Enhanced High‐Voltage Fast‐Charging Capability for Lithium‐Ion Battery Cathodes via Multifunctional Biphasic Interfacial Engineering

High‐capacity Li‐rich Mn‐based oxide cathodes exhibit exceptional specific capacity density; however, their utilization encounters challenges pertaining to sluggish Li + ion transport kinetics and severe interfacial issues in high‐voltage lithium‐ion batteries, especially under the working condition of fast charging. Here, a protective biphasic shell layer coupled with B/Al co‐doping in the near‐surface bulk phase region is designed on Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 cathode by means of feasible and facile chemical surface reconstruction engineering to solve performance degradation and structural collapse. The biphasic layer that is in situ fabricated consists of an amorphous Li 2 B 4 O 7 coating as the outermost layer and a spinel phase structure as the inner layer, respectively. Structural analysis confirms that the engineered interface assisted by surface co‐doping enhances interfacial stability by promoting the fast transfer of Li + ion and mitigating surface side reactions. As a consequence, the engineered batteries are demonstrated to achieve remarkable performance, delivering 138 mAh g −1 at 5 C, along with enhanced cycling stability, retaining 90.07% of their initial capacity after 300 cycles within a voltage range of 2.0–4.8 V compared to their layered oxide counterparts. This work provides an interface/surface modification strategy that simultaneously addresses kinetic hindrance and structural instability, while manipulating the interface effect of cathodic materials.