Activated Carbon Electrode Pore Structure for Lithium Storage
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Solution Overview
Problem
Current storage elements, such as electric double-layer capacitors and lithium ion cells, face challenges in achieving a balance between high energy density, high power output, and durability, with existing solutions either compromising on energy density or output characteristics.
Innovation Solution
A non-aqueous lithium-type storage element utilizing activated carbon with a specific porous structure for the positive electrode, characterized by defined mesopore and micropore volumes, and a carbonaceous material for the negative electrode, optimized to enhance output characteristics while maintaining energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If activated carbon is used for negative electrode to increase capacitance, then energy density is improved, but charging and discharging efficiency for lithium ions decreases
Solution Approach 1:
The patent uses activated carbon with specifically controlled pore structure (mesopore volume V1 between 0.2-0.8 cm³/g and micropore volume V2 between 0.3-1.2 cm³/g) as negative electrode material. The porous structure provides both high capacitance through large surface area and efficient lithium ion transport through optimized pore channels, resolving the contradiction between energy density and charging/discharging efficiency.
Solution Approach 2:
The patent changes the physical parameters of activated carbon by controlling the ratio of mesopore volume to micropore volume (V1/V2 between 0.167-2.667). This parameter optimization allows the material to simultaneously achieve high capacitance and high lithium ion efficiency, transforming the activated carbon into a dual-functional material for both energy storage and fast ion transport.
2Quantity of substance
If graphite is used for negative electrode to increase energy density, then capacitance is improved, but lithium dendrites are generated reducing durability
Solution Approach 1:
The patent replaces graphite with activated carbon that has sufficient capacitance but avoids the dendrite formation problem entirely. The activated carbon structure inherently prevents lithium dendrite growth, providing a durable solution that maintains high capacitance without the reliability issues of graphite-based electrodes.
3Power
If lithium ion cell is designed for high power output, then output characteristics are improved, but energy density decreases to 100 Wh/L or less
Solution Approach 1:
The patent creates a composite electrode system using activated carbon with optimized pore structure that combines the high power characteristics of capacitor materials with the high energy density of battery materials. The composite pore structure (mesopores + micropores) enables both fast ion transport for high power and high lithium ion capacity for high energy density, achieving performance beyond conventional lithium ion cells.
4Quantity of substance
If electric double-layer capacitor uses nonaqueous electrolytic solution with lithium salt to increase withstand voltage, then energy density is improved, but cycle characteristic problems occur
Solution Approach 1:
The patent uses activated carbon with optimized pore structure as negative electrode material that is compatible with nonaqueous lithium-containing electrolytes. The porous structure facilitates efficient lithium ion insertion and extraction, preventing the cycle degradation problems that occur with conventional activated carbon in lithium-containing electrolytes, thereby enabling both high energy density and good cycle characteristics.
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 achieves a higher output density while maintaining high capacitance, improving the performance of storage elements in applications requiring both high power and energy density.
Implementation Method 1
activated carbon with a specific porous structure for the positive electrode, characterized by defined mesopore and micropore volumes
Implementation Method 2
when the mesopore volume relating to pores with a diameter of 2 nm (20 angstrom) or more and 50 nm (500 angstrom) or less calculated by the BJH method is defined as V1
Implementation Method 3
nonaqueous electrolytic solution containing lithium salt
Data Source
Figure 1
AI summary
This invention provides a nonaqueous lithium-type storage element using an activated carbon having a specific porous structure in a positive electrode. A storage element using a conventional carbonaceous material in a positive electrode has a problem that, although the capacitance is large, the output characteristics are disadvantageously unsatisfactory. The nonaqueous lithium-type storage element using a material, which can occlude and release lithium ions in a negative electrode, can improve output characteristics while maintaining the energy density of the storage element at a substantially equal value by using, in a positive electrode, an activated carbon, satisfying 0.3 < V1 ≤ 0.8 and 0.5 ≤ V2 ≤ 1.0 wherein V1 represents the amount of mesopores derived from pores having a diameter of not less than 20 Å and not more than 500 Å, cc/g; and V2 represents the amount of micropores derived from pores having a diameter of less than 20 Å, cc/g.