Deciphering Electrolyte Dominated Na⁺ Storage Mechanisms in Hard Carbon Anodes for Sodium‐Ion Batteries

Abstract

Although hard carbon (HC) demonstrates superior initial Coulombic efficiency, cycling durability, and rate capability in ether‐based electrolytes compared to ester‐based electrolytes for sodium‐ion batteries (SIBs), the underlying mechanisms responsible for these disparities remain largely unexplored. Herein, ex situ electron paramagnetic resonance (EPR) spectra and in situ Raman spectroscopy are combined to investigate the Na storage mechanism of HC under different electrolytes. Through deconvolving the EPR signals of Na in HC, quasi‐metallic‐Na is successfully differentiated from adsorbed‐Na. By monitoring the evolution of different Na species during the charging/discharging process, it is found that the initial adsorbed‐Na in HC with ether‐based electrolytes can be effectively transformed into intercalated‐Na in the plateau region. However, this transformation is obstructed in ester‐based electrolytes, leading to the predominant storage of Na in HC as adsorbed‐Na and pore‐filled‐Na. Furthermore, the intercalated‐Na in HC within the ether‐based electrolytes contributes to the formation of a uniform, dense, and stable solid–electrolyte interphase (SEI) film and eventually enhances the electrochemical performance of HC. This work successfully deciphers the electrolyte‐dominated Na+ storage mechanisms in HC and provides fundamental insights into the industrialization of HC in SIBs.

Revealing the Na storage behavior of graphite anodes in low-concentration imidazole-based electrolytes

“…4c and e), which may be related to the different thickness of the SEI layer formed. 42,43 The CV curves of 0.2-Prlm and 0.2-Bulm were similar to those of 0.2-Melm (Fig. 4d and f), signifying the occurrence of intercalation and deintercalation reactions of solvated sodium ions.…”

Modulating the graphitic domains of hard carbons via tuning resin crosslinking degree to achieve high rate and stable sodium storage

“…However, the low reserves and high cost of lithium, along with the unsafety, impede their usage in large-scale energy storage systems [2] . Sodiumion batteries (SIBs), which show similar chemistry to LIBs while being much cheaper, are deemed one of the most promising next-generation energy storage techniques to replace LIBs [3] . Among the various advanced SIB anode materials, hard carbons (HCs) stand out as promising candidates for commercial SIBs by virtue of the abundant active sites for Na + storage [1] , wide sources, and low cost [2] .…”

Preparation of Enriched Closed-Pores Hard Carbon for High-Performance Sodium-Ion Batteries by the Poly(vinyl butyral) Template Method

“…The results indicate that a significant number of quasi-metallic Na formed below 0.1 V. Electron paramagnetic resonance (EPR) technology is highly sensitive to the detection of unpaired electrons. It is widely used in compound anodes and electrolyte for sodium-ion batteries, , and graphite anodes for lithium-ion batteries . As shown in Figure d.…”