How important is the energy density of batteries in pure electric vehicles?
This is similar to discussing how important the heartbeat is to the human body. The performance, range, and reliability of a pure electric vehicle, or more precisely, a battery-powered vehicle, all depend on the number of batteries in its battery pack and the energy density of each individual battery cell. The formula is easy to understand: Total capacity = Number of batteries × Energy density of individual battery cells.
Modern cars have a rather rigid structural design, leaving very little space for the battery pack. In most models, the battery pack is located under the floor of the passenger compartment, which is, of course, for safety and space considerations.
Therefore, the number of batteries has been limited to a certain range and cannot be significantly increased. The only way to improve the performance of battery-powered vehicles is to focus on energy density.
First, what is battery energy density?
Energy density refers to the amount of energy stored in a given space or mass of matter. The energy density of a battery is the electrical energy released per unit volume or mass of the battery. Battery energy density = battery capacity × discharge plateau / battery thickness / battery width / battery length, with the basic unit being Wh/kg (watt-hours per kilogram).
The higher the energy density of a battery, the more electricity it can store per unit volume.
△Structure diagram of a cylindrical lithium battery
Regarding battery energy density, we now know that it is the most obvious breakthrough for the battery industry, and even the electric vehicle industry, to take a big leap forward. However, breaking through it is really difficult!
△Percentage of inactive materials (excluding leads, etc.) in a typical battery design
It is understood that the energy density of a battery is basically determined by the positive and negative electrodes. However, the positive and negative active materials alone cannot guarantee that the battery can generate electricity. There are also many inactive materials, such as conductive additives, binders between active powders, separators, foils for the anode and cathode, insulating adhesive tape, aluminum-plastic film shells or steel-aluminum shells, etc.
Most of us tend to overlook the content of this component, intentionally or unintentionally, leading to a significant discrepancy between the energy density we arrive at and the actual figures, thus misleading the public. In fact, this component is quite important. Take the technological advancements of the past decade or so, for example; the improvement in battery energy density has primarily been achieved through increasing the proportion of active materials.
△Changes and predictions of energy density
Another method is to increase the original battery size to achieve the effect of expanding the battery capacity.
The most familiar example is Tesla, the well-known electric vehicle company that was the first to use Panasonic 18650 batteries, which will now switch to the new 21700 batteries. The reason is not that there are any quality problems with 18650 batteries, but that the capacity of a single 18650 battery is small, generally around 2-4Ah, and the large number of batteries connected in series and parallel increases the probability of individual cell failure, which limits its application in the electric vehicle field.
△The image shows a 21700 battery.
The 21700 battery is larger in size than the 18650 battery (18mm in diameter, 65mm in length), measuring 21mm in diameter and 70mm in length. To illustrate this further, let's look at calculations from HitechEnergy, considering only the dense packing of individual cells. We can see that the volume of 30 21700 cells is 1.1 times that of 40 18650 cells, while their mass is 0.97 times greater.
With the same energy, the number of batteries required can be reduced by about one-third, and the number of metal connectors inside the battery pack is reduced, thereby further reducing the weight of the battery pack. The energy density of the whole vehicle will be partially improved, reaching close to 300kw/kg.
The following three points are particularly noteworthy:
1. By 2020, the specific energy of a single lithium-ion power battery cell should be greater than 300Wh/kg; the specific energy of the system should strive to reach 260Wh/kg; the cost should be less than 1 yuan/Wh; the operating environment should be between -30℃ and 55℃; and it should have 3C charging capability.
2. By 2025, the specific energy of a single unit will reach 500Wh/kg.
3. Strive to achieve the industrialization and vehicle application of lithium-ion battery products with a single cell capacity of 350Wh/kg and a system capacity of 260Wh/kg.
Recently, Aoyang Shunchang (002245) disclosed in its 2018 semi-annual report that Tianpeng Power has completed the technical reserves of 18650 model 3.5AH products in terms of high-nickel NCA product reserves, and can put into production high energy density batteries with system energy density exceeding 160Wh/kg according to the requirements of electric vehicle customers.
