Current Trends in Battery Technology ECV national seminar 24.9.2014 Samu Kukkonen VTT Technical Research Centre of Finland
Structure of the Presentation 1. Introduction, what was said in the previous ECV-seminar 2. Conventional technologies: Lead-Acid, NiMH, and Li-Ion 3. The future in brief 4. Exercise: specifying a battery for ebus 5. Summary 07/11/2014 2
Introduction - What was said in ECV-seminar on 9/2013 Storing electrical energy is difficult in technology and business wise Li-Ion remains the high capacity technology of the 2010s Next generation batteries not appearing until after 2020 Cost of batteries is still high but falling 300 /kwh in 2020 on a system level for PHEV/EV? The cost and performance of present batteries has reached a critical level for cost effective (hybrid) electric commercial vehicles but implementation requires careful engineering and solutions Applied battery R&D is the focus of ECV-eStorage3. Supporting the industry with experimental, modelling, and literature work. This is still true in 9/2014 but what about the cost estimate? 07/11/2014 3
The conventional technologies Lead-acid, NiMH, and Li-Ion 4
Trends in SLI Lead-Acid Batteries The increasing electrification in conventional passenger vehicles puts extraordinary demands for SLI batteries Electric power steering Electric AC Start/stop, power boost, recuperation capabilities, etc. Upcoming electric turbo chargers (Automated driving) According to the Volkswagen group, the dynamic upper limit for 12 V SLI battery current is 200 A 2009- Audi A8 the current demand is 180 A 2011- Audi A6 the current demand is 290 A! Two batteries required! Advancements in lead-acid technology have been made in e.g. power capability and deeper cycling ability. However, this might not be enough New interest for 48 V systems has arisen especially in premium German brands 07/11/2014 5
Trends in Automotive NiMH Batteries Nickel-metal hydride batteries have proven their safety, performance, and lifetime in mild- and full hybrid applications Advantages (when compared to Li-Ion) include simpler BMS, thermal management and better safety and calendar lifetime Disadvantages: Significantly lower energy content and cyclic lifetime Toyota Nickel as a material is expensive, large NiMH battery systems are expensive and will probably remain so NiMH is the intermediate battery technology Mild-hybrids Full-hybrids Next gen. 48 V systems? However, there are few interesting developments happening in NiMH technology, for example the Swedish Nilar stacked NiMH batteries Nilar 07/11/2014 6
Trends in Automotive Li-Ion Technology First the Basics Lithium-ion technology consists of several anode/cathode material options and additives which determine the characteristics of a Li-Ion battery In 2014, the primary material families are still Anode: graphite and LTO Cathode: NMC, NCA, LMO, and LCO In addition to materials, a cell construction can be optimized to emphasize certain characteristic like energy density Chevrolet Several new materials are under heavy research to increase energy content and lower the costs. 07/11/2014 7
Trends in Automotive Li-Ion Technology Li-Ion Chemistry Characteristics Graphite- NCA Graphite- NMC Graphite- LMO/Blend Graphite- LFP LTO-NMC Safety + ++ ++ +++ ++++ Energy ++++ +++ +++ ++ + Lifetime + +++ ++ +++ ++++ Charging +++ +++ +++ ++ ++++ Cost ++++ +++ +++ ++++ + Supply +++ +++ ++ ++++ ++ Tesla Model S Seems to be the best compromise German EVs. Varying lifetimes depending on blend. Japanese and USA EVs. Chinese are flooding the market. Disparities in quality. A real choice for ECVs. Expensive but very durable, and high power. A real choice for ECVs. 07/11/2014 8
Trends in Automotive Li-Ion Technology Li-Ion Suppliers and Applications Graphite- NCA Graphite- NMC Graphite- LMO/Blend Graphite- LFP LTO-NMC Suppliers Panasonic Samsung, Li- Tec AESC, LG Chem, Li Energy Japan A123, ATL, Calb, BYD, Lishen Tianjin, Saft Toshiba, Altairnano, Tiankang Applications Tesla Model S VW eup, egolf, BMW i3, Daimler Smart, Fiat 500 Nissan Leaf, Chevrolet Volt, Renault Zoe Chevrolet Spark EV, Coda EV, ebuses Mitsubishi i- MiEV, Honda Fit, ebuses 07/11/2014 9
Trends in Automotive Li-Ion Technology Li-Ion Suppliers in China 07/11/2014 10
Trends in Automotive Li-Ion Technology The Challenges Electric passenger cars have fundamental challenges Range Cost Lifetime and safety of the batteries However, Tesla Model S has proven that 500 km EV is possible with current technology Also, Tesla could bring battery prices significantly down Lets take a closer look 07/11/2014 11
Trends in Automotive Li-Ion Technology Case Tesla Model S and Nissan Leaf Tesla Model S Nissan Leaf Range 500 km (NEDC) 85 kwh Panasonic graphite- NCA battery Cell format is standard 18650 7104 cells total! Quite a feat to manage MTBF! Range 200 km (NEDC) 24 kwh AESC graphite- LMO/Blend battery Cell format is custom pouch 192 cells total 07/11/2014 12
