High-energy nickel cobalt manganese oxides have been studied intensively as cathode materials for lithium-ion batteries. However, several hurdles need to be overcome to adopt these cathodes in commercial lithium-ion batteries. Herein, aluminum oxide (Al 2 O 3 ) coating was applied to high-energy nickel cobalt manganese oxides (HE-NCM, Li 1.33 Ni 0.27 Co 0.13 Mn 0.60 O 2+d ) by atomic layer deposition (ALD) and its effects on HE-NCM/graphite full cells were investigated. HE-NCM/graphite full cells have better cycling performance and efficiency when HE-NCM is coated with Al 2 O 3 . ICP-MS measurements show that the Al 2 O 3 coating can effectively prevent transition metal dissolution from HE-NCM. XPS and FT-IR analysis suggests that the surface film on HE-NCM cathodes does not change significantly with the Al 2 O 3 coating even after 50 cycles, however the surface film on graphite anodes shows a significant change. The resistance of graphite electrodes cycled with the uncoated HE-NCM is higher than that of graphite electrodes cycled with the Al 2 O 3 -coated HE-NCM due to the increased SEI thickness. The improved cycling performance of HE-NCM/graphite cells with Al 2 O 3 coating can be attributed to the minimized resistance increase on graphite as well as the suppression of cathode active material loss.
LiNi0.5Mn1.5O4 (LNMO), which has an operating voltage of 4.8 vs Li/Li+ and a theoretical capacity of 147 mAh g−1, is an interesting cathode material for advanced lithium ion batteries. However, electrolyte decomposition at the electrode can gradually decrease the capacity of the battery. In this study, the surface of the LNMO cathode has been modified with phosphoric acid (PA) to improve the capacity of the LNMO/graphite full cell. Modification of LNMO cathodes by PA is confirmed by surface analysis. Additionally, the presence of lithium bis-(oxalato) borate (LiBOB) as an electrolyte additive further enhances the performance of PA modified LNMO/graphite cells. The improved performance of PA modified cathodes and electrolytes containing LiBOB can be attributed to the suppressed Mn and Ni deposition on the anode. Elemental analysis suggests that the Mn and Ni dissolution is significantly reduced compared to unmodified LNMO/graphite cells with standard electrolyte.
Silicon is a promising anode material for lithium ion batteries due to the high theoretical capacity (∼3600mAh/g). However, silicon-based electrodes face rapid degradation due to the extensive volume variation (∼300%) during the lithiation/delithiation process. Binders used in the electrode fabrication play a crucial role for silicon electrodes since it can reduce the mechanical fracture during the cycling process. Recent investigations suggest that in addition to the importance of the mechanical properties of the binder, the chemical reactions between the binder and the surface of the silicon particles also contribute to stabilization. Further investigations suggest that functionalized small molecules can also modify the surface of silicon particles and stabilize cycling. An inexpensive, environmentally friendly alternative has been investigated as a binder for silicon electrodes. Casein is a milk protein found in bovine milk rich in amine groups and carboxylic acid groups which can form bonds with the silanol groups in silicon. A comparative study conducted between PVDF and Casein as binders have shown that when casein was used as binder, it shows better performance compared to PVDF. Surface morphology and solid electrolyte interphase (SEI) was analyzed using electron microscopy techniques and spectroscopic methods and the results will be discussed.
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