Is the restart of lithium iron phosphate batteries a technological "retreat" or a "concession" of capital?

When new energy vehicles first entered the market, the most obvious difference between imported and domestic pure electric models was the battery life. Due to technical and cost issues, domestic brands generally chose lithium iron phosphate power batteries. The benchmark battery life of 150 kilometers at that time, coupled with severe low-temperature attenuation and the difficulty in finding charging networks, early car owners who dared to buy pure electric models were absolutely "brave".

At that time, a complaint from a taxi driver in the suburbs of Beijing left a deep impression on "E Car Hui": "This car can only run 120 kilometers in the summer with air conditioning, and only 60 kilometers in the winter without air conditioning. It can't even do the work of a motorcycle taxi." Because of this, even with strong support from policies and subsidies, pure electric models are still not popular. On the other hand, the Tesla Model S, which requires fuel indicators and costs over one million yuan, is very popular due to its long battery life and high topicality, and once became a "red man" in the eyes of parallel imports and second-hand car dealers.

Subsequently, in order to seek a breakthrough in driving range, domestic brands have turned their attention to ternary lithium batteries. BYD and Denza, staunch supporters of lithium iron phosphate, eventually switched to ternary lithium batteries. According to relevant data, the installed capacity of ternary lithium batteries in 2016 was 6.3GWh, with a market share of 22.6%; by 2019, the installed capacity of ternary lithium batteries reached 38.5GWh, and the market share also climbed to 61.7%. However, just as the market share of lithium iron phosphate has been declining year by year, BYD and Tesla have successively announced that they will restart lithium iron phosphate batteries through "blade battery" technology and adopt "cobalt-free" batteries.

Is it the wrong direction? Lithium iron phosphate makes a comeback

As early as 2018, Tesla's Elon Musk said he wanted to achieve "cobalt-free" batteries, and recently it was reported that Tesla and CATL were discussing "cobalt-free" battery technology. Then BYD showed its latest blade battery and said that the BYD Han EV equipped with the new battery will soon be tested in the market.

First, let me briefly explain the love-hate relationship between lithium iron phosphate batteries and ternary lithium batteries. Endurance has always been a basic factor in evaluating pure electric vehicles. However, due to the limited layout space of power batteries, simply stacking batteries cannot completely solve the problem, so improving battery energy density has become a breakthrough direction. Coupled with the inclination of domestic subsidy policies, long endurance and high density have become the direction of technology convergence for car companies, and ternary lithium batteries have once become the core selling point of new cars.

In fact, the biggest difference between lithium iron phosphate and ternary lithium batteries lies in the difference in the positive electrode materials. The positive electrode material of lithium iron phosphate batteries is lithium iron phosphate, while the positive electrode material of ternary lithium batteries is nickel cobalt aluminum or nickel cobalt manganese. The advantage of ternary lithium batteries is high energy density, and the disadvantage is cost and safety hazards. At present, mainstream manufacturers have used technical means to increase the battery active temperature control system to control the risk of thermal runaway, but the cost of raw materials cannot be solved by technical means for the time being.

According to data from True Lithium Research, as of the end of 2019, the unit price of domestic ternary lithium battery packs was 1.05 yuan/Wh; the unit price of lithium iron phosphate battery packs was 0.8 yuan/Wh. Therefore, against the backdrop of a sharp decline in subsidies, lithium iron phosphate batteries have regained attention.

BYD's "razor blade" breaks the blockade of ternary lithium

While domestic passenger cars are generally equipped with ternary lithium batteries, lithium iron phosphate batteries still occupy nearly 40% of the market share, and their main contribution is in the commercial vehicle field with extremely high safety requirements. Although BYD compromised with ternary lithium batteries in passenger cars, it did not lose its own advantages in the commercial vehicle field.

Under the premise that the energy density of lithium iron phosphate batteries has not been broken through, BYD has made improvements in battery structure and battery pack design. The blade batteries are in a long strip shape and arranged side by side inside the power battery pack. The compact arrangement structure replaces the original crossbeam and longitudinal beam structure inside the power battery pack, and reduces unnecessary module shell structure, effectively improving the utilization rate of the internal space of the battery pack, thereby improving the overall battery pack energy density.

