Why can't lithium battery replace lead battery?

Demand

At present, Lithium Batteries are mainly used in the field of 3C electronic products such as mobile phones and tablet computers, and have high energy density in commercialised batteries, but still cannot meet people's needs, why? In short, a larger cell cannot be squeezed into a limited space. People have strict requirements on the volume and weight of 3C products, so the space that can be given to the battery is limited.

Characteristics

Although it is widely recognised that lithium-ion batteries have a tendency to dominate, they are weaker than lead-acid batteries in at least two aspects, and these two points are more deadly in the car starting power supply: low temperature performance and high current performance.

First of all, low temperature performance, lead-acid battery at low temperature discharge performance is actually very good, at -10°C temperature with 10C discharge rate, more than 10V voltage holding time can be more than 90s, which is enough to cope with the harsh environment in most areas of China; The low-temperature performance of lithium-ion batteries is much worse, is the voice of LiFePO4 (lithium iron phosphate battery) material, its low-temperature discharge performance will be greatly attenuated, in the northeast and northwest regions is difficult to achieve practical application, or far from practical application.

Safety

The starting system used in the car is mostly fixed in the engine compartment and has a high level of leak tightness, so safety is very important for the car, and the heat and potential danger caused by the instantaneous release of hundreds of amperes of current are self-evident.

Secondly, even if there is an accident, the positive and negative electrode materials are lead compounds, and the electrolyte is still sulphuric acid solution, all three of which are non-flammable and can only cause the surrounding parts to burn.

The anode material of a lithium-ion battery is graphite, a type of carbon material, and there is no need to say more about flammability. The electrolyte is an ester solvent and lithium salt, and the ester solvent is not only flammable but also has a strong volatility, once a large amount of heat release or in the car collision prone to combustion or even explosion, the accident will be pushed to a level, the consequences are unimaginable. At the same time, there is an important factor that cannot be ignored, lithium-ion batteries are easy to form lithium dendrites in the negative electrode when the current is discharged, pierce the diaphragm and cause the internal short circuit of the battery to explode, which is a consensus in the Lithium Battery industry.

In fact, there are many other problems, such as the stability of the electrode material caused by the battery in a high state of charge (SOC) for a long time is also a big problem, at present there are not many studies on it, many mechanisms are not clear, and so on, there are too many safety problems of lithium-ion batteries, here it is not clear.

Cost

In terms of cost, the cost of lead-acid batteries is very low, whether it is electrode material, electrolyte or assembly, the environmental requirements are much lower than those of lithium-ion batteries.

As far as electrode materials are concerned, most of the lithium-ion battery electrode materials require complex process preparation and must go through a high-temperature heat treatment process (graphitisation temperature is more than 2000 degrees, and most of the positive electrode materials need 70 or 80 degrees), and the cost is mostly 15-20w/tonne or more, graphite may be lower; lead oxide and lead sulphate used in lead-acid batteries are relatively cheaper.

Electrolyte lithium-ion batteries use several ester solvents, the price is higher, and there are strict requirements for water content, usually within tens of ppm, electrolyte salt lithium hexafluorophosphate is not only expensive, but also easy to decompose, causing danger, one of the decomposition products is terrible HF, Baidu can know its harm! The lead-acid battery is a sulfuric acid solution, which does not need to be said.

Environment

At present, most of the voices in society say that lead-acid batteries pollute the environment, lithium-ion batteries are environmentally friendly, in fact, this is a big misunderstanding, before the small lead-acid battery factory in the South too much do not pay attention to low carbon and wantonly emissions, and coupled with our country wants to reduce the scale of lead-acid batteries, vigorously develop new energy, so the media argument also has a strong focus, in fact, it is not the case.

One of the things that lead-acid batteries do well at the moment compared to lithium-ion batteries is the recycling mechanism. At the moment, lead-acid batteries are mainly used in electric bicycles and car starter systems, both of which have a strong focus, i.e. the user goes back to the specialist shop to change the battery when it is replaced, why? You can turn old batteries into money to buy new ones! These used batteries are basically returned to the special lead plate recycling plant for secondary treatment to recover the electrode material.

Lithium-ion batteries Have you ever seen a special organisation to recycle and reuse electrode materials? The reasons are as follows: First, the application field of lithium-ion batteries is too wide, which determines the difficulty of its recycling; Second, lithium-ion batteries are mostly small, usually people do not need mobile phones or mp3, most of them are directly thrown away or sold, these batteries are basically lying in the trash can.

Although there are fewer heavy metals in lithium-ion batteries, only the positive electrode material contains cobalt metal, but it can not carry such a large user volume, ah, in the long run, this is still a problem, so in general, lead-acid batteries as long as they pay attention to the relevant low-carbon measures in the manufacturing process is no problem, because they are sealed and maintenance-free in use, and there will be a corresponding recycling mechanism.