  Lithium-sulfur (Li-S) batteries have become one of the most attractive
alternatives over conventional Li-ion batteries due to their high theoretical
specific energy density (2500 Wh/kg for Li-S vs. $\sim$250 Wh/kg for Li-ion).
Accurate state estimation in Li-S batteries is urgently needed for safe and
efficient operation. To the best of the authors' knowledge, electrochemical
model-based observers have not been reported for Li-S batteries, primarily due
to the complex dynamics that make state observer design a challenging problem.
In this work, we demonstrate a state estimation scheme based on a
zero-dimensional electrochemical model for Li-S batteries. The nonlinear
differential-algebraic equation (DAE) model is incorporated into an extend
Kalman filter. This observer design estimates both differential and algebraic
states that represent the dynamic behavior inside the cell, from voltage and
current measurements only. The effectiveness of the proposed estimation
algorithm is illustrated by numerical simulation results. Our study unlocks how
an electrochemical model can be utilized for practical state estimation of Li-S
batteries.
