Lithium Battery Safety and Performance Applications of Calorimetry
Thermal Hazard Technology October 2012
Thermal Issues with Li Batteries 1.
The effect of heat on batteriesâ€Ś
Quantifying heat produced by batteriesâ€Ś
Well known hazards: temperature exposure, over-voltage charging and over-discharge, shorting, crush, nail penetration Performance issues: effect of rapid charge/discharge, thermal management, efficiency, cell ageing and lifecycle variation -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
Applications of Calorimetry in the area of Lithium Batteries Battery Development
Battery Lifecycle & Efficiency
Determine what is the hazard and how can it be reduced
Quantifying Thermal Issues by the ARC Accelerating Rate Calorimeter technology has become the benchmark for lithium battery testing in all areas requiring thermal information
The ARC gives quantitative empirical data
•Quantifies the heat and pressure •Gives a ‘worst case’ assessment •Will allow connection to leads for in situ electrical cycling •Test components and coin-cells to large cells and modules
•Safe and easy to use •Proven technology world wide with very many household name users •Also measures heat capacity and surface temperature variation
ARC advantages with Li Batteries Options & Modifications to allow… •In situ cycling of batteries with integrated/stand-alone cyclers •Automated heat capacity measurement •Shorting, over-voltage charging / over-discharging •Abuse tests in situ; Nail Penetration, Crush (variable speed) •EV/HEV Battery testing / fast discharge •Sub-ambient testing of batteries •Quantify gas Gas collection from battery disintegration • Find spatial variation of temperature with MultiPoint
•And extra-large volume calorimeter (for large batteries as used in HEV, PHEV, EV, bicycle, plane, space, military…) •Video monitoring of battery tests to observe cell damage
Methodology – the ARC; ARC Technology for Battery testing…
The ARC - an Adiabatic Safety Calorimeter
…what is ADIABATIC? Adiabatic is the condition of NO HEAT LOSS or gain… therefore – the sample temperature is ALWAYS followed by calorimeter If the sample gives out heat… its temperature increases So … the ARC makes the Calorimeter temperature rise to match it
The traditional sample is a chemical in a sample holder In battery calorimetry the sample is a cell, module, or cell components
Ca rtri dg e H ea te r
Ra di an t Hea te r
ADIABATIC Calorimetry With conditions of NO HEAT LOSS or gain, heat release …data showing heat release ie exotherm reaction.... is given as ‘WORST CASE’ DATA a SIMULATION of what may happen WORST CASE data may then be extrapolated to any LARGER scale
Options & Modifications allow •Abuse tests in situ; Nail Penetration, Crush •Shorting, Over-voltage charging / discharging •In situ Cycling of batteries •EV/HEV Large format Battery testing / fast discharge / drive cycle simulation •Measurement of heat release over surface for Thermal Management •Determination of thermal properties – eg Specific Heat Capacity
All THT ARCs are
SAFE IN USE • Large Blast-proof Chamber of 3mm Reinforced Steel
• 3 secure locks • Space to add options and apparatus • Door Safety interlock • Automatic fume extraction
• Compressed air for rapid cooling • Simple thermocouple and gas line connections • Built in Vacuum, Gas and Pressure lines • Thermolock system – automated cut-out of heaters to avoid runaway
How the ARC Works…
SIMPLE IN USE HEAT-WAIT-SEEK (adiabatic) Automatically increases temperature in small steps to find the EXOTHERM… then follow (or track) this reaction ADIABATICALLY to finish, then H-W-S again to end temperature. OR
ARC testing on battery components: Cathode, Anode, Electrolyte, SEI. Specialized test cells are available for component testing.
