Optimization of carbon coatings on LiFePO4

Doeff, Marca M.; Wilcox, James D.; Kostecki, Robert; Lau, Grace Y.

doi:10.1016/j.jpowsour.2005.11.075

Cited by 231 publications

(149 citation statements)

References 25 publications

Supporting

Mentioning

142

Contrasting

Unclassified

Order By: Relevance

“…Structural defects or other factors that may retard the Li þ diffusion further lower the actual capacity of the cathode. Current strategies to enhance the electrochemical performance of LFP include carbon coating on LFP (cLFP) [1][2][3][4][5][6] , metal doping [7][8][9] , and LFP particle size reduction [10][11][12][13][14][15] . The carbon coating process has been massively used in industry because the conductive carbon layer increases the electron migration rate during the charge/discharge processes.…”

mentioning

confidence: 99%

Graphene-modified LiFePO4 cathode for lithium ion battery beyond theoretical capacity

Lin

et al. 2013

Nat Commun

520

View full text Add to dashboard Cite

The specific capacity of commercially available cathode carbon-coated lithium iron phosphate is typically 120-160 mAh g À 1 , which is lower than the theoretical value 170 mAh g À 1 . Here we report that the carbon-coated lithium iron phosphate, surface-modified with 2 wt% of the electrochemically exfoliated graphene layers, is able to reach 208 mAh g À 1 in specific capacity. The excess capacity is attributed to the reversible reduction-oxidation reaction between the lithium ions of the electrolyte and the exfoliated graphene flakes, where the graphene flakes exhibit a capacity higher than 2,000 mAh g À 1 . The highly conductive graphene flakes wrapping around carbon-coated lithium iron phosphate also assist the electron migration during the charge/discharge processes, diminishing the irreversible capacity at the first cycle and leading to B100% coulombic efficiency without fading at various C-rates. Such a simple and scalable approach may also be applied to other cathode systems, boosting up the capacity for various Li batteries.

show abstract

mentioning

confidence: 99%

Graphene-modified LiFePO4 cathode for lithium ion battery beyond theoretical capacity

Lin

et al. 2013

Nat Commun

520

View full text Add to dashboard Cite

show abstract

“…1,4 Nevertheless, LiFePO 4 is now recognized as one of the most promising cathode materials due to the availability of a variety of synthetic routes for the production of nanoparticles coated by conducting phases ͑e.g., carbon͒. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] The use of nanoparticles as the active mass helps to overcome kinetic problems due to the short diffusion length for ionic transport and a relatively high surface area, which promotes fast interfacial charge transfer. [7][8][9][10][11] Further coating by a conducting phase solves the problems of the poor electronic conductivity of nanoparticles because the small particle size allows efficient electron tunneling into the active mass once the composite structure includes conductive networks.…”

mentioning

confidence: 99%

“…[7][8][9][10][11] Further coating by a conducting phase solves the problems of the poor electronic conductivity of nanoparticles because the small particle size allows efficient electron tunneling into the active mass once the composite structure includes conductive networks. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] However, the use of nanoparticles means enhanced surface reactivity and detrimental and irreversible side reactions. It appears that for LiFePO 4 the use of nanomaterials, which demonstrate impressive rate capability, is fully justified, maybe because the surface reactivity of LiFePO 4 is sufficiently low to allow the use of active mass with a relatively high specific surface area.…”

