Manganese-based materials are essential for developing safe, cost-effective, and environmentally sustainable rechargeable batteries, which are critical for advancing clean energy technologies. However, the high spin state of the Mn cation triggers a pronounced Jahn-Teller effect and phase transformations during cycling, leading to structural instability and reduced electrochemical performance of the Mn-based cathodes. This review provides a fundamental understanding of the Jahn-Teller effect, highlights recent strategies to mitigate the high spin state of Mn, and offers insights into future research directions aimed at overcoming the Jahn-Teller effect to enhance the performance of next-generation Mn-based cathodes for rechargeable batteries.