N/P or N:P ratio

 The "N/P ratio" refers to the ratio of the number of lithium ions (N) that can be inserted into the negative electrode (the "anode") of a lithium-ion battery relative to the number of lithium ions (P) that can be inserted into the positive electrode (the "cathode") of the same battery. This ratio is an important factor in determining the overall performance of a lithium-ion battery, as it affects the battery's capacity, charge/discharge rate, and energy density.

Typically, the N/P ratio in a lithium-ion battery is greater than 1, with a value of around 1.2 being most common. This means that for every 1.2 lithium ions that are inserted into the anode, one lithium ion is inserted into the cathode. The exact value of the N/P ratio can vary depending on the specific materials used in the anode and cathode of the battery, as well as the overall design of the battery.

It's worth noting that the N/P ratio is just one of many factors that can affect the performance of a lithium-ion battery. Other important factors include the type and quality of the materials used in the battery, the size and shape of the battery, and the operating conditions under which the battery is used.

The N/P ratio is defined as the ratio of areal reversible capacity of NE and PE, 

N/P = (QNE/QPE) =(qNE*mNE)/(qPE/mPE) 

Where q is a specific capacity (mAh/g), and m is an area loading of active material (g/cm2) for NE and PE.