New General Motors Batteries Could Pave the Way to Second-Life Uses

In March 2020, General Motors (GM) held an event at its Warren, Michigan facility to provide the first public details on its upcoming third-generation EV architecture known internally as BEV3. GM showed off a dozen different vehicles using the BEV3 component set including the Cruise Origin robotaxi that was unveiled in January 2020. The new Ultium battery is at the heart of the BEV3 system. While GM emphasized that 20 new EVs will hit the market by 2023, the Ultium battery design holds promise for much more than just storing energy for transportation.

New Battery Chemistry Blend Cut Costs

Individual cells are the key building blocks of any battery pack and that is true with Ultium. However, they are far from the only important element here. The cathode chemistry will be a unique proprietary mixture conjured up by GM and its partner LG Chem. Like many EVs, the Chevrolet Bolt uses cells with a blend of nickel, manganese, and cobalt (NMC). Cobalt is a particularly problematic ingredient because much of it is mined in Central Africa in terrible working conditions.

Every automaker and cell supplier, including GM, is working to develop chemistries with little or no cobalt; GM also aims to eliminate nickel. The Ultium cells have 70% less cobalt content than those in the Bolt, instead aluminum has been added to the NMC mixture. These batteries are known as nickel, manganese, cobalt, and aluminum (NMCA). This has helped to cut the cell cost from $145/kWh to under $100/kWh and also improve the energy density. GM also showed off a sample of a development cell with lithium metal anode in place of graphite, but this is still some years away from production. The NMCA cells will eventually be produced at the $2.6 billion JV plant under construction by GM and LG Chem in Lordstown, Ohio.

Programmable Integrated Battery Management Systems Are on the Horizon

Like the battery packs designed by Volkswagen Group, GM is using a standard module format for its Ultium batteries. Within these modules, GM can pack in pouch cells, like those produced by LG Chem, as well as prismatic cells that give them flexibility to use different suppliers for regions and market segments around the world. What’s distinct about the Ultium pack is that GM has integrated the battery management system (BMS) into each module. Typically, a single centralized BMS manages the output of the entire pack and all of the modules have to have the same output.

The integrated BMS used by GM can be programmed with the characteristics of the cells it contains and can manage the output at the module level. As cell chemistries evolve over time, if a pack needs servicing, GM can replace a module with one containing newer cells. This will reduce the need to keep service stocks of old cell chemistries. This approach also reduces the high voltage wiring in the pack by 80%. The cells now make up 80%-90% of the total pack cost, which based on GM comments should be under $120/kWh.

Since the beginning of the modern EV era in the 2000s, one of the hoped for economic advantages was reusing batteries for other applications such as stationary storage when they no longer had adequate capacity for a vehicle. Until now, there hasn’t been a sufficient supply of used batteries and every car line had unique characteristics making matching more challenging.

An integrated BMS should make it easier to mix and match modules in a stationary storage system, providing a new revenue stream for automakers and reducing vehicle end-of-life costs. Such innovations will be key to making EVs affordable and appealing to the masses while also making the most use out of the resources going into these vehicles.