What is the purpose of this plastic piece inside my MacBook Air? I have a MacBook Air (13-inch, Early 2015). The model number is A1466 (EMC 2925).
I recently removed the bottom case (in order to fix my trackpad) and immediately noticed broken plastic pieces inside of a slot located near the middle of the bottom case. Below are two images showing opposite sides of the two pieces I recovered:


There is a matching slot where these pieces fit in the middle of the battery. The slot is in the shape of a rectangle with semi-circle ends. I didn't get pictures of my battery before I put everything back together, but here is an image of the same type of battery (The slot is right above the middle screw):

In my research I found this post which may be a duplicate of my question. I'm not sure though as the model is different.
Is this plastic piece intended to hold the bottom case snug with the battery/upper casing? Is this piece important?
Thank you in advance for any replies to my query!
It is a structural connector and should be repaired and replaced. The battery is part of what makes the case stiff so your device will be more susceptible to bends. Not having the bottom cover latch in could damage the batteries in a very unsafe way. Same if that piece or even a tiny screw were wedged between any part of the top case or bottom cover and the battery thereby pinching or puncturing the exposed cells.
Rather than risk a fire, I would have someone trained on Mac repairs examine your Mac and evaluate of it’s safe due to any chance a piece of plastic or screw was loose inside. The linked article you mentioned has a much less fragile battery and isn’t as susceptible to torsion due to a fundamentally different case structure design. Your battery has less armor than the older ones and safety depends entirely on zero loose parts being inside the case.
A proper fit of the bottom plate for ensured protection and structural integrity. Zero debris ensures safe operational conditions.

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