A primed current collector for high performance carbon-coated LiFePO4 electrodes with no carbon additive

Abstract

This work shows that newly developed primed aluminum current collector for positive electrodes allows to vastly improve the electrochemical performance compared to bare aluminum foil for full cells assembled with a C-coated LiFePO4 positive electrode, a graphite negative electrode and a standard carbonate/LiPF6 based electrolyte. Moreover, it is discovered that using a primed collector allows to drastically reduce the carbon additive content in the C-LiFePO4 electrode down to zero, while maintaining a very low impedance and excellent rate capability (80 mAh/g at 5C rate) and cyclability (60% capacity retention after 200 cycles at 2C rate). Comparatively, the same electrode shows no cyclability in the same testing conditions if a bare aluminum foil is used as the collector. Improving the energy density while maintaining good power capability of a Li-ion cell was thus achieved by using an adapted primed current collector. Such performance originates from a significant reduction of the contact resistance at the current collector – electrode interface through the multiplication of electrical contact points and/or the modification of their nature. In complement, this work shows that the carbon coating of the C-LiFePO4 particles is sufficient to ensure a good electrical conductivity within the electrode.