Now with the abundance of electric vehicle products, various batteries have appeared on the market, such as lead-acid batteries, lithium batteries, graphene batteries, etc., and the mainstream batteries currently on the market are mainly lead-acid batteries and lithium batteries. Battery. The lithium battery is divided into lithium iron phosphate, ternary lithium and so on. These batteries are necessary "good partners" for battery cars. What are the differences between them?
Composition and working principle
A lead-acid battery is a battery whose electrodes are mainly made of lead and its oxides, and the electrolyte is a sulfuric acid solution. In the discharge state of the lead-acid battery, the main component of the positive electrode is lead dioxide, and the main component of the negative electrode is lead; in the charging state, the main component of the positive and negative electrodes is lead sulfate. The sulfate ions and hydrogen ions in the electrolyte move to the positive and negative electrodes of the battery respectively under the action of the electric field, forming a current inside the battery, forming the entire circuit, and the battery continues to discharge outward.
Lithium-ion batteries usually use carbon materials as the negative electrode and lithium-containing compounds as the positive electrode. There is a separator in the middle of the battery to avoid short-circuiting of the positive and negative electrodes. During the charge and discharge process, lithium ions travel back and forth between the positive and negative electrodes. When charging, lithium ions are deintercalated from the positive electrode and inserted into the negative electrode through the electrolyte; combined. In the process of intercalation and deintercalation of ions, accompanied by the intercalation and deintercalation of equivalent electrons, a current is generated.
The so-called lithium iron phosphate battery is a lithium-ion battery that only uses lithium iron phosphate as the positive electrode material. The characteristic of this type of battery is that it does not contain precious metal elements.
The ternary lithium battery refers to a lithium battery that uses nickel-cobalt lithium manganese oxide as the positive electrode material and graphite as the negative electrode material.
Which is safer?
In terms of safety: lithium iron phosphate > ternary lithium > lead-acid battery
The thermal stability of lithium iron phosphate is currently the best among lithium batteries for vehicles. The thermal stability of the lithium iron phosphate cathode material itself is much better than that of ternary lithium. It has extremely high stability within 500 degrees Celsius, and thermal runaway occurs only when it exceeds 800 degrees Celsius. In addition, even if thermal runaway occurs, iron phosphate The heat release of lithium batteries is also very slow, and no oxygen will be released when decomposed, only smoke will be emitted, which reduces the risk of fire.
In contrast, ternary lithium batteries have poor thermal stability and begin to dissolve at around 300 degrees Celsius. In electric vehicle spontaneous combustion incidents, it is true that ternary lithium battery models account for a larger proportion. Therefore, the ternary lithium battery has very high requirements on the battery management system, and an anti-overtemperature protection device and a battery management system are needed to protect the safety of the battery.
The lead-acid battery is more dangerous. When the lead-acid battery is overcharged, it will also produce flammable hydrogen and oxygen. Hydrogen is easy to explode in case of fire. Charging in a closed environment is also very dangerous. Although the application scope and technology of lead-acid batteries are wider and more mature than lithium battery packs. However, the safety of lead-acid batteries is much lower than that of lithium battery packs in the process of material composition and use.
Therefore, under high temperature conditions, the safety of lithium iron phosphate is relatively high.
Which has better battery life?
Battery life (same capacity): lithium iron phosphate ≈ ternary lithium > lead-acid battery
In terms of energy density, according to the information provided by domestic ternary lithium battery companies, the energy density of its 18650 cylindrical battery cells has reached 232Wh/kg, and the energy density of packaged battery packs is about 150Wh/kg.
At present, the energy density of domestic lithium iron phosphate battery cells is about 180Wh/kg. However, the blade battery can arrange the cells in sheets, just like a blade. Although the energy density of the blade battery pack is only 140Wh/kg, this new long-term battery solution improves the recombination efficiency of the cells, and the volumetric energy density increases by as much as 50%.
This means that within the same size of the battery pack, the blade battery can be loaded with more cells, and the cruising range is almost the same as that of the ternary lithium battery.
