Hello
Are you using Arduino board to build your sensor? If you’re using it, normally the working voltage of Arduino is 5V, and you can connect your battery directly to analog port (The max output voltage of Lipo battery is 3.7V), and if your working voltage of Arduino is 3.3V, you can use two 1k resistances connected in series to get the voltage divided.
By the way, if there is an ADC module in your design, in theory you can use it to get the charge of the battery and you don’t need a another voltage divider. If you have any other questions, give your feedback to us. 
Thanks sincerely,
JL