Requirement, Design, and Challenges in Inorganic Solid State Batteries Venkat Anandan Energy Storage Research Department 1
Ford s Electrified Vehicle Line-up HEV Hybrid Electric Vehicle C-Max Hybrid Fusion Hybrid Lincoln MKZ Hybrid PHEV Plug-in Hybrid Electric Vehicle C-Max Energy Fusion Energy BEV Battery Electric Vehicle Focus Electric 2
Motivation Environment Government Regulations 54.5 mpg 163 gco 2 /mile 250 gco 2 /mile Energy Independence ACCESS Number 41, Fall 2012 Double the mpg/half the emission! Reduce Dependence on Foreign Oil 3
US Electrified Vehicle Outlook EV growth, 2010-2015 http://www.iea.org/media/topics/transport/globalevoutlook2016flyer.pdf EV future outlook http://www.iea.org/media/topics/transport/globalevoutlook2016flyer.pdf 4
Why Li-ion? Higher specific capacity and power density Higher operating voltage Higher energy efficiency No memory effect means simpler controls OCV can be used to monitor SOC Saharan, V. and Nakai, K.SAE Technical Paper -01-1200,, Li-ion far exceeds the energy and power capability of Pb-acid, Ni- Cd and Ni-MH 5
Vol. energy density (Wh/l) Limitations in SOA Li-ion Batteries for EV Applications 1000 800 Energy Density Limitation Beyond Li-ion? Safety Burned Li-ion in Boeing 787 600 400 ~350 Wh/L Supplier Projection 600 Wh/L Samsung Galaxy Note 7 200 ~275 Wh/L Conventional Li-ion 2015 2020 2025 High Packaging Cost Need a Battery technology better than conventional Li-ion battery technology 6
Beyond Conventional Lithium-ion Wh/Kg 800 600 400 200 200 400 600 800 1000 Wh/l solid state batteries could deliver high volumetric energy density than other technologies 7
Advanced High Energy Lithium Battery Technologies Cell Type Potential Advantages Key Challenges Li-Air Li-S Low cost, weight cathode (oxygen) High theoretical specific energy Similar to fuel cell technology Low cost cathode High theoretical capacity Sealed cell design Low practical energy density(~550 Wh/l). Low demonstrated current density and cycle life Complex systems requirements - on board air scrubbing or closed O 2 cycling. Safety issues Self discharge and short cycle life Low voltage (high cell count) Safety issues solid state No flammable electrolytes Compatible with existing cathode materials Wide temperature and voltage operating window Low demonstrated current density and cycle life Scalability uncertain Materials compatibility issues Key Takeaways: All the above technologies has to use Li metal as anode to provide high energy density Li-air and Li-S will still have safety concerns due to the presence of liquid electrolyte Solid state batteries offer better safety and vol energy density than other technologies None of the technologies are ready at present for EV applications 8
Types of Solid State battery Thin film Battery Commercially available for applications including sensors, RFID tag, medical devices, and smarter cards. Excellent cycle life (many thousands) Very low capacity (~µah/cm 2 ), low current density (~ µa/cm 2 ) Expensive manufacturing process includes vacuum deposition tools such as sputtering, CVD, PVD. Not Suitable for EV applications Thin film Battery Design EFL700A39 EnFilm from STMicroelectronics 3.9V, 700 µah 9
Types of Solid State battery Bulk Type Solid State Battery 94 µm 20 µm 230 Wh/kg, 630 Wh/L (Cell Level) 1 Graphite Anode Separator 40 µm 50 µm 230 Wh/kg, 866 Wh/L (Cell Level) 2 Lithium Anode 75 µm Liquid Electrolyte 75 µm Solid Electrolyte NMC Cathode NMC Cathode Conventional Li-ion Solid State battery Benefits High energy density: Enables lithium metal and high voltage cathodes Better safety: Eliminates flammable liquid electrolyte and may prevent dendrite formation Thermal Stability: Stable at high temperature operations Reduce cost: Reduction in cost and complexity may be possible at the pack level 1 Assumed 20um separator, 85 um cathode thickness, 4.0 mah/cm 2 capacity loading 2 Assumed 50um Solid electrolyte separator, 75 um composite cathode thickness, 4.0 mah/cm 2 capacity loading 10
