Lithium Boron Composite Coating for Cathode Stability
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Solution Overview
Problem
Lithium composite oxides used in lithium secondary batteries suffer from reduced operational stability and capacity retention due to side reactions with air and electrolytes, leading to the formation of lithium impurities that degrade battery performance.
Innovation Solution
A cathode active material is developed with a core portion of lithium metal oxide particles coated with a lithium boron composite oxide layer, which reduces the specific surface area and suppresses side reactions, enhancing structural and life-span stability. The coating layer covers at least 70% of the core portion's surface and includes lithium boron composite oxides like LiBO2, Li2BO2, and Li2B4O7, with aluminum added for further stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium composite oxide is used as cathode active material to achieve high capacity and high power, then energy density and operational voltage are improved, but side reactions with air and electrolyte occur leading to lithium impurity formation and deterioration of operational stability
Solution Approach 1:
A coating layer comprising aluminum and boron is applied as an intermediary between the lithium composite oxide cathode active material and the electrolyte/air. This coating layer acts as a protective barrier that prevents direct contact and side reactions, while still allowing lithium ion transport. The coating includes aluminum oxide, aluminum hydroxide, boron oxide, and/or boric acid, forming a stable interface that maintains high nickel content benefits without suffering from surface degradation.
Solution Approach 2:
The cathode active material is designed as a composite structure with a core-shell configuration. The core consists of high-nickel lithium composite oxide (LiNi0.8Co0.1Mn0.1O2 or similar compositions) providing high capacity and power, while the shell comprises aluminum and boron compounds that provide chemical stability and protect against electrolyte degradation. This composite structure combines the advantages of high-energy-density materials with the stability of protective coatings.
2Quantity of substance
If high-nickel lithium composite oxide is used to increase capacity, then energy density is improved, but large amounts of lithium impurities (LiOH, Li2CO3) are formed on the surface due to side reactions
Solution Approach 1:
The aluminum-boron coating layer serves as an intermediary barrier that prevents the formation of lithium impurities by blocking the direct reaction between lithium composite oxide and air/electrolyte. The coating materials (aluminum oxide, aluminum hydroxide, boron oxide, boric acid) are chemically stable and do not participate in harmful side reactions, thereby preventing LiOH and Li2CO3 formation while maintaining high capacity.
Solution Approach 2:
The coating process converts the harmful surface reactivity of high-nickel lithium composite oxide into a beneficial protective feature. By deliberately applying aluminum and boron compounds to the surface, the naturally reactive and impurity-prone surface is transformed into a stable, protected interface that prevents impurity formation while preserving the high capacity benefits of the bulk material.
3Object-generated harmful factors
If the lithium impurity is washed with water to remove surface contaminants, then surface cleanliness is improved, but the specific surface area increases and side reaction with electrolyte is accelerated
Solution Approach 1:
Instead of washing with water after synthesis (which increases surface area and instability), the aluminum-boron coating is applied as a preliminary protective action before the material contacts the electrolyte. This pre-coating approach stabilizes the surface area and prevents the acceleration of side reactions that would otherwise occur upon water washing and electrolyte exposure.
Solution Approach 2:
The aluminum-boron coating acts as an intermediary layer that eliminates the need for water washing. By providing a stable, protective barrier during synthesis and handling, the coating allows the material to be used directly without water treatment, thereby avoiding the increase in specific surface area and subsequent acceleration of electrolyte side reactions.
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 lithium boron composite oxide coating significantly improves the operational stability and capacity retention of lithium secondary batteries by reducing side reactions and maintaining structural integrity, even under high-temperature conditions, thereby extending the battery's life-span and maintaining electrochemical performance.
Implementation Method 1
a coating layer at least partially covering a surface of the core portion and including a lithium boron composite oxide
Implementation Method 2
maintaining structural integrity, even under high-temperature conditions
Data Source
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Figure 3~4
AI summary
A cathode active material for a lithium secondary battery includes a core portion comprising a lithium metal oxide particle, and a coating layer at least partially covering a surface of the core portion and including a lithium boron composite oxide. The lithium boron composite oxide is included in an amount from 100 ppm to 1,500 ppm based on a total weight of the cathode active material. A lithium secondary battery having improved structural stability and electrical property is provided using the cathode active material.