All-solid-state batteries with a Li anode and ceramic electrolyte have the potential to deliver a step change in performance compared with today’s Li-ion batteries^1,2. However, Li dendrites (filaments) form on charging at practical rates and penetrate the ceramic electrolyte, leading to short circuit and cell failure^3,4. Previous models of dendrite penetration have generally focused on a single process for dendrite initiation and propagation, with Li driving the crack at its tip^5,6,7,8,9. Here we show that initiation and propagation are separate processes. Initiation arises from Li deposition into subsurface pores, by means of microcracks that connect the pores to the surface. Once filled, further charging builds pressure in the pores owing to the slow extrusion of Li (viscoplastic flow) back to the surface, leading to cracking. By contrast, dendrite propagation occurs by wedge opening, with Li driving the dry crack from the rear, not the tip. Whereas initiation is determined by the local (microscopic) fracture strength at the grain boundaries, the pore size, pore population density and current density, propagation depends on the (macroscopic) fracture toughness of the ceramic, the length of the Li dendrite (filament) that partially occupies the dry crack, current density, stack pressure and the charge capacity accessed during each cycle. Lower stack pressures suppress propagation, markedly extending the number of cycles before short circuit in cells in which dendrites have initiated.

^{与当今的锂离子电池1,2}相比，具有锂阳极和陶瓷电解质的全固态电池有可能在性能上实现飞跃性变化。然而，锂枝晶（细丝）在以实际速率充电时形成并渗透陶瓷电解质，导致短路和电池故障^3,4。以前的枝晶穿透模型通常侧重于枝晶萌生和传播的单一过程，锂在其尖端驱动裂纹^5,6,7,8,9. 在这里，我们表明启动和传播是独立的过程。通过将孔隙连接到表面的微裂纹，锂沉积到地下孔隙中引发。填充后，由于 Li 缓慢挤出（粘塑性流动）回到表面，进一步充电会在孔隙中产生压力，从而导致开裂。相比之下，枝晶传播是通过楔形开口发生的，Li 从后部而不是尖端驱动干裂纹。起爆取决于晶界处的局部（微观）断裂强度、孔径、孔密度和电流密度，而传播取决于陶瓷的（宏观）断裂韧性、锂枝晶（细丝）的长度部分占据干裂纹，电流密度，堆栈压力和每个循环期间访问的充电容量。较低的堆压会抑制传播，显着延长已引发枝晶的电池短路前的循环次数。