LNMO Cathode Forming Process for Li-ion Battery Degassing
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Solution Overview
Problem
Rechargeable lithium-ion batteries with nickel-substituted lithium manganese oxide (LNMO) cathode materials face issues of high self-discharge and degassing due to electrolyte instability at high voltages, leading to capacity drops and interface instability.
Innovation Solution
A process involving charging the battery to 100%, storing it in an open circuit for at least 48 hours, removing generated gas, and repeating this process until gas volume is below a threshold, with optional discharging and storage at controlled temperatures to stabilize the cathode/electrolyte interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional electrolytes are used with LNMO-based cathode material at high voltage, then the battery can operate at high voltage for increased energy density, but the electrolyte becomes unstable leading to strong degassing and high self-discharge
Solution Approach 1:
The patent applies preliminary action by performing a specific forming process before the battery is put into service. The process involves charging the battery to 100% state of charge, storing it in open circuit for at least 48 hours, and removing generated gas. This preliminary treatment stabilizes the cathode/electrolyte interface before normal operation, preventing excessive degassing and self-discharge during subsequent use.
Solution Approach 2:
The patent changes operational parameters by controlling the state of charge and storage time during the forming process. By charging to 100% and maintaining this state for at least 48 hours, the process optimizes the interface stabilization. The parameter of gas volume is also monitored and used as a criterion to determine when the forming process is complete (when gas volume is below a threshold).
2Reliability
If the battery is charged to 100% and stored for extended periods, then the cathode/electrolyte interface stabilizes, but gas is generated that must be removed
Solution Approach 1:
The patent converts the harmful effect of gas generation into a beneficial process indicator. The gas generated during interface stabilization is not viewed merely as a problem to be eliminated, but as a sign that the stabilization process is occurring. By monitoring gas volume and using it as a criterion for process completion (stopping when gas volume is below a threshold), the patent transforms a harmful byproduct into a useful process control parameter.
Solution Approach 2:
The patent applies the extraction principle by physically removing the generated gas from the battery during the forming process. A gas removal step is incorporated into the methodology, where gas is extracted from the battery after charging and during storage. This prevents gas accumulation that would otherwise cause swelling or safety issues, while allowing the interface stabilization to proceed.
3Reliability
If additives are introduced into the electrolyte to protect the LNMO interface, then electrolyte stability improves, but the device complexity and manufacturing complexity increase
Solution Approach 1:
The patent applies self-service by enabling the battery system to stabilize its own interface through a controlled forming process, without requiring external additives or modifications to the electrolyte composition. The high voltage LNMO cathode and conventional electrolyte system stabilizes itself through the charging-to-100%-and-holding procedure, which promotes beneficial surface reactions and SEI formation. This eliminates the need for complex electrolyte formulations with multiple additives.
Solution Approach 2:
Instead of modifying the electrolyte to protect the cathode (the conventional approach), the patent inverts the strategy by modifying the charging and storage protocol to protect the electrolyte-cathode interface. Rather than adding substances to the electrolyte, the method uses a specific electrical and temporal regimen (charging to 100%, holding for 48+ hours, gas removal) to achieve stabilization, thereby simplifying the electrolyte composition while maintaining reliability.
4Reliability
If the forming process is repeated multiple times to reduce gas volume, then the battery reaches optimal performance, but the manufacturing time increases
Solution Approach 1:
The patent implements feedback control by monitoring the gas volume generated during each forming cycle and using this information to determine when to stop the process. The gas volume measurement provides real-time feedback on the degree of interface stabilization. When the gas volume falls below a predetermined threshold, the process is terminated, indicating that optimal performance has been achieved. This feedback mechanism prevents unnecessary repetition of the forming process while ensuring adequate stabilization.
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
Significantly reduces degassing and self-discharge, enhancing electrochemical performance and stability of the Li-ion battery cell, allowing for better capacity retention and usage readiness.
Implementation Method 1
Thermodynamic reactions are then established and the first lithium ion exchanges between the electrodes take place. Products resulting from these reactions accumulate on the surface of the electrodes so as to form a layer known as the 'Solid Electrolyte Interphase' (SEI).
Data Source
AI summary
A process forms a Li-ion battery cell including an LNMO-based cathode material, an anode material, a separator and an electrolyte. The process successively includes charging the cell until the cell reaches a state of charge of 100%, storing the cell in the state of charge of 100% in an open circuit for a period of time of at least 48 hours, and removing gas generated during the charging and the storage.