Technical Discussion | Our Next Energy's Sandwich Battery

BMW I Venture invested in Our Next Energy, a startup founded in 2020. The company, which raised a total of US$85 million, plans to invest US$1.6 billion in Michigan to build a local 20GWh lithium iron phosphate plant. I also took the time to sort out the technology route of this company.

From the overall design concept, this company focuses on lithium iron phosphate (LFP) and anode-free battery (AFB). The entire design concept is indeed a bit like CATL's AB battery.

The first battery (Aries) adopts what we know as "cell-to-pack", directly stacking and using lithium iron phosphate (LFP) in the battery pack to achieve higher system-level energy density.

The second technology, called the Gemini "high-energy battery pack," is used in conjunction with the first battery to extend driving range.

▲Figure 2. Two types of batteries: Aries and Gemini

Part 1. Product design ideas

The first generation of Aries batteries is mainly for commercial vehicles, with a battery capacity of 79kWh, dimensions of 1630*766*288mm, a system energy density of 144Wh/kg, 287Wh/L, and a group efficiency of 76%.

▲Figure 3. The first generation of lithium iron phosphate battery

The first generation of lithium iron batteries are mainly used in commercial vehicles and energy storage, and the overall design concept does not have any major features.

After BMW invested, the company also provided BMW with a set of batteries, mainly using Anode Free cells, with a volume energy density of 1007Wh/L. This is a 240Ah blade anode-free battery, which also uses a composite method due to its poor power characteristics.

▲Figure 5. The actual BMW iX

This design is for a 185kWh battery, in which two types of batteries are directly combined for use.

This is a combination of two different cycle characteristics. Since AFB has a relatively small number of cycles, the startup company is also aware of this. Therefore, when combining them, LFP is used as the main cycle battery and AFB is used as energy storage. This combined scheduling can optimize the entire cycle characteristics.

Note: Currently, everyone can make AFB with high energy density but very poor circulation. However, in order to solve the problem of poor circulation, a special system design is adopted here.

The method designed here is to use AFB and LFP alternately. The advantage here is that since the blade lithium iron phosphate battery has better thermal properties, it can withstand the spread of thermal runaway.

Since the overall energy density of this battery system is relatively high, DCDC is integrated into it.

The purpose here is that the blue part can use the pure LFP module as the main circulating product, and let the hybrid module be used as the energy supplement pack. Conceptually, it is an LMO Anode Free battery pack that can store energy but has a limited number of uses. This chemical system choice is very interesting and is also considered around cost.

Summary: I think this company has some ideas. Based on the actual characteristics of existing battery cells, they have made high-energy density batteries with limited cycles and poor safety. But they can still use them in cars after 200 cycles, which is really a lot of effort.