To develop nonflammable electrolytes for lithium-ion batteries, the fundamental properties of trimethyl phosphate (TMP)-based electrolytes with LiPF6 as solute were investigated for natural graphite anode and LiCoO2 cathodes. It was found that the TMP solvent had good oxidation stability and poor reduction stability, which led to TMP reduction decomposition on the natural graphite electrode at the negative potential of 1.2 V. To solve this problem, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) cosolvents were mixed with TMP solvent. As a result, the reduction decomposition of the TMP solvent was considerably suppressed in <10% TMP containing EC+PC+TMP and <25% TMP containing EC+DEC+TMP electrolytes due to the formation of good solid electrolyte interphase film on natural graphite electrode in these two mixed electrolytes. The nonflammability of the TMP electrolyte declined with mixing flammable cosolvents, which was explained by a flame retarding mechanism involving a hydrogen radical trap in the gas phase. According to this mechanism, it was deduced that the cosolvents with high boiling point and fewer hydrogen atoms were promising for nonflammability of mixed electrolytes. Furthermore, a thermal test disclosed that the thermal stability of lithium-ion cells may be improved by using TMP-containing electrolytes. © 2001 The Electrochemical Society. All rights reserved.

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In order to improve the cycling performance of lithium-ion batteries with nonflammable trimethyl phosphate ͑TMP͒-based electrolytes, amorphous carbon ͑AC͒ was used as the anode material. It was found that the reduction decomposition of TMP solvent, which occurred without limit on a natural graphite anode and concomitantly generated a large amount of methane (CH 4 ) and ethylene (C 2 H 4 ) gases, was considerably suppressed on amorphous carbon anode. This improvement was attributed to the disordered structure of amorphous carbon, which hindered the cointercalation of TMP solvent. The charge/discharge result and cyclic voltammetry further disclosed that a highly stable and passivating surface film, called the solid electrolyte interphase film, was formed on the AC surface at the potential near 1 V. As a result, an AC/LiCoO 2 ion cell with 1 mol/dm 3 LiPF 6 /ethylene carbonate ͑EC͒ ϩ propylene carbonate ͑PC͒ ϩ diethylcarbonate ͑DEC͒ ϩ TMP ͑30:30:20:20͒ nonflammable electrolyte exhibited promising cycling performance. Furthermore, this electrolyte was also found to have good low-temperature performance with the freezing point of ϽϪ40°C. Thermal test results disclosed that a lithium-ion cell with 1 mol/dm 3 LiPF 6 /EC ϩ PC ϩ DEC ϩ TMP ͑30:30:20:20͒ exhibited good thermal stability.

Though much effort has been paid for lithium metal rechargeable batteries with lithium metal as anode in the past decades, 1-6 its commercial application is not yet realized. This has been attributed to the interface reaction of freshly deposited lithium with inorganic and organic species in the electrolytes, which results in low lithium cycling efficiency, deleterious dendritic morphology of deposited lithium surface, and safety concern. Therefore, finding electrolytes with low reactivity with lithium metal is an important issue in the effort to realize the commercial application of lithium metal rechargeable batteries.So far, tetrahydrofuran (THF) and its alkyl derivative electrolytes with LiAsF 6 or LiClO 4 as solute was explored mainly to suppress the reaction of lithium anode with electrolytes. 11-17 1,3-Dioxolane (DOL) based electrolytes also received special attention due to high lithium cycling efficiency in this electrolyte. 18-21 Nevertheless, the poor anodic stability of THF-based solvents and DOL solvent led to the application of these electrolytes only in 3 V lithium metal rechargeable batteries. 11,13,14 The toxicity of LiAsF 6 and the safety problems of LiClO 4 also limited the practical application of these electrolytes.In recent work, we developed 1 mol/dm 3 LiN(SO 2 C 2 F 5 ) 2 /EC ϩ tetrahydropyran (THP) (5:5) electrolyte. [22][23][24][25][26] This electrolyte was found to have many advantages, such as a high lithium cycling efficiency of >99%, good oxidation stability, satisfactory boiling point, and promising thermal stability. The Li/LiMn 2 O 4 coin cell with this electrolyte also gave excellent cycling performance. Furthermore, scanning electron microscopy (SEM) observation showed that the deposited lithium in this electrolyte had fine particle morphology rather than dendritic morphology. Other groups have also studied the use of lithium imide salts for lithium rechargeable batteries. 27-30 Naoi et al. reported the good surface morphology of deposited lithium and high lithium cycling efficiency in LiN(SO 2 C 2 F 5 ) 2 electrolytes. 31 The main problems inherent in the practical application of 1 mol/dm 3 LiN(SO 2 C 2 F 5 ) 2 /EC ϩ THP (5:5) electrolyte are poor lowtemperature performance (freezing point: 8ЊC) and low boiling point of THP solvent. To solve this problem, we studied LiN(SO 2 C 2 F 5 ) 2 electrolytes with DOL, 1,3-dioxane (DOX), 1,3-dioxepane (DOXP) and their alkyl derivatives as solvents in this work. ExperimentalElectrolyte preparation.- Table I lists the examined solutes and five-, six-, and seven-membered cycloalkane solvents with two oxygen atoms. These solvents were generally used with a purity of >99% after being purified by distillation. Lithium bistrifluoromethylsulfonyl imide (LiN(SO 2 CF 3 ) 2 ) and LiN(SO 2 C 2 F 5 ) 2 solutes were dried at 130ЊC and under vacuum for 24 h, while LiPF 6 solute was used as received due to its high purity (battery grade). The preparation of electrolytes was performed in an argon glove box. The water content in the resultant electrolytes...

We report here that fullerenes (C60,C70,C84, etc.) can be fabricated in a 7% yield by carbon particle evaporation in a hybrid plasma which is characterized by the superposition of a rf plasma and a dc arc jet operated at atmospheric pressure. We found that increasing the pressure in the plasma gas increases the yield of fullerenes. We also investigated the effect of introducing the gas for quenching the plasma gas on the yield of fullerenes. Furthermore, this method has also been used to produce metal fulleride.