Suppression of degradation for lithium iron phosphate cylindrical batteries by nano silicon surface modification

Yang, Wenyu; Wang, Zhisheng; Chen, Lei; Chen, Yue; Zhang, Lin; Lin, Yingbin; Li, Jiaxin; Huang, Zhigao

doi:10.1039/c7ra06027k

Cited by 13 publications

(10 citation statements)

References 45 publications

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“…Work functions of the olivine phosphates have also been experimentally obtained using ultraviolet photoelectron spectroscopy (UPS) with He I radiation (21.21 eV), as shown in Supporting Information Figure S2. The result for LiFePO 4 is in good agreement with a previous measurement by Kelvin probe force microscopy . It is worth noting that LiFePO 4 has a work function lower than the value of the band gap, while LiMnPO 4 , LiCoPO 4 , and LiNiPO 4 have higher work functions than their respective band gap values.…”

Section: Resultssupporting

confidence: 90%

“…The result for LiFePO 4 is in good agreement with a previous measurement by Kelvin probe force microscopy. 46 It is worth noting that LiFePO 4 has a work function lower than the value of the band gap, while LiMnPO 4 , LiCoPO 4 , and LiNiPO 4 have higher work functions than their respective band gap values. This result suggests that the vacuum level of LiFePO 4 lies below the CBM.…”

Section: ■ Experimental Sectionmentioning

confidence: 97%

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Effects of Nanoscale Surface Lithium Depletion on the Optical Properties and Electronic Band Structures of Lithium Transition-Metal Phosphates

et al. 2020

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The optical absorption properties of lithium transition-metal phosphates (LiTMPO 4 , TM = Mn, Fe, Co, Ni) with nanoscale particle sizes (300−500 nm in diameter) have been measured. The measured edges have been compared with band gaps determined from their corresponding electronic band structure calculations. Various functionals for density functional theory calculations have been compared and validated against experimental results. Gradual increases and intermediate peaks in optical absorption spectra before the main absorption edges have been attributed to intervalence charge transfer between TM 2+ and TM 3+ due to surface Li depletion. The functional, screenedexchange local density approximation (sX-LDA), which includes screened Hartree−Fock exchange, shows the highest overall accuracy for electronic band structure prediction with acceptable computational cost. The voltage plateaus determined from calculated enthalpies also display the best match with calculations using sX-LDA.

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Section: Resultssupporting

confidence: 90%

Section: ■ Experimental Sectionmentioning

confidence: 97%

Effects of Nanoscale Surface Lithium Depletion on the Optical Properties and Electronic Band Structures of Lithium Transition-Metal Phosphates

et al. 2020

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“…This feature is observed in the electrochemistry shown in Figure 4. Higher current values used for cycling can result in lower discharge plateaus in both Li-ion 48 and Li-S 49 batteries. If the sulfur loading of the film is more heterogeneous than we can see with the X-ray and SEM analysis, then it is possible that there are local pockets of an effective higher current.…”

