Calculation of energy density of lithium battery and metal lithium for dry goods series of lithium battery

How important is the energy density of a pure electric vehicle battery?

This seems to be like discussing how important the beating of the heart is to the human body. For a pure electric car, or a more standard one, the performance, range and reliability of a battery-powered car depend on the battery pack. The number of batteries and the energy density in a single cell. This formula is easy to understand: total power = number of batteries × energy density of a single cell.

The structural design of modern cars is actually very rigid, leaving only a little space for the battery pack. Most models are concentrated under the cockpit floor. Of course, this is also due to safety and space considerations.

Therefore, the number of batteries has been limited to a certain range and cannot be increased significantly. If you want to enhance the performance of the battery car, you can only make a fuss about the energy density.

First of all, what is battery energy density?

Energy density refers to the amount of energy stored in a certain space or mass matter. The energy density of a battery is the electric energy released by the average unit volume or mass of the battery. Battery energy density=battery capacity×discharge platform/battery thickness/battery width/battery length, the basic unit is Wh/kg (watt hour/kg).

The greater the energy density of the battery, the more electricity stored per unit volume.

△Cylindrical lithium battery structure diagram

Regarding battery energy density, now we all know that it is the most obvious breakthrough in the current battery industry, even the electric vehicle industry, but it is really difficult to break through it!

△Proportion of inactive materials (except leads, etc.) in a typical battery design

It is reported that the energy density of the battery is basically determined by the positive and negative electrodes of the battery, but only the positive and negative active materials cannot guarantee that the battery can be powered on. There must be a lot of inactive materials, such as conductive auxiliary agents and the adhesion between active powders. Bonding agent, isolation film, anode and cathode foil, insulating and fixing adhesive tape, aluminum plastic film shell or steel aluminum shell, etc.

Most of us always ignore the content of this part of the substance intentionally or unintentionally, and the energy density obtained is quite different from the facts, misleading the people who eat melons. In fact, this part is quite important. Taking the technological progress of the past ten years as an example, the increase in battery energy density is mainly achieved by the increase in the proportion of active materials.

△Change and prediction of energy density

There is also an increase in the size of the original battery to achieve the effect of capacity expansion.

The most familiar example is that Tesla, a well-known electric car company that was the first to use Panasonic's 18650 battery, will replace it with a new 21700 battery. The reason is not that the 18650 battery has any quality problems. It is just that the capacity of a single 18650 battery is small, generally around 2-4Ah. There are too many series and parallel connections, and the probability of monomer failure is high, which causes its application in the field of electric vehicles to be affected. limit.

△The picture shows the 21700 battery

The 21700 battery is larger in size than the 18650 battery (18mm in diameter and 65mm in length), reaching a diameter of 21mm and a length of 70mm. If you want to think about this problem more vividly, we might as well take a look at the calculations from Hitech Energy, which only considers the dense accumulation of monomers. It can be seen that the volume of 30 pieces of 21700 is 1.1 times the volume of 40 pieces of 18650, and the mass is 0.97 times.

Under the same energy, the number of batteries required can be reduced by about 1/3, and the number of metal connections inside the battery pack is reduced, thereby further reducing the weight of the battery pack, and the energy density of the vehicle will be partially increased, reaching close to 300kw/kg.

The following three points are particularly noticeable:

1. By 2020, the specific energy of lithium-ion power battery cells will be greater than 300Wh/kg; the specific energy of the system will reach 260Wh/kg; the cost will be less than 1 yuan/watt-hour; the use environment will reach -30℃ to 55℃; it has 3C charging capacity .

2. By 2025, the specific energy of the monomer will reach 500Wh/kg.

3. Strive to realize the industrialization and vehicle application of lithium-ion battery products with a single battery of 350Wh/kg and a system of 260Wh/kg.

