Key Findings
A research team led by Professor Chan-Jin Park at Chonnam National University has developed a PDES-1 electrolyte that allows a sodium metal battery full cell to maintain 90.4% of its initial capacity after 1,000 cycles at a 2C rate. In a sodium symmetric cell, the electrolyte demonstrated stable plating and stripping for over 1,000 hours. Additionally, the PDES-1 electrolyte exhibited an ionic conductivity of 1.39 mS/cm at 30°C and a sodium-ion transference number of 0.58, which is higher than the 0.2–0.4 typically found in liquid electrolytes.
Technical Details
The PDES-1 electrolyte consists of three components: sodium perchlorate (NaClO4), N-isopropylacrylamide (NIPAM) as a polymerizable monomer, and succinonitrile (SN) as a plasticizer. The team utilized “in-situ polymerization,” where the liquid deep eutectic solvent is injected into the cell and then thermally polymerized into a flexible polymer matrix. This approach ensures better contact with the electrode surface compared to pre-solidified electrolytes.
- Electrochemical Stability: The electrolyte demonstrated a wide potential window of 5.0 V.
- Rate Performance: In a full cell using a sodium vanadium phosphate (Na3V2(PO4)3) cathode, the discharge capacity was 110.2 mAh/g at 0.1C and remained at 90 mAh/g even at a 5C rate.
- Safety: The polymer matrix is non-flammable and resists leakage. In pouch cell demonstrations, the battery continued to power an LED even after being folded or cut with scissors.
Background and Significance
Sodium metal batteries are targeted for higher energy density than standard sodium-ion batteries by replacing hard carbon anodes with metallic sodium. However, metallic sodium is highly reactive and prone to dendrite growth, which can cause short circuits. The PDES-1 design mitigates these issues by forming a stable interface layer that suppresses non-uniform sodium deposition.
Outlook and Challenges
While promising for energy storage systems (ESS) and backup power, the study was limited to laboratory-scale coin and pouch cells. Future validation is required for large-scale cells, specifically regarding the uniformity of electrolyte penetration in thick electrodes, the minimum required electrolyte volume, and safety evaluations based on international industrial standards.
Source: https://xenospectrum.com/polymer-electrolyte-sodium-metal-battery-durability/
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