Case Study: Li-Ion Battery Testing
The Technical Expert Solution for IP Teams
In this case study, we performed studies to determine the charge cut-off voltage (max voltage) and anode/cathode capacity ratio for Li-Ion batteries found in several major smartphone and notebook products.
GOAL
Batteries are sources of electric power comprising one or more electrochemical cells commonly used across all modern electronic products. Our objective was to demonstrate that the voltage and capacity of batteries found in major smartphones and notebooks available on the market fit within specific parameters.
TEAM
For this project, we employed two highly decorated battery experts. First, a consulting expert with over 30 years of experience in Li-ion technology reviewed the issues and proposed tests. The testing was then carried out by the second battery and energy storage expert, who had relevant experienced in Li-ion battery technology at NASA and various companies. A state-of-the-art energy laboratory was used for all testing.
APPROACH
The cut-off voltage is the voltage at which a battery is considered fully discharged. Further discharge would likely cause harm to the battery, and most modern electronic devices will automatically shut down once the cut-off voltage has been reached.
In this study, we examined the cut-off voltage and max voltage for the batteries of several devices. We attached voltage sensing probes to the battery terminals of host devices such that the cell voltage was measured during charging. A data logging system (biologic potentiostat) was used to collect these data. The discharge/charge cycle was repeated multiple times for each device, and the average cut-off voltage for each device was calculated. A sample graph of the charging curve for a device is provided below.
The capacity ratio between the anode (negative electrode) and the cathode (positive electrode), commonly referred to as the N/P ratio, is an important factor in designing batteries with high performance and balanced electrochemical reactions.
In this study, we determined the capacity ratio of batteries of several devices. Anode and cathode electrodes were harvested from the battery cells as individual half-cells. A harvested anode or cathode of identical area was constructed using lithium metal counter electrodes. The available capacity at a C/20 rate through a full voltage range was determined for the anode and cathode materials and the ratio was then computed. A sample graph of the anode and cathode charging data is provided below.
RESULTS
We were able to accurately calculate the charge cut-off voltage and capacity ratio for the batteries used in several major smartphone and notebook products.
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