Electrolyte Additives for Cobalt-Free Lithium Cathode Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rechargeable lithium batteries using cobalt-free lithium nickel manganese-based oxide positive electrodes face issues with transition metal elution and structural collapse under high-voltage and high-temperature conditions, leading to capacity reduction, increased battery resistance, and deteriorated cycle-life and output characteristics.
Innovation Solution
A rechargeable lithium battery design incorporating a positive electrode with cobalt-free lithium nickel manganese-based oxide and an electrolyte containing specific additives such as nitrile groups and cyclic phosphazene, which stabilizes the electrode structure and reduces metal elution, thereby enhancing high-voltage and high-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cobalt-free lithium nickel manganese-based oxide is used as positive electrode active material to achieve high energy density and economical cost, then energy density and cost-effectiveness are improved, but transition metal elution occurs under high-voltage conditions causing structural collapse, capacity reduction, and gas generation
Solution Approach 1:
The patent introduces a coating layer comprising aluminum oxide (Al2O3) and/or aluminum hydroxide (Al(OH)3) as an intermediary protective barrier between the cobalt-free lithium nickel manganese-based oxide positive electrode and the electrolyte. This coating layer prevents direct contact and chemical reactions, thereby suppressing transition metal elution while maintaining high energy density performance
Solution Approach 2:
The patent employs a composite structure where the positive electrode consists of cobalt-free lithium nickel manganese-based oxide combined with aluminum-based coating materials (Al2O3 and/or Al(OH)3). This composite material approach provides both high capacity from the nickel manganese oxide and structural stability from the aluminum-based coating, resolving the contradiction between energy density and reliability
2Quantity of substance
If high-voltage operation is implemented to increase energy density, then energy density is improved, but electrolyte oxidation occurs leading to performance deterioration of positive electrode
Solution Approach 1:
The aluminum oxide and aluminum hydroxide coating layer acts as a protective intermediary that prevents direct contact between the positive electrode and electrolyte under high-voltage conditions. This barrier suppresses electrolyte oxidation reactions while allowing the battery to operate at high voltages for increased energy density
Solution Approach 2:
The aluminum-based coating layer creates an inert protective environment around the positive electrode, preventing oxidative reactions between the electrolyte and electrode materials under high-voltage operation. This inert barrier maintains electrode performance stability
3Power
If high-temperature operation occurs, then battery power output may be improved, but transition metal elution is aggravated causing side reactions, increased resistance, and deteriorated cycle-life
Solution Approach 1:
The aluminum oxide and aluminum hydroxide coating layer serves as a thermally stable intermediary barrier that prevents transition metal elution even under high-temperature conditions. This protective layer maintains its integrity at elevated temperatures, preventing side reactions and preserving cycle-life while allowing high power output operation
4Reliability
If positive electrode structure is stabilized to prevent transition metal elution, then reliability is improved, but device complexity increases due to additional coating materials and processes
Solution Approach 1:
The patent optimizes the coating layer parameters by limiting aluminum oxide and aluminum hydroxide content to specific ranges (0.1-5 wt% each based on positive electrode active material weight). This parameter optimization provides sufficient protective function while minimizing the impact on manufacturing complexity and maintaining cost-effectiveness
Solution Approach 2:
The patent applies the aluminum-based coating selectively to the positive electrode surface where transition metal elution occurs, rather than throughout the entire battery structure. This localized approach provides targeted protection against elution while minimizing additional complexity in other battery components
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 effectively suppresses structural collapse and side reactions, improving battery stability, cycle-life, and reducing gas generation, allowing the battery to operate reliably at high voltages and temperatures.
Implementation Method 1
the additive includes at least one of the first compound and the second compound... the first compound is a substituted or unsubstituted C1 to C20 alkyl group including at least one nitrile group... the second compound is a cyclic phosphazene
Implementation Method 2
an electrolyte including a non-aqueous organic solvent, a lithium salt, and an additive
Data Source
AI summary
Provided is a rechargeable lithium battery including an electrolyte including a non-aqueous organic solvent, a lithium salt, and an additive; a positive electrode including a positive electrode active material; and a negative electrode including a negative electrode active material, wherein the additive includes at least one of the first compound and the second compound, the first compound is a substituted or unsubstituted C1 to C20 alkyl group including at least one nitrile group, a substituted or unsubstituted C2 to C20 alkenyl group including at least one nitrile group, a substituted or unsubstituted C2 to C20 alkynyl group including at least one nitrile group, a substituted or unsubstituted C1 to C20 alkoxy group including at least one nitrile group, a substituted or unsubstituted C6 to C20 aryl group including at least one nitrile group, or a combination of thereof, the second compound is cyclic phosphazene, and the positive electrode active material includes cobalt-free lithium nickel manganese-based oxide.