Performance to Target Vol. Energy Density (Wh/L) Sp. Energy Density (Wh/kg) Vol. Energy density Sp. Energy density) LCO LCO NCA NCA NMC NMC LMO LMO LFP LFP 1000 800 600 400 200 0 1 2Cathode 3 Materials4 5 Graphite/NMC Li-ion Cell SSB Design Lithium Anode Solid Electrolyte Cathode Active Material Assumed 50um Solid electrolyte separator, 75 um composite cathode thickness, 4.0 mah/cm 2 capacity loading, 2x lithium metal, cathode layer contain 70% active material, 5% carbon, and 25% solid electrolyte 250 200 150 100 50 Graphite/NMC Li-ion Cell A bulk type SSB design containing existing active materials can meet energy density target for automotive application 0 1 2Cathode 3 Materials4 5 11
Current Inorganic solid electrolytes Ionic conductivity >10-4 S/cm Manufacturability ( <40 µm sheets) Negligible electronic conductivity Relative Density Transference Number=1 Fracture Toughness Electrochemical window 0 to 6V Shear Modulus Chemical Stability with electrode Lithium lanthanum Zirconium Oxide (LLZO) meets most of the requirements! 12
Solid Electrolyte Film Processing Solid Electrolyte (LLZO) Sheet Tape Casting Process Conductivity~10-4 S/cm Density=89% 13
Li Metal/Solid Electrolyte (SE) Compatibility Potential (V) Li Metal LLZO (SE) Li Metal C Impedance of Li/SE/Li Li/SE Interface Modification Low Li/LLZO interface resistance ~44 Ω.cm 2 0.4 Cycling of Li/SE/Li Han et al. Nature Materials. 2016. With ALD-Al2O3 Coating interface resistance ~1 Ω.cm 2 and excellent cycling was demonstrated 0.3 E (Volts) 0.2 0.1 0-0.1-0.2 25µA/cm2 50µA/cm2 74µA/cm2 100µA/cm2 Shorting! 0 10000 20000 30000 (Sec) Time (s) Low Li/solid electrolyte interfacial resistance with excellent cycling could be obtained. Cycling performance at high current density need to be evaluated. Li_LLZO_Li_58b_Cycle_Run01_Un1Ch5_Step01.cor Li_LLZO_Li_58b_Cycle_Run01_Un1Ch5_Step02.cor Li_LLZO_Li_58b_Cycle_Run01_Un1Ch5_Step03.cor Li_LLZO_Li_58b_Cycle_Run01_Un1Ch5_Step04.cor Li_LLZO_Li_58b_Cycle_Run01_Un1Ch5_Step05.cor Li_LLZO_Li_58b_Cycle_Run01_Un1Ch5_Step06.cor Li_LLZO_Li_58b_Cycle_Run01_Un1Ch5_Step07.cor Li_LLZO_Li_58b_Cycle_Run01_Un1Ch5_Step08.cor Li_LLZO_Li_58b_Cycle_Run01_Un1Ch5_Step09.cor Li_LLZO_Li_58b_Cycle_Run01_Un1Ch5_Step10.cor Li_LLZO_Li_58b_Cycle_Run01_Un1Ch5_Step11.cor Li_LLZO_Li_58b_Cycle_Run01_Un1Ch5_Step12.cor Li_LLZO_Li_58b_Cycle_Run01_Un1Ch5_Step13.cor Li_LLZO_Li_58b_Cycle_Run01_Un1Ch5_Step14.cor 14
Compatibility with Cathode Materials Reactivity between LLZO (SE) and cathodes Y. Ren et al. / J Materiomics xx (2016) 1-9 LLZO/LCO Compatibility LLZO LLZO/LCO LLZO/LCO sintered at 900C for 5 h Observed color change after sintering >800 C 15
Electrode Design Lithium Anode Solid Electrolyte NMC Composite Cathode Electronic Conducting Material A thick (>50 µm) composite cathode structure is required. Composite cathode should contain active material, ionic and electronic conducting materials. All these materials should be mechanically, electrochemically, and chemically stable. Ionic Conducting Material NMC Active Material 16
Key Challenges in Solid State Battery technology Scalability High Rate SOA SSB Need large format SSB SOA SSB performs at ~1 ma/cm 2, while current Li-ion performs >10 ma/cm 2 Lithium Dendrite Durability Original Solid electrolyte Pellet Cross section of Pellet after short circuited Li dendrite Cycle life of SOA SSB is only about 100, while the current automotive Liion battery has a cycle life of more than 1000 Electrochemistry Communications 57 (2015) 27 30 Electrochemistry Communications 57 (2015) 27 30 17
Summary Conventional Li-ion battery technologies could deliver energy density ~750 Wh/l through engineering optimization, so next generation technologies should target beyond that. Solid state batteries has a potential to deliver more than 900 Wh/l with better safety than conventional Li-ion batteries. Current state of art of the solid state batteries are not yet ready to meet the various 2020 EV requirements. Both material and processing challenges has to be overcome to enable Solid State batteries for EV applications. 18
Collaborations 19
Thank you! 20