  Floating-zone growth of untwinned single crystal of Li_xCu_2O_2 with high Li
content of x ~ 0.99 is reported. Li content of Li_xCu_2O_2 has been determined
accurately through combined iodometric titration and thermogravimetric methods,
which also ruled out the speculation of chemical disorder between Li and Cu
ions. The morphology and physical properties of single crystals obtained from
slowing-cooling (SL) and floating-zone (FZ) methods are compared. The
floating-zone growth under Ar/O_2=7:1 gas mixture at 0.64 MPa produces large
area of untwinned crystal with highest Li content, which has the lowest
helimagnetic ordering temperature ~19K in the Li_xCu_2O_2 system.
