Positive Electrode Active Material with Dual-Phase Lithium Diffusion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lithium composite transition metal oxides for batteries face challenges in achieving high capacity and stability due to limitations in lithium diffusivity and cation mixing, leading to reduced energy density and cycle characteristics.
Innovation Solution
A lithium composite oxide is developed with a multi-phase mixture of first particles having a crystal structure belonging to space group R-3m and second particles with a crystal structure belonging to space group C2/m, featuring a larger amount of cation mixing and smaller particle size, which enhances lithium diffusivity and stability, thereby improving battery capacity and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a lithium composite transition metal oxide with single-phase crystal structure is used, then the manufacturing process is simple, but the battery capacity and energy density are limited due to insufficient lithium diffusivity
Solution Approach 1:
The patent employs a composite material strategy by creating a multi-phase lithium composite oxide containing both R-3m and C2/m crystal structures. The C2/m phase provides extensive three-dimensional lithium diffusion paths that significantly enhance lithium diffusivity and battery capacity, while the R-3m phase maintains structural stability. This composite phase structure resolves the contradiction by achieving high capacity through optimized lithium ion transport without complicating the fundamental manufacturing process.
Solution Approach 2:
The patent applies local quality by creating regions with different crystal structures within the lithium composite oxide. The C2/m phase is specifically engineered to provide three-dimensional lithium diffusion paths in regions where high lithium diffusivity is needed, while the R-3m phase is maintained in regions where structural stability is critical. This spatial differentiation of crystal phases allows simultaneous optimization of both lithium diffusivity and structural integrity.
2Quantity of substance
If cation mixing is increased to improve capacity, then more lithium sites are available for insertion/extraction, but the crystal structure stability deteriorates leading to poor cycle characteristics
Solution Approach 1:
The patent implements local quality by assigning different crystal structures to different phases within the composite material. The C2/m phase is designed with higher cation mixing to maximize lithium insertion/extraction capacity in regions where this function is prioritized, while the R-3m phase maintains lower cation mixing to preserve crystal structure stability in regions where structural integrity is critical. This phase-separated approach allows both high capacity and good cycle characteristics.
Solution Approach 2:
The composite lithium composite oxide combines two phases with complementary properties: the C2/m phase contributes high lithium capacity through enhanced cation mixing and three-dimensional diffusion paths, while the R-3m phase contributes structural stability through its ordered crystal structure. The synergistic combination resolves the contradiction between capacity and stability that cannot be achieved in single-phase materials.
3Area of stationary object
If particle size is reduced to increase surface area and reaction sites, then battery capacity improves, but the amount of cation mixing increases excessively causing structural instability
Solution Approach 1:
The patent applies local quality by controlling particle size and cation mixing distribution across different phases. Smaller particles with higher surface area are formed in the C2/m phase where high reactivity is desired, while the R-3m phase maintains a more ordered structure with controlled cation mixing even in smaller particles. This phase-dependent control allows maximizing surface area for capacity while preventing excessive cation mixing that would destabilize the crystal structure.
Solution Approach 2:
The composite structure allows the material to benefit from small particle size effects (increased surface area and reaction sites) while the R-3m phase provides a stabilizing influence that prevents excessive cation mixing. The two-phase system thus achieves high surface area-to-volume ratio for improved capacity while maintaining overall structural stability through the presence of the ordered R-3m phase.
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 lithium composite oxide achieves a higher capacity and longer battery life by providing extensive three-dimensional lithium diffusion paths and maintaining structural stability during charging and discharging, resulting in improved energy density and cycle characteristics.
Implementation Method 1
providing extensive three-dimensional lithium diffusion paths
Implementation Method 2
In the X-ray diffraction pattern of the lithium composite oxide, the ratio (I020/I003) of the integrated intensity (I020) of the peak from the (020) plane to the integrated intensity (I003) of the peak from the (003) plane
Data Source
AI summary
A positive electrode active material according to the present disclosure includes a lithium composite oxide that contains first particles having a crystal structure belonging to space group R-3m and second particles having a crystal structure belonging to space group C2/m. The crystal structure of the second particles has a larger amount of cation mixing than the crystal structure of the first particles. The second particles have a smaller particle size than the first particles. Mathematical Formula 0.05≤integrated intensity ratio I(18°-20°)/I(43°-46°)≤0.99 is satisfied. The integrated intensity ratio I(18°-20°)/I(43°-46°) is a ratio of the integrated intensity I(18°-20°) to the integrated intensity I(43°-46°). The integrated intensity I(A°-B°) is the integrated intensity of a maximum peak present in the range of angle of diffraction 2θ greater than or equal to A° and less than or equal to B° in the X-ray diffraction pattern of the lithium composite oxide.