transportation safety of lithium iron phosphate batteries - a feasibility study of storing at very low states of charge

by:CTECHi     2020-02-19
In freight classification, lithium-
Ion batteries are classified as dangerous goods and are therefore subject to strict regulations and guidelines for safety Transport Certification.
One of these guidelines is to require the battery to be in a state of charge of 30%.
In this case, a large amount of battery energy is stored;
In the case of poor management, or in fact in the event of an accident at the airport, this energy can lead to ignition and fire.
In this work, we investigated the effect of removing 99 on the battery.
1% of the total storage energy.
At low voltage, under the recommended value of the manufacturer, the performance of the 8Ah c5/life4bag battery was measured during calendar aging.
Monitor battery degradation using impedance spectrum and capacity tests;
The results show that it is stored in 2.
3 after 90 days, the cell capacity did not change;
The increase in resistance is negligible. Energy-dispersive X-
The results of the ray spectrum show that the copper is not dissolved significantly.
Test the safety of the battery under low voltage, external short circuit
A circuit test was performed on the battery.
The cells are arranged to 2.
The 3 v only shows an increase in surface temperature at 6 °c, and the battery at a higher voltage shows sparks, smoke, and fire. Lithium ion (Li-ion)
Because the battery has the advantages of high specific energy density, high efficiency and long life, it has become the first choice in many application fields.
With the increasing demand for portable electronic devices and the rapid decline in battery costs, the global-
Ion batteries are increasing.
In addition, the carbon emission legislation has further promoted-
Ion batteries are prominent in renewable energy plants and energy storage systems for sustainable vehicles such as hybrid and electric vehicles.
Applicability as Li-
With the growth of the market, the market share of ion batteries continues to expand.
Demand for Li
The ion battery was developed from circa.
From 2013 to about 49 GWh.
70 GWh in 2016, is expected to rise to more than 96 GWh by 2020.
The earliest rechargeable Li in the market-
The ion battery is based on the Cobalt cathode I. e. , LiCoO (LCO)
Thus, lithium cobalt batteries have dominated the rechargeable battery market over the past decade.
However, the cycle life and safety issues of this technology have paved the way for lithium nickel manganese cobalt oxide batteries (NMC, LiNiMnCoO)
Dominate the market today.
For the safety consideration of cobalt and the demand for safer batteries, lithium carbonate-based batteries (LFP, LiFePO)
In the past few years, the cathode has gained a prominent position. Lithium-
Ion phosphate battery (LiFePO)
And now engaged in Fisker Karma series such as electric vehicles-
Universal spark electric vehicle and BYD e6/s6 dm.
Considering the production of lithium
Ion batteries are concentrated in Southeast Asia in large quantities and it is necessary to transport these devices to most end users. An industry-
The common practice is to adjust the charging status of the battery ()
The value of safe transportation is 30% to 70%, and recently the International Civil Aviation Organization has recommended limiting SoC to a maximum of 30% (ICAO). Li-
Ion batteries are classified as dangerous goods and therefore need to pass through 38th knots.
United Nations Manual for testing and standards 3 (
United Nations Transport Test)
In order to obtain transport certification.
United Nations 38 Test list.
As shown in Table 3.
Road and sea transport apply specific packing instructions, classified mainly according to the Wh energy level of the battery.
The SP188 is suitable for batteries of 100wh or smaller.
Under SP188, if a strong anti-collision housing is used, unapproved packaging does not require a package size of less than 10 kilograms in weight.
For larger packages up to 30 kilograms, the packaging must be made of metal, hard plastic, natural wood, plywood other than steel, aluminum, steel or aluminum, wood or hard cardboard, resistant to 1. 2u2009m drop test.
For batteries with a capacity greater than 100wh, the P903 is applicable and short circuit protection and unapproved packaging are one of the necessary requirements for transportation.
The battery also needs to be completely closed, with a weight limit of 30 kilograms per pack and a weight limit of 33 kilograms per vehicle.
Air transport of new batteries for adoption of UN Resolution 38.
3 test, packing guide PI965 applicable.
