Shield Battery are divided into Small Battery, Shield Battery, and Phoenix Battery.
Hold a shield battery and long-press right-click to use it. A Small Shield Battery restores 2 shield bars at once, a Shield Battery restores all shield, and a Phoenix Kit restores both full shield and full health.

Small Battery

/give @p battery_shield:small_battery 1

Shield Battery

/give @p battery_shield:battery 1

Phoenix Battery

/give @p battery_shield:phoenix_battery 1