Optimized Positive Electrode Material for High-Density Batteries
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Summary
Problems
Existing positive electrode active materials for nonaqueous electrolyte secondary batteries face challenges in achieving high energy density and cycle stability due to low fillability and increased reaction resistance caused by voids and coat layers, respectively.
Innovation solutions
A lithium-metal composite oxide with a specific particle structure, including a void ratio distribution and tap density, is developed, utilizing a crystallization process to control the morphology of the nickel-cobalt-manganese composite hydroxide, resulting in a positive electrode active material with improved charging and discharging capacities and cycle characteristics.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If the average particle diameter is reduced to 2-8 μm with narrow size distribution to improve cycle characteristic and output, then charging and discharging capacity is improved, but volume-based energy density decreases due to low fillability
Why choose this principle:
The invention segments the particle structure into hierarchical levels: secondary particles (2-8 μm) composed of multiple primary particles (0.5-2 μm), which in turn consist of finer sub-primary particles. This segmentation allows the secondary particles to maintain small overall size for good fillability and cycle characteristics, while the internal porous structure of primary particles provides high surface area for electrochemical reactions, thus resolving the contradiction between particle size and energy density.
Principle concept:
If the average particle diameter is reduced to 2-8 μm with narrow size distribution to improve cycle characteristic and output, then charging and discharging capacity is improved, but volume-based energy density decreases due to low fillability
Why choose this principle:
The invention introduces a controlled porous structure within primary particles, where the porosity ratio is specifically controlled at 10-50%. This porous structure increases the effective surface area for lithium ion insertion/extraction reactions without significantly increasing the external particle size, thereby improving volumetric energy density while maintaining the small secondary particle size needed for good fillability and cycle stability.
Application Domain
Data Source
AI summary:
A lithium-metal composite oxide with a specific particle structure, including a void ratio distribution and tap density, is developed, utilizing a crystallization process to control the morphology of the nickel-cobalt-manganese composite hydroxide, resulting in a positive electrode active material with improved charging and discharging capacities and cycle characteristics.
Abstract
Provided are a positive electrode active material with which a secondary battery having high charging and discharging capacities and an excellent cycle characteristic can be obtained, and a method for producing the same. A positive electrode active material for a nonaqueous electrolyte secondary battery includes a lithium-metal composite oxide represented by a general formula: Li a Ni x Co y Mn z M t O 2+α and containing a secondary particle formed of a plurality of flocculated primary particles. A void ratio obtained from an image analysis result of a cross section of the secondary particle, the image thereof being obtained by a scanning electron microscope, is at least 5% and up to 50% in a first area that is from a central part of the secondary particle to one half of a radius of the secondary particle, and is up to 1.5% in a second area that is outside the first area.