Lithium-Ion Cathode Composition for High-Voltage Cycle Stability
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Solution Overview
Problem
Lithium-ion batteries using LiCoO2 as a positive active material face performance degradation at high voltages due to lattice instability, gas generation, and reduced cycle life, primarily because of Co3+ oxidation and HF corrosion, leading to poor high-voltage performance.
Innovation Solution
A lithium-ion battery design incorporating a metal-ion doped lithium cobalt oxide material with a ternary material and a six-membered nitrogen heterocyclic compound additive in the electrolyte, which stabilizes the lattice, reduces gas production, and enhances thermal stability, forming a passivation layer to inhibit surface reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiCoO2 is used as positive active material and cycled between fully discharged LiCoO2 and semi-charged Li0.5CoO2 at 4.2V, then stable performance is achieved, but only 1/2 of lithium ion content is utilized
Solution Approach 1:
The patent changes the voltage parameter from 4.2V to higher than 4.2V, and modifies the chemical composition parameter by introducing metal element M doping into LiCoO2 lattice, enabling extraction of more lithium ions (greater than 50% utilization) while maintaining structural stability through the doping effect
2Quantity of substance
If voltage is greater than 4.2V to extract remaining lithium ions, then lithium ion content utilization is improved, but lattice instability and performance degradation occur due to Co3+ oxidation
Solution Approach 1:
The patent creates a composite material system by doping metal element M into LiCoO2 lattice, forming LiCoO2-M composite structure that combines the high lithium ion content of LiCoO2 with the stabilizing effect of metal element M, enabling high voltage operation with improved lattice stability
Solution Approach 2:
The patent applies local quality modification by introducing metal element M at specific doping concentrations (0.01-0.5 mole ratio) into the LiCoO2 lattice at specific sites, creating localized structural modifications that prevent Co3+ oxidation while maintaining overall material properties for high lithium ion utilization
3Quantity of substance
If deep delithiation is performed at high voltage, then lithium ion content utilization is improved, but gas generation increases due to HF corrosion
Solution Approach 1:
The patent converts the potentially harmful high voltage deep delithiation process into a beneficial outcome by using metal element M doping to stabilize the lattice, transforming what would be a damaging condition into an effective method for achieving high lithium ion utilization without excessive gas generation
4Use of energy by moving object
If high voltage operation is implemented, then energy density is improved, but cycle life is reduced due to structural degradation
Solution Approach 1:
The patent applies preliminary action by pre-doping metal element M into the LiCoO2 lattice before high voltage operation, creating a pre-stabilized structure that is prepared to withstand the stresses of high voltage cycling, thereby extending cycle life while maintaining high energy density
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 solution significantly improves cycle and storage performance, especially under high temperature and high voltage conditions, by stabilizing the lithium cobalt oxide material and reducing side reactions, thereby extending battery life and maintaining energy density.
Implementation Method 1
forming a passivation layer to inhibit surface reactions
Implementation Method 2
doping element M serves as a skeleton in the lithium cobalt oxide material, and can reduce lattice deformation amount in the process of deep delithiation
Implementation Method 3
with a low oxidation potential... effectively passivate the surface of the positive active material, reduce activity of the surface
Data Source
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AI summary
The present application provides a lithium-ion battery and an apparatus, the lithium-ion battery includes an electrode assembly and an electrolyte, the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator. A positive active material of the positive electrode sheet includes both Lix1Coy1M11-y1O2-aQ1a and Li1Nim1Con1M2pM3qO2-bQ2b, a mass ratio of Lix1Coy1M11-y1O2-aQ1a and Li1Nim1Con1M2pM3qO2-bQ2b is 1:1-9:1. The electrolyte contains an additive A, the additive A is a six-membered nitrogen heterocyclic compound with multiple nitrile groups and with low oxidation potential. The lithium-ion battery according to the present application has excellent cycle performance and storage performance, especially having excellent cycle performance and storage performance under high temperature and high voltage conditions.