ALD-Coated Sintered Cathodes for Stable Cathode-Electrolyte Interfaces
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Solution Overview
Problem
Cathode-electrolyte interface instability in lithium-ion batteries using lithium cobalt oxide (LCO) or nickel-manganese-cobalt (NMC) materials leads to corrosion and capacity degradation over time due to unwanted reactions between electroactive transition metals and electrolytes.
Innovation Solution
A thin coating layer, typically 0.2 to 20 nanometers thick, formed by atomic layer deposition (ALD) on sintered cathodes using materials like aluminum oxide, aluminum fluoride, or zinc oxide, is applied to the external and internal surfaces to separate the cathode from electrolytes, preventing unwanted reactions and enhancing mechanical support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating layer is applied to the cathode surface to prevent corrosion and improve stability, then the cathode-electrolyte interface stability is improved, but the impedance increases due to the additional layer
Solution Approach 1:
The patent applies a thin film coating layer (typically less than 100 nanometers, preferably less than 50 nanometers, and in some cases less than 10 nanometers) on the cathode surface. This thin film acts as a protective shell that prevents corrosion while minimizing impedance increase due to its minimal thickness. The coating provides physical separation between the cathode and electrolyte, reducing unwanted reactions while maintaining ionic conductivity.
Solution Approach 2:
The patent optimizes the thickness parameter of the coating layer to balance protection and conductivity. By controlling the coating thickness to be very thin (nanometer scale), the system achieves sufficient protection against corrosion while minimizing the impedance increase that would result from a thicker barrier layer.
2Reliability
If a thick coating layer is used to provide better protection against corrosion, then the cathode surface protection is improved, but the energy density decreases due to the additional material and volume
Solution Approach 1:
The patent employs ultra-thin film coatings (nanometer scale) that provide adequate corrosion protection without adding significant volume or mass. This thin film approach ensures that the protective function is achieved while minimizing the impact on the active material volume, thereby preserving high energy density.
Solution Approach 2:
The coating is applied only on the surface of the cathode particles, providing protection exactly where it is needed (at the cathode-electrolyte interface) without adding material throughout the entire cathode structure. This localized application ensures that the bulk of the cathode material remains available for electroactive processes, maintaining high energy density.
3Ease of manufacture
If conventional particulate cathodes are used, then the manufacturing process is simpler, but the energy density is lower due to the need for organic binders and carbon conductors
Solution Approach 1:
The patent removes organic binders and carbon conductors from the cathode structure by using sintered cathode materials. This extraction of unnecessary components eliminates the volume occupied by inactive materials, thereby increasing the proportion of active material and improving energy density while maintaining structural integrity through sintering.
Solution Approach 2:
The patent creates a composite structure by combining the sintered cathode material with a thin inorganic coating layer. This composite approach provides both the structural integrity normally requiring binders and the electroactive performance needed for high energy density, eliminating the need for organic binders and carbon conductors.
4Object-affected harmful factors
If the cathode surface is left uncoated, then the impedance remains low, but the electrical capacity degrades rapidly due to corrosion during cycling
Solution Approach 1:
The patent applies a thin protective film that acts as a barrier between the cathode and electrolyte, preventing corrosion reactions that would otherwise degrade the cathode surface and reduce shelf life. The thin nature of the film ensures that it does not significantly increase impedance while providing effective protection.
Solution Approach 2:
The coating layer is applied in advance to the cathode surface to prevent corrosion before it can occur during battery cycling and storage. This preliminary protective action creates a stable interface that resists degradation over time, extending the battery's shelf life without significantly impacting electrical performance.
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 coated sintered cathodes exhibit improved electrical capacity retention and reduced impedance after multiple charge-discharge cycles, extending the shelf life and maintaining performance by stabilizing the cathode-electrolyte interface and protecting against corrosion.
Implementation Method 1
a coating layer that is formed by atomic layer deposition
Data Source
AI summary
A battery is provided comprising a coated sintered cathode. The coated sintered cathode comprises at least one of lithium cobalt oxide (LiCoO2) or NMC (LiNi(1-x-y)MnxCoyO2). The coated sintered cathode also comprises a coating layer. The coating layer comprises at least one of aluminum oxide (Al2O3), aluminum fluoride (AlF3), zinc oxide (ZnO), magnesium oxide (MgO), titanium dioxide (TiO2), lanthanum oxide (La2O3), zirconium oxide (ZrO2), gallium oxide (Ga2O3), magnesium fluoride (MgF2), molybdenum trioxide (MoO3), selenium (Se), or phosphorous pentoxide (P2O5). The coating layer is coated on the sintered cathode by atomic layer deposition. The sintered cathode may form a cathode-electrolyte interface inside the battery, and the coating layer may be positioned at the cathode-electrolyte interface.