The Influence of Synthesis Method on the Local Structure and Electrochemical Properties of Li-Rich/Mn-Rich NMC Cathode Materials for Li-Ion Batteries

Abstract

Electrochemical energy storage plays a vital role in combating global climate change. Nowadays lithium-ion battery technology remains the most prominent technology for rechargeable batteries. A key performance-limiting factor of lithium-ion batteries is the active material of the positive electrode (cathode). Lithium- and manganese-rich nickel manganese cobalt oxide (LMR-NMC) cathode materials for Li-ion batteries are extensively investigated due to their high specific discharge capacities (>280 mAh/g). However, these materials are prone to severe capacity and voltage fade, which deteriorates the electrochemical performance. Capacity and voltage fade are strongly correlated with the particle morphology and nano- and microstructure of LMR-NMCs. By selecting an adequate synthesis strategy, the particle morphology and structure can be controlled, as such steering the electrochemical properties. In this manuscript we comparatively assessed the morphology and nanostructure of LMR-NMC (Li1.2Ni0.13Mn0.54Co0.13O2) prepared via an environmentally friendly aqueous solution-gel and co-precipitation route, respectively. The solution-gel (SG) synthesized material shows a Ni-enriched spinel-type surface layer at the {200} facets, which, based on our post-mortem high-angle annual dark-field scanning transmission electron microscopy and selected-area electron diffraction analysis, could partly explain the retarded voltage fade compared to the co-precipitation (CP) synthesized material. In addition, deviations in voltage fade and capacity fade (the latter being larger for the SG material) could also be correlated with the different particle morphology obtained for both materials.

Deciphering the morphology of transition metal carbonate cathode precursors

“…16,28,29 In the second step, these Mn-rich carbonate precursors are calcined at elevated temperatures with excess lithium salt that oxidizes and lithiates the precursor materials and leads to the formation of LMR-NMC cathode particles. 30 The nal performance of a battery cathode material depends on two aspects: [31][32][33] (a) The atomic crystal structure that determines the maximum cell voltage and lithium capacity under thermodynamic equilibrium conguration. 33 (b) The morphology of the cathode particles, such as the size of the primary and secondary particles, size distribution, internal porosity, etc., which determines the kinetic and transport limitations that prevent the cell from achieving its maximum thermodynamically feasible performance.…”

Status and outlook for lithium-ion battery cathode material synthesis and the application of mechanistic modeling

“…(d) Coulombic efficiency for Li, Mn rich NMC (Li1.2Ni0.13Mn0.54Co0.13O2) synthesized through the sol-gel and co-precipitation route. Adapted from [24]. CC BY 4.0.…”