Synergistic Ti-Ni co-doping enhances the electrochemical performance and densification of LiMn0.6Fe0.4PO4/C cathodes

Ti-Ni co-doping improves electrochemical kinetics and powder densification. • Dopants Ti and Ni function on the Mn- and Fe-redox regions, respectively. • Powder compaction density increases by 8.5% to 2.04 g cm −3 after Ti-Ni doping. LiMn 0.6 Fe 0.4 PO 4 (LMFP) is a promising high-energy cathode, but its practical application is constrained by sluggish Mn 2+ /Mn 3+ redox kinetics and insufficient powder compaction density (PCD). Herein, Ti-doped, Ni-doped, and Ti–Ni co-doped LMFP/C were prepared by a ball-milling-assisted solid-state route. It is clarified that Ni predominantly accelerates the Fe 2+ /Fe 3+ reaction, whereas Ti promotes the kinetically slower Mn 2+ /Mn 3+ reaction and improves cycling stability. The optimal sample LMFP-2Ti-2Ni delivers 163.1 and 142.9 mAh g −1 at 0.1 and 5 C, respectively, and retains 90.8% of its capacity after 400 cycles at 1 C. Relative to pristine LMFP, the Ti-Ni co-doping increases the 0.1 C capacity from 144.7 to 163.1 mAh g −1 (+12.7%) and the PCD from 1.88 to 2.04 g cm −3 (+8.5%). Also, the relative unit-cell-volume variation decreases from approximately 5.2% to 4.6%, indicating more gradual bulk-lattice evolution. Thus, Ti–Ni co-doping as a complementary strategy can simultaneously improve rate capability, cycling durability, and particle packing in LMFP/C cathodes. Download: Download high-res image (356KB) Download: Download full-size image