Size Effects in Sodium Ion Batteries

Abstract

Sodium ion batteries (SIBs) are promising candidates for large-scale energy storage owing to the abundant sodium resources and low cost. The larger Na + radius (compared to Li + ) usually leads to sluggish reaction kinetics and huge volume expansion. One of the efficient strategies is to reduce the size of electrode materials or the components of electrolytes to a suitable scale where size effect begin to emerge, leading to the improved or varied thermodynamics, kinetics, and mechanisms of sodium storage. However, only a few systematic reviews address size effects in SIBs, which requires further attention urgently. Herein, after a brief discussion of the general size effect, the size-related kinetics, thermodynamics (equilibrium voltage and morphology), and sodium storage mechanisms (phase transition, conversion reaction, interfacial, and nanopore storage) of electrode materials are presented. The size effect on liquid, polymer, and inorganic solid-state electrolytes are discussed as well, including the size of solvent molecules, Na salts, and inorganic fillers. Finally, neutral and adverse size effects are discussed, and some useful strategies are proposed to overcome them. The deep insights into the size effect will provide instructive guidelines for developing SIBs and other new energy storage systems.

Heteroatom-Substituted P2–Na2/3Ni1/4Mg1/12Mn2/3O2 Cathode with {010} Exposing Facets Boost Anionic Activity and High-Rate Performance for Na-Ion Batteries

“…To improve the Na + ion transport kinetics, several strategies have been used in the research of layered oxide materials. Nanocrystallization can shorten the diffusion channel distance for Na ions but poses high risk of side reactions between the electrolyte and the bare Na x TMO 2 electrode. − Constructing a Na + -conductive surface layer could prevent these side reactions and protect Na x TMO 2 materials from corrosion. − Even so, the diffusion channel for Na ion transportation in the hexagonal structure is still limited. Unlike other contenders, such as polyanionic and Prussian-blue analogues, Na x TMO 2 materials just provided two-dimensional channels for Na + ion intercalation.…”

In situ thermal exclusion induced Sb and Sb-doped SnO2 nanoheterostructuring and its improvements in cycling stabilities and rate capacities for Na+ storage

“…The high capacity contribution from the SRCC can be attributed to the nanostructure of the Sb-ATO hetero-NPs, which increases the surface to volume ratio, making more active materials accessible to the electrolyte. 9 DFT calculations were performed to gain better understanding on how the Sb doped structure of ATO and the Sb-ATO heterostructuring improve the performance of C@Sb-ATO/ MWCNTs. Fig.…”

“…Nanostructuring can not only shorten the diffusion path length of Na + ions in MCs and facilitate their better accessibility to the electrolyte, but also reduce the total internal strain of MCs caused by the volumetric changes upon sodiation/ desodiation. 9,10 Elemental doping can effectively tune the electronic structure of MCs, improving the electrical conductivity of MCs and promoting the adsorption and diffusion of Na + ions in MCs. 11,12 Likewise, the electronic structure of MCs can also be modulated by heterostructuring through interfacial interactions, improving the electrical conductivity and the sodiation/ desodiation kinetics of MCs.…”

“…The high capacity contribution from the SRCC can be attributed to the nanostructure of the Sb-ATO hetero-NPs, which increases the surface to volume ratio, making more active materials accessible to the electrolyte. 9…”

Study of Synergistic Effects of Cu and Fe on P2-Type Na0.67MnO2 for High Performance Na-Ion Batteries

“…Na-ion batteries were discovered at the same time as Li-ion batteries, but have long been in a state of obscurity due to their suboptimal energy density. − After the high cost of Li-ion batteries and the lack of lithium resources come to the fore, Na-ion batteries become a continuing hot spot and were widely studied. − At present, the booming electric vehicle market and the growing demand for energy storage have led to new challenges and opportunities for rechargeable batteries, including sodium-ion batteries. − However, it should not be overlooked that, despite the advantages in cost and resource, the large radius and slow kinetic of Na ions greatly limit the development of sodium storage materials as the active material, which directly affects the electrochemical performance. − Therefore, the development of sodium storage cathode materials with excellent performance is considered to be the key to design advanced sodium-ion batteries.…”