The bipolar battery essentially moves the series connections inside the cell. This brings a number of advantages and significant challenges.
This is shown very clearly in the Toyota battery technology roadmap [1].
The expectation from Toyota is to deliver the following benefits in 2027-2028:
- 10% cost reduction over a monopolar battery
- Rapid charging time of 20 minutes or less for 10 – 80% SOC
Gambe et al [2] show the bipolar semi-solid state cell and manufacturered 2 and 3 layer bipolar cells in the lab that operated at 2x and 3x the voltage of the single layer device. Thus showing that it is possible to make asemi-solid state cell with a nominal voltage of ~10V.
The advantage is that you remove the need for external connections and some of the cell packaging. Reducing cost, package space and mass.
However, the challenges are significant [3, 4]:
- mechanical sealing
- electrical connections between bilayers
- chemical stability
- state of charge estimation
- state of charge balance across cells within a bipolar cell
- uniform temperature
Toyota have had bipolar NiMh in production since 2021. As of September 2026, the bipolar LFP “Popularization” pack has not yet reached production; Toyota’s roadmap and recent reporting place its launch in 2026-2027 [6]. See our 2025 Battery Roadmaps post for the wider industry roadmap context, and our Toyota Batteries benchmark page for more on Toyota’s pack designs.
Microvast Breakthrough in Solid State
This bipolar design significantly reduces the number of interconnections between cells, modules, and packs. This simplifies the overall system architecture and enhances both energy efficiency and operational safety. [5]
References
- Toyota sets out advanced battery technology roadmap, Toyota Media
- Gambe, Y., Sun, Y. & Honma, I. Development of Bipolar All-solid-state Lithium Battery Based on Quasi-solid-state Electrolyte Containing Tetraglyme-LiTFSA Equimolar Complex. Sci Rep 5, 8869 (2015)
- P. Mohana Sundaram, Chhail Bihari Soni, Sungjemmenla, S.K. Vineeth, C. Sanjaykumar, Vipin Kumar, Reviving bipolar construction to design and develop high-energy sodium-ion batteries, Journal of Energy Storage, Volume 63, 2023
- The Breakthrough of Bipolar Batteries and Toyota’s Remarkable Achievement, Dr. Ivana Veljkovic, LinkedIn post
- Microvast Announces Breakthrough in True All-Solid-State Battery Technology, Microvast Press Release, January 2025
- Toyota Details Next-Gen EV Batteries, Promises 497-Mile Range In 2026, InsideEVs, 2026
See also: Semi-Solid State Battery
It appears to me, naively, as parallel connection versus series connection of unit cells…if that’s the case, won’t single failure deactive teh entire bipolar assembly?
Yes, single unit failure will fail the whole cell. Same as a 1p battery pack where one cell failure means the whole pack fails.