ALD-Coated High-Nickel Cathodes for LiOH Shelf-Life and Stability
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Solution Overview
Problem
High-nickel cathodes face structural instability and capacity fading due to lattice strain and oxygen loss during cycling, with challenges in achieving uniform dopant distribution and coating uniformity, and the need for improved shelf-life of lithium hydroxide to prevent transition to Li2CO3, which hinders calcination reactions.
Innovation Solution
A coated cathode material is produced using atomic layer deposition (ALD) of oxides, fluorides, or nitrides on a lithium precursor, followed by calcination under controlled conditions to form a lithium metal oxide, with subsequent doping to enhance stability and inhibit Li2CO3 formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If lithium hydroxide is stored under open-air or controlled atmosphere, then it transitions to Li2CO3, but this transition delays calcination reaction and hinders formation of good LiNiO2-based cathode
Solution Approach 1:
A protective coating is applied to the lithium hydroxide precursor before calcination to prevent premature reaction with atmospheric CO2. This preliminary protective action maintains LiOH stability during storage and handling, while the coating is designed to be removed or decomposed during the calcination process, thus preventing both carbonate formation and hindrance to the calcination reaction.
Solution Approach 2:
The protective coating acts as an intermediary layer that isolates lithium hydroxide from atmospheric CO2 during storage. This intermediary prevents direct contact between LiOH and CO2, maintaining composition stability. During calcination, the intermediary layer is removed or transforms, allowing the calcination reaction to proceed efficiently.
2Use of energy by moving object
If high-nickel cathodes are cycled at high states of charge, then energy density is improved, but structural instability and oxygen loss occur causing severe capacity fading
Solution Approach 1:
Dopant elements are introduced at specific local positions within the cathode material structure (bulk doping) and/or as surface coatings to provide localized structural stabilization. This allows high-nickel composition for high energy density while the locally distributed dopants prevent structural collapse and oxygen loss during high-voltage cycling.
Solution Approach 2:
The cathode material is designed as a composite structure combining high-nickel LiNiO2 with dopant elements (such as Al, Ti, Zr, Nb) that provide structural stability. This composite approach maintains the high energy density of the nickel-rich base material while the dopant phases or regions prevent structural degradation during cycling at high states of charge.
3Reliability
If uniform dopant distribution is achieved through modification of atomic structure, then structural stability is improved, but difficulty in realizing uniformity of dopant element and coating compounds remains
Solution Approach 1:
Dopant elements are incorporated into the lithium hydroxide precursor material before the calcination process. This preliminary doping ensures uniform distribution of dopants throughout the precursor, which then translates to uniform dopant distribution in the final cathode material after calcination, achieving both structural stability and manufacturing precision.
Solution Approach 2:
The synthesis process merges the doping step with the precursor preparation step. Instead of separate doping and synthesis operations, the dopant incorporation is combined with the lithium hydroxide precursor formation, ensuring homogeneous distribution. The coating and doping processes are also merged into a unified approach applied to the same precursor material.
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 method achieves uniform elemental distribution, improves structural stability, reduces capacity loss, and extends the shelf-life of lithium hydroxide by preventing Li2CO3 formation, leading to enhanced performance and cycling stability of high-nickel cathodes.
Implementation Method 1
selectively depositing an oxide, fluoride, nitride, or a combination thereof on the lithium precursor by atomic layer deposition (ALD)
Implementation Method 2
calcining the prepared mixture at a temperature equal to or lower than 700° C. under pure O2 gas atmosphere
Data Source
AI summary
A coated cathode material including high-nickel lithium cathode and a method of producing the same by atomic layer deposition.