Lithium-ion battery technology analysis, BYD is cheap and safe, Tesla expensive but efficient
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The core technology of new energy vehicles is to provide energy batteries, endurance and charging speed is the bottleneck of battery technology development to today, after more than 30 years of development, most of the energy of electric vehicles are provided by various lithium battery packs, but lithium batteries are still not fully mature, still in continuous exploration.
At present, the types of lithium batteries are lithium manganate, lithium iron phosphate, lithium titanate, lithium cobalt oxide, ternary materials, etc., due to energy performance and rare metal cost, lithium manganate, lithium titanate and lithium cobalt oxide have gradually become a niche choice, while lithium iron phosphate and ternary lithium batteries have been more widely promoted.
What are the characteristics of these two different lithium batteries and what is the difference between them? Which technical route have been adopted by new energy vehicle companies at present? Who of these two lithium batteries can have the last laugh? This article will explain each of them for you.
Ternary lithium battery and lithium iron phosphate battery
The full name of ternary lithium battery is “ternary material battery”, which generally refers to the lithium battery using lithium nickel cobalt manganate (Li (NiCoMn) O2, NCM) or nickel cobalt lithium aluminate (NCA) ternary cathode material, nickel salt, cobalt salt, manganese salt as three different component ratios for different adjustments, so it is called “ternary”, including many different proportions of batteries. From the shape, it can be divided into pouch batteries, cylindrical batteries and square hard shell batteries. Its nominal voltage can reach 3.6-3.8V, high energy density, high voltage platform, high tapped density, long cruising range, large output power, poor high temperature stability, but excellent low temperature performance and relatively high cost.
Lithium iron phosphate battery is the use of lithium iron phosphate (LiFePO4) as the cathode material, the use of iron as battery raw materials is low cost, the second does not contain heavy metals, less environmental pollution, working voltage of 3.2V. The P-O bond in the lithium iron phosphate crystal is stable, so there will be no leakage when stored at zero voltage, the safety is very high under high temperature conditions or overcharge, fast charging, high discharge power, no memory effect, high cycle life, the disadvantage is poor low temperature performance, the positive electrode material is small in tapped density, the energy density is low, and the yield and consistency of the product are also questioned.
Both types of batteries have their own strengths
Under high temperature conditions, the ternary material of the ternary lithium battery will decompose at 200 °C, produce a violent chemical reaction, release oxygen atoms, and under the action of high temperature, it is very easy to burn or explode, so based on safety considerations, China’s Ministry of Industry and Information Technology in January 2016, through special regulations to temporarily limit the use of ternary lithium batteries outside pure electric buses. The decomposition temperature of lithium phosphate batteries is 800 °C, which is less likely to catch fire and has relatively high safety.
(Source: Haitong Securities’ “New Energy Vehicle Industry Chain Series In-depth Report”)
Under low temperature conditions (the temperature is below -10 °C), the lithium phosphate battery decays very quickly, and after less than 100 charge and discharge cycles, the battery capacity will drop to 20% of the initial capacity, which is basically insulated from the use of cold areas; The ternary lithium battery has excellent low temperature performance, can maintain normal battery capacity under the condition of -30 °C, and is more suitable for the use conditions in the northern low temperature area.
From the perspective of manufacturing costs, the cobalt elements necessary for ternary lithium batteries are less in reserves, most of which rely on overseas imports, and are very affected by market fluctuations, so the cost of ternary lithium batteries is bound to remain high, and the raw materials required for lithium iron phosphate batteries do not need to be imported, the supply is sufficient, the price is stable, and the cost is relatively low.
Under experimental conditions, the remaining capacity of lithium iron phosphate battery is 84% after 5000 cycles, and more than 80% of the initial capacity can be maintained after 5 000 cycles of 1 C. After 3900 cycles of ternary lithium battery, the remaining capacity is only 66%, and after 2500 cycles of 1C, it drops to 80% of the initial capacity. In comparison, the cycle life of lithium phosphate batteries is much greater than that of ternary lithium batteries. In addition, the energy density of lithium iron phosphate battery is 120Wh/kg, which has basically reached the theoretical extreme, while the energy density of ternary battery is 180Wh/kg, and there is still a lot of room for improvement in the future.
The technical route selection of battery manufacturing enterprises and electric vehicle companies
According to the data from January to April 2016, domestic shipments of lithium iron phosphate batteries can account for 75.3% of the total market, which can be said to be the mainstream technical form, while the proportion of ternary lithium batteries only accounts for 22.6%, but the year-on-year growth rate has reached 3.47 times, and the development is very rapid.
Japan’s Panasonic, South Korea’s LG Chem, Samsung SDI, etc. use ternary lithium battery technology route, such as new energy giant Tesla uses Panasonic’s nickel cobalt aluminum oxide ternary lithium battery, is the so-called NCA, in Model S and Model X is Panasonic 18650 battery pack, and the latest MODEL 3 uses a larger capacity 21700 cylindrical battery pack.
Domestic new energy vehicle companies in the early days of the cost problem, most of the use of lithium iron phosphate batteries as energy sources, such as BYD and other enterprises for the main manufacturers of lithium iron phosphate batteries, launched Qin, Tang, Song and many other star products, and now due to the improvement of the country’s subsidy standards such as cruising range, the market share of ternary lithium batteries is gradually increasing.
Who can have the last laugh with ternary lithium batteries and lithium iron phosphate batteries?
(Source: IIT, a well-known research institute for lithium batteries in Japan)
The domestic debate about ternary lithium batteries and lithium phosphate batteries is very fierce, who will become the mainstream of future technology? At present, each manufacturer is exploring two different paths. The risk of leakage, deformation, combustion and explosion of ternary lithium battery power battery can not be ignored, but at present, new energy companies are working the battery management system (such as overcharge protection OVP, overdischarge protection UVP, overtemperature protection OTP, overcurrent protection OCP, etc.), and also use high-strength aluminum alloy protection structure, and many battery manufacturers have added silicon titanium nanotubes, solvent-free PI binders, solid electrolytes and other technical routes to the cathode material to make good achievements, greatly reducing risks and costs.
As a leading battery production enterprise, BYD has been adhering to the technical route of lithium iron phosphate batteries, and even began to add manganese elements to lithium iron phosphate batteries, exploring lithium iron manganese phosphate batteries, breaking through the original energy density restrictions, and cost control is also very good, but it poses new challenges to charging time.
Higher safety and greater energy density are two sides that enterprises and researchers need to pursue at the same time, from the perspective of the development needs of new energy vehicles, ternary lithium batteries will achieve a certain upper hand in the future competition after gradually solving safety, with greater energy density.
In the competition with lithium iron phosphate batteries, the safety of ternary lithium batteries needs to be improved, which is always the shadow of Panhuan in the minds of automobile companies, and even technology-leading products such as Tesla Model X have also had many accidents in battery pack fire and combustion at home and abroad. But in the long run, ternary lithium battery has the characteristics of lithium iron phosphate battery incomparable high energy density, low temperature resistance, etc., in the future of new energy vehicle development, ternary lithium battery will completely replace the current market position of lithium iron phosphate after solving the safety and cost problems, will become the general trend of the new energy market, this war will be known within three years at the earliest, let’s wait and see!
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(Source: Haitong Securities’ “New Energy Vehicle Industry Chain Series In-depth Report”)
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