Lithium-ion Battery Positive Electrode Segmentation for Overcharge Safety
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Solution Overview
Problem
Lithium-ion secondary batteries with ternary positive electrode active material particles face reduced gas generation during overcharging, leading to potential safety issues due to inactive gas generation reactions as the state of charge increases, which can result in lower efficiency and increased battery temperature.
Innovation Solution
A lithium-ion secondary battery design incorporating a specific mass ratio of first and second positive electrode active material particles with different compositions, coated with a transition metal oxide, and an overcharge additive in the electrolytic solution to enhance gas generation during overcharging, including a pressure-operated safety mechanism to prevent overcharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ternary positive electrode active material particles are used in the positive electrode, then battery capacity and energy density are improved, but gas generation reaction becomes inactive as state of charge increases
Solution Approach 1:
The positive electrode active material is segmented into two distinct types with different compositions: LiNix1Coy1Mnz1O2 (where x1≥0.5) and LiNix2Coy2Mnz2O2 (where x2<0.5). This segmentation allows each material type to contribute differently to gas generation at various charge states, ensuring continuous gas generation throughout the charging process while maintaining high capacity.
Solution Approach 2:
Different regions of the positive electrode have different material compositions optimized for different functions. The LiNix1Coy1Mnz1O2 particles (with x1≥0.5) provide high capacity but generate gas primarily at lower charge states, while LiNix2Coy2Mnz2O2 particles (with x2<0.5) generate gas more effectively at higher charge states. This local quality differentiation ensures reliable gas generation across the entire charge range.
2Use of energy by moving object
If charging progresses further to increase state of charge, then battery energy output is improved, but gas generation reaction becomes inactive
Solution Approach 1:
The positive electrode active material is segmented into two distinct types with different compositions: LiNix1Coy1Mnz1O2 (where x1≥0.5) and LiNix2Coy2Mnz2O2 (where x2<0.5). This segmentation allows each material type to contribute differently to gas generation at various charge states, ensuring continuous gas generation throughout the charging process while maintaining high capacity.
Solution Approach 2:
The composition parameter x (ratio of Li to Ni) is changed to create two distinct material types. By using LiNix1Coy1Mnz1O2 with x1≥0.5 and LiNix2Coy2Mnz2O2 with x2<0.5, the patent optimizes gas generation at different charge states. The material with lower x value generates gas more effectively at high charge states, enabling continued gas generation even when charging progresses further.
3Reliability
If overcharge additive is added to electrolytic solution to promote pressure operated safety mechanism, then safety is improved, but gas generation becomes insufficient when charging progresses further
Solution Approach 1:
The positive electrode active material is segmented into two distinct types with different compositions: LiNix1Coy1Mnz1O2 (where x1≥0.5) and LiNix2Coy2Mnz2O2 (where x2<0.5). This segmentation allows each material type to contribute differently to gas generation at various charge states, ensuring continuous gas generation throughout the charging process while maintaining high capacity.
Solution Approach 2:
The dual-material composition ensures continuous gas generation throughout the entire charging process. LiNix1Coy1Mnz1O2 particles generate gas primarily at lower charge states, while LiNix2Coy2Mnz2O2 particles generate gas more effectively at higher charge states. This continuity of useful action maintains sufficient gas generation even when charging progresses further, supporting the pressure-operated safety mechanism throughout overcharge conditions.
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
The battery efficiently generates gas during overcharging, even at higher states of charge, reducing the risk of overheating and improving discharge performance by suppressing manganese elution and promoting electron conduction, thus ensuring safer operation.
Implementation Method 1
promoting electron conduction
Implementation Method 2
gas is generated by oxidation of the overcharge additive
Implementation Method 3
The pressure operated safety mechanism converts a pressure applied by generated gas into a mechanical operation such as breaking a circuit
Data Source
AI summary
A positive electrode of a lithium-ion secondary battery contains first positive electrode active material particles and second positive electrode active material particles. The first positive electrode active material particles have a first composition represented by a compositional formula LiNix1Coy1Mnz1O2 (here, x1, y1, and z1 are numerical values satisfying 0<x1<1, 0<y1<1, 0.3<z1<0.5, and x1+y1+z1=1). The second positive electrode active material particles have a second composition represented by a compositional formula LiNix2Coy2Mnz2O2 (here, x2, y2, and z2 are numerical values satisfying 0<x2<1, 0<y2<1, 0<z2<0.2, and x2+y2+z2=1). The surface of at least one of the first positive electrode active material particles and the second positive electrode active material particles is coated with a transition metal oxide.