What is a soft pack battery? How much can it develop?

On March 19, the 14th China International Battery Technology Exchange Conference (CIBF) was officially held in Shenzhen. During the conference, industry professionals had in-depth exchanges on battery industry chain technology innovation and supply chain market prospects. Among them, there was a type of battery that consumers were not very familiar with, which was mentioned by many experts, and it was the soft-pack battery.

New energy vehicles are developing rapidly. If you have some knowledge of the dynamics of the power battery industry in recent years, you will find that there are many types of power batteries. According to the different chemical compositions, ternary lithium batteries, lithium iron phosphate batteries, and nickel-metal hydride batteries can be distinguished; from the perspective of the battery technology promoted by car companies, there are blade batteries and magazine batteries; and there are 18650 and 4680 batteries named after the battery size. So what is the soft pack battery that was proposed by many experts at the time?

Soft pack battery, so powerful!

Soft-pack batteries, as the name suggests, are batteries that use soft packaging. The biggest difference between this type of battery and conventional cylindrical batteries and square batteries is that the former uses an aluminum-plastic composite film shell, while the latter two use metal shells. As for the four core battery materials, positive electrode, negative electrode, diaphragm and electrolyte, the difference between them is not that big.

Soft-pack batteries were first developed by Sony in 1990 and were used in automobiles in 1998. It can be seen that soft-pack batteries are not new high-tech technologies. They have a history of more than 20 years in the automotive field. In addition to their long history, soft-pack batteries also have four major advantages: high safety, high energy, high flexibility, and low internal resistance.

The successive launch of blade batteries and magazine batteries shows that the current development of power batteries focuses on safety, and soft-pack batteries also have their own unique advantages in terms of safety. Lithium iron phosphate batteries are already known for their safety, and both lithium phosphate batteries and ternary lithium batteries can be made into soft-pack batteries, so the difference in safety between the two will not be discussed for the time being.

In order to prevent the battery from being damaged in extreme situations, battery manufacturers usually use a hard shell to wrap the ternary lithium battery that is prone to thermal runaway, such as the Ningde Times NCM811 ternary lithium battery that was "not pierced by a needle". The same is true for the current magazine battery built on the basis of ternary lithium batteries, except that it prevents the spread of thermal runaway by designing a firewall to block high temperature for each single cell.

Unlike the "blocking" method commonly used by conventional ternary lithium batteries on the market to deal with thermal runaway, the method used by soft-pack batteries to deal with thermal runaway is "loosening". Under the same material system, since the ternary soft-pack battery uses a soft aluminum-plastic film packaging instead of a hard shell, it can release heat through inflation when it is in thermal runaway, providing a buffer space for the battery cell. Even in extreme cases, the soft-pack battery will only smoke or catch fire, and will not explode.

Before analyzing the advantages of soft-pack battery energy density, we can first break down the unit of energy density "Wh/kg". From the unit "Wh/kg", we can see that the energy density of the battery is not only strongly related to the battery capacity, but also closely related to the battery quality. The biggest advantage of soft-pack battery in energy density is its lightness.

Compared with conventional ternary lithium batteries, ternary soft-pack batteries save a thick outer shell, so they are 20% lighter than aluminum-shell ternary lithium batteries of the same capacity, and 40% lighter than steel-shell batteries. This means that even if the same battery cell is used, the energy density of ternary soft-pack batteries will be 40% higher than that of steel-shell ternary lithium batteries. At present, most domestic battery companies that have exceeded the 300Wh/kg mark in energy density use soft-pack batteries.

Also, because the soft-pack battery omits the hard outer shell of the conventional power battery, the soft-pack battery has the advantages of high flexibility and adjustable size. During the manufacturing stage, it is like a piece of plasticine that can be kneaded and flattened at will, which can meet the differentiated needs of different OEMs. In addition, compared with conventional power batteries, soft-pack batteries have the advantages of good chemical properties and long life. The chemical characteristics of low internal resistance of soft-pack batteries can greatly reduce the self-consumption of the battery and extend the cycle life of the battery.

As we all know, among the two mainstream power batteries currently, conventional ternary lithium batteries have high energy density but are not safe; conventional lithium iron phosphate batteries are safe but have low energy density; soft-pack batteries have high energy density and are also safe, so why have they become such a mess that neither grandmas nor uncles love them?

Soft packaging makes you successful, but also makes you fail

Xiao Lei believes that there are both objective and subjective reasons why soft-pack batteries are doing so poorly despite having all kinds of advantages.

The subjective reason why soft-pack batteries are unpopular is due to their "soft-pack" structure, just like their many advantages. The soft-pack structure allows them to deflate in time when thermal runaway occurs, can increase energy density by reducing weight, and can even be shaped and flattened at will during manufacturing; however, these advantages of soft-pack batteries also become their disadvantages.

Soft-pack batteries can be rounded or flattened, which means that their product consistency is poor and the manufacturing cost is high; they can release heat by venting in time when thermal runaway occurs, which means that they are prone to leakage and bloating; without a hard shell, it requires an additional shell when grouped, and the PACK process is highly complex. Although Chairman Mao once said that "the merits do not make up for the faults, and the faults do not cover the merits", these defects of soft-pack batteries at this stage can indeed make up for all its advantages in the minds of consumers.

In addition to the subjective problems mentioned above, there are also many objective problems that have prevented soft-pack batteries from developing smoothly in China. As we mentioned earlier, soft-pack batteries are already a long-standing product in the field of power batteries, but Xiao Lei believes that they are a bit out of time.

Soft-pack batteries were first used in cars 20 years ago, and between 2000 and 2010, most people had no idea about new energy vehicles. Due to the limitations of industry development, soft-pack power batteries were not very popular in people's eyes.

When the development of new energy vehicles was on the right track, Tesla's 18650 cylindrical battery had already become popular worldwide, while in the domestic market, lithium iron phosphate batteries led by BYD and the later rising CATL ternary lithium battery dominated the market. In the situation where the three giants divided the world into three parts, the soft-pack battery that got up early could not catch up with the latecomers, and it can even be said that it had no foothold at all.

Since soft-pack batteries are not popular in China, there were not many suppliers researching soft-pack batteries in China before, and the entire industry chain was not large. The suppliers of soft-pack batteries are mainly Japanese and Korean companies. Previously, the power batteries produced by Japanese and Korean companies could not obtain China's new energy vehicle subsidies, so their soft-pack batteries did not enter the Chinese market at all, which is also an important reason affecting the development of soft-pack batteries in China.

Summary: Soft-pack batteries may take one third of the market

Since the development of conventional ternary lithium batteries and lithium iron phosphate batteries has encountered difficult-to-break technical bottlenecks, and solid-state battery and graphene battery technologies are not yet mature. Although the installed capacity of soft-pack batteries in China is not high at present, this is mainly because it was born at the wrong time. Combined with its own advantages and the current status of power battery development, if soft-pack batteries can break through their own technical bottlenecks as soon as possible, then they may emerge as a dark horse with their own advantages.

Xiao Lei's opinion is not groundless, because China's new energy subsidy policy has lifted restrictions on Japanese and Korean batteries, so Japanese and Korean batteries with advanced soft-pack battery technology will enter the Chinese market unimpeded. Competition brings pressure, and pressure brings motivation. In fact, after soft-pack batteries have gradually been recognized by car companies, domestic battery manufacturers have also joined the research and development of soft-pack batteries. It can be seen that soft-pack batteries still have good development prospects.