Introducing the Solvent Co‐Intercalation Mechanism for Hard Carbon with Ultrafast Sodium Storage

Abstract

et al. [13] found that the platform capacity of ball-milled carbon materials dropped sharply, which is consistent with graphite structural collapse in LIBs. Sun et al. [14,15] also proved the existence of an insertion reaction through in situ XRD experiments. Although a lot of studies have proven this model, some experimental phenomena still cannot be explained. Recently, Atsuo Yamada et al. [16] have explored in detail the sodium storage process of hard carbon by combining ex situ small and wide-angle X-ray scattering (SAXS/WAXS) techniques. The results show that the platform capacity is attributed to both insertion and nanopore filling mechanisms. Azusa Kamiyama et al. [17] synthesized a hard carbon material with abundant nanopores through the MgO template technology and an ultrahigh reversible capacity of 478 mAh g −1 was obtained. All these results indicate the principle of adsorption-embedded nanopore filling of hard carbon.Although many experiments and discussions have been conducted on the mechanism of hard carbon materials, the rate performance is still unsatisfactory. However, the previous results show that the co-intercalation of Na + and ether solvents have excellent rate performance with a graphite anode. Both Jache et al. [18] and Kim et al. [19] found that the capacity of the Na[solv] + (solvent solvated Na + ) embedded between graphite layers almost has no decay at different current densities. Sung Chul Jung et al. [20] used the DFT theoretical calculation method to reveal that the ternary Na-diglyme-GIC has a strong interlayer coupling strength. In addition, since Na + has a weaker interaction with diglyme, the diffusion rate of Na + -diglyme complex is 5 orders of magnitude faster than that of Li + -diglyme complex. Mustafa Goktas et al. [21] revealed that the introduction of the co-intercalation process makes this system an example of none SEI, which leads to rapid ion diffusion behavior.In this work, hard carbon fibers with self-supporting properties were prepared to eliminate the influences of binders and conductive agents. A solvent co-intercalation mechanism was introduced into the hard carbon sodium storage mechanism for the first time. In situ XRD and ex situ TEM XPS characterizations were performed to prove it. Introducing the co-intercalation of solvents enabled the hard carbon materials to exhibit 245 mAh g −1 at a current density of up to 5 A g −1 , which can maintain 72% of the one at 50 mA g −1 . The full battery assembled with Na 3 V 2 (PO 4 ) 3 had a high energy density of 157 Wh kg −1 at 3800 W kg −1 (relative to the electrode). It is worth noting that plateau capacity has hardly any decay at high current densities.As the most successful anode material for sodium-ion batteries, hard carbon has attracted extensive attention from researchers. However, its storage mechanism is still controversial. In this paper, a solvent co-intercalation mechanism into hard carbon is proposed and is proved by in situ XRD and ex situ TEM XPS results successfully. Thanks to the co-intercalation of sol...

Pore Structure Modification of Pitch‐Derived Hard Carbon for Enhanced Pore Filling Sodium Storage

“…In this stage, the kinetic bottleneck lies on the Na + diffusion between the graphitic layers, and a wider graphitic layer spacing favors the fast Na + diffusion. [ 35,36 ] Recently, Wu et al found that the solvent cointercalation mechanism of hard carbon in ether electrolytes can lead to an increase in the interlayer spacing of hard carbon, which in turn results in the significant improvement of sodium ion diffusion and kinetic performance, this result was consistent with the earlier analysis. [ 37 ] Besides, compounding hard carbon with other sodium storage materials with fast Na + diffusion may also improve its kinetic performance.…”

Combustion Activation Induced Solid‐State Synthesis for N, B Co‐Doped Carbon/Zinc Borate Anode with a Boosting of Sodium Storage Performance

“…Figure 6g,h and Figure S18 (Supporting Information) exhibit galvanostatic intermittent titration technique (GITT) potential profiles with a pulse current of 0.05 A g −1 for 0.5 h ( τ ), followed by a 1.0 h relaxation process and Na + diffusion coefficients calculated from Equation () [ 29–30,37,43 ] : $$$$\begin{equation}{{\rm{D}}}_{{\rm{Na}}^{\rm{ + }}}{\rm{ = }}\frac{{\rm{4}}}{{{\rm{\pi \tau }}}}{\left( {\frac{{{{\rm{m}}}_{\rm{B}} V_{\rm{m}}}}{{{{\rm{M}}}_{\rm{B}}{\rm{S}}}}} \right)}^{\rm{2}}{\left( {\frac{{\Delta {{\rm{E}}}_{\rm{S}}}}{{\Delta {{\rm{E}}}_{{\tau}}}}} \right)}^{\rm{2}}{\rm{,\tau }} \ll {{\rm{L}}}^{\rm{2}}{\rm{/}}{{\rm{D}}}_{{\rm{Na}}^{\rm{ + }}}\end{equation}$$$$…”

Surface-driven fast sodium storage enabled by Se-doped honeycomb-like macroporous carbon

“…3a, a strong broad characteristic peak located at about 211 is found in the XRD patterns of all Se-HMC samples, which belongs to the (002) crystalline plane of carbon materials. 30 In general, carbon materials with regular graphitic layers have sharp (002) peaks, while amorphous carbons with disordered carbon layers exhibit broad (002) peaks. It is clear that the Se-HMC samples are typical amorphous carbons.…”