Realization of High Loading Density Lithium Polymer Batteries by Optimizing Lithium-Ion Transport and Electronic Conductivity

Lithium polymer batteries (LPBs) with a high energy density and safety are being actively studied for their use as an energy storage system. However, bottlenecks to their development include charge-transport resistance and poor interfacial contact. In this paper, we introduce carbon nanofiber (CNF) as a conductive additive and the optimization of porosity in the electrode by calendering to realize a high loading density LPB. A simple dispersion strategy is applied to homogeneously disperse nanofiber additives in the electrode to achieve high electronic conductivity. Calendering with optimized pressing degree was performed on the CNF-based electrode to enhance lithium-ion transport and electron conduction in the LPB. The optimal pressing conditions were confirmed by measuring the electronic conductivity, internal resistance, lithium-ion diffusion coefficient, and charge transport characteristics of the cells. When the electrode was pressed by 35%, optimum electrode wettability by solid polymer electrolyte and contact between particles and current collector were achieved, resulting in the high performance of the LPB. Finally, at the optimized pressing degree, we successfully demonstrate 90% cycle retention during 100 cycles and an improvement of the volumetric energy density by over seven-fold.

Automated summary

In this paper, carbon nanofiber (CNF) was introduced as a conductive additive, and the porosity of the electrode was optimized by calendering to achieve a high loading density lithium polymer battery (LPB). A simple dispersion strategy was used to homogeneously disperse nanofiber additives in the electrode, resulting in high electronic conductivity. Calendering with optimized pressing degree improved lithium-ion transport and electron conduction in the LPB. The optimized pressing conditions achieved optimum electrode wettability and contact, leading to high performance of the LPB. Finally, at the optimized pressing degree, 90% cycle retention during 100 cycles and over seven-fold improvement in volumetric energy density were successfully demonstrated.