Trends in Automotive Li-Ion Technology Case Tesla Model S and Nissan Leaf Tesla Model S Implications of using 18650 cells Nissan Leaf Implications of using custom pouch cells 18650 is mature technology Small cells, easier safety concept Large battery, less lifetime requirement 630 Wh/l, 233 Wh/kg cell level Cost estimate of cells: 184 $/kwh (2015) Source: AABC Manufacturing process is still evolving for pouches Large cells need to be safe Small battery, high lifetime requirement 309 Wh/l, 155 Wh/kg cell level Cost estimate of cells: 213 $/kwh (2015) Source: AABC 07/11/2014 13
Trends in Automotive Li-Ion Technology Tesla Gigafactory 07/11/2014 14
Near-future technologies (2015 2020) and beyond briefly 15
Near Future Technologies and Beyond - What is taking so long? Specific energy (Wh/kg) = Capacity Ah Voltage (V) Active Masses of Anode and Cathode (kg) Some fundamental challenges: Increasing voltage beyond 4,5 Volts causes present day electrolytes to decompose Increasing capacity and reducing mass requires new anode/cathode materials Finding new electrolytes has proven difficult Developing new stable materials that have the capacity but also safety, lifetime, power, efficiency, low cost, etc. is also difficult 07/11/2014 16
Near Future Technologies and Beyond What is under research and when are they available? 07/11/2014 17
Near Future Technologies and Beyond REDOX Flow Batteries In REDOX flow batteries the reactants are stored in tanks in liquid state The battery can be recharged or the contents in the tanks can be emptied and refilled (much like filling your car) The size of the tanks determines the energy The size of the battery stack determines the power Lifetime is very long Already in commercial operation as stationary grid energy storage Could this be scaled down to ECVs? New energy and fuel Enervault 1 MWh, 250 kw REDOX battery in California 07/11/2014 18
Exercise: Choosing and dimensioning a Li-Ion battery/chemistry for ebus
ebus Battery Exercise Requirement Specification Objective: Dimension a battery for opportunity charged ebus operating in HSL bus line 11 (in Espoo) and discuss about the cost and lifetime Assumptions Charger in Tapiola, Espoo is 250 kw, 8 minutes of charging after each roundtrip One roundtrip is 20 km in distance The ebus consumes 1 kwh/km during summer and 1,5 kwh/km during winter 07/11/2014 20
ebus Battery Exercise Dimensioning Worst case round-trip energy consumption: 1,5 kwh/km * 20 km = 30 kwh Available charging energy = 250 kw * 1 h * 8 min / 60 min = 33,3 kwh Usable energy needs to be 30,0 kwh (with safety margin!) with 250 kw charging acceptance Li-Ion LTO batteries are safe, accept the charging power, and have the lifetime Li-Ion LFP batteries are cheaper, safe enough, can accept the charging power when over-dimensioned, but is lifetime enough? The options in this exercise: Altairnano LTO: 2,26 Volts, 60 Ah, 360 A charging acceptance, 16 000 cycle lifetime (on paper) A123 LFP: 3,3 Volts, 19,5 Ah, 58,5 A charging acceptance, 3000 cycle lifetime (on paper) 07/11/2014 21
ebus Battery Exercise Dimensioning The requirements: 30 kwh each roundtrip, 250 kw charging Dimensioning: Altairnano 60 Ah LTO: 272s2p = 615 Volts, 73,8 kwh, 440 kw, and 1525 kg This leaves 43,8 kwh headroom for energy and 190 kw for charging. Total ebus range: 49 74 km. A123 19,5 Ah LFP: 186s9p = 614 Volts, 108 kwh, 325 kw, and 1661 kg This leaves 78 kwh headroom for energy and 75 kw for charging. Total ebus range: 72-108 km. The cost of the batteries is estimated to be equal Lifetime of the batteries determines the total-cost-of-ownership between the two options However, A123 gives added value with significantly larger 78 kwh headroom and thus range. 07/11/2014 22
ebus Battery Exercise Battery Lifetime Battery lifetime behaves non-linearly as a function of temperature, power, used SoC range and time. Could I calculate the following? Altairnano 16 000 full cycles: 16 000 * 49 74 km = 784 000 km 1 184 000 km A123 3000 full cycles: 3000 * 72 108 km = 216 000 km 324 000 km The calculation is not correct because lifetime is non-linear A123 has much more room for degradation than Altairnano. If safety can be confirmed, the battery can be used beyond common end-of-life condition of 80 % original capacity. Which one has the better TCO? Difficult to answer, assessing lifetime requires laboratory testing, field testing,or modelling approaches 07/11/2014 23
Summary 24
Summary There is limited improvement potential in Lead-Acid and NiMH The present day Li-Ion is the technology of the 2010s It is difficult to estimate when new technologies are commercially available Many ECVs are feasible with the current technology. But careful research and engineering is required. VTT is here for the industry. We aim to research and serve as the necessary knowledge center for batteries and ECV systems. 07/11/2014 25
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