Lactone Electrolytes for 4.5 V Sodium-Ion Batteries Show High-Voltage Advantages, Yet Face Ionic Conductivity and SEI Stability Challenges

July 5, 2026

ACS Energy Letters Unknown

Overview

Lactone electrolytes, widely used in solid polymer electrolytes for sodium-ion batteries, show clear advantages in high-voltage operation but are noted for low ionic conductivity and forming unstable solid electrolyte interphases (SEI). These challenges hinder performance improvement and practical application of sodium-ion batteries, necessitating solutions through future R&D.

In Depth

Key Findings

Research on lactone electrolytes, widely utilized in solid polymer electrolytes for sodium-ion batteries (SIBs), confirmed their clear advantages in high-voltage operation. However, significant challenges such as low ionic conductivity and a propensity to form unstable solid electrolyte interphases (SEI) were simultaneously highlighted, indicating these issues as bottlenecks for performance enhancement and practical application.

Technical Details

Lactone compounds have garnered attention as solvents for polymer and liquid electrolytes in sodium-ion batteries due to their polarity and relatively high boiling points. They offer the specific advantage of excellent compatibility with high-voltage cathode materials, enabling high-voltage battery operation, which is expected to boost battery energy density. However, this study points out that the ionic conductivity of lactone electrolytes is not sufficiently high, constrained by the mobility of Na ions due to their molecular structure. Furthermore, these electrolytes tend to form unstable SEI layers at the sodium metal anode interface. An unstable SEI can promote dendrite growth, potentially compromising battery safety and cycle life. The research also suggests that ring-size dependency (the size of the molecular ring) influences ionic conductivity and interfacial reactions, emphasizing the importance of molecular design.

Background & Context

Driven by concerns over lithium resource scarcity, price volatility, and supply chain risks, active research and development are underway for sodium-ion batteries as a promising alternative to lithium-ion batteries. All-solid-state sodium-ion batteries, particularly those employing solid polymer electrolytes, are anticipated as next-generation batteries that balance safety and energy density. However, because sodium ions are larger than lithium ions, their movement within solid electrolytes is more challenging, making the achievement of high ionic conductivity a major hurdle. The challenges identified in lactone electrolytes suggest that optimization of material design and interface engineering are key to the practical application of all-solid-state sodium-ion batteries.

Strategic Significance & Outlook

To address the ionic conductivity and SEI stability challenges in lactone electrolytes, future research will focus on introducing new additives, developing composite electrolytes, and precise engineering of the electrolyte-electrode interface. Specifically, achieving high-performance all-solid-state sodium-ion batteries requires simultaneously enhancing ion transport efficiency and interfacial stability through molecular-level design. If these challenges are overcome, sodium-ion batteries are expected to play a significant role as a sustainable and cost-effective energy storage solution in stationary energy storage systems and certain EV markets.

Source: https://pubs.acs.org/doi/10.1021/acsenergylett.6c00918

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