Asahi Kasei's lithium pre-doping tech boosts

Asahi Kasei has developed a lithium pre-doping technology for silicon-rich lithium-ion batteries, aiming to cut first-cycle capacity loss.

Asahi Kasei has announced a new lithium pre-doping technology designed for high-voltage lithium-ion batteries that use silicon-based anodes. The Japanese chemical company says the method compensates for the large, permanent capacity loss these cells suffer during their initial charge and discharge cycle.

According to Asahi Kasei, electric vehicles are a key application driving the demand for higher cell energy density. Development efforts have focused on two main changes: partially replacing graphite in the anode with silicon-based materials and raising the cathode's operating voltage. The new pre-doping technology specifically tackles a penalty associated with the first change.

The Silicon Advantage and Its Cost

Silicon can hold more lithium per gram than graphite, which is why it is blended into anodes. There is a significant trade-off, however. The company states this blending causes a large irreversible capacity loss on the first charge.

This loss limits both the cell's cycle life and its overall energy density. To compensate, manufacturers typically must load extra cathode active material, which increases material use and cost.

Asahi Kasei's solution involves adding lithium carbonate to the cathode as an extra lithium source. The company says lithium carbonate is relatively inexpensive and has an established history as a battery material. Its decomposition voltage, however, has traditionally been too high for use in standard lithium-ion cells.

How the Pre-Doping Technology Works

The new technology uses special additives in the electrolyte. These additives promote the decomposition of lithium carbonate at the normal operating voltages of a standard battery. When pre-added to the cathode, the carbonate breaks down during the initial charge and releases its lithium into the cell.

This process aims to make up for the capacity that would otherwise be permanently lost in silicon-rich anodes. The company claims the approach requires no major modifications to existing battery manufacturing lines.

Reported Performance and Next Steps

In its own tests, Asahi Kasei measured the technology's impact on a specific cell configuration. The company reports a 10% increase in energy density was achieved.

Asahi Kasei also states the technology improves cycle life at a low cost per watt-hour. It expects the method to work across various cathode and anode material systems.

The company will now begin proof-of-concept evaluations with global customers. It plans to phase licensing arrangements according to each customer's stage of development.

Source: Charged EVs