Pressure-Resistant Cathode Particles to Limit Crushing and Swelling
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Solution Overview
Problem
Lithium-ion batteries face issues with particle crushing during cycling due to high nickel content in positive active materials, leading to deteriorated cycle performance and volume swelling, which hinders their application in traction batteries.
Innovation Solution
A positive active material with secondary particles composed of primary particles, featuring a compact structure and high pressure-resistant strength, along with an outer and inner coating layer to enhance mechanical stability and ionic conductivity, is developed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nickel content of positive electrode material is increased to improve energy density, then energy density is improved, but cycle performance deteriorates due to aggravated side reactions with electrolyte
Solution Approach 1:
A coating layer comprising fluorinated compounds is applied to the surface of the positive electrode material. This coating layer acts as an intermediary barrier between the high-nickel positive electrode material and the electrolyte, preventing direct contact and side reactions while allowing lithium ion transport, thus maintaining high energy density while improving cycle performance
Solution Approach 2:
The surface chemistry of the positive electrode material is modified by introducing fluorinated compounds that form a stable protective layer. This changes the interfacial parameters between the electrode material and electrolyte, reducing side reactions and improving cycling stability without affecting the bulk energy density
2Use of energy by moving object
If nickel content of positive electrode material is increased to improve energy density, then energy density is improved, but particle crushing occurs during cycling leading to deteriorated cycle performance
Solution Approach 1:
The fluorinated coating layer serves as a protective intermediary that reinforces the particle structure during cycling. This coating prevents direct mechanical stress concentration on the high-nickel particles, reducing particle crushing while maintaining the high energy density benefits of increased nickel content
Solution Approach 2:
A composite structure is formed by combining high-nickel positive electrode material particles with a fluorinated compound coating layer. This composite structure leverages the high capacity of nickel-rich materials while the fluorinated coating provides mechanical protection against particle crushing during cycling
3Reliability
If coating modification techniques are applied to improve cycle performance, then cycle performance is improved to some extent, but manufacturing complexity increases
Solution Approach 1:
The coating process utilizes simple parameter changes such as solution concentration, temperature, and immersion time to form the fluorinated protective layer. These controllable parameters enable straightforward manufacturing process integration without requiring complex multi-step procedures
Solution Approach 2:
The fluorinated coating acts as a simple intermediary layer that can be applied through straightforward wet chemical methods. This approach avoids complex physical vapor deposition or atomic layer deposition techniques, reducing manufacturing complexity while effectively improving cycle performance
Data Source
AI summary
This application relates to the field of battery technologies, and in particular, to a pressure-resistant positive active material and an electrochemical energy storage apparatus. The positive active material includes secondary particles composed of primary particles, and a quantity σ of primary particles per unit sphere area in a SEM graph of the secondary particles is 5/μm2 to 30/μm2. A single-particle pressure-resistant strength of the secondary particles is 60 MPa to 300 MPa. A molecular formula of the positive active material is LixNiyCozMkMepOrAm, where 0.95≤x≤1.05, 0≤y≤1, ≤z≤1, 0≤k≤1, 0≤p≤0.1, 1≤r≤2, 0≤m≤2, and m+r≤2. The positive active material in this application has a compact particle structure and a high single-particle pressure-resistant strength.