Positive Electrode Material for Secondary Battery Over-Discharge Protection
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Solution Overview
Problem
Secondary batteries face issues with rapid capacity decline and potential fire or explosion due to over-discharge, as existing safety measures like protection circuits and PTC devices increase cost and weight, and current lithium battery structures limit discharge by the negative electrode, leading to capacity reduction.
Innovation Solution
A positive electrode material is developed with an active material precursor as an additive, mixed with a lithium compound, conductive agent, and binder, which suppresses lithium consumption at the negative electrode during over-discharge, preventing copper oxidation and enhancing over-discharge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protection circuits and PTC devices are incorporated into secondary batteries, then safety against overcharge and short-circuit is improved, but battery cost, volume, and weight increase
Solution Approach 1:
The invention extracts the safety function from external protection devices and transfers it to the battery's active materials. By incorporating overcharge-preventing agents into the electrolyte and over-discharge-preventing agents into the positive electrode, the safety function is embedded within the battery system itself, eliminating the need for separate protection circuits and PTC devices.
Solution Approach 2:
The battery materials perform safety functions autonomously without external control systems. The overcharge-preventing agent automatically decomposes at high potentials to prevent further charging, and the over-discharge-preventing agent prevents negative electrode discharge below safe potentials, creating a self-regulating safety mechanism.
2Reliability
If over-discharge protection is implemented using existing lithium battery structures, then discharge limitation is achieved, but battery capacity is rapidly reduced
Solution Approach 1:
The over-discharge-preventing agent is incorporated into the positive electrode in advance to counteract the harmful effects of over-discharge before they occur. When the battery voltage drops below a predetermined level, the agent prevents further discharge by blocking electron transfer, thereby preventing copper foil oxidation and capacity loss before they can happen.
Solution Approach 2:
The over-discharge-preventing agent acts as an intermediary substance that mediates between the positive and negative electrodes during discharge. It facilitates normal discharge operations but intervenes to stop discharge when voltage drops below the safe threshold, preventing direct harmful interactions between electrodes that would cause capacity loss.
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 solution prevents rapid voltage rise at the negative electrode, reduces capacity loss after over-discharge, and enhances capacity recovery, thereby improving the battery's over-discharge performance without the need for expensive safety devices.
Implementation Method 1
preventing copper oxidation and enhancing over-discharge characteristics
Implementation Method 2
prevents rapid voltage rise at the negative electrode
Data Source
AI summary
The present disclosure provides a positive electrode material comprising: a positive electrode active material mixture comprising a positive electrode active material prepared with an active material precursor and a lithium compound, a conductive agent and a binder; and an active material precursor as an additive, in which the active material precursor as the additive is a same substance as the active material precursor as a material of the positive electrode active material.