BAK, a leading manufacturer of ternary cylindrical batteries, also announced that its 3.0Ah 18650 power cells have been supplied to a new A00-class SUV model under JAC Volkswagen.
It is clear that with the improvement of automation and intelligent production levels of 18650 power cells and the demand of downstream automakers for high energy density batteries, 18650 battery companies are moving towards high-capacity cell products with capacities of 3.0AH and above.
According to data from GGII (Gaogong Industry Research Institute for Lithium Batteries), there are currently more than 20 companies in China capable of mass-producing 18650 power battery cells. However, due to factors such as funding, technology, production capacity, processes, and equipment, only a small number of these companies are ultimately able to mass-produce 18650 power battery cells with capacities of 2.6AH or higher.
In terms of production capacity, GGII (Gaogong Lithium Battery Research Institute) reviewed six 18650 battery companies with good technology and market reputation, including BAK, EVE Energy, Zhihang New Energy, Far East Foster, Tianpeng Power, and Lishen. They found that BAK ranks first with a production capacity of 6GWh. Although Lishen's production capacity is not high, according to its insiders, the company's 18650 batteries are currently in short supply and its production capacity is tight.
In terms of technology, the chief engineer of a domestic cylindrical battery company said that domestic 18650 power batteries are still mainly benchmarked against Panasonic. Panasonic's 18650 batteries with a capacity of 3.0Ah and above have been practically applied to Tesla. However, the stable mass production of 2.8-2.9Ah 18650 batteries in China has become a threshold for battery companies.
Currently, 2.4-2.6Ah capacity batteries are the mainstream products in the new energy vehicle market and are also among the most competitive products among domestic cylindrical battery manufacturers.
As the most mature power battery technology, 18650 cells have advantages such as short delivery cycles and standardized dimensions. For automakers in particular, the biggest advantage is that the domestic production capacity is sufficient, there are many cylindrical battery manufacturers with high cost performance, and there is a wide range of choices and convenient switching.
However, to meet the downstream customers' demand for high energy density power batteries, the high-capacity 18650 is an inevitable trend for future development. Although the 21700 is already showing signs of replacement, currently, there are only a handful of domestic companies that can stably mass-produce the 21700, and the 18650 will remain the mainstream for at least the next 1-2 years.
So, what are the main challenges for battery manufacturers in upgrading 18650 cells from 2.6Ah to 3.0Ah or even higher?
The consensus among many battery companies, including BAK, Lishen, Far East Foster, and EVE Energy, is:
First, high capacity requires a focus on materials, incorporating high-nickel materials or even silicon-carbon composites. Battery manufacturers need to overcome challenges such as the sensitivity of high-nickel cathodes to application environments and moisture. The slowdown in silicon-carbon applications in the power battery market this year is also related to the slower progress of battery manufacturers in process technology. Second, after achieving experimental capabilities, the biggest bottleneck lies in how to achieve large-scale mass production and truly realize vehicle applications.
These two major challenges place higher demands on the equipment, processes, and technologies of 18650 battery manufacturers. GGII (Gaogong Lithium Battery Research Institute) has compiled a list of the high-capacity cell product offerings of seven 18650 battery companies—BIK, Lishen, Tianpeng Power, Far East Foster, Penghui Energy, Zhihang New Energy, and Zhuoneng New Energy—to provide insight into the technological level of 18650 batteries in China.
➤ BAK: 3.0Ah 18650 battery cells for A0-class SUVs
In mid-August, BAK Battery announced on its official Weibo account that it would provide supporting products for the E20X, the first A0-class SUV model of the JAC Volkswagen SOL brand. The battery pack uses 3.0Ah 18650 ternary lithium battery cells and adopts liquid-cooled battery safety management technology. The maximum range under working conditions is 301km, and the top speed is 130km/h. It is expected to be officially launched in September.
On July 12, Geely Global Hawk announced the launch of its latest pure electric vehicle, the EX3, in Shanghai. The model comes in three versions and is equipped with a BAK 18650 2.75Ah high-energy lithium battery with a capacity of 41.5kWh and a maximum range of 380km.
