High-Ni NCM Cathode Composition for Gas and Thermal Stability
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Solution Overview
Problem
Existing NCM-based lithium composite transition metal oxides, particularly those with high nickel content, suffer from structural and chemical instability, leading to gas generation, increased resistance, and reduced thermal stability due to high specific surface area and particle weakness.
Innovation Solution
A positive electrode active material is developed with a specific crystallite size of 170-300 nm, incorporating multiple dopants such as Zr, Al, Ti, and Sr, which reduces the specific surface area, enhances particle strength, and minimizes lithium by-products, thereby reducing side reactions and improving thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel content (60 mol % or more) is used in NCM-based lithium composite transition metal oxide to secure high capacity, then capacity is improved, but structural and chemical stability deteriorates and thermal stability becomes difficult to secure
Solution Approach 1:
The patent applies local quality by doping specific elements (Zr, Al, Ti, Sr, Ba, Nb, Ta) at particular sites within the NCM crystal structure. These dopants are strategically positioned to stabilize the local crystal structure around nickel atoms, preventing structural degradation while maintaining high nickel content (60 mol % or more) for high capacity.
Solution Approach 2:
The patent creates a composite material system by combining NCM-based lithium composite transition metal oxide with multiple dopant elements. This composite approach integrates the high capacity benefits of high-nickel NCM with the stabilizing effects of various dopants, achieving both high capacity and improved structural/chemical stability and thermal stability.
2Ease of manufacture
If typical NCM-based lithium composite transition metal oxide is used with aggregated primary particles forming secondary particles, then manufacturing is simplified, but specific surface area increases and particle strength decreases leading to gas generation and reduced stability
Solution Approach 1:
The patent applies parameter changes by controlling the crystallite size to a specific range (170-300 nm) and adjusting particle morphology parameters. This results in particles with reduced specific surface area and enhanced particle strength, preventing particle breakage during roll-pressing while maintaining manufacturability.
Solution Approach 2:
The patent employs beforehand cushioning by pre-strengthening particles through controlled crystallization and doping before the roll-pressing process. This prevents particle breakage and reduces the generation of lithium by-products and gas that would otherwise occur during electrode manufacturing.
3Productivity
If high specific surface area particles are used, then more active material is exposed for reactions, but gas is generated in large amount and stability is lowered when driving a cell
Solution Approach 1:
The patent changes the surface area parameter by controlling particle morphology and crystallite size to achieve an optimal balance. The resulting particles have reduced specific surface area compared to conventional materials, which suppresses gas generation and side reactions with electrolyte while maintaining sufficient reaction activity for high productivity.
4Ease of operation
If particle strength is low, then processing is easier, but particle breakage occurs during roll-pressing leading to increased resistance and reduced performance
Solution Approach 1:
The patent applies parameter changes by optimizing crystallite size (170-300 nm) and particle structure through controlled doping and heat treatment. This enhances particle strength to prevent breakage during roll-pressing, maintaining low resistance and stable performance while still allowing for effective processing.
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 solution effectively suppresses gas generation, resistance increase, and enhances thermal stability in high-Ni NCM-based lithium composite transition metal oxides, enabling their use in high-voltage lithium secondary batteries.
Implementation Method 1
A lithium secondary battery generates electric energy by an oxidation and reduction reaction when lithium ions are intercalated/deintercalated from a positive electrode and the a negative electrode
Data Source
AI summary
A lithium composite transition metal oxide includes nickel (Ni), cobalt (Co), and manganese (Mn), wherein the lithium composite transition metal oxide includes two or more elements selected from the group consisting of Zr, Al, V, Co, and Mg and additional two or more elements selected from the group consisting of Ti, Y, Sr, Nb, Ba, and Ca, and the lithium composite transition metal oxide is in a form of a particle having a crystallite size of 170-300 nm.