Poly(ethylene oxide)-co-poly(propylene oxide)-based gel electrolyte with high ionic conductivity and mechanical integrity for lithium-ion batteries.
Using gel polymer electrolytes (GPEs) for lithium-ion batteries usually encounters the drawback of poor mechanical integrity of the GPEs. This study demonstrates the outstanding performance of a GPE consisting of a commercial membrane (Celgard) incorporated with a poly(ethylene oxide)-co-poly(propylene oxide) copolymer (P(EO-co-PO)) swelled by a liquid electrolyte (LE) of 1 M LiPF6 in carbonate solvents. The proposed GPE stably holds LE with an amount that is three times that of the Celgard-P(EO-co-PO) composite. This GPE has a higher ionic conductivity (2.8×10(-3) and 5.1×10(-4) S cm(-1) at 30 and -20 °C, respectively) and a wider electrochemical voltage range (5.1 V) than the LE-swelled Celgard because of the strong ion-solvation power of P(EO-co-PO). The active ion-solvation role of P(EO-co-PO) also suppresses the formation of the solid-electrolyte interphase layer. When assembling the GPE in a Li/LiFePO4 battery, the P(EO-co-PO) network hinders anionic transport, producing a high Li+ transference number of 0.5 and decreased the polarization overpotential. The Li/GPE/LiFePO4 battery delivers a discharge capacity of 156-135 mAh g(-1) between 0.1 and 1 C-rates, which is approximately 5% higher than that of the Li/LE/LiFePO4 battery. The IR drop of the Li/GPE/LiFePO4 battery was 44% smaller than that of the Li/LE/LiFePO4. The Li/GPE/LiFePO4 battery is more stable, with only a 1.2% capacity decay for 150 galvanostatic charge-discharge cycles. The advantages of the proposed GPE are its high stability, conductivity, Li+ transference number, and mechanical integrity, which allow for the assembly of GPE-based batteries readily scalable to industrial levels.
Department of Chemical Engineering and Research Center for Energy Technology and Strategy, National Cheng Kung University , Tainan 70101, Taiwan.
Shih-Hong
SH
Wang
Sheng-Shu
SS
Hou
Ping-Lin
PL
Kuo
Hsisheng
H
Teng
D004553:Electric Conductivity; D011211:Electric Power Supplies; D005782:Gels / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D008094:Lithium / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry; D011095:Polyethylenes / Q000737:chemistry*; D011126:Polypropylenes / Q000737:chemistry*
D005782:Gels; D007477:Ions; C473349:LiFePO4; D010710:Phosphates; D011095:Polyethylenes; D011126:Polypropylenes; C078661:UCON 50-HB-5100; D008094:Lithium; D007501:Iron