Olivine FePO₄ Cathode Material for Rechargeable Mg-Ion Batteries

Abstract

In this work, MgFePO is exploited as a cathode material for rechargeable Mg-ion batteries. FePO/C prepared via electrochemical delithiation of LiFePO/C is directly used as the cathode in aqueous Mg electrolyte, and reversible capacity is achieved for the first time. Notably, the capacity (82 mA h/g) is half of the theoretical value (164 mA h/g) and "asymmetric" discharge/charge behavior can be observed. In addition, first-principles calculations show it is the strong Mg-ion interactions between adjacent channels that not only limit the capacity of the cathode but also lead to the difference in rates for Mg-ion intercalation and deintercalation. This work provides experimental and theoretical evidence that reveal the mechanism of Mg-ion intercalation and deintercalation in a FePO host, which gives guidance in designing cathode materials for rechargeable batteries based on multivalent metal ions.

High-Voltage Phosphate Cathodes for Rechargeable Ca-Ion Batteries

“…Here, we demonstrate two representative polyanion phosphates as new high-voltage CIB cathodes. NaV 2 (PO 4 ) 3 and FePO 4 were chosen, as they are electrochemically active with sodium cations (Na + (116 pm), which has a similar ionic radius to Ca 2+ (114 pm)) and other studied multivalent intercalation cations (Zn 2+ , Mg 2+ , Al 3+ ). − In our study, we observed reversible calcium intercalation at high voltage at room temperature in a nonaqueous electrolyte. Importantly, we utilized numerous multiple characterization techniques, including synchrotron XRD, XAS, EELS, and EDS analysis to elucidate and confirm reversible calcium intercalation.…”

Structure, morphology, size and application of iron phosphate

“…FePO 4 /C nanospheres demonstrate a high initial discharging capacity of 151 mAh g −1 at 20 mA g −1 , stable cyclability (94% capacity retention ratio over 160 cycles), as well as high rate capability (44 mAh g −1 at 1000 mA g −1 ) for Na-ion storage [28]. FePO 4 /C prepared via electrochemical delithiation of LiFePO 4 /C is directly used as the cathode material for rechargeable Mgion batteries, and reversible capacity is achieved for the first time [78]. Huang et al [79] synthesized hollow FePO 4 spheres wrapped by reduced graphene oxide as an efficient sulfur host material.…”

Chemical Flexibility of Mg in Pnictide Materials: Structure and Properties Diversity

“…Various materials, such as LiFePO 4 , LiMn 2 O 4 , LiCoO 2 , LiNi 1/3 Mn 1/3 Co 1/3 O 2 , graphite, and MoS 2 , have demonstrated use as electrode materials for Li-ion batteries due to the presence of channels or layers which are able to house Li cations. Due to the similar size of Li + and Mg 2+ , research efforts have led to analogous applications for Mg-ion batteries. ,, Materials such as LiFePO 4 and Li 3 V 2 (PO 4 ) 3 have been studied in the presence of Mg 2+ -rich electrolytes, which allowed the Li from the structures to be replaced by Mg ions upon cycling. , The crystal structures of LiFePO 4 and Li 3 V 2 (PO 4 ) 3 are shown in Figure . The presence of channels filled with Mg cations is not sufficient to be an electrochemically active material, as in the case of the MgCr 2 S 4 thiospinel.…”

“…Due to the similar size of Li + and Mg 2+ , research efforts have led to analogous applications for Mg-ion batteries. 129,139,140 Materials such as LiFePO 4 and Li 3 V 2 (PO 4 ) 3 have been studied in the presence of Mg 2+ -rich electrolytes, which allowed the Li from the structures to be replaced by Mg ions upon cycling. 139,141 The crystal structures of LiFePO 4 and Li 3 V 2 (PO 4 ) 3 are shown in Figure 11.…”

“…129,139,140 Materials such as LiFePO 4 and Li 3 V 2 (PO 4 ) 3 have been studied in the presence of Mg 2+ -rich electrolytes, which allowed the Li from the structures to be replaced by Mg ions upon cycling. 139,141 The crystal structures of LiFePO 4 and Li 3 V 2 (PO 4 ) 3 are shown in Figure 11. The presence of channels filled with Mg cations is not sufficient to be an electrochemically active material, as in the case of the MgCr 2 S 4 thiospinel.…”