Improving Low-Temperature Performance in Nonaqueous Batteries
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Summary
Problems
Nonaqueous electrolyte secondary batteries with tungsten and lithium fluorosulfonate additives face low-temperature performance issues due to nonuniform coating films and increased resistance, particularly when the concentration of LiPF6 is less than 1.11 mol/L or viscosity is less than 3.1 cP, and porosity ratios exceed or fall below specific ranges.
Innovation solutions
A nonaqueous electrolyte secondary battery design with a positive electrode active material layer containing lithium transition metal composite oxides, including tungsten, and a nonaqueous electrolytic solution with LiPF6 concentration of 1.11 mol/L or more and viscosity of 3.1 cP or more, along with a separator structure that maintains porosity ratios between 0.6 and 0.9 for both inorganic and resin layers, ensuring uniform ion conductivity and fluidity.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If the concentration of LiPF6 is less than 1.11 mol/L or the viscosity of the nonaqueous electrolytic solution is less than 3.1 cP, then the electrolytic solution decomposes nonuniformly, but a coating film is formed nonuniformly on the electrode surface, deteriorating low-temperature performance
Why choose this principle:
The patent optimizes the concentration of LiPF6 to be 1.11 mol/L or more and the viscosity of the nonaqueous electrolytic solution to be 3.1 cP or more. These parameter changes ensure uniform decomposition of the electrolytic solution and formation of a uniform coating film on the electrode surface, thereby improving low-temperature performance.
Principle concept:
If the porosity ratio β/α exceeds 0.9, then the separator structure is highly porous, but the nonaqueous electrolytic solution amount and fluidity on the positive electrode surface are insufficient, causing nonuniform coating film formation
Why choose this principle:
The patent specifies that the porosity ratio β/α should be 0.9 or less. This parameter control ensures that the separator structure retains sufficient nonaqueous electrolytic solution and maintains adequate fluidity on the positive electrode surface, enabling uniform coating film formation and improving low-temperature performance.
Application Domain
Data Source
AI summary:
A nonaqueous electrolyte secondary battery design with a positive electrode active material layer containing lithium transition metal composite oxides, including tungsten, and a nonaqueous electrolytic solution with LiPF6 concentration of 1.11 mol/L or more and viscosity of 3.1 cP or more, along with a separator structure that maintains porosity ratios between 0.6 and 0.9 for both inorganic and resin layers, ensuring uniform ion conductivity and fluidity.
Abstract
Provided is a nonaqueous electrolyte secondary battery with excellent low-temperature performance. The nonaqueous electrolyte secondary battery disclosed herein includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the 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, cobalt, and tungsten. The nonaqueous electrolytic solution includes lithium fluorosulfonate and LiPF 6 . The concentration of LiPF 6 in the nonaqueous electrolytic solution is 1.11 mol/L or more. The viscosity of the nonaqueous electrolytic solution at 25° C. is 3.1 cP or more. The separator includes a resin layer and an inorganic layer formed on a surface of the resin layer that faces the positive electrode. Where a porosity of the inorganic layer is denoted by α, a porosity of the resin layer is denoted by β, and a porosity of the positive electrode active material layer is denoted by γ, relationships of 0.6≤(β/α)≤0.9 and 0.6≤(γ/α)≤0.9 are fulfilled.