Under higher states of delithiation (i.e., high voltage charging), Ni and/or Mn cations are known to migrate to lithium layer tetrahedral and eventually octahedral sites 14, forming defect spinel and rock salt structures 7, 8, 15. Common high-energy commercial layered-structure cathodes like NMC and NCA achieve specific capacities in the range 150–200 mAh/g with moderate charge upper cutoff voltages (UCV) ~4.2 V 5, 6 however using higher voltages to realize higher utilization of these materials towards their theoretical capacities ~275 mAh/g causes increased rate of capacity fade and resistance growth (i.e., lower cycle life) symptomatic of cathode-based degradation mechanisms including phase transitions 7, 8, 9, 10 particle amorphization/pulverization 11, transition metal dissolution 12, and electrolyte decomposition 13.Įlectrolyte decomposition at the cathode surface at high voltage, leading to surface passivation and charge transfer impedance growth with negative impact on cycle life, is highly emphasized in the literature however, the significant contribution of phase transitions to impedance growth has not been as widely recognized, and indeed may be more dominant at higher voltage. As graphite anode materials have a relatively high specific capacity >300 mAh/g and lower cost per unit weight, cathode materials are the limiting component to both energy density and cost per unit energy. For a practical system to be compelling at least a 67% reduction in cell cost and more than a 150% increase in volumetric energy density compared to current state-of-the-art Ni-Mn-Co or NMC/graphite and Ni-Co-Al or NCA/graphite cells, while retaining at least 80% of initial capacity after 1000 100% Depth of Discharge (DoD) cycles 1. Such emerging battery applications demand higher voltage and higher energy density than currently commercially available lithium-ion battery (LIB) technologies, with simultaneous improvements to cost, cycle life, and safety 3, 4. Department of Energy, December 2013) have set aggressive battery performance targets for EVs and grid storage applications, respectively 1, 2. Department of Energy (“Grid Energy Storage”, U.S. The USABC (“USABC Goals for Advanced Batteries for EVs - CY 2020 Commercialization”, USCAR, 2015) and U.S. The ability to mitigate degradation mechanisms for Ni-rich NMC and NCA illustrated in this report provides insight into a method to enable the performance of high-voltage LIBs. EIS confirmed that Al 2O 3-coated materials had significantly lower increase in the charge transfer component of impedance during cycling. High resolution TEM/SAED structural characterization revealed that Al 2O 3 coatings prevented surface-initiated layered-to-spinel phase transitions in coated materials which were prevalent in uncoated materials. Our results show that Al 2O 3 coating improved the NMC cycling performance by 40% and the NCA cycling performance by 34% at 1 C/−1 C with respectively 4.35 V and 4.4 V UCV in 2 Ah pouch cells. In this report, we show that atomic layer deposition (ALD) of titania (TiO 2) and alumina (Al 2O 3) on Ni-rich FCG NMC and NCA active material particles could substantially improve LIB performance and allow for increased upper cutoff voltage (UCV) during charging, which delivers significantly increased specific energy utilization. The energy density of current lithium-ion batteries (LIBs) based on layered LiMO 2 cathodes (M = Ni, Mn, Co: NMC M = Ni, Co, Al: NCA) needs to be improved significantly in order to compete with internal combustion engines and allow for widespread implementation of electric vehicles (EVs).

Nmc cathode sinterizing