Towards Advanced Sodium-Ion Batteries: Green, Low-Cost and High-Capacity Anode Compartment Encompassing Phosphorus/Carbon Nanocomposite as the Active Material and Aluminum as the Current Collector

Abstract

Sodium-ion batteries (SIBs) are promising alternative to Lithium-ion batteries for massive stationary energy storage. To improve energy density, however, more performing active materials are needed. In order to allow sustainable scale-up, it is also mandatory to develop green products and processes. Herein, we report on anodes of phosphorus/carbon (P/C) nanocomposites prepared via High Energy Ball Milling (HEBM), a simple, powerful and easily scalable synthesis technique. The electrodes were prepared under oxygen-free atmosphere, using water as solvent, which enabled the use of aluminum (instead of copper) as current collector, implying significant cost reduction. The P/C nanocomposite obtained after 54 hours HEBM resulted in excellent cycling stability, delivering very high specific capacity (2200 mAh g -1 , C/20) and showing good capacity retention after 120 cycles. A careful structural analysis (XRD, FESEM-EDS, XPS), revealed that long milling times strongly increased cycling stability due to: i) significant decrease of P particle size inside the matrix and deep composite amorphization, which alleviates the buffering dimensional issues typical of black phosphorus; ii) presence of defects in the carbonaceous component, which allows easier Na + insertion into the anode. Our results show that P/C nanocomposites are very promising anode materials for SIBs, paving the way for further exploitation of nano-architectures in SIBs technology.

Autonomous Self-Healing Strategy for Stable Sodium-Ion Battery: A Case Study of Black Phosphorus Anodes

“…In contrast, the capacity of the anode with a CMC−PAA binder abruptly drops to about 100 mA h g −1 after the first five cycles, corresponding to a capacity retention less than 10%, in agreement with what is generally observed for pure BP anodes. 6,46 The impressive stabilizing effects of the 50−50 SH binder is further confirmed when this anode is kept to rest for 48 h (see Figure 7a,c). Contrary to the anode with CMC−PAA, after the cycling breaks, the SH anode regains about 80% of the capacity lost during the first 25 cycles at 0.185 A h g −1 (increasing from 1000 mA h g −1 to 1500 mA h g −1 ).…”

“…Except for a slight increase of porosity, the cycled electrode does not reveal any significant structural degradation or reduction of adhesion with the current collector, which is still very good, contrary to what is observed in the case of CMC–PAA binders where post-mortem SEM-FIB/EDX revealed serious coating layer detachments from the Al foil, as already shown in our previous paper. 6 In addition, the cycled electrode thickness does not increase, confirming that such a binder prevents the BP anode from irreversible volume expansion thanks to its SH ability.…”

“…The BP mass loading in the anode was 1.26 and 1.6 mg cm –2 , respectively. Electrodes including different BP amounts were also investigated, namely, 2.5 mg cm –2 for B50–50 and 1 mg cm –2 , but no significant differences were observed in the electrochemical performances ( Figure S12 ad ref ( 6 )). On cycling, the first cycle discharge (desodiation) capacity is 2450 mA h g –1 at 0.18 A g –1 (corresponding to a cycling rate of C/20 based on the theoretical capacity of BP 1C = 2596 mA h g –13 ), very close to the theoretical one for both the anodes.…”

“…In contrast, the capacity of the anode with a CMC–PAA binder abruptly drops to about 100 mA h g –1 after the first five cycles, corresponding to a capacity retention less than 10%, in agreement with what is generally observed for pure BP anodes. 6 , 46 …”

“…BP was synthesized via high-energy ball milling, as deeply described elsewhere. 6 , 29 Raman spectra, SEM images, and XRD patterns of the as-prepared BP and the BP-C mixture used to prepare the anode slurry are reported in Figures S1–S3 , respectively. Two different binders were used: (i) the SH UPyPEG 795 UPy—PEO blend (50–50) and (ii) a blend of Na-CMC and PAA (1/1 wt/wt).…”