Positive Electrode Coating for Low-Resistance Moisture-Stable Li-Ion Cells
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Solution Overview
Problem
Existing lithium ion secondary batteries face issues with high interface resistance due to the reaction between the positive electrode active material and the solid electrolyte, leading to decreased lithium ion conductivity and susceptibility to atmospheric moisture adsorption, which affects battery performance.
Innovation Solution
A positive electrode active material comprising powdery particles of a composite oxide represented by Formula (LiaNibXcBadYeOx) with an organosilicon compound adhered to its surface, where the organosilicon compound includes organic functional groups, such as alkyl or aryl groups, to suppress the formation of high resistance layers and moisture adsorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating layer including lithium niobate or Li4Ti5O12 is formed on the surface of a positive electrode active material, then interface resistance between the positive electrode active material and solid electrolyte decreases, but adsorption of atmospheric moisture into the positive electrode active material cannot be suppressed
Solution Approach 1:
The patent applies a composite coating structure consisting of two distinct layers: an inner layer of lithium niobate or Li4Ti5O12 that provides low interface resistance with the solid electrolyte, and an outer layer of organic functional groups (such as alkyl or aryl groups) that provides moisture barrier properties. This composite material approach allows each layer to perform its specialized function, resolving the contradiction between achieving low interface resistance and preventing moisture adsorption.
Solution Approach 2:
The patent implements local quality by differentiating the functional properties of different regions of the coating. The inner layer is optimized for electrical conductivity and interface resistance with the solid electrolyte, while the outer layer is optimized for hydrophobicity and moisture barrier properties. This spatial differentiation of material properties allows simultaneous optimization of both interface resistance and moisture protection.
2Quantity of substance
If a positive electrode active material abundant in nickel is used to increase battery capacity, then battery capacity increases, but the battery properties are easily impaired due to adsorption of atmospheric moisture
Solution Approach 1:
The patent uses a composite coating material system where the inorganic layer (lithium niobate or Li4Ti5O12) provides structural stability and low interface resistance, while the organic layer with hydrophobic functional groups provides moisture barrier protection. This composite structure allows high-nickel positive electrode materials to maintain both high capacity and stability by protecting them from atmospheric moisture while maintaining good interface properties with the solid electrolyte.
Solution Approach 2:
The dual-layer coating acts as an intermediary between the high-nickel positive electrode active material and the external environment. The inner inorganic layer mediates the interface between the active material and solid electrolyte, while the outer organic layer mediates the protection against atmospheric moisture. This intermediary structure allows the high-nickel material to function at high capacity without direct exposure to harmful environmental factors.
3Object-affected harmful factors
If an organosilicon compound with organic functional groups is adhered to the surface of powdery particles, then adsorption of atmospheric moisture is suppressed, but lithium ion conductivity may be affected
Solution Approach 1:
The patent segments the coating into two functional layers: the inner inorganic layer (lithium niobate or Li4Ti5O12) that ensures lithium ion conductivity and low interface resistance, and the outer organic layer (organosilicon compound with alkyl or aryl groups) that provides moisture barrier properties. This segmentation allows each layer to perform its specialized function without interfering with the other, resolving the contradiction between moisture protection and lithium ion conductivity.
Solution Approach 2:
The patent applies local quality by assigning different functional properties to different layers of the coating. The inner layer is optimized for lithium ion transport and electrical conductivity, while the outer layer is optimized for hydrophobicity and moisture barrier properties. This localized functional differentiation allows the organic functional groups to suppress moisture adsorption without significantly affecting lithium ion conductivity, as the inorganic inner layer maintains the conductive pathway.
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 solution enhances lithium ion conductivity and prevents moisture adsorption, improving the stability and performance of lithium ion secondary batteries, particularly in all-solid configurations.
Implementation Method 1
an organosilicon compound adhered to surfaces of the powdery particles
Data Source
AI summary
A positive electrode active material for a lithium-ion secondary cell having exceptional lithium ion conductivity, the positive electrode active material being such that the absorption of moisture from the atmosphere can be suppressed. This positive electrode active material for a lithium-ion secondary cell has powder particles that include a specific composite oxide, and an organic silicon compound affixed to the surface of the powder particles, the organic functional groups of the organic silicon compound including at least one selected from the group made of C2-10 alkyl groups and C6-14 aryl groups.