Unraveling the interfacial compatibility of ultrahigh nickel cathodes and chloride solid electrolyte for stable all-solid-state lithium batteries

All-solid-state lithium batteries (ASSLBs) combining ultrahigh nickel cathodes have received considerable attention due to their great potential for ensuring safety along with high energy density. Improving the interfacial stability between the cathode and solid electrolyte is crucial for achieving high battery performance. Herein, we first employed in situ electrochemical impedance spectroscopy, galvanostatic cycling, and ex situ time-of-flight secondary ion mass spectrometry techniques to probe the degradation mechanism of the ultrahigh nickel cathode, LiNi 0.92 Co 0.05 Mn 0.03 O 2 , and amorphous Li 2 TaCl 7 electrolyte at different cut-off voltages of 4.3, 4.6, and 4.8 V. At high charge potentials, LiNi 0.92 Co 0.05 Mn 0.03 O 2 cathodes release lattice oxygen, causing the inevitable breakdown of amorphous chlorides and the Li-ion percolating network within the composite cathodes, resulting in a decrease in the capacity and lifespan of the fabricated ASSLBs. In light of these findings, we propose a capacity-cyclability trade-off strategy by reducing the charging voltage, resulting in a durable interface that prevents the generation of lattice oxygen. Specifically, the capacity retention of ASSLBs operating under a high areal capacity of 5 mA h cm −2 remained above 80% for 300 and 600 cycles at 1 and 3 mA cm −2 , respectively. Additionally, the lifespan increased sixfold compared to the 4.3 V charging conditions. Our work elucidates the degradation mechanisms of ultrahigh nickel cathodes and amorphous chloride electrolytes and presents a practical strategy for achieving cycling durability of battery. Highly active lattice oxygen released from ultrahigh nickel cathodes degrade chloride solid electrolytes, forming an inert interphase; this phenomenon worsens at higher voltages. Reducing the cut-off voltage markedly enhances ASSLBs' operational lifespan.