Aluminium-Substituted Lithium-Rich Cathode for Stable Oxygen Redox
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Solution Overview
Problem
Conventional lithium ion batteries are limited by the capacity of cathode materials, which rely heavily on transition metal ions for charge storage, leading to safety concerns and reduced energy density, as they struggle to effectively utilize anion redox chemistry without compromising stability during charge/discharge cycles.
Innovation Solution
A lithium-rich compound with a specific formula, Li(4-2x-y-z)NixCoyAlzO2, is developed, where x, y, and z are within defined ranges, incorporating nickel, cobalt, and aluminium to enhance oxygen redox activity and maintain charge balance, thereby increasing capacity and stability while reducing the need for heavy transition metals and avoiding undesired redox reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium rich blends of cathode materials containing nickel manganese cobalt oxide are used, then energy density is improved, but safety is compromised
Solution Approach 1:
The patent changes the chemical composition parameters by controlling the ratios of lithium, nickel, manganese, cobalt, and aluminum in the cathode material. Specifically, it uses lithium-rich compositions with excess lithium (x > 0) while maintaining controlled amounts of transition metals, and introduces aluminum substitution (z > 0) to stabilize the structure, thereby achieving high energy density while improving safety
Solution Approach 2:
The patent creates a composite cathode material combining multiple elements (Li, Ni, Mn, Co, Al, O) in a specific layered structure. The composite nature allows synergistic effects where aluminum substitution stabilizes the crystal structure during cycling, preventing catastrophic failures while the lithium-rich composition provides high capacity, thus resolving the safety-energy density trade-off
2Use of energy by moving object
If charge is stored on anions (oxygen) to increase capacity, then energy density is improved, but material stability deteriorates due to undesired redox reactions
Solution Approach 1:
The patent introduces aluminum as an intermediary element that mediates between the lithium ions and the oxygen anions. The aluminum substitution at transition metal sites (z > 0) creates a stabilizing effect on the oxygen sublattice, allowing oxygen redox reactions to occur reversibly without causing structural collapse or oxygen release, thus enabling high capacity while maintaining stability
Solution Approach 2:
The patent optimizes the aluminum content parameter (z) within a specific range (0 < z ≤ 0.3) to achieve the right balance between enabling oxygen redox activity and stabilizing the structure. This precise parameter control allows the material to access anion redox capacity while preventing the degradation that would otherwise occur
3Use of energy by moving object
If aluminum is substituted for cobalt ions, then energy density is improved by reducing heavy metal content, but charge balance may be affected
Solution Approach 1:
The patent adjusts the aluminum substitution parameter (z) and compensates by adjusting the lithium excess parameter (x) and transition metal parameters (y) to maintain charge balance. The specific formulation Li(1+x)Ni(1-y-z/2)Coy/2AlzO2 ensures that the +3 charge of aluminum substituting for cobalt is compensated by the overall charge neutrality maintained through the defined compositional relationships, allowing reduced cobalt content while preserving electrochemical functionality
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 compound achieves a significant increase in electrochemical capacity and stability over numerous cycles, maintaining charge storage efficiency without the need for additional layers, thus enhancing energy density and extending the battery's useful lifetime.
Implementation Method 1
The particular compound as defined above exhibits a significantly large increase in capacity due to the degree of oxidation of the transition metals, the aluminium and also the oxidation of the oxide ions within the lattice
Implementation Method 2
charge is stored in the transition metal cations within such cathode materials... rely on the redox chemistries of both the anions and cations to store charge
Implementation Method 3
the presence of a particular amount of nickel and/or cobalt with an amount of aluminium substitution enables greater oxygen redox activity and thereby improves the electrochemical capacity of the material
Implementation Method 4
the compounds of the present invention exhibit improved stability during electrochemical cycling when compared to the transition metal substituted NMC lithium rich materials of the prior art
Data Source
AI summary
A compound of the general formula:Li(43-2x3-y3-z3)NixCoyAlzMn(23-K3-2y3-2z3)O2wherein x is equal to or greater than 0 and equal to or less than 0.4; y is equal to or greater than 0.1 and equal to or less than 0.4; and z is equal to or greater than 0.02 and equal to or less than 0.3. The compound is also formulated into a positive electrode for use in an electrochemical cell.