Realizing ≥99.9% Li Plating/Stripping Coulombic Efficiency in a Solid-State Li Metal Battery via Constant Interfacial Contact-Targeted Zero-Volume-Change Host Design

Solid-state lithium metal batteries (SSLMBs), particularly in anode-less configurations, are severely hindered by catastrophic electrochemomechanical degradation at the Li anode-solid electrolyte interface caused by infinite anode volume fluctuations during Li plating/stripping reaction, posing significant challenges to its cycling reversibility. Here, we report a zero-volume-change cellular void-structured host that changes the solid-state Li metal anode reaction mechanism, from infinite volume-changing Li deposition/dissolution at the anode-solid electrolyte interface to Li deposition/dissolution inside the voids of the host with zero-volume-changing feature. Operando pressure/microscopy characterization verifies that the zero-volume-change cellular void host architecture terminates the critical Li anode volume-change-induced solid-solid interface delamination failure that has constrained SSLMB development for decades, thus achieving a record-breaking Coulombic efficiency (≥99.9%) that surpasses prior benchmarks by 1-3 orders of magnitude. Meanwhile, anode-less SSLMBs using the zero-volume-change host with a negative:positive capacity ratio of 0 can realize 95.5% capacity retention after 400 cycles at low stack pressure (440 kPa), representing one of the best SSLMB performances so far. By resolving the root cause of the Li anode volume-change-driven fluctuated interface contact failure mechanism in the SSLMB, this work provides an anode design strategy for cycling-stable solid-state lithium metal battery construction.