A few days ago, Aoyang Shunchang (002245) disclosed in the 2018 semi-annual report that Tianpeng Power has completed the technical reserve of 18650 3.5AH products in terms of high nickel NCA product reserves, and can put into production according to the requirements of electric vehicle customers. The system energy density exceeds 160Wh. /kg of high energy density battery.

BAK, the leading company in the ternary column, also stated that the company’s 3.0Ah 18650 power cell has been equipped with a new A00-class SUV model of JAC Volkswagen.

It is clear that with the improvement of 18650 power cell automation and intelligent production level and downstream car companies' demand for high-energy density batteries, 18650 battery companies are moving towards high-capacity cell products above 3.0AH.

According to statistics from the Advanced Institute of Technology, Industry and Research Lithium Battery (GGII), there are currently more than 20 domestic companies that have mass-produced 18650 power cells. However, due to factors such as capital, technology, production capacity, technology, equipment, etc., there are not many companies that can finally mass produce 18650 power cells above 2.6AH.

From the perspective of production capacity, Gaogong Lithium Battery has counted 6 18650 battery companies with better technology and market reputation, including BAK, Yiwei Lithium Energy, Zhihang New Energy, Far East Foster, Tianpeng Power, and Lishen. Gram ranks first with 6GWh production capacity. Although Lishen's production capacity is not high, it is learned from its insiders that the current supply of the company's 18650 is in short supply and production capacity is tight.

If measured by technology, the chief engineer of a domestic cylindrical battery company said that the domestic 18650 power battery is still the main benchmark against Panasonic, and its 18650 above 3.0AH has been actually applied to Tesla, but stable mass production of 2.8-2.9Ah18650 in the country Become a threshold for battery companies.

At present, 2.4-2.6Ah capacity battery products are the mainstream products in the current new energy vehicle market, and they are also the most competitive products of domestic cylindrical battery companies.

As the most mature power battery technology route for production technology, 18650 batteries have the advantages of short delivery cycle and uniform size standards. Especially for car companies, the biggest advantage is that the number of cylindrical battery companies with satisfactory domestic production capacity and high cost performance is relatively large. There are many options, wide selection, and convenient switching.

However, in order to meet the demand of downstream customers for high energy density of power batteries, the high capacity of 18650 is an inevitable trend of future development. Although the 21700 has been replaced by a trend, from the current point of view, there are only a handful of domestic companies that can stabilize the mass production of the 21700, and the 18650 will remain in the mainstream for at least 1-2 years.

So, what are the difficulties for battery companies to upgrade from 2.6Ah to 3.0AH or even higher 18650 cells?

The consensus of many battery companies, including BAK, Lishen, Far East Foster, and Yiwei Lithium Energy, is:

First of all, high capacity must start from the material side, importing high nickel or even with silicon carbon and other materials, battery companies need to overcome difficulties such as high nickel cathodes that are sensitive to the application environment and moisture. The slowdown in the application of silicon carbon in the power market this year is also related to the slower advancement of battery companies in technology. Secondly, after having the experimental level, the biggest bottleneck lies in how to achieve large-scale mass production and truly realize the application of truck loading.

Both of these two major difficulties place higher requirements on the equipment, process and technology of 18650 battery companies. Gaogong Lithium Battery hereby sorts out the layout of 7 18650 battery companies in BAK, Lishen, Tianpeng Power, Far East Foster, Penghui Energy, Zhihang New Energy, and Zhuoneng New Energy in high-capacity battery cell products. A glimpse of the domestic 18650 battery technology level.

➤BAK: 3.0Ah18650 batteries supporting A0-class SUV models

In mid-August, BAK Battery announced on its official microblog that the company will provide supporting products for the E20X, the first A0-class SUV model of JAC Volkswagen SOL (Sihao), which uses a 3.0Ah 18650 ternary power cell, and the battery pack also uses liquid The cold battery safety control technology has a maximum cruising range of 301km under working conditions and a maximum speed of 130km/h. It is expected to be officially launched in September.

