We developed an in situ radiotracer method for diffusion studies in solids using short-lived α-emitting &lt
sup&gt
8&lt
/sup&gt
Li tracer. In the method, while implanting a pulsed &lt
sup&gt
8&lt
/sup&gt
Li beam into a solid material of interest, the α particles emitted into the implantation side of the sample surface were detected as a function of time. By changing the implantation depth and the detection angle against the sample surface according to lithium diffusivity (deep implantation and large angle with a large solid angle, or shallow implantation and small angle with a narrow solid angle), the method can be sensitive to a wide range of diffusion length ranging from micrometer scale to nanometer scale per second. The feasibility of the method was demonstrated by measuring the lithium diffusion coefficients to the order of 10&lt
sup&gt
-12&lt
/sup&gt
cm&lt
sup&gt
2&lt
/sup&gt
/s in lithium ionic conductors.