Soft Carbon Integration for Prolonging the Cycle Life of LiNi_0.5Mn_1.5O₄ Cathode

Abstract

LiNi0.5Mn1.5O4 (LNMO) has the advantages of high voltage output (4.7 V), fast charging capability, and better thermal stability, which make it suitable for future applications in lithium-ion batteries. However, the limitation in cycle life due to the electrolyte and the structural instability during high-voltage cycling to 5 V is a major drawback. Further, the decomposition of the electrolyte on the highly reactive surface of LNMO plays a critical role in catalyzing the structural disintegration. The issue can be mitigated via the surface carbon coating on LNMO. Herein, a method to integrate soft carbon on LNMO is reported, which bypasses the drawback of lattice oxygen loss during the conventional carbon coating on metal oxides. The soft carbon derived from the pitch precursor with its unique blend of physical properties renders the LNMO surface less susceptible to electrolyte attack. As a result, capacity retention enhances by 25.6%, and the coulombic efficiency improves by 1.5% over 500 cycles in a carbonate-based 1 M LiPF6 electrolyte. The soft carbon regulates the interfacial composition balanced in LiF/Li x PO y F z and reduces the growth of the charger-transfer resistance. Moreover, the strategy also decreases the Mn dissolution by 18%.

Soft carbon in non-aqueous rechargeable batteries: a review of its synthesis, carbonization mechanism, characterization, and multifarious applications

“…Recently, we proposed a post-synthetic modification to integrate 5 wt% petroleum-pitch-derived soft carbon with LNMO slurry by substituting the same weight percentage of carbon black. 160 The graphene-like sheets of the soft carbon encapsulated (not a conventional coating) the truncated octahedron-shaped LNMO particles and the surface thus became less susceptible to electrolyte decomposition (Fig. 6c and d).…”