Studies of the Electrochemical Behavior of LiNi_0.80Co_0.15Al_0.05O₂Electrodes Coated with LiAlO₂

Abstract

In this paper, we studied the influence of LiAlO 2 coatings of 0.5, 1 and 2 nm thickness prepared by Atomic Layer Deposition onto LiNi 0.8 Co 0.15 Al 0.05 O 2 electrodes, on their electrochemical behavior at 30 and 60 • C. It was demonstrated that upon cycling, 2 nm LiAlO 2 coated electrodes displayed ∼3 times lower capacity fading and lower voltage hysteresis comparing to bare electrodes. We established a correlation among the thickness of the LiAlO 2 coating and parameters of the self-discharge processes at 30 and 60 • C. Significant results on the elevated temperature cycling and aging of bare and LiAlO 2 coated electrodes at 4.3 V were obtained and analyzed for the first time. By analyzing of X-ray diffraction patterns of bare and 2 nm coated LiNi 0.8 Co 0.15 Al 0.05 O 2 electrodes after cycling, we concluded that cycled materials preserved their original structure described by R-3m space group and no additional phases were detected. The lithium-ion batteries (LIB) market nowadays has expanded widely from cellular phones, computers and other electronic devices to the automotive industry. Positive electrodes for LIBs to be explored in electric vehicles are mainly based on lithiated transition-metal oxides comprising Ni, Co and Mn (LiNi y Co x Mn 1-y-x O 2 ) and designated as NCM.1,2 They have attracted much attention as promising materials and therefore many research projects have been dedicated to them in the past 20 years. [3][4][5][6][7][8][9][10][11][12][13] In studies of LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM333) cathodes, it was demonstrated 4-6 that they provided a capacity of 200 mAh/g in the voltage range of 2.5-4.6 V, or ∼155 mAh/g if the cutoff voltage is limited by 4.3 V.7 A substantially improved high-voltage performance of NCM333 electrodes (up to 4.6 V) was achieved by introducing tris(2,2,2-trifluoroethyl) borate additive in the electrolyte solution.8 These authors suggest that the additive takes part in the formation of the solid-electrolyte interface by lowering and stabilization of the interfacial resistance. NCM333 and NCM424 materials were studied in our group from the viewpoint of their electrochemical behavior, aging mechanisms, thermal properties, and surface chemistry developed upon cycling in ethylene carbonate-dimethyl carbonate/LiPF 6 based solutions.9 LiNi y Co x Mn 1-y-x O 2 materials with higher Ni content (y > 5) are important due to high capacity that can be extracted by charging up to 4.3 V only. However, Ni-rich NCMs suffer from their low cycling stability especially for compositions with Ni ≥ 60%, severe capacity fading and impedance increase during cycling at elevated temperatures (e.g. 45• C). One of the effective ways to stabilize the structure of NCM materials, to increase cycling activity and to diminish the heat evolution of the electrodes in a charged 14 There is a consensus in the literature that the above drawbacks originate from the unstable Ni 4+ ions developed in the charge state (high anodic potential, most Li + extracted from NCA). These Ni-ions can be readily reduce...

Surface/Interface Structure Degradation of Ni‐Rich Layered Oxide Cathodes toward Lithium‐Ion Batteries: Fundamental Mechanisms and Remedying Strategies

“…Now that the parasitic side reactions start from the interfaces between the solid cathodes and liquid electrolytes, the most effective method is to avoid their direct contact by introducing passive physical protection layer on the cathode surface . In general, the employed coating species can be categorized into i) the chemically and electrochemically inactive coatings, including metal oxides (Al 2 O 3 , TiO 2 , MgO, SiO 2 , ZrO 2 , V 2 O 5 , Nb 2 O 5 , ZnO, MoO 3 , and Y 2 O 3 ,) and phosphates (AlPO 4 , MnPO 4 , Mn 3 (PO 4 ) 2 , La(PO 4 ) 3 , Ni 3 (PO 4 ) 2 , Co 3 (PO 4 ) 2 , ZrP 2 O 7 , and FePO 4 ) as well as some fluorides (AlF 3 and LiF); ii) the Li + conductive coatings, mainly refer to the Li‐containing compounds such as LiAlO 2 , Li 2 ZrO 3 , Li 3 VO 4 , Li 2 MnO 3 , LiMn 2 O 4 , Li 3 PO 4 (LPO), LiFePO 4 (LFP), LiMnPO 4 , Li 2 TiO 3 , LiTiO 2 , Li 2 O‐2B 2 O 3 , LiTi 2 (PO 4 ) 3 , LiZr 2 (PO 4 ) 3 , Li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 , Li 0.5 La 0.5 TiO 3 , LiTaO 3 , Li 4 SiO 4 , and LiAlF 4 as well as some heterostructured electrochemical active cathodes (Li 1.2 Ni 0.2 Mn 0.6 O 2 , Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 and NCM333); and iii) the electron conducting coating, representatively, reduced graphene oxide (rGO), permeable poly (3,4‐ethylenedioxythiophene) (PEDOT),…”

Synthesis and Characterization of Nano SnO2 Modification on LiNi0.8Mn0.1Ni0.1O2 Cathode Materials for Lithium Ion Batteries

“…The materials selected for coating are mainly some substances with relatively stable chemical properties, such as oxides, fluorides, salts and polymers. As previously reported, AlF 3 , Al 2 O 3 , TiO 2 , ZnO, Li 4 SiO 4 , LiAlO 2 , and SnO 2 (Yang et al, 2012;Lee et al, 2013;Wang et al, 2015;Dai et al, 2016;Lai et al, 2016;He et al, 2017;Srur-Lavi et al, 2017;Liua et al, 2018;Zheng et al, 2018;Xie et al, 2019) were used as effective coating materials for lithium battery cathode materials. The coated materials contribute to more stable SEI film, which can slow down the decomposition of electrolyte and protect bulk materials from corrosion during charging and discharging.…”

Surface Modification Strategies for Improving the Cycling Performance of Ni‐Rich Cathode Materials

“…This sets ALD apart from chemical bath deposition or line‐of‐sight techniques, such as physical vapor deposition, which create thicker films on the surface of particles but do not reach into pores and cracks of rough surfaces of the CAM secondary particles. For Ni‐rich NCMs and NCAs, the technique has been used to deposit Al 2 O 3 ,, LiAlO 2 , LiAlF 4 , Li 3 PO 4 and TiO 2 . However, many of the available ALD coating materials and routes are unexplored to date or have only been tested for low‐Ni CAMs.…”