Lithium Nickelate Cathode Coating for High-Voltage Cycle Stability
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Solution Overview
Problem
Current positive electrode active substance particles for lithium nickelate composite oxide-based non-aqueous electrolyte secondary batteries face challenges in maintaining high capacity and repeated charge/discharge cycle characteristics due to ion elution and incomplete reaction during synthesis, leading to poor stability and side reactions with the electrolyte.
Innovation Solution
The development of positive electrode active substance particles with a lithium nickelate composite oxide core coated with a thin film of epitaxially grown inorganic compounds, specifically Al, Mg, Zr, Ti, or Si, having a high degree of crystallinity and coverage, which forms a protective layer to prevent electrolyte interaction while allowing Li+ ion insertion and desorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickelate composite oxide particles are used as positive electrode active substance, then high capacity and high energy density are achieved, but repeated charge/discharge cycle characteristics deteriorate due to ion elution and side reactions with electrolyte
Solution Approach 1:
An inorganic compound coating layer is introduced as an intermediary between the lithium nickelate composite oxide core particles and the electrolyte. This coating layer selectively prevents harmful ion elution and side reactions while allowing Li+ ions to pass through, thus resolving the contradiction between high capacity and good cycle characteristics.
Solution Approach 2:
A thin film coating of inorganic compound (such as Al2O3, TiO2, SiO2, ZrO2, or Nb2O5) is applied on the surface of the core particles. This thin film acts as a protective shell that maintains ion conductivity for Li+ while providing mechanical and chemical stability to prevent electrode material degradation during repeated charge/discharge cycles.
2Reliability
If surface treatment with lithium carbonate or lithium hydroxide is applied to improve cycle characteristics, then protective effect against hydrofluoric acid is enhanced, but incomplete reaction and residual impurities remain
Solution Approach 1:
The invention changes the coating material from organic compounds (lithium carbonate, lithium hydroxide) to inorganic compounds with higher thermal and chemical stability. This parameter change enables complete reaction and eliminates residual impurities while maintaining the protective function against hydrofluoric acid and enhancing cycle characteristics.
Solution Approach 2:
The invention uses composite structure consisting of lithium nickelate composite oxide core and inorganic compound coating shell. This composite material approach combines the high capacity of lithium nickelate with the stability and protective properties of inorganic compounds, achieving both high performance and complete reaction without residual impurities.
3Stability of the object's composition
If vapor phase epitaxial growth is used to form thin inorganic compound coating, then crystal structure destruction is suppressed, but coating uniformity and coverage may be insufficient
Solution Approach 1:
The inorganic compound coating serves multiple functions simultaneously: it suppresses crystal structure destruction, provides protective barrier against electrolyte, enables complete reaction without impurities, and can be applied with good uniformity and coverage. This multi-functionality resolves the contradiction between structural stability and coating quality.
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 solution enhances the charge/discharge cycle characteristics and maintains high capacity, reducing side reactions and improving the battery's service life by forming a protective nano-size thin film that inhibits electrolyte contact with the core particles.
Implementation Method 1
a coating compound Y comprising at least one element selected from the group consisting of Al, Mg, Zr, Ti and Si, in which the coating compound Y has an average film thickness of 0.2 to 5 nm, a degree of crystallinity of 50 to 95%, a degree of epitaxy of 50 to 95%
Data Source
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AI summary
The present invention provides positive electrode active substance particles comprising a lithium nickelate composite oxide which have a high energy density and which are excellent in repeated charge/discharge cycle characteristics upon charging at a high voltage when used in a secondary battery, as well as a non-aqueous electrolyte secondary battery. The present invention relates to positive electrode active substance particles each comprising: a core particle X comprising a lithium nickelate composite oxide having a layer structure which is represented by the formula of Li1+aNi1-b-cCobMcO2 wherein M is at least one element selected from the group consisting of Mn, Al, B, Mg, Ti, Sn, Zn and Zr; a is a number of -0.1 to 0.2 (-0.1 ≤ a ≤ 0.2); b is a number of 0.05 to 0.5 (0.05 ≤ b ≤ 0.5); and c is a number of 0.01 to 0.4 (0.01 ≤ c ≤ 0.4); and a coating compound Y comprising at least one element selected from the group consisting of Al, Mg, Zr, Ti and Si, in which the coating compound Y has an average film thickness of 0.2 to 5 nm, a degree of crystallinity of 50 to 95%, a degree of epitaxy of 50 to 95% and a coating ratio (coverage) of 50 to 95%.