The interaction of red phosphorus with supporting carbon additives in lithium-ion battery anodes

Abstract

In theory, red P is a promising alloying-type anode material for Li-ion batteries (LIBs). However, we are challenged by reports of poor electrochemical performance due to P pulverization. So far, our best approach is to use composites of P and C as these dramatically improve the anode's stability in regards to the lithiation/delithiation process. Admittedly, success is dependent on the C additives providing electronic conductivity and structural integrity to the composite whilst also ensuring an adequate P dispersion. Here, three of the most commonly used C additives (carbon nanotubes, reduced graphene oxide and graphite flakes) are compared in their ability to stabilize the capacity of red P and its adherence to the current collector in a LIB. Our experiments show that nanotubes are the most promising stabilization agents due to their mechanical elasticity, high surface area/pore volume, and superior P uptake of their elastic web-like aggregates. As a result, the adherence of the C/P composite to the current collector is ensured. Notwithstanding the additive's performance, we also observe that the interconversion between different P phases is not fully reversible at room temperature, constituting an added reason for the capacity fade of C/P anodes.