An Overview on Polymer-Based Electrolytes with High Ionic Mobility for Safe Operation of Solid-State Batteries
Authors: Falco Marisa , Lingua Gabriele , Porporato Silvia , Zhang Ying , Zhang Mingjie , Gastaldi Matteo , Gambino Francesco , Maruccia Elisa , Saffirio Sofia , Milanesi Matteo , Darjazi Hamideh , Piovano Alessandro , Meligrana Giuseppina , Elia Giuseppe Antonio , Gerbaldi Claudio 
Published: February 2024

Liquid electrolytes used in commercial Li-ion batteries are generally based on toxic volatile and flammable organic carbonate solvents, thus raising safety concerns in case of thermal runaway. The most striking solution at present is to switch on all solid-state designs exploiting polymer materials, films, ceramics, low-volatile, green additives, etc. The replacement of liquids component with low-flammable solids is expected to improve the safety level of the device intrinsically. Moreover, a solid-state configuration is expected to guarantee improved energy density systems. However, low ionic conductivity, low cation transport properties and issues in cell manufacturing processes must be overcome [1].

Electrochemical performance in lab-scale devices can be readily improved using different RTILs or specific low-volatile additives. Here, an overview is offered of the recent developments in our labs on innovative polymer-based electrolytes allowing high ionic mobility, particularly attractive for safe, high-performing, solid-state Li-metal batteries, and obtained by different techniques, including solvent-free UV-induced photopolymerization. Cyclic voltammetry and galvanostatic charge/discharge cycling coupled with electrochemical impedance spectroscopy exploiting different electrode materials (e.g., LFP, Li-rich NMC, LNMO, Si/C) demonstrate specific capacities approaching theoretical values even at high C-rates and stable operation for hundreds of cycles at ambient temperature [2,3]. Direct polymerization procedures on top of the electrode films are also used to obtain an intimate electrode/electrolyte interface and full active material utilization in both half and full-cell architectures. In addition, results of composite hybrid polymer electrolytes [4] and new single-ion conducting polymers [5] are shown, specifically developed to attain improved ion transport and high oxidation stability for safe operation with high voltage electrodes even at ambient conditions.

References

[1] Ferrari, S.; Falco, M.; Muñoz-García, A.B.; Bonomo, M.; Brutti, S.; Pavone, M.; Gerbaldi, C. Solid-State Post Li Metal Ion Batteries: A Sustainable Forthcoming Reality? Adv. Energy Mater. 2021, 11, 2100785.

[2] Falco, M.; Simari, C.; Ferrara, C.; Nair, J.R.; Meligrana, G.; Nicotera, I.; Mustarelli, P.; Winter, M.; Gerbaldi, C. Understanding the Effect of UV-Induced Cross-Linking on the Physicochemical Properties of Highly Performing PEO/LiTFSI-Based Polymer Electrolytes. Langmuir 2019, 35, 8210-8219.

[3] Lingua, G.; Falco, M.; Stettner, T.; Gerbaldi, C.; Balducci, A. Enabling safe and stable Li metal batteries with protic ionic liquid electrolytes and high voltage cathodes. J. Power Sources 2021, 481, 228979.

[4] Falco, M.; Castro, L.; Nair, J.R.; Bella, F.; Bardé, F.; Meligrana, G.; Gerbaldi, C. UV-Cross-Linked Composite Polymer Electrolyte for High-Rate, Ambient Temperature Lithium Batteries. ACS Appl. Energy Mater. 2019, 2 1600-1607.

[5] Lingua, G.; Grysan, P.; Vlasov, P.S.; Verge, P.; Shaplov, A.S.; Gerbaldi, C. Unique Carbonate-Based Single Ion Conducting Block Copolymers Enabling High-Voltage, All-Solid-State Lithium Metal Batteries. Macromolecules, 2021, 54, 6911-6924.

Acknowledgements

The Si-DRIVE project has received funding from the EU's Horizon 2020 research and innovation program under GA 814464. The PSIONIC project has received funding from the European Union's Horizon Europe Research and Innovation Programme under Grant Agreement N. 101069703.