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Edinburgh | May-16 | OXIS Energy Ltd : Li-S Batteries for Energy Storage Applications


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Presenter : Dr David Ainsworth
Chief Technical Officer

Published in: Science
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Edinburgh | May-16 | OXIS Energy Ltd : Li-S Batteries for Energy Storage Applications

  1. 1. OXIS Energy Ltd Li-S Batteries for Energy Storage Applications Dr David Ainsworth, Chief Technical Officer Frontier Energy Storage Technologies and Global Energy Challenges 11th May 2016
  2. 2. OXIS Company Background  $70 million investment since 2005  Expanding rapidly:  3 fold increase in the number of employees since 2012 => 59 today  Highly trained staff (14 PhDs, 13 MSc/MA)  Cutting edge development facilities => second largest high specification dry room in Europe  Strong patent portfolio protecting IP => 79 patents granted, 81 pending, encompassing 25 families)  OXIS have been working on Li-S since 2005 at Culham Science Centre (Oxfordshire, UK)
  3. 3.  High Gravimetric Energy • Theoretical 2500 Wh kg-1 • >400 Wh kg-1 achievable in the future  Low Predicted Costs  High Safety • Short Circuit Test • Nail Penetration Test • Overcharge • Thermal Stability  Producing Li-S battery cells at pilot scale  Internally at OXIS and at manufacturing partners OXIS Li-S Pouch Cell Technology Variety of different sizes and capacities 2.0 – 3.4 Ah 6 Ah – 10 Ah > 20 Ah 10Ah Li-S pouch cells 3 KWh Li-S Rack Mounted Battery System
  4. 4. Introduction  Overview of Li-S cell technology  Key considerations for energy storage applications  OXIS materials research activities  OXIS activities relating to energy storage  Concluding remarks
  5. 5. Overview of Li-S Technology
  6. 6. Company Confidential Li-S Batteries: Principles Li Currentcollector Currentcollector Li+ Li+ Li+ Li+ Li+ Li+ (-) (+) Separator +- Discharge Load / Charger S8 (-) : 16 Li° → 16 Li+ + 16 e- (+) : S8 + 16 e- → 8 S2- 16 Li° + S8 → 8 Li2S Elemental sulfur Conductive carbon Binder  Average voltage: 2.1 V (vs. 3.7 V of Li-ion)  Sulfur electrode specific capacity: 1675 mAh g-1 (vs. 170 mAh g-1 of LiFePO4)  Complex working mechanism: with intermediate species (soluble Li2Sx)  Theoretical gravimetric and volumetric energy: 2500 Wh kg-1 and 2800 Wh L-1, respectively
  7. 7. OXIS Key Technical Competences R&D Pilot Production Battery Systems Materials Research Li-S Cell and Components Battery Design and Testing
  8. 8. History of OXIS Li-S Cell Development Q2 2015: 10Ah Cell Energy Storage/LEV’s 160Wh/kg 2010: 500 mAh pouch cell < 100 Wh/kg Q4 2014:39Ah automotive cell 220 Wh/kg 2011-2013: 1.7-3.4Ah pouch cells 170 Wh/Kg Q1 2015: Ultra light for UAV market 35 Ah ; 300 Wh/kg ULTRALIGHTLONGLIFE Q3 2014: 25Ah automotive cells 200 Wh/Kg Q4 2014: Ultra light for UAV market 6.5 Ah ; 265 Wh/kg 2013-2014: R&D prototype 2 Ah ; 220-240 Wh/kg Q2 2015: Ultra light for UAV market 21 Ah ; 325 Wh/kg Company Confidential
  9. 9. Improvements to Li-S Technology  OXIS is researching the following areas to improve cell performances  Sulfur/Carbons/Binders  Current collectors  Separators  Lithium & protection mechanisms  Electrolytes Current Collector Sulfur/Carbon/Binder Electrolyte Separator Lithium Current Collector Cathode Anode SeparatorSulfur/Carbon/Binder Ni Tab Al Tab Cathode Anode Separator Pouch  20 R&D scientists (11 PhD’s)  20 production staff  Aiming to achieve 500Wh/Kg by 2020
  10. 10. Li-S Cells for Energy Storage  Over 1400 cycles demonstrated on OXIS Long-Life Li-S cells
  11. 11. Key Considerations of Energy Storage
  12. 12. Considerations for Li-S Batteries in Energy Storage  Cost per KWh => > $200/KWh at over 3M units production  Cycle Life => 1400 cycles today, targeting 2000 cycles  Recyclability => No heavy/transition metals, lithium probable only material of value  Price per kWh of energy storage is key! => Strongly dependant of deployed location
  13. 13. Considerations for Li-S Batteries in Energy Storage Other, 5% Separator, 5% Lithium, 15% Cathode, 25% Electrolyte 50% A typical distribution of masses in an Li-S cell  Electrolyte can represent up to 50% of the weight of a cell!  Electrolyte and Lithium are most expensive cell components Sulfur can only represent up to 15% of the mass of the cell
  14. 14. Materials Research Activities
  15. 15. Optimisation of Li-S cells from Materials Research Cathode: New S/C composites • Increase S8 loading • Increase S8 utilisation • Improve power capability Electrolyte: Development of new additives and solvents • Maintain Safety • Increase S8 utilisation • Stability vs Anode Anode: New anode coating • Enhance cycle life • High resistance to corrosion • Reduce electrolyte degradation • Increase volumetric energy
