Hard Carbon–Sulfide Solid Electrolyte Interface in All-Solid-State Sodium Batteries

Abstract

Hard carbon is a promising negative electrode material for sodium-ion batteries that operate at low potentials. However, reversible and high-capacity charging and discharging in all-solid-state sodium batteries with hard carbon electrodes using sulfide solid electrolytes have not been reported. This study reports that reductive decomposition of the sulfide solid electrolyte occurs at both the negative composite electrode and the interface between the negative electrode layer and the solid electrolyte layer. In the first cycle, the all-solid-state cell with a composite electrode containing a Na3PS4 solid electrolyte exhibited a large irreversible capacity of 561 mAh g −1 because of the reductive decomposition of Na3PS4 to Na2S and Na3P. The use of a Na3BS3 glass electrolyte with reduction stability can lead to the successful charging and discharging of all-solid-state cell that utilizes hard carbon. This glass electrolyte can serve as a solid electrolyte for the negative composite electrode and as a buffer layer between the negative electrode layer and the solid electrolyte layer. Hence, it can also help suppress the irreversible capacity of the cell to 122 mAh g −1 .

On the influence of the coherence length on the ionic conductivity in mechanochemically synthesized sodium-conducting halides, Na3−xIn1−xZrxCl6

“…The structure and transport properties of ball milled Na 3 InCl 6 have been discussed in-depth in previous reports. 30,32 Meanwhile, ball milled Na 2 ZrCl 6 is a phase mixture of the trigonal and monoclinic polymorphs, 32 which makes it difficult to distinguish the contributions of each phase. Hence in this work, we focus on the cation-mixed Na 3−x In 1−x Zr x Cl 6 solid solutions only, excluding the endmembers from the discussion.…”

“…Compounds of nominal Na 3−x In 1−x Zr x Cl 6 (0.1 # x # 0.95) were successfully synthesized by ball milling. 32 An additional smaller step composition (i.e. x = 0.95) was included to push the series closer to the Na 2 ZrCl 6 endmember.…”

“…30 To develop more conductive sodium halides, Zr 4+ was introduced in Na 3 InCl 6 and both via ball milling and also by subsequent annealing. 31,32 However, it is interesting that the trend of ionic conductivity as a function of the Zr content is different between the series of Na 3−x In 1−x Zr x Cl 6 (0.1 # x # 0.9) with and without subsequent annealing, even though both adopt the monoclinic polymorph (space group P2 1 /n). For the subsequently annealed Na 3−x In 1−x Zr x Cl 6 series, the intermediate substituted Na 2.5 In 0.5 Zr 0.5 Cl 6 shows the highest ionic conductivity, which is analogous with the Na 3−x Y 1−x Zr x Cl 6 and Na 3−x Er 1−x Zr x Cl 6 series of solid solutions.…”

NaTaCl6: Chloride as the End-Member of Sodium-Ion Conductors

“…In general, aliovalent substitution is a typical strategy for increasing the conductivity. The substitution of Zr 4+ for In 3+ in the Na 3 InCl 6 end-member increases the ionic conductivity to 10 –5 S cm –1 . Thus, finding suitable end-members is important for the development of solid electrolytes with high conductivity and oxidation stability.…”

“…The substitution of Zr 4+ for In 3+ in the Na 3 InCl 6 end-member increases the ionic conductivity to 10 −5 S cm −1 . 29 Thus, finding suitable end-members is important for the development of solid electrolytes with high conductivity and oxidation stability. Computational science offers a new material Na 3 MCl 6 with high ionic conductivity and electrochemical stability.…”