| Nowadays lithium- ion batteries(LIB) play a vital role in the society because of their application in electric vehicles and power grids. Nevertheless, with the further development of high-power and high-energy electric vehicles, LIB is still restricted by the insufficient energy density. The application of high operating voltage cathode materials is an important approach to further increase the energy density of LIBs. However, operation in the high- voltage range of LIBs inevitably results in rapid capacity fading over numerous cycles. The critical concern is mainly due to that more interfacial side reactions will take place between active electrode and the electrolyte fo r cell under the high charge cutoff voltage, which lead to the formation of solid electrolyte interface(SEI) layer with higher resistance thus deterioration of battery performance. It can relieve these drawbacks by using the gel polymer electrolyte(GPE) for lithium ion batteries,which not only retains the characteristics of liquid lithium- ion batteries, but also it has the properties of well-design, battery capacity, charge& discharge efficiency, and environmental friendly. The paper emphatically introduced that three kinds of electrolytes lithium salts were designed and synthesized. Their various electrochemical performances were tested. Some creative results obtained are as follow:1. This study explores a rigid-flexible gel polymer electrolyte(GPE) based on based on robust PET nonwoven fabric skeletal nonwoven fabric incorporated with poly(ethyl α-cyanoacrylate) swelled by a liquid electrolyte(LE) of 1 M LiPF6 in carbonate solvents. This GPE shows an enhanced mechanical strength(38 MPa), wide electrochemical voltage range window(4.7 V) and a higher ionic conductivity(2.6 × 10-3 S cm-1) at room temperature. Besides, the gel polymer electrolyte remarkably improves the cyclic stability of the N i-rich NCM full-cells, especially at an elevated voltage. Capacity retention increased from 80 to 91% after 200 cycles at potential range of 3.0 ~ 4.3 V, and from 20 to 77% at potential range of 3.0 ~ 4.6 V. Moreover, the gel polymer electrolyte also improves the high coulombic efficiency because of retarding the decomposition of electrolyte and the dissolution of active material.2. We explored a sustainable and rigid- flexible coupling cellulose-supported poly(propylene carbonate)(PPC) polymer electrolyte by facile solution-casting method. The feasibility of applying the PPC-GPE to high performance LBs is explored by testing mechanical properties, electrochemical stability, ionic conductivity and interfacial compatibility. The results show that the GPE shows a smooth and nonporous structure and the incorporating of robust cellulose as skeleton effectively surmounts the drawback of poor mechanical integrity of the gel polymer electrolyte and the polymer electrolyte exhibited wider electrochemical window(up to 5.0 V), higher ion transference number(0.75) and higher ionic conductivity(1.14 mS cm-1) compared to liquid electrolyte with commercial separator at 25 °C. Thus, 5 V high voltage batteries with this kind polymer electrolyte display excellent capacity retention and superior rate performance for at room temperature.3. Nowadays lithium–sulfur(Li–S) batteries are attractive due to their high energy density but suffering the soluble polysulfide shuttling both electrodes thus severe capacity degradation. Here, we firstly fabricate a composite polymer electrolyte based on poly(propylene carbonate)(PPC) coating on the cellulose separator and modified by carbon paper to be applied in Li-S battery. The battery using this composite polymer electrolyte exhibits a highly initial reversible capacity of 1400 mAh g-1 at 0.2 C with sluggish capacity loss cycling, even with commercially available pristine sulfur as cathode material. This fascinating study demonstrates an effective process of retarding of polysulfides, providing an easy way towards practical Li–S batteries. |
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