https://wccftech.com/airpods-pro-lite-ship-with-coin-shaped-batteries/

For the first and second-generation AirPods, Apple employed the use of pin-shaped batteries supplied to it by LG Energy Solutions. However, with the launch of the AirPods Pro in 2019, the tech giant switched to coin-shaped cells, likely due to the smaller space the company had to work with. Now, according to a report, which refers to the AirPods 3 as the ‘lite’ version of the AirPods Pro, Apple is expected to stick with coin-shaped batteries, which in turn, should increase the component’s popularity in the future.

When Apple released the AirPods Pro, the gravitation towards coin-shaped batteries allowed this cell form to capture a market share of 57 percent in 2020. In contrast, the market share of pin-shaped batteries was at 18 percent, suggesting that the AirPods Pro outperformed both the first and second-generation AirPods in terms of sales. A report from The Elec does not confirm if using coin-shaped batteries has any cost-saving benefit for Apple.