For 100wh or smaller batteries, the weight of each package is limited to 10 kg and the package needs to go through 1. 2u2009m drop test.
For batteries with large capacity, the maximum net weight of the cargo machine per pack is 35 kilograms (PI965, SEC IA).
However, for large Li-
Ion batteries with a net weight of more than 35 kilograms;
According to special aviation regulations, these goods need to be checked on the cargo plane.
Consignment goods need to be accompanied by documents approved by the appropriate authorities in the country of origin.
Despite these regulations and regulations, there is a long history of air cargo transport incidents involving Li-
Ion batteries and devices using Li-ion batteries.
In the form, a copy of Lee-
Ion batteries are provided.
This list includes all Li-
Ion battery chemicals including the most volatile LCO and relatively mild LFP batteries.
This list does not include battery-related air freight events related to personal equipmentg.
Samsung Galaxy Note 7 and battery integrated into aircraft eg.
Battery fire on Boeing 787 Dreamliner
Malaysia Airlines Flight 370 of 2014 was later confirmed to carry lithium-
The ion batteries in the cargo hold sparked speculation that they might have caused a fire that crashed the plane.
The Egyptian airline flight 804, which crashed in 2016, was not confirmed, but caused similar suspicions.
This shows that people are on the transportation of Li-
Therefore, the air ion battery is still an open research problem.
A method for transporting lithium
The ion battery is safer to remove the stored energy before transportation.
In this work, we investigated the feasibility of transporting Li-
More specifically, it\'s a lithium-ion battery (LFP)
Battery, at a voltage corresponding to 0% SoC and lower Ie.
, After removing almost all the energy stored in the electro-chemical system.
Lithium-
Ion battery chemistry, the potential of the graphite negative electrode at a very low battery voltage (LiC)
Significantly increased compared to Li/Li current and may cause the copper current collector to dissolve.
Therefore, dissolved copper ions can pass through the separator and deposit, which leads to the growth of copper shoots during circulation.
Copper shoots may cause internal short circuit
Circuit, endangering safety.
In addition, the corrosion of the copper current collector causes a loss of mechanical and electrical contact between the current collector and the negative electrode assembly, resulting in an increase in the battery impedance.
Corrosion products with poor electronic conductivity can lead to over-potential;
Coupled with the loss of mechanical contact, this encourages uneven current (
Therefore, very high localized current)
And the potential distribution that leads to the growth of lithium shoots.
At very low potentials below 1 v, the morphology of cathode materials can also be changed.
Side effects that occur during extreme over-discharge lead to solids-
Amortization of the state of transition metal compounds.
The change of electrode morphology leads to a decrease in capacity.
LFP-based batteries and other lithium-at extremely low voltages-
Ion battery chemistry.
In this paper, after studying the effect of long-term low voltage storage on the performance of LFP batteries, the safety of LFP batteries exposed to external short voltage at such low voltage is studied.
Circuit conditions (
Most common causes of events in the table)is studied.
The results show that there is a voltage stability window in which degradation related to storage batteries at low voltage is negligible;
At the same time, the battery is actually \"inert\" because the energy stored in the electro-chemical system is almost completely extracted.
In this condition, transporting batteries will be relatively safe than the industry practice adopted today, with little in terms of reducing the cost of long-term batteries
Battery function.
This pilot study selected relatively benign LFP cells, as even this benign chemical reaction has the potential to cause a fire in the event of an external short circuit.
Due to the aging mechanism under low SoC in all Li-
The chemical and fire hazards of ion batteries are related to the stored energy, and the high level conclusions drawn by studying LFP batteries may be inferred as other Li-
Ion cell chemistry
A detailed investigation of other Li
Ion-cell chemistry in this area will be discussed in future studies.
The experimental procedure used in this study is given in the \"experimental details\" section.
The \"low pressure calendar aging results\" section shows the length
Results of aging of long-term low voltage storage.
The conclusions of this section are used to determine the optimal aging conditions to advance the external short time forward
Circuit tests described in the \"short circuit abuse experiment\" section.
General discussion on aging test results and short time
The circuit test results are given before summarizing the key contributions.
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