Hollow Lithium Battery Particles for Low SOC Output
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Solution Overview
Problem
Lithium rechargeable batteries experience a decline in output as the state of charge (SOC) decreases, leading to performance deterioration, especially in low SOC regions, due to slow lithium ion diffusion and increased grain boundaries in conventional active material particles.
Innovation Solution
The use of active material particles with a hollow structure formed by aggregating lithium transition metal oxide primary particles, where the ratio of full width at half maximum (A/B) in the powder x-ray diffraction pattern is less than or equal to 0.7, reducing lithium ion diffusion distance and grain boundaries, and a thin shell section surrounding the hollow section facilitates rapid ion diffusion and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional solid active material particles are used, then the battery can store sufficient energy, but the lithium ion diffusion distance is long and grain boundaries impede diffusion, causing output decline at low SOC
Solution Approach 1:
The patent employs a hollow porous structure for active material particles, where the hollow interior creates void space that reduces the effective diffusion path length for lithium ions. The porous architecture allows ions to reach active material regions more quickly, improving output characteristics at low SOC while maintaining sufficient energy storage capacity through the preserved outer shell structure.
Solution Approach 2:
The active material particles are segmented into a hollow shell structure with an interior void space. This segmentation divides the solid particle into an outer shell region and an inner hollow region, creating multiple pathways for ion diffusion and reducing the maximum diffusion distance from the particle surface to the interior active material, thereby improving productivity at low SOC.
2Quantity of substance
If the crystal thickness in the c-axis direction is increased, then energy density is improved, but lithium ion diffusion becomes slow due to long diffusion distance
Solution Approach 1:
The hollow porous structure creates an internal void that effectively reduces the diffusion distance for lithium ions. By removing material from the particle interior, the structure creates a shortcut pathway that allows ions to reach active material regions faster, maintaining high diffusion speed while preserving sufficient crystal thickness in the shell for energy density.
Solution Approach 2:
The hollow structure introduces a new spatial dimension by creating an internal void space within the particle. This dimensional change transforms the diffusion pathway from a purely radial path through solid material to a path that可以利用 the hollow space, effectively reducing the maximum diffusion distance without reducing the outer shell thickness that determines energy density.
3Stability of the object's composition
If multiple primary particles aggregate to form secondary particles, then the particle structure is stabilized, but grain boundaries increase and impede lithium ion diffusion
Solution Approach 1:
The hollow porous structure reduces the number of grain boundaries by creating a void space that separates aggregated primary particles. This porous architecture allows lithium ions to diffuse through the hollow interior without encountering multiple grain boundaries, thereby maintaining high diffusivity while preserving the structural stability provided by the aggregated particle configuration.
Solution Approach 2:
The hollow structure effectively extracts or removes the problematic grain boundary regions from the particle interior. By creating a void space, the structure eliminates the continuous network of grain boundaries that would otherwise impede ion diffusion, while the outer shell maintains the structural stability of the aggregated particle configuration.
4Quantity of substance
If the active material particle density is increased, then energy density is improved, but the diffusion distance for lithium ions increases and output characteristics deteriorate
Solution Approach 1:
The hollow porous structure resolves this contradiction by creating an internal void that reduces diffusion distance without significantly reducing the overall particle density. The porous architecture allows ions to traverse shorter paths through the hollow interior, improving power characteristics, while the maintained shell structure preserves sufficient active material volume for energy density.
Solution Approach 2:
The particle is segmented into a hollow shell configuration that separates the active material into an outer shell region. This segmentation creates a geometry where the maximum diffusion distance is reduced (from particle center to shell) while the total active material volume is preserved, thereby improving power characteristics without sacrificing energy density.
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
This configuration enables lithium rechargeable batteries to maintain high output even at low SOC levels, such as 30% or less, while preventing capacity deterioration during high-temperature storage, by ensuring rapid lithium ion diffusion and structural durability.
Implementation Method 1
diffusion of the Li ion into the interior of the crystal becomes slow... diffusion of the Li ion is impeded due to the presence of grain boundaries... Li ion diffusion distance is short as a result and diffusion of the Li ion into the interior of the crystal is then rapid
Implementation Method 2
the ratio (A/B) in the powder x-ray diffraction (x-ray diffraction using the CuKα line) pattern of the active material particles
Implementation Method 3
x-ray diffraction (x-ray diffraction using the CuKα line) pattern... full width at half maximum of the diffraction peak obtained for the (003) plane
Data Source
AI summary
The lithium rechargeable battery of the present invention is provided with a current collector and an active material layer containing active material particles 10 supported on this current collector. The active material particles 10 are secondary particles 14 in which a plurality of primary particles 12 of a lithium transition metal oxide are aggregated, and have a hollow structure that contains a hollow section 16 formed inside the secondary particle 14 and a shell section 15 that surrounds the hollow section 16. A through hole 18 that penetrates from the outside to the hollow section 16 is formed in the secondary particle 14. The ratio (A/B) in a powder x-ray diffraction pattern of the active material particles 10, where A is the full width at half maximum of the diffraction peak obtained for the (003) plane and B is the full width at half maximum of the diffraction peak obtained for the (104) plane, satisfies the equation (A/B)≦0.7.