Preparation and characterization of flexible self-supported electrodes for lithium-ion batteries from nanofibrillated cellulose

摘要

In this work, nanofibrillated cellulose (NFC), LiFePO4 (LFP), and graphene (GR) were used as raw materials to prepare a flexible self-supporting electrode. NFC shows excellent mechanical properties and flexibility. NFC is used as the skeleton of the flexible electrode, coupling LFP and GR to form a conductive network structure. The Flexible electrodes show excellent flexibility and bendability. The mass of the flexible electrode no longer decreased significantly at temperature higher than 400 degrees C. The final residual rate of the flexible electrode is about 58%. The surface resistance of the flexible electrode is found to decrease by 93% with the content of LFP increasing from 25 to 45 wt%. The flexible electrode also shows higher electrochemical reaction activity and higher reversibility of Li+ extraction/intercalation with the increase of LFP and GR. At 0.1 C rate, the first discharge capacity is 121.47 mAh g(-1), 146.76 mAh g(-1) and 167.74 mAh g(-1) for NFC/GR/LFP flexible electrode with 25 wt%, 35 wt%, and 45 wt% LFP, respectively. After 60 cycles of cycling, the capacity retention rate remains above 98%. Under 5 C rate, the first discharge capacity of these electrodes decrease to 29.87 mAh g(-1), 77.41 mAh g(-1), 99.84 mAh g(-1), respectively, and after 770 cycles, the capacity retention rate is still above 90%. The AC impedance of the NFC/GR/LFP flexible electrodes with LFP content of 25 wt%, 35 wt%, and 45 wt% is 40 omega, 15 omega, and 9 omega, respectively. The above results show that the flexible electrode exhibits excellent mechanical and electrochemical properties. The flexible electrode shows very high capacity retention rate no matter at low scan rate and or high scan rate. The cycle stability can be further enhanced by increasing the loading of active materials.

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