LiCoO2 Cathode Electrolyte Additives for High-Voltage Cycle Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion batteries using LiCoO2 as a positive active material face instability and rapid capacity decrease when operated at high voltages greater than 4.2 V due to lattice deformation, gas production, and side reactions, leading to poor performance and short cycle life.
Innovation Solution
A lithium-ion battery design incorporating a metal ion-doped lithium cobalt oxide material (Lix1Coy1M1-y1O2-z1Qz1) with a polynitrile six-membered nitrogen-heterocyclic compound additive in the electrolyte, which forms a stable complex layer on the positive active material to reduce surface activity and side reactions, and includes vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sultone to create a surface film with good chemical and electrochemical stability.
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 Co4+ instability
Solution Approach 1:
The patent modifies the chemical composition parameters of the positive active material by doping LiCoO2 with metal ions (Al, Ti, Zr, Y, or Mg) at controlled concentrations (0.01-0.1 mol ratio). This parameter change stabilizes the crystal structure at high voltages while maintaining lithium ion extraction capability above 4.2 V, preventing lattice collapse and Co4+ instability.
Solution Approach 2:
The patent creates a composite material system by incorporating metal ion-doped LiCoO2 particles with a protective coating layer formed through electrolyte additives. This composite structure combines the high capacity of LiCoO2 with the structural stability of doped regions and the protective barrier of the coating, enabling stable operation at voltages greater than 4.2 V.
2Quantity of substance
If deep delithiation is performed to increase capacity, then more lithium ions are extracted, but gas production increases due to electrolyte oxidation and HF corrosion
Solution Approach 1:
The patent introduces electrolyte additives (vinylene carbonate, fluoroethylene carbonate, and polynitrile six-membered nitrogen-heterocyclic compounds) as intermediary substances that form protective coating layers on the positive electrode surface. These intermediaries prevent direct contact between the electrolyte and the positive active material, blocking oxidation reactions and HF corrosion that produce gas, while still allowing lithium ion transport.
Solution Approach 2:
The patent applies preliminary protective action by forming a stable surface coating layer on the positive electrode before harmful reactions can occur. The electrolyte additives react first to create a protective barrier that prevents subsequent electrolyte oxidation and HF corrosion, thereby preventing gas production during deep delithiation and extended cycling.
3Quantity of substance
If high voltage operation greater than 4.2 V is implemented to increase energy density, then capacity is improved, but cycle life decreases due to surface activity and side reactions
Solution Approach 1:
The patent changes the surface chemistry parameters of the positive electrode by introducing metal ion doping and electrolyte additive coatings. These parameter changes reduce surface activity and suppress side reactions at high voltages, maintaining electrode integrity and lithium ion transport pathways throughout extended cycling, thereby extending cycle life while operating above 4.2 V.
Solution Approach 2:
The patent creates a composite electrode structure consisting of metal ion-doped LiCoO2 core particles with a protective coating layer formed from electrolyte additives. This composite structure maintains high capacity through the doped core while the coating layer protects against degradation during cycling, enabling stable performance at high voltages greater than 4.2 V over extended periods.
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 enhances the structural stability and cycle performance of lithium-ion batteries under high-temperature and high-voltage conditions, reducing gas production and extending cycle life while maintaining efficient lithium ion conduction.
Implementation Method 1
the additive A is selected from one or more of compounds represented by Formula I-1, Formula I-2, and Formula I-3... forms a stable complex layer on the positive active material
Implementation Method 2
includes vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sultone to create a surface film with good chemical and electrochemical stability
Implementation Method 3
lithium ions that are actually used account only for 1/2 of lithium ions actually contained in LiCoO2... efficient lithium ion conduction
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, 0.85≤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.