Phosphates in Li-ion batteries and automotive applications

Phosphates in Li-ion batteries and automotive applications MY. Saidi*, H. Huang, TJ. Faulkner (Batteries 2009) Valence Technology, Inc., (NV USA) Yazid.Saidi@Valence.com www.valence.com 1

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Li-ion - HEV market Conventional lithium-ion batteries for HEVs are almost ready for commercialization Intent is displacement of NiMH batteries, Li-ion promises long term reduced cost, with a higher level of performance combined with a longer life. Major hurdle is cost reduction and safety; current cost is approximately twice the goal. Additional improvements include Calendar life projections of 8-12 years are based on limited data Abuse tolerance and improved safety Low-temperature performance Other existing technologies: LMO, NCA, NMC and phosphates as cathodes Li 4 Ti 5 O 12 and alloy composite as anodes www.valence.com 3

Li-ion for the automotive industry Higher power density for HEV Higher energy density for PHEV/EV Higher voltage/cell: allows fewer cells/pack (need to meet capacity target as well) NiMH approaching technology limits? Environmentally friendly chemistry? Certainly LMO and phosphates. Cost ($/kwh) Attribute Energy Density (Wh/kg) Power Density (W/kg) Volumetric Energy Density (Wh/L) Self Discharge (% / month) In/Out Efficiency (%) Temperature Range ( C) Cycle Life: EV (# cycles) Cycle Life: HEV (# cycles) Calendar Life (years) Ni-MH <70 1600 200 35 20 90-10 to +40 ~1000 300,000 > 10 Li-Ion ~150 >3000 >300 30-35 2-5 > 95-30 to +50 1000-3000 300,000 2 >10 www.valence.com 4

A power-assist HEV battery What are power-assist HEV requirements? Must absorb and release high power pulses (25kW / 10sec) efficiently (90% energy recapture) and repeatedly (300,000 charge-discharge pulse cycles over life of vehicle) Must be inexpensive, lightweight and fit a small space Capacity is not necessary release short pulses. only needs to store and Much higher specific power than PHEV Power assist battery has to be smaller in size and capacity to meet cost and weight targets, www.valence.com 5

Application power/energy HEV 1-2 KWh P/E 20 20-40 liters PHEV 4-15 KWh P/E = 3-15 40-80 liters EV > 40KWh P/E ~ 2 170 liters 1 10 100 Energy kwh Different applications : different requirements www.valence.com 6

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FreedomCAR specifications (HEV) Characteristics Units Power- Assist (Min) 2003 Power- Assist (Max) 2003 IFR PC Pulse discharge power (10s) kw 25 40 Spec (25) Peak regenerative pulse power (10s) kw 20 35 Spec (20) Total available energy (over DOD range 0.3 (1C rate) 0.5 (1C Rate)? where power goals are met) KWh Spec (0.3) Minimum round-trip energy efficiency % Cold cranking power at -30 C (three 2-s pulses, 10-s rests between ( o C) Cycle life for specified SOC increments kw cycles 90 (25-Wh cycle) 90 (50-Wh cycle) 5 7 300,000 25- Wh cycles (7.5MWh) 300,000 50- Wh cycles (15MWh) Calendar Life years 15 15 FreedomCAR Battery Test Manual For Power-Assist Hybrid Electric Vehicles www.valence.com 8? 8 ( m > 90-25? 300,000 mixed pulse cycles 8 (? Maximum weight kg 40 60 <17 (cells only) Maximum volume liter 32 45 <8 (cells only) max<400 max<400 min>(0.55 x min>(0.55 x?2.1-3.82 (single Operating Voltage limits Vdc Vmax) Vmax) cell) <30% max 30% max 30%? Power Margin % (projected)

Advantages of Lithium Ion 100,000 10,000 1,000 Super capacitors Lead acid spirally wound Ni-Cd Li-Ion Very High Power Li-Ion High Power Ni-MH 100 Lead acid Na / NiCl2 LiM-Polymer Li-ion High Energy 10 1 0 20 40 60 80 100 120 140 160 180 200 Specific Energy, Wh/kg at Cell Level HEV applications require a cell to deliver at least 1000W/Kg. At this Level of power, Li-ion delivers twice the energy density than Ni-MH. Phosphates in a power design easily meet the power requirements Source: SAFT www.valence.com 9

Voltage vs. Rate (IFR26650) 3.5 3.0 2.5 2.1A 20A 30A 40A 2.0 1.5 0.0 0.5 1.0 1.5 2.0 2.5 Capacity / Ah Time / h 26650: power design shows very little polarization at higher rates (min. self heating lag) www.valence.com 10

50C (100A) pulse on IFR 26650 P u lsin g at t/s P o w er/w P o w er d en sity (W /kg )* P o w er d en sity (W /kg )** 5 235.8 2948 3369 100% S O C 10 232.1 2901 3316 20 226.9 2837 3242 30 223.8 2798 3197 55% S O C 10 208.4 2605 2977 * 80g/cell; ** if 70g/cell Specific power capability derived from a fixed 100A pulse. www.valence.com 11

