Toward Practical Li Metal Batteries: Importance of Separator Compatibility Using Ionic Liquid Electrolytes

Abstract

Long-term cycling studies of high capacity Li-metal|lithium iron phosphate (LFP, 3.5 mAh/cm2) cells were carried out using two highly concentrated ionic liquid electrolytes (ILEs). Cells incorporating N-propyl-N-methylpyrrolidinium bis­(fluorosulfonyl)­imide (C3mpyrFSI) or triethylmethyl­phosphonium bis­(fluorosulfonyl)­imide (P1222FSI), with 50 mol % lithium bis­(fluorosulfonyl)­imide (LiFSI) electrolytes were shown to operate for over 180 cycles at 50 °C at a rate of C/2 (1.75 mA/cm2). The choice of separator was identified as a critical factor to enable high areal capacity cycling, with the occurrence of cell failure through a short-circuiting mechanism being particularly sensitive to separator characteristics. Several commercial separators were characterized and tested, and their performance was related to membrane properties such as the MacMullin number, pore size, and contact angle. Celgard 3000 series separators were found to support long-term cycling due to their combination of desirable nanoporosity and wettability. The most compatible cell components were assembled into a pouch cell to further demonstrate the feasibility of ILE incorporation into high-capacity lithium metal batteries for commercial purposes.

Mixed Ionic-Electronic Conductors Based on PEDOT:PolyDADMA and Organic Ionic Plastic Crystals

“…As no transition temperatures were observed by differential scanning calorimetry (DSC) in the range of –70 and 200 °C, dynamic mechanical analysis (DMA) was used to study the thermal transitions of PolyDADMA X polyelectrolytes between 40 and 200 °C [ 31 ] ( Figure S1 ). During DMA measurements, with increasing of temperature, a sharp decay in the storage modulus is usually observed when the material passes through the glass transition, thus T g can be determined from the maximum of tan delta and the concomitant decrease in storage modulus [ 33 ]. In this work, from these DMA data, the T g measured for PolyDADMA CF 3 SO 3 is 154 °C and 152 °C for PolyDADMA Tos.…”

Wetting Phenomena and their Effect on the Electrochemical Performance of Surface‐Tailored Lithium Metal Electrodes in Contact with Cross‐linked Polymeric Electrolytes

“…The strongly varying wetting behavior of SPE and TSPE is expected to have an influence on the electrochemical performance of V‐shaped Li metal electrodes as well. The effect of wettability on the electrochemical characteristics of battery cells are widely discussed for liquid electrolyte systems with separators . However, our findings reveal that the difference of wettability in case of cross‐linked PEs, which is rarely discussed in literature, could be also regarded as key parameter to explain the overpotential evolution during cycling in Li|PE|Li cells.…”

“…The effect of wettability on the electrochemical characteristics of battery cells are widely discussed for liquid electrolyte systems with separators. [47] However,our findings reveal that the difference of wettability in case of cross-linked PEs,which is rarely discussed in literature,could be also regarded as key parameter to explain the overpotential evolution during cycling in Li j PE j Li cells.Asshown in Figure S3 ,apositive correlation between enhanced wettability and improved cycling stability was also observed at the interface between Li metal electrodes and garnet-type SE pellets by preheating at 175 8 8C( 5 8 8Cl ower than the Li metal melting point) before cycling at room temperature. [48]…”

Benetzungsvorgänge und ihr Einfluss auf die elektrochemischen Eigenschaften von oberflächenangepassten Lithium‐Metall‐Elektroden in Kontakt mit quervernetzten Polymer‐Elektrolyten

“…Auf Basis der stark unterschiedlichen Benetzungseigenschaften des SPE und des TSPE ist ebenfalls ein Einfluss auf die elektrochemische Leistung der V‐förmig dekorierten Li‐Elektroden zu erwarten. Der Einfluss der Benetzungsfähigkeit auf die elektrochemischen Eigenschaften von Batteriezellen bei Verwendung von Flüssigelektrolytsystemen mit Separatoren ist ein viel diskutierter Punkt . Die erzielten Ergebnisse zeigen jedoch, dass die Unterschiede der Benetzungsfähigkeit im Falle quervernetzter PEs, welche kaum in der Literatur thematisiert werden, ebenfalls als Schlüsselparameter angesehen werden kann, um die Überspannungsentwicklung während der Zyklisierung in Li|PE|Li‐Zellen zu erklären.…”