Developing “Polymer‐in‐Salt” High Voltage Electrolyte Based on Composite Lithium Salts for Solid‐State Li Metal Batteries

Abstract

The stringent demands for lithium salts make the design of "polymerin-salt" type solid electrolyte restricted since it was proposed in 1993. Herein, a novel polymer-in-salt solid electrolyte is developed via a supramolecular strategy based on poly(methyl vinyl ether-alt-maleic anhydride) (PME) and novel single-ion lithiated polyvinyl formal (LiPVFM)/lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) composite salts (Dual-Li). Hydroxyl of LiPVFM in Dual-Li forms a strong hydrogen bond with the carboxylic acid group generated by the partial ring-opening reaction of maleic anhydride in PME. Meanwhile, PME with abundant carbonyl enables the improved LiTFSI coordination in the polymer/salt composites. As a result, the greatly enhanced mutual solubility of PME and Dual-Li is of importance to build a "polymer-in-salt" solid electrolyte (PISE), which exhibits high ionic conductivity of 3.57 × 10 -4 S cm -1 , wide electrochemical window beyond 5 V, and superior lithium-ion transference number of 0.62 at 25 °C as well as excellent interfacial compatibility with electrodes. The as-assembled LiCoO 2 ||Li solid batteries present prominent high-voltage cyclability with 89.2% capacity retention in 225 cycles. Furthermore, LiNi 0.7 Mn 0.2 Co 0.1 O 2 ||Li pouch cells exhibit remarkable safety even under harsh conditions. The study offers a promising strategy to address the high voltage compatibility and interfacial issues using PISE in solid-state batteries.

In situ prepared “polymer-in-salt” electrolytes enabling high-voltage lithium metal batteries

“…12 Recently, poly(vinylidene fluoride- co -hexafluoropropylene)-based, poly(methyl vinyl ether- alt -maleic anhydride)-based and polyethylene oxide-based PISE have been reported to improve electrochemical performance. 13–15…”

“…12 Recently, poly(vinylidene uorideco-hexauoropropylene)-based, poly(methyl vinyl ether-altmaleic anhydride)-based and polyethylene oxide-based PISE have been reported to improve electrochemical performance. [13][14][15] Nevertheless, PISEs have usually been prepared in selfstanding lms before being integrated into cells, which is denoted as the ex situ method. 16,17 Accordingly, there are similar problems that the solvent residue in electrolytes is generally believed to decrease anodic stability as a result of reactions with the anode surface.…”

Design of Polymer‐in‐Salt Electrolyte for Solid State Lithium Battery with Wide Working Temperature Range

“…Lian et al developed a novel polymer-in-salt solid electrolyte polymer by supramolecular strategy with poly(methyl vinyl ether-alt-maleic anhydride) (PME) and novel single-ion lithiated polyvinyl formal (LiPVFM)/LiTFSI. [36] Hydroxyl of LiPVFM and the partial ring-opening reaction of maleic anhydride in PME generated carboxyl groups to form strong hydrogen bonds. The carbonyl-rich PME also improves the coordination effect of LiTFSI in solid electrolytes.…”

In Situ Construction of a Liquid Film Interface with Fast Ion Transport for Solid Sodium-Ion Batteries

“…A sodium metal anode with a low potential (−2.71 V vs SHE) and a high theoretical capacity (1166 mAh g –1 ) has been considered to be an ideal anode for the next generation of sodium-ion batteries (SIBs). − However, the traditional SIBs with liquid nonaqueous electrolyte are usually accompanied by some challenges such as continuous side reaction, severe dendrites growth, and safety issues. − Solid electrolytes have attracted more and more attention recently because of their high ionic conductivity, excellent chemical/electrochemical stability, and high mechanical strength. − Moreover, solid electrolyte collocated with a high-voltage cathode will play an important role in the field of electric vehicles and energy storage . However, the poor interface contact and large interface resistance seriously hinders the further development of solid sodium-ion batteries (SSIBs). , …”

“…9−13 Moreover, solid electrolyte collocated with a high-voltage cathode will play an important role in the field of electric vehicles and energy storage. 14 However, the poor interface contact and large interface resistance seriously hinders the further development of solid sodium-ion batteries (SSIBs). 15,16 As we all know, there must be a point-to-point contact at the interface since both electrode and electrolyte are solid for SSIBs, which will cause excessive interface resistance and local polarization during cycling process.…”