Interfacial‐Catalysis‐Enabled Layered and Inorganic‐Rich SEI on Hard Carbon Anodes in Ester Electrolytes for Sodium‐Ion Batteries

Abstract

Constructing a homogenous and inorganic‐rich solid electrolyte interface (SEI) can efficiently improve the overall sodium‐storage performance of hard carbon (HC) anodes. However, the thick and heterogenous SEI derived from conventional ester electrolytes fails to meet the above requirements. Herein, an innovative interfacial catalysis mechanism is proposed to design a favorable SEI in ester electrolytes by reconstructing the surface functionality of HC, of which abundant CO (carbonyl) bonds are accurately and homogenously implanted. The CO (carbonyl) bonds act as active centers that controllably catalyze the preferential reduction of salts and directionally guide SEI growth to form a homogenous, layered, and inorganic‐rich SEI. Therefore, excessive solvent decomposition is suppressed, and the interfacial Na+ transfer and structural stability of SEI on HC anodes are greatly promoted, contributing to a comprehensive enhancement in sodium‐storage performance. The optimal anodes exhibit an outstanding reversible capacity (379.6 mAh g−1), an ultrahigh initial Coulombic efficiency (93.2%), a largely improved rate capability, and an extremely stable cycling performance with a capacity decay rate of 0.0018% for 10 000 cycles at 5 A g−1. This work provides novel insights into smart regulation of interface chemistry to realize high‐performance HC anodes for sodium storage.

Reductive Competition Effect-Derived Solid Electrolyte Interphase with Evenly Scattered Inorganics Enabling Ultrahigh Rate and Long-Life Span Sodium Metal Batteries

“…Compared with the reference electrolytes, elements in the F/P + 3% LiTFSI electrolyte are different and polydisperse; some new elements, such as Li/N/S/F, have a share of 4.48, 1.56, 0.69, and 6.15% (Atomic %) in the SEI, respectively. As a whole, the inorganic components in F/P + 3% LiTFSI are higher than the other two electrolytes, thus leading to a higher electrical conductivity …”

“…As a whole, the inorganic components in F/P + 3% LiTFSI are higher than the other two electrolytes, thus leading to a higher electrical conductivity. 24 Transmission electron microscopy (TEM) was employed to further characterize the detailed structure and distribution of these inorganics and organics. As shown in Figure 3d, the components of SEI in F/P electrolyte are mainly composed of big-sized and clumsy inorganics, such as Na 2 O, Na 2 CO 3 , NaF, etc.…”

“…19−23 derived uneven inorganic and organic hybrid structure may limit the interfacial Na + transfer and result in poor rate performance. 24 Among which the organic components in SEI may lead to difficulty in diffusion at the interphase, while the inorganic components have some outstanding physicochemical properties such as high ionic conductivity, enhanced mechanical properties, and elevated interfacial energy to suppress the growth of metal dendrites. 25,26 Nevertheless, the structure of SEI can be regulated by molecules, functional groups, electrons, etc., but the complex process and high cost limit its commercial application.…”

“…In contrast to ether electrolytes, ester electrolytes possess exceptional oxidation resistance, a higher boiling point, a higher flash point, and sodium salt solubility, which are most likely to find wide commercial application. However, the ester electrolyte presents reactive activity with sodium metal, producing unstable and heterogeneous SEI during the repeated sodium plating and stripping, causing enlarged overpotentials, decreased coulomb efficiency, and a shortened cycle life of SMBs, especially at high currents. – Generally, the ester-derived uneven inorganic and organic hybrid structure may limit the interfacial Na + transfer and result in poor rate performance . Among which the organic components in SEI may lead to difficulty in diffusion at the interphase, while the inorganic components have some outstanding physicochemical properties such as high ionic conductivity, enhanced mechanical properties, and elevated interfacial energy to suppress the growth of metal dendrites. , Nevertheless, the structure of SEI can be regulated by molecules, functional groups, electrons, etc., but the complex process and high cost limit its commercial application.…”

Sustainable Fabrication of a Practical Hard Carbon Anode for a Sodium-Ion Battery with Unprecedented Long Cycle Life

“…As the temperature increases, the proportion of the C–O group gradually decreases and the proportion of the CO group gradually increases (Table S3), which is in line with the results of the peak division of C 1s. In previous work, oxygen groups have been studied to have electrochemical activity and can store sodium ions through surface redox reactions . Among them, CO functional groups have also been shown to improve the electrolyte affinity of HC anodes, making it possible to boost sodium-ion transport and stabilize the electrode/electrolyte interface .…”