Lithium Iron Oxide Pre-Doping Agent for Low-Voltage Battery Doping
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Solution Overview
Problem
Existing pre-doping methods for power storage devices, such as lithium ion batteries and capacitors, face challenges including high production costs, reduced volume energy density, and the risk of electrolytic solution decomposition due to the use of metal lithium foils and high charging voltages.
Innovation Solution
A pre-doping agent comprising a lithium iron oxide with a specific composition, characterized by a particular diffraction peak half width and intensity ratio in X-ray diffractometry, is used to facilitate pre-doping at a lower charging voltage, thereby preventing electrolytic solution decomposition and reducing the risk of short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal lithium foil is used as an ion source for pre-doping, then the negative electrode can be effectively doped with lithium ions, but the production cost increases and the volume energy density decreases
Solution Approach 1:
The patent changes the material parameter from metal lithium foil to lithium iron oxide with specific compositional parameters (x and y in Li_xFeO_y where 3.5≤x≤7.0 and 3.1≤y≤5.0) and crystallographic parameters (diffraction peak half width and intensity ratio). This material substitution maintains pre-doping effectiveness while eliminating the need for expensive metal lithium foil and through-hole collectors, thereby reducing production cost and increasing volume energy density.
2Reliability
If high charging voltage (4.5 V or more) is applied for pre-doping, then lithium can be effectively released from the pre-doping agent, but the electrolytic solution is oxidatively decomposed leading to accelerated deterioration
Solution Approach 1:
The patent optimizes the crystallographic parameters of lithium iron oxide, specifically controlling the diffraction peak half width at 23.6° to be 0.06° to 0.17° and the intensity ratio I44.6/I23.6 to be less than 8%. These parameter changes create a material structure that releases lithium at lower charging voltages, avoiding the oxidative decomposition of the electrolytic solution while maintaining effective pre-doping.
3Ease of manufacture
If conventional lithium iron oxide is used as pre-doping agent, then production cost is reduced, but short circuit may occur in the power storage device
Solution Approach 1:
The patent establishes specific parameter ranges for lithium iron oxide: compositional parameters (3.5≤x≤7.0, 3.1≤y≤5.0), diffraction peak half width (0.06° to 0.17° at 23.6°), and intensity ratio (I44.6/I23.6 < 8%). These parameter changes ensure the material has appropriate lithium release characteristics and structural stability, preventing short circuits while maintaining cost-effectiveness compared to metal lithium foil methods.
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 use of this lithium iron oxide pre-doping agent enhances the charging depth and discharge capacity of power storage devices while reducing production costs and preventing short circuits, thus improving the safety and performance of the devices.
Implementation Method 1
the lithium metal complex oxide is decomposed at a high voltage to release lithium
Implementation Method 2
due to a large irreversible capacity, it releases a large amount of lithium during charging
Implementation Method 3
Increase in a contact area of the lithium metal complex oxide with the carbon material facilitates effective electron supply to the lithium metal complex oxide through a highly conductive carbon material
Implementation Method 4
in X-ray diffractometry, a half width of a diffraction peak at a diffraction angle (2θ) of 23.6°±0.5°
Implementation Method 5
a half width of a diffraction peak at a diffraction angle (2θ) of 23.6°±0.5° is 0.06° to 0.17°
Implementation Method 6
a common electrolytic solution is oxidatively decomposed, leading to a problem of accelerated deterioration in performance
Data Source
AI summary
The present invention relates to a pre-doping agent for a power storage device comprising a lithium iron oxide represented by Formula (1), wherein in X-ray diffractometry, a half width of a diffraction peak at a diffraction angle (2θ) of 23.6°±0.5° is 0.06° to 0.17°, and an intensity ratio (I44.6/I23.6) of a diffraction peak intensity (I44.6) at a diffraction angle (2θ) of 44.6°±0.5° to a diffraction peak intensity (I23.6) at a diffraction angle (2θ) of 23.6°±0.5° is less than 8%. There is thus provided a pre-doping agent for a power storage device with a large irreversible capacity suitably used as a power storage device, which can suppress reduction in a volume energy density of a power storage device, can reduce a production cost, can prevent decomposition of an electrolytic solution because it allows for pre-doping with lithium ions at a lower charging voltage, has a high charging depth and a high discharge capacity, and can prevent occurrence of a short circuit. LixFeOy (1) wherein x meets 3.5≤x≤7.0 and y meets 3.1≤y≤5.0.