Formation Of Solid Electrolyte Interface Layer Research Articles

Kinetic Monte Carlo Simulation of Surface Heterogeneity in Graphite Anodes for Lithium-Ion Batteries: Passive Layer Formation

The properties and chemical composition of the solid-electrolyte-interface (SEI) layer have been a subject of intense research due to their importance in the safety, capacity fade, and cycle life of Li-ion secondary batteries. In this paper, Kinetic Monte Carlo (KMC) simulation is applied to explore the formation of the passive SEI layer in the tangential direction of the lithium-ion intercalation in a graphite anode. The simulations are consistent with experimental observations that the active surface coverage decreases with time slowly in the initial stages of the battery operation, and then decreases rapidly. The effects of operating parameters such as the exchange current density, charging voltage, and temperature on the formation of the passive SEI layer are investigated. The active surface coverage at the end of each charging cycle remained constant for more cycles at higher temperature, but was lower at later cycles. The temperature that optimizes the active surface in a lithium-ion battery at cycle 1 can result in much lower active surface for most of the battery life. The potential for coupling the KMC model with porous electrode theory-continuum models is discussed to arrive at a multiscale model for understanding, analyzing, and minimizing capacity fade.

Access to M3 + / M2 + Redox Couples in Layered LiMS2 Sulfides ( M = Ti , V , Cr ) as Anodes for Li-Ion Battery

The insertion of Li into layered sulfides has been reinvestigated with ethylene-carbonate-based carbonate electrolytes. The and redox couples in a sulfide were found to give a reversible insertion reaction at about 0.5 and 1.0 V vs , respectively, while Cr atoms are displaced from at 0.9 V vs . Comparison to a graphite anode indicates that a solid-electrolyte-interface (SEI) passivation layer is formed below 0.9 V during the first discharge of the before reaching the redox couple, while an SEI layer was formed after reaching the redox couple at 1.0 V during the first discharge of the electrode. The formation of a suitable SEI layer and therefore the reversibility and capacity of sulfide anodes are shown to depend on the composition of the electrolyte.

Electrochemical absorption effect of BF 4 anion salt on SEI layer formation

The change of open circuit voltage (OCV) in aging process was surveyed to clarify the relations with the solid electrolyte interface (SEI) layer formation and with the Li ion battery performance. The compositions of absorbing materials were designed by organic compounds (EC, GBL, and FEC) and salts (LiPF 6 and LiBF 4). The OCV was affected by not only the organic compounds but also the salt contents. It was concluded that the absorbed BF 4 anion affected the SEI layer formation, and that the thermal stability was far superior to the other systems. This means that Li ion battery with thermal stability could be also fabricated by the control of the electrochemical absorption in the aging process.

리튬이온 전지의 초기 흡착 거동 해석

리튬이온 제조공정에서 전해질 주입 후 반드시 거쳐야 하는 숙성공정은 일반적으로 별로 중요하게 다루어 지지 않고 있다. 왜냐하면 전지 숙성공정이 전지성능에 영향을 주는 인자에 대하여 그다지 깊이 있게 연구가 되어있지 않기 때문이다. 하지만 숙성공정 중에 나타나는 OCV 변화는 전해질 내에 포함되어 있는 성분이 전극으로 전기화학적 흡착되어 나타나는 현상으로 SEI 피막 형성에 매우 중요한 역할을 하게 된다. 이에 본 연구에서는 숙성기간 중에 변하게 되는 OCV와 SEI피막의 관계, 그리고 전지성능과의 연계에 대하여 깊이 있게 논의하고자 한다. In the Li ion battery fabrication process, an aging step has treated as a miner step because there is not so much data to define the relationship between the phenomena generated in aging process and the battery performances. However, the OCV(open circuit voltage) change in the aging process is shown by the electrochemical absorption of the electrolyte component to the both electrodes(anode or cathode) and the absorbed layer to the electrode affects to form the solid electrolyte interface(SEI) layer during the first charge process. In this report, the adsorbed materials are designed deliberately and are cleared to affect to the SEI layer formation.

Enhanced High-Temperature Cycle Life of LiFePO[sub 4]-Based Li-Ion Batteries by Vinylene Carbonate as Electrolyte Additive

Addition of vinylene carbonate (VC) in electrolyte solution has been found to greatly improve the high-temperature (55°C) cycling performance of LiFePO 4 -based Li-ion batteries. It has been established that the VC additive remarkably suppresses Fe dissolution from LiFePO 4 cathode and hence, subsequent Fe deposition on the anode side. Furthermore, the VC additive also significantly reduces formation of solid-electrolyte interface layers on both LiFePO 4 cathodes and mesocarbon microbead (MCMB) anodes. With VC addition, a 18650-type LiFePO 4 /MCMB cell has been shown to retain ∼80% capacity after 980 cycles at 55°C under 1-3 C charge-discharge rates. This is in contrast with more than 25% capacity loss after merely 100 cycles when no VC is added.