Modification of Ni-Rich FCG NMC and NCA Cathodes by Atomic Layer Deposition: Preventing Surface Phase Transitions for High-Voltage Lithium-Ion Batteries

Abstract

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.

Impact of Temperature and Discharge Rate on the Aging of a LiCoO2/LiNi0.8Co0.15Al0.05O2Lithium-Ion Pouch Cell

“…The charge transfer resistance originates from the interface of electrolyte and electrodes, particularly the cathode side. [47][48][49][50][51][52] Passive layer growth and phase transitions on the cathode surface lead to a continuous increase of the charge transfer resistance. The massive charge transfer resistance increase at 10 • C may be a crucial cathode structural disordering, which will be verified in the following section by means of DVA and ICA.…”

Toward Low-Cost, High-Energy Density, and High-Power Density Lithium-Ion Batteries

“…110 One especially promising approach to reduce surface reactivity and prolong the cycle life of Nirich NMCs is the development of compositionally graded cathodes with less Ni at the surface. 96,106,107,112,113 These particles typically have a Mn-rich surface and a Ni-rich core. Mn 4+ is electrochemically inactive.…”

“…114 Ultimately, a combination of approaches will likely be needed to produce Ni-rich NMCs with optimum performance. For example, Al-doping 115,116 and surface coating 106,117 are two strategies that have been used to boost capacity retention and improve rate performance in NMCs with concentration gradients.…”

“…102 Electrolyte decomposition products deposit on the cathode surface in the form of Li 2 CO 3 , LiOH, LiF, Li x POF y , polycarbonates, and species specific to electrolyte and cathode compositions. 103,104 Strategies to improve the surface properties include doping, 105 surface coatings, 106,107 and electrolyte additives. 108 These approaches typically result in trade-offs of maximum specific capacity and first cycle coulombic efficiency 109 for decreased impedance rise, thermal stability, and reduced CEI buildup to increase cell-cycle life.…”

Development of Electrolytes for Single Crystal NMC532/Artificial Graphite Cells with Long Lifetime

“…[10][11][12][13][14][15][16][17][18][19][20][21] Recently, J. Li et al showed that single crystal Li[Ni 0.5 Mn 0.3 Co 0.2 ]O 2 (NMC532) materials in NMC532/artificial graphite cells can have excellent long term lifetime with an electrolyte consisting of 2 wt% prop-1-ene-1,3 sultone (PES) + 1 wt % ethylene sulfate (DTD) + 1 wt% tris (trimethylsilyl) phosphite (TTSPi) in 1 M LiPF 6 in ethylene carbonate: ethyl methyl carbonate (3:7 by weight) (this electrolyte is called PES211 here). 22 During testing to 4.4 V at 40…”