Lithium Ion Capacitor Negative Electrode Thickness Control
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Solution Overview
Problem
Conventional lithium ion capacitors experience a reduction in capacity retention ratio and an increase in internal resistance after repeated high-load charging-discharging, and are prone to short circuits due to lithium precipitation on the negative electrode, leading to a short service life.
Innovation Solution
The lithium ion capacitor design ensures that the thickness ratios of electrode layers on the front and back surfaces of the negative electrode current collector deviate by -10 to 10% from the average, with specific thickness ranges for the current collectors and electrode layers, and a higher capacitance per unit mass of the negative electrode active material compared to the positive electrode, using materials like graphite or non-graphitizable carbon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrode layers are formed on front and back surfaces of the negative electrode current collector, then the negative electrode can support lithium ion occlusion and deocclusion, but uneven thickness distribution causes capacity retention degradation and internal resistance increase after repeated high-load charging-discharging
Solution Approach 1:
The invention specifies precise parameter ranges for electrode layer thickness (20-200 μm total sum) and thickness deviation ratio (-10 to 10%), transforming the qualitative problem of uneven thickness into a quantitative control specification. By defining these precise parameter boundaries, the invention enables consistent manufacturing quality and prevents capacity retention degradation while maintaining manufacturing feasibility.
2Power
If high-load charging-discharging is repeated many times, then high power output is achieved, but lithium precipitates on the negative electrode causing short circuit
Solution Approach 1:
The invention performs preliminary action by pre-establishing uniform electrode layer thickness distribution before the capacitor undergoes high-load charging-discharging cycles. This preliminary structural optimization prevents lithium precipitation from occurring in the first place, rather than attempting to address it after formation. The uniform thickness ensures even current distribution and prevents localized lithium deposition that would lead to short circuits.
Solution Approach 2:
The invention provides beforehand cushioning by controlling electrode layer thickness uniformity within -10 to 10% deviation, creating a buffer against the harmful effects of repeated high-load cycling. This thickness control acts as a protective measure that cushions the negative electrode structure from the stress of lithium ion insertion/extraction, preventing structural degradation and lithium precipitation that would otherwise occur under high-load conditions.
3Use of energy by moving object
If the negative electrode potential is reduced by occluding lithium ions in advance, then high energy density is achieved, but the negative electrode becomes prone to lithium precipitation and short circuit
Solution Approach 1:
The invention changes the parameter of electrode layer thickness from an uncontrolled variable to a precisely controlled parameter within 20-200 μm total thickness and -10 to 10% deviation ratio. This parameter control allows the negative electrode to achieve high energy density through lithium ion occlusion while maintaining structural integrity and preventing lithium precipitation, thus extending service life.
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 maintains a high capacity retention rate and suppresses internal resistance increase even after repeated high-load charging-discharging, preventing lithium precipitation and ensuring long service life by ensuring uniform doping and reduced lithium precipitation.
Implementation Method 1
lithium ions are occluded in and supported by a negative electrode capable of occluding and deoccluding lithium ions in advance using a chemical or electrochemical method
Implementation Method 2
electrode layers that contain a negative electrode active material and are formed on front and back surfaces of the current collector
Data Source
AI summary
Provided is a lithium ion capacitor that can maintain a high capacity retention rate and suppress an increase in internal resistance even after high-load charging-discharging is repeated many times and that has long service life because the occurrence of a short circuit due to precipitation of lithium on the negative electrode is prevented.The lithium ion capacitor comprises a positive electrode, a negative electrode, and an electrolyte solution, the negative electrode including a current collector and electrode layers that contain a negative electrode active material and are formed on front and back surfaces of the current collector, wherein, in the negative electrode, ratios of deviations of respective thicknesses of the electrode layers formed on the front and back surfaces of the current collector from an average of the thicknesses of the electrode layers to the average is −10 to 10%.