| 英文摘要: | To properly evaluate the prospects for commercially competitive battery electric vehicles (BEV) one must have accurate information on current and predicted cost of battery packs. The literature reveals that costs are coming down, but with large uncertainties on past, current and future costs of the dominating Li-ion technology1, 2, 3. This paper presents an original systematic review, analysing over 80 different estimates reported 2007–2014 to systematically trace the costs of Li-ion battery packs for BEV manufacturers. We show that industry-wide cost estimates declined by approximately 14% annually between 2007 and 2014, from above US$1,000 per kWh to around US$410 per kWh, and that the cost of battery packs used by market-leading BEV manufacturers are even lower, at US$300 per kWh, and has declined by 8% annually. Learning rate, the cost reduction following a cumulative doubling of production, is found to be between 6 and 9%, in line with earlier studies on vehicle battery technology2. We reveal that the costs of Li-ion battery packs continue to decline and that the costs among market leaders are much lower than previously reported. This has significant implications for the assumptions used when modelling future energy and transport systems and permits an optimistic outlook for BEVs contributing to low-carbon transport. The single most important factor in achieving a compelling and affordable mass-market BEV is its relative cost4. The key difference in design and cost between BEVs and internal combustion vehicles is the power train—in particular, the battery. It is commonly understood that the cost of battery packs needs to fall to below US$150 per kWh in order for BEVs to become cost-competitive on par with internal combustion vehicles5. This paper presents a first-of-its-kind systematic review of the cost of battery packs (in contrast to the cost of constituent cell) to BEV manufacturers of the at present dominating Li-ion technology. Recent noteworthy papers put such costs per kWh in the range €500–1,200 (US$636–1,529; ref. 1) and US$800–US$1,200 (ref. 2) in the 2010–2011 time frame, but these figures stem from only a limited set of data sources. There are also clear signs that costs of batteries are declining: estimates have been published putting costs as high as US$1,000 per kWh in 2012 (ref. 4), citing data from 2008 from the International Energy Agency (IEA; ref. 6) and 2007 from the World Energy Council (WEC; ref. 7). Comparisons between internal combustion and battery electric cars in 2009–2010 found battery costs to be €600(US$764) per kWh (ref. 8) and, most recently, van Noorden reported US$500 per kWh in 2014 in a recent paper9. Other recent research10, as well as major revisions of estimates from key actors studying the industry11, 12, also suggest that costs are declining fast. However, there have been no peer-reviewed studies that systematically review battery pack costs since the introduction of the new generation of BEVs in 2008 (ref. 10). We review cost estimates of battery packs for BEV application only (high capacity), excluding hybrid vehicle application (high power) as these are typically 30–50% more costly and not used in BEV (ref. 3). We include cost estimates of all variants of Li-ion technology used for BEV, as the aim is to track the progress of BEV technology in general and data is too scarce for individual Li-ion cell chemistry variants. Cost estimates (N = 85) included are from peer reviewed papers in international scientific journals; the most cited grey literature, including estimates by agencies, consultancy and industry analysts; news items of individual accounts from industry representatives and experts; and, finally, some further novel estimates for leading BEV manufacturers (see Supplementary Sheet 1). Results are based on N = 53 unique estimates (see Methods) and show that average cost, given as μ ± 2σ, for the industry as a whole declined by 14 ± 6% (N = 53, R2 = 0.28, p = 5.1 × 10−5) annually from 2007 to 2014 (Fig. 1, blue squares and crosses), and costs for market-leading manufacturers declined by 8 ± 8% (N = 15, R2 = 0.23, p = 0.07) annually for the same period (Fig. 1, green circles), leading to an estimated current cost range in 2014, given as given as the mean (95% confidence interval for the log model are shown in parentheses), of US$410(250–670) per kWh and US$300(140–620) per kWh respectively. This is of the order of two to four times lower than many recent peer-reviewed papers have suggested. Linear models give similar R2 values, but an exponential relationship is to be expected1. The rates for market leaders is on par with the 6–9% reported by Weiss et al.1, citing industry analysts11, 13, and 5–8% given by representatives from the industry14. We estimate that cumulative battery capacity has grown by more than 100% annually since 2011 (see Supplementary Sheet 3). However, the cost data has too much uncertainty to be used directly together with data on cumulative capacity to estimate learning rates, but using modelled average costs gives a learning rate of 9% (R2 = 0.99, p = 0.006) for the industry as a whole and 6% (R2 = 0.99, p = 0.004) for market-leading actors (Fig. 2). Finally, results show that costs in 2014 were probably already below average projected costs for the 2020 time frame (Fig. 1, yellow triangles).
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