Insights on the delithiation/lithiation reactions of Li Mn0.8Fe0.2PO4 mesocrystals in Li+ batteries by in situ techniques

Binder‐Free Electrodes with High Energy Density and Excellent Flexibility Enabled by Hierarchical Configuration for Wearable Lithium Ion Batteries

“…[ 60 ] With GITT measurements, we can estimate the apparent value of the Li + diffusivity in electrodes. [ 61,62 ] The details of GITT analysis are shown in Supplementary material. The calculated apparent Li + diffusivity ( D Li+ ) are 2.9 × 10 −13 cm 2 s −1 for pCNT/LFP@rGO/ccCNT electrode and 6.1×10 −14 cm 2 s −1 for traditional electrode with similar mass loading of the same EAM, which suggesting a faster ionic transport and an effective electrolyte accessibility of the binder‐free electrode.…”

Zero Lithium Miscibility Gap Enables High-Rate Equimolar Li(Mn,Fe)PO4 Solid Solution

“…These transition characteristics are very compatible with the well-known twophase reaction (LiFePO 4 /FePO 4 ). 42,43,45 Compared with the solid-state reaction 24,33 and solvothermal synthesis, 18 the cations (Fe,Mn) are more homogeneously distributed (Figure 1d) in the crystal lattice of the LiMn 0.5 Fe 0.5 PO 4 prepared in this work. Based on the previous experimental results, the single-phase transition of equimolar LiMn 0.5 Fe 0.5 PO 4 is caused by cations (Fe,Mn) evenly distributed in the crystal lattice and the Fe 2+ /Fe 3+ and Mn 2+ /Mn 3+ stepwise redox reactions (Figure 2a and c).…”

“…The continuous variation of peak position behavior is related to a singlephase evolution with a feature of zero lithium miscibility gap for the equimolar LiMn 0.5 Fe 0.5 PO 4 solid solution, which is due to the insertion of Li + ions into the Mn 0.5 Fe 0.5 PO 4 lattice. 18,42,43 Interestingly, at the beginning of the discharge, there is a slight lag at (211)/(020), (311), and ( 121) reflections. This is consistent with the results reported by Ravnsbaek et al 44 It is argued that as the particle size is reduced to below ∼150 nm, metastable behavior is easily induced, especially during discharge, such that continuous solid solutions dominate.…”

“…These features are in accordance with the single-phase transition mechanism. 18,42,43 Moreover, the full width at half-maximum changes gradually during the (dis)charging process, indicating that equimolar LiMn 0.5 Fe 0.5 PO 4 underwent a single-phase evolution (Figure S6). 42 Notably, the volume of LiMn 0.5 Fe 0.5 PO 4 changes by 3.8% during the (de)lithiation process (Figure 3c), which is smaller than that of LiFePO 4 .…”

“…Much efforts have been devoted to this issue. For instance, Wi et al 18 reported that during the (de)lithiation process, Li x Mn 0.8 Fe 0.2 PO 4 mesocrystals underwent solid solution phase transformations in the Fe 2+ /Fe 3+ reaction region, with a typical two-phase reaction in the Mn 2+ /Mn 3+ reaction region. The sluggish kinetics of Li x Mn 0.8 Fe 0.2 PO 4 mesocrystals is caused by the slow apparent Li + diffusivity, which is triggered by the Mn redox reaction.…”