Sulfate Ester Additive for Low-Temperature Battery Resistance
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries, such as lithium ion batteries, experience decreased performance due to increased internal resistance and reduced discharge capacity when subjected to repeated charge/discharge cycles or long-term storage, especially under varying temperature conditions, leading to inadequate power performance at low temperatures after being used in high-temperature environments.
Innovation Solution
Incorporating a sulfate ester with a specific structure, such as isopropyl ethyl sulfate, diisopropyl sulfate, or di-t-butyl sulfate, and a lithium phosphate compound containing fluorine and oxygen into the non-aqueous electrolyte, with the sulfate ester content limited to 4.0 wt% or less and the lithium phosphate compound content between 0.01 wt% and 3.0 wt% relative to the total weight, to inhibit the increase in internal resistance at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the battery is used in high-temperature circumstances, then the battery can operate in summer conditions, but the internal resistance increases significantly and power performance deteriorates when used at low temperatures afterward
Solution Approach 1:
The patent applies preliminary action by adding specific additives (sulfate ester and lithium phosphate compound) to the non-aqueous electrolyte before the battery undergoes high-temperature operation. These additives pre-form protective films on the electrode surfaces that stabilize the electrolyte and prevent excessive internal resistance increase, ensuring the battery maintains reliable power performance even after high-temperature use and when subsequently operated at low temperatures.
Solution Approach 2:
The patent applies parameter changes by modifying the chemical composition of the non-aqueous electrolyte through the addition of sulfate ester (0.01-5.0 wt%) and lithium phosphate compound (0.01-3.0 wt%). These compositional changes alter the physical and chemical properties of the electrolyte, including its stability, viscosity, and interaction with electrode surfaces, enabling the battery to maintain acceptable performance across wide temperature ranges from -30°C to 60°C.
2Productivity
If repeated charge/discharge cycles are performed, then the battery provides continuous power supply, but the discharge capacity decreases and internal resistance increases
Solution Approach 1:
The patent applies preliminary action by incorporating stabilizing additives (sulfate ester and lithium phosphate compound) into the electrolyte before the battery undergoes repeated charge/discharge cycling. These additives pre-form protective films on the electrode surfaces that prevent degradation reactions, reduce electrolyte decomposition, and maintain ion conductivity, thereby preserving discharge capacity and limiting internal resistance increase even after extensive cycling.
3Duration of action of stationary object
If long-term storage is performed, then the battery can be kept ready for use, but the internal resistance increases and power performance decreases
Solution Approach 1:
The patent applies preliminary action by adding sulfate ester and lithium phosphate compound to the non-aqueous electrolyte before storage. These additives form stable protective films on the electrode surfaces that prevent self-discharge reactions and electrolyte decomposition during long-term storage. The films act as barriers that maintain electrolyte integrity and electrode functionality, ensuring the battery retains acceptable power performance even after extended storage periods.
Solution Approach 2:
The patent employs small amounts of sacrificial additives (sulfate ester and lithium phosphate compound) that are consumed during initial cycles to form protective films. These additives act as disposable components that sacrifice themselves to create a stable interface between the electrolyte and electrodes, preventing long-term degradation without requiring continuous presence in significant quantities.
Data Source
AI summary
A non-aqueous electrolyte secondary battery is described, capable of inhibiting the raise of the internal resistance at a low temperature after use in a high-temperature circumstance, and having a good power performance at a low temperature. The non-aqueous electrolyte secondary battery has a non-aqueous electrolyte, and is characterized in containing a sulfate ester with a specific structure in an amount of 4.0 wt % or less relative to the total weight of the non-aqueous electrolyte.