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Cycling stability is a key challenge for application of silicon (Si)-based composite anodes as the severe volume fluctuation of Si readily leads to fast capacity fading. The binder is a crucial component of the composite electrodes. Although only occupying a small amount of the total composite mass, the binder has major impact on the long-term electrochemical performance of Si-based anodes. In recent years, water-based binders including styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) have attracted wide research interest as eco-friendly and low-cost alternatives for the conventional poly(vinylidene difluoride) (PVDF) binder in Si anodes. In this study, Si-based composite anodes are fabricated by simple solid mixing of the active materials with subsequent addition of SBR and CMC binders. This approach bypasses the use of toxic and expansive organic solvents. The factors of binder, silicon, and graphite materials have been systematically investigated. It is found that the retained capacities of the anodes are more than 440 mAh/g after 400 cycles. These results indicate that organic solvent free process is a facile strategy for producing high performance silicon/graphite composite anodes.

With an 11Ah LiMn2O4 battery as the object of study, through disassembling the battery after normal charge and normal discharge as well as over-charge and over-discharge, and using such methods as x-ray diffraction and scanning electron microscope, this study explores the micro-changes that happened to the material for the anode and cathode of this lithium battery after over-charge and over-discharge, and provides the measures to prevent batteries from charge and discharge, so as to avoid potential safety problems during the use of lithium batteries.

At a low temperature, due to its use of an organic electrolyte system, and its active substances having a poor electric conductivity as well, a lithium-ion battery will deliver a relatively poor performance at a low temperature, usually showing the symptoms of the common problem that individual batteries are consistent with each other better at a normal temperature, but showing a big difference in electric performance at a low temperature. Moreover, because of the effect of processing and fabricating techniques, the inconsistency among individual batteries in internal resistance also arises at a low temperature, which cannot be effectively detected at a normal temperature. Therefore, this article has studied the effect of low temperatures on battery recharge and discharge voltages. The results indicate that, with the decrease in temperature, batteries deliver a poor performance on discharge, the discharge curve shows an obviously downward trend, both average discharge voltage and discharge capacity fall somewhat, discharge capacity decreases remarkably, therefore the performance of batteries as a whole decreases faster, and batteries are noticeably less active.

Electrochemical impedance spectroscopy (EIS) is a viable approach that can be used in lithium ion batteries (LIBs) to investigate the electrochemical behavior. In this paper, Lithium Nickel Manganese Cobalt Oxide (NMC) type lithium ion batteries were divided into four groups. They were charged and discharged under various currents. The results showed that the higher the charging or discharging currents were, the faster the NMC batteries capacities fading were. In order to investigate the electrochemical behavior of the NMC batteries during cycling, we established an equivalent circuit model including one capacitor element in parallel with resistor and one constant phase angle element in parallel with resistor elements to study the impedance characteristics of the NMC batteries. The simulated results indicate that when the capacities of the batteries are dropping, the sum ohmic resistance of them will go up, and the resistance of Li+ diffusion through the SEI layer keeps increasing during cycling. The charge transfer resistance of the NMC batteries decreased at first and then kept increasing after 100 cycles. Among the three parameters, the charge transfer resistance values are the most sensitive factors that are corresponding to the state of charge of the NMC batteries during one single discharging process. We think that the internal ohmic resistance values can be used to predict the state of health (SOH) of the batteries and the charge transfer resistance can be used to predict the state of charge of the NMC batteries.

It is essential to know the behavior of the battery at all relevant internal and external conditions when the battery cell is in the new and the aging state. Electrochemical impedance spectroscopy (EIS) is a viable approach that can be used in lithium ion batteries (LIBs) to investigate the electrochemical behavior. In this paper, in order to investigate the state of charge effects on the LIBs, three types of commercial LIB cells were used, and the EIS measurements were performed under 100%, 80%, 50%, 20% and 0% SOC, respectively. An equivalent circuit model (ECM) including two constant phase angle elements in parallel with resistor elements is established to study the impedance characteristics for LIBs. The influence of the state of charge on the parameters of the ECM was analyzed. Based on the results we think EIS combined with ECM simulation tool can be used to derive useful information for improving battery design and state of health prediction.

This paper mainly studies the impact of temperature on the consistency of Lithium ion batteries. 4 cells of better capacity and internal resistance consistency, and inconsistent initial open-circuit potential are selected, respectively, to form 2 cell blocks connected in series, respectively, charged and discharged and monitored the real-time voltage and temperature at 20°C/20°C/40°C/65°C. The results show that when the high temperature was proper, the battery activity is increased, the energy is brought into more effective play, but the service life of the battery operating under high temperature environment for a long time, will be significantly reduced. While in the low-temperature environment, the overall performance of the battery pack is relatively decayed faster and battery inconsistency is increased.

This paper mainly studies the impact of internal resistance on the consistency of Lithium-ion batteries. The results shown that the inconsistent internal resistance of the cells forming the series-connected battery pack will reduce the performance of battery pack, and the higher initial internal resistance difference, the worse the consistency of cells of the series-connected battery pack.

The consistency tests of power Li-ion batteries which were good capacity, internal resistance consistency, and initial open-circuited potential were researched. The results showed that the monomer capacity consistency has a more significant impact on the capacity of series-connected battery pack, the capacity of battery pack is equal to the minimum capacity of single series of batteries — short board effect, the monomer battery capacity declines, causing the capacity of whole battery pack decrease proportionally. The voltage dispersion in later charging and discharging stage also increases with the capacity difference. And according to the analysis of the difference in voltage among 4 discharged batteries, at a normal temperature, the consistency among the batteries goes down at the end of the discharge process, while with the decrease in temperature, the consistency among the batteries goes down throughout the discharge process.

Cycling reliability is crucial for Si-based materials due to severe volume change during cycles that results in the fast capacity fading. Though the binder only occupies a very low amount of the total mass of anodes, it is proved to perform a key parameter to improve the cycle performance of Si-based anodes. Because they are eco-friendly and cost saving, water-based binders styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) are regarded as the better binder to substitute Poly (vinylidene difluoride) (PVDF) as the binder for Si-based anode. In this study, the anodes are fabricated by simply mixing the active materials (naso Si, graphite and conductive additive) together and using the mixture of SBR and CMC as a binder. The results showed that the retention capacities of the anodes are more than 440 mAh/g after 400 cycles. It indicates that it is an easy and simple way to make high performance anodes.

The crushing tests are generally performed at room temperature based on actual standards, but in fact, the power battery work in variety of different environment temperatures. Therefore, the crushing tests of the power battery were researched at different environment temperatures (-30℃, 20℃, 40℃ and 65℃). The results showed that the crush can induce the internal short circuit, thermal runaway and even fire and explosion. The other result is that the higher the environment temperature is, the worse the battery thermal stability is. That is to say, the battery is prone to induce thermal runaway when the temperature is high.