Stable Sodium Metal Batteries via Manipulation of Electrolyte Solvation Structure

Abstract

ion batteries (LIBs), which significantly hinders the technology adoption rate. The energy density of SIBs is greatly limited by the anode material, [10] for example, the conventional anode, hard carbon, can only provide a specific capacity of ≈250 mAh g −1 . Sodium metal is an ideal alternative of the anode materials for SIBs due to its relatively high theoretical specific capacity (1166 mAh g −1 ) and low redox potential (−2.71 V vs the standard hydrogen electrode). [11][12][13][14][15] Typical sodium metal batteries, such as sodium-sulfur and sodium-oxygen batteries, have ultrahigh theoretical energy densities of 1274 and 1605 Wh kg −1 , respectively, which are 10 times higher than that of the SIBs (120 Wh kg −1 ). [16][17][18][19][20][21][22][23] Applications of Li metal anode have been hindered by the scarcity and uneven distribution of Li resource. Benefiting from the wide distribution of Na resource, it is possible to design high power, high energy density and low-cost sodium-based batteries by "enhanced cathode materials," [24] "electrolyte design" [25] and sodium metal anode protection.Although the sodium metal anode holds promising potential for providing high energy density, its practical applications are encountered with several essential challenges, such as dendritic growth and side reactions, thus leading to serious safety issues and short battery life. To overcome these problems, tremendous efforts have been devoted to suppressing the sodium dendrite growth and enhancing the Coulombic efficiency (CE) of sodium metal anode. A variety of strategies have been proposed to improve the reversibility and cycling stability, including the utilization of 3D current collectors, manipulation of artificial solid-electrolyte interphase (SEI) and development of stable electrolyte solvation structure. For example, the 3D metal skeletons, [26,27] carbon-based materials, [28][29][30][31][32] and pillared Mxene [33] have been used as current collectors for sodium metal anode, which successfully change the sodium plating/stripping behaviors and achieve better cycling performances by reducing the local current densities at the electrode surface. However, the direct consequences for using 3D current collectors include the introduction of voids and additional weight of inactive materials and the sacrifice of the first cycle CE caused by increased anode surface area. The utilization of artificial SEI is another common strategy to physically suppress the Na dendrite and increase the CE of sodium anode. [34][35][36][37][38][39] Nevertheless, it is still challenging to design suitable artificial SEI because of the large size of the Sodium metal batteries have attracted rapidly rising attention due to their low cost and high energy densities. However, the instability and low efficiency of metallic sodium anodes pose significant concerns for their practical applications. Here a highly stable sodium metal anode enabled by an etherbased electrolyte is reported, which exhibits a long-term stable cycling up to 400 cycles and achie...

Molecularly Compensated Pre‐Metallation Strategy for Metal‐Ion Batteries and Capacitors

“…[31] Meanwhile,e x-situ XPS measurements have been carried out for further detecting the composition changes of APC/AC-Na cathodes in details.The Na 1s high-resolution spectrum is shifted left to higher binding energy,which reveals that the C-ONa group has been transformed into of Na + ion (Figure 6f). [32] As confirmed in C 1s and O1shigh-resolution spectra after Gaussian fitting,the desodiation process could also be verified due to the sharply decreased percentage contents of C=Oa nd O=CÀOs pecies after cycling (Figure 6g and h). Meanwhile,the solid electrolyte interphase (SEI) film has been formed on the surface of NHPC-800 anode after the cycling as seem from SEM images, implying that the pre-sodiation process of NHPC-800 anode could be accomplished triggered by the Na source originated from AC-Na ingredient (Figure 6i).…”

Sodiophilically Graded Gold Coating on Carbon Skeletons for Highly Stable Sodium Metal Anodes

“…[3,7,8] In fact, all these issues are interrelated and lower the coulombic efficiency (CE), trigger serious safety hazards, and are ultimately responsible for the short lifespan of NMBs. [7,9,10] Many efforts have been directed to circumventing these challenges, including the optimization of electrolyte composition, [11][12][13] the construction of artificial SEI layers, [14][15][16] the modulation of morphology/structure of current collectors and hosts, [17][18][19][20][21][22][23][24] the building of interlayers, [10,25] and the use of solidstate electrolytes. [26,27] Among these options, plating Na metal in 3D hosts is an effective approach not only to accommodate the large volume change of Na metal during plating and stripping but also to reduce the local current densities, thus mitigating the Na dendrite growth and reversibility issues.…”

