Study of the cathode spot on a liquid electrolyte by using highspeed visualization and software of coloured images processing

We explore a novel ether aided superconcentrated ionic liquid electrolyte; a combination of ionic liquid, N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (C3mpyrFSI) and ether solvent, 1,2 dimethoxy ethane (DME) with 3.2 mol/kg LiFSI salt, which offers an alternative ion-transport mechanism and improves the overall fluidity of the electrolyte. The molecular dynamics (MD) study reveals that the coordination environment of lithium in the ether aided ionic liquid system offers a coexistence of both the ether DME and FSI anion simultaneously and the absence of ‘free’, uncoordinated DME solvent. These structures lead to very fast kinetics and improved current density for lithium deposition-dissolution processes. Hence the electrolyte is used in a lithium metal battery against a high mass loading (~12 mg/cm2) LFP cathode which was cycled at a relatively high current rate of 1mA/cm2 for 350 cycles without capacity fading and offered an overall coulombic efficiency of >99.8 %. Additionally, the rate performance demonstrated that this electrolyte is capable of passing current density as high as 7mA/cm2 without any electrolytic decomposition and offers a superior capacity retention. We have also demonstrated an ‘anode free’ LFP-Cu cell which was cycled over 50 cycles and achieved an average coulombic efficiency of 98.74%. The coordination chemistry and (electro)chemical understanding as well as the excellent cycling stability collectively leads toward a breakthrough in realizing the practical applicability of this ether aided ionic liquid electrolytes in lithium metal battery applications, while delivering high energy density in a prototype cell.

Download Full-text

Probing the Na metal solid electrolyte interphase via cryo-transmission electron microscopy

Nature Communications ◽

10.1038/s41467-021-23368-6 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Bing Han ◽

Yucheng Zou ◽

Zhen Zhang ◽

Xuming Yang ◽

Xiaobo Shi ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Solid Electrolyte ◽

Solid Electrolyte Interphase ◽

Metal Electrode ◽

Liquid Electrolyte ◽

Battery Materials ◽

Cryogenic Transmission Electron Microscopy ◽

Transmission Electron ◽

Fluoroethylene Carbonate

AbstractCryogenic transmission electron microscopy (cryo-TEM) is a valuable tool recently proposed to investigate battery electrodes. Despite being employed for Li-based battery materials, cryo-TEM measurements for Na-based electrochemical energy storage systems are not commonly reported. In particular, elucidating the chemical and morphological behavior of the Na-metal electrode in contact with a non-aqueous liquid electrolyte solution could provide useful insights that may lead to a better understanding of metal cells during operation. Here, using cryo-TEM, we investigate the effect of fluoroethylene carbonate (FEC) additive on the solid electrolyte interphase (SEI) structure of a Na-metal electrode. Without FEC, the NaPF6-containing carbonate-based electrolyte reacts with the metal electrode to produce an unstable SEI, rich in Na2CO3 and Na3PO4, which constantly consumes the sodium reservoir of the cell during cycling. When FEC is used, the Na-metal electrode forms a multilayer SEI structure comprising an outer NaF-rich amorphous phase and an inner Na3PO4 phase. This layered structure stabilizes the SEI and prevents further reactions between the electrolyte and the Na metal.

Download Full-text

Enabling highly reversible sodium metal cycling across a wide temperature range with dual-salt electrolytes

Journal of Materials Chemistry A ◽

10.1039/d1ta00842k ◽

2021 ◽

Author(s):

Akila C. Thenuwara ◽

Pralav P. Shetty ◽

Neha Kondekar ◽

Chuanlong Wang ◽

Weiyang Li ◽

...

Keyword(s):

Wide Temperature Range ◽

High Energy ◽

Liquid Electrolyte ◽

Metal Cycling ◽

Temperature Range ◽

Sodium Metal ◽

Wide Range

A new dual-salt liquid electrolyte is developed that enables the reversible operation of high-energy sodium-metal-based batteries over a wide range of temperatures down to −50 °C.

Download Full-text