Nickel Layered Cathode Surface Chemistry for High-Voltage Cycle Life
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Solution Overview
Problem
Existing positive-electrode active materials for nonaqueous electrolyte secondary batteries face challenges in maintaining high charge/discharge capacities while achieving favorable cycle characteristics at high voltages, due to the need for large amounts of aluminum additives which can reduce capacity.
Innovation Solution
A positive-electrode active material comprising lithium transition metal composite oxide particles with a layered structure containing nickel, and surface-adhering oxides of lithium and aluminum, and lithium and boron, where the aluminum is present as a solid solution in the surface layer of primary particles and the content ratio of the oxide containing lithium and aluminum to the oxide containing lithium and boron is 1 or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large amounts of aluminum additives are used to achieve favorable cycle characteristics at high voltage, then cycle characteristics are improved, but charge/discharge capacity is reduced
Solution Approach 1:
The patent applies local quality by creating a concentrated aluminum-rich surface layer on the positive electrode active material particles. Aluminum is selectively accumulated at the particle surfaces through controlled heat treatment, forming a protective shell that improves cycle characteristics without requiring bulk aluminum addition. This localized aluminum distribution protects the particle surfaces from degradation while minimizing the overall aluminum content, thereby maintaining high charge/discharge capacity.
Solution Approach 2:
The patent utilizes parameter changes by controlling the heat treatment temperature and duration to regulate aluminum diffusion and redistribution. By optimizing the heat treatment parameters (temperature range and time), aluminum ions are mobilized and re distributed to form the desired surface-enriched configuration. This parameter control enables precise adjustment of the aluminum concentration gradient, achieving favorable cycle characteristics while minimizing capacity loss.
2Reliability
If aluminum content is increased to improve cycle characteristics, then cycle stability is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent merges the cycle stability function and aluminum distribution control into a single heat treatment step. By combining aluminum diffusion, surface enrichment, and phase stabilization into one integrated thermal processing operation, the manufacturing process avoids multiple separate steps for aluminum addition and surface modification. This unified approach simplifies manufacturing while achieving the desired aluminum distribution for improved cycle stability.
Solution Approach 2:
The patent applies self-service by utilizing the aluminum already present in the positive electrode active material composition. Instead of requiring separate aluminum addition steps, the existing aluminum content is redistributed and concentrated at particle surfaces through heat treatment. This self-organizing process eliminates the need for complex multi-step manufacturing procedures while achieving the aluminum-rich surface configuration necessary for cycle stability.
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 enables nonaqueous electrolyte secondary batteries to exhibit excellent cycle characteristics at high voltage while minimizing capacity reduction, through the effective use of aluminum and boron oxides on the surface of the lithium transition metal composite oxide particles.
Implementation Method 1
the lithium transition metal composite oxide particles include secondary particles formed by aggregation of primary particles containing a solid solution of aluminum in a surface layer
Implementation Method 2
an oxide containing lithium and aluminum and an oxide containing lithium and boron adhering to a surface of the lithium transition metal composite oxide particles
Implementation Method 3
heat-treating the provided mixture. The aluminum compound has a volume-based particle diameter distribution in which a total volume percentage of particles having a particle diameter of 0.4 μm to 3.0 μm is greater than 54%
Data Source
Figure 1A~1D
Figure 2~3
Figure 4~5
AI summary
Provided is a positive-electrode active material for a nonaqueous electrolyte secondary battery, including a lithium transition metal composite oxide particle having a layered structure and containing nickel, and an oxide containing lithium and aluminum and an oxide containing lithium and boron adhering to a surface of the lithium transition metal composite oxide particle. The lithium transition metal composite oxide particle includes a secondary particle formed by aggregation of primary particles containing a solid solution of aluminum in a surface layer. The lithium transition metal composite oxide particles have a composition with a difference of more than 0.22 mol% and less than 0.6 mol% between a ratio of the number of moles of aluminum in the solid solution in the surface layer of the primary particles relative to a total number of moles of metal other than lithium and a ratio of the number of moles of aluminum present in a region other than the surface layer of the primary particles relative to the total number of moles of metal other than lithium.