Cobalt-Free Li Battery Electrolyte Additive for High-Voltage Stability
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Solution Overview
Problem
Rechargeable lithium batteries using cobalt-free lithium nickel manganese-based oxide positive electrodes face issues with transition metal elution under high voltage and high temperature conditions, leading to structural collapse, gas generation, and reduced 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 solution containing a specific additive, such as 2-fluoro-1,3,2-dioxaphospholane, to prevent transition metal elution and stabilize the electrolyte, thereby enhancing high-voltage and high-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If cobalt-free lithium nickel manganese-based oxide is used as positive active material to reduce cost and increase energy density, then manufacturing cost is reduced and energy density is improved, but transition metal elution occurs under high voltage conditions leading to structural collapse and performance deterioration
Solution Approach 1:
A coating layer comprising at least one of an oxide, oxyhydroxide, hydroxide, carbonate, or carboxylate of magnesium, calcium, strontium, barium, or rare earth elements is formed on the surface of the cobalt-free lithium nickel manganese-based oxide positive active material. This coating layer acts as an intermediary barrier that prevents direct contact between the electrolyte and transition metal atoms, thereby suppressing transition metal elution while allowing lithium ion diffusion. The coating layer resolves the contradiction by maintaining structural stability during high voltage operation without significantly increasing manufacturing complexity.
Solution Approach 2:
The patent modifies the surface composition and chemical state of the positive active material by introducing a coating layer with specific chemical properties (oxide, oxyhydroxide, hydroxide, carbonate, or carboxylate). This parameter change in surface chemistry creates a protective interface that stabilizes the structure under high voltage conditions while preserving the bulk material's high capacity characteristics.
2Use of energy by moving object
If high voltage operation is implemented to increase energy density, then energy density is improved, but transition metal elution is aggravated leading to gas generation and capacity reduction
Solution Approach 1:
The coating layer serves as a protective intermediary that enables high voltage operation by preventing direct electrochemical reactions between the electrolyte and transition metal atoms. This intermediary layer suppresses transition metal elution and associated harmful effects (gas generation, capacity reduction) while allowing the battery to operate at high voltages for increased energy density.
Solution Approach 2:
The coating layer is formed preliminarily on the surface of the positive active material before battery operation. This preliminary protective action prevents transition metal elution from occurring in the first place during high voltage operation, rather than attempting to address elution after it has begun.
3Power
If high temperature operation is permitted to increase power output, then power output is improved, but transition metal elution is aggravated causing side reactions and increased battery resistance
Solution Approach 1:
The coating layer acts as a thermal and chemical barrier that reduces transition metal elution under high temperature conditions. By preventing direct contact between the electrolyte and positive active material surface, the coating layer suppresses thermally-accelerated elution processes and associated side reactions, enabling safer high-temperature operation for improved power output.
4Ease of operation
If electrolyte solution is used to enable ion transport, then electrochemical function is achieved, but electrolyte oxidation occurs in high voltage region leading to positive electrode performance deterioration
Solution Approach 1:
The coating layer serves as a physical and chemical barrier that prevents direct contact between the electrolyte solution and the positive active material surface. This intermediary layer suppresses electrolyte oxidation reactions that would otherwise occur at high voltages, thereby maintaining electrolyte stability while preserving electrochemical function.
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 reduces transition metal elution, suppresses structural collapse, and improves battery stability and cycle-life characteristics, maintaining performance under high voltage and high temperature conditions.
Implementation Method 1
a compound represented by Chemical Formula 1... In Chemical Formula 1, each of R1 to R6 may independently be a fluorine atom or a hydrogen atom
Data Source
Figure 1
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 active material; and a negative electrode including a negative active material, wherein the additive is a compound represented by Chemical Formula 1, and the positive active material includes a cobalt-free lithium nickel manganese-based oxide. Details of Chemical Formula 1 are as described in the specification.