Influence Mechanism of Mg²⁺ Doping on Electrochemical Properties of LiFePO₄ Cathode Materials

Abstract

For this work, a Mg2+-doped LiFePO4 (LFP) cathode material was prepared using a solid-state method with Mg­(CH3COO)2 as the Mg2+ dopant. X-ray diffraction and refinement data suggested that an appropriate doping amount of Mg2+ can reduce the cell volume of LFP, shorten the Fe–O and P–O bonds, and elongate the Li–O bond, thereby facilitating the diffusion of Li+. X-ray photoelectron spectroscopy test results revealed that Mg2+ doping prevents the formation of Li–Fe antisite defects while also promoting the formation of Fe2P, thereby improving the electronic conductivity of the LFP. The electronic conductivity was measured using a four-probe teste, and the Li+ diffusion rate was fitted and calculated according to the electrochemical impedance spectroscopy test results. The results found that electron conductivity expanded by 275 times and the Li+ diffusion coefficient increased by 3.6 times following LFP being doped with Mg2+. Charge/discharge curves and cyclic voltammetry test reveal that LFP with Mg2+ doping has superior reversibility, rate performance, and cycle stability, and the capacity can be maintained at 162 mA h g–1 following 300 cycles at 0.1 C.

Dual Modification of Olivine LiFe0.5Mn0.5PO4 Cathodes with Accelerated Kinetics for High-Rate Lithium-Ion Batteries

“…From Figure d, the C 1s spectra exhibit the well-defined C-coating of LMFP/C-Nb samples, and the carbon contents are measured to be ∼4 wt %. Figure e,f demonstrates that Fe and Mn ions in LMFP/C-Nb samples are all divalent according to previous kinds of literature. , The appeared slight Fe 2 P species were generated due to the reducibility of the surface C-coating layer at high temperatures . The ICP-OES results of LMFP/C-Nb samples with different Nb-doping contents are depicted in Table S1.…”

Hybrid Polymer Electrolyte Encased Cathode Particles Interface‐Based Core–Shell Structure for High‐Performance Room Temperature All‐Solid‐State Batteries

“…It exhibits oxidation peaks at 3.62, 3.75, 4.01, and 4.19 V during charge, which are attributed to the multi-phase transition. [41] The phase transitions are associated with hexagonal to monoclinic, monoclinic to hexagonal, and hexagonal to hexagonal, comparable to the phase shifts determined in LIBs with liquid electrolyte. [46,47] As a result, the HPEIC design does not alter the redox process of the cathode materials and exhibits comparable electrochemical performance to conventional LIBs with liquid electrolytes.…”

“…The determined lithium‐ion diffusion coefficient is comparable to liquid electrolyte‐based lithium‐ion batteries (LIBs). [ 41 ] The integration of ultrathin HPE on the surface of the cathode not only improved the cathode/electrolyte interface contact but also enhanced the Li + diffusion of the cathode electrode. The mechanism of the improved Li + diffusion is indicated in the schematic diagram (Scheme 1b), where the highly ionic conductive networks of HPEs encapsulate the cathode particles, facilitating excellent Li + diffusion.…”

“…All the SSBs show a well‐resolved oxidation and reduction peak around 3.6 and 3.22 V at 0.1 mV s −1, which correspond to the Fe 2+ to Fe 3+ and Fe 3+ to Fe 2+ redox reactions of LFP cathodes and are comparable to liquid electrolyte‐based LFP LIBs. [ 41 ] The LFP|SPE|Li cell exhibits redox peaks at 3.822 and 3.02 V at 0.1 mV s −1 , with a significant potential difference between the oxidation and reduction peaks (802 mV), implying poor reversibility and cycle stability due to low ionic conductivity and transference number of the SPE. No excessive oxidation and reduction peaks are detected in the CV curves of LFP|SPE|Li, LFP|HPE‐AL‐LLZO:15|Li, LFP|HPE‐AL‐LLZO:25|Li, and HPEIC/Li SSBs, showing superior electrochemical stability.…”

Revealing the Ultrahigh Rate Performance of the La and Ce Co-doping LiFePO4 Composite

“…Therefore, the kinetics of ion transport are further influenced . In a comparison of electrochemical properties modified with Li site and O site doping, Fe site substitution with metal elements is more effective owing to the diverse selection of metal elements and easy substitution. , Besides, the active materials present low cell internal resistance and enhanced Li-ion diffusion rate and capacity retention after being modified at the Fe site than other positions. Thus, various single dopants (Mg, Mn, Sm, Zn, etc.)…”