Two-Layer Positive Electrode for Lithium Battery Capacity Retention
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Solution Overview
Problem
Lithium batteries face challenges in achieving high capacity and power output due to the irreversibility of silicon-based composite materials used in negative electrodes, which leads to poor capacity retention and stability issues.
Innovation Solution
A positive electrode is designed with a first layer that irreversibly deintercalates lithium ions and a second layer that allows reversible intercalation and deintercalation, compensating for the irreversibility of the negative electrode by providing additional lithium ions during initial charging, thereby improving capacity retention and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based composite material is used as negative active material to achieve high capacity, then battery capacity is improved, but capacity retention deteriorates due to irreversible deintercalation
Solution Approach 1:
The first layer is designed to perform preliminary irreversible deintercalation of lithium ions during initial charging, compensating for the irreversible capacity loss that occurs in silicon-based negative electrodes. This preliminary action ensures that sufficient lithium ions are available for subsequent reversible cycling, thereby improving capacity retention while maintaining high battery capacity
Solution Approach 2:
The invention changes the operational parameters of the positive electrode by introducing a two-layer structure with different deintercalation characteristics. The first layer operates in irreversible mode to compensate for negative electrode losses, while the second layer operates in reversible mode for sustained cycling, thereby optimizing both capacity and capacity retention
2Quantity of substance
If high charging voltage is used to achieve high capacity, then battery capacity is improved, but battery stability deteriorates
Solution Approach 1:
The positive electrode employs a composite two-layer structure where the first layer uses materials suitable for high-voltage irreversible deintercalation (such as Li2NiO3, Li2MoO3, or Li2CoO3) to achieve high capacity, while the second layer uses materials optimized for reversible cycling (such as LiCoO2, LiMn2O4, or LiFePO4) to ensure stability. This composite structure allows the battery to achieve high capacity through high-voltage operation while maintaining stability through the protective reversible layer
3Reliability
If first layer is added to compensate for irreversible deintercalation, then capacity retention is improved, but electrode complexity increases
Solution Approach 1:
The positive electrode is segmented into two distinct functional layers: the first layer dedicated to irreversible deintercalation for capacity compensation, and the second layer dedicated to reversible cycling for stability. This segmentation allows each layer to be optimized for its specific function, achieving improved capacity retention while keeping the overall electrode design manageable through clear functional division
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 proposed electrode structure enhances the capacity retention and stability of lithium batteries by compensating for the irreversibility of negative electrodes, maintaining high capacity characteristics while reducing net gas generation and improving overall battery performance.
Implementation Method 1
a first layer capable of irreversible deintercalation of lithium ions
Implementation Method 2
a second layer capable of reversible intercalation and deintercalation of lithium ions
Implementation Method 3
A lithium battery converts chemical energy into electrical energy through electrochemical redox reactions between chemical substances
Data Source
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AI summary
Disclosed is a positive electrode and a lithium battery including the positive electrode. The positive electrode includes a current collector, a first layer irreversibly deintercalating lithium ions, and a second layer allowing reversible intercalation and deintercalation of lithium ions. In an embodiment, the first layer further comprises a first sublayer and a second sublayer, in which the first sublayer is interposed between the current collector and the second sublayer. The first sublayer comprises a first active material represented by Formula 1 Li 2 Mo 1-n R 1 O 3 , and the second sublayer comprises a second active material represented by Formula 2 Li 2 Ni 1-m R 2 m O 2 . In Formula 1, 0‰¤n<1; and R 1 is selected from the group consisting of manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), magnesium (Mg), nickel (Ni), and combinations of at least two of the foregoing elements. In Formula 2, 0‰¤m<1; and R 2 is selected from the group consisting of Mn, Fe, Co, Cu, Zn, Mg, Mo, and combinations of at least two of the foregoing elements.