Hi Martin,
I wouldn’t recommend using battery power for LED strip lighting. The voltage in a LiPo will vary depending on the available charge in the battery which will give you a changing brightness as the battery wears, plus you will need monitoring circuitry to ensure you don’t damage the LiPo and other components.
Even a big 6000mAh LiPo battery would only power a 2m LED strip for less than 2 hours at full brightness. Mains is well and truly the best way to go.