At the same time, blade batteries can not only be directly packaged into power battery modules, but also increase the contact area of ​​the temperature management system, improve cooling or heating performance, and reduce the additional loss of the temperature control system. At the same time, different models can be adapted to different models by simply changing the length of the blade battery, which enhances the adaptability of the blade battery.

Although ternary lithium batteries have strong expansion capabilities in terms of energy density, the high density brought by high activity also has high risks. Since 2019, spontaneous combustion caused by thermal runaway has increased significantly, and safety issues have gradually become the focus. Recently, BYD has demonstrated the different performances of ternary lithium batteries, lithium iron phosphate block batteries, and BYD blade batteries after being punctured by needles in response to safety issues.

When the steel needle pierces the power battery cell and causes a short circuit in the cell, the ternary lithium battery experiences a drastic temperature change, the surface temperature quickly exceeds 500°C, and extreme thermal runaway and violent combustion occurs. Although there is no open flame after the traditional lithium phosphate battery is pierced, it emits white smoke and the surface temperature reaches 200°C-400°C. After the blade battery is penetrated, there is no open flame or smoke, and the surface temperature of the battery is only 30°C-60°C. Ouyang Minggao, an academician of the Chinese Academy of Sciences, believes: "This is mainly due to the unique design characteristics of the blade battery, which makes it generate less heat and dissipate heat quickly during a short circuit." In addition, BYD's internal engineers revealed to "E Car Hui": "By 2021, the application of blade batteries will be popularized in both pure electric and plug-in hybrid models."

How Tesla is going "cobalt-free"

In addition to BYD, Tesla is also pursuing new batteries. In 2018, Tesla CEO Musk tweeted that Model 3 batteries contain less than 3% cobalt, and that the technology will be improved to completely abandon cobalt in the next generation of batteries. After Tesla announced the "cobalt-free" plan, cobalt stocks plummeted, and lithium iron phosphate-related stocks rose by the daily limit for many days.

In fact, the global price trend of cobalt materials has continued to rise since 2017. Tesla has seen its domestically produced Model 3 continue to sell well due to its price advantage. Since its domestic production, Tesla has been accelerating the localization of parts. As the core of cost, power batteries, Tesla has reached an agreement with CATL on the one hand, and is also exploring the feasibility of "cobalt-free" batteries on the other.

Although lithium iron phosphate has inherent advantages in terms of price and safety, there is not much room for improvement in its energy density. Tesla, which has won market attention with its high range, will certainly not give up its strength. In fact, Tesla is attracted by CATL's CTP module-free power battery pack technology.

In pure electric vehicles, the battery is not exposed and exists alone. It needs to be composed of many battery cells to form a battery module, and the battery capacity or battery voltage is increased by series and parallel connection. At the same time, it also needs to be equipped with a battery management system, temperature control device, protective shell, etc. All these extra weights need to spread the battery energy density.

Simply put, CATL's CTP module-free power battery pack technology removes the concept of battery modules and adopts a modular design to increase the full cabin rate of power batteries. On the one hand, it reduces the extra weight, and on the other hand, it increases the load capacity. At present, the energy density of the CTP lithium iron phosphate battery pack provided by CATL for Volkswagen's e-Delivery series of models has reached 160Wh/kg, so the energy density and endurance of lithium iron phosphate batteries are no longer a problem.

At present, the number of parts in CATL's CTP battery pack has been reduced by 40%, the volume utilization rate of CTP battery pack has been increased by 15%-20%, and the production efficiency has been increased by 50%, which can significantly reduce the manufacturing cost of power batteries. Therefore, Tesla has seen the possibility of applying "cobalt-free" battery packs to domestic models.

In the view of "E Car Hui", controlling battery costs has always been a breakthrough direction for car companies. As early as 2019, the iEV7L launched by JAC was equipped with lithium iron phosphate batteries to ensure that the terminal price was affordable enough. Now, under the premise that lithium iron phosphate battery technology has not yet made a significant breakthrough, CATL and BYD have improved the battery structure, optimized the unnecessary extra weight inside, and increased the overall battery pack energy density, while taking into account the cost and endurance requirements, so that lithium iron phosphate batteries can regain their competitiveness.