TY - JOUR
T1 - Comparing the Ion-Conducting Polymers with Sulfonate and Ether Moieties as Cathode Binders for High-Power Lithium-Ion Batteries
AU - Tsao, Chih Hao
AU - Yang, Tang Kai
AU - Chen, Kun You
AU - Fang, Chan En
AU - Ueda, Mitsuru
AU - Richter, Felix H.
AU - Janek, Jurgen
AU - Chiu, Chi Cheng
AU - Kuo, Ping Lin
N1 - Funding Information:
The authors would like to thank the Ministry of Science and Technology, Taipei, R.O.C., for their support of this research under the Grants of MOST 108-2923-E-006-008, MOST 108-3116-F-006-012-CC1, and MOST 109-3116-F-006-021-CC1. The authors also acknowledge the financial support by the Hierarchical Green-Energy Materials (Hi-GEM) Research Center from The Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (MOE) in Taiwan. J.J. and F.H.R. acknowledge financial support within the BMBF project Evabatt (03XP0134C) and the DAAD project 57448730.
Publisher Copyright:
©
PY - 2021/3/3
Y1 - 2021/3/3
N2 - Two types of ion-conducting polyimides with sulfonate or ether functional groups were synthesized as ion-type or coordination-type cathode binders for lithium-ion batteries (LIBs), respectively. Although superior ion transport abilities have been reported for both types of ion-conducting polymers, their electrochemical performances are significantly different and the corresponding transport mechanisms at the electrolyte/electrode interface remain elusive. Here, we combine experimental and computational techniques to investigate the cathode interface in the presence of both functional polymer binders in comparison with the poly(vinylidene fluoride) (PVDF) binder as reference. A broad shoulder in the cyclic voltammogram accompanied by a poor rate performance of battery tests was observed for a LiFePO4 cathode with coordination-type ether-based polyimide (EPI) binder. In contrast, a LiFePO4 cathode with ion-type sulfonated polyimide (SPI) binder exhibits smaller concentration polarization, achieving satisfactory capacity at high current density. Simulations show that the ether-based binder strongly coordinates Li ions and thus slows the diffusion of Li ions. This leads to the reduction of the LIB electrochemical performance at a high C-rate. In contrast, the negative moiety of the SPI binder leads to less localization of Li ions, allowing a slightly higher Li-ion mobility. Conventional PVDF shows no affinity to Li ions, leading to less Li-ion accumulation at the electrode/electrolyte interface. Yet, the cathode surface covered with PVDF shows the lowest Li-ion diffusivity compared to those with the two types of Li-ion-conducting binders. Therefore, cathodes with SPI and PVDF binders show less polarization at the electrode interface and allow higher C-rate performance of LIBs. The combined results provide a comprehensive understanding of the mechanism of ion conduction in ion- and coordination-type Li-ion-conducting polymer binders. This gives valuable insight into the design of next-generation polymer materials for high-power LIBs.
AB - Two types of ion-conducting polyimides with sulfonate or ether functional groups were synthesized as ion-type or coordination-type cathode binders for lithium-ion batteries (LIBs), respectively. Although superior ion transport abilities have been reported for both types of ion-conducting polymers, their electrochemical performances are significantly different and the corresponding transport mechanisms at the electrolyte/electrode interface remain elusive. Here, we combine experimental and computational techniques to investigate the cathode interface in the presence of both functional polymer binders in comparison with the poly(vinylidene fluoride) (PVDF) binder as reference. A broad shoulder in the cyclic voltammogram accompanied by a poor rate performance of battery tests was observed for a LiFePO4 cathode with coordination-type ether-based polyimide (EPI) binder. In contrast, a LiFePO4 cathode with ion-type sulfonated polyimide (SPI) binder exhibits smaller concentration polarization, achieving satisfactory capacity at high current density. Simulations show that the ether-based binder strongly coordinates Li ions and thus slows the diffusion of Li ions. This leads to the reduction of the LIB electrochemical performance at a high C-rate. In contrast, the negative moiety of the SPI binder leads to less localization of Li ions, allowing a slightly higher Li-ion mobility. Conventional PVDF shows no affinity to Li ions, leading to less Li-ion accumulation at the electrode/electrolyte interface. Yet, the cathode surface covered with PVDF shows the lowest Li-ion diffusivity compared to those with the two types of Li-ion-conducting binders. Therefore, cathodes with SPI and PVDF binders show less polarization at the electrode interface and allow higher C-rate performance of LIBs. The combined results provide a comprehensive understanding of the mechanism of ion conduction in ion- and coordination-type Li-ion-conducting polymer binders. This gives valuable insight into the design of next-generation polymer materials for high-power LIBs.
UR - http://www.scopus.com/inward/record.url?scp=85102421558&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85102421558&partnerID=8YFLogxK
U2 - 10.1021/acsami.0c20657
DO - 10.1021/acsami.0c20657
M3 - Article
C2 - 33594888
AN - SCOPUS:85102421558
VL - 13
SP - 9846
EP - 9855
JO - ACS applied materials & interfaces
JF - ACS applied materials & interfaces
SN - 1944-8244
IS - 8
ER -