Periodic Current Relaxation Mitigates Stress and Phase Instability in Single-Crystal Ni-Rich Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Single-crystal nickel-rich cathodes (SC-NCM) are crucial for high-energy-density lithium-ion batteries (LIBs).
• Current limitations include sluggish ion diffusion, stress, and phase instability during constant-current cycling.
• Existing modifications are complex and hinder scalability.

Purpose of the Study:

• To investigate the efficacy of a pulse-current (PC) cycling protocol for SC-NCMs.
• To demonstrate a simple, materials-independent method for enhancing LIB performance.
• To elucidate the relationship between electrochemical relaxation and structural stability.

Main Methods:

• Implementation of a pulse-current (PC) cycling protocol with periodic relaxation intervals.
• Electrochemical performance testing under various conditions (low temperature, high voltage, pouch cells).
• Advanced structural characterization techniques to analyze phase transitions and stress.

Main Results:

• PC cycling increased initial discharge capacity by 10.6% and improved long-term cycling stability.
• Homogenized ion distribution, enhanced Li+ kinetics, and stabilized phase transitions (H1-M, H2-H3).
• Suppressed rock-salt phase formation and reduced localized stress accumulation.
• Demonstrated robustness across practical operating conditions and in Ah-level pouch cells.

Conclusions:

• Periodic electrochemical relaxation via PC cycling is a simple, effective strategy for SC-NCMs.
• This method dynamically regulates ion transport and structural evolution, unlocking intrinsic cathode performance.
• Dynamic current modulation offers a broadly applicable approach without chemical modification.