetic protocols for the preparation of silver and palladium nanoparticle/carbon composite microspheres a combination of thermogravimetric and spectroscopic methods were used to characterize the carbon microsphere and nanoparticle surfaces. Infrared reflectance spectroscopy and single particle surface enhanced Raman spectroscopy were used to characterize Pd and Ag metal surfaces, respectively, following synthesis. Strongly adsorbed organic layers were found to be present at metal nanoparticle surfaces after synthesis. The catalytic activity of Pd nanoparticles in hydrogenation reactions were leveraged to study the availability of surface sites, and coffee-synthesized nanomaterials were compared to commercial Pd-based hydrogenation catalysts. Our results demonstrate that biogenic adsorbates block catalytic surface sites and affect nanoparticle functionality. These findings highlight the need for careful analysis of surface chemistry as it relates to the specific applications of nanomaterials produced using greener or more sustainable methods.

We report the synthesis and properties of a low-density (∼5 mg/cm) and highly porous (99.6% void space) three-dimensional reduced graphene oxide (rGO)/poly(acrylic acid) (PAA) nanocomposite aerogel as the scaffold for cathode materials in lithium-ion batteries (LIBs). The rGO-PAA is both simple and starts from readily available graphite and PAA, thereby providing a scalable fabrication procedure. The scaffold can support as much as a 75 mg/cm loading of LiFePO (LFP) in a ∼430 μm thick layer, and the porosity of the aerogel is tunable by compression; the flexible aerogel can be compressed 30-fold (i.e., to as little as 3.3% of its initial volume) while retaining its mechanical integrity. Replacement of the Al foil by the rGO-PAA current collector of the slurry-cast LFP (1.45 ± 0.2 g/cm tap density) provides for exemplary mass loadings of 9 mg/cm at 70 μm thickness and 1.4 g/cm density or 16 mg/cm at 100 μm thickness and ∼1.6 g/cm density. When compared to Al foil, the distribution of LFP throughout the three-dimensional rGO-PAA framework doubles the effective LFP solution-contacted area at 9 mg/cm loading and increases it 2.5-fold at 16 mg/cm loading. Overall, the rGO-PAA current collector increases the volumetric capacity by increasing the effective electrode area without compromising the electrode density, which was compromised in past research where the effective electrode area has been increased by reducing the particle size.

Bulk carbon nitride (C3N4) was transformed into hierarchically nanoporous, nitrogen-rich (N-rich) carbons via calcium chloride (CaCl2)-mediated thermal activation. By systematically varying the annealing time and CaCl2:C3N4 weight ratio, we describe the fragmentation-recombination porogen mechanism and show that Ca2+ effectively stabilizes pyridinic N species through high-temperature solvent–solute interactions. The resulting N-rich nanocarbons were applied as CO2 sorbents over the pressure range of 0–1.0 bar. For these relatively low surface area materials, surface chemistry has the dominant impact on the affinity for CO2 adsorption, primarily at low pressures relevant for carbon capture. An optimal sample with a gravimetric CO2 uptake of 1.9 mmol/g at 25 °C and 0.1 bar and large associated isosteric heat of adsorption (Q st > 45 kJ/mol) resulted in incredible CO2/N2 selectivity (S IAST = 105) for a simulated binary gas feed of 10% CO2 (1.0 bar, 25 °C). We attribute these attractive properties to a unique combination of dipole-rich surface chemistry (43 at % N), moderate porosity (V pore = 0.6 cc/g), and relatively small N2 accessible surface area (180 m2/g).