热塑性聚氨酯基聚合物电解质的制备与表征

doi:10.13208/j.electrochem.200606

摘要/Abstract

摘要：

采用非溶剂诱导相转化法（NIPS）制备了热塑性聚氨酯/醋酸纤维素（TPU/CA）新型聚合物隔膜。然后,将隔膜浸入液体电解质中得到TPU/CA凝胶聚合物电解质（GPEs）。研究TPU与CA的质量比对GPEs性能的影响。通过X射线衍射（XRD）、扫描电镜（SEM）、热重（TG）、差示扫描量热（DSC）、线性扫描伏安（LSV）、电化学阻抗（EIS）等对TPU/CA膜进行表征。结果表明,在共混隔膜中引入CA可以降低TPU的结晶度,增加隔膜的吸液率。其中,室温下TPU/CA = 7/3基电解质的离子电导率为1.04 mS·cm^-1,电化学窗口为5.1 V(vs. Li/Li⁺)。组装的电池LiFePO₄/TPU/CA/Li在0.5 C循环100次后,仍具有较高的放电比容量和较好的容量保持率,具有良好的循环稳定性。这些结果表明,这种新型的TPU/CA共混GPEs是锂离子电池的理想选择。

关键词: 锂离子电池, 凝胶聚合物电解质, 非溶剂诱导相转化法, 聚氨酯, 醋酸纤维素

Abstract:

Electrolyte still has to be improved to satisfy the increasingly rigid demands of lithium ion batteries that have higher energy densities. Thermoplastic polyurethane (TPU) has two phase structures of soft segments and hard segments, which can guarantee the electrochemical and physical performances of electrolyte for lithium ion battery. It is now creatively applied to the gel polymer electrolyte matrix of lithium ion batteries. In this paper, a novel polymer membrane based on thermoplastic polyurethane/cellulose acetate (TPU/CA) was prepared by non-solvent induced phase separation (NIPS) method. Further, the TPU/CA blending gel polymer electrolyte (GPE) was prepared by absorbing liquid electrolyte. The effects of CA contents on the physical and electrochemical properties of the polymer membranes were studied. The structures, morphologies and performances of the membranes with different ratios of CA to TPU were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TG), differential scanning calorimetry (DSC), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The results show that the addition of CA to the blended polymer resulted in lower crystallinity of TPU and higher liquid uptake capability of electrolyte. The TPU/CA membrane possessed a large pore structure, but maintained sufficient mechanical strength. The decomposition temperature of TPU/CA samples with the weight loss of 5% was above 300℃, indicating good thermal stability of each sample. Among the TPU/CA blend electrolytes, the TPU/CA = 7/3 based electrolyte presented an ionic conductivity of 1.04 mS·cm^-1 with electrochemical stability above 5.1 V (vs. Li/Li⁺) at room temperature. The lithium ion battery with the TPU/CA = 7/3 GPE also exhibited a higher charge-discharge capacity of 150.9 mAh·g^-1 at 0.2 C, and a capacity retention rate of 95.7% at 0.5 C was confirmed after 100 cycles. All of these results demonstrate that this new TPU/CA blended gel polymer electrolyte is a promising candidate for lithium ion batteries.

Key words: lithium ion batteries, gel polymer electrolytes, non-solvent induced phase separation, thermoplastic polyurethane, cellulose acetate

周莉, 吴勰, 薛照明. 热塑性聚氨酯基聚合物电解质的制备与表征[J]. 电化学（中英文）, 2021, 27(4): 439-448.

Li Zhou, Lie Wu, Zhao-Ming Xue. Preparation and Characterization of Thermoplastic Polyurethane-Based Polymer Electrolyte[J]. Journal of Electrochemistry, 2021, 27(4): 439-448.

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	C0	C1	C2	C3	C4
TPU/g	4	3.6	3.2	2.8	2.4
CA/g	0	0.4	0.8	1.2	1.6
DMF/mL	16	16	16	16	16
Thickness/μm	205	215	215	220	210
Porosity/%	62	67	74	78	60
Stress/MPa	9.7	7.3	5.2	3.6	2.3
Strain/%	398	342	302	271	200
Uptake/%	56	160	250	300	150
Resistance/Ω	21.2	16.1	11.9	10.6	15.0
Ionic conductivity/(mS·cm^-1)	0.48	0.67	0.90	1.04	0.70