Lithium Ion Capacitor Pre-Doping via Segmented Current Collector
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Solution Overview
Problem
Existing lithium-ion capacitor technologies face challenges in achieving uniform pre-doping due to the limitations of porous current collectors, leading to inefficient lithium ion transfer and inconsistent cell performance, which affects the cycle life and series connectivity of capacitors.
Innovation Solution
A pre-doping formation method involving a face-to-face arrangement of a third metal lithium electrode and the cell, with lithium-intercalating the negative electrode using lithium-intercalated oxide from the positive electrode, and supplementing lithium ions using a third electrode, ensuring uniform lithium distribution and potential balancing across the electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous current collector is used for pre-doping, then lithium ion transfer is enabled, but the mechanical strength and electrical conductivity deteriorate, and the cost increases
Solution Approach 1:
The current collector is divided into two distinct parts: a non-porous current collector providing mechanical support and electrical conductivity, and a separate porous layer (aluminum foil with porous coating or porous polymer film) that enables lithium ion transfer. This segmentation allows each component to optimize its specific function without compromising the other.
Solution Approach 2:
A porous layer acts as an intermediary between the non-porous current collector and the electrode. This intermediate layer provides the necessary porosity for lithium ion diffusion while the underlying non-porous current collector maintains structural integrity and electrical conductivity.
2Productivity
If excessive holes are formed in the porous current collector, then pre-doping speed increases, but the mechanical strength deteriorates
Solution Approach 1:
The system separates the structural support function (non-porous current collector) from the ion transport function (porous layer). This allows the porous layer to have high porosity for fast lithium ion diffusion without compromising the mechanical strength provided by the non-porous current collector.
3Strength
If a non-porous current collector is used, then mechanical strength and electrical conductivity are maintained, but pre-doping uniformity deteriorates
Solution Approach 1:
A porous layer is introduced as an intermediary between the non-porous current collector and the electrode. This porous intermediate layer ensures uniform lithium ion distribution during pre-doping while the non-porous current collector beneath it maintains mechanical strength and electrical conductivity.
Solution Approach 2:
Different regions of the current collector system have different properties: the porous layer provides high porosity and uniform ion distribution where needed, while the non-porous current collector provides structural support and conductivity in the underlying region.
4Quantity of substance
If lithium plates are used for pre-doping, then lithium source is provided, but the potential matching between positive and negative electrodes deteriorates
Solution Approach 1:
The positive electrode itself serves as the lithium source through its lithium-containing oxide material. During pre-doping, lithium ions are extracted from the positive electrode and inserted into the negative electrode, achieving both lithium transfer and potential matching within the same system without requiring external lithium plates.
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 method stabilizes and uniformizes the doping process, prolongs the cycle life of the capacitor, improves consistency, and facilitates module and system assembly by balancing lithium-containing oxide and active carbon potentials.
Implementation Method 1
the positive electrode provides lithium ions to the negative electrode during charging
Implementation Method 2
the lithium ions in the negative electrode return to the positive electrode during discharging
Implementation Method 3
supplementing, by the third metal lithium electrode, lithium ions to the metal oxide in a lithium-deintercalated state of the positive electrode
Data Source
Figure 1
AI summary
The present invention relates to a lithium ion capacitor and a formation method thereof. A positive electrode of the capacitor comprises porous carbon and lithium-intercalated metal oxide, and a negative electrode thereof is carbon difficult to graphitize. The metal lithium electrode and a cell are arranged in a face-to-face manner and separated by separator. A current collector adopts a porous current collector. During formation, the lithium-intercalated oxide in the positive electrode is used as a lithium source to intercalate lithium into the negative electrode, and a third electrode lithium plate is used for supplementing lithium ions to the metal oxide in a lithium-deintercalated state of the positive electrode. The lithium ion capacitor is formed in two steps, so that the doping of the negative electrode is more stable, efficient and uniform, the cycle life of the capacitor can be prolonged, the consistency of the capacitor can be improved, and the assembling of a module and a system can be facilitated.