LiFePO4 Battery

The lithium iron phosphate (LiFePO4) battery, also called LFP battery, is a type of rechargeable battery, specifically a lithium ion battery, which uses LiFePO4 as a cathode material.

LiFePO4 battery vs. Lead Acid Battery

Battery Type

LiFePO4 Battery

Lead Acid Battery

Nomenclature

LFP Battery

Lead acid Battery

Easiness of manufacturing

More difficulty

Easy

Voltage fluctuation in working

Remains stable with different output

Voltage fluctuation based on output

Cycle life
(Residual capacity over 5%)

1500 ~ 3000 cycles  (Eqivalent of around 10 years life)

150~300 times (Life is estimated 1~2 years)

Capacity

Very stable and very little affection by output current

Suffer a big affection in by output current. Capacity will be much smaller than rated capacity when output current is large.

Depth Of Discharge (D.O.D.)

99%

50% ~ 60%

Self discharge rate (per month)

1~1.5% (Capacity remains over 80% even the battery is idled for one year)

30% (Battery capacity drops near to zero if it is unused for 3 months)

Fast charge capability

Capable of using 1C~3C charging rate (Charge to full capacity can be finished within 20 minutes)

Maximum charging rate is 0.2C (It needs at least 6 hours to fully charge the battery)

Max. discharge rate

10C~30C

1C~5C

Discharge working temperature ℃

-20~+75

-20~+55

Memory effective

None

None

Thermal stability

Outstanding

Acceptable

Weight (Compare to the same capacity)

1/2 of weight to lead acid battery

comparatively heavier weight

Installation

Any direction

Upright position is necessary

Safety

Mild warm, no explosion and firing

Dangerous of acid leakage

Environmental conform-ability

Conforms to RoHs standard

Violet RoHs standard;Lead and sulphate acid are pollutant

Disposition of used battery

No recycle required

Needs special recycle, after treatment utility



LiFePO4 battery vs. Lithium Battery


Most lithium-ion batteries (Li-ion) used in consumer electronics products are lithium cobalt oxide batteries (LiCoO2). Other varieties of lithium-ion batteries include lithium-manganese oxide (LiMn2O4) and lithium-nickel oxide (LiNiO2). The batteries are named after the material used for their cathodes; the anodes are generally made of carbon and a wide variety of electrolytes are used.

Advantages and disadvantages:

The LiFePO4 battery uses a lithium-ion-derived chemistry and shares many of its advantages and disadvantages with other lithium ion battery chemistry.

However, one key advantage over other lithium-ion batteries is the superior thermal and chemical stability, which provides better safety characteristics than lithium-ion batteries with other cathode materials.Due to significantly stronger bonds between the oxygen atoms in the phosphate (compared to the cobalt), oxygen is not readily released, and as a result, lithium iron phosphate cells are virtually incombustible in the event of mishandling during charge or discharge, and can handle high temperatures without decomposing.

Lithium Iron Phosphate chemistry also offers a longer cycle life over standard lithium ion cells.

The use of phosphates also reduces the cost and environmental concerns of Cobalt cells, particularly in regards of cobalt entering the environment through improper disposal, with considerably increased safety over the cobalt chemistry type of lithium battery cell, particularly when compared to LiPo battery cells commonly used in the aero modeling hobby.

One of the other major advantages for LiFePO4 when compared with LiCoO2 is higher current or peak-power rating.

LFP batteries have some drawbacks:

The energy density (energy/volume) of a new LFP battery is somewhat lower than that of a new LiCoO2 battery. (14% reduction in energy density) Battery manufacturers across the world are currently working to find ways to maximize the energy storage performance and reduce size & weight.

Many brands of LFPs have a low discharge rate compared with lead-acid or LiCoO2. Since discharge rate is a percentage of battery capacity this can be overcome by using a larger battery (more ampère-hours). However, A123Systems claims 100C pulse discharge rate.[9] While LiFePO4 cells have lower voltage and energy density than LiCoO2 Li-ion cells, this disadvantage is offset over time by the slower rate of capacity loss (aka greater calendar-life) of LiFePO4 when compared with other lithium-ion battery chemistry (such as LiCoO2 cobalt or LiMn2O4 manganese spinel based lithium-ion polymer batteries or lithium-ion batteries). For example:

After one year on the shelf, a LiFePO4 cell typically has approximately the same energy density as a LiCoO2 Li-ion cell.

Beyond one year on the shelf, a LiFePO4 cell is likely to have higher energy density than a LiCoO2 Li-ion cell due to the differences in their respective calendar-lives.

Safety:

LiFePO4 is an intrinsically safer cathode material than LiCoO2 and manganese spinel. The Fe-P-O bond is stronger than the Co-O bond, so that when abused, (short-circuited, overheated, etc.) the oxygen atoms are much harder to remove. This stabilization of the redox energies also helps fast ion migration.[citation needed]

As lithium migrates out of the cathode in a LiCoO2 cell, the CoO2 undergoes non-linear expansion that affects the structural integrity of the cell. The fully lithiated and unlithiated states of LiFePO4 are structurally similar which means that LiFePO4 cells are more structurally stable than LiCoO2 cells.[citation needed]

No lithium remains in the cathode of a fully charged LiFePO4 cell—in a LiCoO2 cell, approximately 50% remains in the cathode. LiFePO4 is highly resilient during oxygen loss, which typically results in an exothermic reaction in other lithium cells.

Lithium battery chemistry comparison

Cell Chemistries LiCoO2 LiMn2O4 LiNiMnCoO2 LiFePO4
Rate Voltage
3.7V
3.8V
3.6V
3.2V
Charging Voltage
4.2V
4.2V
4.2V
3.7V
Dischargiing end Voltage
3.0V
2.5V
2.5V
2.0V
Energy Density (Wh/L)
447
253
327
222
Energy Density (Wh/Kg)
140-145
105-115
140-155
90-110
Cycle Life
>700
>500
>700
>1800
Self-Discharge Rate (Month)
1%
5%
1%
0.05%
High Temperature Performance
(55+/-2 )
Good
Acceptable
Good
Excellent
Low Temperature Performance
(-20+/-2 )
Good
Good
Good
Good
High-rate Discharge (10C)
N/A
Good
Good
Excellent
Safety & Environmental Concern
Bad
Good
Good
Excellent


Comparing LifePO4 battery with Lead-acid battery

LifePO4 battery may become a substitute for Lead-acid battery in the near future. It has many advantages over Lead-acid battery:
  • Much longer life time: LiFePO4 battery total life cycles are about 2000 times, which is 6-7 times longer than Lead acid battery and 2-3 times longer than NIMH battery and other lithium battery, also maintenance free.
  • Environmental-friendly,no heavy metals, rare metals. Sealed Lead-Acid battery made serious pollution of the environment,and other Lithium manganese no pollution but containing heavy metals. LiFePO4 batteries is environmental friendly, have no heavy metals, rare metals.
  • Small size,light weight. The volume of LifePO4 battery is 65% of lead-acid batteries and the weight is 1/3 Lead-acid.
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