Robust AlF₃ Atomic Layer Deposition Protective Coating on LiMn_1.5Ni_0.5O₄ Particles: An Advanced Li-Ion Battery Cathode Material Powder

Abstract

The most promising LiMn 1.5 Ni 0.5 O 4 (LMNO) ultrahigh voltage cathode material is not yet commercialized because it is suffering from capacity fading during cycling, especially at elevated temperatures. Manganese ions dissolution from the cathode and their precipitation on the graphite anode are the main cause of failure of Li-ion batteries (LIBs) utilizing LMNO cathode material. In order to mitigate this issue, an AlF 3 layer was coated directly on LMNO powder particles via atomic layer deposition (ALD). A few nanometer thick coating was individually formed on each particle. The coating protected the particles from the corrosion-like phenomenon, when immersed in LIB electrolyte at room temperature (RT) and at 45 °C. Half-cell electrochemical measurements showed superior performance for the ALD coated AlF 3 material over the uncoated material. In the full-cell configuration enhanced capacity retention was observed for cells comprised from cathode materials coated by different AlF 3 ALD coatings. Complete Li-ion cells utilizing ALD coated cathode powder in the cathode and a graphite anode exhibited lower initial capacity, which was recovered continuously during cycling at RT and dramatically at 45 °C during the first ∼30 cycles. A different and modified formation process and cycling method significantly improved the lower initial capacity of the Li-ion cells on the expense of a rather shorter cycle life. Even with the new formation cycling, Li-ion cells utilizing ALD coated materials exhibited better cycling performance than cells utilizing pristine material. Fluorination of oxygen impurities in the coating layer or its lithiation are suggested as mechanisms for the recovered capacity. Li-ion cells utilizing ALD AlF 3 coated cathode powder were cycled up to 180 cycles, when 150 of them were at 45 °C. KEYWORDS: particle by particle, AlF 3 , ALD coating, LiMn 1.5 Ni 0.5 O 4 powder, Li-ion batteries

Realizing Superior Cycle Stability of a Ni‐Rich Layered LiNi0.83Co0.12Mn0.05O2 Cathode with a B2O3 Surface Modification

“…Surface coating is regarded as a simple, direct and effective method to alleviate these issues. To date, metal oxides, metal fluoride, phosphates and graphene have been employed as surface coating layers to raise the interfacial stability. For example, a TiO 2 ‐coated LiNi 0.8 Co 0.15 Al 0.05 O 2 exhibited a higher capacity retention of 85 % after 200 cycles compared to that of a pristine electrode (only 36 %), and an Al 2 O 3 ‐coated LiNi 0.8 Co 0.15 Al 0.05 O 2 could deliver 195 mAh g −1 after 60 cycles at 2.8–4.5 V, whereas a pristine cathode only delivered 173 mAh g −1 .…”

Surface modification of LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode materials with Li 2 O‐B 2 O 3 ‐LiBr for lithium‐ion batteries

“…[11][12][13] To solve these issues, some strategies (such as surface modification and ion doping) have been employed to improve NCM523. 14 Metal oxides [15][16][17] (such as Al 2 O 3 , ZnO, and TiO 2 ), fluorides 18,19 (such as LiF and AlF 3 ), and phosphates 20 are commonly used as coating materials to protect the electrode material by preventing it from contacting electrolyte. 21,22 Furthermore, to obtain better lithium-ion conductivity, superionic conductors were explored as the coating materials.…”

An alternative means of advanced energy storage by electrochemical modification

“…It has been reported to be able to inhibit further decomposition of the electrolyte during cycling and widen the stable voltage window [12]. Currently, the formation of this layer can also be achieved by atomic layer deposition technology [2,13]. However, the electrochemical coating is certainly the most economical.…”