You should use a formal tone when writing academic papers.
One way you can do this is by not using contractions in your papers. In fact, contractions should never be used in your academic writing.
Contractions are short forms that combine subjects and verbs using an apostrophe.
Example
There's a relationship between quality of care and patient satisfaction. (There and is are combined)
The above sentence should be as follows: There is a relationship between quality of care and patient satisfaction.
More Information
"Contractions in Formal Writing," APA Style Blog
"Basic Grammar and Punctuation: Apostrophes," St. Petersburg College
