Single-Ion-Conducting Gel Polymer Electrolyte Based on Lithiated Nafion

Abstract

The use of gel polymer electrolytes (GPEs) is recognized as a promising strategy to improve the safety characteristics of current lithium-ion batteries (LIBs) due to the incorporation of polymer matrix and immobilization of the liquid phase. To achieve high performance and efficient Li+ transport in GPEs, the selection of polymer is critically important. Herein, a single-ion-conducting GPE with a high lithium-ion transference number is proposed with lithiated Nafion (Li-Nafion) and polyacrylonitrile (PAN) polymers. We found that the interactions between electron-withdrawing CN groups Li+ facilitate fast Li+ transport and reduce the Li+ migration barrier of Li+ on the −SO3 – groups. As a consequence, the designed GPE shows a high lithium-ion transference number of 0.93, an admirable ionic conductivity of 1.93 × 10–4 S cm–1, and a wide electrochemical stability window up to 5.0 V at 30 °C. Further validation of the Li|LiFePO4 cell shows a decent cycling performance with an initial discharge specific capacity of 126.1 mAh g–1 and a high capacity retention of 90.1% after 200 charge/discharge cycles at 1C. This study provides a strategy of Li-Nafion and a “decoupling” polymer to enhance the GPE performance and its applications on LIBs.

Perfluorosulfonic Acid Membranes as Gel-Polymer Electrolytes for Lithium Metal Batteries

“…54−56 After cycling for 70 cycles at 0.1 C, capacity retention was 98.8, 99.9, 96.3, and 94.4% for cells with Aquivion-87-EC− DMA, Aquivion-98-EC−DMA, Aquivion-87-EC−PC, and Aquivion-98-EC−PC electrolytes, respectively. The resulting LFP|Li cell performance at room temperature is comparable to existing literature data for other single-ion conducting polymer electrolytes, 21,26,57 and for cells with liquid electrolytes, 53,58 which indicates the possibility of using the investigated membranes as electrolytes in lithium metal batteries.…”

“…Solvation of such membranes by organic aprotic solvents provides high values of ionic conductivity which can reach values of 10 –4 –10 –3 S/cm at room temperature. Several examples of the application of Nafion-type membranes in lithium-ion or lithium-metal batteries have been described in the literature. − However, to date, there is only one work using the Aquivion membrane with a short side chain as an electrolyte in a battery with a lithium metal anode . Lithium–sulfur batteries utilizing Aqiuvion membranes as electrolytes exhibited increased capacity compared to batteries utilizing electrolytes based on Nafion membranes …”

Nafion-212 Membrane Solvated by Ethylene and Propylene Carbonates as Electrolyte for Lithium Metal Batteries

“…The authors declare no conflict of interest. The performance of the Li|Nafion-212-EC-PC|LFP cell at room temperature is comparable with data for other single-ion conducting polymer electrolytes or even surpasses them [18,19,55]. This comparison is also true for cells with liquid electrolytes [51,54,56].…”

“…A further temperature decrease leads to a significant decrease in electrochemical capacity due to lower electrolyte conductivity and a slower transfer rate of solvated lithium cation at the electrolyte/SEI interfaces, along with changes in the kinetics of the electrode reaction for LiFePO 4 /FePO 4 transformation [53,54]. The performance of the Li|Nafion-212-EC-PC|LFP cell at room temperature is comparable with data for other single-ion conducting polymer electrolytes or even surpasses them [18,19,55]. This comparison is also true for cells with liquid electrolytes [51,54,56].…”

“…Nafion membrane is a commonly used polymer (ionomer) that consists of a nonpolar polytetrafluoroethylene matrix and a side chain -O-CF 2 -CF(CF 3 )-O-CF 2 -CF 2 -SO 3 Li, which effectively delocalizes negative charge. Nafion membranes solvated by organic polar aprotic solvents, which are commonly used in conventional lithium-ion batteries, exhibit high ionic conductivity (10 −4 S/cm), high Li + transference numbers (>0.9), and stable battery performance when used as electrolytes [17][18][19][20][21][22][23]. As solvents for the solvation of membranes, it is possible to use various aprotic organic solvents used in liquid electrolytes, such as linear and cyclic carbonates, esters, sulfoxides, etc.…”