mentioning

confidence: 99%

LiMnPO[sub 4] as an Advanced Cathode Material for Rechargeable Lithium Batteries

Martha

Markovsky

Grinblat

et al. 2009

J. Electrochem. Soc.

299

239

View full text Add to dashboard Cite

LiMnPO 4 nanoparticles synthesized by the polyol method were examined as a cathode material for advanced Li-ion batteries. The structure, surface morphology, and performance were characterized by X-ray diffraction, high resolution scanning electron microscopy, high resolution transmission electron microscopy, Raman, Fourier transform IR, and photoelectron spectroscopies, and standard electrochemical techniques. A stable reversible capacity up to 145 mAh g −1 could be measured at discharge potentials Ͼ4 V vs Li/Li + , with a reasonable capacity retention during prolonged charge/discharge cycling. The rate capability of the LiMnPO 4 electrodes studied herein was higher than that of LiNi 0.5 Mn 0.5 O 2 and LiNi 0.8 Co 0.15 Al 0.05 O 2 ͑NCA͒ in similar experiments and measurements. The active mass studied herein seems to be the least surface reactive in alkyl carbonate/LiPF 6 solutions. We attribute the low surface activity of this material, compared to the lithiated transition-metal oxides that are examined and used as cathode materials for Li-ion batteries, to the relatively low basicity and nucleophilicity of the oxygen atoms in the olivine compounds. The thermal stability of the LiMnPO 4 material in solutions ͑measured by differential scanning calorimetry͒ is much higher compared to that of transition-metal oxide cathodes. This is demonstrated herein by a comparison with NCA electrodes. 2 Among them, LiMnPO 4 is of particular interest as it offers the advantages of a flat discharge voltage profile at 4.1 V vs Li/Li + , the expected safety features, and an abundance of the relevant elements in the earth's crust.1-6 Hence, LiMnPO 4 can be an ideal substitute for the commonly used cathode material, LiCoO 2 , which is expensive, toxic, and demonstrates problematic safety features. The three-dimensional framework of the olivine structure is stabilized by the strong covalent bonds between the oxygen and the P 5+ ions, resulting in PO 4 3− tetrahedral polyanions. As a result, lithium metal phosphate materials do not undergo a structural rearrangement during lithiation and delithiation. This indicates that LiMPO 4 electrodes may demonstrate better stability and capacity retention during prolonged cycling as compared to lithiated transition-metal oxide cathode materials such as LiCoO 2 , LiNiO 2 , LiMnO 2 , and LiMn 2 O 4 . However, LiMPO 4 compounds and LiMnPO 4 , in particular, suffer from poor electronic and ionic ͑Li + ͒ conductivity, which means a limited rate capability ͑especially at low temperatures͒.

show abstract

“…However, the poor electronic conductivity and slow diffusion of lithium ion in bulk LiFePO 4 have been major challenges requiring new electrode material engineering. To improve electronic conductivity and reduce lithium ion diffusion length, many approaches, such as reducing the particle size to nanoscale [2][3][4][5], coating the particles with conductive carbon [6][7][8][9][10][11][12], and doping LiFePO 4 with various cations [13][14][15][16][17][18][19][20] have been proposed. In addition, LiFePO 4 decomposes above 700 • C leading to in-situ formation of conductive iron phosphides (Fe 2 P, FeP, Fe 3 P), and compounds with superior lithium-ion diffusion coefficients, such as, Li 3 PO 4 and Li 2 FeP 2 O 7 [21][22][23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Optimization of Electrochemical Performance of LiFePO4/C by Indium Doping and High Temperature Annealing

et al. 2017

View full text Add to dashboard Cite

Abstract:We have prepared nano-structured In-doped (1 mol %) LiFePO 4 /C samples by sol-gel method followed by a selective high temperature (600 and 700 • C) annealing in a reducing environment of flowing Ar/H 2 atmosphere. The crystal structure, particle size, morphology, and magnetic properties of nano-composites were characterized by X-ray diffraction (XRD), scanning electron microsopy (SEM), transmission electron microscopy (TEM), and 57 Fe Mössbauer spectroscopy. The Rietveld refinement of XRD patterns of the nano-composites were indexed to the olivine crystal structure of LiFePO 4 with space group Pnma, showing minor impurities of Fe 2 P and Li 3 PO 4 due to decomposition of LiFePO 4 . We found that the doping of In in LiFePO 4 /C nanocomposites affects the amount of decomposed products, when compared to the un-doped ones treated under similar conditions. An optimum amount of Fe 2 P present in the In-doped samples enhances the electronic conductivity to achieve a much improved electrochemical performance. The galvanostatic charge/discharge curves show a significant improvement in the electrochemical performance of 700 • C annealed In-doped-LiFePO 4 /C sample with a discharge capacity of 142 mAh·g −1 at 1 C rate, better rate capability (~128 mAh·g −1 at 10 C rate,~75% of the theoretical capacity) and excellent cyclic stability (96% retention after 250 cycles) compared to other samples. This enhancement in electrochemical performance is consistent with the results of our electrochemical impedance spectroscopy measurements showing decreased charge-transfer resistance and high exchange current density.

show abstract

Optimization of carbon coatings on LiFePO4

Cited by 231 publications

References 25 publications

Graphene-modified LiFePO4 cathode for lithium ion battery beyond theoretical capacity

Graphene-modified LiFePO4 cathode for lithium ion battery beyond theoretical capacity

LiMnPO[sub 4] as an Advanced Cathode Material for Rechargeable Lithium Batteries

Optimization of Electrochemical Performance of LiFePO4/C by Indium Doping and High Temperature Annealing

Contact Info

Product

Resources

About