Reddit mentions of HUSAN New A1322 Laptop Battery Compatible with MacBook Pro 13'' A1322 A1278 (2009 2010 2011 2012 Version) 020-6547-A 661-5229 661-5557 MB990LL/A (Black-1)

Well, first off: OS X 10.11 El Capitan isn't the newest macOS version for your MacBook Pro. Your MacBook pro actually supports macOS 10.13 High Sierra. High Sierra can still be downloaded from the Mac App Store, it is just hidden. Here is the link to it (click this link in Safari only, not in Chrome or Firefox!):

• https://itunes.apple.com/de/app/macos-high-sierra/id1246284741?ls=1&mt=12
  
  OS X El Capitan went out of support in the fall of 2018, so it has been missing out on security for quite some time. Every major macOS version has 1 year of mainstream support (the time frame between its own initial release and the initial release of its successor one year later) and two years of security support immediately after that. Security support includes Safari updates.
  
  Mainstream support for High Sierra has already ended, but its security support only ends in the fall of 2020. So if you update your MacBook Pro to High Sierra, it is still safe to use.
  
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  You can speed your machine up by adding more RAM and an SSD to it:
  
  Your MacBook Pro supports up to 16 GB RAM (2 x 8 GB RAM modules). A higher amount than that won't work due to a limitation in the logic board.
  
  You need to buy RAM that matches the following specifications:
  
  PC3-8500 1066 MHz DDR3, 204-pin
  
  Those are some examples of RAM that should work:
  
  
• https://www.amazon.com/OWC-PC8500-SO-DIMM-MacBook-OWC8566DDR3S16P/dp/B00BKVQFCU
  
• https://www.amazon.com/dp/B00KFNBP24/ref=twister_B07FSYCMM9?_encoding=UTF8&psc=1
  
• https://www.amazon.com/Mushkin-997019-204-pin-DDR3-1066Mhz-PC3-8500/dp/B006E0P1IG
  
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  As for the SSD, your MacBook Pro supports every SSD that meets the following criteria:
  
  
• 2.5" form factor
  
• SATA3-compatible
  
  Here are some examples of SSDs that should work:
  
  
• https://www.amazon.com/Samsung-500GB-Internal-MZ-76E500B-AM/dp/B0781Z7Y3S
  
• https://www.amazon.com/SanDisk-500GB-Ultra-NAND-SATA/dp/B072R78B6Q
  
• https://www.amazon.com/Blue-NAND-500GB-SSD-WDS500G2B0A/dp/B073SBZ8YH
  
  Before you install the SSD, it is advisable to create a backup of the files you want to keep. Store them on some external drive.
  
  You can then reinstall macOS either via Internet Recovery or a macOS 10.13 High Sierra installer USB-Stick (which is the last OS your MacBook Pro supports).
  
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  As for the battery: The battery is replaceable in MacBook Pros 2010. However, you won't be able to get an OEM battery Apple uses, most likely. Those are sold out by now and no longer available, unless you are extremely lucky. There are third party batteries that work, though, like this one for the 13" version(!):
  
  
• https://www.amazon.com/HUSAN-Compatible-661-5229-661-5557-020-6547/dp/B071G53YBQ
  
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  > I also heard mixed things about the new butterfly keyboards, but overall it seems once you get used to them they make your typing faster? So that sounds good for me if it's true
  
  The problem is less the feeling of the butterfly keyboard; beauty is in the eye of the beholder. The problem is that the butterfly keys sometimes outright fail if small particles - like dust - intrude under them. I have discussed the problem here (last paragraph):
  
  
• https://www.reddit.com/r/mac/comments/b86zvo/macbook_retina_vs_macbook_air_school_me_on_which/ejwayit/

ended up going with https://www.amazon.com/gp/product/B071G53YBQ/ref=od_aui_detailpages00?ie=UTF8&psc=1

This one seems like a safe bet. There are some cheaper ones on there but it’s a good idea to buy something that has good reviews especially when buying Chinese stuff. If it doesn’t last as long as it should you have a month to send it back.

https://www.amazon.com/HUSAN-Compatible-661-5229-661-5557-020-6547/dp/B071G53YBQ?ref_=fsclp_pl_dp_2

For the SSD, Crucial is fine. Any SATA SSD is fine. That was just a quick suggestion. All will provide a dramatic improvement in performance.