Lithium Ion Capacitor Non-Graphitizable Carbon Electrode
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Solution Overview
Problem
Lithium ion capacitors face challenges with high energy density, high output characteristics, and long-term sustainability, particularly in large capacity cells where uniform lithium ion doping is difficult and internal resistance is high.
Innovation Solution
A lithium ion capacitor design featuring a negative electrode made of non-graphitizable carbon with a specific hydrogen-to-carbon ratio, a positive electrode capable of reversible lithium and anion storage, and a non-protonic organic solvent electrolyte, where lithium ions are pre-doped to achieve low negative electrode potential and enhanced endurance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium ion is doped to negative electrode in large capacity cells, then energy density is improved, but uniformity of doping is poor and internal resistance increases
Solution Approach 1:
The patent applies preliminary doping of lithium ions to the negative electrode before final cell assembly. By pre-doping the carbon material with lithium ions and controlling the hydrogen-to-carbon ratio to 0.05 or less, the system achieves uniform distribution of lithium ions throughout the negative electrode structure, eliminating the non-uniformity problem that occurs when doping is attempted after cell assembly in large capacity devices.
2Use of energy by moving object
If hydrogen to carbon ratio in non-graphitizable carbon is reduced, then negative electrode potential is lowered and energy density is improved, but internal resistance increases
Solution Approach 1:
The patent optimizes the hydrogen-to-carbon ratio parameter of non-graphitizable carbon to 0.05 or less, which lowers the negative electrode potential and increases energy density. Simultaneously, the patent controls the doping amount of lithium ions and the structural parameters of the carbon material to maintain adequate electrical conductivity, thus resolving the contradiction between energy density improvement and internal resistance increase.
3Quantity of substance
If lithium ion capacitor is designed for high energy density, then capacitance is improved, but output characteristics deteriorate
Solution Approach 1:
The patent uses non-graphitizable carbon with controlled hydrogen-to-carbon ratio as the negative electrode material, which provides both high capacitance through increased lithium ion doping capacity and good output characteristics through maintained electrical conductivity. The specific composition control enables the material to exhibit both high energy density and excellent rate performance, resolving the contradiction between capacitance and power output.
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 design achieves higher withstand voltage, capacitance, energy density, and lower internal resistance, ensuring long-term sustainability and improved performance in large capacity cells.
Implementation Method 1
a negative electrode made of a material capable of reversibly carrying lithium ion
Implementation Method 2
a non-protonic organic solvent electrolytic solution of a lithium salt as an electrolyte
Implementation Method 3
a non-protonic organic solvent electrolytic solution of a lithium salt as an electrolyte
Data Source
AI summary
A lithium ion capacitor is provided with a positive electrode made of a material capable of reversibly carrying lithium ion and/or anion, a negative electrode made of a material capable of reversibly carrying lithium ion and an electrolytic solution made of a non-protonic organic solvent electrolytic solution of a lithium salt. (a) A negative electrode active material is non-graphitizable carbon that has a ratio of number of hydrogen atoms to number of carbon atoms of zero or more and less than 0.05. (b) Lithium ion is doped in advance to a negative electrode and/or positive electrode so that a negative electrode potential when a cell is discharged to a voltage one half a charging voltage of the cell may be 0.1.5 V or less to a metal lithium potential.