Creasable Batteries: Understanding Failure Modes through Dynamic Electrochemical Mechanical Testing.

Area of Science:

• Materials Science
• Electrochemistry
• Mechanical Engineering

Background:

• Flexible electronics require energy storage solutions that withstand mechanical stress.
• Traditional thin-film batteries often fail under bending or creasing due to brittle current collectors.
• Developing robust current collectors is crucial for durable flexible batteries.

Purpose of the Study:

• To evaluate the mechanical and electrochemical performance of flexible thin-film batteries with different current collectors.
• To demonstrate the benefits of using multiwalled carbon nanotube mats as current collectors.
• To quantify the improvements in durability and stability under mechanical strain.

Main Methods:

• Fabrication of thin-film Li-ion batteries (Li4Ti5O12//LiFePO4) using multiwalled carbon nanotube (MWNT) mats and traditional metal foil as current collectors (CCs).
• Systematic evaluation using dynamic mechanical testing for controlled bending and creasing.
• Electrochemical performance testing under various mechanical deformation conditions.

Main Results:

• MWNT-based CCs significantly reduced voltage fluctuation (14-fold) under 4.2% bending strain compared to metal foils.
• MWNT-based full-cells maintained integrity through 288 crease cycles.
• Metal foil CCs showed continuous performance degradation and catastrophic fracture after 94 folds.

Conclusions:

• M Wall-woven carbon nanotube mats provide superior mechanical robustness and flexibility for thin-film batteries.
• The MWNT CCs enhance interfacial properties, mechanical strength, and compliancy, improving stability during mechanical stress.
• Utilizing appropriate flexible current collectors enables substantial improvements in both mechanical and electrochemical stability for foldable batteries.