Layered NMC Cathode Composition for High-Voltage Cycle Stability
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries using lithium-nickel-manganese-containing composite oxides experience irreversible structural changes and degradation in charge-discharge cycle characteristics when charged and discharged at voltages greater than or equal to 4.8 V.
Innovation Solution
A positive electrode active material with a lithium-nickel-manganese-containing composite oxide represented by the composition formula LixNiyMnzMe1-y-zO2, with a layered structure belonging to space group R-3m and a diffraction peak at 2θ in the range of 65° to 67° in an X-ray diffraction pattern, is used to suppress degradation in charge-discharge cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If charging and discharging are performed at a charge voltage of greater than or equal to 4.8 V to increase energy density, then energy density is improved, but irreversible structural change of the composite oxide occurs resulting in degradation in charge-discharge cycle characteristics
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition parameters of the lithium-nickel-manganese-containing composite oxide. Specifically, it controls the Li/transition metal molar ratio to be greater than 0.80 and less than 0.94, the Mn/Ni molar ratio to be greater than 1.08, and the Ni atom occupancy in the Li main layer to be greater than or equal to 0.0% and less than or equal to 6.0%. These parameter optimizations enable the material to maintain structural stability even when charged at high voltages of 4.8 V or higher, thus resolving the contradiction between achieving high energy density and maintaining reliable charge-discharge cycle characteristics
Solution Approach 2:
The patent employs composite materials by creating a lithium-nickel-manganese-containing composite oxide with a specific layered rock salt structure (O3 structure). This composite material combines lithium, nickel, and manganese in optimized proportions to achieve both high capacity and structural stability. The composite structure prevents irreversible changes during high-voltage charging while maintaining the necessary electrochemical performance for high energy density applications
2Quantity of substance
If the Li/transition metal molar ratio is increased to improve capacity, then capacity is improved, but structural stability deteriorates leading to irreversible structural change
Solution Approach 1:
The patent optimizes the Li/transition metal molar ratio parameter to a specific range (greater than 0.80 and less than 0.94) that balances capacity and structural stability. This parameter optimization ensures sufficient lithium content for high capacity while preventing excessive lithium that would cause structural instability and irreversible changes during charging cycles
3Stability of the object's composition
If the Mn/Ni molar ratio is increased to suppress structural change, then structural stability is improved, but charge capacity decreases
Solution Approach 1:
The patent optimizes the Mn/Ni molar ratio to be greater than 1.08, which provides sufficient manganese content to stabilize the layered structure and prevent irreversible changes during high-voltage charging. At the same time, the ratio is controlled to maintain adequate nickel content for charge capacity, achieving a balance between structural stability and electrochemical performance
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 proposed solution effectively suppresses degradation in charge-discharge cycle characteristics even when charging and discharging are performed at a charge voltage of greater than or equal to 4.8 V, maintaining the stability of the crystal structure and improving the occupancy of metal elements in the Li layer.
Implementation Method 1
a non-aqueous electrolyte secondary battery, which includes a positive electrode, a negative electrode, and a non-aqueous electrolyte and in which lithium ions or the like are moved between the positive electrode and the negative electrode to perform charging and discharging
Implementation Method 2
has a diffraction peak at 2θ in the range of greater than or equal to 65° and less than or equal to 67° in an X-ray diffraction pattern
Data Source
AI summary
A positive electrode active material for a non-aqueous electrolyte secondary battery contains a lithium-nickel-manganese-containing composite oxide which is represented by composition formula LixNiyMnzMe1-y-zO2 (where Me is a metal element other than Li, Ni, and Mn, x≤1.16, 0.3≤y≤0.7, and 0.3≤z≤0.7), has a layered structure belonging to space group R-3m, and has a diffraction peak at 2θ in the range of greater than or equal to 65° and less than or equal to 67° in an X-ray diffraction pattern when charging and discharging are performed until the charge voltage reaches 4.8 V.