High-rate pulse on IFR 26650 Power Pulse I @ 100%SOC Rate t/s Power/W density (W/kg)* Power density (W/kg)** 100A 50 5 235.8 2948 3369 150A 75 5 278.8 3485 3983 180A 90 5 278.5 3482 3979 200A 100 5 288.2 3602 4117 216A 108 5 273.4 3417 3905 Specific power capability derived or a fixed pulse time of 5s. * 80g/cell; ** if 70g/cell www.valence.com 12

Hybrid Pulse Power Capability (HPPC) FreedomCar test manual 2003 IFR Power Cell (18650) V o lts 4.0 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4 2.2 2.0 Voltage Current 2.725 2.73 2.735 2.74 2.745 2.75 Time Hr Pulse train consisting of 10-sec discharge and charge pulses with 40-sec rest between Determines the DCIR under realistic operating currents (25%-75% of max) Repeated at 10% SOC intervals over 1 complete discharge half-cycle 50 40 30 20 10 0-10 -20 C u rre n t A www.valence.com 13

10-Second DCIR at 36A (IFR26650) 0.05 0.04 0.03 0.02 0.01 0.00 0% 20% 40% 60% 80% 100% DOD / % LiFe(Mg)PO 4 flat operating voltage combined with a flat DCiR helps to further extend the useable DOD range. www.valence.com 14

Available Power & Energy (IFR26650) 50000 40000 30000 20000 10000 0 40000 30000 20000 10000 BSF = 200 0 0 500 1000 1500 Regen PPC (W, xbsf) Wh @ 1C (xbsf) Power capability (HPPC) of a 26650 power design using LiFe(Mg)PO 4 at BOL www.valence.com 15

Cold cranking test (IFR26650) Voltage Power Cell voltage / V 3.5 3.0 2.5 2.0 5000 4000 3000 2000 1000 Pulse power / W (x BSF) 1.5 0-2 2 6 10 14 18 22 26 30 34 38 Time / s -25 o C/45%DOD www.valence.com 16

discharge PPC (W, xbsf) 40000 30000 20000 10000 HPPC vs. cycles 0 0 0% 20% 40% 60% 80% 100% DOD / % HEV cycling target: 300K Cycles 30000 24000 18000 12000 6000 Regen PPC (W, xbsf) Power goal d/0 cycles d/90k cycles d/120k cycles d/150k cycles d/180k cycles d/210k cycles d/240k cycles d/240k cycles d/270k cycles d/300k cycles R/0 cycles R/90K cycles R/120K cycles R/150K cycles R/180k cycles R/210k cycles R/240k cycles R/240k cycles R/270k cycles R/300k cycles Poly. ( d/0 cycles) IFR-PC exhibits excellent power and energy retentions under HEV cycling regime Meets HEV cycle life target: 300K (HEV cycles) % of initial capacity 100% 80% 60% 40% 20% 0% Capacity vs. cycles 0 100000 200000 300000 Cycles % of initial PPC @ 40%DOD 100% 80% 60% >77% 40% >80% 20% 0% Power vs. cycles 0 100000 200000 300000 Cycles www.valence.com 17

Why phosphates for the HEV application? A flat and relatively low OCV Wide usable range for power/regen pulses Overcharge voltage is a safe margin above the normal end of charge voltage Operating range can be extended close to fully charged Low power fade over 300,000 mixed pulse cycles Made from the least expensive transition metals available via most efficient and cost effective method (carbothermal) High thermal stability built in robustness Phosphate lithium ion can meet most HEV requirements www.valence.com 18

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Introduction In this segment, lithium-ion is also viewed as the most commercially viable chemistry for PHEVs due to its potential for much higher energy and power density than traditional technologies. Within Li-ion, phosphates offer the distinct advantage of paramount importance in large format applications: improved safety Further improvements are needed before a larger penetration of HEVs and PHEVs can take place into the marketplace. www.valence.com 20

Plug-In hybrid application (PHEV) Motivation: Hybrid electric vehicles: 40-50 MPG using fossil fuels PHEV: >100 MPG by displacing fossil fuels with grid electricity New technological challenges for PHEV batteries: Must store significant amount of energy to displace fossil fuels Larger, heavier battery is required Additional battery weight increases vehicle fuel/electricity usage 10Wh/mile for each 100kg (Rousseau, 2007) Li-ion = Higher energy density battery = better vehicle performance Must use as much as possible of this stored energy Significant depth of discharge on cycling (DOD) produces more wear and tear Lithium-ion technology: one of the few chemistries that can meet energy density and high DOD cycle life requirements www.valence.com 21

PHEV Battery Specifications Table 1 is cited from Battery Test Manual For Plug-In Hybrid Electric Vehicles U.S. DOE Vehicle Technologies Program. Specifications for PHEV10 and PHEV40. www.valence.com 23

