Li-Ion Battery Electrolyte Composition for Heat-Stable High Energy Density
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Solution Overview
Problem
Current lithium-ion secondary batteries face challenges in achieving high energy density while maintaining long cycle and storage life, as they generate excessive heat during charging, leading to electrolyte decomposition and poor performance.
Innovation Solution
A lithium-ion secondary battery design incorporating a positive electrode sheet with a specific carbon content and a highly heat-stable electrolyte solution, where the electrolyte solution contains a lithium salt (My+)x/yR1(SO2N−)xSO2R2, and a low-impedance additive, optimizing the mass percent and temperature rise coefficients to reduce heat impact and improve energy density and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the content of carbon as a conductive agent on an electrode sheet or a carbon coating amount on the surface of positive electrode material particles is reduced to increase the weight of active material per unit volume, then the energy density is improved, but the internal resistance of the battery cell increases significantly
Solution Approach 1:
The patent optimizes the carbon content parameters in the positive electrode material layer, specifically controlling the carbon coating amount on positive electrode material particles and the content of carbon conductive agent within defined ranges (carbon coating amount: 0.1-5 wt% based on positive electrode material; carbon conductive agent content: 0.1-5 wt% based on total positive electrode material layer weight). This parameter optimization balances the competing requirements of maximizing energy density while maintaining acceptable internal resistance levels.
2Quantity of substance
If the coating weight of the active material is increased and the proportion of the inactive substrate is reduced to improve energy density, then the discharge gram capacity of active material per unit volume is improved, but the internal resistance increases and heat generation during charging worsens
Solution Approach 1:
The patent defines specific parameter ranges for active material coating weight and inactive substrate proportion to optimize the balance between energy density and heat generation. By controlling these parameters within defined ranges, the patent achieves high discharge gram capacity while managing the internal resistance and heat generation that would otherwise worsen with increased active material loading.
3Quantity of substance
If the internal resistance of the battery cell is high due to optimized energy density, then the energy density is improved, but the battery cell releases heat seriously during high rate charging leading to electrolyte decomposition
Solution Approach 1:
The patent introduces a specific electrolyte composition as an intermediary substance to mediate between the high internal resistance condition and the harmful electrolyte decomposition. The electrolyte contains lithium salt (My+)x/yR1(SO2N−)xSO2R2 with specific structural features (where My+ is metal ion, R1 and R2 are fluorine atoms, alkyl, fluoroalkyl, or fluoroalkoxy groups with 1-20 carbon atoms) that provide thermal stability and suppress decomposition reactions during high-rate charging.
Solution Approach 2:
The patent optimizes the mass percent of lithium salt in the electrolyte solution (denoted as k2%) and establishes a specific relationship between this parameter and the temperature rise coefficient k1 of the positive electrode sheet (0.34 ≤ k2/k1 ≤ 8). This parameter coordination ensures that the electrolyte maintains sufficient ionic conductivity while providing thermal stability to prevent decomposition under high-temperature conditions generated during high-rate charging.
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 effectively reduces heat-induced decomposition, enhances energy density, and extends the cycle life of the battery by maintaining thermal stability and conductivity, thereby improving both charging and discharging performance.
Implementation Method 1
the electrolyte solution comprises a lithium salt (My+)x/yR1(SO2N−)xSO2R2... a mass percent of the lithium salt in the electrolyte solution is set as k2%
Implementation Method 2
a temperature rise coefficient k1 of the positive electrode sheet satisfies 2.5≤k1≤32, where k1=Cw/Mc... When charging at a high rate, the battery cell releases heat seriously
Implementation Method 3
When charging at a high rate, the battery cell releases heat seriously and are thus under high temperature conditions. In this case, decomposition of lithium salts, such as LiPF6, in the electrolyte solution will be accelerated to generate gases such as HF and PF5
Implementation Method 4
These highly reactive ingredients will accelerate the damage of a SEI film, resulting in the exposure of the active material to the electrolyte solution
Data Source
AI summary
A lithium-ion secondary battery is provided, where an electrolyte solution of the lithium-ion secondary battery comprises a highly heat-stable salt (My+)x/yR1(SO2N−)xSO2R2, where the My+ is a metal ion, R1 and R2 are each independently a fluorine atom, an alkyl with 1-20 carbon atoms, a fluoroalkyl with 1-20 carbon atoms, or a fluoroalkoxy with 1-20 carton atoms, x is 1, 2, or 3, and y is 1, 2, or 3. A mass percent of the salt in the electrolyte solution is set as k2%; a temperature rise coefficient k1 of the positive electrode sheet satisfies 2.5≤k1≤32, where k1=Cw/Mc, Cw is a positive electrode material load per unit area (mg/cm2) on the surface of any side of the positive electrode current collector on which a positive electrode material layer is loaded, and Mc is a carbon content (%) of the positive electrode material layer; and the lithium-ion secondary battery satisfies 0.34≤k2/k1≤8.