Hard Carbon Metal-Ion Capacitor with Cathode Pre-Doping Salt
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Solution Overview
Problem
Metal ion capacitors, particularly lithium ion capacitors, face limitations due to irreversible charge loss and complex manufacturing processes, especially when using hard carbons as anodes, which require high prelithiation and pose safety hazards, and existing solutions like sacrificial salts are costly and affect cyclability.
Innovation Solution
A metal ion capacitor design utilizing a hard carbon anode and an activated carbon cathode with a sacrificial salt, such as squarate, oxalate, or ketomalonate, mixed with conducting carbon, to achieve efficient pre-doping and compensate for solid electrolyte interphase formation, allowing for scalable and safer production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If hard carbon is used as negative electrode to achieve high energy density, then energy density is improved, but irreversible capacity loss increases due to high pre-lithiation requirements
Solution Approach 1:
The patent applies preliminary action by incorporating sacrificial salt into the positive electrode before device assembly. This sacrificial salt releases metal ions during initial cycles to compensate for the irreversible capacity loss of hard carbon, enabling the anode to achieve its full theoretical capacity without requiring external pre-lithiation steps.
Solution Approach 2:
The sacrificial salt acts as an intermediary substance that mediates between the hard carbon anode and the electrolyte. It provides a controlled source of metal ions that compensate for SEI formation losses, thereby enabling the hard carbon to function at its full potential while maintaining charge balance in the device.
2Use of energy by moving object
If metallic lithium is used for pre-lithiation of hard carbon to achieve high energy density, then energy density is improved, but safety hazards and manufacturing complexity increase
Solution Approach 1:
The patent employs sacrificial salt as a disposable, non-reactive alternative to metallic lithium. The sacrificial salt is consumed during initial cycles to provide the necessary lithium ions, after which it serves no further function. This approach eliminates the safety hazards associated with handling and storing reactive metallic lithium while achieving the same pre-lithiation effect.
Solution Approach 2:
The invention extracts the essential function of metallic lithium (providing lithium ions for SEI formation and capacity compensation) and separates it from the harmful properties (high reactivity and safety risks). The sacrificial salt provides only the necessary lithium ion source without the dangerous characteristics of metallic lithium, thereby eliminating safety hazards while maintaining energy density benefits.
3Duration of action of stationary object
If sacrificial salt is added to positive electrode to compensate irreversible capacity, then cyclability is improved, but manufacturing cost increases
Solution Approach 1:
The patent optimizes the concentration of sacrificial salt in the positive electrode to achieve the minimum necessary amount for compensating irreversible capacity loss. By carefully controlling the salt content parameter, the invention achieves full cyclability benefits while minimizing the additive cost and maintaining ease of manufacturing through simple mixing processes.
4Power
If hard carbon anode is used to achieve high power density, then power density is improved, but manufacturing complexity increases due to pre-lithiation requirements
Solution Approach 1:
The patent merges the pre-lithiation function with the positive electrode composition by incorporating sacrificial salt directly into the cathode mixture. This eliminates the need for separate pre-lithiation steps or additional manufacturing complexity, as the sacrificial salt is simply mixed with the activated carbon and other electrode components using standard procedures.
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 design enhances power capabilities, achieves superior mass balances, and is compatible with industrial-scale fabrication, overcoming the limitations of graphite-based capacitors by providing higher energy and power densities while ensuring safety and cost-effectiveness.
Implementation Method 1
a positive electrode which comprises an activated carbon and a sacrificial salt mixed with a conducting carbon to obtain a carbon coating on the salt
Implementation Method 2
a sacrificial salt mixed with a conducting carbon to obtain a carbon coating on the salt
Implementation Method 3
supercapacitors store charge by means of capacitive reactance allowing high power and long cyclability
Data Source
Figure 1a~1c
Figure 2a~2f
Figure 3a~3f
AI summary
The present invention relates to a metal ion capacitor with outstanding power capabilities comprising a negative electrode based on hard carbon (HC) and a positive electrode based on a combination of activated carbon (AC) and a sacrificial salt selected from the group consisting of squarate, oxalate, ketomalonate and di- ketosuccinate or a combination thereof. The sacrificial salt is added to AC in the positive electrode as a source of metal ions for pre-doping the HC and to efficiently compensate its high irreversible capacity by providing the metal ions necessary for the formation of solid electrolyte interphase (SEI) on the hard carbon, allowing for a 1:1 and superior mass balances between anode and cathode. Advantageously, the extraordinary performance of this approach has been successfully demonstrated not only in lithium ion capacitors (LICs) but also in other metal ion capacitors such as sodium and potassium ion capacitors.