On July 12, Geely Global Hawk announced the release of the latest pure electric model EX3 in Shanghai. There are 3 versions of this model, equipped with BAK 186502.75Ah high-energy lithium battery with a battery capacity of 41.5kWh and a maximum cruising range of 380KM.

➤Lishen: The first domestic cylindrical enterprise with 21700 application loading

Lishen is currently the first domestic power battery company to mass-produce 21700 and apply it to passenger cars. As a veteran 18650 battery company in China, Lishen has a total production capacity of 1GWh18650 batteries, all of which are automated and intelligent production, which can meet the production needs of car companies with high capacity batteries above 2500mAh.

➤Tianpeng power supply: NCA system 18650 battery loading

At the roadshow of Aoyang Shunchang 2017 Performance Report on March 12 this year, Chen Xuan, general manager of Tianpeng Power, said: "In 2017, Tianpeng Power’s performance in the field of power tool batteries and EV batteries has reached 1:1. , In the EV field, it is mainly positioned in the mini passenger car market, and has established cooperation with SAIC-GM-Wuling, Zhidou, Kangdi, Zotye and other car companies."

For example, SAIC-GM-Wuling’s explosive model Baojun E100 and the new upgraded version of Baojun E200 are equipped with Tianpeng power supply NCA system 18650 batteries. Among them, Baojun E100 ranked sixth among the top ten best-selling models of domestic new energy A00-class passenger vehicles with a sales volume of 7,972 units from January to May this year.

➤Far East Foster: 3100mAh power battery enters pilot test

Far East Foster has been deeply engaged in 18650 ternary lithium batteries for many years, and has 18650-2400mAh, 2600mAh, 2800mAh, 3100mAh and other types of products. It is expected that NCM811 high-capacity batteries will be put into production in 2019. Among them, the 2600-2900mAh18650 products produced by Far East Foster have begun to use high nickel 811 materials, and a small amount of shipments have been made in 2017, and mass shipments have been achieved in March this year.

At the beginning of August, Smart Energy (600869) stated that the cylindrical 18650-3100mAh power cell of its wholly-owned subsidiary, Far East Foster, has now entered the pilot test stage.

➤Penghui Energy: Mainly 2800mAh18650 power battery

In June, Liu Jiansheng, Dean of Penghui Energy and Power Research Institute, revealed to Gaogong Lithium that starting from April this year, the company’s new capacity for power cylindrical batteries will be NCM811, mainly with a capacity of 2800mAh, using 811 with a graphite anode solution. It has a density of 220Wh/kg and is currently mainly supplied to SAIC-GM-Wuling. The company is also stepping up the mass production of 3000mAh 18650 batteries in the NCM811 system, and the progress of NCM811 with 3300mAh silicon carbon batteries.

➤Zhihang New Energy: 3000mAh18650 battery passed the new national standard strong inspection

According to data from the Advanced Industry Research Institute of Lithium Battery (GGII), Zhihang New Energy ranked 10th in the ranking of power battery installed capacity in the first half of 2018. In the high-tech lithium battery 2018 power battery supply chain tour in May, Zhihang New Energy stated that the company focuses on the ternary technology route, and its main product is 18650-2600mAh ternary batteries, with a specific energy of 210wh/kg. The new high-energy density 3000mAh product has completed the pilot test and has passed the new national standard mandatory inspection. The company has a complete production line of ternary cathode materials, batteries and PACK systems, and currently has a total production capacity of 3.5GWh.

➤Zhuoneng New Energy: Mainly pushing 2800mAh and higher capacity batteries

At present, Zhuoneng New Energy has two production bases in Shenzhen and Guangxi, with a daily production capacity of 1.6 million batteries, both of which are actual production capacity. Among them, the Shenzhen base produces 600,000 units per day, mainly 3C consumer batteries; the Guangxi base produces 1 million units per day, mainly power batteries.

Last year, Zhuoneng New Energy's main power battery model was 2600mAh. This year, it will mainly push 2800mAh and higher capacity batteries in the power battery market, and it has entered the stage of mass supply.