Degradation Effects in Li₄Ti₅O₁₂-Based Cells─Learning from Electrode Potential Profiles.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium titanate (Li4Ti5O12) is a key material for high-power lithium-ion batteries due to its stability and safety.
• Cyclic aging and gas evolution in Li4Ti5O12 cells hinder optimized design and longevity.
• Understanding these aging mechanisms is crucial for advancing battery technology.

Purpose of the Study:

• To investigate the cyclic aging behavior and gas evolution in LiNi1/3Co1/3Mn1/3O2 (NCM111)||Li4Ti5O12 (LTO) cells.
• To identify the primary causes of capacity fade and gas generation in LTO-based batteries.
• To explore strategies for mitigating capacity loss and improving cycle life.

Main Methods:

• Utilized a three-electrode setup for operando analysis of NCM111||LTO cells during cycling.
• Monitored electrode potential profiles and capacity changes over extended cycles.
• Investigated the impact of formation temperature on cell performance and aging.

Main Results:

• Observed an initial capacity increase followed by significant fade after 40 cycles, linked to lithium inventory loss and electrolyte consumption.
• Demonstrated that higher formation temperatures effectively suppress capacity decrease, lithium loss, and electrolyte consumption.
• Identified reductive decomposition of moisture and electrolyte at the LTO electrode surface as the major source of gas evolution.

Conclusions:

• The cyclic aging of LTO batteries is primarily driven by lithium inventory loss and electrolyte degradation, leading to capacity fade.
• Optimizing formation temperature is a viable strategy to enhance the stability and lifespan of LTO-based cells.
• Addressing moisture and electrolyte decomposition at the LTO electrode is critical for resolving gas evolution issues and improving battery safety and performance.