➤Lishen: The first domestic cylindrical engine manufacturer to install 21700 in vehicles
Lishen is currently the first domestic company to mass-produce 21700 power batteries for use in passenger vehicles. As a long-established 18650 battery company in China, Lishen has a total production capacity of 1GWh of 18650 cells, all of which are produced in an automated and intelligent manner, capable of meeting the production needs of automakers for high-capacity cells of 2500mAh and above.
➤ Tianpeng Power: NCA system 18650 batteries installed in vehicles
At the 2017 performance report roadshow of Aoyang Shunchang on March 12 this year, Chen Xuan, general manager of Tianpeng Power, said: "In 2017, the performance ratio of Tianpeng Power in the field of power tool batteries and EV batteries has reached 1 : 1. In the EV field, we mainly target the micro passenger car market and have established cooperation with automakers such as SAIC-GM-Wuling, Zhidou, Kandi, and Zotye."
For example, SAIC-GM-Wuling's best-selling Baojun E100 and the newly upgraded Baojun E200 are both equipped with Tianpeng Power's NCA system 18650 batteries. Among them, the Baojun E100 ranked sixth among the top ten best-selling new energy A00-class passenger vehicles in China, with sales of 7,972 units from January to May this year.
➤ Far East Foster: 3100mAh power battery cells enter pilot production.
Far East Foster has been deeply involved in the 18650 ternary lithium battery industry for many years, offering a variety of models including 18650-2400mAh, 2600mAh, 2800mAh, and 3100mAh. High-capacity NCM811 cells are expected to enter production in 2019. Among these, Far East Foster's 2600-2900mAh 18650 products have already begun using high-nickel 811 materials, with small quantities shipped in 2017 and mass production commencing in March of this year.
In early August, Smart Energy (600869) announced that its wholly-owned subsidiary, Far East Foster, has entered the pilot production stage for its cylindrical 18650-3100mAh power battery cells.
➤Penghui Energy: Primarily featuring 2800mAh 18650 power battery cells
In June, Liu Jiansheng, Dean of the Penghui Energy Power Research Institute, revealed to GGII Lithium Battery that since April of this year, the company's new production capacity for cylindrical power batteries has all been NCM811, mainly with a capacity of 2800mAh. It uses an 811 battery paired with a graphite anode, achieving an energy density of 220Wh/kg. Currently, it primarily supplies batteries to SAIC-GM-Wuling. The company is also accelerating the mass production of 3000mAh 18650 cells based on the NCM811 system, as well as the progress on 3300mAh cells using NCM811 combined with silicon-carbon technology.
➤ Zhihang New Energy: 3000mAh 18650 battery passes new national standard mandatory testing
According to data from GGII (Gaogong Industry Research Institute for Lithium Batteries), Zhihang New Energy ranked 10th in power battery installations in the first half of 2018. During the GGII 2018 Power Battery Supply Chain Roadshow in May, Zhihang New Energy stated that the company focuses on ternary lithium battery technology, with its main products being 18650-2600mAh ternary batteries, achieving a single-cell specific energy of 210Wh/kg. A new 3000mAh product with even higher energy density has completed pilot testing and passed the new national standard's mandatory testing. The company possesses complete production lines for ternary cathode materials, cells, and PACK systems, with a current total capacity of 3.5GWh .
➤ Zhuoneng New Energy: Primarily promoting battery cells with capacities of 2800mAh and higher.
Currently, Zhuoneng New Energy has two major production bases in Shenzhen and Guangxi, with a daily production capacity of 1.6 million battery cells, both of which are actual production capacity. Among them, the Shenzhen base produces 600,000 cells per day, mainly for 3C consumer batteries; the Guangxi base produces 1 million cells per day, mainly for power batteries.
Last year, Zhuoneng New Energy's mainstream power battery model was the 2600mAh model. This year, it will mainly promote 2800mAh and higher capacity cells in the power battery market, and has already entered the mass supply stage.
