9.1: Prelude

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In many ways, current technology is limited by battery technology. For example, the battery of the Apple iPhone X weighs 42 g and has a specific energy of 246 $\frac{W \cdot h}{kg}$. It accounts for 24% of the weight of the phone [123] [124]. Similarly, the batteries of the Tesla Model S electric vehicle weigh 580 kg and have an overall specific energy of 141 $\frac{W \cdot h}{kg}$. They account for 27% of the weight of the car [125]. Relatedly, technology companies have been rocked by problems in battery manufacture. In July of 2015, more than half a million hoverboards produced by ten different companies were recalled due to battery explosions [126]. Also, Samsung recalled millions of Galaxy Note 7 smart phones in 2016, costing the company billions of dollars [127]. The batteries were manufactured by one of two different suppliers. Manufacturing issues in batteries produced by both suppliers made the phones susceptible to catching on fire [127].

Due to the importance of battery technology to the consumer product industry, electric vehicle industry, and other technology sectors, money and effort have been pouring into battery research, development, and manufacturing. Rechargeable lithium ion battery development, in particular, is an intense area of effort and investment. All of the examples in the previous paragraph involve these lithium batteries. In 2009, $13 billion worth of lithium batteries were sold, and 163 billion lithium batteries were produced [128, ch. 15]. In 2014 Tesla, one of multiple manufacturers, began construction of a new factory named the Gigafactory. Upon completion, Tesla aims for this facility to be the largest building in the world and for it to annually produce lithium batteries with a combined capacity of 35 gigawatt hours [129]. More recently, industry-wide investment has only grown larger.