Mimicking Capacity Degradation in a Lithium Ion Battery Anode in Cells With a Li Metal Electrode: A Perspective on Advantages

The lifetime of Li‐ion batteries (LIB) depends on the amount of Li ions and electrons (= active Li), definingLi inventory and cell capacity and can be limited by active Li loss (ALL) at the negative electrode (= anode), e.g., via electrolyte reduction. Given cathode interference‐reasoned challenges for anode R&D in a LIB, Li metal is commonly applied as a Li source within a half cell. However, applied test protocols do not represent the full cell situation, as (1) anodes get fully recharged each cycle, i.e., not consider ALL from previous cycles and (2) cycling with a fixed charge cut‐off potential (COP) can lead to pronounced capacity deviations as, e.g., already marginal overpotential reaches COP notably earlier, i.e., at lower charge capacities, which is in particular relevant for plateau‐like charge profiles like graphite. Here, an advanced charging protocol via mimicking capacity degradation is provided, which adjusts the specific charge capacities of an individual cycle to previous cycle discharge capacity; hence it considers previous ALL and avoids the COP issue. This allows “fast screening” anode R&D by simulating full cell conditions, e.g., mass loading, N/P ratio, state‐of‐charge, and even prelithiation degree, as exemplarily shown for “next generation” anodes.