Lithium-Rich Cathode Coating for Capacity Retention
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Solution Overview
Problem
Current lithium ion batteries face limitations in achieving high specific discharge capacities and stable cycling performance, with significant irreversible capacity loss and reduced capacity over cycles, especially at moderate discharge rates.
Innovation Solution
Development of a positive electrode active material with a layered lithium metal oxide structure coated with a metal fluoride, synthesized using co-precipitation and sol-gel methods, which reduces irreversible capacity loss and maintains high specific discharge capacity over multiple cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional lithium-based cathode materials (LiCoO2, LiMn2O4, LiFePO4) are used, then commercial battery applications are achieved, but specific discharge capacity is limited to roughly 50% of theoretical capacity (around 140 mAh/g for LiCoO2)
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating lithium-rich layered oxide materials with specific stoichiometries (e.g., Li1.2Ni0.13Co0.1Mn0.57O2) that enable higher specific discharge capacities exceeding 240 mAh/g at C/3 rate, while maintaining structural stability through controlled metal cation ratios and oxidation states
Solution Approach 2:
The patent creates composite structures by coating the lithium-rich layered oxide core with protective layers (such as Li2SiO3 or Al2O3) that stabilize the crystal structure during cycling, enabling both high capacity retention (97-98% after 50 cycles) and enhanced electrochemical performance
2Power
If high current delivery is designed for high power applications, then power output is improved, but total energy and capacity are reduced
Solution Approach 1:
The patent designs electrodes with dynamic lithium ion diffusion pathways through optimized layered structures and controlled particle morphologies, enabling the material to adaptively respond to varying current rates and maintain high capacity utilization across different power demands
3Quantity of substance
If lithium-rich layered oxide materials are used to achieve high specific capacity, then discharge capacity exceeds 240 mAh/g, but irreversible capacity loss and cycling instability occur
Solution Approach 1:
The patent introduces intermediary protective coating layers (such as Li2SiO3, Al2O3, or fluorinated compounds) that act as mediators between the lithium-rich layered oxide and the electrolyte, reducing direct harmful interactions and minimizing irreversible capacity loss while preserving high discharge capacity
Solution Approach 2:
The patent converts the inherently unstable surface chemistry of lithium-rich materials into a benefit by inducing controlled surface modifications and forming stable solid electrolyte interphase (SEI) layers that protect the bulk material from degradation, thereby improving cycling stability
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 coated lithium metal oxide materials exhibit improved cycling performance, maintaining at least 98% of the 5th cycle discharge capacity at the 20th cycle and reducing irreversible capacity loss, thereby enhancing the overall energy density and stability of lithium ion batteries.
Implementation Method 1
The material has a metal/metalloid fluoride coating wherein the positive electrode material has a first cycle irreversible capacity loss at a discharge rate of C/10 of no more than about 2/3 of the first cycle irreversible capacity loss of the uncoated material
Implementation Method 2
lithium ion secondary batteries generally have a negative electrode material that intercalates lithium
Data Source
AI summary
Positive electrode active materials are described that have a very high specific discharge capacity upon cycling at room temperature and at a moderate discharge rate. Some materials of interest have the formula Li1+xNiαMnβCOγO2, where x ranges from about 0.05 to about 0.25, α ranges from about 0.1 to about 0.4, β ranges from about 0.4 to about 0.65, and γ ranges from about 0.05 to about 0.3. The materials can be coated with a metal fluoride to improve the performance of the materials especially upon cycling. Also, the coated materials can exhibit a very significant decrease in the irreversible capacity lose upon the first charge and discharge of the cell. Methods for producing these materials include, for example, a co-precipitation approach involving metal hydroxides and sol-gel approaches.