SEM pictures of three LiCoO2 with different particle sizes (0.8um,2um, and 5um,respectively)
Self-heating rate vs. temperature for the three Li0.5CoO2 samples with 1M LiPF6 EC/DEC
Stopped at 220â„ƒ
Self-heating rate vs. temperature for the three Li0.5CoO2 samples with EC/DEC solvent Electrochimica Acta 49 (2004)2661-2666
Self-heating rate vs. temperature of 100mg of Li[(Ni0.5Mn0.5)0.2Co0.8]O2(900,1000, and 1100â„ƒ) charged to 4.2V(solid line) or 4.4V(dashed line) with 100mg of 1.0M LiPF6 EC/DEC electrolyte
Complete single 18650 battery: Heat-wait-seek testing Establishes: Rate of cell reaction against temperature Reaction onset temperature Maximum cell self-heating rate Total heat of reaction etc.
New Chemistries â€“ four generations of development
Temperature vs. time and self-heat-rate vs. temperature for full cell at 50-200% SOC. All batteries went to thermal runaway except the one at 50% SOC.
Battery A: Sn-LCO/ MCMF Battery B: LCO/ Graphite J Power Sources 137 (2004) 117-127
Measurement of Internal Pressure
Cylinder or prismatic, large or small, sample must be prepared in an inert environment
Data reproduced with permission of ZSW, Ulm
After Battery disintegration the calorimeter is dirty due to carbon residue, but totally undamaged. Gas/fumes are extracted via a fan in the blast box (max speed 30m2/min).
Short circuiting an 18650 battery; open or with gas collection High Impedance
Automated nail penetration & crushing system
EV or Standard calorimeter compatibility â€“ large or small cells with voltage monitoring
Replaceable piston heads â€“ large and small crushing heads or nails Custom holders for various sizes of battery
Nail penetration data Four different commercial cells tested by nail penetration from ambient temperature in the ARC.
Nail penetration in adiabatic conditions â€“ cell response is different compared to a open test. In a non-adiabatic environment, the cells illustrated by red and black would not have fully decomposed, however in the ARC the reaction continues after the penetration and the cell self-heats to decomposition. ARC isothermal mode allows comparison
Control speed nail penetration
The newest abuse option is nail penetration with controlled speed this option can be used without a calorimeter â€“ it may be used as a stand-alone option (however the PSU and control cards are still required) It can also be elegantly integrated into the calorimeter (EV or EV+) for in situ nail penetration tests Speed range: 1mm per second to 200mm per second, 17nm maximum torque
Automated Specific Heat Capacity Measurement Plot heat capacity against temperature
Test data show good agreement (< 5%) with establish literature values
â€Śthis is necessary to convert temperature data to units of Heat (Joules) and Power (Watts) to consider thermal management
Battery Performance â€“ Efficiency and Lifecycle Testing Efficiency is measured as the ratio of electrical energy stored (or released) by the cell compared to the heat generated. Cells are cycled in the ARC so heat release is directly quantified (using heat capacity to convert kelvin to joules)
Old vs. new battery, heat release rate and voltage against time at the same constant current (1C) ďƒ
CryoCool and Environmental Testing Cooling of the EV and BPCARCs to -30°C or lower allows all testing to be carried out at sub-ambient temperatures Achieved using a liquid nitrogen flow system or circulating bath. • 3600mAh LiFePO4 battery
• Charged/discharged at 1C • Operating temps: -30oC to 60oC • Test shows poor subambient performance
Surface Area Thermal Variation
Battery has multiple surface mounted thermocouples and is within calorimeter MultiPoint Options are available with 8, 16 or 24 extra thermocouples. 2 extra thermocouple measurements as standard. MPO TCs used with the EV+ are pressure sealed.
Variation of Temperature over Surface
18650 battery example Heat is primarily released at the positive terminal (the top of the battery)
large prismatic battery multipoint example test
100 amp constant-current discharge Tab temperature 90oC+ Bulk temperature 65oC âˆ´ âˆ†T = 25o C+
Multitrack feature allows tracking from the hottest thermocouple at all times. Multipoint can also be used with safety tests.
