Single-Crystal Positive Electrode Material With Cation-Mixing Surface Layer
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Solution Overview
Problem
Lithium-nickel composite oxide (LiNiO2) based positive electrode active materials in lithium secondary batteries suffer from poor high-temperature stability and are prone to degradation due to internal short circuits and side reactions with the electrolyte, leading to battery swelling and potential explosions.
Innovation Solution
A positive electrode active material with a lithium-based composite oxide having a single crystal structure and a cation-mixing layer on its surface, reducing the surface area and grain boundary density to enhance thermal and structural stability, thereby minimizing side reactions and gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-nickel composite oxide (LiNiO2) is used as positive electrode active material, then reversible capacity is improved (approximately 200 mAh/g), but high-temperature stability deteriorates due to crystal structure instability caused by delithiation
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the interior maintains high-nickel content for capacity while the surface layer has modified composition (reduced nickel, added aluminum and lithium) for stability. This spatial differentiation of material properties resolves the contradiction between bulk capacity and surface stability.
Solution Approach 2:
The patent creates a composite material system combining lithium-nickel composite oxide core with aluminum-lithium-containing surface layer. This composite structure integrates the high capacity of nickel-based materials with the structural stability of aluminum-lithium compounds, simultaneously achieving both improved capacity and enhanced high-temperature stability.
2Quantity of substance
If lithium-nickel composite oxide (LiNiO2) is used to achieve high capacity, then battery capacity is improved, but reliability deteriorates due to degradation from internal short circuits and side reactions with electrolyte
Solution Approach 1:
The aluminum-lithium-containing surface layer acts as an intermediary barrier between the high-nickel active material and the electrolyte. This intermediate layer prevents direct harmful interactions while allowing ionic transport, thereby maintaining reliability without sacrificing capacity.
Solution Approach 2:
The patent applies preliminary anti-action by pre-forming a protective surface layer before battery operation that prevents degradation reactions. This preliminary protective measure counteracts potential harmful effects before they can occur during cycling and storage.
3Ease of manufacture
If conventional positive electrode active material is used, then manufacturing is simpler, but harmful factors increase due to gas generation causing battery swelling and explosion hazards
Solution Approach 1:
The patent converts the potentially harmful high reactivity of nickel-based materials into a benefit by using it to form a stable surface layer through controlled reaction. The same nickel content that could cause degradation is transformed into a protective interface that prevents gas-generating side reactions during normal operation.
Data Source
AI summary
The present invention relates to a positive electrode active material which has the structural stability of a lithium composite oxide constituting a positive electrode active material and a lithium secondary battery including the same. The lithium composite oxide constituting the positive electrode active material according to the present invention is able to reduce the surface area and grain boundary of secondary particles having a side reaction with an electrolyte solution, thereby improving high-temperature stability and reducing gas generation caused by the positive electrode active material, and the structural stability of the lithium composite oxide may be improved using a cation-mixing layer covering the surface of a primary particle.