Pre-lithiated Graphite Anodes for Hybrid Battery-Capacitor Cells
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Solution Overview
Problem
In hybrid lithium-ion battery/capacitor cells, the initial irreversible consumption of lithium ions during cell formation reduces the capacity and performance of the lithium-ion capacitor (LIC) due to the absence of lithium content in the activated carbon capacitor, leading to a capacity mismatch between the graphite anode and the activated carbon cathode.
Innovation Solution
The graphite anodes are pre-lithiated to form a solid electrolyte interface (SEI) before assembly, eliminating the need for additional lithium ion consumption during cell formation and ensuring stable lithium intercalation and de-intercalation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If graphite anodes are used in hybrid lithium-ion battery/capacitor cells, then the cell can provide both battery and capacitor functions, but initial irreversible consumption of lithium ions during cell formation reduces the capacity and performance of the lithium-ion capacitor unit
Solution Approach 1:
The graphite anodes are pre-lithiated before assembly into the hybrid cell by exposing them to lithium ions in a formation process. This preliminary action ensures that the graphite anodes have sufficient lithium content before being assembled with the activated carbon capacitor cathode, preventing capacity mismatch and performance degradation during cell operation
2Power
If activated carbon capacitor cathode is used in the hybrid cell, then high power density and energy density can be achieved, but capacity mismatch with graphite anode occurs due to absence of lithium content in activated carbon
Solution Approach 1:
The graphite anodes undergo pre-lithiation treatment before assembly, where they are exposed to lithium ions to form solid electrolyte interface (SEI) and store lithium content. This preliminary action ensures capacity compatibility between the graphite anode and activated carbon capacitor cathode, enabling the hybrid cell to achieve both high power density and energy density without capacity mismatch issues
3Reliability
If pre-lithiation of graphite anodes is performed, then initial lithium ion consumption is reduced and cell performance is improved, but additional process steps are required
Solution Approach 1:
The graphite anodes are pre-lithiated in a controlled process before assembly into the hybrid cell. This preliminary treatment involves exposing the graphite anodes to lithium ions to form SEI and store lithium content, which eliminates the need for additional lithium consumption during cell formation and ensures optimal cell performance from the first cycle
Solution Approach 2:
The pre-lithiation process enables the graphite anodes to self-regulate their lithium content before assembly, ensuring they have sufficient lithium reserves to match the activated carbon capacitor cathode capacity. This self-service approach simplifies the overall cell design by eliminating the need for complex lithium management systems during operation
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
Pre-lithiation of graphite anodes enhances the capacity and performance of hybrid lithium-ion battery/capacitor cells by reducing initial lithium ion consumption and maintaining reversible lithium intercalation, thereby improving the overall cell performance.
Implementation Method 1
The graphite anodes are pre-lithiated to form a solid electrolyte interface (SEI) before assembly, eliminating the need for additional lithium ion consumption during cell formation and ensuring stable lithium intercalation and de-intercalation processes
Implementation Method 2
During this initial charging step, solvated lithium ions intercalate into the graphite particles of the anodes
Implementation Method 3
such carbon particles are prepared with high levels of porosity which enable them to adsorb and desorb suitable ions during their capacitor function in the hybrid electrochemical cell
Data Source
AI summary
A hybrid lithium-ion battery/capacitor cell comprising at least a pair of graphite anodes assembled with a lithium compound cathode and an activated carbon capacitor electrode can provide useful power performance properties and low temperature properties required for many power utilizing applications. The graphite anodes are formed of porous layers of graphite particles bonded to at least one side of current collector foils which face opposite sides of the activated carbon capacitor. The porous graphite particles are pre-lithiated to form a solid electrolyte interface on the anode particles before the anodes are assembled in the hybrid cell. The pre-lithiation step is conducted to circumvent the irreversible reactions in the formation of a solid electrolyte interface (SEI) and preserve the lithium content of the electrolyte and lithium cathode during formation cycling of the assembled hybrid cell. The pre-lithiation step is also applicable to other anode materials that benefit from such pre-lithiation.