Secondary Battery Central Side Cell Output Optimization
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Solution Overview
Problem
Lithium secondary batteries face challenges in enhancing output characteristics for electric vehicles due to material blending issues, which can lead to cell degradation and reduced service life when heterogeneous cells with different electrical characteristics are connected in parallel.
Innovation Solution
A secondary battery design where central cells with higher loading energy density and thicker positive electrode material coating layers are connected in parallel with side cells having lower loading energy density and thinner coating layers within a single package, optimizing energy density and resistance distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If blended positive electrode material is used to enhance output, then output characteristics are improved, but microstructure of the active material coating layer deteriorates
Solution Approach 1:
The positive electrode is divided into multiple regions with different active material compositions. The first region contains active material optimized for high SOC range output, while the second region contains active material optimized for low SOC range output. This spatial segmentation allows each region to contribute its strengths without the microstructural conflicts of blending materials at the particle level.
Solution Approach 2:
Different regions of the positive electrode are assigned different material properties and compositions tailored to their specific functional requirements. The first region uses active material with properties suitable for high SOC operation, while the second region uses active material with properties suitable for low SOC operation, optimizing performance locally in each region.
2Power
If heterogeneous cells with different electrical characteristics are connected in parallel to increase output, then output is enhanced, but service life is shortened due to cell degradation
Solution Approach 1:
Multiple unit cells with different electrical characteristics are connected in parallel within a single package, merging their outputs to enhance overall battery power. The cells include different configurations (e.g., different numbers of electrode plates or different active material compositions), allowing them to contribute differently to the total output while working together as an integrated system.
3Power
If blended active materials with different physical characteristics are used, then output in different SOC ranges is improved, but cracks and particle crush occur during coating
Solution Approach 1:
Instead of blending active materials at the particle level, the patent segments the positive electrode into distinct regions, each using a single type of active material optimized for specific SOC ranges. This avoids the mechanical incompatibility and microstructural deterioration that occurs when materials with different physical characteristics are mixed at the particle level.
Solution Approach 2:
Each region of the positive electrode uses active material with properties specifically tailored to its operational SOC range, ensuring optimal performance and structural integrity in each local region without the conflicts arising from material blending.
4Power
If independently-packed cells are connected in parallel, then output is increased, but electrochemical reactions cannot compensate for cell degradation
Solution Approach 1:
Multiple unit cells are merged into a single package with shared electrolyte, allowing electrochemical interactions between cells. This enables cells to compensate for each other's degradation through ion exchange and electrochemical reactions, improving reliability while maintaining enhanced output capability.
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 increases energy density per unit volume, reduces resistance, and enhances output characteristics by enabling electrochemical interactions among cells, compensating for degradation and maintaining performance even when electrolyte or ion density decreases.
Implementation Method 1
The positive electrode plate and the negative electrode plate each includes a positive electrode active material coating layer and a negative electrode active material coating layer where lithium ions can be intercalated or de-intercalated
Implementation Method 2
The cell assembly includes a plurality of unit cells connected in parallel, and each of the unit cells includes at least a positive electrode plate and a negative electrode plate
Data Source
AI summary
A secondary battery having improved output characteristics is disclosed. The secondary battery according to the present invention accommodates a cell assembly including a plurality of cells connected in parallel, and an electrolyte together in one package, in which positive electrodes of a plurality of central cells disposed at a central part of the cell assembly have a loading energy density higher than that of positive electrodes of a plurality of side cells disposed at a side part, and the positive electrodes of the central cells have positive electrode material coating layers formed at surfaces thereof, which are thicker than those formed at surfaces of the positive electrodes of the side cells. Preferably, the total resistance of the side cells is lower than the total resistance of the central cells.