@corey & @frlobo: Sorry to contradict, while they do use the same controler chip they are not the same product.
There was already a question about this - I’ll try to find it and post back.
Edit: Found it
Particle Battery Shield vs SparkFun Battery Shield
The last batch of the Particle Power Shields was shipped with a 2000mAh/7.4Wh LiPo
One other difference I see (but can’t confirm, since I’ve not got a SparkFun one) is, that the Particle shield does have its own micro USB connector for charging but can’t charge the battery via the Photon’s/Core’s USB. The SparkFun one seems to do it via the device too.
The Particle one comes with not-presoldered long pin headers which allow to have the Shiled with Device plugged into a breadboard, while the SparkFun has already soldered standard headers.