Positive Electrode Precursor for Hybrid Capacitors
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Solution Overview
Problem
Current power storage systems, such as lithium ion batteries and electric double layer capacitors, face challenges in achieving high energy density, high output characteristics, and durability, particularly in hybrid electric cars and fuel cell electric cars, where existing solutions either compromise on energy density or durability.
Innovation Solution
A positive electrode precursor for nonaqueous hybrid capacitors composed of a carbon material and an alkali metal compound, specifically designed to promote the decomposition of the alkali metal compound for pre-doping lithium ions into the negative electrode, enhancing capacitance and reducing gas generation, while maintaining excellent charging and discharging cycle characteristics under high load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If activated carbon is used as electrode material for electric double layer capacitor, then high output characteristics and durability are achieved, but energy density is only about 1 to 5 Wh/L
Solution Approach 1:
The patent uses composite materials by combining activated carbon (for high output and durability) with lithium compound-containing particles (for high energy density). This composite electrode structure allows the system to achieve both high output characteristics/durability from the activated carbon and high energy density from the lithium compound particles, resolving the contradiction between these two requirements.
Solution Approach 2:
The patent changes the energy storage mechanism parameter by incorporating lithium compounds that can undergo Faraday reactions in addition to the non-Faraday adsorption/desorption of activated carbon. This parameter change enables the electrode to achieve higher energy density while maintaining the high output characteristics provided by the activated carbon matrix.
2Quantity of substance
If oxide or carbon material is used as electrode for Faraday reaction, then energy density is increased, but durability and output characteristics deteriorate
Solution Approach 1:
The patent uses activated carbon as an intermediary matrix that hosts the lithium compound particles. The activated carbon provides a stable, durable structure with high output characteristics, while the lithium compound particles embedded within it provide the Faraday reaction capability for high energy density. This intermediary structure allows the lithium compounds to deliver high energy density without sacrificing the durability and output characteristics.
Solution Approach 2:
The patent applies local quality by creating a heterogeneous electrode structure where different regions serve different functions: the activated carbon matrix provides durability and high output characteristics, while the lithium compound particles dispersed within it provide high energy density through Faraday reactions. This local differentiation of material properties resolves the contradiction between energy density and durability.
3Power
If lithium ion battery is designed for high output, then output characteristics are improved, but energy density is suppressed to equal to or lower than 100 Wh/L
Solution Approach 1:
The patent merges the advantages of electric double layer capacitors (high output characteristics) and lithium ion batteries (high energy density) into a single hybrid electrode structure. By combining activated carbon for capacitive behavior with lithium compound particles for battery-like Faraday reactions, the system achieves both high output characteristics and high energy density simultaneously, resolving the contradiction between these two parameters.
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 solution enables efficient pre-doping of lithium ions into the negative electrode, improving the energy density and output characteristics of nonaqueous hybrid capacitors, while minimizing gas generation and ensuring robust cycle performance, thus addressing the limitations of existing technologies.
Implementation Method 1
promote the decomposition of the alkali metal compound for pre-doping lithium ions into the negative electrode
Implementation Method 2
carrying out charging and discharging, not only in the positive electrode by non-Faraday reaction based on adsorption/desorption of anions but also in a negative electrode by Faraday reaction based on occlusion/releasing of lithium ions
Implementation Method 3
charging and discharging are carried out by adsorption/desorption (non-Faraday reaction) of ions at a surface of the activated carbon
Implementation Method 4
charging and discharging are carried out by Faraday reaction
Data Source
AI summary
This positive electrode precursor includes: a positive electrode active material containing a carbon material and an alkali metal compound, wherein 5≤A≤35, when A (g/m2) is a weight of the alkali metal compound in the positive electrode active material layer at one surface of the positive electrode precursor, 10≤B≤100 as well as 0.20≤A/B≤1.00, when B (g/m2) is a weight of the positive electrode active material in the positive electrode active material layer, and 1≤C≤20, when C (m2/cm2) is a specific surface area per unit area as measured by the BET method at one surface of the positive electrode precursor.