Silicon Oxide Negative Electrode Oxygen Capture for Battery Safety
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Solution Overview
Problem
Lithium ion secondary batteries face excessive temperature rise due to oxygen release during overcharging, which affects their reliability and capacity, as existing solutions either fail to stabilize internal pressure or insufficiently reduce oxygen partial pressure.
Innovation Solution
A lithium ion secondary battery design featuring a positive electrode with a composite metal oxide and a negative electrode containing silicon and silicon oxide, where the negative electrode active material is treated with hydrofluoric acid to adjust hydrogenation and covered with amorphous carbon, effectively suppressing oxygen generation and oxidation reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a layered oxide containing lithium is used as positive electrode material to increase power storage amount, then capacity increases, but oxygen is easily released during overcharging causing excessive temperature rise
Solution Approach 1:
Silicon oxide is introduced as an intermediary substance that mediates between the oxygen released from the layered oxide positive electrode and the harmful oxidation reactions. The silicon oxide captures the oxygen to form silicon oxyfluoride, preventing the oxygen from causing excessive temperature rise while allowing the high-capacity layered oxide to function.
Solution Approach 2:
The oxygen release, which is normally a harmful side reaction causing temperature rise, is converted into a beneficial process by having it react with silicon oxide to form silicon oxyfluoride. This transforms the harmful oxygen evolution into a useful oxygen-capture mechanism that protects the battery from thermal runaway.
2Temperature
If lithium carbonate is introduced inside the battery to reduce oxygen partial pressure through reaction with silicon oxide, then temperature rise is suppressed, but internal pressure increases due to CO2 generation
Solution Approach 1:
The chemical composition and structure of the negative electrode active material are changed by controlling the silicon oxide content and hydrogenation level. By adjusting these parameters, the material can capture oxygen without generating excessive CO2, thus suppressing temperature rise while maintaining stable internal pressure.
Solution Approach 2:
A composite negative electrode active material is created by combining silicon, silicon oxide, and carbon in specific proportions. This composite structure provides multiple functions: silicon provides capacity, silicon oxide captures oxygen, and carbon provides conductivity and structural stability, achieving both temperature suppression and pressure stability.
3Object-affected harmful factors
If the negative electrode active material is hydrogenated to enhance oxygen capture capability, then oxygen release is suppressed, but discharge capacity decreases
Solution Approach 1:
Hydrogenation is applied locally and selectively to specific sites on the silicon oxide surface rather than uniformly throughout the entire material. This localized hydrogenation creates specific functional groups that are highly effective at capturing oxygen while preserving the overall discharge capacity of the negative electrode material.
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 high capacity and suppresses temperature rise during overcharging by reducing oxygen levels and enhancing discharge capacity while maintaining stable battery conditions.
Implementation Method 1
oxygen is easily released from a positive electrode active material due to temperature rise when the deintercalation of Li out of the active material is caused by overcharging. This accelerates the oxidation reaction
Implementation Method 2
the negative electrode active material is treated with hydrofluoric acid to adjust hydrogenation
Implementation Method 3
when the battery is short-circuited, endothermic reaction occurs in which carbon dioxide is released, so that the battery is cooled
Data Source
AI summary
A lithium ion secondary battery includes a positive electrode including a positive electrode active material having a composition represented by the formula (1)LixNiyCozMtO2 (1)(wherein the element M is at least one kind selected from the group consisting of Mg, Ba, Al, Ti, Mn, V, Fe, Zr, and Mo and x, y, z, and t satisfy the following formulae: 0.9≦x≦1.2, 0≦y≦1.1, 0≦z≦1.1, and 0≦t≦1.1), and a negative electrode including a negative electrode active material mainly containing silicon and silicon oxide, and having an absorbance of 0.01 to 0.035 at 2110±10 cm−1 according to an FT-IR method.