Two series of lithium iron phosphate (LiFePO4) nanocomposites are prepared by a solvothermal method coupled with high temperature calcination using mononuclear and binuclear metal hexaaminophthalocyanines as modulatory additives, respectively. Physical and electrochemical performances of the composites as cathode materials of lithium-ion batteries are characterized by inductively coupled plasma (ICP), X-ray diffraction (XRD), infrared (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical techniques. The results indicate that the as-synthesized samples modified with binuclear metal phthalocyanines can improve electrochemical properties of LiFePO4 (LFP) for lithium-ion batteries. The composite using binuclear manganese hexaaminophthalocyanine as additive can achieve the highest initial specific discharge capacity of 152.3 mAh/g at 0.1 C, higher than that of ones modified with the corresponding mononuclear phthalocyanine 143.0 mAh/g. Furthermore, the most excellent product exhibits a pretty good capacity retention of 93.0% after 50 cycles at 0.1 C, cycling stability, and low charge transfer resistance of 58.7 Ω.

In situ scanning transmission electron microscopy (STEM) through liquids is a promising approach for exploring biological and materials processes. However, options for in situ chemical identification are limited: X-ray analysis is precluded because the liquid cell holder shadows the detector and electron energy-loss spectroscopy (EELS) is degraded by multiple scattering events in thick layers. Here, we explore the limits of EELS in the study of chemical reactions in their native environments in real time and on the nanometer scale. The determination of the local electron density, optical gap, and thickness of the liquid layer by valence EELS is demonstrated. By comparing theoretical and experimental plasmon energies, we find that liquids appear to follow the free-electron model that has been previously established for solids. Signals at energies below the optical gap and plasmon energy of the liquid provide a high signal-to-background ratio regime as demonstrated for LiFePO4 in an aqueous solution. The potential for the use of valence EELS to understand in situ STEM reactions is demonstrated for beam-induced deposition of metallic copper: as copper clusters grow, EELS develops low-loss peaks corresponding to metallic copper. From these techniques, in situ imaging and valence EELS offer insights into the local electronic structure of nanoparticles and chemical reactions.

The electrochemical reaction behavior of a commercial Li-ion battery (LiFePO4-based cathode, graphite-based anode) has been measured via in situ neutron diffraction. A multivariate analysis was successfully applied to the neutron diffraction data set facilitating in the determination of Li bearing phases participating in the electrochemical reaction in both the anode and cathode as a function of state-of-charge (SOC). The analysis resulted in quantified phase fraction values for LiFePO4 and FePO4 cathode compounds as well as the identification of staging behavior of Li6, Li12, Li24, and graphite phases in the anode. An additional Li-graphite phase has also been tentatively identified during electrochemical cycling as LiC48 at conditions of ∼5% to 15% SOC.