Synthesis of Fe2+ Substituted High-Performance LiMn1−xFexPO4/C (x = 0, 0.1, 0.2, 0.3, 0.4) Cathode Materials for Lithium-Ion Batteries via Sol-Gel Processes

Abstract

A series of carbon-coated LiMn1−xFexPO4 (x = 0, 0.1, 0.2, 0.3, 0.4) materials are successfully constructed using glucose as carbon sources via sol-gel processes. The morphology of the synthesized material particles are more regular and particle sizes are more homogeneous. The carbon-coated LiMn0.8Fe0.2PO4 material obtains the discharge specific capacity of 152.5 mAh·g−1 at 0.1 C rate and its discharge specific capacity reaches 95.7 mAh·g−1 at 5 C rate. Iron doping offers a viable way to improve the electronic conductivity and lattice defects of materials, as well as improving transmission kinetics, thereby improving the rate performance and cycle performance of materials, which is an effective method to promote the electrical properties.

Boron‐Catalyzed Graphitization Carbon Layer Enabling LiMn0.8Fe0.2PO4 Cathode Superior Kinetics and Li‐Storage Properties

“…The diffusion coefficient of Li + ( D Li + ) in the solid phase is calculated according to the Randles‐Sevick equation. [ 34 ] The peak current ( I p ) is calculated according to Equation (2), which is consistent with the diffusion equation in the semi‐infinite diffusion model. $$\[ \begin{array}{*{20}{c}}{{I_p} = 2.69 \times {{10}^5} \times {C_{{\rm{Li}}}} \times A \times {n^{3/2}} \times D_{{\rm{Li}}}^{1/2} \times {\nu ^{1/2}}}\end{array} \]$$…”

“…The diffusion coefficient of Li + (D Li + ) in the solid phase is calculated according to the Randles-Sevick equation. [34] The peak current (I p ) is calculated according to Equation (2), which is consistent with the diffusion equation in the semi-infinite diffusion model.…”

Novel NASICON‐Type Na‐V‐Mn‐Ni‐Containing Cathodes for High‐Rate and Long‐Life SIBs

“…[51,52] Also, as previously reported, an increase in the amount of Mn in the composition of the cathode material usually leads to a loss of capacity during long-term cycling, which is associated with the loss of the electrochemical activity of the Mn 2+ /Mn 3+ redox center. [53] By comparing the first cycle charge-discharge curves of VM, VMN-0.5, and VN cathodes (Figure 5c), it can be seen that there is a flat voltage platform between 3.35-3.58 V on the charge-discharge curve of VMN-0.5 cathode, which corresponds to the conversion of V 3+ /V 4+ and Mn 2+ /Mn 3+ . In addition, there is a small platform in the range of 3.81-4.0 V during charging, which corresponds to a small amount of V 4+ /V 5+ and Ni 2+ /Ni 3+ reactions, but due to its poor reversibility, the corresponding platform during discharging does not appear.…”

“…[ 51,52 ] Also, as previously reported, an increase in the amount of Mn in the composition of the cathode material usually leads to a loss of capacity during long‐term cycling, which is associated with the loss of the electrochemical activity of the Mn 2+ /Mn 3+ redox center. [ 53 ]…”

Electrochemical Performance and In Situ Phase Transition Analysis of Iron-Doped Lithium Manganese Phosphate

“…Among them, uniform coating of conductive carbon shells to obtain LiMn x Fe 1– x PO 4 /C (0< x < 1) and partial substitution of Fe 2+ with Mn 2+ in solid solution have been investigated widely. − Coating of homogeneous conductive carbon shells not only increases the electronic conductivity of LMP cathode and reduces overall cell resistance but also prevents HF attacks to electrodes to avoid Mn dissolution in electrolyte . Analogously, available Fe 2+ doping improves the ionic diffusion coefficient, electronic conductivity, and structural stability while the suitable Mn/Fe ratio is still being debated, as a higher ratio results in higher energy density but less discharge capacity and worse rate capability . Therefore, a suitable Mn/Fe ratio is very important for the overall performance of the battery.…”