16 research outputs found
Nickel, Manganese, and Cobalt Dissolution from Ni-Rich NMC and Their Effects on NMC622-Graphite Cell
Electrochemical polarization-based fast charging of lithium-ion batteries in embedded systems
Thermal and electrical aging of laser braze-welded aluminum–copper interconnects
Aluminum–copper (Al–Cu) interconnects are of great interest for a variety of electrical applications, such as lithium-ion batteries. In this paper, the effects of thermal and electrical aging on the intermetallic compound growth of laser braze-welded Al–Cu interconnects are reported. Thermal aging was studied in a temperature range from 200 to 500 °C for durations between 1 and 120 h. Electrical aging was studied with 200 A direct current application with different polarities and durations between 1 and 24 h. The formation of intermetallic compounds was found to be dependent on the type of aging and, for electrical aging, on the polarity of the current. The growth of intermetallic compounds under the influence of the electric current was distinctly higher than for thermal annealing conditions. The formation of voids at the transition between intermetallic compounds indicates that electromigration may be the main driving force for the accelerated intermetallic growth
Nickel, Manganese, and Cobalt Dissolution from Ni-Rich NMC and Their Effects on NMC622-Graphite Cell
Transition metal dissolution from the cathode active material and its deposition on the anode causes significant cell aging, studied most intensively for manganese. Owing to their higher specific energy, the current focus is shifting towards nickel-rich layered LiNixMnyCozO2 (NMC, x + y + z = 1) with x > 0.5, so that the effect of Ni dissolution on cell degradation needs to be understood. This study investigates the dissolution of transition metals from a NMC622 cathode and their subsequent deposition on a graphite anode using operando X-ray absorption spectroscopy. We show that in NMC622-graphite cells transition metals dissolve nearly stoichiometrically at potentials > 4.6 V, highlighting the significance of investigating Ni dissolution/deposition. Using NMC622-graphite full-cells with electrolyte containing the bis(trifluoromethane) sulfonimide (TFSI) salts of either Ni, Mn, or Co, we compare the detrimental impact of these metals on cell performance. Using in-situ and ex-situ XRD, we show that the aging mechanism induced by all three metals is the loss of cycleable lithium in the solid electrolyte interface (SEI) of the graphite. This loss is larger in magnitude when Mn is present in the electrolyte compared to Ni and Co, which we ascribe to a higher activity of deposited Mn towards SEI decomposition in comparison to Ni and Co. (C) The Author(s) 2019. Published by ECS
Role of 1,3-Propane Sultone and Vinylene Carbonate in Solid Electrolyte Interface Formation and Gas Generation
Lithium-ion
coin cells containing electrolytes with and without
1,3-propane sultone (PS) and vinylene carbonate (VC) were prepared
and investigated. The electrochemical performance of the cells is
correlated with ex situ surface analysis of the electrodes conducted
by Fourier transform infrared and X-ray photoelectron spectroscopies
and in situ gas analysis by online electrochemical mass spectrometry
(OEMS). The results suggest that incorporation of both PS and VC results
in improved capacity retention upon cycling at 55 °C and lower
impedance. Ex situ surface analysis and OEMS confirm that incorporation
of PS and VC alter the reduction reactions on the anode inhibiting
ethylene generation and changing the structure of the solid electrolyte
interface. Incorporation of VC results in CO<sub>2</sub> evolution,
formation of polyÂ(VC), and inhibition of ethylene generation. Incorporation
of PS results in generation of lithium alkylsulfonate (RSO<sub>2</sub>Li) and inhibition of ethylene generation. The combination of PS
and VC reduces the ethylene gassing during formation by more than
60%