Electrolyte and Lithium-ion Battery
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Solution Overview
Problem
Lithium iron manganese phosphate batteries suffer from poor high-temperature storage performance and cycling performance due to manganese dissolution, leading to capacity fading and irreversible capacity loss, which is not effectively addressed by existing electrolytes.
Innovation Solution
Incorporating a fluorosultones compound as an additive in the electrolyte to form a protective film on the cathode and negative electrodes, along with lithium bis(oxalate) borate to suppress manganese dissolution and enhance the electrolyte's wettability and internal resistance, and using a specific combination of organic solvents and lithium salts to improve the battery's electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium iron manganese phosphate is used as cathode material to improve energy density and low-temperature performance, then the energy density and low-temperature performance are improved, but manganese dissolution occurs leading to capacity fading and poor high-temperature cycling performance
Solution Approach 1:
The patent introduces an electrolyte as an intermediary medium between the lithium iron manganese phosphate cathode and graphite anode. This electrolyte contains specific additives that form protective films on the electrode surfaces, mediating the interaction between electrodes and preventing direct harmful effects like manganese dissolution while maintaining ion transport functionality.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by incorporating specific additives (vinylene carbonate at 0.5-2.0%, fluoroethylene carbonate at 0.5-2.0%, and lithium bis(oxalate)borate at 0.1-1.0%). These parameter changes in electrolyte composition lead to improved interfacial properties and suppressed manganese dissolution, resolving the high-temperature performance issue while maintaining the energy density benefits of lithium iron manganese phosphate.
2Power
If manganese is reduced to trivalent state during deep discharge or high power operation, then the material structure is distorted and service life is affected, but high power operation is required for battery performance
Solution Approach 1:
The patent applies preliminary action by having the electrolyte additives form protective films on the electrode surfaces before harmful reactions can occur. These pre-formed films prevent manganese reduction and structural distortion during subsequent high-power operations, allowing the battery to deliver high power without compromising service life.
Solution Approach 2:
The patent converts the potentially harmful high-power operation conditions into beneficial effects. The electrolyte composition is designed to stabilize the electrodes specifically under high-power stress conditions, transforming the harsh operational environment into a condition that activates the protective mechanisms, thereby extending service life while maintaining high power output capability.
3Quantity of substance
If Mn2+ dissolves to the electrolyte to cause irreversible capacity loss, then capacity fading occurs, but Mn2+ dissolution is an inherent issue of lithium iron manganese phosphate
Solution Approach 1:
The electrolyte acts as a mediator between the lithium iron manganese phosphate cathode and the aqueous environment. The specific electrolyte composition with film-forming additives creates a barrier that prevents Mn2+ from dissolving into the bulk electrolyte, thereby eliminating the harmful dissolution effect while maintaining the beneficial ionic conductivity for capacity delivery.
Solution Approach 2:
The patent employs the flexible shells and thin films principle by forming thin protective films on the cathode surface through electrolyte additives. These films are flexible enough to accommodate volume changes during cycling while providing effective barrier properties against manganese dissolution, thus preserving capacity without restricting electrochemical activity.
4Reliability
If Mn2+ is reduced and deposited in the negative electrode destroying SEI film, then capacity fading occurs, but negative electrode protection is needed
Solution Approach 1:
The electrolyte serves as an intermediary that controls the interaction between Mn2+ and the negative electrode. By adjusting electrolyte composition with specific additives, the system prevents Mn2+ from reaching and destroying the SEI film on the negative electrode, thereby maintaining negative electrode stability and preventing capacity fading.
Solution Approach 2:
The electrolyte composition is designed to enable self-protection of the negative electrode. The film-forming additives in the electrolyte automatically form protective layers on the negative electrode surface during initial cycles, creating a self-healing mechanism that continuously protects the SEI film from Mn2+ attack throughout battery operation.
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 significantly improves high-temperature storage and cycling performance, maintaining capacity and reducing thickness growth, with a capacity maintaining rate of 85% after 30 days at 60°C and 88% after 1000 cycles at 45°C, while minimizing manganese dissolution.
Implementation Method 1
The fluorosultones compound as shown in Formula 1 in the present application is used as an additive in lithium iron manganese phosphate batteries to participate in the film formation of the positive electrode
Implementation Method 2
the structure of the fluorocarbon chain in the fluorosultones compound as shown in Formula 1 may improve the wettability of the electrolyte to a certain degree, and reduce the internal resistance of the battery
Data Source
AI summary
Provided in the present application is an electrolyte and lithium-ion battery, the electrolyte including a fluorosultones compound as shown in Formula 1. The electrolyte prepared in the present application is applied to lithium iron manganese phosphate batteries, which effectively suppresses the dissolution of manganese in lithium iron manganese phosphate materials, and significantly improves the high-temperature storage performance and high-temperature cycling performance of the batteries.