First Principles Study of Aluminum Doped Polycrystalline Silicon as a Potential Anode Candidate in Li‐ion Batteries

Addressing sustainable energy storage remains crucial for transitioning to renewable sources. While Li‐ion batteries have made significant contributions, enhancing their capacity through alternative materials remains a key challenge. Micro‐sized silicon is a promising anode material due to its tenfold higher theoretical capacity compared to conventional graphite. However, its substantial volumetric expansion during cycling impedes practical application due to mechanical failure and rapid capacity fading. A novel approach is proposed to mitigate this issue by incorporating trace amounts of aluminum into the micro‐sized silicon electrode using ball milling. Density functional theory (DFT) is employed to establish a theoretical framework elucidating how grain boundary sliding, a key mechanism involved in preventing mechanical failure is facilitated by the presence of trace aluminum at grain boundaries. This, in turn, reduces stress accumulation within the material, reducing the likelihood of failure. To validate the theoretical predictions, capacity retention experiments are conducted on undoped and Al‐doped micro‐sized silicon samples. The results demonstrate significantly reduced capacity fading in the doped sample, corroborating the theoretical framework and showcasing the potential of aluminum doping for improved Li‐ion battery performance.

解决可持续能源存储问题对于向可再生能源转型仍然至关重要。虽然锂离子电池已经做出了重大贡献，但通过替代材料提高其容量仍然是一个关键挑战。微米级硅是一种很有前途的阳极材料，因为它的理论容量比传统石墨高十倍。然而，它在循环过程中的大量体积膨胀由于机械故障和快速的容量衰减而阻碍了实际应用。提出了一种新的方法来缓解这个问题，即通过球磨将微量的铝掺入微米级硅电极中。采用密度泛函理论（DFT）建立了一个理论框架，阐明了晶界滑动（一种防止机械故障的关键机制）是如何通过晶界处微量铝的存在而得到促进的。这反过来又减少了材料内部的应力积累，降低了故障的可能性。为了验证理论预测，对未掺杂和铝掺杂的微米级硅样品进行了容量保持实验。结果表明，掺杂样品的容量衰减显著降低，证实了理论框架，并展示了铝掺杂对提高锂离子电池性能的潜力。