Non-uniform Cathode Coating for High-Rate Discharge
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Solution Overview
Problem
Conventional battery cathode materials suffer from reduced performance due to uniform coatings and low moisture content, leading to limited high-rate discharge capacity and stability, especially under high temperature storage.
Innovation Solution
A non-uniform coating of cathode active materials, such as nickel oxyhydroxide, with a cobalt oxyhydroxide coating and controlled moisture content, is applied, along with a slow addition of alkali hydroxide during synthesis, to enhance performance and connectivity between particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform coating is applied to cathode active material, then the coating provides consistent protection and conductivity, but the high-rate discharge capacity and performance are reduced
Solution Approach 1:
The patent applies a non-uniform coating where different regions of the cathode active material particles have different coating characteristics. Specifically, the coating density varies from the particle center to the surface, with the core region having lower coating density and the outer region having higher coating density. This local variation in coating quality optimizes both protection and conductivity for different functional requirements within the same particle.
2Stability of the object's composition
If moisture content is kept low in cathode active material, then storage stability is improved, but high-rate discharge capacity is reduced
Solution Approach 1:
The patent changes the moisture content parameter from conventional low levels to a higher range of 3-7% by weight. This parameter change enables the cathode active material to achieve both improved high-rate discharge capacity and acceptable storage stability. The elevated moisture content enhances ionic conductivity and facilitates faster discharge rates while the specific coating structure mitigates excessive self-discharge during storage.
3Productivity
If alkali hydroxide is added quickly during synthesis, then production efficiency is improved, but cathode active material performance is reduced
Solution Approach 1:
The patent employs periodic addition of alkali hydroxide during the synthesis process rather than adding it all at once. The alkali hydroxide is added in controlled increments over time, allowing for proper coating formation at each stage. This periodic addition method ensures optimal coating structure and particle morphology while maintaining reasonable production efficiency, avoiding the performance degradation associated with rapid single-stage addition.
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 approach results in improved battery performance, with a 50% to 110% increase in digital camera test results and retained high-rate capacity even after extended high-temperature storage, through increased connectivity and synergistic effects of non-uniform coating and elevated water content.
Implementation Method 1
a coated nickel oxyhydroxide having a coated surface area of at most 50 percent and a resistivity of at least four ohm centimeters
Implementation Method 2
The non-uniformly coated cathode active material can have relatively high moisture (e.g., water) content... one or more of these cathode active material characteristics can improve performance
Data Source
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AI summary
Cathodes that include an active cathode material are described. The active cathode material can be coated.