Surface Potential Regulation Realizing Stable Sodium/Na₃Zr₂Si₂PO₁₂ Interface for Room‐Temperature Sodium Metal Batteries

Abstract

Inorganic Na3Zr2Si2PO12 is prospective with a high ionic conductivity but suffers large interfacial resistance and stability issues against sodium metal, hindering its practical application in all‐solid‐state sodium batteries. A surface potential regulation strategy is adopted to address these issues. Na3Zr2Si2PO12 (NZSP) ceramic with homogeneously‐sintered surface is synthesized by a simple two‐step sintering method to promote its uniform surface potential, which is favorable for mitigating the potential fluctuations at the interface against Na metal and enhancing interfacial compatibility. The Na/NZSP interface can be stabilized for over 4 months with a low interfacial resistance of 129 Ω cm2 at 25 °C. The symmetrical Na/NZSP/Na cell exhibits ultra‐stable sodium platting/stripping cycling for over 1000 cycles under 0.1 mA cm−2. Superior interfacial performance is well retained even under 0.2 mA cm−2 at room temperature. The robust interface is further signified by its excellence under higher current densities of up to 0.85 mA cm−2 at 60 °C. A 4 V all‐solid‐state Na3V1.5Cr0.5(PO4)3/NZSP/Na metal battery is demonstrated at ambient conditions, which exhibits superior rate capability and delivers a high reversible capacity of 103 mA h g−1 under 100 mA g−1 for over 400 cycles with a Coulombic efficiency of over 99%.

Uniform Na Metal Plating/Stripping Design for Highly Reversible Solid‐State Na Metal Batteries at Room Temperature

“…After that, steady and small voltages of around 35 mV are maintained even until the cycling time reaches 5000 h. In sharp comparison, the Na|NZSPO|Na cell exhibits a large Na metal stripping overpotential of over 3.5 V versus Na + /Na and short circuit occurs after the first charge only for 1 h (Figure S7, Supporting Information). Furthermore, as shown in Figure 4h, the excellent performance of the CuO@NZSPO solid electrolyte surpasses those of the previously reported NZSPO-based solid electrolytes, [20,21,30,31,[48][49][50][51] such as the Na-deficient NZSPO, [50] TiO 2 coated NZSPO, [22] SnO 2 modified NZSPO, [30,31] and GBS-NZSPO. [47] A solid-state Na metal full battery was assembled to examine the practical application of CuO@NZSPO as an advanced solid electrolyte.…”

“…The main diffraction peaks of the NZSPO are indexed to a monoclinic Na 3 Zr 2 Si 2 PO 12 structure reported by previous literature. [21,43,44] Minor diffraction peaks at 2θ = 24.40°, 28.15°, 31.44° are assigned to a monoclinic ZrO 2 phase (ICSD#85243) resulting from sodium volatilization at high temperature. [34,45,46] For CuO@NZSPO, additional diffraction peaks appear at 2θ = 32.58°, 35.57°, 38.86°, 48.71°, which correspond to the (110), (−111), (111), (−202) planes of a monoclinic CuO phase (ICSD#92346), respectively.…”

“…[13,14] Researchers have proposed various methods to boost the robust solid electrolyte/Li or Na metal interface for reduced interfacial impedance, improved critical current densities, and long-term cycling stability. [15][16][17][18][19][20][21] Among them, surface modification of the solid electrolyte proves one of the most effective ways as it introduces an active interphase to mitigate the difference between the alkaline metal and the solid electrolyte. [17,22] Functional coatings including…”

Solid‐State Na Metal Batteries with Superior Cycling Stability Enabled by Ferroelectric Enhanced Na/Na3Zr2Si2PO12 Interface

“…With respect to Na/NZSP/Na symmetrical cell, an obviously increased resistance is observed (Figure S7, Supporting Information), which is identical to previous research. [15,16,29] Owing to the improved Na + conductivity of ceramic electrolyte and charge transfer capability at the interface, the total resistance of Na/NZSP-3BTO/Na symmetrical cell is apparently decreased with the increasing temperature (Figure 2d); the total resistance at 50 °C is only 135 ohm. The activation energy for Na ion transfer of the Na/NZSP-3BTO interface is about 0.39 eV, which is much smaller than ≈0.6 eV of the Na/NZSP interface.…”

Metallic Sodium Anodes for Advanced Sodium Metal Batteries: Progress, Challenges and Perspective

“…ISEs under development generally contain numerous inorganic oxides and nonoxides with amorphous or crystalline structures, including NASICON type Na 3 Zr 2 Si 2 PO 12 (NZSP), [188,189,[197][198][199][200] β-Al 2 O 3 , [201][202][203][204][205] Na 3 SbS 4 . [206][207][208] Despite some success, new problems have arisen from these electrolytes with low IC and large interfacial resistance in Na-based batteries.…”