Construction of Inorganic-Rich Cathode Electrolyte Interphase on Co-Free Cathodes

Abstract

Lithium-rich layered oxides (LRLOs), with the chemical formula of xLi 2 MnO 3 •(1 − x)LiMO 2 , delivering higher specific discharge capacity, are potential cathode materials for lithium-ion batteries. However, the dissolution of transition metal ions and the instability of the cathode-electrolyte interphase (CEI) hinder the commercial application of LRLOs. Herein, a simple and affordable method is developed for the construction of a robust CEI layer by quenching a kind of cobalt-free LRLO, Li 1.2 Ni 0.15 Fe 0.1 Mn 0.55 O 2 (denoted as NFM), in 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether solvent. This robust CEI, with well-distributed LiF, TMF x , and partial organic component CF x , performs as a physical barrier to prevent NFM from direct contact with the electrolyte, suppresses the oxygen release, and ensures the CEI layer stability. The customized CEI with LiF and TMF x -rich phase considerably enhances the NFM cycle stability and the initial coulomb efficiency and inhibits voltage fading. This work provides a valuable strategy for designing stable interface chemistry on the cathode of lithium-ion batteries.

Minimizing ion/electron pathways through ultrathin conformal holey graphene encapsulation in Li- and Mn-rich layered oxide cathodes for high-performance lithium-ion batteries

“…The F 1s peak corresponds to peaks associated with CF 2 , Li x PO y F z , and LiF, which are separated into three peaks at 687.8, 686.5, and 685.4 eV, respectively. 61 The CF 2 peak originates from the PVDF binder, while the Li x PO y F z and LiF peaks can be attributed to the decomposition by-products of the inorganic salt LiPF 6 in the electrolyte. Furthermore, when LiPF 6 decomposes to generate HF, HF attacks the LMR surface, corroding it and promoting irreversible structural changes.…”

Electrolyte Regulation in Stabilizing the Interface of a Cobalt-Free Layered Cathode for 4.8 V High-Voltage Lithium-Ion Batteries

“…Developing new Ni-rich cathodes (LiNi 1‑ x ‑ y ‑ z Mn x Co y Al z O 2 ) and enhancing the upper charge cutoff voltage are considered as the direct way to boost the energy density of LIBs. , Many researches have been done on the structure design for a typical ternary cathode material of LiNi x Co y Mn 1‑ x ‑ y O 2 . , Among these key elements, as the Ni content increases, higher discharge capacity will be obtained, whereas the cation mixture degree increases and the corresponding discharge capacity is reduced if more Co elements are implanted. , Furthermore, the price of cobalt is greatly influenced by the supply chain in the past decade, which limits the availability of cobalt and hinders the growth of the EV market. Instead, Co-free and Ni-rich high-voltage materials are considered as the most promising cathode due to the high specific capacity, low cost, and environment-friendliness. − However, the practical applications of the Co-free high voltage cathode are greatly inhibited by the poor cathode–electrolyte interface (CEI) layer formed on the cathode surface in the carbonated electrolytes containing LiPF 6 salt, especially at voltages higher than 4.4 V. The poor oxidation stability of the carbonate-based electrolyte leads to continuous interfacial side reactions that suppress the Li + migration and increase the cell polarization. , Meantime, the oxygen revolution, fatigue of secondary particles, formation of intergranular crack, and dissolution of transition metal ion that occur at high-voltage conditions further cause the capacity decay and early death of the cell, especially at high operating voltages and elevated temperatures. − …”