Layered NCM Electrode Assembly for Capacity and Thermal Stability
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Solution Overview
Problem
Secondary batteries with high nickel content in NCM-based positive electrode materials face a trade-off between increased capacity and decreased thermal stability, leading to potential ignition issues.
Innovation Solution
The electrode assembly stacks multiple positive electrodes with different nickel, cobalt, and manganese composition ratios, with higher nickel content on the outer electrodes for capacity and lower nickel content on inner electrodes for improved thermal stability, and separates positive electrode tabs to reduce electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel content in NCM-based positive electrode material is increased, then battery capacity is improved, but thermal stability deteriorates
Solution Approach 1:
The electrode assembly is divided into multiple positive electrodes with different nickel content compositions. Outer positive electrodes contain NCM material with higher nickel content (e.g., Ni:Co:Mn = 8:1:1) for high capacity, while inner positive electrodes contain NCM material with lower nickel content (e.g., Ni:Co:Mn = 6:2:2 or 4:3:3) for thermal stability. This segmentation allows simultaneous optimization of both capacity and safety.
Solution Approach 2:
Different regions of the electrode assembly are assigned different material compositions tailored to their specific functional requirements. The outer electrodes, which contribute more to overall capacity, use high-nickel NCM material. The inner electrodes, which are more susceptible to thermal runaway, use low-nickel NCM material with better thermal stability. This local quality differentiation resolves the capacity-stability trade-off.
2Reliability
If multiple positive electrodes with different composition ratios are stacked, then both capacity and thermal stability are improved, but device complexity increases
Solution Approach 1:
The electrode assembly is segmented into multiple positive electrodes stacked in sequence, where outer electrodes use high-nickel NCM material and inner electrodes use low-nickel NCM material. This segmentation strategy enables simultaneous optimization of capacity and thermal stability while maintaining a relatively simple overall structure that follows conventional battery design patterns.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances both thermal stability and capacity while minimizing electrical resistance and cell damage, improving the overall performance and lifespan of secondary batteries.
Implementation Method 1
a process, in which lithium ions are intercalated and deintercalated from lithium metal oxide to the negative electrode, is repeated to charge and discharge the lithium secondary batteries
Implementation Method 2
measuring a temperature change (a vertical axis) versus time (a horizontal axis) while heating is performed at a temperature of 80° C. to 200° C. at a rate of 2K/min
Data Source
AI summary
An electrode assembly comprises: a negative electrode, a separator, and at least two or more positive electrodes which are stacked in the electrode assembly with the negative electrode and the separator, each of the positive electrodes including a positive electrode active material applied to a surface of a positive electrode collector, wherein the positive electrode active material contains nickel, cobalt, and manganese, and a first composition ratio of nickel, cobalt, and manganese in the positive electrode active material applied to a first one of the positive electrodes is different from a second composition ratio of nickel, cobalt, and manganese in the positive electrode active material applied to a second one of the positive electrodes. The first and second positive electrodes may be stacked to adequately improve thermal stability and capacity.