Non-aqueous Electrolyte for High-Loading Lithium Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-loading lithium secondary batteries face challenges in achieving excellent high-rate charging/discharging characteristics and low-temperature discharging characteristics while maintaining a long life cycle, due to issues with the stability of the Solid Electrolyte Interface (SEI) film and the reactivity of certain solvents, which lead to increased inner pressure and poor conductivity at low temperatures.
Innovation Solution
A lithium secondary battery with a non-aqueous electrolyte comprising a mixed organic solvent blend of cyclic carbonates and propionate-based ester compounds, specifically ethylene carbonate, propylene carbonate, and ethyl propionate, optimized in a volume ratio to enhance ionic conductivity and reduce reactivity, ensuring a capacity density of 3.5 to 5.5 mAh/cm² and porosity of 18 to 35%, thereby improving high-rate discharging and low-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large amount of ethylene carbonate is used in the electrolyte, then the SEI film formation is enhanced, but the inner pressure of the battery increases and low-temperature conductivity deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing propionate-based ester compounds with specific molecular structures (containing carbonyl and ester groups) to modify the SEI film properties. This substitution reduces the freezing point and enhances low-temperature ionic conductivity while maintaining SEI stability.
Solution Approach 2:
The patent creates a composite electrolyte system by combining cyclic carbonate, chain carbonate, and propionate-based ester compounds. This composite approach leverages the complementary properties of each component: cyclic carbonate for SEI formation, chain carbonate for low viscosity, and propionate ester for low-temperature performance.
2Reliability
If the battery is left at high temperature in a fully charged state, then the SEI film breaks down due to increased electrochemical and thermal energy, but this leads to continuous side reactions and increased inner pressure
Solution Approach 1:
The propionate-based ester compounds act as intermediary substances that mediate between the electrolyte and the anode surface. These compounds form a more stable SEI film that prevents direct contact between the electrolyte and anode, thereby preventing continuous side reactions and gas generation at high temperatures.
Solution Approach 2:
The patent converts the potential harm of SEI film breakdown at high temperatures into a benefit by using propionate-based esters that form a more thermally stable SEI film. The initial SEI formation process using these compounds creates a protective layer that prevents further decomposition and gas generation.
3Quantity of substance
If the cathode capacity density is increased to achieve high energy concentration, then the energy storage is improved, but the high-rate charging/discharging characteristics and life cycle are compromised
Solution Approach 1:
The patent optimizes the electrolyte composition parameters by adjusting the ratios of cyclic carbonate, chain carbonate, and propionate-based ester compounds. This parameter optimization enhances ionic conductivity and reduces viscosity, enabling fast ion transport even at high cathode capacity densities, thereby maintaining high-rate charging/discharging performance.
4Reliability
If a mixed solvent of cyclic carbonate and linear carbonate is used, then the electrochemical stability is achieved, but the reactivity with anode increases and gas generation occurs
Solution Approach 1:
The propionate-based ester compounds serve as intermediary substances that reduce the direct reactivity between the carbonate-based electrolyte and the carbon anode. These intermediates form a stable SEI film that prevents further decomposition reactions, thereby reducing CO and CO2 gas generation while maintaining electrochemical stability.
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 provides a lithium secondary battery with enhanced high-rate charging/discharging characteristics and improved low-temperature discharging performance, along with extended life cycle and reduced gas generation, addressing the limitations of previous battery compositions.
Implementation Method 1
a non-aqueous electrolyte obtained by dissolving a suitable amount of lithium salt in a mixed organic solvent
Implementation Method 2
The SEI film plays the role of an ion tunnel, which allows only lithium ions to pass
Implementation Method 3
Lithium ions coming out from the cathode active material such as lithium metal oxide during an initial charging process of a lithium secondary battery move towards the anode active material such as graphite and then are intercalated between layers of the anode active material
Implementation Method 4
the electrolyte reacts with carbon of the anode active material on the surface of the anode active material such as graphite, thereby generating compounds such as Li2CO3, Li2O and LiOH
Data Source
AI summary
A lithium secondary battery has an anode, a cathode, a separator between the anode and the cathode and a non-aqueous electrolyte. The non-aqueous electrolyte includes a lithium salt; and a non-linear carbonate-based mixed organic solvent in which (a) a cyclic carbonate compound, and (b) a propionate-based compound are mixed at a volume ratio (a:b) in the range from about 10:90 to about 70:30. The cathode has a current density in the range from about 3.5 to about 5.5 mAh/ cm2 and a porosity in the range from about 18 to about 35%. This battery may be manufactured as a high-loading lithium secondary battery.