Quantitative Analysis of Sodium Metal Deposition and Interphase in Na Metal Batteries

TL;DR

This paper investigates sodium metal deposition and interphase formation in sodium-ion batteries, employing titration gas chromatography and pressure control to enhance sodium anode stability, capacity retention, and cycling performance.

Contribution

It introduces a method to quantify sodium loss and demonstrates pressure-controlled deposition to improve sodium anode stability and performance in sodium-ion batteries.

Findings

Sodium inventory loss quantified accurately using titration gas chromatography.

Uniaxial pressure yields dense sodium deposits with high initial coulombic efficiency.

Full cell retains 91.84% capacity after 500 cycles at 2C.

Abstract

Sodium-ion batteries exhibit significant promise as a viable alternative to current lithium-ion technologies owing to their sustainability, low cost per energy density, reliability, and safety. Despite recent advancements in cathode materials for this category of energy storage systems, the primary challenge in realizing practical applications of sodium-ion systems is the absence of an anode system with high energy density and durability. Although Na metal is the ultimate anode that can facilitate high-energy sodium-ion batteries, its use remains limited due to safety concerns and the high-capacity loss associated with the high reactivity of Na metal. In this study, titration gas chromatography is employed to accurately quantify the sodium inventory loss in ether- and carbonate-based electrolytes. Uniaxial pressure is developed as a powerful tool to control the deposition of sodium metal with dense morphology, thereby enabling high initial coulombic efficiencies. In ether-based electrolytes, the Na metal surface exhibits the presence of a uniform solid electrolyte interphase layer, primarily characterized by favorable inorganic chemical components with close-packed structures. The full cell, utilizing a controlled electroplated sodium metal in ether-based electrolyte, provides capacity retention of 91.84% after 500 cycles at 2C current rate and delivers 86 mAh/g discharge capacity at 45C current rate, suggesting the potential to enable Na metal in the next generation of sodium-ion technologies with specifications close to practical requirements.