Abstract
: Medium-Ni, Co-free NMC640/graphite cells have the potential to compete in volumetric energy density with high-Ni materials like NMC811/graphite cells when charged to high voltages like 4.4 V. Employing NMC640 can significantly reduce cost and alleviate the demand for precious transition metals such as Ni and Co. This study focuses on assessing the impact of electrolyte additives on the operation of high voltage NMC640/graphite pouch cells. Initially, various generations of electrolyte additives were screened in NMC442/graphite pouch cells using a rigorous 24-hour voltage-hold protocol at 40°C, targeting an upper cutoff voltage (UCV) of 4.4 V. This approach accelerates the screening process, allowing for quicker identification of promising additives, as cell failures primarily stem from impedance growth and transition metal loss. Subsequently, promising candidates of electrolyte additives were evaluated in NMC640/graphite cells through long-term cycling (CCCV) to UCVs of 4.3 V, 4.4 V, and 4.5 V at temperatures ranging from 20°C to 55°C, employing a conventional CCCV protocol. Figure 1
Published Version
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