Lithium Storage Electrode Pore Structure for Low-Temperature Output
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Solution Overview
Problem
Existing non-aqueous lithium-type electricity storage elements face challenges in achieving high energy density and high output while maintaining performance in a wide temperature environment, particularly due to increased internal resistance and lithium dendrite formation at low temperatures.
Innovation Solution
The solution involves using activated carbon in the positive electrode active material with formed active sites that interact reversibly with Li ions, optimizing the mesopore and micropore volumes, and specific surface areas to enhance capacity and ion diffusivity without impairing lithium ion diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If energy density is increased by surface modification or fine pore control of positive electrode active material layer, then energy density is improved, but lithium ion diffusion is impaired and output characteristic in lowered temperature environment is reduced
Solution Approach 1:
The patent applies local quality by creating distinct pore size regions within the positive electrode active material layer. Micropores (0.003-0.05 μm) provide high surface area for lithium ion adsorption to increase energy density, while mesopores (0.05-2.0 μm) provide diffusion channels to maintain output characteristics. This spatial differentiation of pore functions resolves the contradiction between energy density and output performance.
Solution Approach 2:
The patent uses a composite pore structure combining micropores and mesopores within the same positive electrode active material layer. This composite architecture allows the material to simultaneously exhibit high capacity (from micropores) and good ion transport (from mesopores), resolving the trade-off between energy density and output characteristic.
2Productivity
If charge-discharge is carried out by non-Faraday reaction using activated carbon electrode, then output characteristic and durability are improved, but energy density is reduced
Solution Approach 1:
The patent employs porous activated carbon with a specifically controlled pore size distribution (micropores and mesopores) to increase the effective surface area available for lithium ion adsorption. This increases the capacitance and energy density while maintaining the non-Faraday reaction mechanism that provides high output and durability characteristics.
3Quantity of substance
If charge-discharge is carried out by Faraday reaction using oxide or carbon material electrode, then energy density is improved, but durability and output characteristic are reduced
Solution Approach 1:
The patent changes the pore size parameter distribution within the activated carbon material, creating a bimodal distribution with micropores for high capacity and mesopores for ion transport. This parameter optimization allows the non-Faraday reaction system to achieve energy density comparable to Faraday reaction systems while maintaining superior durability through the capacitive mechanism.
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 approach enables a non-aqueous lithium-type electricity storage element with improved energy density and output characteristics that are maintained across a wide temperature range, reducing internal resistance and preventing performance degradation.
Implementation Method 1
non-Faraday reaction by adsorption/desorption of anions similar to an electrical double layer capacitor at about 3 V or higher, at the positive electrode
Implementation Method 2
Faraday reaction by intercalation/release of lithium ions similar to a lithium ion battery, at the negative electrode
Data Source
AI summary
Provided is a non-aqueous lithium-type electricity storage element which includes a positive electrode current collector having a positive electrode active material layer disposed thereon, wherein, in a solid-state 7Li-NMR spectrum of the positive electrode active material layer, a signal area ratio a/b, which is the ratio of a signal area ratio of component A having a signal at least at -2 to 2.5 ppm to a signal area of component B having a signal at -6 to -2.5 ppm is 1.5 to 20.0.