It is widely accepted
that the commercial application of lithium–sulfur
batteries is inhibited by their short cycle life, which is primarily
caused by a combination of Li dendrite formation and active material
loss due to polysulfide shuttling. Unfortunately, while numerous approaches
to overcome these problems have been reported, most are unscalable
and hence further hinder Li–S battery commercialization. Most
approaches suggested also only tackle one of the primary mechanisms
of cell degradation and failure. Here, we demonstrate that the use
of a simple protein, fibroin, as an electrolyte additive can both
prevent Li dendrite formation and minimize active material loss to
enable high capacity and long cycle life (up to 500 cycles) in Li–S
batteries, without inhibiting the rate performance of the cell. Through
a combination of experiments and molecular dynamics (MD) simulations,
it is demonstrated that the fibroin plays a dual role, both binding
to polysulfides to hinder their transport from the cathode and passivating
the Li anode to minimize dendrite nucleation and growth. Most importantly,
as fibroin is inexpensive and can be simply introduced to the cell
via the electrolyte, this work offers a route toward practical industrial
applications of a viable Li–S battery system.