Lithium-Ion Cathode Particles With Nonlinear Ni Gradient
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Solution Overview
Problem
Existing lithium-ion battery cathode materials face challenges in achieving high energy densities while maintaining interfacial stability, particularly due to trade-offs in composition that affect capacity retention and surface reactivity.
Innovation Solution
A method for preparing cathode particles with a non-linear continuous concentration gradient profile for transition metal components, allowing for increased nominal mole percent of Ni, Mn, or Co without altering the concentration gradient's thickness or initial/final transition metal composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the average Ni content of the NMC composition is increased to achieve high energy densities, then the initial capacity is improved, but the capacity retention during secondary cell cycling deteriorates and the interfacial stability worsens
Solution Approach 1:
The patent applies local quality by creating a concentration gradient within the cathode particle where the Ni content varies spatially - higher Ni content at the core for high capacity and lower Ni content at the surface for stability. This is achieved by controlling the precipitation process to establish a radial concentration gradient, allowing different regions of the same particle to have different compositional properties optimized for their specific functional requirements.
2Reliability
If a core-shell structure with large step change in NMC composition is prepared to protect the core, then the cycle life is improved, but the shell may delaminate and the manufacturing complexity increases
Solution Approach 1:
The patent transitions from a static core-shell structure with abrupt composition changes to a dynamic concentration gradient where the composition changes continuously and smoothly from core to surface. This dynamic approach eliminates the sharp interfaces that cause delamination while maintaining the protective effect, achieving a more stable and manufacturable structure through continuous precipitation control.
3Reliability
If a continuous concentration gradient with linear slope is used, then the interfacial stability is maintained, but the Ni content at the surface is the mean of core and surface composition which limits energy density
Solution Approach 1:
The patent applies asymmetry by creating a non-linear concentration gradient where the rate of composition change is not uniform throughout the particle. The gradient is designed to be more pronounced in certain regions and more gradual in others, allowing the surface Ni content to be lower than the linear mean while the core maintains high Ni content, thereby achieving both stability and high energy density through asymmetric distribution.
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 enhances capacity retention and maintains interfacial stability, enabling higher energy densities in lithium-ion battery cathodes by optimizing the concentration gradient profile.
Implementation Method 1
The method includes: feeding a feed stream (a) containing metal cations into a reactor; feeding a feed stream (b) containing anions into the reactor; wherein a ratio of the metal cations in the feed stream (a) is continuously changed from A1 at time t1 to A2 at time t2; wherein the feed stream (a) and the feed stream (b) are contacted in the reactor to form precipitated precursor particles
Data Source
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AI summary
A method of preparing cathode particles using a co-precipitation reaction in a reactor is disclosed. A feed stream (a) containing metal cations is fed into the reactor, and a feed stream (b) containing anions is fed into the reactor, wherein a ratio of the metal cations in the feed stream (a) is continuously changed from A1 at time t1 to A2 at time t2. The feed stream (a) and the feed stream (b) are contacted in the reactor to form precipitated precursor particles, and at least one transition metal component in the particle has a non-linear continuous concentration gradient profile over at least a portion along a thickness direction of the particle.