Lithium has confused scientists for decades at almost every scale of the universe. Lithium-rich giants are peculiar stars with lithium abundances greater than model prediction. A large fraction of lithium-rich low-mass evolved stars are traditionally supposed to be red giant branch (RGB) stars. Recent studies, however, report that red clump (RC) stars are more frequent than RGB stars. Here, we present a uniquely large systematic study that combines direct asteroseismic analysis and spectroscopy of the lithium-rich stars. The majority of lithium-rich stars are confirmed to be RCs, whereas RGBs are a minority. We reveal that the distribution of lithium-rich RGBs declines steeply with increasing lithium abundance, with an upper limit of around 2.6 dex, whereas the lithium abundances of RCs extend to much higher values. We also find that the distributions of mass and nitrogen abundance are notably different between RC and RGB stars. These findings indicate that there is still an unknown process that significantly affects surface chemical composition in low-mass stellar evolution.

数十年来，锂几乎使宇宙的各个尺度的科学家困惑。富含锂的巨星是奇特的恒星，其锂丰度大于模型预测值。传统上，大部分富含锂的低质量演化恒星被认为是红色巨星（RGB）星。但是，最近的研究报告说，红色团块（RC）恒星比RGB恒星更频繁。在这里，我们提出了一个独特的大型系统研究，该研究结合了直接锂震分析和富锂星光谱的光谱分析。多数富含锂的恒星被确认为RC，而RGB仅占少数。我们发现，随着锂丰度的增加，富锂RGB的分布急剧下降，上限约为2.6 dex，而RC的锂丰度扩展到了更高的值。我们还发现，RC和RGB恒星之间的质量和氮丰度分布明显不同。这些发现表明，还有一个未知的过程会严重影响低质量恒星演化过程中的表面化学组成。