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Fail safe design for large capacity lithium ion batteries
 

Fail safe design for large capacity lithium ion batteries

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    Fail safe design for large capacity lithium ion batteries  Fail safe design for large capacity lithium ion batteries Presentation Transcript

    • Source: A123 Source: GM Fail Safe Design for Large Capacity Lithium-ion Batteries NREL Commercialization & Tech Transfer Webinar March 27, 2011 Kandler Smith Gi-Heon Kim kandler.smith@nrel.gov gi-heon.kim@nrel.gov John Ireland, Kyu-Jin Lee, Ahmad PesaranNREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.
    • Challenges for Large LIB Systems•  Li-ion batteries are flammable, require expensive manufacturing to reduce defects•  Small-cell protection devices do not work for large systems•  Difficult to detect faults in large cells before catastrophe Outer temperature Short Inner temperature Short 4 blog.wellsfargo.com 3.9 3.8 Large cell Voltage [V] 3.7 3.6 Reference Small cell 3.5 1Ah 40Ah 3.4 0 50 100 150 200 250 300 engadget.com Time [sec] NATIONAL RENEWABLE ENERGY LABORATORY   2
    • Barriers for Safe Large LIB Systems 1)  Early Fault Detection •  The faults leading to a field accident are believed to grow from a latent defect over time •  Signals of an early-stage-fault are difficult to detect in large capacity LIB systems 2)  Electrical Isolation of Fault •  To limit further electric current feed energizing the fault •  Neither active nor passive circuit breaker is directly applicable in large capacity LIB systems 3)  Suppression of Fault preventing Propagation •  Pack fault response depends on pack integration characteristics as well as individual cell safety characteristics •  Using safe cells does not guarantee the safety of a pack consisting of themNATIONAL RENEWABLE ENERGY LABORATORY   3
    • Electrical Current Paths in LIBs1) Battery Electric Power Delivery: “Fail-safe” concept differentiates: Charging/Discharging •  Power line (to be as conductive as possible) and •  Balancing line (to be relatively resistive);2) Balancing: Material Utilization The proposed architecture facilitates early fault detection and isolation features… NATIONAL RENEWABLE ENERGY LABORATORY   4
    • I1 I2 I1 I2 Fail-Safe Design A A A A Fault Detection Rf1 I2 – I1 •  |Signal| >> |Noise| Rf2 •  Known reference; (I2 – I1)ref = 0 •  Single measure per module Rf3 Viability  of  the  proposed   concept  has  been   inves4gated  against   Rf4 various  design  parameters   and  opera4on  condi4ons   •  Simula4on  model   •  Ini4al  tes4ng  NATIONAL RENEWABLE ENERGY LABORATORY   5
    • Impact of ISC Resistance on Signal Fault Detection Magnitude  of  signal  varies  with  ISC  resistance     A A I1 I2 Rs=  100  mΩ   Cell# 5 40Ah  (20Ah+20Ah)   8 Rf=  100  mΩ   Module  current  :  0  A   6 Current [A] Cell# 4 N  in  series  :  5   4 Shorted  Cell  #  :  2   I2-I1 + 2 Rs:  100  mΩ/  500  mΩ/2Ω   I2-I1 - Cell# 3 0 0 5 10 15 20 Time [sec] Rs=  500  mΩ   Rs=  2  Ω   Cell# 2 8 8 6 6 Current [A] Current [A] 4 4 Cell# 1 I3 I4 2 2 A A 0 0 0 5 10 15 20 0 5 10 15 20 Time [sec] Time [sec]NATIONAL RENEWABLE ENERGY LABORATORY   6
    • Experiments Confirmed Model Predictions Fault Detection Experimental  implementa4on  reproduces  the  results   Current  through  parallel  junc4ons   16Ah  (8Ah+8Ah)   1 Rf=  180  mΩ   0.9 Module  current  :  0  A   0.8 0.7 N  in  series  :  3   0.6 A A Shorted  Cell  #  :  3   0.5 Series1 I1 I2 0.4 Series2 0.3 Rs:  200  mΩ  /  1Ω   0.2 0.1 0 0 20 40 60 80 A A Rs=  200  mΩ   Rs=  1  Ω   I1 I2 7 1.4 Cell# 3 6 1.2 5 I2-I1: + 1 I2-I1: + I2-I1: - I2-I1: - Current [A] 4 0.8 Cell# 2 Series1 S 3 0.6 S Series2 2 0.4 1 0.2 Cell# 1 I3 I4 0 0 A A 0 20 40 60 80 0 20 40 60 80 -­‐1 Time [sec] Time [sec]NATIONAL RENEWABLE ENERGY LABORATORY   7
    • Isolating the Fault Fault Suppression Isolated FaultReviving “Mitigation technologies valid with A Asmall capacity batteries” Once the faulted electrode is electrically Rf1 isolated, the subsequent behavior of the faulted electrode depends on the characteristics of individual unit, and not on Rf2 the pack or module assembly characteristics. Therefore, designing safe packs can possibly Rf3 be reduced to designing safe unit cells. Rf4 Multi-series-branch configuration of the proposed design still allows partial power delivery from the pack even after the local-shut down for fault isolation is executed.NATIONAL RENEWABLE ENERGY LABORATORY   8
    • Summary & Next Steps•  Proposed “Fail-safe design for large capacity LIB system” is promising to address the barriers identified: Early fault detection, Electrical isolation, Fault suppression.•  Simulation models have demonstrated the viability of the proposed concept against various battery design parameters and operation conditions•  Collaborate with others for further evaluation, development and embodiment of the design and the methodologies proposed •  Develop/refine computational tools for specific designs •  Build prototypes and test •  Demonstrate safety improvement of the proposed design against various failure modes of vehicle battery systemsNATIONAL RENEWABLE ENERGY LABORATORY   9
    • Acknowledgements Vehicle Technology Program at DOE •  Dave Howell •  Brian Cunningham NREL Energy Storage Task Lead •  Ahmad Pesaran NREL Colleagues •  John Ireland •  Matthew Keyser •  Jeremy Neubauer Thank you for your attention!NATIONAL RENEWABLE ENERGY LABORATORY   10