Nonaqueous Energy Storage Electrodes for Accurate SOC Detection
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Solution Overview
Problem
Nonaqueous electrolyte energy storage devices using polyanionic positive active materials and graphite struggle to detect State of Charge (SOC) accurately due to flat charge-discharge curves, which limits their input performance, especially in applications requiring high input/output performance like mild hybrid vehicles.
Innovation Solution
Incorporating a polyanionic positive active material with a specific surface area ratio of 4 or more to the average particle size of non-graphitic carbon in the negative electrode, which reduces reaction resistance and enhances input performance by creating a sloped charge-discharge curve for easier SOC detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a polyanionic positive active material and graphite are used in a nonaqueous electrolyte energy storage device, then the device achieves high energy density, but the charge-discharge curve becomes flat making SOC detection difficult and input performance is limited
Solution Approach 1:
The patent changes the particle size parameter of the negative active material from conventional graphite to fine non-graphitic carbon with average particle size of 0.6 μm or less. This parameter change transforms the flat charge-discharge curve into a sloped curve, enabling accurate SOC detection while maintaining high energy density. The specific surface area to particle size ratio (A/B) is optimized to 3 or more to achieve the desired curve slope.
2Ease of manufacture
If a polyanionic positive active material and graphite are used, then the device structure is simple and manufacturing is easy, but input performance is insufficient for high-power applications
Solution Approach 1:
The patent changes the particle size parameter of the negative active material to 0.6 μm or less, which significantly increases the specific surface area. This parameter change reduces reaction resistance and improves input performance by 20% or more, while the manufacturing process remains relatively simple using conventional techniques.
Solution Approach 2:
The patent utilizes non-graphitic carbon material with high specific surface area (20 m²/g or more) to create a porous-like structure that increases the reaction interface between the electrode and electrolyte. This enhances ion transport and reaction kinetics, significantly improving input performance while maintaining manufacturing feasibility.
3Power
If the specific surface area of the polyanionic positive active material is increased relative to the particle size of non-graphitic carbon (A/B ≥ 3), then input performance improves through reduced reaction resistance, but the device complexity increases
Solution Approach 1:
The patent optimizes the ratio of specific surface area of the positive active material to particle size of the negative active material (A/B) to be 3 or more. This parameter optimization balances the electrode characteristics to reduce reaction resistance and improve input performance, while the overall device structure remains conventional and simple.
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 configuration allows for easy detection of SOC and significantly improves input performance by reducing reaction resistance, making the energy storage device more suitable for high-performance applications.
Implementation Method 1
The nonaqueous electrolyte secondary battery is generally provided with an electrode assembly with a pair of electrodes electrically isolated by a separator, and a nonaqueous electrolyte interposed between the electrodes and is configured to be charged and discharged by transferring ions between both the electrodes.
Implementation Method 2
capacitors such as lithium ion capacitors and electric double layer capacitors are also widely used as nonaqueous electrolyte energy storage devices other than the nonaqueous electrolyte secondary batteries
Data Source
AI summary
A nonaqueous electrolyte energy storage device according to one aspect of the present invention includes: a positive electrode containing a polyanionic positive active material; and a negative electrode containing non-graphitic carbon, in which a ratio A/B of a specific surface area A (m2/g) of the polyanionic positive active material to an average particle size B (μm) of the non-graphitic carbon is 4 or more.