Secondary Battery Ion Trapping for Transition Metal Stability
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Solution Overview
Problem
Secondary batteries face issues with transition metal ion dissolution leading to structural instability and performance degradation due to catalysis of electrolyte decomposition and negative electrode interface film, necessitating improved cycle performance.
Innovation Solution
Incorporating an ion trapping agent with a reduction potential of 0-2 V relative to lithium metal in the positive electrode, separator, or negative electrode of the secondary battery to trap transition metal ions and reduce H+ in the electrolyte, preventing their catalytic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transition metal ions are present in the electrolyte, then the battery can operate, but the transition metal ions catalyze electrolyte decomposition and interface film degradation, leading to reduced cycle performance
Solution Approach 1:
The patent introduces an ion trapping agent as an intermediary substance that selectively captures transition metal ions (Fe2+, Mn2+, Ni2+, Co2+) from the electrolyte. This mediator prevents the harmful catalytic action of these ions on the electrolyte and interface films, thereby improving cycle performance without affecting normal battery operation.
Solution Approach 2:
The patent converts the harmful presence of transition metal ions into a beneficial effect by using their reducibility. The ion trapping agent reduces these ions to lower valence states that are less catalytically active, thereby transforming the harmful catalytic property into a beneficial trapping mechanism that improves battery reliability.
2Reliability
If ion trapping agent is added to trap transition metal ions, then cycle performance improves, but the complexity of battery composition increases
Solution Approach 1:
The ion trapping agent performs multiple functions simultaneously: it traps transition metal ions, reduces them to lower valence states, and protects both the electrolyte and interface films from degradation. This multi-functionality improves cycle performance without requiring multiple separate additives, thereby limiting the increase in composition complexity.
3Reliability
If ion trapping agent with reduction potential 0-2 V is used, then transition metal ions are reduced to low-valence states, but the selection of suitable materials becomes more restricted
Solution Approach 1:
The patent specifies a particular parameter range (reduction potential 0-2 V relative to Li/Li+) for the ion trapping agent to ensure effective reduction of transition metal ions to low-valence states. This parameter constraint guarantees structural stability improvement while providing a clear selection criterion for suitable materials.
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 ion trapping agent effectively reduces transition metal ions to low-valence states, enhancing the structural stability and cycle performance of the secondary battery by mitigating electrolyte decomposition and interface film degradation.
Implementation Method 1
the reduction potential of the ion trapping agent relative to lithium metal is 0-2 V... the ion trapping agent can reduce transition metal ions dissolved from the secondary battery into low-valence ions that are not easily dissolved
Implementation Method 2
the dissolved transition metal ions can migrate and deposit on the surface of the negative electrode material... the ion trapping agent can reduce transition metal ions dissolved from the secondary battery
Data Source
AI summary
Embodiments of the present application provide a secondary battery and an electric device. The secondary battery comprises a positive electrode sheet, a separator, and a negative electrode sheet; at least one of the positive electrode sheet, the separator, or the negative electrode sheet comprises an ion trapping agent; the reduction potential of the ion trapping agent relative to lithium metal is 0-2 V.