Solid Electrolyte Interphases on Sodium Metal Anodes

“…[65,66] Recently, Wang et al reported a state-of-the-art electrolyte containing NaBF 4 salt and diglyme solvent, which achieved an unprecedentedly high average CE of 99.93% over 400 cycles for stable Na metal anodes. [67] The B-O species with high ion conductivity work as a strong binder to tightly connect the inorganic components in the inner SEI part and the organic polymer in the top layer, which can lead to a continuous and flexible SEI layer. [68,69] Furthermore, a NaBF 4 -based electrolyte using another solvent (tetraglyme) exhibited an excellent cycling efficiency (99.9%) of a Na metal anode for over 1000 cycles.…”

“…Hence, the precursor concentration and reaction time should be precisely tuned to achieve ideal protection. Recently, various Na 3 PS 4 (NaPS) protective layers were fabricated by controlling the experimental design parameters, as illustrated in Ether-based electrolytes 1 m NaPF 6 in diglyme -0.5 mA cm −2 ; 1 mA h cm −2 99.9%/300 cycles 2015 [64] 0.5% NaFSI in DME -0.2 mA cm −2 ; 0.5 mA h cm −2 97.7%/250 cycles 2017 [73] 0.5 m NaBF 4 in diglyme -0.5 mA cm −2 ; 1 mA h cm −2 99.93%/400 cycles 2020 [67] 1 m NaBF 4 in TEGDME -0.5 mA cm −2 ; 0.5 mA h cm −2 99.9%/1000 cycles 2020 [70] 0.1 m NaBPh 4 in DME -0.5 mA cm −2 ; 0.5 mA h cm −2 99.85%/300 cycles 2019 [43] Additives 1 m NaClO 4 in EC/PC/FEC 5 wt% FEC 1 mA cm −2 ; 1 mA h cm −2 100 h 2018 [56] 1 m NaPF 6 in DME/FEC/TMP 40 vol% HFPM 1 mA cm −2 ; 1 mA h cm −2 800 h 2019 [86] 2 m NaTFSI in TMP/FEC 30 vol% FEC 0.3 mA cm −2 ; 0.3 mA h cm −2 1000 h 2019 [85] 1 m NaPF 6 in diglyme/Na 2 S 6 0.033 m Na 2 S 6 10 mA cm −2 ; 5 mA h cm −2 100 h 2018 [87] 1 m NaTFSI in FEC/NaAsF 6 0.75 wt% NaAsF 6 0.1 mA cm −2 ; 0.5 mA h cm −2 97%/400 cycles 2019 [95] 1 m NaClO 4 in EC/DEC/SnCl 2 50 × 10 −3 m SnCl 2 0.5 mA cm −2 ; 1 mA h cm −2 500 h 2019 [96] 4 m NaFSI in DME/SbF 3 1% SbF 3 0.5 mA cm −2 ; 0.5 mA h cm −2 1000 h 2020 [210] 0.8 m LiPF 6 , 1 m NaPF 6 in DME 0.8 m LiPF 6 0.2 mA cm −2 ; 0.2 mA h cm −2 99.2%/100 cycles 2018 [93] 1 m NaOTf in TEGDME/KTFSI 0.01 m KTFSI 0.5 mA cm −2 ; 1 mA h cm −2 99.5%/300 cycles 2018 [94] 0.5 m NaOTf in diglyme/DCAD 1.0 mg mL −1 DCAD 0.356 mA cm −2 ; 0.2 mA h cm −2 100 cycles 2020 [211] Concentration effects 4 m NaFSI in DME -1 mA cm −2 ; 1 mA h cm −2 99%/300 cycles 2016 [71] 2.5 m NaCF 3 SO 3 in diglyme -2 mA cm −2 ; 1 mA h cm −2 100 h 2019 [102] 5 m NaFSI in DME -0.0028 mA cm −2 ; 0.0014 mA h cm −2 600 h 2017 [103] 2.1 m NaFSI in DME/BTFE -1 mA cm −2 ; 1 mA h cm −2 98.95%/400 cycles 2018 [108] Ionic liquids Buffered Na-Cl-IL -0.5 mA cm −2 ; 0.25 mA h cm −2 95%/100 cycles 2019 [60] NaAlCl 4 • 2SO 2 -0.75 mA cm −2 ; 1.5 mA h cm −2 95 cycles 2015 [135] NaBF 4 -2.5NH 3 -10 mA cm −2 ; -100 cycles 2017 [138] a) Reproduced with permission. [139] Copyright 2019, Wiley.…”