Lithium Fluorosulfonate Electrolyte for Low-Temperature Battery Performance
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries, such as lithium ion batteries, face poor low-temperature performance due to insufficient discharge capacity when large currents flow, primarily because of uneven ion conductivity and increased electric resistance caused by inadequate lithium fluorosulfonate content and dibutyl phthalate absorption in the positive electrode active material.
Innovation Solution
A nonaqueous electrolyte secondary battery with a positive electrode active material comprising lithium transition metal composite oxide, including nickel, manganese, and cobalt, and a nonaqueous electrolytic solution containing lithium fluorosulfonate, dibutyl phthalate, lithium bis(oxalato)borate, and lithium difluorophosphate, where the dibutyl phthalate absorption is between 28 mL/100 g and 45 mL/100 g, and lithium fluorosulfate content is between 0.15% and 1.0% by mass, to form a uniform coating film with improved ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium fluorosulfonate content is increased to improve ion conductivity, then low-temperature performance improves, but excessive content causes too much coating film formation which decreases electron conductivity and increases electric resistance
Solution Approach 1:
The patent optimizes the content of lithium fluorosulfonate within a specific range (0.15-1.0% by mass) to achieve the desired balance between ion conductivity and electron conductivity. This parameter optimization resolves the contradiction by finding the optimal concentration that provides sufficient coating film for ion conductivity while preventing excessive film formation that would harm electron conductivity.
2Reliability
If dibutyl phthalate absorption amount is increased to improve liquid retention property, then coating film formation improves, but excessive absorption causes particle strength decrease and crack formation
Solution Approach 1:
The patent specifies an optimal range for dibutyl phthalate absorption amount (28-45 mL/100 g) to resolve the contradiction between liquid retention property and particle strength. Within this range, the coating film forms uniformly without causing excessive particle degradation or cracking, maintaining both performance and structural integrity.
3Quantity of substance
If lithium fluorosulfonate content is too low, then coating film formation is insufficient and ion conductivity decreases, but increasing content too much causes excessive coating film that decreases electron conductivity
Solution Approach 1:
The patent establishes an optimal content range for lithium fluorosulfonate (0.15-1.0% by mass) that produces the right quantity of coating film. This parameter control ensures sufficient coating for good ion conductivity while preventing excessive film formation that would increase electric resistance and harm electron conductivity.
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 battery achieves enhanced low-temperature performance by maintaining sufficient ion conductivity and reducing electric resistance, thereby increasing discharge capacity when large currents are drawn at low temperatures.
Implementation Method 1
the formation of a coating film having good ion conductivity (in particular, the conductivity of ions serving as charge carriers) on the surface of the positive electrode active material becomes uneven
Implementation Method 2
A dibutyl phthalate (DBP) absorption amount of the positive electrode active material is 28 mL/100 g or more and 45 mL/100 g or less
Data Source
AI summary
Provided is a nonaqueous electrolyte secondary battery in which lithium fluorosulfonate is added to a nonaqueous electrolytic solution and which demonstrates excellent low-temperature performance. The nonaqueous electrolyte secondary battery disclosed herein includes a positive electrode, a negative electrode, and a nonaqueous electrolytic solution. The positive electrode includes a positive electrode active material layer. The positive electrode active material layer includes, as a positive electrode active material, a lithium transition metal composite oxide including at least lithium, nickel, manganese, and cobalt. The nonaqueous electrolytic solution includes lithium fluorosulfonate. A dibutyl phthalate absorption amount of the positive electrode active material is 28 mL/100 g or more and 45 mL/100 g or less. A content of lithium fluorosulfonate in the nonaqueous electrolytic solution is 0.15% by mass or more and 1.0% by mass or less.