Are Fe-Li Antisite Defects Necessarily Detrimental to the Diffusion of Li + in LiFePO4/C?

Abstract

The one-dimensional Li+ diffusion channel is the key factor restricting the rate performance and low-temperature performance of LFP/C composites. By artificially creating a certain content of anti-site defects, the Li+ in the LFP material can be diffused two-dimensionally. The LFP/C composites synthesized by the carbothermic reduction method at 700°C have 3.77% Fe-Li anti-site defects, showing higher rate performance, cycle performance, and discharge specific capacity. The CV, EIS, and GITT tests show that the Li+ diffusion coefficient of LFP is the highest when the content of Fe-Li anti-site defects is 3.77%. DFT calculation shows that the single pair of Fe-Li anti-site defects is conducive to the two-dimensional diffusion of Li+, while the continuous two pairs of anti-site defects greatly inhibit the diffusion of Li+ along the original [010] crystal direction.

Dynamic Li+ Capture through Ligand‐Chain Interaction for the Regeneration of Depleted LiFePO4 Cathode

“…The presence of both LFP and FP phases in O‐LFP indicated substantial Li + loss from LFP during prolonged cycling, consistent with the XRD data and prior research. [ 13 ] The heterogeneous phase distribution in O‐LFP severely restricted the insertion/extraction of Li + owing to the insufficient Li + replenishment resulting from the incomplete conversion between LFP and FP. On the contrary, R‐LFP exhibited distinct lattice fringes and a periodic arrangement.…”

“…For all the LFP half cells, a good linear fitting result was observed, proving that the de/intercalation of Li + during the charge–discharge process was controlled by diffusion. Therefore, the corresponding D Li+ in the electrode material could be calculated using the Randles–Sevcik equation: [ 13,32 ] $$$$\begin{equation}{i}_{\mathrm{p}} = 2.69\ \times {10}^5{n}^{3/2}A{D}_{{\mathrm{Li}} + }^{1/2}{C}_0{v}^{1/2}\end{equation}$$$$where i p is the peak current density, n is the number of electrons transferred per reactant molecule during the charge–discharge process in the LFP electrodes ( n = 1 for the LFP phase), A is the electrode surface area (1.13 cm 2 ), C 0 is the concentration of Li + in the crystal, and v is the sweep rate.…”

“…For all the LFP half cells, a good linear fitting result was observed, proving that the de/intercalation of Li + during the charge-discharge process was controlled by diffusion. Therefore, the corresponding D Li+ in the electrode material could be calculated using the Randles-Sevcik equation: [13,32] i p = 2.69 × 10 5 n 3∕2 AD 1∕2 Li+ C 0 v 1∕2…”

“…This, in turn, provides an opportunity for the Fe ions to migrate and generate Fe─Li antisite defects, further hindering the Li + transport. [ 13 ] Therefore, the performance degradation of LFP becomes more evident with extended cycling.…”

W Modification of Nickel-Rich Ternary Cathode Material for Efficient Lithium-Ion Batteries

“…7 Though the rapidly commercialized LiFePO 4 has been considered to be high energy density and excellent stability in power tools, there is still a certain gap on its electronic conductivity and temperature adaptability. 8 LiMn 2 O 4 with the low cost raw material is generally applied in low-speed electric vehicles, but the low energy density and the fast capacity decays are disadvantageous factors affecting the development of commercialization. 9 Optimistically, high nickel ternary cathode materials for LIBs have becoming the first choice for the next future commercial batteries owning to their advantages of high discharge capacity, power density together with reasonable price.…”