Salt engineering toward stable cation migration of Na metal anodes,Journal of Materials Chemistry A

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Salt engineering toward stable cation migration of Na metal anodes
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2022-11-15 , DOI: 10.1039/d2ta08187c
Yingying Ji ₁ , Hengchao Sun ₂ , Zhibin Li ₁ , Liang Ma _{1,

3} , Wanggang Zhang ₄ , Yiming Liu ₄ , Likun Pan ₅ , Wenjie Mai ₁ , Jinliang Li ₁

Affiliation

Na metal batteries (NMBs) have received extensive attention due to their high theoretical capacity and low electrochemical redox potential. However, dendrite growth and an unstable solid electrolyte interphase (SEI) layer in Na anodes limit the development of NMBs. In this work, we attempt to introduce potassium bis(fluorosulfonyl)imide (KFSI) as an NMB salt additive in electrolyte and find that this KFSI-containing electrolyte can enable highly reversible and nondendritic plating–stripping of Na metal anodes. Excellent cycling stability for 400 h at 0.5 mA cm⁻² in a Na‖Na symmetric cell and a high coulombic efficiency of 97.7% after 200 cycles in a Na‖carbon cloth (CC) asymmetric cell can be achieved in KFSI containing electrolyte. From our results, we find that K-ions from KFSI can show electrostatic shielding on the tip of the dendrite and then guide the uniform deposition of Na ions due to the lower potential of the K/K⁺ couple (−2.93 V vs. the standard hydrogen electrode (SHE)) compared with that of the Na/Na⁺ couple (−2.71 V vs. SHE). In addition, the S–F bond cleavage from the FSI anion presents low dissociation energy of S–F from density functional theory calculation, contributing to the formation of a stable fluoride (NaF and KF) rich solid electrolyte interfacial layer on the Na anode surface, which is also in favor of a tough Na plating–stripping process. We believe our findings will guide salt engineering to enhance the electrochemical performance of the Na metal anode.

中文翻译：

钠金属阳极稳定阳离子迁移的盐工程

钠金属电池（NMB）由于其高理论容量和低电化学氧化还原电位而受到广泛关注。然而，Na 负极中的枝晶生长和不稳定的固体电解质界面 (SEI) 层限制了 NMB 的发展。在这项工作中，我们尝试在电解质中引入双（氟磺酰基）亚胺钾（KFSI）作为 NMB 盐添加剂，并发现这种含有 KFSI 的电解质可以实现钠金属阳极的高度可逆和非树枝状电镀-剥离。^{在 0.5 mA cm −2}下 400 小时的出色循环稳定性在 Na‖Na 对称电池中，在含有 KFSI 的电解质中，在 Na‖碳布（CC）不对称电池中经过 200 次循环后，库仑效率高达 97.7%。从我们的结果中，我们发现来自 KFSI 的 K 离子可以在枝晶尖端显示静电屏蔽，然后由于 K/K ⁺电势较低（−2.93 V vs.标准氢电极 (SHE)）与 Na/Na ⁺电偶（−2.71 V vs.她）。此外，FSI 阴离子的 S-F 键裂解从密度泛函理论计算中呈现出 S-F 的低解离能，有助于在 Na 阳极表面形成稳定的富含氟化物（NaF 和 KF）的固体电解质界面层，这也有利于坚韧的 Na 电镀-剥离工艺。我们相信我们的发现将指导盐工程提高钠金属阳极的电化学性能。

更新日期：2022-11-15

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