Maximizing Cell Energy Density Reduce amount of inert material: Lighter enclosure Thinner separator Less conductive additive Thicker electrodes Increase utilization of active material: Smaller primary particle size More conductive additive Thinner electrodes More porous electrodes Increase amount of active material: Larger primary particle size More dense electrodes Cell energy optimization calls for a balance of higher utilization, less inert material and more active material Powder morphology is key to maximizing energy www.valence.com 24

IFR-EC 26650 wide useable SOC range Dis. PPC (W, xbsf) 90000 80000 70000 60000 50000 40000 30000 20000 10000 0 5%DOD 10%DOD 58.5kW(BOL) 45kW (EOL) 80%DOD 60000 52500 45000 37500 30000 22500 15000 7500 0 Regen PPC (W, xbsf) 0 1000 2000 3000 4000 5000 6000 Wh @ 10KW (xbsf) Regen power capability is > 75% above the target at EOL (margin), even at very low DOD. DOD MIN can be reduced from 10% to 5%, or even lower, extending available energy. More available energy for CD mode = BSF can be further decreased by 6% to 12%. www.valence.com 25

PHEV: Long Cycle Life at 100% DOD 100% 80% 60% 40% 20% 0% 0 1000 2000 3000 4000 Cycle number IFR18650EC exhibits very long life at e.g. C/2 cycling, 100% DOD After 4000 cycles, 80% of initial capacity is retained. www.valence.com 26

Higher Rate over Shorter Range 100% 80% 60% 40% 20% 2008 2009 0% 0 500 1000 1500 2000 2500 3000 Cycles Shorter range, higher rate, PHEV designs (PHEV10 etc.) mitigate the higher cost of larger packs and have a a higher chance for commercialization Without sacrificing cell capacity, IFR18650 energy design s rate capability has been improved significantly through cell design to meet this challenge Constant current cycle life at 2C charge, 2C discharge rate, 100% DOD, is predicted to reach more than 2300 cycles to 80% of its initial capacity. www.valence.com 27

FreedomCar PHEV10 CD Cycling From Battery Test Manual For Plug-In Hybrid Electric Vehicles U.S. DOE Vehicle Technologies Program. One CD cycle is a series of 5 above profiles, followed by a recharge. Energy throughput / cycle = 3.4kWh 5000 CD cycles are required over lifetime of the battery. www.valence.com 28

IFR18650EC: CD Cycle Life (Projected) % of remaining energy 120% 100% 80% 60% 40% 20% 0% 0 2000 4000 6000 Cycles Current / A 4 0-4 -8-12 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Time / h One single CD mode discharge Charge depleting (CD) cycle life criterion: 5000 cycles This 360s-pulsing profile is repeated five times as a single discharge before recharging battery at 1.4kW rate The IFR18650EC is predicted to deliver 5000 cycles under CD operation. www.valence.com 29

Valence and PHEVs Battery supplier to PHEV integrators as early as 2005. Testing conducted at cell, module, and pack levels. Incorporated feedback from early adopters to improve performance, design, and functionality. www.valence.com 30

Early adoption First pack was assembled in Feb, 2005. Consisted of 18 U1 off the shelf modules (12.8V/40Ah) in series and controlled by Energy CS Battery Management System Originally charged with PFC-20 charger. www.valence.com 31

Engineering Evolution Most recent system includes 18 modules (12.8V/40Ah), but not set inside a case. Laid out for better thermal management. Integrated BMS. Uses updated battery management system from Energy CS which includes: Built in data logging GPS Around the clock balancing Communication with charger. www.valence.com 32

Pack Performance The Energy CS conversion provides the greatest range of all other conversions on the market (provided boosted electrical assistance for approximately 66 miles while averaging 107 mpg per Argonne National Lab testing). This performance cost only about $1 worth of electricity with overnight charging. www.valence.com 33

Promising New Materials 6.0 LCP LVP LVPF LMP LFP LCO 5.0 4.0 3.0 2.0 1.0 LCO is used as a reference 0 100 200 300 400 500 600 Energy / WhKg -1 These new materials promise more energy through higher voltage www.valence.com 34

Enabling technologies Materials Safety of phosphates Overcharge prevention simpler than layered oxides Balancing is a functionality issue rather than a safety issue Thermal runaway does not propagate through pack CTR Low-cost high-performance materials Cells Larger format cells will reduce complexity and cost of modules, packs Packs Epoch BMS provides intelligent interface, balancing and soft fail modes www.valence.com 35

Summary Phosphates An enabling technology especially in the large format arena The most thermally stable Li-ion chemistry Exhibit excellent performance characteristics for a variety of applications Offer a competitive cost advantage due to inexpensive raw materials, design simplicity and longevity Show a high tolerance under abuse conditions Have the least impact on the environment (LFP) www.valence.com 36

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