Tea‐Derived Sustainable Materials

Abstract

The practical application of hard carbon in sodium‐ion batteries is limited by insufficient reversible capacity and low initial Coulombic efficiency (ICE), which are caused by the lack of active sites and unstable electrode/electrolyte interface. Herein, a biomass‐derived hard carbon material based on tea stems is proposed, which exhibits an ultrahigh ICE of 90.8%. This remarkable ICE is attributed to the presence of an inorganic‐rich, thin, and robust solid electrolyte interface (SEI) layer. Furthermore, the material demonstrates excellent cycling stability, showing a capacity retention of 99.5% after 500 cycles at 280 mA g−1. Additionally, when it works as the anode material in a sodium‐ion full cell without presodiation, it reaches a high energy density of 212 Wh kg−1 and a superior stability, e.g., retaining 93.1 mAh g−1 after 1000 cycles at 1 A g−1 with a capacity retention of 91.3%. The sodium storage capacity of this material is primarily attributed to a combined adsorption‐intercalation/filling effect as confirmed by in situ XRD and ex situ Raman analyses. These findings make this biomass‐derived hard carbon material a promising candidate for commercial application of sodium‐ion batteries, achieving high performance at low cost.

Simultaneously enabling superior ICE and high rate/cycling stability with a hollow carbon nanosphere anode for sodium-ion storage

“…Thus, HCs represent one of the most commercializable anode candidates. 2,7,8 Considerable progress has been dedicated to designing defects and functional groups and constructing porous nanoarchitectures to expedite transport/diffusion kinetics, dominated by high-potential regions, thus enabling outstanding cycling stability and rate performance. 9–12 Unfortunately, their ICE is rather poor (<60%), 13–15 mainly due to the irreversible loss of active Na ions catalysed by defects and high surface areas.…”

Heteroatom doping-induced formation of closed pores for high-performance sodium storage hard carbon anodes

“…The transfer of electrons from Na + to the antibonding orbitals of carbon atoms implies, in layman's terms, that Na + diffused into a suitable closed pore and reacted with sp 2 carbon, which in turn affected the telescopic vibrations on the sp 2 hybridisation surface of the carbon, resulting in a shift of the G band, further suggesting that the storage of Na + is the result of a combination of intercalation-type and surface diffusion. 23,25,26 The ex situ XPS spectra of Na 1s are shown in Fig. 3c.…”

“…Specifically, the diffusion coefficient of 1.0 M NaPF 6 is 1.15 × 10 −5 cm 2 ps −1 at 298 K, which is similar to previously reported results. 25 To evaluate the application potential of the CDRTF anode in the SICs, a full battery was assembled using electrochemically pre-sodiumized CDRTF as the anode and commercial AC (YP-50F) as the cathode (Fig. S23 and S24, ESI†).…”