Unique Carbonate-Based Single Ion Conducting Block Copolymers Enabling High-Voltage, All-Solid-State Lithium Metal Batteries

Abstract

Safety and high-voltage operation are key metrics for advanced, solid-state energy storage devices to power low- or zero-emission HEV or EV vehicles. In this study, we propose the modification of single-ion conducting polyelectrolytes by designing novel block copolymers, which combine one block responsible for high ionic conductivity and the second block for improved mechanical properties and outstanding electrochemical stability. To synthesize such block copolymers, the ring opening polymerization (ROP) of trimethylene carbonate (TMC) monomer by the RAFT-agent having a terminal hydroxyl group is used. It allows for the preparation of a poly(carbonate) macro-RAFT precursor that is subsequently applied in RAFT copolymerization of lithium 1-[3-(methacryloyloxy)propylsulfonyl]-1-(trifluoromethylsulfonyl)imide and poly(ethylene glycol) methyl ether methacrylate. The resulting single-ion conducting block copolymers show improved viscoelastic properties, good thermal stability ( T onset up to 155 °C), sufficient ionic conductivity (up to 3.7 × 10 –6 S cm –1 at 70 °C), and high lithium-ion transference number (0.91) to enable high power. Excellent plating/stripping ability with resistance to dendrite growth and outstanding electrochemical stability window (exceeding 4.8 V vs Li + /Li at 70 °C) are also achieved, along with enhanced compatibility with composite cathodes, both LiNiMnCoO 2 – NMC and LiFePO 4 – LFP, as well as the lithium metal anode. Lab-scale truly solid-state Li/LFP and Li/NMC lithium-metal cells assembled with the single-ion copolymer electrolyte demonstrate reversible and very stable cycling at 70 °C delivering high specific capacity (up to 145 and 118 mAh g –1 , respectively, at a C/20 rate) and proper operation even at a higher current regime. Remarkably, the addition of a little amount of propylene carbonate (∼8 wt %) allows for stable, highly reversible cycling at a higher C-rate. These results represent an excellent achievement for a truly single-ion conducting solid-state polymer electrolyte, placing the obtained ionic block copolymers on top of polyelectrolytes with highest electrochemical stability and potentially enabling safe, practical Li-metal cells operating at high-voltage.

Crosslinked xylose-based polyester as a bio-derived and degradable solid polymer electrolyte for Li+-ion conduction

“…, Miller) 15 and polycarbonates ( e.g. , Tominaga, 16 Brandell, 17 and Mecerreyes 18,19 ) have also been studied for SPE applications, as well as more sophisticated materials such inorganic/polymer composites, 20–22 block co-polymers, 23–30 single-ion conducting polymers 24,31,32 and crosslinked polymers. 33–36 Among the latter category, Jang, Kim and co-workers recently reported impressive ionic conductivity close to the practical requirement ( ca.…”

Single‐Ion Lithium Conducting Polymers with High Ionic Conductivity Based on Borate Pendant Groups

“…The versatility of the methacrylic chemistry should allow one to use these monomers in different polymer formulations such as gel cross-linked networks, random or block copolymers. [2,15,[17][18][19] This should lead to an improvement in its ionic conductivity values. To prove this, a single-ion gel cross-linked polymer electrolyte based on LBB(OGlyO6FiP) monomer was formulated by rapid UV photopolymerization in the presence of a PEG-diacrylate crosslinker (20 %wt.)…”

“…These values of ionic conductivity in homopolymers remain low for proper battery operation. For this reason, ionic transport and the ionic conductivity values are increased by formulation of the SLIPCE with plasticizers, [2,15] blending with flexible polymeric matrices such as PEO [16] or block copolymerization. [17][18][19] The main objective of this work is to report the synthesis of an innovative family of anionic monomers based on the highly delocalized asymmetric borate group and their homopolymers, which show very high ionic conductivity for a single-ion polymer electrolyte.…”

Single‐Ion Lithium Conducting Polymers with High Ionic Conductivity Based on Borate Pendant Groups

“…The versatility of the methacrylic chemistry should allow one to use these monomers in different polymer formulations such as gel cross-linked networks, random or block copolymers. [2,15,[17][18][19] This should lead to an improvement in…”

“…These values of ionic conductivity in homopolymers remain low for proper battery operation. For this reason, ionic transport and the ionic conductivity values are increased by formulation of the SLIPCE with plasticizers,[ 2 , 15 ] blending with flexible polymeric matrices such as PEO [16] or block copolymerization. [ 17 , 18 , 19 ] The main objective of this work is to report the synthesis of an innovative family of anionic monomers based on the highly delocalized asymmetric borate group and their homopolymers, which show very high ionic conductivity for a single‐ion polymer electrolyte.…”