Designing electrolytes for lithium metal batteries with rational interface stability
- PDF / 774,449 Bytes
- 3 Pages / 595.276 x 790.866 pts Page_size
- 28 Downloads / 281 Views
RARE METALS
HIGHLIGHT
Designing electrolytes for lithium metal batteries with rational interface stability Chen-Xuan Xu, Jian-Jun Jiang*
Received: 21 September 2020 / Revised: 27 September 2020 / Accepted: 13 October 2020 Ó GRINM Bohan (Beijing) Publishing Co., Ltd 2020
Lithium (Li)-ion batteries (LIBs) have promoted the development of portable electronics and electric vehicles [1, 2]. However, with the rapid increase in energy demand, it is increasingly urgent to develop batteries with high energy density [3]. Li metal batteries (LMBs) are considered as the ‘‘Holy Grail’’ which have attracted much attention due to the high theoretical capacity (3860 mAhg-1) and low redox potential (- 3.040 V vs. the standard hydrogen electrode) [4, 5]. However, before the practical application of LMBs, there are two pressing problems to be solved: one is the growth of Li dendrites and the other is low coulomb efficiency (CE) [6]. In the last few decades, enormous research has proven that the solid electrolyte interphase (SEI) layer with high uniformity and stability can effectively suppress the growth of lithium dendrites [7]. So, electrolyte engineering is used to facilitate the formation of stable SEI due to the significant impact and low cost. Recently, two papers in Angewandte Chemie International Edition [8] and Nature Communications [9] reported two new electrolyte systems to repress the growth of Li dendrites and improve the long-term performance of LMBs. Fu et al. [8] introduced lithium nitrate (LiNO3) into high concentration 3.25 molL-1 lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-sulfolane (SL) electrolyte. As the concentration of LiTFSI increases, the solvation rate of SL increases, while free SL decreases accordingly. Moreover, the addition of LiNO3 further increases the solvated SL, because the NO3- is easier to obtain electrons than TFSIfrom Li? then produces a higher electron affinity (2.12 eV) in the density functional theory (DFT) calculation. Among C.-X. Xu, J.-J. Jiang* School of Physics and Electronics, Hunan University, Changsha 410082, China e-mail: [email protected]
the Li||Cu half-cells, the cell using 3.25 molL-1 LiTFSI0.1 molL-1 LiNO3-SL shows high stability and high average CE of 98.5%, indicating that the high solvation rate of SL is assisted to reduce the production of dead Li. In addition, the electrolyte viscosity decreases with the addition of hydroflurane (HFE) [10]. So, the average CE is increased to 99.0%. As results, a uniform lithium metal surface without dendrites is obtained in the 3.25 molL-1 LiTFSI0.1 molL-1 LiNO3-SL electrolyte due to the high solvation rate of SL and low electrolyte viscosity. Furthermore, the NO3- has participated in the solvation shell of Li? and promotes the fracture of the C–F bond in TFSI-; thus, more LiF is produced in SEI when the presence of LiNO3. Meanwhile, LiNxOy components are also detected in the deeper SEI. The LiF-LiNxOy rich SEI formed in the 3.25 molL-1 LiTFSI-0.1 molL-1 LiNO3-SL electrolyte is more stable and possessed smaller impeda
Data Loading...
