Synergistic Construction of Composite Conductive Networks and Particle Size Gradation toward High-Volumetric-Energy-Density LiMn x Fe1– x PO4 Cathodes

Abstract

The commercial deployment of LiMnxFe1–xPO4(LMFP) cathodes is hindered by the Mn3+ Jahn–Teller effect, low electronic conductivity, and low compacted density resulting from intensive gas evolution during conventional pyrolysis. Herein, a comprehensive modification strategy integrating precursor regulation, surface coating, and particle packing optimization is developed. Initially, micrometer-scale spherical LMFP with a smooth surface is obtained via spray drying. Subsequently, one-dimensional carbon nanotubes (CNTs) and two-dimensional poly(vinyl alcohol) (PVA) are introduced to construct a composite conductive network, significantly reducing interfacial charge-transfer resistance. Finally, utilizing a multiscale particle gradation strategy, highly active nanoscale LMFP synthesized via a hydrothermal approach is precisely embedded into the interstitial voids of the micrometer spheres to maximize macroscopic packing efficiency. The modified LMFP-CNT/PVA exhibits exceptional cycling stability, delivering an initial discharge specific capacity of 150.2 mAh·g–1 at 1C, alongside an outstanding capacity retention of 99.5% after 500 cycles. Under the optimal gradation ratio, the LMFP@C-55 system successfully elevates the powder compacted density to 2.31 g·cm–3. This composite network effectively buffers the anisotropic volume strain induced by Mn3+ distortion and preserves long-term lattice integrity, providing a viable technical pathway for the commercialization of next-generation power batteries with high-volumetric energy density.