Silane Coupling Agent Positive Electrode Film for Battery Safety
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Solution Overview
Problem
Nonaqueous secondary batteries using fluorinated cyclic carbonate esters as electrolytes suffer from decreased nail penetration characteristics, leading to potential thermal runaway due to oxidative decomposition on the positive electrode surface, while existing solutions to improve cycle characteristics do not address nail penetration safety effectively.
Innovation Solution
Incorporating a predetermined amount of a silane or aluminum coupling agent and maintaining the average particle diameter and specific surface area of the positive electrode active material within specific ranges, along with using fluorinated cyclic carbonate esters in the nonaqueous electrolyte, to form a stable surface film and enhance thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If fluorinated cyclic carbonate esters are used as nonaqueous electrolyte, then cycle characteristics are improved, but nail penetration characteristics deteriorate
Solution Approach 1:
A silane coupling agent is introduced as an intermediary substance that forms a protective surface film on the positive electrode. This film acts as a mediator between the fluorinated cyclic carbonate ester electrolyte and the electrode, preventing direct oxidative decomposition while allowing ion transport, thus improving nail penetration characteristics without sacrificing cycle characteristics.
Solution Approach 2:
The patent uses a composite approach by combining fluorinated cyclic carbonate ester with silane coupling agent to create a dual-function system. The electrolyte provides electrochemical stability for cycling, while the silane-derived surface film provides thermal stability for safety, achieving both improved cycle characteristics and nail penetration characteristics.
2Duration of action of stationary object
If coupling agent is added to positive electrode mixture, then cycle characteristics are improved, but nail penetration characteristics may deteriorate
Solution Approach 1:
The patent optimizes the concentration of silane coupling agent within a specific range (0.01-5% by mass relative to positive electrode active material). This parameter optimization ensures sufficient surface film formation for cycle stability while preventing excessive film formation that could compromise thermal safety and nail penetration characteristics.
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
This approach improves both nail penetration characteristics and cycle characteristics by preventing electrolyte decomposition and maintaining thermal stability, ensuring safer battery performance.
Implementation Method 1
form a stable surface film
Implementation Method 2
the positive electrode mixture layer contains at least one of a silane coupling agent and a coupling agent
Implementation Method 3
decomposition of the nonaqueous electrolyte is suppressed and the nonaqueous electrolyte is electrochemically stabilized
Implementation Method 4
preventing electrolyte decomposition
Data Source
AI summary
A positive electrode active material has an average particle diameter of 4.5 to 15.5 μm and a specific surface area of 0.13 to 0.80 m2/g. A positive electrode mixture layer contains a silane coupling agent and/or at least one of aluminum, titanium, or zirconium based coupling agent having an alkyl or alkoxy groups having 1 to 18 carbon atoms at a content of 0.003% by mass or more and 5% by mass or less with respect to the mass of the positive electrode active material. The nonaqueous electrolyte contains a fluorinated cyclic carbonate esters at a content of 0.3% by mass or more with respect to the total mass of the nonaqueous electrolyte. Thus the nonaqueous secondary battery in which, when used with a nonaqueous electrolyte containing a fluorinated cyclic carbonate esters, cycle characteristics are good and nail penetration characteristics are superior is provided.