Reducing the Flammability of Lithium Ion Batteries Daikin America, - - PowerPoint PPT Presentation

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Daikin Confidential

Reducing the Flammability of Lithium Ion Batteries

Daikin America, Inc.

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Daikin Confidential

• The Fire Safety of Lithium ion Batteries (LiB) has been a concern

since their initial adoption.

• LiB fires in laptops
• UPS Boeing 747 crash in 2010 blamed on LiB fire
• EV battery fires – Chevrolet Volt and Fisker Karma
• LiB development work has focused on improving energy density,

power, and increasing battery life.

• Fire safety has been addressed by improving auxiliary

support systems

• Little work done on improving the fire safety of the LiB cells

until now.

• Daikin America – A global leader in fluorochemical products, has

developed electrolyte chemistry that greatly increases the fire safety of LiB’s.

Fire Safety of Lithium Ion Batteries a Concern

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Daikin Confidential

LIB model reaction

Charging reaction using hydrocarbon (ie. flammable) electrolyte

LiCoO2 + C + electrolyte CoO2 + CxLi + electrolyte

• xidizer

fuel

ignition source – heat, spark

A charged conventional lithium battery contains fuel (electrolyte), an oxidizer (active), and multiple possible ignition sources.

Root Causes of Fire in LiB Batteries

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Daikin Confidential

Using safer actives – remove oxidizer.

• Myth: using LiFePO4 cathodes eliminate fires in lithium ion
• batteries. Would not fully eliminate fire possibility .
• Report DOT/FAA/AR-09/55 clearly indicates extreme fire

hazard still possible due to the presence of flammable electrolyte even using LiFePO4 Minimize ignition sources through engineering controls – remove ignition.

• May identify causes but flammable fuel still present.

Eliminate flammability of electrolyte – remove fuel.

• Render electrolyte non flammable through chemistry.
• Replacing the flammable electrolyte (fuel) is the ONLY

strategy for preventing fire.

Fire Mitigation Strategies in LIB Cells

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SADK -01 Conventional electrolyte SADK-03 Daikin electrolyte (20% wt fluoroadditive

Testing at independent laboratory shows flammability eliminated/reduced with added 20% fluorochemical content. Burst testing was completed using 18650 cells using hot wire ignition source.

Burst Test and Flammability

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Daikin Confidential

time until ignition temperature at vent burst flame duration

Numerical test results with some typical electrolyte hydrocarbon mixtures (1st four) shown for comparison.

Burst Test and Flammability Results

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Addition of D7 fluorochemical enhances safety upon overcharge.

LFP／artificial graphite, 3.6V, SOC=100%, １C 12V overcharge （10Ah laminate cell）

• A. 1.0M LiPF6, EC/EMC=30/70
• B. 1.0M LiPF6, EC/EMC/D7=30/60/10

explosion no explosion 3 hrs. 3 hrs. Overcharge Test - Daikin

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In separate independent laboratories, Daikin electrolyte also containing 20% fluorochemical shows superior cycling behavior compared to conventional hydrocarbon electrolyte. Note cycle number on x axis. Fluorinated electrolyte increases cycle life by more than a factor of 2 down to 70% retention.

Cycling Behavior

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Daikin Confidential

Fires in lithium ion cells are due to interaction of electrolyte (fuel), active (oxidizer) and spark/heat (ignition source). Most viable safety solution is elimination of flammable electrolyte. Daikin America produces electrolyte with fluorinated additives which:

• Show enhanced safety – no flammability
• Demonstrate improved cycle performance – greater

battery lifetime

• Have been verified in-house and in independent

laboratories A safe and reliable Lithium ion battery can be engineered using such an electrolyte.

Conclusions / Future Prospects