What is the difference between a lithium-ion battery and a lithium metal battery?
Recently, SES (formerly SolidEnergySystems) announced the Apollo™ hybrid lithium metal battery at an online event. The Apollo™ hybrid lithium metal battery has a capacity of 107Ah and weighs only 0.982Kg, making it the largest single lithium metal battery in the world.
Its energy density also reached 417Wh/kg and 935Wh/L. This lithium-metal battery also showed high capacity and energy density in third-party discharge tests.
Typically, lithium-ion battery use graphite or silicon as the anode. A hybrid lithium metal battery, however, uses lithium metal as its anode.
SES said it has signed A joint development agreement with GM and Hyundai to develop a model A of lithium metal battery , which will be rolled out next year and ready for mass production by 2025.
This is actually only the second attempt to commercialize a lithium metal battery using a liquid electrolyte.
Route:hybrid lithium metal battery
Exploration of liquid electrolyte and solid electrolyte
Solid-state batteries are the most hotly touted next-generation batteries. Solid battery is a lithium battery with a solid battery electrolyte. One of the reasons for using a solid electrolyte is to use a lithium metal anode to dramatically increase energy density.
The first commercial attempts at lithium metal batteries used a liquid electrolyte.
In 1985, Moli Energy, a Canadian company, installed the first commercial use of lithium metal battery in the Mobile phone, but within six months launched a global recall due to a series of explosions.
After scientists failed to make a breakthrough in lithium metal battery using liquid electrolytes, people turned to solid-state electrolyte solutions.
Although the idea of solid electrolyte can effectively solve the problem of lithium dendrite, the low ionic conductivity has become another development bottleneck.
The application of lithium metal anode in secondary battery is in trouble.
The emergence of high concentration electrolyte
If we take the previous exploration of liquid electrolyte and solid electrolyte as the first two stages of anode application of lithium metal battery, the third stage will be entered around 2014, when the emergence of high concentration electrolyte.
Generally electrolytes have two materials, namely salt and solvent. Conventional electrolytes have a lot of solvents and very little salt. The solvent itself is carbonate, which is an organic flammable and flammable material. Most of the electrolyte is flammable and therefore unsafe.
A high concentration electrolyte, on the other hand, has a lot of salt and little solvent.
SES’s own electrolyte does two things: it is not flammable and it improves the shape of lithium dendrites.
According to SES, they use an electrolyte with a high concentration of solvent in salt, an electrolyte with more salt and less solvent. There are only a few drops of solvent, and the solvent is an inorganic solvent, it’s not flammable. And the salt is not regular lithium hexafluorophosphate, it’s a new salt with its own recipe.
That is, the electrolyte is still liquid, but the liquid itself is no longer flammable.
Their electrolyte also improved the shape of lithium dendrites.
With a conventional electrolyte, the lithium dendrites are very sharp, very fluffy shapes, and the lithium dendrites can break through the membrane and cause the lithium metal battery to short out and explode.
With SES’s new electrolyte, lithium dendrites still form, but their shape is completely changed, a very round, dense, flat shape. That way you don’t puncture the diaphragm and cause a short circuit.”
In addition, they have a protective coating on top of the anode, which makes the lithium dendrite very dense and then compacts it. SES draws on the idea of solid electrolyte.
Dendrite problems still exist even if they are not sharp or even flattened. So they use a third approach, software monitoring. They developed a software monitoring platform, monitor lithium metal battery safety 24 hours a day, and predict the development status of batteries in advance according to the use condition, and take the initiative to deal with potential dangers of batteries.
Four core technologies of hybrid lithium metal battery
The SES lithium metal battery has a total of four core technologies The first is the material, that is, the electrolyte, the formula and the solvent inside the electrolyte are completely developed by themselves, not flammable, more safe. It’s also a very stable liquid with lithium metal.
The second is lithium metal itself. Although lithium metal is purchased, it is a great challenge to make an ultra-thin and ultra-wide lithium foil and lithium belt. SES is working with a number of suppliers to develop the process.
The third is cell manufacturing, with SES producing its own cells. Lithium metal battery is similar to lithium ion battery, but there are many differences. This part is also their core technology.
The fourth is software. SES starts from cell production, quality control of raw materials and data collection during the whole process of production. The software monitors the performance of each cell with great accuracy and predicts risk, up to a month in advance.
