Li Gradient Cathode Particles for HACR Oxygen Loss
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Solution Overview
Problem
Lithium-ion battery cathodes, particularly HACR cathodes, face limitations in cycling capacity and voltage fading due to irreversibilities associated with anionic redox reactions, leading to structural defects and oxygen loss, which reduces their performance and lifespan.
Innovation Solution
A transition metal oxide particle with a Li-rich core and a Li-poor surface region, featuring a gradient in Li concentration, is developed to enhance capacity and reduce degradation. The Li-poor surface region suppresses anionic-redox activity, preventing oxygen loss and structural collapse, while the Li-rich core region maintains anionic-redox activity for capacity contribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If anionic redox reactions are utilized to increase capacity in HACR cathodes, then energy density is improved, but structural stability deteriorates due to oxygen loss and structural defects
Solution Approach 1:
The patent applies local quality by creating a lithium concentration gradient within the cathode particle, where the surface region has lower lithium concentration to suppress anionic redox activity and prevent oxygen loss, while the core region has higher lithium concentration to maintain anionic redox activity for high capacity. This spatial variation in lithium concentration allows different regions to perform different functions, resolving the contradiction between energy density and structural stability.
2Use of energy by moving object
If lithium concentration is increased to enhance anionic redox activity and capacity, then energy density is improved, but cycling performance deteriorates due to increased structural degradation
Solution Approach 1:
The patent implements local quality by establishing a lithium concentration gradient where the core region has high lithium concentration (Li1+X(r)M1−X(r)O2 with X(r) > 0) to provide high capacity through anionic redox, while the surface region has lower or negative lithium concentration (X(r) ≤ 0) to suppress structural degradation. This spatial differentiation allows the material to achieve both high capacity and good cycling performance.
Solution Approach 2:
The patent applies preliminary action by pre-forming the lithium concentration gradient structure before battery cycling begins. The gradient structure is created through controlled synthesis methods that establish the desired lithium distribution pattern in advance, so that during subsequent cycling, the surface region is already prepared to protect against oxygen loss while the core region is ready to provide high capacity.
3Ease of manufacture
If uniform lithium distribution is used to simplify material structure, then manufacturing is easier, but electrochemical performance deteriorates due to lack of protective surface region
Solution Approach 1:
The patent applies local quality by creating a lithium concentration gradient that differentiates between surface and core regions. The surface region has reduced lithium concentration to suppress anionic redox activity and prevent oxygen loss, while the core region has enhanced lithium concentration to maximize capacity. This spatial variation in composition optimizes both protective and active functions, improving electrochemical performance despite increased 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 approach significantly improves the cycling performance and energy density of lithium-ion batteries by reducing anion loss and structural defects, leading to enhanced capacity retention and voltage stability over multiple cycles.
Implementation Method 1
The Li-poor surface region (e.g., Li0.95M1.05O2) substantially reduces or, in some instances, mitigates anionic-redox activity, thus preventing the loss of anions from the cathode
Implementation Method 2
The Li-rich core region (e.g., Li1.2M0.8O2) provides capacity to the particle from both anionic-redox (e.g., oxygen anions) and cationic-redox (e.g., lithium cations) contributions
Implementation Method 3
The Li-rich core region (e.g., Li1.2M0.8O2) provides capacity to the particle from both anionic-redox (e.g., oxygen anions) and cationic-redox (e.g., lithium cations) contributions
Implementation Method 4
a gradient region, disposed between the core region and the surface region, with a Li concentration profile that varies from the first Li concentration to the second Li concentration
Data Source
AI summary
Previous hybrid-anion and cation-redox (HACR) cathodes were limited in cycling performance by irreversible anionic redox reactions caused by the loss of anions. To overcome this limitation, a lithium (Li) transition metal (M) oxide particle is described having a Li concentration gradient. In one example, the particle includes a Li-rich core region that provides capacity and energy density due anionic and cationic contributions and a Li-poor surface region surrounding the core region to inhibit anionic activity and thus substantially reduce the loss of anions. A gradient region disposed between the core and surface regions has a Li concentration profile that varies from a first Li concentration in the core region to a second Li concentration in the surface region. A high-temperature leaching method may be used to leach LiO from a Li-rich Li1+xM1−XO2 particle, thus forming a coherent Li gradient with a stabilized layered structure.