In order to maintain the required high charge-discharge rate, negative electrodes in lithium ion second batteries for use by vehicles and industrial equipment as well as electric power distribution infrastructure need high output properties. Soft carbons of high quality are capable of achieving these output characteristics. The production of these carbon materials is energy intensive.
It takes, for instance, 1865kWh/t-1 of electricity to roast the petroleum coke using a traditional graphitization method. Heat is generated by the burning of natural gas and electric power to heat and cool raw materials repeatedly. The process is responsible for a large portion of energy consumption by the battery industry.
A solution is to use calcined petroleum coke (CPC). The calcination process transforms GPC into a form that is electrically conductive and has an acceptably low reactivity to oxygen and carbon dioxide. This material is very dense. CPC can be used for anodes in battery manufacture. It is important that anodes be dense enough to survive the chemical and physical degradation of smelters.
The production of CPC with high quality is a complicated process that requires many steps. Therefore, selecting the correct raw petroleum coal for the processing is crucial. The quality of CPC is dependent on sulfur content, among other things. Selection of best raw material has a major impact on the battery's performance and cost.
It is important to know how much heat has been applied in order to determine the CPC’s quality. In large rotary ovens, up to 85m in length and width with a height of 1.4-3.4m can be used for the calcination. Temperatures in the 1200degC range to 1350degC are used for calcination.
The calcination should also not create any nitrogen compounds. These compounds can lead to short circuits within the battery. In a battery, these short circuits are referred to as "spikes" and are the cause of the "burnt smell" that occurs when a battery is overcharged or discharged. It is important to have low levels of nitrogen in the batteries. The CPC performs better in batteries with lower nitrogen levels.
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