Greener Low-solvation Electrolyte Solvent Based Electrolyte Enables High-Efficiency Hard Carbon Anodes for Wide-Temperature Sodium-Ion Batteries

Energy Technology, IF = 3.6, Publication Date: 17-12-2025

DOI: https://doi.org/10.1002%2Fente.202500856

Authors: Nagmani, Dhrubajyoti Das, Sreeraj Puravankara

Article Title: Enhancing SEI Stability of Hard Carbon Anodes with Low‐Solvating CPME Co‐Solvent for Wide‐Temperature Sodium‐Ion Batteries

Research Overview:

Sodium-ion batteries (SIBs) are emerging as a sustainable and cost-effective alternative to lithium-ion batteries for large-scale energy storage. However, one of the major challenges limiting the commercialization of SIBs is the low initial Coulombic efficiency (ICE) and unstable solid-electrolyte interphase (SEI) formed on hard carbon (HC) anodes, especially under low-temperature operating conditions.

In this work, we demonstrate a greener electrolyte strategy by replacing the conventional ethylene carbonate (EC) co-solvent with cyclopentylmethyl ether (CPME), a weakly solvating and environmentally friendly solvent possessing a wide liquid-phase temperature range. The optimized CPME-PC electrolyte significantly improves electrochemical performance by regulating SEI chemistry and sodium-ion transport.

Key Innovations

First Report of CPME for Hard Carbon Sodium-Ion Batteries

This study reports, for the first time, the successful use of cyclopentylmethyl ether (CPME) as a co-solvent for hard carbon anodes in sodium-ion batteries, opening a new direction for greener electrolyte engineering.

Thin and Stable Inorganic SEI Formation

The weak solvation characteristics of CPME promote the formation of a thin, inorganic-rich, and highly stable SEI, unlike the thicker organic-rich SEI typically formed with EC-based electrolytes. This minimizes irreversible sodium consumption during the first cycle and enhances long-term cycling stability.

Enhanced Initial Coulombic Efficiency

The optimized electrolyte achieves an Initial Coulombic Efficiency (ICE) of up to 75%, substantially improving sodium utilization during the first charge-discharge cycle.

Higher Reversible Capacity

The hard carbon anode delivers a high reversible capacity of 356 mAh g⁻¹ at 30 mA g⁻¹, accompanied by a 68% low-voltage plateau capacity, indicating efficient sodium storage in closed pores.

Excellent Wide-Temperature Performance

The CPME-PC electrolyte exhibits outstanding electrochemical performance from room temperature down to 10°C and 0°C, providing:

Approximately 30% higher capacity than conventional EC-PC electrolyte
Improved ICE at low temperatures
Nearly 100% Coulombic efficiency during cycling
Excellent cycling stability even under cold operating conditions

Superior Long-Term Stability

Cells employing the CPME-PC electrolyte maintain 91% capacity retention after 100 cycles, demonstrating enhanced electrode-electrolyte compatibility and durable SEI formation.

Major Outcomes

Performance Parameter	Result
Electrolyte	CPME-PC (Greener Ether-Based)
Initial Coulombic Efficiency	Up to 75%
Reversible Capacity	356 mAh g⁻¹
Plateau Capacity Contribution	68%
Capacity Retention	91% after 100 cycles
Low-Temperature Improvement	~30% higher capacity
Coulombic Efficiency at 10°C & 0°C	Close to 100%

Why This Research Matters

The study demonstrates that electrolyte engineering can be as important as electrode design in improving sodium-ion battery performance. By employing a greener, weakly solvating ether solvent, the work successfully addresses two critical challenges of hard carbon anodes:

Low initial Coulombic efficiency
Poor low-temperature performance

These findings provide an effective strategy for developing high-performance, environmentally friendly sodium-ion batteries suitable for stationary energy storage and electric mobility operating across a wide temperature range.

Novel Contributions at a Glance

First demonstration of CPME as a co-solvent for hard carbon sodium-ion batteries.
Development of a green, weakly solvating electrolyte for sustainable battery technology.
Formation of a thin, inorganic-rich SEI that minimizes irreversible sodium loss.
Significant improvement in ICE, reversible capacity, and cycling stability.
Outstanding wide-temperature electrochemical performance, including operation at 10°C and 0°C.
Provides a practical electrolyte design strategy for next-generation sodium-ion batteries.

Potential Impact

This work advances the understanding of electrolyte–electrode interactions in sodium-ion batteries and establishes CPME-based electrolytes as a promising platform for next-generation, high-efficiency, and wide-temperature sodium-ion energy storage systems. The strategy offers a scalable pathway toward the commercialization of sustainable sodium-ion batteries with improved safety, efficiency, and environmental compatibility.

Dr. Nagmani

Search This Blog