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Effects of styrene-butadiene rubber/carboxymethylcellulose (SBR/CMC) and polyvinylidene difluoride (PVDF) binders on the electrochemical characteristics of a type of microsize MCMB (mesocarbon microbeads) anode (SMA) at low temperature are investigated by cold/heat shock testing, differential scanning calorimetry, scanning electron microscopy, electrochemical impedance spectroscopy, coin cell testing and 18650 full cell testing. Under low temperature conditions and compared to the SMA electrode with a SBR/CMC binder, the SMA electrode with a PVDF binder has lower impedance, lower charge transfer resistance, better rate capability and superior cycleability.Lithium ion batteries (LIBs) are at present dominating as power supplies in small sized general portable consumer electronics applications in the information technology (IT) industry. During recent decades, LIBs have undergone revolutionary technological progress in design and application. Development of LIBs for low temperature use has become an issue of great concern, especially for high power applications such as in aerospace, military and hybrid electric vehicles. 1-3 Lithium insertion and extraction in anode materials involve solid/electrolyte interface (SEI) formation, 4,5 although the twophase reaction theory has been challenged at low temperatures. In any case, it is widely observed that the insertion and extraction of lithium is more difficult at low temperatures. Great efforts have been made to enhance the lithium ion transport properties of SEI films on carbon anodes by approaching cell design from the related low temperature conditions. 6-8 Most previous researchers 9-13 have attempted to improve LIB low temperature performance by developing electrolytes with increased ionic conductivities. Among such studies, application of micro-sized materials and their shorter ionic diffusion paths to electrodes is considered one of the attractive solutions to the problem. However, recent work 14,15 has demonstrated that the primary cause of poor Li-ion cell performance at low temperatures is not related to organic electrolytes or SEI films but is in fact related to Li ion diffusion in negative electrodes with a polyvinylidene difluoride (PVDF) binder. The resistance to ionic flow at low temperatures is therefore a major factor in the performance of carbon-based negative electrodes in LIBs.Most polymers at room temperature show the familiar polymeric properties of material flexibility and high resistance to cracking. Typically, the long molecular chains of most polymers at moderate temperatures are able to stretch, deform and slither over one another. Accordingly, at normal temperatures, polymer materials are flexible, do not crack and are considered to be in a 'rubbery' state. But when the temperature drops through the 'glass transition region,' i.e. falls below the glass transition temperature (Tg), most polymers stiffen up and become glassy solids that are very hard and brittle. For the −40 • C to 80 • C operating temperature range of Li-ion batteries, low tem...

Mesophase soft carbon (MSC) and mesophase graphite (SMG), for use in comparative studies of high C-rate Lithium Ion Battery (LIB) anodes, were made by heating mesocarbon microbeads (MCMB) at 1300 °C and 3000 °C; respectively. The crystalline structures and morphologies of the MSC, SMG, and commercial hard carbon (HC) were investigated by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy. Additionally, their electrochemical properties, when used as anode materials in LIBs, were also investigated. The results show that MSC has a superior charging rate capability compared to SMG and HC. This is attributed to MSC having a more extensive interlayer spacing than SMG, and a greater number of favorably-oriented pathways when compared to HC.