NMC811 Cathode Alumina Coating and Zr Doping for Cycle Stability
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Solution Overview
Problem
Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) lithium ion battery cathodes face significant capacity fading and poor thermal characteristics due to surface degradation, parasitic reactions, and structural instability, limiting their application in electric vehicles.
Innovation Solution
A lithium ion battery cathode is developed with a doped lithium metal oxide comprising zirconium and an alumina coating, achieved through atomic layer deposition and post-annealing, which enhances structural stability and electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) is used as cathode material to achieve high specific capacity and high average voltage, then energy density is improved, but capacity fading and thermal instability worsen due to surface degradation and structural instability
Solution Approach 1:
The patent applies composite materials by combining NMC811 cathode material with alumina (Al2O3) coating and zirconium doping. The alumina coating layer forms a protective composite structure on the NMC811 surface, while zirconium elements are doped into the NMC811 lattice. This composite approach maintains the high energy density of NMC811 while the alumina coating and zirconium doping work together to suppress capacity fading and improve thermal stability by preventing surface degradation and structural collapse.
2Use of energy by moving object
If Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) is used to achieve high specific capacity, then energy density is improved, but thermal characteristic worsens due to parasitic reactions catalyzed by transition metals on the cathode surface
Solution Approach 1:
The alumina coating serves as an intermediary layer between the NMC811 cathode material and the electrolyte. This intermediate alumina layer prevents direct contact between the transition metals in NMC811 and the electrolyte, thereby suppressing parasitic reactions that would otherwise be catalyzed by the exposed transition metal surfaces. The zirconium doping also acts as an intermediary by stabilizing the crystal structure and reducing surface reactivity, further improving thermal characteristics while maintaining high specific capacity.
3Stability of the object's composition
If degree of discharge or upper cutoff voltage is limited to prevent H2→H3 phase transition and lattice collapse, then structural stability is improved, but energy density decreases
Solution Approach 1:
The alumina coating and zirconium doping are applied in advance (preliminarily) to the NMC811 cathode material before it undergoes cycling. The alumina coating is deposited on the surface and zirconium is doped into the lattice structure beforehand, creating a protective framework that prevents the H2→H3 phase transition and lattice collapse during subsequent high-voltage charging. This preliminary protection enables the battery to operate at higher cutoff voltages (up to 4.5V) without suffering from structural degradation, thereby maintaining both structural stability and high energy density.
4Duration of action of stationary object
If surface coating is applied to extend cycle life of Ni-rich LIB cathode, then cyclic stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges multiple functions into a single integrated approach: the alumina coating process simultaneously provides surface protection, suppresses parasitic reactions, and the subsequent annealing treatment combines coating formation with zirconium doping in one thermal processing step. This merged approach extends cycle life through improved cyclic stability while avoiding the need for separate, complex manufacturing steps for coating and doping, thereby reducing overall manufacturing complexity.
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 combination of zirconium doping and alumina coating significantly improves the discharge capacity retention and structural stability of NMC811 cathodes, maintaining 85.9% of the initial capacity after 200 cycles, outperforming other modification methods.
Implementation Method 1
a doped lithium metal oxide comprising a dopant comprising zirconium
Implementation Method 2
a coating comprising alumina at least partially coating the doped lithium metal oxide
Implementation Method 3
achieved through atomic layer deposition and post-annealing
Implementation Method 4
post-annealing emerged as an effective method to address instability of cathode materials
Data Source
AI summary
The present invention relates to various lithium ion battery cathodes as well as lithium ion batteries incorporating one or more of these cathodes. The present invention further relates to processes of preparing the lithium ion battery cathode.