Positive Electrode Additive Network for Low-Resistance Lithium Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face challenges with low electrical conductivity and high irreversible capacity loss due to the use of conventional irreversible additives like Li6CoO4, which lead to decreased performance and safety concerns.
Innovation Solution
A positive electrode for lithium secondary batteries is developed, incorporating a positive electrode mixture layer with a lithium cobalt oxide additive represented by Chemical Formula 1, combined with conductive materials such as carbon nanotubes and graphite, to achieve a sheet resistance of 3.0 Ω/sq. or less, reducing oxygen gas generation and improving charging/discharging efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional irreversible additive Li6CoO4 is used in positive electrode, then lithium ion source is provided to overcome negative electrode capacity loss, but powder electrical conductivity is very low (10^-11 S/cm) causing high electrical resistance and rapid performance decrease at high C-rate
Solution Approach 1:
The patent uses Li6CoO4 as the base irreversible additive and composites it with conductive materials (carbon black, acetylene black, Denka black, ketjen black, Super-P, channel black, furnace black, lamp black, or thermal black) to create a composite positive electrode additive. This composite structure maintains the lithium ion source function of Li6CoO4 while the conductive materials provide electrical pathways, resolving the contradiction between capacity retention and electrical conductivity.
Solution Approach 2:
The conductive materials act as intermediaries between the insulating Li6CoO4 particles and the electrode current collector. These intermediary conductive materials bridge the electrical gap, allowing electrons to reach the Li6CoO4 particles without requiring the Li6CoO4 itself to be conductive, thus maintaining both the lithium ion source function and electrical conductivity.
2Reliability
If conventional irreversible additive Li6CoO4 is used in positive electrode, then lithium ion source is provided, but structural instability generates large amount of oxygen gas during charging causing volume expansion and performance deterioration
Solution Approach 1:
The patent intentionally uses Li6CoO4 as a sacrificial irreversible additive that is consumed during initial charging cycles. The Li6CoO4 serves its purpose as a lithium ion source and then degrades or transforms, accepting that it is a temporary, disposable component that enables the negative electrode to achieve stable cycling afterward. This resolves the contradiction by accepting short-term structural instability for long-term battery reliability.
Solution Approach 2:
The Li6CoO4 performs preliminary action by providing lithium ions during the initial charging cycle before the negative electrode structure is fully stabilized. This preliminary lithium ion supply prevents subsequent capacity loss, and the oxygen generation issue is managed as a one-time event during this initial activation phase rather than during normal operation.
3Stability of the object's composition
If graphite is used as negative electrode material, then battery structure is stable, but capacity per unit mass is small (372 mAh/g) making it difficult to increase battery capacity
Solution Approach 1:
The patent changes the parameter of negative electrode material from pure graphite to graphite combined with non-carbon-based materials (silicon, tin, or their oxides) that have higher theoretical capacity. The irreversible additive Li6CoO4 compensates for the initial capacity loss of these high-capacity materials, enabling the system to achieve both high capacity and stable cycling.
Solution Approach 2:
The negative electrode uses composite materials combining graphite with higher-capacity materials like silicon, tin, or their oxides. This composite structure allows the battery to achieve higher capacity while graphite provides structural stability. The irreversible additive Li6CoO4 in the positive electrode compensates for the initial capacity loss of the non-carbon materials, resolving the contradiction between capacity and stability.
4Quantity of substance
If non-carbon-based negative electrode material (silicon, tin, oxides) is used, then capacity is large, but initial efficiency is low with large lithium consumption and irreversible capacity loss
Solution Approach 1:
The patent uses Li6CoO4 as a sacrificial irreversible additive that is deliberately consumed during initial charging cycles. This disposable material provides lithium ions to compensate for the irreversible capacity loss of the non-carbon-based negative electrode materials. After this initial sacrifice, the negative electrode achieves stable cycling with high capacity retention.
Solution Approach 2:
The patent extracts the lithium ion source function from the negative electrode system by placing it in the positive electrode as Li6CoO4. This separation allows the negative electrode to focus on high-capacity non-carbon materials while the positive electrode's Li6CoO4 handles the lithium ion supply and compensation for initial losses, resolving the contradiction between capacity and irreversible 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
The solution enhances the electrical performance and safety of lithium secondary batteries by reducing oxygen gas generation and maintaining high charging/discharging capacity and capacity retention rates, while preventing side reactions and structural instability.
Implementation Method 1
the first conductive material contains one or more of carbon nanotubes, graphite nanofibers, carbon nanofibers, vapor-grown carbon fibers and activated carbon fibers
Implementation Method 2
a positive electrode additive represented by the following Chemical Formula 1... LipCo(1-q)M1qO4 wherein M1 is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo
Data Source
AI summary
Provided is a positive electrode for a lithium secondary battery and a lithium secondary battery including the same, wherein the positive electrode is manufactured by using a pre-dispersion containing a positive electrode additive represented by Chemical Formula 1 and a conductive material having a linear structure in a positive electrode mixture layer as an irreversible additive and, by adjusting the electrode sheet resistance to satisfy a specific range, it is possible to reduce the amount of oxygen gas generated during charging and discharging, as well as easily improve the charging and discharging efficiency of the lithium secondary battery.