Cathode Surface Segregation for Stable Lithium-Ion Cycle Capacity
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Solution Overview
Problem
Secondary batteries, particularly lithium-ion secondary batteries, face challenges in discharge capacity, cycle performance, reliability, safety, and cost, with existing materials showing degradation and instability during charge and discharge cycles.
Innovation Solution
A method for manufacturing a positive electrode active material involving the formation of a composite oxide by mixing lithium, cobalt, and oxygen, followed by the segregation of magnesium, nickel, and fluorine on the surface through heating, which stabilizes the crystal structure and enhances discharge capacity and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional positive electrode active materials are used to achieve high discharge capacity, then the discharge capacity is improved, but the cycle performance and structural stability deteriorate due to crystal structure breakdown during charge and discharge cycles
Solution Approach 1:
The patent uses a composite oxide material with a specific layered crystal structure containing lithium, cobalt, and oxygen in defined ratios. This composite structure combines the high capacity benefits of lithium cobalt oxide with improved structural stability, resolving the contradiction between achieving high discharge capacity and maintaining cycle performance through material composition optimization
Solution Approach 2:
The patent introduces magnesium, nickel, and fluorine segregation at the surface regions of the composite oxide particles through controlled heating. This creates a core-shell like structure where the interior maintains high capacity characteristics while the surface layer provides enhanced structural stability and protection against degradation during cycling
2Stability of the object's composition
If the positive electrode active material is heated to segregate magnesium, nickel, and fluorine on the surface, then the crystal structure stability is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent combines the segregation of multiple elements (magnesium, nickel, and fluorine) into a single heating step rather than treating them separately. This merging of element segregation processes simplifies the manufacturing complexity while achieving the desired surface composition and crystal structure stability
Solution Approach 2:
The patent employs controlled heating at specific temperature ranges to induce phase separation and element segregation. By optimizing the heating temperature and duration parameters, the process achieves effective magnesium, nickel, and fluorine segregation on the particle surfaces without requiring excessively complex multi-step processing
3Ease of manufacture
If conventional materials are used without surface modification, then the manufacturing cost is reduced, but the safety and reliability deteriorate due to thermal runaway susceptibility
Solution Approach 1:
The patent introduces fluorine as an intermediary element that segregates to the surface of the composite oxide particles. This fluorine-rich surface layer acts as a protective barrier that inhibits thermal runaway reactions while maintaining manufacturing feasibility through a single heating step, thus improving safety without prohibitively increasing manufacturing cost
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 method provides a positive electrode active material with improved discharge capacity, stability against structural breakdown, and enhanced safety by inhibiting capacity loss and thermal runaway, resulting in a highly reliable secondary battery.
Implementation Method 1
magnesium, nickel, and fluorine are segregated on a surface of the composite oxide by the second step
Data Source
AI summary
A positive electrode active material inhibiting a decrease in discharge capacity due to charge and discharge cycles and a secondary battery including the positive electrode active material are provided. Alternatively, a secondary battery with a high level of safety is provided. The secondary battery includes a positive electrode containing a positive electrode active material, a negative electrode, and an electrolyte. The positive electrode active material is formed by a first step of mixing a composite oxide containing lithium, cobalt, and oxygen, a magnesium source, and a nickel source to form a mixture and a second step of heating the mixture. The nickel source is nickel fluoride. Magnesium, nickel, and fluorine are segregated on the surface of the composite oxide.