期刊
ACS APPLIED POLYMER MATERIALS
卷 5, 期 8, 页码 5857-5866出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsapm.3c00495
关键词
Lithium-ion batteries; Separator; Direct fluorination; Oxygen groups; Wettability
By direct fluorination treatment, the wettability, electrolyte uptake, ionic conductivity, and stability of the polyethylene separator can be significantly improved.
Due to the intrinsic inertness of polyethylene (PE),it is difficultto induce polar oxygen-containing groups onto the PE separator surfaceunder mild conditions on a large scale and further enhance their wettability.Herein, utilizing the ultrastrong oxidation of elemental fluorine(F-2), it was found that F-2 could easily reactwith the PE separator surface via radical-related routes, and thusoxygen would be naturally captured onto the separator surface forits radical affinity. The fluorinated PE separator exhibited significantlyimproved wettability as the water contact angle decreased from 117 & DEG;to 62 & DEG; at the minimum. Therefore, electrolyte uptake of the fluorinatedseparator reached 803.9% (of which the PE electrolyte uptake was 246.2%),and the ionic conductivity increased from 0.29 to 0.52mS/cm. Capacityretention of LiCoCO2/graphite cells assembled by a fluorinatedPE separator increased to 80.4% from 73.2% after 200 cycles of charge-discharge,and the discharge capacity of it also increased 38.83% (from 79.07mAh/g to 109.77 mAh/g) at 1.2 C. Besides, due to the spontaneous couplingbetween direct fluorination induced radicals, micro-cross-linkingspots were generated, and thus, modulus and thermal deformability,which meant service stability of the separator, were also improved.Therefore, direct fluorination could be considered an effective post-treatmentstrategy for high-performance PE separators.
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