What is the bond order of Li2- ion

use simple MO diagram
[Li2]^- = three valence e⁻ = σs(2e⁻) σs*(1e⁻) σp(0e⁻) πp(0e⁻) πp*(0e⁻) σp*(0)
Bond Order = ½[Σ(bonding e⁻) - Σ(antibonding e⁻)]
bo = ½[σs(2e⁻) - σs*(1e⁻)] = 0.5