Section: Resultsmentioning

confidence: 99%

Operando Spectromicroscopy of Sulfur Species in Lithium-Sulfur Batteries

Miller

Kasse

Heath

et al. 2017

J. Electrochem. Soc.

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In this study, a novel cross-sectional battery cell was developed to characterize lithium-sulfur batteries using X-ray spectromicroscopy. Chemically sensitive X-ray maps were collected operando at energies relevant to the expected sulfur species and were used to correlate changes in sulfur species with electrochemistry. Significant changes in the sulfur/carbon composite electrode were observed from cycle to cycle including rearrangement of the elemental sulfur matrix and PEO 10 LiTFSI binder. Polysulfide concentration and area of spatial diffusion increased with cycling, indicating that some polysulfide dissolution is irreversible, leading to polysulfide shuttle. Fitting of the maps using standard sulfur and polysulfide XANES spectra indicated that upon subsequent discharge/charge cycles, the initial sulfur concentration was not fully recovered; polysulfides and lithium sulfide remained at the cathodes with higher order polysulfides as the primary species in the region of interest. Quantification of the polysulfide concentration across the electrolyte and electrode interfaces shows that the polysulfide concentration before the first discharge and after the third charge is constant within the electrolyte, but while cycling, a significant increase in polysulfides and a gradient toward the lithium metal anode forms. This chemically and spatially sensitive characterization and analysis provides a foundation for further operando spectromicroscopy of lithium-sulfur batteries. New "beyond lithium-ion" battery chemistries are essential to meet the increasing demand for long-lasting, high capacity energy storage in portable electronics and electric vehicles. Lithium-sulfur (Li-S) batteries are an attractive Li-ion alternative that provides large capacity (1672 mAh g −1 ) and energy density (2500 Wh kg −1 ) while also being low cost, earth-abundant, and lightweight.1-3 Li-S batteries have a unique chemistry that achieves high capacity via chemical transformation rather than Li intercalation. Elemental sulfur (S 8 ) is reduced through a series of soluble Li polysulfides (Li 2 S x , 2 ≤ x ≤ 8) to a final solid discharge product (Li 2 S), and the process is reversed upon charging. [4][5][6] However, Li-S suffers from unrealized theoretical capacity and rapid capacity fade due to loss processes that are not well-understood. 2,7 While many advances in electrode and electrolyte engineering have been made in an attempt mitigate these performance issues, 8-14 a gap remains in the mechanistic understanding of Li-S battery operation. Several mechanisms for reduced capacity and capacity fade have been proposed. Lithium polysulfides, which are necessary for operation, dissolve into the liquid electrolyte, remain dissolved, and "shuttle" between the electrodes rather than participating in the electrochemical reactions, decreasing the amount of active material available. 3,[15][16][17][18] Low sulfur utilization results in initially low capacity that then continues to decrease with subsequent cycles. [19][20][21] Batteries are spatiall...

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“…Fig. 12 shows a typical charging curve of a 69 Though the relative alignment of Fermi levels for LiFePO 4 and FePO 4 has been conrmed experimentally, the relatively smaller difference in experimental work functions for the two phases may be related to the morphology, atmospheric exposure during sample handling, crystal orientation, difficulties with poorly conducting materials, etc. 70 Moreover, a work function lower that the value of the band gap appears unfeasible at rst sight, however, it is not uncommon for materials with large band gaps to display negative electron affinities.…”

Section: Open-circuit Voltagementioning

confidence: 99%

Re-evaluation of experimental measurements for the validation of electronic band structure calculations for LiFePO₄ and FePO₄

et al. 2019

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Suppression of degradation for lithium iron phosphate cylindrical batteries by nano silicon surface modification

Abstract: Si surface modification gets improved electrochemical performances for 18 650 cylindrical cells, especially at elevated temperature, which is attributed to the fact that Si can enable the LiFePO4 electrodes to suppress battery degradation.

Cited by 13 publications

References 45 publications

Effects of Nanoscale Surface Lithium Depletion on the Optical Properties and Electronic Band Structures of Lithium Transition-Metal Phosphates

Effects of Nanoscale Surface Lithium Depletion on the Optical Properties and Electronic Band Structures of Lithium Transition-Metal Phosphates

Operando Spectromicroscopy of Sulfur Species in Lithium-Sulfur Batteries

Re-evaluation of experimental measurements for the validation of electronic band structure calculations for LiFePO₄ and FePO₄

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Suppression of degradation for lithium iron phosphate cylindrical batteries by nano silicon surface modification

Abstract: Si surface modification gets improved electrochemical performances for 18 650 cylindrical cells, especially at elevated temperature, which is attributed to the fact that Si can enable the LiFePO4 electrodes to suppress battery degradation.

Cited by 13 publications

References 45 publications

Effects of Nanoscale Surface Lithium Depletion on the Optical Properties and Electronic Band Structures of Lithium Transition-Metal Phosphates

Effects of Nanoscale Surface Lithium Depletion on the Optical Properties and Electronic Band Structures of Lithium Transition-Metal Phosphates

Operando Spectromicroscopy of Sulfur Species in Lithium-Sulfur Batteries

Re-evaluation of experimental measurements for the validation of electronic band structure calculations for LiFePO4 and FePO4

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Re-evaluation of experimental measurements for the validation of electronic band structure calculations for LiFePO₄ and FePO₄