2032 Battery you need - https://amzn.to/3QN9Bcx

Here is a quick little demonstration video on how to swap out your dead 2032 battery in your Toyota Avalon key fob. The process doesn't require any additional tools but a small flat tip screwdriver can be helpful. It's not required but will likely save you some time. You first want to start by removing the mechanical key. Use the tip of that key to open the two halves. Once that is open, go ahead and use your key or a small screwdriver to pry out the dead 2032 coin cell battery. Replace that battery and be sure to place the new one + side facing upward. Clip the two halves back together and you're all set! I hope you found the video helpful!

OEM TOYOTA AVALON SMART KEYLESS REMOTE FOB HYQ14FBC 4 BUTTON
2020 - 2022 - Toyota Avalon Smart Key 4B FCC# HYQ14FBC
2020 - 2022 - Toyota Avalon Smart Key 4 Buttons FCC# HYQ14FBC - 0351 - 315 MHz
This Key Fob fits for:
TOYOTA AVALON 2020 2021 2022
More Information
FCC ID: HYQ14FBC - 0315
Frequency: 315 MHz
Chip ID: Texas ID H 8A - Master 128 Bits
OE #: 8990H-07070
Battery CR2032
Reusable: Yes, after unlocking