Secondary Battery Electrolyte Additives for High Density Negative Electrodes
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Solution Overview
Problem
Lithium-ion batteries with high negative electrode density face challenges in balancing high-temperature characteristics and low-temperature charging capabilities, with increased active material load leading to deteriorated power characteristics and lithium plating issues.
Innovation Solution
A secondary battery design incorporating a fluorinated compound, polynitrile, and sulfate additives in the electrolyte, along with a negative electrode compaction density of at least 1.55 g/cm3, to enhance oxidation resistance and lithium ion migration, thereby improving high-temperature and low-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the compaction density of the negative electrode is increased to achieve higher volumetric energy density, then the battery capacity increases, but the charging ability deteriorates and lithium plating occurs
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing a specific fluorinated compound (Formula 1) with fluorine atoms at the 3-position of the cyclic carbonate ring. This parameter change in electrolyte composition enables the formation of a stable protective film on the negative electrode surface, allowing the battery to maintain good charging ability even at high negative electrode compaction densities (≥1.55 g/cm³) where conventional electrolytes would cause lithium plating and capacity deterioration.
2Quantity of substance
If the active material load of the negative electrode is increased to achieve higher capacity, then the volumetric energy density improves, but the power characteristics deteriorate
Solution Approach 1:
The patent modifies the electrolyte composition by incorporating the fluorinated cyclic carbonate compound (Formula 1) at a specific concentration range (5-50 wt% of total cyclic carbonate). This parameter change in electrolyte chemistry enables the system to maintain low internal resistance and high ionic conductivity even when the negative electrode contains high loads of active material (compaction density ≥1.55 g/cm³), thereby preserving power characteristics while achieving high capacity.
3Temperature
If film-forming additives are increased to improve high-temperature characteristics, then thermal stability improves, but charging capability decreases especially at low temperature
Solution Approach 1:
The patent introduces a specific fluorinated compound (Formula 1) with unique molecular structure containing fluorine atoms at the 3-position of the cyclic carbonate ring. This structural parameter change creates a protective film with different properties than conventional additives - the film provides thermal stability at high temperatures while maintaining sufficient ionic conductivity and charge transfer kinetics at low temperatures, thus avoiding the charging capability deterioration that occurs with conventional film-forming additives.
4Quantity of substance
If the charge cut-off voltage is set to 4.4 V or higher to obtain higher battery capacity, then energy density improves, but electrolyte oxidative decomposition increases and transition metal ions dissolve
Solution Approach 1:
The fluorinated cyclic carbonate compound (Formula 1) acts as an intermediary protective layer between the positive electrode and the bulk electrolyte. When the battery operates at high voltages (≥4.4 V), this compound forms a stable surface film on the positive electrode that prevents direct contact between the electrolyte and the high-voltage electrode material, thereby suppressing oxidative decomposition of the electrolyte and preventing dissolution of transition metal ions while still allowing lithium ion transport.
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 optimized electrolyte composition and electrode design improve high-temperature characteristics and low-temperature charging ability, reducing internal resistance and preventing lithium plating, thus maintaining battery performance across varying conditions.
Implementation Method 1
a fluorinated compound that accounts for 5 to 20% of the total mass of the electrolyte
Implementation Method 2
the lithium-ion secondary batteries that energy conversion by the intercalation and deintercalation of lithium ions
Implementation Method 3
the electrolyte is prone to oxidative decomposition on the positive electrode side; at the same time, transition metal ions will dissolve out
Implementation Method 4
transition metal ions will dissolve out, reduce and deposit on the negative electrode side
Implementation Method 5
After the battery is fully charged, if there is white attachment on the negative electrode interface, it is called 'lithium plating'
Data Source
AI summary
Disclosed is a secondary battery, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte comprises a lithium salt, an organic solvent, and an additive, wherein the additive comprises a fluorinated compound that accounts for 5-20% of the total mass of the electrolyte, and a polynitrile compound that accounts for 0.2-4% of the total mass of the electrolyte and a sulfate compound that accounts for 0.3-5% of the total mass of the electrolyte; and the negative electrode has a compacted density of not less than 1.55 g/cm3. When the secondary battery is used, the battery can still have both a high temperature characteristic and a low temperature charging ability under the conditions of a higher negative electrode density, thereby having market application prospects, and overcoming the problem of the performance of existing secondary batteries deteriorating when the compacted density of a negative electrode is improved.