Thermodynamic and experimental analysis of Ni-Co-Mn carbonate precursor synthesis for Li-rich cathode materials
The Eh-pH diagrams for Ni-Co-Mn-CO3-H2O system at various temperatures and ion concentrations are simulated via OLI studio based on the fundamentals of thermodynamic equilibrium. A co-existence area for NiCO3, CoCO3, and MnCO3 is observed visually from the Eh-pH diagrams, which thermodynamically proves the stability of these species in aqueous solutions, and the possibility of co-precipitating polymetallic carbonate. The simulation results also demonstrate that a higher temperature and/or a more dilute solution are not in favor of the co-precipitation. With the predicted pH ranges from the Eh-pH diagrams, a confirmative experiment was conducted to synthesize Ni0.13Co0.13Mn0.54(CO3)0.8, the precursor for preparing Li1.2Ni0.13Co0.13Mn0.54O2, which is a promising cathode material for next-generation LIBs. The physical properties of both materials are characterized in detail, and the electrochemical performance for the final cathode material was tested. The results show that Ni2+, Co2+, and Mn2+ ions in solution are homogeneously co-precipitated in the form of polymetallic carbonate. The Li1.2Ni0.13Co0.13Mn0.54O2 material obtained from the carbonate precursor has a typical structure of Li- and Mn-rich cathodes and yields an initial discharge capacity of 296.0 mAh g−1 at 0.1 C and 188.1 mAh g−1 after 100 cycles at 1 C rate. It was verified that the OLI-assisted Eh-pH simulation is consistent with the experimental measurements.
KeywordsEh-pH diagrams Li-ion batteries Carbonate precursor Li-rich material
Mr. S. Deng is thankful for the support from Central South University for the CSU Special Scholarship for Study Abroad at the University of Toronto. OLI Systems Inc. is also acknowledged for providing access to the OLI software at the UofT.
This study received financial support from the Government of Chongzuo, Guangxi Zhuang Autonomous Region, China (GC Joint Special Fund No. FA2019015) and Science and Technology Department of Guangxi Zhuang Autonomous Region, China (Guangxi Special Fund for Scientific Center and Talent Resources, No. AD18281073).
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Conflict of interest
The authors declare that they have no conflict of interest.
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