Kinetically tunable O vacancies in LiFePO4 for improved Li+/e− conduction and high-rate cycling

Abstract

Lithium iron phosphate (LFP) offers excellent structural and performance stability derived from the (PO4)3− polyanionic structure, which is beneficial for long-term usage. However, this inherent stability also comes along with intrinsically poor ionic and electronic conductivities, which have been notoriously plaguing its high-rate performance and broader applications. Here, we present a gas-assisted transient synthesis (GATS, ~ 30 s) of LFP with controllable oxygen vacancies (Ov) for enhanced rate performance yet without sacrificing structural integrity or cycling stability. Benefited by the ultrafast heating and a higher synthesis temperature, we revealed that the LFP synthesis in GATS followed an interface reaction mechanism (rapid core shrinking) with a low activation energy (Ea), thus reducing the synthesis time from ~ 16.5 h in tube furnace heating (TFH, often nuclei-growth mechanism) to merely seconds. The optimized LFP sample demonstrates an 8-fold enhancement in ionic conductivity and a 12-fold increase in electronic conductivity compared to LFP obtained by TFH and attains exceptional cycling stability even at high rates of 10 C, as evidenced by a higher capacity retention of 93.8% (vs. 63.6% of commercial LFP) after 1000 cycles. Our strategy offers a kinetic pathway for rapid synthesis and structural engineering of LFP, thus unlocking its potential for broader energy storage applications.