Clamping batteries and modules for High-power discharge New clamp design with holders customized for large prismatic or cylindrical batteries. Wires are connected inside the calorimeter chamber through the special collar
Fast Discharge… High power (short time) Driving cycle simulation
Options: stand –alone EV Battery Test System (eg Bitrode ‘FTN’) dSpace with programmable power supply and discharge units
Options: stand –alone The EV ARC is available with Keisokuki cyclers (KSU) from 5V/0.1A to 50V/600A The KSU can be fully integrated with ES ARC control software and ARCCal+ analysis software
High Power Discharge Tests ARC testing with high power discharges using an electronic load: 50W, 100W, 200W, 300W... 250mm
200W discharge pulses Each pulse is 60 seconds MultiPoint measurement of temperature variation across battery surface
High Power MultiPoint Discharge Constant power discharges
<= 300W 41oC rise 200W => 38oC rise
<= 100W 25oC rise
50W => 13oC rise Using heat capacity, ΔT can be converted to ΔQ (heat).
High-Power Discharge Efficiency
Cell efficiency is reduced as rate of discharge is increased. When the discharge rate is increased, more energy is wasted as heat due to the increased internal resistance. Note that the heat produced results from a combination of the internal resistance and the chemical process inside the cell.
Combined Safety/Performance Evaluation 20Ah Lithium Iron Phosphate versus 20Ah Lithium Cobalt Oxide
onset = 135⁰C onset = 90 ⁰ C
EV+ Calorimeter Designed to fulfil protocols outlined in Sandia Freedom Car and SAE Papers 3-zone calorimeter temperature control for adiabatic environment – standard Cylindrical chamber 40cm diameter by 44cm depth – can take 38 cm wide prismatic cells Sealed calorimeter to 1.5 bar above ambient (no gas escape)
Sealed, thermally guarded copper 12mm connectors for cycling (max 300amp) – standard Inert calorimeter chamber with nitrogen or flush chamber with air – standard Calorimeter chamber pressure measurement – standard Video/image recording of sample during test – standard
Gas collection using Tedlar/Kynar bags – option Gas collection using steel gas cylinders – option Gas flow rate and total gas flow measurement – option Liquid N2 delivery system for cryogenic testing – with LNFO option
Thermal surface variation (MultiPoint) – with MPO 8/16/24 option Specific heat capacity measurement – with Cp option Motorized speed-controlled nail penetration – with NPCO-SC option
External views of the calorimeter
Internal view of the calorimeter: 12 o’clock – camera window 1 o’clock – NPCO port 6 o’clock – electrical connectors 7 & 8 o’clock TC ports 9 o’clock – gas removal port
Battery Performance Calorimeter Large volume performance testing calorimeter. Designed around highcurrent charge/discharge testing, and sub-ambient isothermal operation. Not designed for safety tests.
65cm x 45cm x 50cm chamber with elliptical cylinder shape
“Thermal Guard” design for direct electrical connection to calorimeter walls, allowing current supply/draw without thermal loses (500 amp max current rating)
Combined with refrigerated circulating bath for isothermal operation to -30⁰C.
Fast tracking at up to 20⁰C/min. Includes XL blast box for user safety.
THT ARCs â€“ meeting the challenge of MEASURING THE HEAT under a range of conditions
THT ARC Users
With Battery Safety and Cycler Options the ESARC EVARC and EV+ARC are the THT family of Battery Calorimeters, they may be used to study... BATTERY R&D, SAFETY, LIFECYLCE, EFFICIENCY, PERFORMANCE battery components (anode, cathode, electrolyte, SEI) batteries (at various age or State of Charge) batteries of ‘any’ size, battery modules or packs batteries when shorted (internal or external), crushed (abuse) batteries when over-voltage charging and over-discharging (abuse) batteries when cycled to define their lifecycle and efficiency (use) batteries when tested to determine performance (use) cell, module pack testing video monitoring gas collection and pressure measurement environmental isothermal testing (-30 to +60C) measurement of specific heat capacity conversion of data to Enthalpy (Joules) and Power (Watts) testing with large, fast discharge or driving cycle simulation to be continued….!
The End The THT family of Battery Calorimeters... unique.. World Benchmark Products Battery Development Battery Safety (Use & Abuse) Battery Efficiency & Lifecycle Battery Performance