The increase of specific energy of current Li ion batteries via further increase of the cell voltage, for example, to 4.5 V is typically accompanied by a sudden and rapid capacity fade, known as “rollover” failure. This failure is the result of Li dendrite formation triggered in the course of electrode cross‐talk, that is, dissolution of transition metals (TMs) from the cathode and deposition on the anode. It is shown herein, that the elimination of ethylene carbonate (EC) from a state‐of‐the‐art electrolyte, that is, from 1.0 m LiPF6 in a 3:7 mixture of EC and ethyl methyl carbonate prevents this failure in high‐voltage LiNi0.5Co0.2Mn0.3O2||graphite cells, even without any electrolyte additives. While the oxidative stability on the cathode side is similar in both electrolytes, visible by a decomposition plateau at 5.5 V versus Li|Li+ during charge, the anode side in the EC‐free electrolyte reveals significantly less TM deposits and Li metal dendrites compared to the EC‐based electrolyte. The beneficial effect of EC‐free electrolytes is related to a significantly increased amount of degraded LiPF6 species, which effectively trap dissolved TMs and suppress the effect of detrimental cross‐talk, finally realizing rollover‐free performance under high voltage conditions.

Lithium ion battery cells operating at high‐voltage typically suffer from severe capacity fading, known as ‘rollover’ failure. Here, the beneficial impact of Li2CO3 as an electrolyte additive for state‐of‐the‐art carbonate‐based electrolytes, which significantly improves the cycling performance of NCM523 ∥ graphite full‐cells operated at 4.5 V is elucidated. LIB cells using the electrolyte stored at 20 °C (with or without Li2CO3 additive) suffer from severe capacity decay due to parasitic transition metal (TM) dissolution/deposition and subsequent Li metal dendrite growth on graphite. In contrast, NCM523 ∥ graphite cells using the Li2CO3‐containing electrolyte stored at 40 °C display significantly improved capacity retention. The underlying mechanism is successfully elucidated: The rollover failure is inhibited, as Li2CO3 reacts with LiPF6 at 40 °C to in situ form lithium difluorophosphate, and its decomposition products in turn act as ‘scavenging’ agents for TMs (Ni and Co), thus preventing TM deposition and Li metal formation on graphite.

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