Entropy-Driven Solvation toward Low-Temperature Sodium-Ion Batteries with Temperature-Adaptive Feature

Area of Science:

• Electrochemistry
• Materials Science
• Physical Chemistry

Background:

• Rechargeable battery performance degrades at low temperatures due to salt precipitation.
• Current understanding of design principles for low-temperature electrolytes is limited.
• Developing electrolytes that maintain stability and performance in cold conditions is crucial for applications like electric vehicles and grid storage.

Purpose of the Study:

• To address the challenge of salt precipitation in rechargeable batteries at low temperatures.
• To design a novel temperature-adaptive electrolyte with enhanced low-temperature performance.
• To investigate the role of solvation entropy in preventing salt precipitation.

Main Methods:

• Tuning the entropy of solvation in a strong-solvation (SS) and weak-solvation (WS) solvent mixture.
• Developing a temperature-adaptive electrolyte that avoids salt precipitation at low temperatures.
• Testing the performance of the developed electrolyte in a hard carbon||Na2/3Ni1/4Cu1/12Mn2/3O2 full cell at -40°C.

Main Results:

• The temperature-adaptive electrolyte demonstrated a spontaneous transformation of solvation structure at low temperatures, preventing salt precipitation.
• The hard carbon||Na2/3Ni1/4Cu1/12Mn2/3O2 full cell achieved 90.6% capacity retention over 400 cycles at -40°C.
• The concept was generalized to create a series of SS-WS electrolytes for low-temperature sodium-ion batteries.

Conclusions:

• Tuning solvation entropy is critical for designing effective low-temperature electrolytes.
• The developed SS-WS electrolytes offer a promising solution for high-performance rechargeable low-temperature sodium-ion batteries.
• This work provides a rational strategy for developing advanced electrolytes for extreme temperature conditions.