Instruction:
What are some of the most important attributes of spacecraft battery and how are these attributes realized?

Response:
Some of the most important attributes are reliability, low mass.  Reliability is often achieved through qualification testing, demonstrated performance in a flight environment and configuration management.  Mass can be minimized by using high-performance Li-ion batteries that are optimized for the anticipated use case and by right-sizing the battery to meet end of mission power requirements using calibrated battery life and performance models.