Toward a Suitable Anode Surface for High Voltage Li Ion Batteries: Suppressing Transition Metal‐Induced Degradation via a Coordinating Solid Electrolyte Interphase

Abstract

The specific energy of Li ion batteries with layered‐oxide‐based cathodes can be enhanced by enhancing charge cut‐off voltage, which increases both, mean discharge voltage and capacity. However, the increased delithiation capacity facilitates thermodynamically‐driven phase changes and increases transition metal (TM) dissolution, finally initiate a failure cascade, known as “electrode crosstalk”. This can trigger formation of high surface area lithium (HSAL), active Li/capacity loss, and consequently decrease the cycle life. Here, after screening of bio‐based additives, the maleimide (MI) is shown to be even superior compared to the effective and literature‐known TM‐scavenging additive lithium difluorophosphate (LiDFP). Although, the electrode crosstalk and the TM amount on the anode are not suppressed with MI, the anode surface remains intact, and is even free from HSAL deposits. The solid electrolyte interphase (SEI) is shown to consist from oligo and polymer‐based MI decomposition products and is concluded to scavenge TMs on the outer SEI layer via its characteristic coordinating chemistry. This way the TM diffusion toward the inner SEI layer is suppressed, where it otherwise would block the Li+ pathway and initiate the well‐known failure cascades, that is, locally increase resistance, trigger HSAL formation and capacity fade, in worst case rollover failure.