  16. 16. Anodes for Li-S Batteries: Cycle Life Coated Lithium Anode Solution => Deposit thin protective coating onto anode surface Required Properties:  Good adhesion to lithium metal  High sheer modulus  High ionic conductivity  Chemical resistance
  17. 17. Development of Protected Lithium Metal Anodes Unprotected Lithium: 50 cycles Protected Lithium: 50 cycles Very aggressive conditions High surface area lithium Integrity of foil is preserved
  18. 18. Cathode Development: Energy Density and Cost TEM image of Sulfur/CNT composite material Issues:  Both Sulfur and Lithium are insulating  Low surface capacity for good utilization  Access/Wettability of active material  Power  Migration of Polysulfides Solutions:  Form 3D conductive network form S/CNT composite  Functionalization of binder/carbon materials?  Control process parameters to tailor cathode porosity/ morphology
  19. 19. Energy Storage Activities at OXIS Energy
  20. 20. OXIS Li-S Battery Evolution Bike Battery V2 using 3.4 Ah cells 2013 Rack Mount Battery using 10 Ah cells 2016 Control Board Very simple safety circuitry Components = 58 Bike Battery V1 using 1.7 Ah cells 2012 Stackable Battery using 3.4 Ah cells 2015 Navya using 3.4 Ah cells 2014 LINCAD BMS Adapted from LIPS10 RDVS BMS Cell Control Board Balancing and Safety per cell Components = 101 Control Board Prototype only Enhanced safety Communications Components = 261 Control Board with integrated cell monitoring Production Safety + reliability (fault diagnostics) Components = 897 Cell Wiring Board Production orientated connectivity. Board per module Charger Board For direct PV connection LIPS 10 Battery Development for MoD
  21. 21. Li-S Batteries for Stationary Energy Storage 3KWh Rack Mounted Battery 48KWh Battery System 1MWh Containerised Battery System
  22. 22. 3 kWh Rack Mounted Battery • Prototype 1 of 3KWh Rack Mounted Battery manufactured in Q1 2016 – Prototype battery completed and initial tests successful N.B. Flying leads are deliberate to allow testing of the prototype
  23. 23. 3 kWh Rack Mount Battery Specification Dimensions (h x w x d) 130 x 482 x 650 mm Weight 25 kg Cell type OXIS POA0122 10Ah Long-Life Lithium-Sulfur cells Number of cells 144 Environmental protection IP 20 Storage temperature -27 to + 30 °C Operating temperature 0 to 60 °C Nominal voltage 50 V Minimum voltage 38 V Maximum voltage 56.4 V Rated stored energy 3 kWh Charge 0.1C, discharge 0.2C Usable stored energy 2.5 kWh Charge 0.1C, discharge 0.2C Rated capacity 60 Ah Charge 0.1C, discharge 0.2C Operating Depth of Discharge (DoD) 80 % Maximum continuous discharge current 60 A Peak discharge current (30 secs max) 180 A Maximum charging current 15 A Recommended charging current 6 A Equivalent series resistance < 100 mΩ Isolation to chassis 1 kV Cycle life 1400 cycles Charge 0.1C, discharge 0.2C, 80% DoD. Battery equivalent series resistance < 100 mΩ Features: • Cell balancing • Cell safety monitoring circuits with redundancy • Electronic short circuit protection (LV only) • High voltage interlock/ trip (HV only) • Chassis isolation monitor • Isolated user CAN bus interface • Isolated user RS485 bus interface • Ethernet port • Internal history and fault logging
  24. 24. Master Controller Battery System Architecture System Integrator responsibility OXIS custom design and manufacture OXIS standard design, 3rd party manufacture Key RMB RMB RMB RMB RMB RMB RMB RMB SC Rack 1 RMB RMB RMB RMB RMB RMB RMB RMB SC Container RMB RMB RMB RMB RMB RMB RMB RMB SC Rack 21 RMB RMB RMB RMB RMB RMB RMB RMB SC RMB RMB RMB RMB RMB RMB RMB RMB SC Rack 2 RMB RMB RMB RMB RMB RMB RMB RMB SC Inverter and grid connection RMB Rack Mount Battery SC String Controller
  25. 25. Conclusions  Li-S Cells need to be low cost and long cycle life for Energy Storage  Costs of <$200/kWh are already possible at mass manufacturing scale  Cathode/Electrolyte Interface for reduced cost plus lithium protection for extended cycle life  Prototype Li-S battery systems for stationary energy storage are being tested by OXIS
  26. 26. OXIS R&D Development Partners Joint Development Agreements Development Programmes Partnerships
  27. 27. Mark Wild Geraint Minton Laura O’Neill Rajlakshmi Purkayastha Steffen Schlueter Sylwia Walus David Ainsworth Agata Swiatek Ashley Cooke Jacob Locke Justyna Kreis Lisset Urrutia Lukasz Kabacik Martin Clegg Lukasz Solek Maciej Szczygielski Sebastien Desilani Sebastien Liatard Stephen Lawes Steve Rowlands Acknowledgements