LiCoO2 Cathode Electrolyte Design for High-Voltage Cycle Stability
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Solution Overview
Problem
Lithium-ion batteries using LiCoO2 as the positive active material suffer from poor performance at high voltages greater than 4.2 V, leading to lattice deformation, bulk structure degradation, and instability due to deep delithiation, resulting in rapid capacity loss and safety concerns.
Innovation Solution
The use of a metal ion M-doped lithium cobalt oxide material Lix1Coy1M1−y1O2−z1Qz1 as the positive active material, where M serves as a framework, and an electrolytic solution containing vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, and a polynitrile six-membered nitrogen-heterocyclic compound to form a stable complex layer on the positive active material, reducing surface activity and side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiCoO2 is used as positive active material and voltage is increased greater than 4.2 V to extract more lithium ions, then capacity is improved, but structural stability deteriorates due to lattice deformation and bulk structure collapse
Solution Approach 1:
The patent modifies the chemical composition parameters of LiCoO2 by doping with metal ions (Ni, Cu, Zn, Mn, Fe, Al, Ti, Zr, Nb, Ta, Mo, W, or their combinations) at controlled concentrations (0.01-0.5 mol ratio). This parameter change stabilizes the crystal structure at high voltages while maintaining lithium ion extraction capability above 4.2V, resolving the contradiction between capacity improvement and structural stability
Solution Approach 2:
The patent creates composite materials by combining LiCoO2 with metal ion-doped variants (LiCo1-xMxO2 where M represents dopant elements). These composite structures provide both the high capacity of LiCoO2 and the structural stability of doped variants, enabling operation at voltages greater than 4.2V without bulk structure collapse
2Quantity of substance
If deep delithiation is performed to increase capacity, then more lithium ions are extracted, but harmful factors increase due to Co4+ oxidation and electrolyte decomposition
Solution Approach 1:
The patent introduces metal ion-doped LiCoO2 as an intermediary material that mediates between the electrode and electrolyte. The doped structure reduces surface activity and suppresses Co4+ formation, thereby preventing electrolyte decomposition and gas production while still enabling deep lithium ion extraction at high voltages
Solution Approach 2:
The patent converts the potentially harmful deep delithiation process into a beneficial outcome by using metal ion doping. The doping elements stabilize the structure during deep delithiation, transforming what would be a destructive process into a capacity-enhancing process that occurs without significant gas production or electrolyte degradation
3Power
If high voltage operation is implemented to improve energy density, then power and energy capacity are enhanced, but reliability decreases due to rapid capacity loss
Solution Approach 1:
The patent changes the compositional parameters of LiCoO2 through metal ion doping, which fundamentally alters the voltage-capacity characteristics. The doped materials maintain stable performance at high voltages (4.2-4.4V), enabling high energy density operation with improved cycle life and capacity retention compared to conventional LiCoO2
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
This configuration enhances the structural stability of the lithium-ion battery at high voltages, improves cycle performance and storage performance, and significantly reduces gas production and thickness expansion, especially under high-temperature and high-voltage conditions.
Implementation Method 1
M serves as a framework, reducing lattice deformation of the lithium cobalt oxide material during deep delithiation, and delaying degradation of bulk structure
Implementation Method 2
an electrolytic solution containing vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, and a polynitrile six-membered nitrogen-heterocyclic compound to form a stable complex layer on the positive active material
Implementation Method 3
form a stable complex layer on the positive active material, reducing surface activity and side reactions
Implementation Method 4
significantly reduces gas production and thickness expansion, especially under high-temperature and high-voltage conditions
Data Source
AI summary
The present application provides a lithium-ion battery and an apparatus, and the lithium-ion battery includes an electrode assembly and an electrolytic solution, the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separation film. A positive active material of the positive electrode sheet includes Lix1Coy1M1−y1O2−z1Qz1, 0.5≤x1≤1.2, 0.8≤y1≤1.0, 0≤z1≤0.1, M is selected from one or more of Al, Ti, Zr, Y, and Mg, and Q is selected from one or more of F, Cl, and S. The electrolytic solution contains vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, and an additive A. The additive A is a polynitrile six-membered nitrogen-heterocyclic compound with a relatively low oxidation potential. The lithium-ion battery has superb cycle performance and storage performance, especially under high-temperature and high-voltage conditions.