## 1 Introduction  
Lithium-ion batteries (LIBs) have become the cornerstone of modern energy systems due to their superior energy density, extended cycle life, minimal self-discharge rate, and absence of memory effect [1], powering a wide range of applications, from portable electronics and renewable energy storage, to electric vehicles, ships, and aircraft. These applications are increasingly pushing the boundaries of battery performance, with a particular emphasis on fast-charging capability and high-rate discharging performance. For example, electric vehicles require rapid charging to improve user experience [2], energy storage stationsmust deliver millisecond-level power for grid frequency regulation [3], and electric marine propulsion systems demand high-current pulse discharges on the kiloampere scale [4]. These demanding scenarios place great stress on the battery's current-carrying components [5; 6; 7; 8], making the optimization of overcurrent capability a critical technical challenge. Inadequate overcurrent tolerance can result in severe thermal and structural failures [9; 10; 11] such as localized overheating, internal fusion, and ultimately, thermal runaway. Enhancing the overcurrent capability of LIBs can be approached from the perspectives of material design and internal structure design [12; 13]. On the materials side, numerous efforts have been made to develop active materials with improved electrical and thermal properties. Carbon-coated LiFePO\({}_{4}\) particles [14; 15], ceramic separators [16], optimized electrolytes [17; 18], and fast ion-conductive anode materials [19; 20; 21] have significantly improved rate performance and thermal resilience. Furthermore, phase-change materials have shown promise in enhancing thermal conductivity to maintain the thermal stability of LIBs [22; 23]. However, while these material-level innovations have gained widespread attention, relatively few studies have addressed the internal conductor structure (also termed current collector [24]), which is a critical current pathway inside the battery. Despite frequent reports of failure in internal conductor structures during high-current applications, the in-depth research on this issue remains limited. Especially under extreme load conditions, such as those encountered in electric propulsion or fast-charging stations, the internal conductor structure often becomes the weakest link [25], resulting in localized failure. This lack of understanding hinders the development of structurally robust LIBs capable of withstanding the increasing current loads. High-current operation introduces additional complexity and risk, particularly in thermal management. Elevated current densities accelerate Joule heating, intensify thermal gradients, and increase the likelihood of triggering thermal runaway events. Significant in-plane and through-thickness temperature gradients are observed during a 10 C discharge (200 A) [26], while multiphysics simulations have demonstrated how heat generation and voltage drop become tightly coupled under 5 C to 10 C conditions [27; 28; 29; 30]. In parallel, electrical constraints such as limited internal space and high energy density severely restrict the design flexibility of current-carrying structures, often forcing them to operate near their thermal and electrical failure thresholds. Although recent studies have improved high-rate operation to the hundred-ampere level [31; 32; 33; 34], the kiloampere-level discharge regimes urgently required by next-generation technologies remain largely unexplored. The current lack of understanding in this extreme regime prevents the development of safe, high-power LIBs for future applications. This study addresses a critical knowledge gap in lithium-ion battery design by systematically investigating the impact of internal conductor structural configurations on overcurrent resilience under ultra-high current conditions (>10 KA).