Lithium-Ion Battery Cathode Coating for Cycling Stability
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Solution Overview
Problem
Lithium-ion batteries face limitations in achieving high specific discharge capacities and long cycling lives, with existing materials like LiCoO2, LiMn2O4, and LiFePO4 not providing significant improvements in energy density, and designs for high power or high energy applications often compromise on either power or energy delivery.
Innovation Solution
The development of lithium-ion batteries with a negative electrode of graphite and a positive electrode comprising a lithium intercalation composition, such as lithium rich layered lithium metal oxides like Li1+xNiαMnβCoγO2, coated with metal fluoride, and a non-aqueous electrolyte with stabilizing additives, which maintains at least 70% discharge capacity over 1000 cycles and achieves high specific energy densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional cathode materials like LiCoO2, LiMn2O4, or LiFePO4 are used, then the battery can be manufactured with current commercial processes, but the specific discharge capacity is limited to roughly 140 mAh/g with no significant improvement in energy density
Solution Approach 1:
The patent changes the chemical composition parameters of the cathode material by using lithium-rich layered oxides with excess lithium (Li1+x[Mn1-y-zNiycoz]O2 where x>0), achieving specific capacities exceeding 200 mAh/g while maintaining structural stability through controlled composition ratios
Solution Approach 2:
The patent creates a composite structure by coating the lithium-rich layered oxide core with a protective layer (such as Li2SiO3 or other ceramic coatings), combining the high capacity of the lithium-rich material with the stability and protection of the coating material to achieve both high specific capacity and long cycling life
2Power
If the battery is designed for high power applications to deliver high current, then the power delivery is improved, but the total energy and specific energy density are reduced
Solution Approach 1:
The patent optimizes the cathode material composition with lithium-rich layered structures that provide both high ionic conductivity for power delivery and high capacity for energy density, achieving a balance where the material can deliver high currents while maintaining specific energy density above 175 Wh/kg
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
These batteries exhibit excellent cycling performance, maintaining 70% capacity over 1000 cycles and achieving high specific energy densities, making them suitable for electric vehicles and other high-energy applications while reducing the need for frequent battery replacements and minimizing weight and volume.
Implementation Method 1
a positive electrode material that intercalates lithium
Implementation Method 2
The lithium intercalation composition of the positive electrode can have a coating comprising a metal fluoride
Implementation Method 3
the electrolyte of the battery can comprise a stabilizing additive
Data Source
AI summary
Batteries with high energy and high capacity are described that have a long cycle life upon cycling at a moderate discharge rate. Specifically, the batteries may have a room temperature fifth cycle discharge specific energy of at least about 175 Wh/kg discharged at a C/3 discharge rate from 4.2V to 2.5V. Additionally, the batteries can maintain at least about 70% discharge capacity at 1000 cycles relative to the fifth cycle, with the battery being discharged from 4.2V to 2.5V at a C/2 rate from the fifth cycle through the 1000th cycle. In some embodiment, the positive electrode of the battery comprises a lithium intercalation composition with optional metal fluoride coating. Stabilizing additive maybe added to the electrolyte of the battery to further improve the battery performance. The batteries are particularly suitable for use in electric vehicles.