The Russian, trying to reach her fourth Grand Slam final in her past seven appearances, had romped through her first five matches for the loss of just nine games, an Australian Open record.
But on a day when her own groundstrokes lacked a little bite and her court coverage was exposed, she never found an answer to Li's aggressive game-plan, which paid off perfectly in a 6-2 6-2 win.
"I think she played a really great match," Sharapova said. "She was certainly much more aggressive than I was, dictating the play. I was always on the defence.
"She was taking the first ball and doing something with it. When I was trying to, I was making too many unforced errors.
"When I had my opportunities and breakpoints in games that went to deuce, I don't think any of them really went my way today."
At 6ft 2in, movement is always going to be an issue for Sharapova and though the Russian has worked hard in the past two years to improve that area of the game, the more nimble Li exposed her weakness in ruthless fashion.
Time and again, she pulled Sharapova wide on her weaker forehand side, both on serve and off the ground, and the off-balance Russian made a series of surprising mistakes.
Even more crucially, with the benefit of a fast start, a relaxed Li attacked Sharapova's second serve, winning a whopping 18 of 24 points when the No 2 seed missed her first serve.
Continually under pressure, Sharapova was then guilty of pressing too much and the mistakes flowed.
Li hit more winners, almost half as many unforced errors and moved better, her strong base allowing her the chance to attack even when in a seemingly defensive position.
Last August, former French Open champion Li appointed Carlos Rodriguez as her new coach and the Argentinian immediately set about making technical changes to her forehand.
Without that, he said, Li would remain a top-10 player but never add to her Grand Slam tally.
Rodriguez famously coached former world No 1 Justine Henin and the Belgian had a good record against Sharapova.
His tactical input clearly gave Li a kickstart as she began well and then maintained her momentum all the way to victory and a third Grand Slam final.
"When your opponent is always up and ahead, it's always a little bit mentally easier for them to keep that going," Sharapova admitted.
"If I had taken those chances and clawed my way back and made it a bit tougher for her, I'm sure she would have thought a little bit more. But I certainly didn't make her think about anything.
"She always had a little bit of the edge. From the beginning, she was up a break. That's why I said I don't think I gave her much to think about because she was always playing ahead.
"That's tough because you have an opponent that's playing well and aggressive and confident tennis. It was just one of those days."
Sharapova's defeat ended her immediate hopes of regaining the world No 1 ranking but the Russian said she was sure she would bounce back.
"I've been in this position before and I've come through it," she said. "I'm tough. I'm not afraid to go out and keep working, work as hard as I can to be quicker, better, improve in these situations, and when I have another chance, take it."
- Sports & Recreation