Aromatic Phosphate Electrolyte for Lithium Ion Battery Safety
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Solution Overview
Problem
Lithium ion secondary batteries face issues with overcharge safety, high-temperature safety, and cycle life due to thermal instability and gas release, which can lead to thermal runaway and battery damage.
Innovation Solution
An electrolyte comprising a non-aqueous organic solvent, a lithium salt, and at least one aromatic phosphate compound, which forms a polyphosphate that acts as a barrier against heat and oxygen, inhibiting exothermic reactions and reducing gas release, thereby enhancing safety and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redox shuttle additives (aromatic compounds) are used to interrupt overcharge current and prevent thermal runaway, then overcharge safety is improved, but large amounts of gases are released from decomposition of the additives, causing severe swelling of the batteries
Solution Approach 1:
The patent combines aromatic phosphate compound (I) with specific functional groups (ether, ester, or amide) to create a composite additive system. This composite structure allows the additive to perform multiple functions: the aromatic ring provides redox shuttle activity for overcharge protection, while the specific functional groups control decomposition behavior to minimize gas release. The synergistic effect of these combined structural elements resolves the contradiction between overcharge safety and gas generation.
Solution Approach 2:
The patent specifies precise parameter ranges for the aromatic phosphate compound structure: n values from 1-10, specific alkyl group configurations (C1-C5), and controlled amounts (0.01-5 wt%). By optimizing these structural parameters, the additive achieves effective overcharge protection while its decomposition produces minimal gas. The parameter optimization balances the redox activity needed for safety with the stability needed to reduce gas release.
2Reliability
If aromatic additives are incorporated into electrolyte to improve battery safety, then overcharge protection is enhanced, but the additives are electrochemically polymerized at abnormally high voltages to increase internal resistance, and heat generated by exothermic oxidation reactions increases internal temperatures
Solution Approach 1:
The patent introduces localized functional groups (ether, ester, or amide) at specific positions on the aromatic phosphate molecule. These local functional modifications create sites that preferentially undergo polymerization or react with radicals at the electrode interfaces rather than undergoing bulk exothermic oxidation. This localized reactivity control allows the additive to protect against overcharge while minimizing heat generation in the bulk electrolyte.
Solution Approach 2:
The aromatic phosphate compound acts as an intermediary substance that mediates between the overcharge current and the electrode materials. It undergoes controlled electrochemical reactions that consume excess charge while the specific functional groups facilitate heat dissipation or prevent runaway exothermic reactions. The intermediary structure provides a controlled reaction pathway that protects the battery without causing excessive temperature rise.
3Reliability
If SEI film is formed on graphite negative electrode during initial charge to prevent side reactions, then charge/discharge characteristics are maintained, but the SEI film slowly collapses during high-temperature exposure, exposing the negative electrode surface to continuous reaction with electrolyte and gas release
Solution Approach 1:
The aromatic phosphate compound performs preliminary protective action by forming a stable surface layer or modifying the SEI film structure during initial cycles. This preliminary modification creates a more thermally stable interface that prevents SEI collapse at high temperatures. The additive prepares the electrode surface in advance to resist thermal degradation, maintaining both charge/discharge performance and structural stability under elevated temperature conditions.
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 electrolyte improves overcharge safety, high-temperature safety, and cycle life by preventing thermal runaway and reducing swelling, ensuring the battery remains safe and functional under extreme conditions.
Implementation Method 1
The additives are electrochemically polymerized at abnormally high voltages to increase the internal resistance of the battery
Implementation Method 2
The additives are electrochemically polymerized at abnormally high voltages to increase the internal resistance of the battery. These redox shuttle additives increase the internal temperatures of batteries at the early stages due to heat generated by exothermic oxidation reactions
Implementation Method 3
This thermal instability may induce rapid exothermic thermal decomposition reactions between the electrodes and the electrolyte
Data Source
AI summary
An electrolyte for a lithium ion secondary battery and a lithium ion secondary battery comprising the electrolyte. The electrolyte comprises a non-aqueous organic solvent, a lithium salt, and at least one aromatic phosphate compound. Exothermic reactions are inhibited in the battery upon overcharge or during high-temperature storage to prevent an increase in the temperature of the battery, resulting in an improvement in safety. In addition, the battery exhibits good swelling stability during high-temperature storage as well as improved cycle life characteristics. The electrolyte further comprises an ethylene carbonate-based compound. The presence of the ethylene carbonate-based compound leads to further improvements in the overcharge safety, high-temperature safety and cycle life characteristics of the battery.