Effect of Co₂P on Electrochemical Performance of Li(Mn_0.35Co_0.2Fe_0.45)PO₄/C

Abstract

In this paper, we report the synthesis of carbon coated Li(Mn0.35Co 0.2Fe0.45)PO4 and discuss the effect of Co2P formation during the carbothermal reduction process, which enhances the electrochemical performance of cathode material for lithium ion batteries. It was observed that Co2P was favorably formed in 5% H2/Ar than in Ar atmosphere. The conductivity of Li(Mn0.35Co0.2Fe0.45)PO4/C sintered at 600-800 degrees C in 5% H2/Ar is increased as the temperature is increased. The O K-edge X-ray absorption near edge spectrum (XANES) demonstrates that content of hole carriers is increased in Li(Mn0.35Co0.2Fe0.45)PO4/C as the amount of Co2P increased. We also observed that the capacity of Li(Mn0.35Co0.2Fe0.45)PO4/C is increased with sintering temperature, and it exhibited a maximum capacity of 166 mAh/g at 700 degrees C. It was found that the enhancement in the discharge capacity of sintered Li(Mn0.35Co0.2Fe0.45)PO4/C was as a result of its higher electrical conductivity under 5% H2/Ar atmosphere as compared with Ar atmosphere.

Nitridation effect on lithium iron phosphate cathode for rechargeable batteries

“…It is known that the nitridation temperature domain has an upper limit; in fact, according to some authors, heating up pristine LFP in a reducing atmosphere at 800 C or above causes partial decomposition of the phosphate with subsequent loss of phosphorous element. 51,52 This precludes the use of 'standard' (high temperatures and long times) ceramic methods under ammonia ux. We have established here that it is possible to synthesize olivine phases in an ammonia atmosphere from ceramic mixtures at temperatures below the limit of partial decomposition of phosphates and in short synthesis times.…”

“…Small quantities (about 1%) of Fe 2 P impurity phase were detected; this barringerite phase 53 is usually formed on heating at temperatures around 700 C in reducing atmospheres. 52,54 This impurity was included and quantied in the Rietveld renements as a second minor phase.…”

A High Voltage Olivine Cathode for Application in Lithium‐Ion Batteries

“…[39,40] The increase of Mn content in LiFe x Mn y Co z PO 4 materials is expectedt op ositivelya ffect the workingv oltage andc ycling stability. However,t ot he best of our knowledge, only LiMn 0.35 Co 0.2 Fe 0.45 PO 4 /C has been investigated [41] in addition to LiFe 1/3 Mn 1/3 Co 1/3 PO 4 .A ccordingly,w es tudied an olivine compound having compositionL iFe 0.25 Mn 0.5 Co 0.25 PO 4 synthesized through as olvothermalm ethod.T he material was fully characterized in terms of structure and morphologyb yX -ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), and high-angle annular dark field scanning TEM (HAADF-STEM). The Li + transportp roperties of the material and its electrochemical behavior in al ithium cell were studied by galvanostatici ntermittent titration technique( GITT), cyclic voltammetry (CV), andg alvanostatic cycling (GC).…”

“…The increase of Mn content in LiFe x Mn y Co z PO 4 materials is expected to positively affect the working voltage and cycling stability. However, to the best of our knowledge, only LiMn 0.35 Co 0.2 Fe 0.45 PO 4 /C has been investigated in addition to LiFe 1/3 Mn 1/3 Co 1/3 PO 4 . Accordingly, we studied an olivine compound having composition LiFe 0.25 Mn 0.5 Co 0.25 PO 4 synthesized through a solvothermal method.…”

Electrochemical and structural studies of LiCo1/3Mn1/3Fe1/3PO4 as a cathode material for lithium ion batteries

“…In order to improve the electrical conductivity and consequent performance, solid solutions of lithium multi-transition-metal phosphates have been prepared, including LiMn x Fe 1−x PO 4 reported by Yamada' group [13]. Moreover, Kuo et al substituted Mn by Co to reduce the effect of Jahn-Teller distortion of Mn 3+ so that LiMn 0.35 Co 0.2 Fe 0.45 PO 4 was successfully synthesized [14]. In order to investigate the lithium diffusivity of lithium multi-metal phosphate, LiCo 1/3 Mn 1/3 Fe 1/3 PO 4 was synthesized and ex-situ electrochemical impedance spectroscopy experiment was employed to investigate the lithium diffusivity of each phase transition reaction from M 2+ to M 3+ .…”