An electrolyte to improve the deep charge–discharge performance of LiNi0.8Co0.15Al0.05O2 cathode

Yang

ACS Appl. Mater. Interfaces

et al. 2019

Enhancing the stability of the interface between the electrode and electrolyte at high voltages is crucial concerning the development of Li-ion batteries with high energy densities. Application of some additives in the electrolyte is not only the simplest but also the most effective way to form a protection layer against the electrolyte decomposition and the electrolyte corrosion to the electrode. Herein, we introduce trimethyl borate (TMB) as an additive of the commercial electrolyte to ameliorate the performance of a LiCoO2 cell charged to 4.5 V because its addition lowers the oxidation potential of the baseline electrolyte (3.75 V vs 4.25 V). By being oxidized preferentially and thus forming a compact protection layer of about 25 nm thick on the cathode surface, the additive suppresses the electrolyte decomposition and protects the LiCoO2 cathode against the structural degradation. The capacity retention of the cell after 100 cycles between 2.5 and 4.5 V at 0.1 C increases from 64 to 81% when 2.0 wt % TMB is added into the baseline electrolyte. The X-ray photoelectron spectroscopic results demonstrate the oxidation of TMB on the cathode and therefore the suppressed decomposition of the electrolyte. The results of the X-ray diffraction and Raman spectroscopy show the better structural maintenance of the LiCoO2 material in the TMB-containing electrolyte. The protection mechanism of the TMB additive was comprehensively studied.

Section: Resultsmentioning

confidence: 99%

Trimethyl Borate as Film-Forming Electrolyte Additive To Improve High-Voltage Performances

Yang

ACS Appl. Mater. Interfaces

et al. 2019

“…42 Consequently, less LiF is detected on the cathodes in the TMB-containing electrolytes. Moreover, the appearance of the B−F bond (687 eV) 43 on the cathode surface in the TMB-containing electrolyte is assigned to TMB decomposition. It is believed that the protective effect of borate-containing CEI is due to the existence of the B−F bond.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Synergy Effect of Trimethyl Borate on Protecting High-Voltage Cathode Materials in Dual-Additive Electrolytes

ACS Appl. Mater. Interfaces

Yang

et al. 2021

The lack of electrolyte that is stable under high potentials hinders the application of high-voltage cathode materials for lithium batteries; the introduction of electrolyte additives is clearly the most effective solution to address this issue. Herein, we investigated the synergistic effects of trimethyl borate (TMB) in two dual-additive electrolytes on protecting the LiNi0.8Co0.1Mn0.1O2 and LiCoO2 cathode materials under high potentials. The interactions of TMB with fluoroethylene carbonate and the catalysis of the decomposition product of TMB to tetramethylene sulfone lower the onset oxidation potential of these additives and are beneficial in forming a stable cathode electrolyte interphase film on the cathode materials. This work sheds light on another way of electrolyte designing for high-voltage cathode materials.

“…Without a protective layer, the pristine cathode deteriorated immediately in the first cycle and showed a capacity lower than the theoretical values. Nevertheless, both of the electrodes showed a typical NCA profile 65‐67 …”

Section: Resultsmentioning

confidence: 99%

“…Nevertheless, both of the electrodes showed a typical NCA profile. [65][66][67] During the lithiation/delithiation of cathodes, Li-rich and Li-deficient regions occur in the same particle. These regions can create coherency strains, and the particle needs an overpotential to be delithiated.…”

Section: Electrochemical Characterizationsmentioning

confidence: 99%

Nafion‐coated LiNi₀_.₈₀Co₀_.₁₅Al₀_.₀₅O₂ (NCA) cathode preparation and its influence on the Li‐ion battery cycle performance

et al. 2020

One of the main problems of LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA) materials is the side reactions occurring during battery cycling. These side reactions result in capacity fading, which in turn decreases the life span of the battery. Conventionally, for nickel-rich cathodes, an inorganic layer is used as a protective layer. Applying these layers may require additional complicated steps. To overcome this problem, we focused on coating the NCA electrode with a polymeric ion conductive layer that can easily be applied. For this purpose, using an ionconductive polymer is a novel approach. We used Nafion as the protective layer on NCA electrodes. While the Nafion layer can protect the surface against the side reactions, it does not prevent the Li + ion flow. Following this purpose, we synthesized NCA by a modified co-precipitation method followed by sintering at 750 C. After the preparation of the NCA cathodes, we coated the surfaces with a more straightforward drip coating. The Nafion-coated electrodes delivered a superior electrochemical performance with 100% of discharge capacity retention even after 100 cycles at 0.1C. The electrochemical impedance spectroscopy revealed that the Nafion coating could effectively prevent passive layer formation, which causes capacity fading.