Lithium iron phosphate (LiFePO₄, LFP) is already recognized as a cathode material in lithium-ion batteries due to its excellent electrochemical stability, intrinsic safety, non-toxicity, and low cost. Beyond its established role in commercial battery systems, LFP is increasingly being explored as a reference electrode material for non-aqueous lithium-based electrochemical measurements because of its stable and well-defined electrode potential.
In this work, we demonstrate that chemically partially delithiated LiFePO₄ (modified LFP) can serve as a stable, reliable, and safe alternative to metallic lithium reference electrodes. Through controlled chemical delithiation, the electrode potential is set to 3.420 V vs. Li, providing a reproducible reference without the need for in-situ electrochemical conditioning after cell assembly. The uncertainty is less than 5 mV over 1000 hours of cycling.
The modified LFP reference electrode exhibits excellent long-term potential stability and avoids common issues associated with lithium metal, such as parasitic side reactions and possible dendrite formation that result in voltage spikes. As a result, it improves both the safety and accuracy of electrochemical experiments while maintaining high reproducibility across measurements.
The use of chemically delithiated LFP expands experimental capabilities for investigating electrode materials, electrolytes, and additives in lithium-ion battery research, including systems based on acetonitrile, where lithium metal is less suitable. Being ready to use and requiring no in-situ treatment, this reference electrode offers clear advantages. Modified LFP is therefore a reliable reference electrode for studying lithium-ion batteries.