Positive Electrode Protection Layer for Safer High-Temperature Cycling
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Solution Overview
Problem
Existing lithium-ion batteries fail to achieve desirable safety performance while improving cycle life, as current solutions to alleviate capacity and power loss do not sufficiently enhance safety.
Innovation Solution
A positive electrode plate with a protection layer comprising inorganic particles, a conductive oxide with a doping element, and a water-soluble polymer metal salt binder, which enhances adhesion, conductivity, and safety by forming a high-resistance coating, reducing short-circuit points, and improving interfacial adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a positive electrode protective agent and additives are used to improve SEI and CEI film formation, then capacity loss is alleviated, but safety performance does not achieve desirable improvement
Solution Approach 1:
The patent uses a composite protective layer containing inorganic particles (alumina, silica, or boehmite) combined with conductive carbon materials (acetylene black, Ketjen black, or carbon nanotubes) and binder polymers. This composite structure provides both mechanical protection for cycle life extension and thermal stability for safety improvement, resolving the contradiction between reliability and safety performance.
Solution Approach 2:
The protective layer is applied specifically at the positive electrode surface where safety issues occur during charging. The inorganic particles are distributed throughout the protective layer to provide localized thermal stability at critical heat generation points, while the conductive carbon materials are positioned to maintain electron transport pathways. This localized quality enhancement addresses safety performance without compromising overall cycle life.
2Object-affected harmful factors
If the amount of carbon nanotubes is reduced to improve high-temperature stability, then safety is improved, but conductivity of the positive electrode deteriorates
Solution Approach 1:
The patent changes the material composition parameters by introducing inorganic particles with high thermal stability (alumina, silica, boehmite) to replace carbon nanotubes for thermal stability. Simultaneously, it adjusts the conductive carbon material content and type (acetylene black, Ketjen black, or carbon nanotubes) to maintain optimal conductivity parameters. This parameter optimization resolves the contradiction between high-temperature stability and conductivity.
Solution Approach 2:
The protective layer combines inorganic particles for thermal stability with conductive carbon materials for electron transport. The inorganic particles form a thermally stable matrix while the conductive carbon materials embedded within maintain electrical conductivity pathways. This composite material approach simultaneously achieves high-temperature stability and adequate conductivity without relying solely on carbon nanotubes.
3Object-affected harmful factors
If an oil-based separator is used to suppress battery deformation at high temperature, then safety is improved, but cycle life improvement is compromised
Solution Approach 1:
The patent applies a protective layer to the positive electrode surface before battery assembly, pre-establishing a barrier that prevents electrode deformation during subsequent high-temperature cycling. This preliminary protective action eliminates the need for oil-based separators during operation, as the deformation suppression function is already provided by the solid protective layer, thereby improving cycle life while maintaining safety.
Solution Approach 2:
The patent extracts the deformation suppression function from the oil-based separator and transfers it to the solid protective layer on the positive electrode. By taking out this specific function from the separator system, the battery can use standard separators that maintain good cycle life performance, while the protective layer independently provides high-temperature deformation suppression.
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 positive electrode plate improves safety and electrical performance by reducing short-circuit risks, enhancing conductivity, and boosting electron and ion transmission, resulting in better high-temperature cycle performance.
Implementation Method 1
The water-soluble polymer metal salt possesses a large specific surface area, and can be highly dispersed after contacting water. In addition, the physical tensile strength of the water-soluble polymer metal salt is high, and a large number of polar functional groups exist on the surface of the water-soluble polymer metal salt, thereby increasing the interaction force between the positive electrode protection layer and the positive electrode current collector, and increasing the interfacial adhesion.
Implementation Method 2
The inorganic particles added in the positive electrode protection layer can form a safety protection coating of high adhesiveness and a high resistance, thereby reducing dangerous short-circuit points on the positive electrode, increasing the short-circuit resistance, reducing the heat power generated by a short circuit, and improving safety performance.
Implementation Method 3
By doping a specified conductive oxide with a specified type of doping element at a specified mass percentage, the positive electrode protection layer is made highly conductive.
Implementation Method 4
In addition, the water- soluble polymer metal salt is relatively hydrophilic, and is more soluble than non-water- soluble polymers, thereby boosting the transmission of electrons and ions, thereby enhancing the kinetics of the battery, and improving the electrical performance of the battery, especially high-temperature cycle performance.
Data Source
AI summary
A positive electrode plate includes a current collector, and a positive electrode protection layer and a positive active material layer disposed on the current collector in sequence. The positive electrode protection layer includes inorganic particles, a first conductive material, and a binder. The binder includes a water-soluble polymer metal salt. The first conductive material includes a conductive oxide containing a doping element. A first metal element in the conductive oxide includes at least one of a Group IVA metal element and a Group IIIA metal element. The doping element includes at least one of a Group IIIA non-metal element, a Group VA element, or a Group VIIA 10 element. A mass ratio of the doping element to the first metal element is 1: (10 to 200), and a mass ratio of the first metal element to a metal element in the inorganic particles is 1: (3 to 9).