Bimodal Cathode Material for High-Rate Lithium-Ion Batteries
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Solution Overview
Problem
Lithium secondary batteries face challenges with low safety, high cost, and instability at high temperatures due to limitations in cathode active materials like LiCoO2 and nickel-based lithium transition metal oxides, which result in reduced cycle characteristics and capacity.
Innovation Solution
A cathode active material with a bimodal form comprising lithium cobalt-based oxide and surface-treated lithium nickel-based oxide, where the average diameters of the oxides differ, is used to enhance rolling density and stability, incorporating dopants like Mg and Ti for improved electrical conductivity and a coating of Al2O3 for high-temperature storage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiCoO2 is used as cathode active material, then excellent cycle properties are achieved, but safety is low and cost is high
Solution Approach 1:
The patent uses a composite cathode material consisting of LiCoO2 combined with surface-treated lithium nickel-based oxide. This composite structure allows LiCoO2 to provide excellent cycle properties while the lithium nickel-based oxide component addresses safety concerns and reduces cobalt content, thereby lowering cost.
2Reliability
If LiCoO2 is used as cathode active material, then excellent cycle properties are achieved, but charge and discharge current capacity is low
Solution Approach 1:
The composite structure combines LiCoO2 with lithium nickel-based oxide, where the lithium nickel-based oxide component provides higher charge and discharge current capacity while LiCoO2 maintains excellent cycle properties, achieving a balance between the two parameters.
3Reliability
If lithium nickel-based oxide substituted with metal is used, then cycle and capacity characteristics are improved, but chemical stability is low and gas generation occurs
Solution Approach 1:
The patent applies surface treatment to the lithium nickel-based oxide using aluminum oxide coating. This surface layer acts as an intermediary that protects the bulk material from chemical reactions with the electrolyte, preventing gas generation while maintaining the high capacity and cycle characteristics of the nickel-based oxide.
4Reliability
If simple mixture of two lithium transition metal oxides is used, then drawbacks of separately using each oxide are overcome, but synergy effect is not achieved
Solution Approach 1:
The patent merges LiCoO2 and lithium nickel-based oxide into a composite structure where the two materials are closely integrated at the particle level. This merging enables synergistic effects where the combination performs better than the simple sum of individual components, achieving improved overall performance and productivity.
Data Source
AI summary
Disclosed are a cathode active material for secondary batteries and a lithium secondary battery including the same. More particularly, a cathode active material for secondary batteries having an operating voltage area of 2.50 V to 4.35 V, including a lithium cobalt-based oxide and a surface-treated lithium nickel-based oxide and having high rolling density by a bimodal form in which an average diameter of the cobalt-based oxide and an average diameter of the lithium nickel-based composite oxide are different, and a lithium secondary battery including the same are disclosed.