Positive electrode active material of power storage device, power storage device, electrically propelled vehicle, and method for manufacturing power storage
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Solution Overview
Problem
Lithium ion batteries face challenges with low conductivity and limited performance due to the low conductivity of lithium oxide as a positive electrode active material, which restricts the improvement of power storage device characteristics.
Innovation Solution
Nano-sizing the grain size of the active material and increasing its surface area by using materials like Li(2-x)MSiO4, where M is a transition metal, and supporting the surface with a carbon material to enhance the diffusion path and conductivity, thereby improving the charging and discharging rates and capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium oxide is used as a positive electrode active material, then the battery can store large electricity with compact size, but the conductivity is low and characteristics cannot be improved
Solution Approach 1:
The patent changes the physical parameters of lithium oxide by controlling grain size (reducing to fine particles) and surface area (increasing through roughness enhancement), which transforms the material's conductivity characteristics while preserving its high capacity properties
Solution Approach 2:
The patent creates a composite structure by coating lithium oxide particles with conductive materials or forming aggregates with controlled surface roughness, combining the high capacity of lithium oxide with the conductivity of other materials
2Productivity
If grain size of active material is reduced to increase diffusion path, then charging and discharging rates improve, but manufacturing complexity increases
Solution Approach 1:
The patent segments the active material into fine-grained particles with controlled size distribution, creating numerous small diffusion paths that enable faster ion transport while using standard ceramic processing techniques to manage manufacturing complexity
Solution Approach 2:
The patent creates a porous or rough surface structure on the particles, increasing effective surface area and diffusion pathways without requiring complex nanofabrication processes, thereby improving rate characteristics with manageable manufacturing complexity
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 approach results in higher capacitance, improved charging and discharging rates, and reduced internal resistance, leading to enhanced power storage device performance.
Implementation Method 1
insertion and extraction of a lithium ion can be performed and change in a crystal structure is hardly induced by insertion and extraction of a lithium ion
Implementation Method 2
By utilizing the high conductivity of the carbon material, the internal resistance of a power storage device is reduced
Implementation Method 3
a diffusion path of a reactive material (e.g., lithium ions) is increased by nano-sizing a grain size of an active material
Data Source
AI summary
An object is to improve the characteristics of a power storage device such as a charging and discharging rate or a charge and discharge capacity. The grain size of particles of a positive electrode active material is nano-sized so that a surface area per unit mass of the active material is increased. Specifically, the grain size is set to greater than or equal to 10 nm and less than or equal to 100 nm, preferably greater than or equal to 20 nm and less than or equal to 60 nm. Alternatively, the surface area per unit mass is set to 10 m2/g or more, preferably 20 m2/g or more. Further, the crystallinity of the active material is increased by setting an XRD half width to greater than or equal to 0.12° and less than 0.17°, preferably greater than or equal to 0.13° and less than 0.16°.