Amorphous precipitated silica which may be used to form battery separators of very low shrinkage is characterized by (a) a BET surface area in the range of from 60 to 200 m.sup.2 /g; (b) a CTAB surface area in the range of from 40 to 150 m.sup.2 /g; (c) a DBP oil absorption in the range of from 180 to 300 cm.sup.3 /100 g; (d) a mean ultimate particle size in the range of from 20 to 30 nm; (e) a total intruded volume in the range of from 2.5 to 4 cm.sup.3 /g; (f) an intruded volume in the range of from 0.3 to 1.2 cm.sup.3 /g for pores having diameters in the range of from 20 to 100 nm; and (g) a pore diameter at the maximum of the volume pore size distribution function in the range of from 30 to 200 nm.