Si Negative Electrode Battery with Controlled Acid Electrolyte
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Solution Overview
Problem
Lithium-ion batteries with graphite negative electrodes face limitations in capacity increase, and silicon-based batteries suffer from deterioration when stored at high temperatures, especially in a discharged state, due to Si dissolution and film formation reactions.
Innovation Solution
A non-aqueous electrolyte secondary battery design incorporating a Si-based negative electrode with a potential of 0.6 to 1.5 V relative to a Li electrode, using lithium hexafluorophosphate as the main electrolyte and controlling acid content between 50-200 ppm to suppress Si dissolution and precipitation, along with a Si alloy or compound with specific impurities and a thin film structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode material is used to achieve high capacity, then battery capacity increases significantly, but storage characteristics deteriorate at high temperatures due to Si dissolution and film formation reactions
Solution Approach 1:
The patent applies parameter changes by controlling the acid content of the non-aqueous electrolyte within a specific range (50-200 ppm) to suppress Si dissolution and film formation reactions during storage, while maintaining high capacity utilization during charge/discharge cycles. This parameter optimization resolves the contradiction between high capacity and storage stability.
Solution Approach 2:
The patent uses composite materials by combining Si-based negative electrode material with specific electrolyte compositions (lithium hexafluorophosphate as main supporting electrolyte) and controlling impurity levels. This composite approach enables both high capacity utilization and improved storage characteristics by suppressing harmful side reactions.
2Reliability
If discharge potential is limited to minimize capacity loss during cycles, then storage characteristics improve, but only about half of the inherent capacity of SiO is utilized
Solution Approach 1:
The patent changes the parameter of acid content in the electrolyte to enable full capacity utilization of Si-based materials without requiring discharge potential limitations. By controlling acid content at 50-200 ppm, the patent suppresses film formation reactions that previously necessitated discharge potential restrictions, thereby achieving both high capacity utilization and storage stability.
Solution Approach 2:
The patent introduces the electrolyte with controlled acid content as an intermediary that mediates between the Si-based negative electrode and the environment. This intermediary role of the electrolyte suppresses harmful side reactions during storage while allowing full capacity utilization during operation, eliminating the need for discharge potential limitations.
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 design allows for the full utilization of the high capacity of Si-based negative electrodes while maintaining excellent storage and charge/discharge characteristics by controlling the dissolution and film formation reactions, enhancing battery stability and performance.
Implementation Method 1
the non-aqueous electrolyte has an acid content of not less than 50 ppm and not more than 200 ppm
Implementation Method 2
a negative electrode including a negative electrode active material that comprises at least Si... capable of electrochemically absorbing and desorbing lithium ions
Data Source
AI summary
A non-aqueous electrolyte secondary battery including: a positive electrode; a negative electrode, and a non-aqueous electrolyte. The negative electrode includes a negative electrode active material that includes at least Si. The non-aqueous electrolyte includes lithium hexafluorophosphate as a main supporting electrolyte and has an acid content of not less than 50 ppm and not more than 200 ppm. The negative electrode has a potential of not less than 0.6 V and not more than 1.5 V relative to a Li electrode at an end-of-discharge voltage of the battery. The battery is prevented from suffering degradation of storage characteristics caused by the dissolution reaction of Si from the negative electrode during charging and the precipitation reaction of the dissolved Si.