The iPhone 17 Air Could Use a Silicon-Carbon Battery. What Is It?

"Apple has taken the second approach with caveats. Rumors suggest the iPhone 17 Air's battery capacity will sit around 2,900 mAh, a steep drop from prior iPhone models, especially at the 6.6-inch screen size. But the company is supposedly making up for it with power-saving tricks to make sure battery life remains similar to other iPhones, including Apple's more efficient C1 modem that debuted on the iPhone 16e earlier this year."

"The problem with silicon batteries is that they expand. When you lithiate raw silicon, Luebbe says it can expand up to three times its initial volume. Lithium-ion batteries also swell; you've probably heard of or maybe even experienced this, as it can happen for a myriad of reasons. It means something has gone wrong, and the battery is now a safety risk."

""Imagine a carbon sponge, but the pores of that sponge are on the single-digit molecule wide, we're talking less than 10 nanometers wide," he says. These pores are filled with silane gas (the silicon), but only about halfway. The particle you're left with is made up of silicon, carbon, and void space. When the lithium ions head over from the cathode to the anode and the silicon lithiates, it expands to fill the void spaces of the particle."

iPhone 17 Air battery capacity is rumored to be around 2,900 mAh, a steep reduction for a 6.6-inch device, with Apple relying on power-saving techniques and the more efficient C1 modem to maintain comparable battery life. Luebbe declined to confirm whether Group14's silicon-carbon composite is used in the iPhone 17 Air batteries; Sila Nanotechnologies and Enovix did not immediately respond to requests for comment. Silicon anodes can expand substantially when lithiated, potentially up to three times their initial volume, which can cause lithium-ion batteries to swell and become safety risks. Group14's approach uses a porous carbon material with sub-10-nanometer pores partially filled with silane gas, allowing silicon to expand into internal voids and mitigating particle-level expansion to stabilize cycle life.

Read at WIRED