Boron-Modified Ni-Mn Oxide for High-Temperature Resistance
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Solution Overview
Problem
High-temperature storage of non-aqueous electrolyte secondary batteries with lithium transition metal oxides having high Ni content increases the direct current resistance (DCR) due to nickel elution and side reactions with the electrolyte.
Innovation Solution
A positive electrode active material comprising secondary particles of lithium transition metal oxide with Ni and Mn, where the boron compound is present both internally and on the surface, with a composition ratio difference between Ni and Mn greater than 0.2 and boron content in the range of 5-60% by mass, stabilizing the crystal structure and forming a dense film to suppress nickel elution and side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high Ni content lithium transition metal oxide is used to achieve high voltage, then voltage is improved, but direct current resistance increases due to nickel elution during high-temperature storage
Solution Approach 1:
A boron compound is introduced as an intermediary substance between the high Ni content lithium transition metal oxide and the electrolyte. The boron compound forms a protective interface layer that mediates the interaction, preventing direct contact between the nickel-containing oxide and electrolyte, thereby suppressing nickel elution and side reactions while maintaining the high voltage characteristics of the nickel-rich material.
Solution Approach 2:
The boron compound acts as a sacrificial protective layer that can be consumed or transformed during initial cycles to form a stable protective interface. This disposable-like approach allows the boron compound to undergo initial reactions to create a stable surface layer that then protects the underlying high Ni content material during long-term storage.
2Quantity of substance
If high Ni content lithium transition metal oxide is used, then battery capacity is improved, but nickel elution occurs during high-temperature storage increasing resistance
Solution Approach 1:
The boron compound serves as a protective intermediary that forms a barrier between the nickel-containing lithium transition metal oxide and the electrolyte environment. This intermediate layer specifically targets and prevents nickel elution into the electrolyte, maintaining the nickel content and electrochemical capacity of the positive electrode material during high-temperature storage.
Solution Approach 2:
The invention changes the chemical composition parameters of the positive electrode by incorporating boron compounds with specific characteristics (water solubility of 0.1 g/100 mL or less). This parameter change in composition creates a surface layer with different chemical stability properties that resist nickel elution while allowing the bulk material to maintain its high capacity characteristics.
3Reliability
If lithium transition metal oxide with high Ni content is used, then electrochemical performance is improved, but side reactions with electrolyte increase during high-temperature storage
Solution Approach 1:
The boron compound forms an intermediate protective interface layer between the lithium transition metal oxide and the electrolyte solution. This intermediary layer acts as a physical and chemical barrier that prevents direct contact between the electrochemically active material and the electrolyte, thereby suppressing side reactions such as solvent decomposition and salt decomposition that would otherwise occur during high-temperature storage.
Solution Approach 2:
The boron compound forms a thin film coating on the surface of the lithium transition metal oxide particles. This thin film structure provides effective protection against side reactions while maintaining sufficient ionic conductivity for lithium ion transport, balancing the need for electrochemical performance with the need to suppress harmful side reactions during storage.
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 configuration effectively reduces the increase in battery direct current resistance during high-temperature storage by preventing nickel elution and side reactions, maintaining battery performance.
Implementation Method 1
stabilizing the crystal structure and forming a dense film to suppress nickel elution and side reactions
Implementation Method 2
forming a dense film to suppress nickel elution and side reactions
Data Source
AI summary
The present disclosure is directed to a positive electrode active material for non-aqueous electrolyte secondary batteries that is capable of suppressing an increase in battery direct current resistance due to high-temperature storage (e.g., storage at 60° C. or higher). Positive electrode active material particles in one aspect of the present disclosure include secondary particles formed by aggregation of primary particles of a lithium transition metal oxide containing Ni and Mn and include a boron compound present in the inner part and surface of the secondary particles. The difference in composition ratio between Ni and Mn in the lithium transition metal oxide is more than 0.2. The proportion of the boron element content in the inner part of the secondary particles to the total boron element content in the inner part and surface of the secondary particles is in the range from 5% by mass to 60% by mass.