High-voltage operation of Li4Ti5O12/AC hybrid supercapacitor cell in carbonate and sulfone electrolytes: Gas generation and its characterization
High-voltage operation of Li4Ti5O12/AC hybrid supercapacitor cell in carbonate and sulfone electrolytes: Gas generation and its characterization
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DOI：
10.1016/j.electacta.2019.01.088
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发表时间：
2019-04
影响因子：
6.6
通讯作者：
Etsuro Iwama;Tsukasa Ueda;Y. Ishihara;K. Ohshima;Wako Naoi;McMahon Thomas Homer Reid;K. Naoi
中科院分区：
文献类型：
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作者：
Etsuro Iwama;Tsukasa Ueda;Y. Ishihara;K. Ohshima;Wako Naoi;McMahon Thomas Homer Reid;K. Naoi
设计一种由Li4Ti5O12(LTO)/活性炭（AC）组成的混合超级电容器，是利用对称交流电极提高超级电容器（SCs）能量密度的有前途的途径之一。然而，在高压运行（>3.0 V）时，故障模式或气体产生对系统至关重要，这在很大程度上取决于电解质的类型。在本研究中，我们研究了LTO/1 M四氟硼酸锂（LiBF4）在碳酸丙烯酯(PC)/AC中的界面现象的电压依赖性。结果表明，当电池电压高于3.0 V时，负LTO电极与电解质之间的界面变得不稳定，对应的电位高于4.5 Vvs。Li/Li+为交流正极。LTO/电解质界面的失稳似乎是由AC正极发生的不可逆反应引起的，伴随着吸收的H2O的释放。用抗水解溶剂乙基异丙基砜（EiPS）取代PC进一步证实了这一假设；基于eips的电解质成功地实现了3.3 V的高压工作，而没有LTO降解，无论交流正极的氧化反应如何，1000次循环后容量保持率为95%。
Designing a hybrid supercapacitor, composed of Li4Ti5O12(LTO)/activated carbon (AC), is one of promising routes to enhance the energy density of supercapacitors (SCs) using symmetrical AC electrodes. At high-voltage operations (>3.0 V), however, the failure mode or gas generation is critical for the system, which is greatly dependent on the type of electrolyte. In this study, we investigated the voltage dependence of the interfacial phenomena of LTO/1 M lithium tetrafluoroborate (LiBF4) in propylene carbonate (PC)/AC. The results reveal that the interface between the negative LTO electrode and the electrolyte becomes unstable at cell voltages above 3.0 V, corresponding to potentials above 4.5 Vvs. Li/Li+for the AC positive electrode. The destabilization of the LTO/electrolyte interface appears to be initiated by an irreversible reaction occurring at the AC positive electrode, accompanied by a release of absorbed H2O. This hypothesis is further confirmed by replacing PC with a hydrolysis-resistant solvent, ethyl isopropyl sulfone (EiPS); the EiPS-based electrolyte successfully realizes a high-voltage operation at 3.3 V without LTO degradation, regardless of the oxidative reaction at the AC positive electrode, with a 95% capacity retention after 1000 cycles.