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Title: Tuning Li-Ion Diffusion in α-LiMn 1–xFe xPO 4 Nanocrystals by Antisite Defects and Embedded β-Phase for Advanced Li-Ion Batteries

Olivine-structured LiMn 1–xFe xPO 4 has become a promising candidate for cathode materials owing to its higher working voltage of 4.1 V and thus larger energy density than that of LiFePO 4, which has been used for electric vehicles batteries with the advantage of high safety but disadvantage of low energy density due to its lower working voltage of 3.4 V. One drawback of LiMn 1–xFe xPO 4 electrode is its relatively low electronic and Li-ionic conductivity with Li-ion one-dimensional diffusion. In this paper, olivine-structured α-LiMn 0.5Fe 0.5PO 4 nanocrystals were synthesized with optimized Li-ion diffusion channels in LiMn 1–xFe xPO 4 nanocrystals by inducing high concentrations of Fe 2+–Li + antisite defects, which showed impressive capacity improvements of approaching 162, 127, 73, and 55 mAh g –1 at 0.1, 10, 50, and 100 C, respectively, and a long-term cycling stability of maintaining about 74% capacity after 1000 cycles at 10 C. By using high-resolution transmission electron microscopy imaging and joint refinement of hard X-ray and neutron powder diffraction patterns, we revealed that the extraordinary high-rate performance could be achieved by suppressing the formation of electrochemically inactive phase (β-LiMn 1–xFe xPO 4, which is first reported in this work) embeddedmore » in α-LiMn 0.5Fe 0.5PO 4. Because of the coherent orientation relationship between β- and α-phases, the β-phase embedded would impede the Li + diffusion along the [100] and/or [001] directions that was activated by the high density of Fe 2+–Li + antisite (4.24%) in α-phase. Thus, by optimizing concentrations of Fe 2+–Li + antisite defects and suppressing β-phase-embedded olivine structure, Li-ion diffusion properties in LiMn 1–xFe xPO 4 nanocrystals can be tuned by generating new Li + tunneling. Finally, these findings may provide insights into the design and generation of other advanced electrode materials with improved rate performance.« less
Authors:
 [1] ;  [2] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [3] ;  [4] ; ORCiD logo [5] ;  [6] ; ORCiD logo [1]
  1. Peking Univ. Shenzhen Graduate School, Shenzhen (China). School of Advanced Materials
  2. Forschungszentrum Julich (Germany). Julich Centre for Neutron Science. Peter Grunberg Inst.
  3. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). NIST Center for Neutron Research
  4. Argonne National Lab. (ANL), Argonne, IL (United States). Electrochemical Technology Program. Chemical Sciences and Engineering Division
  5. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab.
  6. Brookhaven National Lab. (BNL), Upton, NY (United States). Sustainable Energy Technologies Dept.
Publication Date:
Report Number(s):
BNL-114552-2017-JA
Journal ID: ISSN 1530-6984; TRN: US1800333
Grant/Contract Number:
SC0012704; 2016YFB0700600; 21603007; 51672012; JCYJ20150729111733470; JCYJ20151015162256516
Type:
Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 17; Journal Issue: 8; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Research Org:
Brookhaven National Lab. (BNL), Upton, NY (United States); Peking Univ. Shenzhen Graduate School, Shenzhen (China)
Sponsoring Org:
USDOE; National Natural Science Foundation of China (NNSFC); Shenzhen Science and Technology (China)
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; Fe2+-Li+ antisite; high-rate capabilities; LiMn1-xFexPO4; lithium-ion battery; β-LiMn1-xFexPO4
OSTI Identifier:
1412728