In this review, we summarize research efforts to realize Na-based organic materials for novel battery chemistries. Na is a more abundant element than Li, thereby contributing to less costly materials with limited to no geopolitical constraints while organic electrode materials harvested from biomass resources provide the possibility of achieving renewable battery components with low environmental impact during processing and recycling. Together, this can form the basis for truly sustainable electrochemical energy storage. We explore the efforts made on electrode materials of organic salts, primarily carbonyl compounds but also Schiff bases, unsaturated compounds, nitroxides and polymers. Moreover, sodiated carbonaceous materials derived from biomasses and waste products are surveyed. As a conclusion to the review, some shortcomings of the currently investigated materials are highlighted together with the major limitations for future development in this field. Finally, routes to move forward in this direction are suggested.

A composite electrolyte based on a garnet electrolyte (LLZO) and polyester-based co-polymer (80:20 ε-caprolactone (CL)-trimethylene carbonate, PCL-PTMC with LiTFSI salt) is prepared. Integrating the merits of both ceramic and co-polymer electrolytes is expected to address the poor ionic conductivity and high interfacial resistance in solid-state lithium-ion batteries. The composite electrolyte with 80 wt % LLZO and 20 wt % polymer (PCL-PTMC and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) at 72:28 wt %) exhibited a Li-ion conductivity of 1.31 × 10^–4 S/cm and a transference number (t_Li⁺) of 0.84 at 60 °C, notably higher than those of the pristine PCL-PTMC electrolyte. The prepared composite electrolyte also exhibited an electrochemical stability of up to 5.4 V vs Li⁺/Li. The interface between the composite electrolyte and a LiFePO₄ (LFP) cathode was also improved by direct incorporation of the polymer electrolyte as a binder in the cathode coating. A Li/composite electrolyte/LFP solid-state cell provided a discharge capacity of ca. 140 mAh/g and suitable cycling stability at 55 °C after 40 cycles. This study clearly suggests that this type of amorphous polyester-based polymers can be applied in polymer-in-ceramic composite electrolytes for the realization of advanced all-solid-state lithium-ion batteries.

Ball-milling of graphite results in graphene layer exfoliation and defect formation, leading to enhanced performance as a K-ion battery anode.

The generation of a distribution of nanoparticles upon conversion reaction of thin Cu₂O layers is demonstrated to produce a wide electrochemical potential window, as well as a distinctive capacity increase in large area three-dimensional electrodes. Cu nanopillars with a 10–15 nm Cu₂O coating containing traces of nanocrystalline Fe₂O₃ yield capacities up to 0.265 mA h cm⁻² (at 61 mA g⁻¹), excellent cycling for more than 300 cycles and an electroactive potential window larger than 2 V, due to the size effects caused by the various Cu/Cu₂O nanoparticles formed during conversion/deconversion. These 3D Li-ion battery electrodes based on electrodeposited Cu nanopillars spontaneously coated with a Cu₂O layer are compatible with current densities of 16 A g⁻¹ (i.e. 61 C rates) after aerosol-assisted infiltration with an iron acetate solution followed by low-temperature pyrolysis. The capacity of the composite material increases by 67% during 390 cycles due to the growth of the electroactive area during the electrochemical milling of Cu₂O forced by its repeated conversion/de-conversion. The latter generates a distribution of nanoparticles with different sizes and redox potentials, which explains the broad potential window, as well as the significant capacity contribution from double layer charging. These 3D electrodes should be well-suited for Li-ion microbatteries and Li-ion batteries in general, since they combine high capacities per footprint area with excellent power capabilities. More importantly, such electrodes grant access to fundamental understanding of the electrochemical behaviour of these active materials providing new insights into both conversion mechanisms and nanostructured interfaces more in general.