Polymer-induced solid-electrolyte interphase on hard carbon enabling 5C fast-charging practical sodium-ion pouch cell

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Fast charging of sodium-ion batteries (SIBs) is hindered by parasitic reactions and unstable solid-electrolyte interphase (SEI) on hard carbon (HC) anodes.
• Developing stable interfaces is crucial for enhancing SIB performance and longevity.

Purpose of the Study:

• To develop a universal polymer-induced SEI strategy for enabling fast-charging SIBs.
• To investigate the role of functionalized polymer coatings in stabilizing the HC-electrolyte interface.

Main Methods:

• A functionalized polymer molecular layer, polyethylenesulfonyl fluoride (PESF), was coated onto the HC surface (PolyHC) to create a stable SEI.
• The PESF layer's polar -SO2F group was utilized to induce anion enrichment and tailor fluorine incorporation into the SEI.
• An Ah-level SIB pouch cell was assembled using a PolyHC anode and a NaNi1/3Fe1/3Mn1/3O2 cathode.

Main Results:

• The PESF coating resulted in a stable, approximately 5.0 nm SEI hybridizing polymer and NaF, minimizing electrolyte decomposition.
• The polymer skeleton effectively stabilized the inorganic SEI components, ensuring structural integrity during fast charging.
• The assembled 1.2 Ah pouch cell demonstrated exceptional fast-charging capability (under 10 minutes) and long-term durability.

Conclusions:

• The polymer-induced SEI strategy offers a universal approach to enhance the fast-charging performance and stability of SIBs.
• This method provides a novel perspective for interface engineering in hard carbon anodes for advanced energy storage applications.
• The compatibility with various HCs suggests broad applicability for next-generation sodium-ion battery technologies.