Abstract:Olivine-structured lithium ion phosphate (LiFePO 4 ) is one of the most competitive candidates of energydriven cathode material for sustainable lithium ion battery (LIB) systems. However, the high electrochemical performance is significantly limited by the slow diffusivity of Li-ion in LiFePO 4 (ca. 10 -10 14 cm 2 ·s -1 ) together with the low electronic conductivity (ca. 10 -9 S·cm -1 ), which is the big challenge we are currently facing. To resolve the challenge, many efforts have been directed to dynamics o… Show more
“…It can be noted that the annealing in air of amorphous LiFePO 4 not only leads to crystallization but also to the iron oxidation according to (Eq. 1) [28, 29]:Fig. 1XRD patterns of samples a LiFePO 4 target, b as-deposited Li 3 Fe 2 (PO 4 ) 3 , and c annealed Li 3 Fe 2 (PO 4 ) 3 at 700 °C for 3 h…”
We report the electrochemical performance of porous NASICON-type Li3Fe2(PO4)3 thin films to be used as a cathode for Li-ion microbatteries. Crystalline porous NASICON-type Li3Fe2(PO4)3 layers were obtained by radio frequency sputtering with an annealing treatment. The thin films were characterized by XRD, SEM, and electrochemical techniques. The chronoamperometry experiments showed that a discharge capacity of 88 mAhg−1 (23 μAhcm−2) is attained for the first cycle at C/10 to reach 65 mAhg−1 (17 μAhcm−2) after 10 cycles with a good stability over 40 cycles.
“…It can be noted that the annealing in air of amorphous LiFePO 4 not only leads to crystallization but also to the iron oxidation according to (Eq. 1) [28, 29]:Fig. 1XRD patterns of samples a LiFePO 4 target, b as-deposited Li 3 Fe 2 (PO 4 ) 3 , and c annealed Li 3 Fe 2 (PO 4 ) 3 at 700 °C for 3 h…”
We report the electrochemical performance of porous NASICON-type Li3Fe2(PO4)3 thin films to be used as a cathode for Li-ion microbatteries. Crystalline porous NASICON-type Li3Fe2(PO4)3 layers were obtained by radio frequency sputtering with an annealing treatment. The thin films were characterized by XRD, SEM, and electrochemical techniques. The chronoamperometry experiments showed that a discharge capacity of 88 mAhg−1 (23 μAhcm−2) is attained for the first cycle at C/10 to reach 65 mAhg−1 (17 μAhcm−2) after 10 cycles with a good stability over 40 cycles.
“…Whereas for the LiFePO 4 /C composite, the equation will be LiFePO 4 + xC + 1/4O 2 + xO 2 = 1/3Li 3 Fe 2 (PO 4 ) 3 + 1/6Fe 2 O 3 + xCO 2 (2) wherein x represents the carbon content in this composite. At above 600 C, the mass of the LiFePO 4 /C composite remain constant, indicating that the oxidization reactions are finished.…”
Section: Structural Characterizationmentioning
confidence: 99%
“…Olivine orthophosphate lithium iron (II) phosphate (LiFePO 4 ) has attracted considerable attention as the cathode material to replace the toxic and expensive cobalt-oxide-based cathodes for use in Li-ion battery due to its merits of high operating voltage ($3.4 V vs Li/Li + ), large theoretical capacity ($170 mAhÁg À1 ), and thermal stability, as well as its low-cost raw materials, no toxicity, and environmental benignity [1][2][3][4]. However, the inherently low electronic conductivity ($10 À9 SÁcm À1 ) and ionic conductivity ($1.8Â10 À14 cm 2 ÁS À1 ) are the two major obstacles of LiFePO 4 material, which results in noteworthy capacity loss during highrate discharge, making it unsuitable for high-power battery applications [5].…”
“…Conductive surface modifications towards carbon coating of olivine-structured lithium iron phosphate (LiFePO 4 ) have attracted significant attention due to its high-efficiency and environmental benign in the development of lithium ion battery cathode materials [1][2][3][4][5] .…”
An evolutionary composite of LiFePO4 with nitrogen and boron codoped carbon layers was prepared by processing hydrothermal-synthesized LiFePO4. This novel codoping method is successfully applied to LiFePO4 for commercial use, and it achieved excellent electrochemical performance. The electrochemical performance can be improved through single nitrogen doping (LiFePO4/C-N) or boron doping (LiFePO4/C-B). When modifying the LiFePO4/C-B with nitrogen (to synthesis LiFePO4/C-B+N) the undesired nonconducting N-B configurations (190.1 and 397.9 eV) are generated. This decreases the electronic conductivity from 2.56×10(-2) to 1.30×10(-2) S cm(-1) resulting in weak electrochemical performance. Nevertheless, using the opposite order to decorate LiFePO4/C-N with boron (to obtain LiFePO4/C-N+B) not only eliminates the nonconducting N-B impurity, but also promotes the conductive C-N (398.3, 400.3, and 401.1 eV) and C-B (189.5 eV) configurations-this markedly improves the electronic conductivity to 1.36×10(-1) S cm(-1). Meanwhile the positive doping strategy leads to synergistic electrochemical activity distinctly compared with single N- or B-doped materials (even much better than their sum capacity at 20 C). Moreover, due to the electron and hole-type carriers donated by nitrogen and boron atoms, the N+B codoped carbon coating tremendously enhances the electrochemical property: at the rate of 20 C, the codoped sample can elevate the discharge capacity of LFP/C from 101.1 mAh g(-1) to 121.6 mAh g(-1), and the codoped product based on commercial LiFePO4/C shows a discharge capacity of 78.4 mAh g(-1) rather than 48.1 mAh g(-1). Nevertheless, the B+N codoped sample decreases the discharge capacity of LFP/C from 101.1 mAh g(-1) to 95.4 mAh g(-1), while the commercial LFP/C changes from 48.1 mAh g(-1) to 40.6 mAh g(-1).
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