Pre-lithiation of Lithium Ion Capacitor Anodes
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Solution Overview
Problem
Existing lithium ion capacitors face challenges in achieving uniform and stable solid-electrolyte interphase layers, leading to reduced capacitance, increased equivalent series resistance, and poor cycling performance due to inadequate control over the pre-doping process of lithium ions into the anode.
Innovation Solution
A method involving pre-doping the anode of a lithium ion capacitor by immersing it and a dopant source in an electrolyte, applying a constant current or voltage to achieve a desired potential difference and pre-doping level, which forms a homogeneous and stable solid-electrolyte interphase layer, thereby improving capacitor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pre-doping methods are used to form solid-electrolyte interphase layer, then lithium ions can be transported to the anode, but the layer is non-uniform and unstable leading to poor capacitance and high equivalent series resistance
Solution Approach 1:
The patent applies preliminary action by pre-doping the anode with lithium ions before the capacitor is assembled and before normal operation begins. The method involves immersing the anode in an electrolyte solution containing lithium ions and applying a constant current or voltage to facilitate lithium ion insertion into the anode structure. This preliminary lithium ion insertion creates a stable solid-electrolyte interphase layer in advance, ensuring uniformity and stability before the capacitor enters service, thereby resolving the contradiction between reliability and manufacturing precision.
2Reliability
If conventional pre-doping methods are used, then lithium ion transport is enabled, but equivalent series resistance increases due to inadequate control over the pre-doping process
Solution Approach 1:
The patent applies parameter changes by precisely controlling key parameters of the pre-doping process: applying a constant current or constant voltage within specific ranges, controlling the temperature during pre-doping, and regulating the concentration of lithium ions in the electrolyte solution. By optimizing these parameters, the method achieves uniform lithium ion distribution and stable solid-electrolyte interphase layer formation, thereby reducing equivalent series resistance and improving capacitor performance while maintaining manageable process complexity.
3Stability of the object's composition
If lithium ions are not adequately pre-doped into the anode, then the anode structure remains unstable, but achieving proper pre-doping is difficult with existing methods
Solution Approach 1:
The patent applies self-service by utilizing the electrolyte solution that is already present in the capacitor assembly process as the source of lithium ions for pre-doping. The anode is immersed in this electrolyte solution, and through controlled application of constant current or voltage, lithium ions naturally migrate from the electrolyte into the anode structure. This self-service approach eliminates the need for separate lithium ion insertion equipment or complex external lithium sources, making the pre-doping process easier to manufacture while achieving stable anode composition.
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 method results in improved capacitance, reduced equivalent series resistance, and enhanced cycling performance by achieving a uniform and stable solid-electrolyte interphase layer, with controlled pre-lithiation levels facilitating better lithium ion access and capacitor reliability.
Implementation Method 1
A non-aqueous electrolyte conductive of lithium ions is provided. A constant or substantially constant voltage is applied across the anode and the dopant source for a duration of time such that a solid-electrolyte interphase layer forms adjacent a surface of the anode
Implementation Method 2
The solid-electrolyte interphase layer may form at least in part due to an electrochemical reaction at the anode surface involving an electrolyte solvent and/or an electrolyte salt
Data Source
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AI summary
A method of pre-doping an anode of an energy storage device can include immersing the anode and a dopant source in an electrolyte, and coupling a substantially constant current between the anode and the dopant source. A method of pre-doping an anode of an energy storage device can include immersing the anode and a dopant source in an electrolyte, and coupling a substantially constant voltage across the anode and the dopant source. An energy storage device can include an anode having a lithium ion pre-doping level of about 60% to about 90%.