Mn Concentration Control in Positive Electrode Active Material
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Solution Overview
Problem
Current secondary batteries, such as lithium ion batteries, face challenges in maintaining durability and cycle characteristics for vehicle applications due to high internal resistance, which is not adequately addressed by existing positive electrode active materials.
Innovation Solution
A positive electrode active material with a lithium transition metal composite oxide having a layered rock salt structure, containing manganese, is developed, where the concentration difference between average and local maximum manganese concentrations is controlled to suppress the formation of high-resistance spinel structures, thereby reducing internal resistance and improving durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If local accumulation of Mn concentration is restrained in the lithium-containing composite oxide, then the internal resistance is reduced and cycle characteristics are improved, but the manufacturing precision requirement increases due to the need to control concentration distribution
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Mn concentration distribution parameter, specifically maintaining the concentration difference between average and local maximum Mn concentration at 4 at% or less. This parameter control prevents excessive local accumulation of Mn that would form high-resistance spinel structures, thereby reducing internal resistance and improving cycle characteristics while managing manufacturing precision requirements
Solution Approach 2:
The patent applies local quality by ensuring uniform distribution of Mn concentration throughout the lithium-containing composite oxide particles. By controlling that the local maximum Mn concentration does not excessively exceed the average concentration (difference ≤ 4 at%), the patent prevents localized formation of spinel structures in specific regions, achieving consistent low-resistance properties throughout the material volume
2Stability of the object's composition
If spinel structured composite oxide is formed locally, then the structural stability is improved, but the internal resistance increases and durability decreases
Solution Approach 1:
The patent applies parameter changes by controlling the Mn concentration parameter to prevent excessive local accumulation (concentration difference ≤ 4 at%). This control prevents the formation of spinel structured composite oxide, which would otherwise provide structural stability but cause increased internal resistance and reduced durability. The parameter control achieves an optimal balance where structural integrity is maintained without forming harmful spinel phases
Solution Approach 2:
The patent applies the blessing in disguise principle by converting the potential harm of Mn accumulation into a benefit through precise concentration control. Instead of allowing Mn to accumulate and form harmful spinel structures, the patent controls the concentration distribution (difference ≤ 4 at%) to utilize Mn's beneficial properties for structural stability while preventing its harmful effect of forming high-resistance spinel phases, thereby improving durability
Data Source
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AI summary
A technique disclosed herein provides a positive electrode active material having a granular shape and used for a positive electrode of a secondary battery. The positive electrode active material includes, as an essential component, a lithium transition metal composite oxide containing at least manganese as a transition metal element and having a layered rock salt structure. A concentration difference between an average Mn concentration and a local maximum Mn concentration is equal to or less than 4atm%, the average Mn concentration being measured based on ICP emission spectroscopic analysis of the positive electrode active material, and the local maximum Mn concentration being measured based on energy dispersive X-ray analysis with a transmission electron microscope. Selected Drawing: None