The energy density of current lithium-ion batteries (LIBs) based on layered LiMO2 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). In this report, we show that atomic layer deposition (ALD) of titania (TiO2) and alumina (Al2O3) 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. Our results show that Al2O3 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. High resolution TEM/SAED structural characterization revealed that Al2O3 coatings prevented surface-initiated layered-to-spinel phase transitions in coated materials which were prevalent in uncoated materials. EIS confirmed that Al2O3-coated materials had significantly lower increase in the charge transfer component of impedance during cycling. 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.

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Low cost, high energy and long cycle life Lithium-ion batteries are the technology of choice widespread implementation of high-performance electric vehicles (EVs). In spite of the strides technology has made, current high energy density solutions suffer from well understood and catastrophic degradation mechanisms that have prevented to full fruition of lithium- and manganese-rich NMC cathode materials. Capacity, power, and voltage fade, excessive SEI growth, electrolyte oxidation, cathode dissolution, structural degradation, and phase transformations are only few of the mechanisms that have been identified. Layered-to-spinel phase transformations at high voltages (~4.8 V), are a main contributor to voltage fade in LMR-NMC-based batteries. Here we show that TiO2 and Al2O3 atomic layer deposition (ALD) coatings applied to NMC powder, conformally coating active material particle surfaces, create a cathode artificial SEI layer which alters and slows the chemical pathways for nucleation and propagation of layered-to-spinel phase transformations at high voltages. XRD, TEM, and magnetic susceptibility characterization of active materials before cycling and at end of cycle life in 95x64 mm pouch cells (~2.5Ah) showed decreased extent of phase transformation with coated NMC compared to uncoated. XALT Energy’s integrated cell design and manufacturing makes 95x64 mm cell performance representative of large format (216x216 mm) production EV cells, demonstrating the validity and scalability of this approach.

Low cost, high energy and long cycle life Lithium-ion batteries are the technology of choice widespread implementation of high-performance electric vehicles (EVs). In spite of the strides technology has made, current high energy density solutions suffer from well understood and catastrophic degradation mechanisms that have prevented the full fruition of NCA cathode materials. There is growing evidence that the cathode surface is the initiation site of all the above mechanisms, motivating the use of larger particle sizes to minimize surface area and mitigate degradation. However, larger particle sizes decrease the overall rate of diffusion of lithium ions, causing a loss of activation of Li-rich phases and an increased loss of capacity at higher rates. Here we show that Al2O3 and TiO2 ALD coatings applied to NCA powder, completely covering active material particle surfaces, create a cathode artificial SEI layer which facilitates an improved Li-ion diffusion pathway, increasing the rate capability of NCA cathodes even with larger particle sizes. Electrochemical analyses showed increased rate capability in 95x64 mm pouch cells (~2.5Ah) with coated NCA compared to uncoated, and XRD and TEM were used to characterize the underlying favorable interactions of coatings with the cathode surface. XALT Energy’s integrated cell design and manufacturing makes 95x64 mm cell performance representative of large format (216x216 mm) production EV cells, demonstrating the validity and scalability of this approach.