High-Voltage Lithium Battery Electrolyte for Cobalt-Free Cathode Stability
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Solution Overview
Problem
Cobalt-free lithium nickel manganese-based oxide positive electrodes in rechargeable lithium batteries face structural collapse and transition metal elution at high voltage and temperature, leading to capacity reduction, increased resistance, and deteriorated cycle-life characteristics.
Innovation Solution
A rechargeable lithium battery design combining a cobalt-free lithium nickel manganese-based oxide positive electrode with a specialized electrolyte solution containing specific additives and a non-aqueous organic solvent mixture, forming a protective layer to prevent transition metal elution and structural instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the charging upper limit voltage is increased to expand the voltage range and increase energy density, then the energy density is improved, but the positive electrode structure collapses and transition metals elute due to oxidization of the electrolyte solution
Solution Approach 1:
A coating layer comprising at least one of an oxide, oxyhydroxide, hydroxide, carbonate, or carboxylate of a coating element is formed on the surface of the positive electrode active material particles. This coating layer acts as an intermediary barrier between the positive electrode and the electrolyte solution, preventing direct contact and chemical reactions at the interface, thereby suppressing transition metal elution and electrolyte oxidization even at high charging voltages of 4.4V or higher
Solution Approach 2:
The positive electrode is constructed as a composite structure where the core consists of high-capacity lithium nickel manganese-based oxide (cobalt-free) and the surface is coated with protective materials (oxides, oxyhydroxides, hydroxides, carbonates, or carboxylates of coating elements). This composite structure combines the high energy density benefits of cobalt-free materials with the protective properties of the coating layer, enabling stable operation at elevated voltages
2Duration of action of stationary object
If the positive electrode structure is stabilized to prevent transition metal elution, then the cycle-life characteristics are improved, but the battery resistance increases due to precipitated transition metals on the negative electrode
Solution Approach 1:
The coating layer on the positive electrode serves as a protective barrier that prevents transition metals from eluting into the electrolyte and subsequently precipitating on the negative electrode. By blocking the source of transition metal contamination at the positive electrode surface, the coating layer protects the negative electrode from forming resistive deposits, thereby maintaining low battery resistance over extended cycling
Solution Approach 2:
The harmful transition metals (nickel and manganese) are extracted or contained within the positive electrode structure through the coating layer, preventing them from migrating to the negative electrode. This extraction of the harmful element from the system prevents the side reactions and resistance increase that would otherwise occur
3Ease of manufacture
If cobalt-free lithium nickel manganese-based oxide is used to reduce cost and increase energy density, then the manufacturing cost is reduced and energy density is improved, but the positive electrode deteriorates due to structural collapse at high voltage
Solution Approach 1:
The positive electrode employs a composite structure where cobalt-free lithium nickel manganese-based oxide particles are coated with a protective layer of oxide, oxyhydroxide, hydroxide, carbonate, or carboxylate of a coating element. This composite design maintains the cost and energy density advantages of cobalt-free materials while adding structural stability through the protective coating, enabling high-voltage operation without structural collapse
Solution Approach 2:
The coating element is selected from specific metals (magnesium, calcium, strontium, barium, scandium, yttrium, or rare earth elements) that provide localized structural support and chemical stability at the critical electrode-electrolyte interface. This local quality enhancement at the surface level protects the bulk cobalt-free material from degradation while maintaining its inherent cost and performance benefits
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 battery stability and cycle-life characteristics by forming a protective layer that reduces gas generation and internal resistance, improving high-voltage and high-temperature performance.
Implementation Method 1
an electrolyte solution capable of effectively protecting the positive electrode including cobalt-free lithium nickel manganese-based oxide to reduce elution of transition metals under high-voltage and high-temperature conditions
Implementation Method 2
the additive includes one or more of a compound represented by Chemical Formula 1A and a compound represented by Chemical Formula 1B
Data Source
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AI summary
Provided is a rechargeable lithium battery including an electrolyte solution 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 one or more of a compound represented by Chemical Formula 1A and a compound represented by Chemical Formula 1B, the positive electrode active material includes a lithium nickel manganese-based oxide represented by Chemical Formula 2, and a charging upper limit voltage of the rechargeable lithium battery is about 4.4 V to about 4.7 V. Chemical Formula 1A and Chemical Formula 1B are as defined in the specification.