Why does the lithium iron phosphate battery 'hip' in winter?

by:CTECHi     2021-07-26

Why do lithium iron phosphate batteries not last in winter? To analyze the reasons.

The following is just a personal opinion for your reference.

People who may not know, do not know what a lithium iron phosphate battery is, so let me briefly talk about it first.

Lithium iron phosphate battery is a lithium-ion battery that uses lithium iron phosphate (LiFePO4) as the cathode material and carbon as the anode material. The rated voltage of the monomer is 3.2V. The charge cut-off voltage is 3.6V~3.65V.

Discharge principle: The charge and discharge reaction of lithium iron phosphate battery is carried out between the two phases of LiFePO4 and FePO4. During the charging process, LiFePO4 gradually separates from lithium ions to form FePO4, During the discharge process, lithium ions intercalate into FePO4 to form LiFePO4.

Why lithium iron phosphate batteries are not easy to use in winter, I summarize the following 2 points for your reference.

1. First of all, the lithium iron phosphate battery has some performance defects. The principle of the lithium iron phosphate battery is also mentioned above. The electrolyte moves quite slowly in a low temperature environment. , Thereby affecting the transfer activity of lithium ions between the positive and negative electrodes, resulting in a decline in battery charge and discharge performance. Simply put, in a low temperature environment, it is not that the lithium battery is really out of power, but that it has electricity but cannot be discharged normally.

2. Secondly, its low temperature performance is relatively poor. There are many tests showing that lithium iron phosphate batteries cannot make electric vehicles run at low temperatures (below 0°C). Although some manufacturers claim that the capacity retention rate of lithium iron phosphate batteries is good at low temperatures, that is when the discharge current is small and the discharge cut-off voltage is very low. According to analytical data, the capacity of an ordinary lithium battery will be reduced by 20% when it is at zero degrees Celsius. When it reaches minus 10 degrees Celsius, the capacity may be only about half.

Low temperature is the weak point of lithium iron phosphate batteries, minus 20 degrees can release 50%-70% of the rated capacity, and the lower temperature will be smaller, minus 40 degrees basically It's just a building block!

Considering comprehensively, the cost performance of lithium iron phosphate power batteries is more than 3 times that of lead-acid batteries.

The only disadvantage of lithium iron phosphate batteries is that they are not durable in winter. Generally speaking, they are the first choice in electric motorcycles, and they may be better in terms of temperature adaptation.

The shortcomings of lithium iron phosphate batteries are also mentioned above, so let's talk about why there are so many places where they are used more?

In fact, there are still many advantages of lithium iron phosphate batteries.

1. First of all, high temperature performance is good. The peak value of lithium iron phosphate electric heating can reach 350℃-500℃, the working temperature range is wide, and the high temperature resistance is good.

2, followed by large capacity. It has a larger capacity than ordinary batteries (lead-acid, etc.).

3, then light weight. The volume of the lithium iron phosphate battery of the same specification and capacity is 2/3 of the volume of the lead-acid battery, and the weight is 1/3 of the lead-acid battery

4, and then safety Good aspect. The electrochemical performance of the cathode material of lithium iron phosphate battery is relatively stable, which determines that it has a stable charging and discharging platform. Therefore, the structure of the battery will not change during the charging and discharging process, and it will not burn and explode. It is still very safe under special conditions such as filling, squeezing, and acupuncture.

5. Its cycle life is relatively long. The 1C cycle life of lithium iron phosphate batteries generally reaches 2000 times, or even more than 3,500 times, and the energy storage market requires 4000-5000 times or more, guaranteeing a service life of 8-10 years, which is more than 1,000 cycles of ternary batteries Life span, and the cycle life of long-life lead-acid batteries is about 300 times.

6. Widely used. For example, large electric vehicles: buses, electric vehicles, tourist attractions, etc.;

Light electric vehicles: electric bicycles, cleaning vehicles, electric wheelchairs, etc.;

Power tools: electric drills, chainsaws, lawn mowers, etc.;

Toys: remote control cars, boats, airplanes, etc.;

Energy storage equipment for solar and wind power generation; UPS and emergency lights, warning lights and miner's lamps (the best safety);

Small medical Equipment and portable instruments, etc.

According to personal understanding, the recycling of lithium iron phosphate batteries is not yet mature, because batteries have life limitations, while lithium iron phosphate batteries are growing rapidly, and the amount of scrap is If it is relatively large, its recycling cost is relatively high, because it does not contain precious metals, and its economic value is relatively low, which increases the difficulty of recycling. The harm of lithium iron phosphate batteries is also relatively large. The chemical substances such as LiPF6, organic carbonates, copper, etc. are all included in the national hazardous waste list. If the discarded lithium iron phosphate batteries are not recycled, it will be harmful to the environment and human health. Great harm. So I hope that the future development will get better and better and the performance will get better and better.

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