Core-Shell NCM Electrode with Boron Lithium Oxide Coating
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high capacity, output characteristics, and cycle stability due to limitations in thermal and chemical stability, particularly with nickel manganese-based lithium composite metal oxides, which experience rapid degradation and gas swelling issues.
Innovation Solution
A positive electrode active material comprising a lithium transition metal oxide with specific structural and compositional features, including a differential graph with three peaks from pH titration analysis, and a coating of boron lithium oxide, ensures excellent chemical and thermal stability, high capacity, and improved charge and discharge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nickel content is increased in NCM-based lithium oxide to achieve high energy density, then energy density is improved, but cycle characteristics are rapidly degraded and chemical stability deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core region contains high nickel content (0.6-0.8) for high energy density, while the outer shell region contains lower nickel content (0.3-0.6) for improved stability. This spatial differentiation of composition allows simultaneous optimization of energy density and cycle characteristics.
Solution Approach 2:
The patent uses composite materials by combining nickel manganese cobalt oxide with a protective coating layer containing aluminum oxide and/or lithium aluminum oxide. This composite structure provides both high capacity from the NCM core and enhanced chemical/thermal stability from the AL coating, resolving the contradiction between energy density and reliability.
2Temperature
If nickel is substituted with manganese in lithium composite metal oxide to improve thermal stability, then thermal stability is improved, but output characteristics are reduced
Solution Approach 1:
The patent applies local quality by concentrating manganese in the outer shell region (0.4-0.6 mole ratio) where it provides thermal stability, while maintaining higher nickel content in the inner core region (0.6-0.8) where it delivers high output characteristics. This spatial separation allows both thermal stability and power performance to be optimized simultaneously.
3Quantity of substance
If nickel is substituted with cobalt in lithium composite metal oxide to maintain reversible capacity, then reversible capacity is maintained, but thermal stability is reduced
Solution Approach 1:
The patent applies local quality by placing cobalt-rich regions in the inner core where high reversible capacity is needed, while positioning manganese-rich regions in the outer shell where thermal stability is required. The gradient composition (0.3-0.6 for Co, 0.4-0.6 for Mn) creates local optimization of both capacity and thermal properties.
4Reliability
If a coating of boron lithium oxide is applied to the positive electrode active material, then chemical and thermal stability are enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating boron-containing compounds into the NCM precursor mixture before sintering, allowing the boron lithium oxide coating to form in-situ during the sintering process itself. This eliminates the need for separate coating steps, reducing manufacturing complexity while achieving the desired stability enhancement.
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 proposed active material achieves high capacity, output, and extended cycle life with enhanced chemical and thermal stability, addressing the limitations of existing nickel manganese-based lithium composite metal oxides.
Implementation Method 1
electrical energy is produced by oxidation and reduction reactions when the lithium ions are intercalated/deintercalated into/from the positive electrode and the negative electrode
Data Source
AI summary
The present invention provides a positive electrode active material for a secondary battery which includes a lithium transition metal oxide, wherein the positive electrode active material has three peaks in a differential graph (ERC curve) obtained by differentiating a pH value against an amount of acid (HCl) added, which is obtained by pH titration of 10 g of the lithium transition metal oxide using 0.5 M HCl, wherein a y-axis (dpH/dml) value of a first peak at the smallest x-axis value among the three peaks is −1.0 or less.