Optimized Li+ ion diffusion pathways in unidirectional stacked lithium iron phosphate cathodes: Enhanced electrochemical performance and long-term stability

Abstract

In this study, we introduce an innovative approach to enhance the electrochemical performance and longevity of lithium iron phosphate (LiFePO₄, LFP) cathode materials through a novel saccharide-assisted unidirectional stacking method. The inherent challenges of LFP, such as low lithium-ion diffusion and limited electrical conductivity, are addressed by leveraging saccharides as binders to achieve precise alignment of LFP particles. This method facilitates the formation of unobstructed lithium-ion pathways, significantly enhancing Li⁺ ion diffusion rates and cycle stability. The unmodified LFP cathode exhibited a lithium-ion diffusion coefficient (D_Li⁺) of 7.79 × 10⁻¹² cm² s⁻¹, while the S5 (sucrose 5 %) LFP cathode demonstrated a superior diffusion coefficient of 3.5 × 10⁻¹⁰ cm² s⁻¹. Additionally, the S5-LFP achieved a remarkable discharge capacity of 165.1 mAh g⁻¹ at a 0.1C rate, compared to 147.8 mAh g⁻¹ for the unmodified LFP. The cycle stability was also significantly improved, with the S5-LFP retaining 86.3 % of its capacity after 2,000 cycles at a 5C rate, whereas the unmodified LFP retained only 79.2 % under the same conditions. These improvements are attributed to the optimized particle alignment achieved through saccharide-assisted stacking, which enhances Li⁺ ion diffusion and overall electrochemical performance. Additionally, the structural integrity and electrochemical stability of the S5-LFP cathodes were thoroughly validated through a comprehensive set of characterization methods and electrochemical tests, highlighting the scalability and cost-effectiveness of this technique for battery manufacturing. This breakthrough in cathode material design offers a promising pathway for the development of high-performance, durable lithium-ion batteries, particularly for applications in electric vehicles and other demanding energy storage systems.