Positive Electrode Composition for High-Temperature Li-Ion Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges with high irreversible capacity and structural instability due to excess lithium in positive electrode materials, leading to voltage sagging and degradation, particularly at high temperatures.
Innovation Solution
A positive electrode material comprising a combination of large and small lithium composite transition metal oxide particles, where the first material has a lithium-to-metal ratio of 1 to 1.5 and the second material has a crystallite size of 180 nm or more, enhancing structural stability and thermal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If excess lithium-containing lithium transition metal oxide is used as positive electrode active material to achieve high capacity and high output, then capacity and output characteristics are improved, but irreversible capacity increases and oxygen is released causing structural collapse and voltage sagging
Solution Approach 1:
The invention changes the particle size parameter by classifying positive electrode active material particles into specific size ranges (1 μm to 5 μm for first material, 0.5 μm to 2 μm for second material). This parameter change allows the material to achieve high capacity and output while maintaining structural stability, resolving the contradiction between productivity and reliability.
Solution Approach 2:
The invention applies local quality by using two different positive electrode active materials with different particle size characteristics in specific proportions (60-90 wt% first material, 10-40 wt% second material). The larger particles provide structural stability while the smaller particles enhance capacity and output, allowing each component to fulfill its specific function.
2Power
If excess lithium-containing lithium transition metal oxide is used to utilize surplus lithium, then high voltage activation is achieved, but oxygen is released to the outside causing active material structure collapse and voltage sagging phenomenon
Solution Approach 1:
The invention changes the particle size parameter to specific ranges (1 μm to 5 μm and 0.5 μm to 2 μm) which prevents oxygen release during high voltage activation. This parameter optimization allows the material to achieve high voltage activation without the harmful effects of oxygen release and structural collapse.
Solution Approach 2:
The invention converts the potential harm of excess lithium into a benefit by carefully controlling particle sizes. The specific particle size ranges enable the material to utilize surplus lithium for high voltage activation while preventing oxygen release, thus converting what could be a harmful condition into a beneficial one.
3Quantity of substance
If positive electrode material with high lithium content is used, then capacity is improved, but thermal stability deteriorates and gassing increases during high temperature storage
Solution Approach 1:
The invention applies local quality by using two positive electrode active materials with different particle sizes in specific proportions. The larger particles (1 μm to 5 μm) provide thermal stability while the smaller particles (0.5 μm to 2 μm) contribute to capacity, allowing the material to achieve high lithium content without compromising thermal stability.
Solution Approach 2:
The invention changes the particle size parameter to specific ranges which simultaneously improves capacity and maintains thermal stability. The optimized particle size distribution prevents gassing during high temperature storage while utilizing high lithium content for enhanced capacity.
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 improves the battery's capacity, output, and thermal stability, reducing gassing and maintaining performance over high-temperature cycles, while preventing structural degradation and electrolyte side reactions.
Implementation Method 1
which consist of an active material enabling the intercalation and deintercalation of a lithium ion
Implementation Method 2
which consist of an active material enabling the intercalation and deintercalation of a lithium ion
Implementation Method 3
produces electric energy through oxidation and reduction when a lithium ion is intercalated/deintercalated in/from the positive electrode and the negative electrode
Data Source
AI summary
A positive electrode material for a lithium secondary battery includes a first positive electrode active material and a second positive electrode active material, both of which are lithium composite transition metal oxides containing transition metals. The first positive electrode active material has a larger average particle size (D50) than the second positive electrode active material, wherein a ratio (Li/Me)1 of the mole number of lithium with respect to the total mole number of transition metals of the first positive electrode active material is more than 1 to 1.5 or less, and a ratio (Li/Me)2 of the mole number of lithium (Li) with respect to the total mole number of transition metals of the second positive electrode active material is 0.9 to 1. The second positive electrode active material has a crystallite size of 180 nm or more.