Pre-Lithiated Cathodes for First-Cycle Lithium Loss Compensation
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Solution Overview
Problem
Lithium-ion cells face limitations in energy density due to irreversible capacity losses during initial charge and cycling, primarily due to surface passivation and volume changes in anode materials, which reduce cyclable capacity and stability.
Innovation Solution
Chemically or electrochemically pre-lithiated cathodes with specific active materials and processes, such as Li1+aMxOy, are used to supply extra lithium, reducing thermodynamic potential and minimizing volume changes, thereby enhancing energy density and cycling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high capacity anode materials like Si are used to increase energy density, then the theoretical capacity increases significantly, but the large volume expansion (nearly 300%) causes severe surface passivation and irreversible Li consumption
Solution Approach 1:
The cathode is pre-lithiated before cell assembly by electrochemical treatment, adding extra lithium to the cathode structure. This preliminary action ensures that when the cell operates, the additional lithium compensates for the irreversible consumption at the anode, maintaining higher cyclable capacity throughout cycling.
Solution Approach 2:
The invention modifies the lithium content parameter of the cathode material by treating it with lithium metal or lithium-containing compounds under controlled conditions. This changes the stoichiometry from standard LiMO2 to Li1+aMO2 (where a>0), increasing the lithium reservoir capacity to offset anode losses.
2Loss of energy
If graphitic carbon anodes with low surface area are used to minimize passivation losses, then irreversible Li consumption is reduced, but the energy density increase is limited
Solution Approach 1:
The cathode undergoes pre-lithiation treatment before cell assembly, adding extra lithium to compensate for future irreversible losses. This allows the use of high-capacity anodes without sacrificing net energy density, as the lithium deficit is preemptively corrected.
Solution Approach 2:
The invention creates a composite system where the cathode contains both the original lithium-containing material and additional lithium phases introduced during pre-lithiation. This composite structure provides a larger lithium reservoir that can sustain higher capacity anodes.
3Reliability
If SiOx anodes are used to improve cycling efficiency, then cycle life increases, but even larger 1st cycle irreversible capacity is consumed due to oxide reduction to Li2O and lithium silicates
Solution Approach 1:
The cathode is pre-lithiated before cell assembly to add a lithium buffer. This preliminary lithium addition compensates for the severe first-cycle irreversible consumption in SiOx anodes, allowing the cell to achieve both high cycling efficiency and acceptable initial capacity.
Solution Approach 2:
The invention converts the harmful effect of large first-cycle irreversible loss into a beneficial feature by designing the cathode with excess lithium capacity. The initial capacity loss becomes a one-time cost that enables stable, efficient long-term cycling with SiOx anodes.
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 pre-lithiated cathodes increase the first charge capacity and maintain discharge capacity, improving energy density and cycle life while being less susceptible to degradation, thus overcoming the limitations of traditional anode materials.
Implementation Method 1
When the cell is charged for the first time, all the lithium that can be reversibly extracted from the cathode (or positive electrode) by electrochemical oxidation is transferred to the anode (or the negative electrode)
Implementation Method 2
pre-lithiated cathode active material has a thermodynamic potential less than 3.0 V versus Li prior to assembly into an electrochemical cell... minimizing volume changes
Data Source
AI summary
Provided are compositions, systems, and methods of making and using pre-lithiated cathodes for use in lithium ion secondary cells as the means of supplying extra lithium to the cell. The chemically or electrochemically pre-lithiated cathodes include cathode active material that is pre-lithiated prior to assembly into an electrochemical cell. The process of producing pre-lithiated cathodes includes contacting a cathode active material to an electrolyte, the electrolyte further contacting a counter electrode lithium source and applying an electric potential or current to the cathode active material and the lithium source thereby pre-lithiating the cathode active material with lithium. An electrochemical cell is also provided including the pre-lithiated cathode, an anode, a separator and an electrolyte.