Low-EC Electrolyte for High-Voltage Nickel-Manganese Lithium Batteries
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Solution Overview
Problem
Rechargeable lithium batteries using cobalt-free lithium nickel manganese-based oxide positive electrodes face structural collapse and transition metal elution under high-voltage and high-temperature conditions, leading to capacity reduction, increased resistance, and deteriorated cycle-life characteristics.
Innovation Solution
A rechargeable lithium battery design incorporating a non-aqueous organic solvent with less than 5 wt% ethylene carbonate, a lithium nickel manganese-based oxide positive electrode, and specific additives to reduce transition metal elution and stabilize the electrode structure, combined with a negative electrode material like graphite or Si composite, to enhance high-voltage and high-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a high voltage range is used to increase energy density, then energy density is improved, but positive electrode performance deteriorates due to electrolyte oxidization
Solution Approach 1:
A coating layer comprising a compound of formula (1) is formed on the surface of the positive electrode active material particles. This coating layer acts as an intermediary between the electrolyte and the positive electrode active material, preventing direct contact and harmful oxidization reactions while allowing lithium ion diffusion. The coating layer specifically suppresses electrolyte oxidization at high voltages, enabling the use of higher charging voltages (4.35V or higher) to increase energy density without compromising positive electrode performance.
2Use of energy by moving object
If cobalt-free lithium nickel manganese-based oxide is used to reduce cost and increase energy density, then cost and energy density are improved, but structural collapse and transition metal elution occur under high voltage conditions
Solution Approach 1:
The coating layer of compound (1) serves as a protective intermediary that prevents direct exposure of the cobalt-free lithium nickel manganese-based oxide to the electrolyte under high voltage conditions. This intermediary layer suppresses transition metal elution and prevents structural collapse, maintaining the stability of the positive electrode structure while enabling the use of cost-effective cobalt-free materials with high energy density.
Solution Approach 2:
The patent modifies the chemical composition parameters of the coating layer by using a compound with specific formula (1) containing particular functional groups. This parameter change in the coating composition provides enhanced protection against structural degradation and metal elution compared to conventional coatings, enabling stable operation of cobalt-free high-nickel cathodes at high voltages.
3Speed
If high temperature environment is used to increase reaction rate, then charging speed is improved, but transition metal elution is aggravated and battery resistance increases
Solution Approach 1:
The coating layer of compound (1) acts as a thermal and chemical barrier between the positive electrode active material and the electrolyte. Under high temperature conditions, this intermediary layer suppresses the aggravated transition metal elution that would otherwise occur, preventing metal precipitation on the negative electrode and avoiding side reactions that increase battery resistance. This enables faster charging at elevated temperatures without compromising reliability.
4Productivity
If transition metals are eluted and precipitated on negative electrode surface, then side reactions increase, but battery cycle-life and output characteristics deteriorate
Solution Approach 1:
The coating layer of compound (1) is applied in advance to the positive electrode active material surface to prevent transition metal elution before it can occur during battery operation. This preliminary protective action blocks the source of eluted metals, preventing their transport and precipitation on the negative electrode surface. By preventing the root cause of side reactions, the coating layer preserves battery cycle-life and maintains output characteristics over extended cycling.
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 elution of transition metals, improving battery stability, cycle-life, and reducing internal resistance, thereby enhancing the battery's high-voltage and high-temperature characteristics.
Implementation Method 1
the electrolyte capable of effectively protecting the positive electrode including a lithium nickel manganese-based oxide to reduce elution of transition metals under high-voltage and high-temperature conditions
Implementation Method 2
the additive includes a compound represented by Chemical Formula 1... effectively protecting the positive electrode including a lithium nickel manganese-based oxide to reduce elution of transition metals
Implementation Method 3
improving battery stability, cycle-life, and reducing internal resistance, thereby enhancing the battery's high-voltage and high-temperature characteristics
Data Source
AI summary
A rechargeable lithium battery including an electrolyte including a non-aqueous organic solvent, a lithium salt, and an additive; positive electrode including a positive electrode active material; and a negative electrode including a negative electrode active material, wherein the non-aqueous organic solvent includes less than about 5 wt % of ethylene carbonate based on the total weight of the non-aqueous organic solvent, the positive electrode active material includes a lithium nickel manganese-based oxide, and the additive includes a compound represented by Chemical Formula 1.