The hybrid lithium metal battery combines the high energy density of lithium metal with the high manufacturing performance of lithium ions to play to their respective strengths.
Advantages: lithium metal battery has significantly higher energy density
Lithium metal battery has Similar performance to lithium ion battery , but significantly higher energy density.
High energy density
In the case of using the same cathode as lithium ion battery, the application of lithium metal anode can significantly improve the energy density of the lithium metal battery. According to SES, the Apollo™ battery has an energy density of 417Wh/ Kg and 935Wh/L.
400Wh/kg is the starting point for lithium metal battery energy density, and they will continue to optimize it to 480Wh/kg or even 500Wh/kg depending on demand in the future.That’s far more than the energy density of lithium-ion batteries currently on the market.
What about safety, low temperature performance and life span?
Better safety performance
Perhaps because ApolloTM had just been built, there wasn’t much test data. They have so far only given discharge tests in three environments, 10-hour discharge, 3-hour discharge and 1-hour discharge. From the data, the energy density and the volume are very close.
SES gave more of their previous 4Ah small cell data for reference.
According to a third party test, their small cell can pass the needle, overcharge, external short circuit and high temperature test. In SES’s words, lithium metal battery can achieve similar safety performance as lithium ion battery.
Better low temperature performance
They also tested for C-rate and low temperature performance. These tests for lithium metal battery showed that it maintained a very high energy density from 40 degrees to minus 30 degrees, from a very slow discharge — 10 hours — to a very fast discharge — less than 10 minutes.
A small cell can charge up to 4C and discharge up to 10C.
Lithium metal battery can also be charged quickly. Third-party tests show that their lithium metal battery goes from 10 percent to 90 percent charge in just 12 minutes.
Long life span
In terms of life span, SES data shows that the 3/4 layer 250mAh lithium metal battery can achieve 80% battery capacity retention rate after 800 cycles, and the 25+ layer 4.2Ah lithium metal battery can achieve 90% capacity retention rate after 550 cycles.
The whole manufacturing process and industry chain of lithium metal battery is very similar to lithium-ion battery. 60% of the process can be shared, but there is a big difference in the production of the anode.Lithium metal cells can be produced very well.
In terms of cathode material, the cathode material of lithium ion battery is used according to the needs of automobile companies, which can be made into ternary and lithium iron phosphate. Therefore, the performance of mixed lithium metal battery is very similar to that of lithium ion battery.
Progress in lithium metal battery : next year A sample, 2025 mass production
SES is working with General Motors and Hyundai Motor to launch A sample of lithium metal battery for vehicles next year.They plan to launch A sample in 2022, B sample in 2023, C sample in 2024, and get on the bus around 2025 for mass production.
SES is building the Shanghai Gigafactory, scheduled for completion in 2023, with a total area of 30,000 square meters. The Gigafactory, located in Shanghai’s Jiading International Automobile City, will have a capacity of 1GWh, making it the largest lithium metal battery plant in the world.
By 2025, SES will build joint venture plants with auto companies. The target is to start construction of 10GWh plants in 2025 and further increase the annual capacity to 30GWh by 2028.
For the layout of the production base, it is to take the principle of nearest to the car enterprise.
In SES’s view, the battery industry chain has three steps. First, material development, the United States has the advantage;
Second, cell product development and production engineering development, which must be placed in China and South Korea, benefiting from the industrial chain advantages of China and South Korea;
The third is production. Generally speaking, production should be close to the car company. For example, CATL sets up a factory in Germany mainly to serve German car companies. LG and SK set up factories in the United States mainly to serve American car companies.
“If we were to serve American automakers, build factories in the United States, serve Asian automakers in Asia, and serve European automakers in Europe.”
For hybrid lithium-metal batteries, ses is confident. SES doesn’t care if it’s a solid battery or a hybrid battery. The only thing they care about is data, data that is truly repeatable.Solid-state battery, which they have tried before, is not nearly as good as hybrid lithium metal battery in terms of performance and productivity, which is why they chose hybrid lithium metal battey.
It should be emphasized again that at present SES provides more data from the small 4Ah cell, and the large 100Ah cell will not reveal more data until next year at the earliest.
Moreover, as A brand new product, hybrid lithium metal battey has to go from A sample to mass production, and has to overcome the major hurdles of mass production, vehicle matching test and verification, and real car application. Let’s wait and see if it can be successfully mass-produced and loaded.