Multi-Doped High-Ni NCM Cathode for Low By-Products and Stability
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Solution Overview
Problem
High-Ni NCM-based lithium composite transition metal oxides used in lithium secondary batteries face issues with stability, specific surface area, particle strength, lithium by-product content, and thermal stability, leading to increased gas generation and resistance, especially when used in high-capacity applications.
Innovation Solution
A lithium composite transition metal oxide is developed with a crystallite size of 170-300 nm, incorporating multiple dopants such as Zr, Al, V, Co, Mg, Ti, Y, Sr, Nb, Ba, and Ca to reduce specific surface area, enhance particle strength, and minimize lithium by-products, achieved through a primary and secondary firing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the nickel content is increased to secure high capacity, then the capacity is improved, but the structural and chemical stability deteriorates and thermal stability becomes difficult to secure
Solution Approach 1:
The patent applies local quality by introducing dopant elements (Al, Ti, V, Zr, Nb, Sr, Ba, Ca, Mg, Y) at specific locations (surface and bulk) of the NCM particles. These dopants are concentrated at the particle surface and grain boundaries to locally enhance stability without reducing the overall high nickel content in the bulk material, thus maintaining high capacity while improving structural and chemical stability.
Solution Approach 2:
The patent creates a composite material system by combining high-Ni NCM with multiple dopant elements. The dopants form a composite structure where the base NCM provides high capacity while the dopant-containing phases (such as spinel-like or rock-salt structures) provide structural stability and thermal resistance, resolving the contradiction between high nickel content and stability.
2Quantity of substance
If the specific surface area is large due to aggregated primary particles, then the capacity is improved, but particle strength decreases and lithium by-products increase
Solution Approach 1:
The patent segments the particle structure into primary particles (maintaining small size for high capacity) and secondary particles (aggregates providing strength). The primary particles are kept small to maintain high specific capacity, while they are aggregated into secondary particles with controlled morphology to provide mechanical strength and reduce lithium by-product formation, thus resolving the contradiction between capacity and particle strength.
3Quantity of substance
If the specific surface area is large, then the capacity is improved, but the content of lithium by-products increases leading to side reactions with electrolyte
Solution Approach 1:
The patent creates an inert environment by forming a dopant-rich surface layer that acts as a protective barrier between the reactive high-Ni NCM bulk and the electrolyte. This surface layer, containing elements like Al, Ti, and other dopants, reduces the chemical reactivity and suppresses lithium by-product formation, thereby reducing side reactions while maintaining high capacity through the underlying high-Ni structure.
4Quantity of substance
If the crystallite size is small, then the capacity is improved, but the particle strength decreases making roll-pressing difficult
Solution Approach 1:
The patent applies the nested doll principle by nesting small crystallites (providing high capacity) within larger particle structures (providing strength). The small crystallites are aggregated into larger secondary particles with controlled morphology, creating a hierarchical structure where the outer shell provides mechanical strength for roll-pressing while the inner crystallites maintain high specific 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
The solution improves stability, reduces gas generation, and suppresses resistance increase, enabling the use of high-Ni NCM-based materials in high-voltage lithium secondary batteries with enhanced thermal and structural stability.
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
Implementation Method 2
A positive electrode active material precursor including nickel (Ni), cobalt (Co), and manganese (Mn), a lithium raw material, and at least two kinds of first dopant raw materials selected from the group consisting of Zr, Al, V, Co, and Mg, and subjecting the mixture to primary firing, and after the primary firing, mixing at least two kinds of second dopant raw materials selected from the group consisting of Ti, Y, Sr, Nb, Ba, and Ca, and subjecting the mixture to secondary firing
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 kinds of first dopants selected from the group consisting of Zr, Al, V, Co, and Mg and two or more kinds of second dopants selected from the group consisting of Ti, Y, Sr, Nb, Ba, and Ca, and particles of the lithium composite transition metal oxide has a crystallite size of 170-300 nm.