Atomically tailoring vacancy defects in FeF2.2(OH)(0.8) toward ultra-high rate and long-life Li/Na-ion batteries

Wang, Qun1,2; Yang, Zhenhua1,2; Liu, Hanghui1,2; Wang, Xianyou3; Shi, Xingqiang4

2019-06-21

10.1039/c9ta02649e

Journal of Materials Chemistry A   影响因子和分区

2050-7488

2050-7496

As for FeF2.2(OH)(0.8), introducing appropriate vacancy defects has been recently discovered to be a new experimental method for the improvement of the lithium storage performance. However, owing to the limitation of experimental methods, for Li/Na rechargeable batteries, the vacancy formation mechanism of FeF2.2(OH)(0.8) and its regulation mechanism on the electrochemical properties associated with rate-performance and cycling stability are still poorly understood. Therefore, we carried out first principles calculations to investigate the defect chemistry in FeF2.2(OH)(0.8). Eleven representative vacancy defects, such as neutral iron vacancy (V0Fe), charged iron vacancy (V-Fe(2-) and V-Fe(3-)), neutral oxygen vacancy (V0O), charged oxygen vacancy (V-O(+) and V-O(2+)), neutral hydrogen vacancy (V0H), charged hydrogen vacancy (V-H(-)), neutral hydroxide vacancy (V0OH), charged fluorine vacancy (V-F(+)) and neutral fluorine vacancy (V0F) are included. The vacancy formation energies clearly reveal that FeF2.2(OH)(0.8) with neutral hydroxide vacancy (V0OH) (FeF2.2(OH)(0.64)O-0.080.08) is most likely to form under hydrogen-poor (H-poor) conditions. With the introduction of V0OH, the band gap of FeF2.2(OH)(0.8) reduces from 1.47 eV to 0.99 eV, which contributes to the improvement of electronic conductivity. Moreover, by analysis of the defect structure and Li/Na diffusion process, it was proposed that the ion diffusion channel of FeF2.2(OH)(0.8) is broadened. Besides, the balance between Li/Na ions and surrounding anions also occurs at the saddle point, which induces higher ionic conductivity to appear in FeF2.2(OH)(0.64)O-0.080.08 relative to FeF2.2(OH)(0.8) (5.16 x 10(-4) S cm(-1)vs. 1 x 10(-6) S cm(-1) for Li; 6.88 x 10(-2) S cm(-1)vs. 2.03 x 10(-2) S cm(-1) for Na). Accordingly, FeF2.2(OH)(0.64)O-0.080.08 possesses higher rate performance and more stable discharge voltage than FeF2.2(OH)(0.8). As a whole, our theoretical results successfully clarify the origin of the favorable electrochemical properties of FeF2.2(OH)(0.64)O-0.080.08 during the Li intercalation/deintercalation process in the experiment. Furthermore, they also clearly simulate the process of Na diffusion kinetics and electrochemistry in FeF2.2(OH)(0.8) and FeF2.2(OH)(0.64)O-0.080.08. Furthermore, it is verified that introducing V0OH is an effective strategy to design FeF2.2(OH)(0.8)-based cathode materials for ultra-high rate and long-life Li/Na-ion batteries.

SCI ; EI

英语

其他

Shenzhen Fundamental Research Foundation[JCYJ20170817105007999]

Chemistry ; Energy & Fuels ; Materials Science

Chemistry, Physical ; Energy & Fuels ; Materials Science, Multidisciplinary

WOS:000472566400033

ROYAL SOC CHEMISTRY

20192507060151

Calculations ; Cathodes ; Defects ; Diffusion ; Electric discharges ; Electrochemical properties ; Energy gap ; Fluorine ; Hydrogen ; Ions ; Iron ; Oxygen ; Oxygen vacancies ; Secondary batteries

Iron:545.1 ; Electricity: Basic Concepts and Phenomena:701.1 ; Secondary Batteries:702.1.2 ; Electrochemistry:801.4.1 ; Chemical Products Generally:804 ; Mathematics:921 ; Crystalline Solids:933.1 ; Materials Science:951

Web of Science

1.Xiangtan Univ, Sch Mat Sci & Engn, Key Lab Mat Design & Preparat Technol Hunan Prov, Xiangtan 411105, Hunan, Peoples R China
2.Xiangtan Univ, Sch Mat Sci & Engn, Minist Educ, Key Lab Low Dimens Mat & Applicat Technol, Xiangtan 411105, Hunan, Peoples R China
3.Xiangtan Univ, Sch Chem, Natl Local Joint Engn Lab Key Mat New Energy Stor, Natl Base Int Sci & Technol Cooperat,Hunan Prov K, Xiangtan 411105, Hunan, Peoples R China
4.Southern Univ Sci & Technol, Dept Phys, Shenzhen 518055, Peoples R China

Wang, Qun,Yang, Zhenhua,Liu, Hanghui,et al. Atomically tailoring vacancy defects in FeF2.2(OH)(0.8) toward ultra-high rate and long-life Li/Na-ion batteries[J]. Journal of Materials Chemistry A,2019,7(23):14180-14191.

Wang, Qun,Yang, Zhenhua,Liu, Hanghui,Wang, Xianyou,&Shi, Xingqiang.(2019).Atomically tailoring vacancy defects in FeF2.2(OH)(0.8) toward ultra-high rate and long-life Li/Na-ion batteries.Journal of Materials Chemistry A,7(23),14180-14191.

Wang, Qun,et al."Atomically tailoring vacancy defects in FeF2.2(OH)(0.8) toward ultra-high rate and long-life Li/Na-ion batteries".Journal of Materials Chemistry A 7.23(2019):14180-14191.