Thermal stability carbon anodes

When conducting a differential scanning calorimetry (DSC) study on the stability of carbonaceous anodes in electrolytes, Tarascon and co-workers found that, before the major reaction between lithiated carbon and fluorinated polymers in the cell, there was a transition of smaller thermal effect at 120 °C, marked peak (a) in Figure 28. They ascribed this process to the decomposition of SEI into Li2C03, based on the previous understanding about the SEI chemical composition and the thermal stability of lithium alkyl carbonates.Interestingly, those authors noticed that the above transition would disappear if the carbonaceous anode was rinsed in DMC before DSC was performed, while the other major processes remained (Figure 28). Thus,... 

Cells can be overcharged when the cell voltage is incorrectly detected by the charging control system or when the charger breaks down. When this happens, the lithium ions remaining in the cathode are removed and more lithium ions are inserted into the anode than nnder standard charging conditions. If the lithium insertion ability of the carbon anode is small, lithium metal in the form of dendrites may be deposited on the carbon and this causes a drastic reduction in thermal stability. 

Ihara, M. Hang, B. Sato, K.. Egashira, M. Okada, S. Yamaki, J., Properties of carbon anodes and thermal stability in LiPF /Methyl difluoroacetate electrolyte, J. Electrochem. Soc., 2003, 750(11), A1476-A1483. 

Thermal stability of graphite and silicon/Li alloy ne tives, LiPFe/Alkyl carbonate mixed-solvent electrolytes, LiPFe/methyl difluoroacetate electrolyte, IiCo02 and FeFs positives with 1 M LiPFe/EC -I- DMC were investigated using DSC. Chained graphite and silicon/Li alloy showed almost the same heat output based on the amoimt of Li in each anode. LiPFe/methyl difluoroacetate electrolyte and FeFs showed a very small heat output. 

SEI formation-boosting additives. There has been a significant interest in the development of electrolyte additives to enhance the stabihty of LiPFe-based electrolytes for lithium-ion batteries [28]. One class of additives, which includes vinylene carbonate (VC) [29] and LiBOB [30, 31], react on the surface of the anode to generate a more stable SEI. Another class of additives includes N,N-dimethylacetamide (DMAc). DMAc reduces the reactivity of LiPFe and inhibits the reactions between the electrolyte and the electrode materials [32-34], Stabilizing the anode SEI and inhibiting the detrimental reactions of the electrolyte with the surface of the electrode materials will extend calendar life and enhance the thermal stability of lithium-ion batteries. 

Methods of fiiier pretreatment lignin treated by methylolation decreases the rate of cure of phenolic adhesives carbon fiber was anodically oxidized and subjected to various treatments with coupling agents to improve interfacial interaction with phenolic resins and oxidative stability of carbon fibers ti-tanate coupling of oxidized fibers resulted in improved adhesion to matrix and enhanced thermal stability of fibers ... 

Lee Y-S, Lee K-S, Sun Y-K, Lee YM, Kim D-W (2011) Effect of an organic additive on the cycling performance and thermal stability of lithium-ion cells assembled with carbon anode and LiNii/3Coi/3Mni/302 cathode. J Power Sources 196 6997-7001. doi 10.1016/j.jpowsour. 2010.10.047... 

Yamaki et aL DSC Cathode and electrolyte 1. The thermal stability of electrolytes with Lij Co02 cathode or lithiated carbon anode showed two exothermic peaks, one beginrting at 190 °C and the other beginning at 290 °C [28] n 1... 

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