Nonaqueous Battery Heat Dissipation via Surface Area and Electrolyte
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face issues with heat generation and reduced output characteristics in abnormal conditions and low temperature environments, respectively, due to the reaction between the negative electrode and the electrolyte, which affects their safety and performance.
Innovation Solution
Incorporating a lithium salt with an oxalate complex and lithium difluorophosphate (LiPF2O2) in the electrolyte, combined with a larger outer surface area of the battery casing and specific electrode designs, such as elongated electrodes and collectors with ribs, to facilitate heat dissipation and prevent excessive temperature buildup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lithium salt having an oxalate complex as an anion is added to the nonaqueous electrolyte to form a protective layer on the negative electrode, then cycling characteristics and safety are improved, but heat generation increases in abnormal conditions
Solution Approach 1:
The patent introduces a new parameter - the outer surface area of the battery outer body (setting it to 350 cm² or more) - to resolve the contradiction. By changing the geometric parameter of the battery housing, heat dissipation capability is enhanced, which counteracts the increased heat generation from the protective layer formed by LiBOB addition, thereby maintaining reliability while reducing harmful heat accumulation
Solution Approach 2:
The patent converts the harmful heat generation effect into a beneficial outcome by designing the battery outer body with sufficient surface area (350 cm² or more) to facilitate heat dissipation. The heat generated by the protective layer reaction is now effectively managed and dissipated, transforming a harmful thermal effect into an acceptable operational characteristic
2Reliability
If LiPF2O2 is added to the nonaqueous electrolyte to form a protective covering on electrode interfaces, then charge storage characteristics are improved, but heat generation increases when temperature rises
Solution Approach 1:
The patent applies the same parameter change strategy - increasing the outer surface area of the battery outer body to 350 cm² or more - to manage heat generation from LiPF2O2. This geometric modification enables effective heat dissipation that counterbalances the thermal effects of the protective covering formation, preserving charge storage characteristics while controlling harmful heat accumulation
3Power
If the battery size is increased to achieve high capacity and high output characteristics, then power supply capability is improved, but heat dissipation becomes more difficult
Solution Approach 1:
The patent directly addresses this contradiction by specifying a minimum outer surface area of 350 cm² for the battery outer body. This parameter setting ensures that even as battery size increases to provide high capacity and output, sufficient surface area is maintained for effective heat dissipation, balancing power capability with thermal management
Solution Approach 2:
The patent shifts the focus from internal battery dimensions to external surface area characteristics. By emphasizing the outer surface area parameter (350 cm² or more), the design optimizes heat dissipation in the external dimension while maintaining internal capacity for high power output, effectively resolving the contradiction through dimensional consideration
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 generation and maintains high output characteristics even in low temperature environments, enhancing the battery's safety, cycling performance, and reliability by promoting efficient heat release and preventing electrolyte decomposition.
Implementation Method 1
When LiBOB disclosed in JP-T-2010-531856 and JP-A-2010-108624 is added to a nonaqueous electrolyte, a protective layer including a lithium ion conductive layer that is thin and extremely stable is formed on the surface of a carbon negative electrode active material
Implementation Method 2
the outer surface area of a battery outer body including the hollow outer can and the sealing plate is 350 cm2 or more
Implementation Method 3
When a battery is in an abnormal condition due to being crushed, for example, and the temperature thereof increased
Data Source
AI summary
A nonaqueous electrolyte secondary battery according to an embodiment of the invention includes: a flat electrode assembly including a positive electrode and a negative electrode; a bottomed prismatic hollow outer can storing the flat electrode assembly and a nonaqueous electrolyte and having an opening portion; and a sealing plate sealing the opening portion of the hollow outer can. The nonaqueous electrolyte contains at least one of a lithium salt having an oxalate complex as an anion and lithium difluorophosphate (LiPF2O2). The outer surface area of a battery outer body including the hollow outer can and the sealing plate is 350 cm2 or more. With this configuration, the nonaqueous electrolyte secondary battery has excellent battery characteristics.