The heart of any electric vehicle lies in its battery. The range, weight, and lifespan of the battery pack are critical factors that determine the vehicle’s performance and practicality. Even traditional technologies like lead-acid batteries, which have been used for decades for vehicle starting, are undergoing innovations to meet modern demands. One such innovation is the development of a new titanium collector designed for bipolar architecture where cells are stacked in a compact block.
In modern batteries, whether lead-acid or lithium-ion, the collector is a metallic support that carries electrons from the active material to the external terminals. While it does not store energy, it is essential for the electrode to communicate with the rest of the circuit. In bipolar lead-acid batteries, where multiple elements are in close contact within a compact sandwich structure, the collector must also withstand the mechanical load of the assembly, much like a chassis supporting a battery pack under a vehicle.
The Role of Titanium in Battery Collectors
Titanium is already being studied for use in specialized long-lasting cells because it spontaneously forms a very stable oxide layer that protects it from corrosion. However, its electrical conductivity is lower compared to copper and aluminum, and it is more expensive. As a result, titanium has been used primarily in environments where chemical resistance is more critical than pure electrical efficiency, such as in highly aggressive conditions.
In a study highlighted by ScienceDirect the titanium collector is designed asymmetrically: the titanium does not cover both sides uniformly but is distributed differently to adapt to the role of each element within the bipolar cell. This design allows the same ‘plate’ to offer more robustness where structural support is needed and greater conductivity where current flow is prioritized. However, this remains a research prototype and is not yet ready for commercial battery production lines.
Balancing Structure and Conduction
Every material used as a collector must meet four key conditions simultaneously: resistance to oxidation and reduction reactions within the battery, good adhesion to the active energy-storing layer, sufficient mechanical strength to prevent bending or cracking, and thermal stability when the cell heats up during charging and discharging. A layer that is too thin saves weight but risks deformation, while one designed solely for robustness can increase internal resistance and overheating.
The asymmetric design helps separate these functions: using titanium where mechanical resistance and corrosion resistance are paramount, and reducing its area where the priority is to conduct current without losses. This compromise is similar to the development of steel casings for electric vehicle batteries, where the same structure must protect the pack in case of impact while not adding too much weight to the vehicle.
Applications in Mobility and Automotive
Bipolar lead-acid batteries are already moving beyond theoretical stages. Architectures of this type, often reinforced with fiberglass grids or composite materials, are being integrated into products requiring robustness, repeated charging cycles, and compact sizes. These applications range from stationary energy storage systems to commercial vehicles.
In this context, a more efficient collector directly impacts internal resistance and charge cycle lifespan, determining how much energy is lost as heat and how many times the battery can be used before significant degradation occurs. The comparison with lithium-ion batteries is more of a trend indicator than a direct comparison. Lighter and better-integrated collectors have already shown in other chemistries to reduce weight and improve energy density, as demonstrated by studies on the impact of mechanical stress on lithium-metal batteries.
For bipolar lead-acid batteries, the titanium collector remains a research application today. It could contribute to making accumulators more compact and long-lasting in vehicles where weight is less critical but operational durability is highly valued.
