Highly Reversible Li‐Insertion/Extraction in Octahedral Voids of LiNi _0.5 Mn _1.5 O ₄ Cathode With

In this work, we explore the possibility of utilizing lithium nickel manganese oxide (LiNi _0.5 Mn _1.5 O ₄ or LNMO) as a cathode material for developing a stable and safe Li‐ion battery (LIB). The full‐cell configuration is assembled by pairing LNMO with coprecipitated SnS, a high‐capacity alloy‐type anode material that surpasses conventional anode materials, such as graphite. While LNMO is typically operated in the high‐voltage region (~4.8 V vs. Li) utilizing the Ni ^2+/4+ couple associated with tetrahedral insertion, such operation often leads to severe electrolyte degradation and parasitic reactions. To overcome this, we employ a lower‐voltage (~2.8 V vs. Li) approach that utilizes the Mn ^4+/3+ redox couple corresponding to octahedral insertion, enhancing safety and stability. However, conventionally synthesized (i.e., bulk) LNMO often fails to facilitate this insertion, prompting us to adopt the electrospinning technique to produce nanostructured LNMO with improved Li‐ion kinetics and ionic transport that supports octahedral insertion. Our work also demonstrates the importance of nanostructuring, which facilitates octahedral insertion and enables us to incorporate a low‐voltage application without compromising safety. The electrospun (E‐spun) LNMO can exhibit a higher discharge capacity and superior cycling stability in both high‐ and low‐voltage regions; however, we will focus on low‐voltage applications. This hybrid configuration, integrating a fast Li‐ion diffusion spinel cathode and a high‐capacity alloy anode, enables efficient ion transport and enhanced electrode compatibility. By narrowing the voltage window to 2–3 V versus Li, the system exhibits stable cycling performance, along with improved safety, which facilitates the development of next‐generation LIBs with balanced performance and durability.