Lithium-Ion Battery Electrode Design for Zero-Voltage Discharge
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Solution Overview
Problem
Conventional lithium-ion batteries suffer from capacity loss and corrosion issues when discharged to near zero volts, leading to degradation in performance and potential damage to the battery and medical devices that rely on them.
Innovation Solution
A lithium-ion battery design featuring a positive electrode with a lithium cobalt oxide active material and a negative electrode with a carbonaceous or lithium titanate primary active material, along with a secondary active material that provides charge and discharge capacity below the corrosion potential of the negative current collector and above the decomposition potential of the positive active material, ensuring stability and preventing corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional lithium-ion batteries are discharged to near zero volts, then the battery capacity is fully utilized, but corrosion of the negative electrode current collector occurs and deliverable capacity is lost
Solution Approach 1:
The patent modifies the electrochemical potential window of the battery system by selecting positive and negative electrode materials with specific potential characteristics. The positive electrode material (such as LiCoO2, LiMn2O4, or LiFePO4) is chosen to have a decomposition potential below zero volts, while the negative electrode material (such as graphite, lithium titanate, or lithium aluminum silicate) is selected to have a corrosion potential above zero volts. This parameter change in electrode material selection resolves the contradiction by enabling safe discharge to near-zero volts without corrosion or capacity loss.
2Reliability
If protection circuitry is added to prevent over-discharge, then battery corrosion is prevented, but device complexity increases
Solution Approach 1:
The battery system provides its own protection through the inherent electrochemical properties of the electrode materials. The positive electrode material's decomposition potential and the negative electrode material's corrosion potential create a natural protective window that prevents harmful reactions during discharge to zero volts. This self-service mechanism eliminates the need for external protection circuitry, resolving the contradiction between reliability and device complexity.
3Productivity
If the negative electrode potential approaches the copper corrosion potential, then zero voltage discharge is achieved, but negative current collector corrosion occurs
Solution Approach 1:
The patent changes the potential parameter relationship between electrodes by selecting materials where the negative electrode corrosion potential is elevated above zero volts. Materials such as lithium titanate (with a potential of approximately 1.5-1.6 volts vs. Li/Li+) or graphite (with a potential of approximately 0.05-0.1 volts vs. Li/Li+) are used to ensure the negative electrode remains at a safe potential during zero-voltage discharge, preventing copper corrosion while maintaining productivity.
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 maintains performance and prevents corrosion, allowing for safe discharge to near zero volts without significant capacity loss, reducing the need for protective circuitry and enhancing the functionality of medical devices powered by these batteries.
Implementation Method 1
During charging and discharging of the battery 10, lithium ions move between the positive electrode 20 and the negative electrode 30.
Implementation Method 2
The third active material exhibits charging and discharging capacity below a corrosion potential of the current collector of the negative electrode and above a decomposition potential of the first active material.
Data Source
AI summary
A medical device includes a rechargeable lithium-ion battery for providing power to the medical device. The lithium-ion battery includes a positive electrode comprising a current collector and a first active material and a negative electrode comprising a current collector, a second active material, and a third active material. The first active material, second active material, and third active material are configured to allow doping and undoping of lithium ions. The third active material exhibits charging and discharging capacity below a corrosion potential of the current collector of the negative electrode and above a decomposition potential of the first active material.