Lithium iron phosphate

About: Lithium iron phosphate is a research topic. Over the lifetime, 4360 publications have been published within this topic receiving 60977 citations. The topic is also known as: LiFePO4 & LFP.

Phospho‐olivines as Positive‐Electrode Materials for Rechargeable Lithium Batteries

Abstract: Reversible extraction of lithium from LiFePO 4 (triphylite) and insertion of lithium into FePO 4 at 3.5 V vs. lithium at 0.05 mA/cm 2 shows this material to be an excellent candidate for the cathode of a low-power, rechargeable lithium battery that is inexpensive, nontoxic, and environmentally benign. Electrochemical extraction was limited to ∼0.6 Li/formula unit; but even with this restriction the specific capacity is 100 to 110 mAh/g. Complete extraction of lithium was performed chemically; it gave a new phase, FePO 4 , isostructural with heterosite, Fe 0.65 Mn 0.35 PO 4 . The FePO 4 framework of the ordered olivine LiFePO 4 is retained with minor displacive adjustments. Nevertheless the insertion/extraction reaction proceeds via a two-phase process, and a reversible loss in capacity with increasing current density appears to be associated with a diffusion-limited transfer of lithium across the two-phase interface. Electrochemical extraction of lithium from isostructural LiMPO 4 (M = Mn, Co, or Ni) with an LiClO 4 electrolyte was not possible; but successful extraction of lithium from LiFe 1-x Mn x PO 4 was accomplished with maximum oxidation of the Mn 3+ /Mn 2+ occurring at x = 0.5. The Fe 3+ /Fe 2+ couple was oxidized first at 3.5 V followed by oxidation of the Mn 3+ /Mn 2+ couple at 4.1 V vs. lithium. The Fe 3+ -O-Mn 2+ interactions appear to destabilize the Mn 2+ level and stabilize the Fe 2+ level so as to make the Mn 3+ /Mn 2+ energy accessible.

A multifunctional 3.5 V iron-based phosphate cathode for rechargeable batteries

Abstract: In the search for new positive-electrode materials for lithium-ion batteries, recent research has focused on nanostructured lithium transition-metal phosphates that exhibit desirable properties such as high energy storage capacity combined with electrochemical stability1,2. Only one member of this class—the olivine LiFePO4 (ref. 3)—has risen to prominence so far, owing to its other characteristics, which include low cost, low environmental impact and safety. These are critical for large-capacity systems such as plug-in hybrid electric vehicles. Nonetheless, olivine has some inherent shortcomings, including one-dimensional lithium-ion transport and a two-phase redox reaction that together limit the mobility of the phase boundary4,5,6,7. Thus, nanocrystallites are key to enable fast rate behaviour8,9. It has also been suggested that the long-term economic viability of large-scale Li-ion energy storage systems could be ultimately limited by global lithium reserves, although this remains speculative at present. (Current proven world reserves should be sufficient for the hybrid electric vehicle market, although plug-in hybrid electric vehicle and electric vehicle expansion would put considerable strain on resources and hence cost effectiveness.) Here, we report on a sodium/lithium iron phosphate, A2FePO4F (A=Na, Li), that could serve as a cathode in either Li-ion or Na-ion cells. Furthermore, it possesses facile two-dimensional pathways for Li+ transport, and the structural changes on reduction–oxidation are minimal. This results in a volume change of only 3.7% that—unlike the olivine—contributes to the absence of distinct two-phase behaviour during redox, and a reversible capacity that is 85% of theoretical.

Lithium deintercalation in LiFePO4 nanoparticles via a domino-cascade model

Abstract: Lithium iron phosphate is one of the most promising positive-electrode materials for the next generation of lithium-ion batteries that will be used in electric and plug-in hybrid vehicles. Lithium deintercalation (intercalation) proceeds through a two-phase reaction between compositions very close to LiFePO(4) and FePO(4). As both endmember phases are very poor ionic and electronic conductors, it is difficult to understand the intercalation mechanism at the microscopic scale. Here, we report a characterization of electrochemically deintercalated nanomaterials by X-ray diffraction and electron microscopy that shows the coexistence of fully intercalated and fully deintercalated individual particles. This result indicates that the growth reaction is considerably faster than its nucleation. The reaction mechanism is described by a 'domino-cascade model' and is explained by the existence of structural constraints occurring just at the reaction interface: the minimization of the elastic energy enhances the deintercalation (intercalation) process that occurs as a wave moving through the entire crystal. This model opens new perspectives in the search for new electrode materials even with poor ionic and electronic conductivities.