Based on my understanding, they do indeed mean the same thing and are written in Kanji the same way, but may be said differently. にっぽん is an older way of saying the 日本 and is usually read as にほん these days. You'll usually hear にっぽん in very formal and official contexts. In daily conversation にほん is likely the only one you'll hear or use, unless you are referencing a title to something that uses the word にっぽん instead.

Lee-san has a great grasp of word　日本! I was going to post the followings, so please let me post this anyway. As you've already known that, there are two pronunciations for 日本, にほん and にっぽん. Actually, it hasn't been enacted by Japanese government which we should use. So, it's a matter of preference. However, we mostly use にほん. "Nippon" is easier to say it loud than "Nihon", probably because its "pp" is a plosive sound. So, when someone would like to call for 日本　strongly/loudly or put an emphasis on 日本, the pronunciation is likely "Nippon". For example: In Olympic games, you can hear Japanese audience cheer on Japanese teams by shouting and clapping their hands like にっぽん　(clap) (clap)(clap)(, which action is called ニッポンチャチャチャ).

Hồ dành cho công chúng. Poe là quân đội. → Nó đã được sử dụng cho Thế vận hội Olympic.