Solid State Li Metal/LMO Batteries based on Ternary Triblock Copolymers and Ionic Binders

Abstract

Triblock copolymers containing an ionophilic polymerized ionic liquid block, sandwiched between two ionophobic polystyrene blocks, were investigated as solid polymer electrolytes (SPE) to simultaneously provide mechanically robust, free-standing membranes with high lithium conductivity and an optimized electrolyte composition. The conductivity reached 8 × 10–5 S cm–1 and 6.5 × 10–4 S cm–1 at 30 and 80 °C, respectively, with an anodic stability above 4.5 V. Highly stable Li metal symmetric cycling was demonstrated, with an overpotential of 130 mV for over 300 h at 50 °C at a current density of 0.5 mA cm–2/0.5 mAh cm–2. Attempts were also made to incorporate the SPE as the binder in an LMO cathode formulation. The best cell performance, however, was obtained when substituting the SPE in the LMO cathode formulation with a PMA solid-state gel electrolyte, resulting in a high-performance solid-state Li|polymer eletrolyte|LMO device with stable cycling at C/5, and an impressive capacity retention (i.e., 105 mAh g–1 after 150 cycles at 0.1 mA cm–2) with a Coulombic efficiency around 99.4%.

Current Trends and Perspectives of Polymers in Batteries

“…This allows them to be used with high-voltage cathodes such as the NMC 811 or LMNO. Lithium metal batteries running at 25 °C with high performance have recently been demonstrated. − Future improvements of the PDADMA polymers in terms of mechanical stability or miscibility with new ionic liquid electrolytes are expected by developing new copolymerization strategies. Recent examples of the copolymerization approach to improve the mechanical properties of poly­(ionic liquid)-based polymer electrolytes while retaining their favorable ionic conductivity and lithium transport number are the RAFT polymerized diblock and triblock polymers; when combined with LiFSI and an ionic liquid, the resulting polymer electrolyte was demonstrated to give excellent performance in Li metal batteries. , Interestingly, PDADMA-based polymer electrolytes have shown great versatility and performance in other battery chemistries such as sodium metal batteries. , …”

“…Recent examples of the copolymerization approach to improve the mechanical properties of poly(ionic liquid)-based polymer electrolytes while retaining their favorable ionic conductivity and lithium transport number are the RAFT polymerized diblock and triblock polymers; when combined with LiFSI and an ionic liquid, the resulting polymer electrolyte was demonstrated to give excellent performance in Li metal batteries. 43 , 44 Interestingly, PDADMA-based polymer electrolytes have shown great versatility and performance in other battery chemistries such as sodium metal batteries. 46 , 47 …”

Understanding Polymerized Ionic Liquids as Solid Polymer Electrolytes for Sodium Batteries

“…To address these concerns, the use of block copolymer with elevated molecular weights for the mechanical block has been explored. This further builds upon the favorable outcomes that have been attained with Li-ion-based SPEs through the utilization of reversible addition fragmentation chain transfer (RAFT) polymerization methods to produce meticulously controlled block copolymers. ,,, This study delves into an analogous investigation; in particular, an AB diblock copolymer, PS–PEA­(BuImTFSI) (presented in Figure ), is explored as a potential candidate for an all-solid-state sodium device. To accomplish this, a series of binary (polymer + salt) and ternary (polymer + salt + ionic liquid) electrolytes were fabricated and characterized to understand the effect of SPE composition.…”

Impact of optimised quasi-block structures on the properties of polymer electrolytes

“…As a result, these block copolymer systems are capable of high loading of lithium salts without compromising the mechanical integrity of the resulting electrolyte membranes. 22 This also allows for a higher loading of additional organic liquid electrolytes such as ionic liquids or carbonates to improve ion dynamics. 23,24 Ionic liquids alone are emerging electrolyte materials offering several advantages over traditional solvent-based electrolytes including improved safety, a broader operating temperature range and a wider electrochemical window.…”

“…22 This also allows for a higher loading of additional organic liquid electrolytes such as ionic liquids or carbonates to improve ion dynamics. 23,24 Ionic liquids alone are emerging electrolyte materials offering several advantages over traditional solvent-based electrolytes including improved safety, a broader operating temperature range and a wider electrochemical window. 25,26 Addition of these into block copolymer electrolytes has been shown to enhance the overall SPE performance.…”