Core-Shell Electrode Material Moisture Barrier
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face issues with gas generation due to moisture reaction, despite carbon coating on electrode active materials, as uniform carbon coating is difficult to achieve, leaving some areas exposed and prone to moisture contact.
Innovation Solution
The development of an electrode active material with a core-shell structure, where a carbon-composite inorganic composite oxide core is coated with a carbon shell, enhancing electrical conductivity and preventing moisture adsorption, with a specific surface area of 6.0 m2/g or more and moisture content of 400 ppm or less, achieved through a carbon coating precursor with electron-donating properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the specific surface area of the electrode active material is increased to improve battery capacity, then the battery capacity increases, but the reaction with moisture becomes more prominent leading to increased gas generation
Solution Approach 1:
A carbon coating layer is formed on the surface of the electrode active material particles to create a protective shell. This thin film shell prevents moisture from reaching the high-surface-area active material, thereby suppressing gas-generating side reactions while preserving the high capacity benefits of increased specific surface area.
Solution Approach 2:
The electrode active material is created as a composite structure combining the inorganic oxide core with a carbon coating layer. This composite material integrates the high capacity of the oxide with the moisture barrier properties of carbon, resolving the contradiction between high capacity and gas generation.
2Object-generated harmful factors
If carbon coating is applied to the surface of the electrode active material to prevent moisture reaction, then gas generation is reduced, but the coating is difficult to form uniformly leaving exposed areas
Solution Approach 1:
An organic polymer substance serves as an intermediary precursor that uniformly adsorbs onto the electrode active material surface before carbonization. This intermediary layer ensures even distribution of the carbon source, enabling uniform carbon coating formation that completely covers the particle surface without exposed areas.
Solution Approach 2:
The coating process utilizes parameter changes through thermal decomposition. The organic polymer precursor is heated to decompose and transform into a uniform carbon coating layer, with the transformation parameters (temperature, time) controlled to achieve complete and even coverage.
3Quantity of substance
If lithium metal oxide with highly Lewis basic oxygen atoms is used to achieve high capacity, then the battery capacity increases, but the reaction with moisture increases forming hydroxyl groups that are difficult to remove
Solution Approach 1:
A carbon coating shell is formed on the lithium metal oxide particles to create a moisture barrier. This protective shell prevents moisture from contacting the Lewis basic oxygen atoms on the oxide surface, thereby preventing hydroxyl group formation while preserving the high capacity of the lithium metal oxide.
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
This configuration effectively suppresses gas generation and battery performance degradation by reducing moisture content and ensuring uniform carbon coating, enhancing the safety and performance of nonaqueous electrolyte secondary batteries.
Implementation Method 1
an electron-conducting substance made of an organic polymer (precursor) is mixed with particles of an electrode active material, and then the mixture is subjected to a thermal decomposition reaction to form an electron-conducting coating film
Implementation Method 2
the adsorption of moisture cannot be reduced
Data Source
AI summary
An electrode active material for a nonaqueous electrolyte secondary battery includes: a core part including at least one of an inorganic oxide and a carbon-composite inorganic composite oxide; and a shell part for carbon coating on the core part. The electrode active material has a specific surface area of 6.0 m2/g or more. The electrode active material has a moisture content of 400 ppm or less, which is measured by a Karl Fischer method such that the electrode active material is heated in a heat-evaporating manner, and continuously maintained at 250° C. for 40 minutes without exposing to an atmosphere after the electrode active material is exposed to the atmosphere to absorb moisture to be saturated.