Enhanced Electrochemical Capacity of Spherical Co‐Free Li_1.2Mn_0.6Ni_0.2O₂ Particles after a Water and Acid Treatment and its Influence on the Initial Gas Evolution Behavior

Abstract

Li‐rich layered oxides (LRLO) with specific energies beyond 900 Wh kg−1 are one promising class of high‐energy cathode materials. Their high Mn‐content allows reducing both costs and the environmental footprint. In this work, Co‐free Li1.2Mn0.6Ni0.2O2 was investigated. A simple water and acid treatment step followed by a thermal treatment was applied to the LRLO to reduce surface impurities and to establish an artificial cathode electrolyte interface. Samples treated at 300 °C show an improved cycling behavior with specific first cycle capacities of up to 272 mAh g−1, whereas powders treated at 900 °C were electrochemically deactivated due to major structural changes of the active compounds. Surface sensitive analytical methods were used to characterize the structural and chemical changes compared to the bulk material. Online DEMS measurements were conducted to get a deeper understanding of the effect of the treatment strategy on O2 and CO2 evolution during electrochemical cycling.

In-depth structural characterization of the influence of Li+ excess on spherical, Co-free layered LiMn0.5Ni0.5O2 cathode material using correlative Raman–SEM microscopy

“…Nevertheless, compared to LRLO materials (Fig. 1, green line) with a strongly distinct plateau at ≈4.5 V, 45,72–75,79 the plateau in the voltage profile of the presented powders is less pronounced, likely due to the higher Li/Mn ratio and very dense particle morphology (Li 1.10 and Li 1.16 ) of the investigated materials. Based on the SEM images, we additionally estimate a low specific surface area, which strongly influences the activation of the Li 2 MnO 3 domains as well.…”

“…67,68 Specific plateaus, that would indicate phase transitions or electrochemical activation as in Li 2 MnO 3 -containing LRLO materials, are not present. 45,69 The voltage profiles of the other electrodes show a slightly different behavior in the voltage region beyond 4.4 V. With higher amount of excess Li + , a plateau region is observable with increasing length, concomitant with decreasing charge capacity below 4.4 V. Furthermore, the first cycle irreversible capacity loss increases. A detailed analysis is presented in the ESI (Fig.…”

Oxygen vacancy in Li-rich Mn-based cathode materials: origination, influence, regulation and characterization

“…As shown in Fig. 16(l), 98 the reduced gas (including oxygen and carbon dioxide) was observed by DEMS when charging to 4.8 V, which provides evidence for an inhibited oxygen loss and improved reversible anion redox of LRMOs.…”

“…Copyright 2016, John Wiley and Sons. (L) DEMS, reproduced with permission 98. Copyright 2022, John Wiley and Sons.…”

Limiting voltage and capacity fade of lithium-rich, low cobalt Li1.2Ni0.13Mn0.54Fe0.1Co0.03O2 by controlling the upper cut-off voltage

“…Besides, there is the degradation of the different components of the electrodes such as the binder, conductive additive, and the electrolyte. Several strategies have been adopted to stabilize the crystal structure and decrease the voltage and capacity drop of Li-rich NMC cathode material including surface coating, [31][32][33][34][35][36] doping, 29,[37][38][39][40][41][42][43][44][45] structural modication, [46][47][48][49][50][51][52][53] lithium extraction, [54][55][56][57] and electrolyte modication. [58][59][60][61][62][63][64] Controlling the cut-off voltage can be also an effective strategy for stabilizing the crystal structure and decreasing the capacity and voltage drop of Li-rich NMC cathode materials.…”