Today’s electric vehicles are almost exclusively powered by lithium-ion batteries, but there is a long way to go before electric vehicles become dominant in the global automotive market. In addition to policy support, widespread deployment of electric vehicles requires high-performance and low-cost energy storage technologies, including not only batteries but also alternative electrochemical devices. Here, we provide a comprehensive evaluation of various batteries and hydrogen fuel cells that have the greatest potential to succeed in commercial applications. Three sectors that are not well served by current lithium-ion-powered electric vehicles, namely the long-range, low-cost and high-utilization transportation markets, are discussed. The technological properties that must be improved to fully enable these electric vehicle markets include specific energy, cost, safety and power grid compatibility. Six energy storage and conversion technologies that possess varying combinations of these improved characteristics are compared and separately evaluated for each market. The remainder of the Review briefly discusses the technological status of these clean energy technologies, emphasizing barriers that must be overcome.
Fig 1:Evolution of cumulative EV sales and EV market share prescribed
in the IEA’s ‘Beyond 2 Degrees Scenario’. Cumulative EV sales up to 20162
are shown in the inset. Battery, plug-in hybrid and hydrogen fuel-cell EVs
are all included in these data. The scenario data are from ref


Although first introduced as early as the 1800s1, electric vehicles (EVs) have  only begun to be widely adopted since  the start of the present decade.  Global EV  sales have escalated from less than 10,000 in 2010 to 774,000 in 2016, surpassing 2 million  cumulative sales2.  Vehicle  electrification  is  now seen  as  the main decarbonization pathway for nearly all road-based transportation. Worsening urban air quality has also led  several countries to announce intentions to ban sales of internal combustion engine vehicles (ICEVs)4, which will need to be replaced by EVs. The growing success of EVs can be attributed, from a technological perspective, to advances in electrochemical energy storage technology. The specific energy of lithium-ion (Li-ion) batteries, which increased from approximately 90 Wh kg–1cell in the 1990s to over 250 Wh kg–1cell today5,6, has  allowed full-size automobiles to  travel sufficient distances for typical driving patterns7. Meanwhile, the cost of Li-ion battery packs has decreased from over 1,000 US$ kWh–1 to about 250 US$ kWh–1 (refs 5,8–11), allowing EV prices to fall to a price that early adopters are willing to pay. Figure  1 shows the  evolution of cumulative  EV sales  and EV market share that is needed to conform to the International Energy Agency (IEA)’s scenario3 for limiting global temperature increase to 1.75 °C. Referred to as the Beyond 2 Degrees Scenario (B2DS), this pathway calls for cumulative EV sales of 1.8 billion and an EV market share of 86% by 2060. The inset within Fig. 1, displaying cumulative vehicle sales of about 2 million and a market share of 0.2% in 2016, demonstrates the extremely early stage of current global EV adoption and  the large amount of future adoption that is needed. EV adoption has so far been heavily dictated by government policy instruments, such as  financial incentives, sales mandates and free vehicle charging12,13. Although these policies are likely to spur further adoption, it could become financially unsustainable or undesirable to scale them up to the level needed to reach the market share prescribed in Fig. 1. Moreover, it is not certain that EVs powered by Li-ion batteries will be suitable for every vehicle market, owing to inherent limits in their energy  storage capacity, safety and achievable cost. Alternative technologies that can power EV drivetrains are therefore an important focus. Here, we evaluate the potential  of  batteries and hydrogen fuel cells for improving the performance and reducing the cost of EVs. We first outline three automotive markets that have not seen much penetration  by  Li-ion  powered  EVs,  and  we  discuss  the  energy
characteristics  that  require  improvement  for  EVs  to  succeed  in these markets. Then, we compare and evaluate the properties of five battery types that are commonly discussed as candidates to power new EVs. Finally, we provide a  brief status review of each battery, in addition to hydrogen fuel cells, and discuss the potential of each technology in fulfilling requirements for emerging EV markets.
 
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