In the case of the same capacity, lead-acid batteries do not run as far as lithium iron phosphate and ternary lithium batteries. There are two main reasons. The first is because the internal resistance of lithium batteries is relatively large, and the discharge curve is relatively stable. The speed is relatively uniform, and uniform discharge can make the lithium battery last longer. The second reason is that the battery using lead-acid is basically heavier than the lithium battery, so the endurance of the heavy load is relatively poor, and the load is light. The lithium battery will run longer.
Which has a longer lifespan?
Cycle life: lithium iron phosphate > ternary lithium > lead-acid battery
Lithium batteries and lead-acid batteries can be said to be two completely different battery categories. Lithium batteries are light in weight and high in energy density. Under the same voltage and capacity, their weight is about 1/3 of that of lead-acid batteries. This is fully reflected in the service life. If the remaining capacity is 80% of the initial capacity as the end point of the test, the current lithium iron phosphate battery has been tested in the laboratory, and the cycle life is more than 3,500 times, and some of them reach 5,000 times. The test cycle life of ternary lithium batteries is about 2500 times, and the general cycle times of lead-acid batteries is between 300-500 times. In terms of cycle life, lead-acid is the shortest, and lithium iron phosphate batteries are much longer than the real life of ternary lithium batteries.
That is to say, if it is charged and discharged once a day, it will take nearly 10 years for the lithium iron phosphate battery to show significant attenuation. The ternary lithium battery has a shorter life than the lithium iron phosphate battery, that is, about 6 years, and it will begin to decay. Lead acid will decay in about one year.
However, in areas such as takeaway and express delivery, the life of these batteries may be shortened, mainly depending on the frequency of use and battery maintenance. When the time is up, it should be replaced in time.
Which market has the lower price?
Market price: lithium iron phosphate ≈ ternary lithium > lead-acid battery
When buying a car, everyone will find that lithium electric vehicles are significantly more expensive than lead-acid electric vehicles. For the same electric vehicle, installing a lithium battery is at least 800-1000 yuan more expensive than installing a lead-acid battery. The fundamental reason is that the price of lithium batteries is higher than that of lead-acid batteries.
On the one hand, lithium carbonate, the raw material required for the manufacture of lithium batteries, is a scarce resource and currently mainly relies on imports; on the other hand, it is not as large-scale and mature as the lead-acid battery industry. Therefore, in terms of cost, lithium batteries are higher than lead-acid batteries.
In addition to battery life, convenience, and ease of use, safety is also the most important consideration when choosing a battery.
Safety is the most important, lithium iron phosphate battery is the first choice
no memory
Rechargeable batteries often work under the condition of being fully charged, and the capacity will quickly drop below the rated capacity value. This phenomenon is called the memory effect. Lead-acid batteries, nickel metal hydride batteries, and nickel cadmium batteries have memory, but lithium iron phosphate batteries do not have this phenomenon. No matter what state the battery is in, it can be charged and used at any time, and it does not need to be discharged before charging.
fast charging
The energy conversion efficiency is high, and the charging can be completed within 1~3H.
Large capacity, large magnification
It has a larger capacity than ordinary batteries (lead-acid, etc.). The monomer capacity is 5AH-1000AH. High efficiency output: standard discharge is 2~5C, continuous high current discharge can reach 10C, and instantaneous pulse discharge (10S) can reach 20C;
The battery is over-discharged (even to 0V), and the battery will not leak or be damaged
Good waterproof performance and strong resistance
Environmentally friendly and pollution-free
Lithium iron phosphate battery does not contain any heavy metals and rare metals, non-toxic (SGS certified), non-polluting, in line with European RoHS regulations, and is an absolute green battery certificate.
To sum up, from the perspective of safety, lithium iron phosphate batteries are safe and stable, and no explosion incidents have occurred; in terms of battery life, the development of standardized, modularized, and integrated lithium iron phosphate battery systems is not inferior to Ternary lithium; in terms of service life, the lithium iron phosphate battery has a long life span, which can be the same as that of the whole vehicle; in terms of environmental adaptability, the lithium iron phosphate battery system has wide temperature adaptability and high protection level. It has obvious performance advantages in all aspects.
