Polyacrylate polymer is a promising polymer matrix for gel polymer electrolyte (GPE) in lithium-ion batteries . Herein, in-situ polymerized poly(ethylene glycol phenyl etheracrylate) (PEGPEA) based GPE combined with 1 M LiPF6 in ethylene carbonate/dimethyl carbonate/ethyl methyl carbonate (EC/DMC/EMC, 1:1:1 in volume) solvents was introduced. The maximum recoverable strain of the in-situ polymerized PEGPEA-GPE was up to 99%. The outstanding interfacial compatibility between PEGPEA-GPE and the lithium electrode was also obtained. Surprisingly, lithium dendrite was effectively suppressed in charge-discharge cycling because of polymer-enhanced solid electrolyte interphase (SEI) and excellent contact interface. Furthermore, the PEGPEA-GPE exhibited wide electrochemical stability window up to 4.9 V versus Li + /Li, and achieved an ionic conductivity of 3.35 × 10 −3 S cm −1 at 25 °C. When used as electrolyte, the Li[Ni 0.5 Co 0.2 Mn 0.3 ]O 2 /PEGPEA-GPE/Li batteries showed high discharge capacity retention rate of 97.5% after 70 charge-discharge cycles and considerable discharge rate capability, i.e., 155 mAh g −1 0.2C, 142 mAh g −1 0.5C, 120 mAh g −1 1C, 60 mAh g −1 2C. These results demonstrate that this highly elastic in-situ polymerized PEGPEA-GPE is a potential electrolyte system for high-performance polymer electrolyte lithium-ion batteries and has excellent application prospects in wearable and flexible batteries.
This research explores the structural and interfacial regulation mechanisms of multi-element synergistic electrolytes for high voltage LiNi x Co y Mn 1-x-y O 2 (NCM) lithium ion batteries through a combined simulation-experiment approach. Theoretical calculations revealed that difluoroxalate borate ion (DFOB − ) exhibit a pronounced negative electrostatic potential distribution, with a binding energy to Li + (-110.26 kJ/mol) higher than conventional carbonate solvents (e.g., DMC, FEC), thus dominating the formation of anion-enriched solvation sheaths and significantly reducing Li + desolvation energy barriers (<30 kJ/mol). Raman spectroscopy and molecular dynamics simulations confirmed that LiDFOB introduction facilitates the transition of solvation structures from solvent-separated ion pairs (SSIPs) to contact ion pairs (CIPs) and aggregates (AGGs), with CIPs/AGGs proportion increasing from 29 % to 39 %, effectively suppressing LiPF 6 hydrolysis and mitigating electrode structural damage caused by solvent co-intercalation. Electrochemical tests demonstrated that the optimized 0.5 PB modified electrolyte(0.5 M lithium hexafluorophosphate+0.5 M lithium difluoro(oxalato)borate dissolved in a mixed solvent of dimethyl carbonate: fluoroethylene carbonate: propyl p-toluene sulfonate in a ratio of 3:1:1) enabled NCM811||Li half-cells to achieve 88 % capacity retention after 100 cycles at 4.5 V high voltage (versus 58 % for control group), along with stable lithium metal anode cycling for 500 h at 1 mA·cm −2 . Interface analysis revealed that DFOB⁻ and PPTs preferentially undergo redox reactions to form inorganic-rich cathode electrolyte interphase (CEI) films containing borides (LiₓBOyFz) and sulfonates (ROSO₂Li). On the anode side, synergistic effects of DFOB⁻, Propyl p-toluene sulfonate (PPTs) and FEC generate LiF/sulfur/boride-enriched composite solid electrolyte interface (SEI) layers, effectively suppressing transition metal dissolution and graphite structural degradation. This work provides a novel paradigm of "anion coordination-solvation structure-interface functionalization" for high-voltage lithium-ion batteries."
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