Lithium Battery Degassing Method Using Segmented Voltage Activation
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Solution Overview
Problem
Lithium secondary batteries with a cathode active material represented by formula (I) face safety issues and reduced lifespan due to gas generation during the high-voltage activation process, which existing technologies have not effectively addressed.
Innovation Solution
A method involving two degassing steps: one below and one above the voltage region where structural variation of the cathode active material occurs, to remove gases and enhance battery life by inducing uniform reactions and complete structural variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high voltage activation process is used to achieve high capacity, then battery capacity is improved, but gas generation increases causing safety problems and reduced battery life
Solution Approach 1:
The activation process is divided into multiple stages with different voltage ranges. The first activation occurs at a lower voltage range (below the uniform potential region 4.3-4.8V) and the second activation occurs at a higher voltage range (above the uniform potential region). This segmentation allows gas removal at each stage, preventing excessive gas accumulation while achieving high capacity.
Solution Approach 2:
The first activation process is performed as a preliminary step before the second activation. During this first activation at lower voltage, gas is generated and removed through a vent hole. This preliminary gas removal prevents excessive gas pressure and Li plating that would occur if all activation were done at high voltage in a single step.
2Device complexity
If single-stage degassing is used to simplify the process, then device complexity is reduced, but gas removal effectiveness deteriorates leading to Li plating and reduced battery life
Solution Approach 1:
The degassing process is segmented into two distinct activation steps with different voltage ranges. The first activation at lower voltage removes initial gas, and the second activation at higher voltage removes additional gas. This segmentation ensures thorough gas removal at each stage, preventing Li plating and extending battery life, while the overall process remains relatively simple.
3Quantity of substance
If high voltage activation is applied to induce structural variation of cathode material, then capacity is improved, but gas generation increases and remains in battery causing Li plating
Solution Approach 1:
The activation process is segmented into two voltage stages. The first stage at lower voltage (below 4.3V) generates and removes gas through a vent hole. The second stage at higher voltage (above 4.8V) induces structural variation for high capacity while generating additional gas that is also removed. This segmentation ensures gas is removed at each stage rather than accumulating to cause Li plating.
Solution Approach 2:
The gas generation, which is normally a harmful byproduct of activation, is converted into a beneficial process. By designing a vent hole and performing multiple activation steps, the gas is intentionally generated and then systematically removed. This converts the harmful gas accumulation into a controlled process that actually improves battery performance and longevity.
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 approach effectively removes gases generated during the activation process, enhancing the battery's lifespan and capacity retention by conducting degassing under specific voltage conditions, both below and above the structural variation range of the cathode active material.
Implementation Method 1
the lithium-containing compound used as a cathode active material is subject to structural variation at a high voltage, from which large amounts of gases may be generated
Implementation Method 2
the steps of (S1) and (S2) may be carried out under vacuum
Implementation Method 3
gases generated during the activation process should be removed... to deteriorate the transfer of lithium ions
Data Source
AI summary
The present disclosure provides a method for removing gases generated in a lithium secondary battery using a cathode active material of the following formula (I)Li(LixMy−y′M′y′)O2−zAz (I)wherein, x, y, y′, and z satisfy 0<x<0.5, 0.6<y′<1.1, 0≦y′<0.2, and 0≦z<0.2,M is any one selected from the group consisting of Mn, Ni, Co, Fe, Cr, V, Cu, Zn, and Ti,M′ is any one selected from the group consisting of Al, Mg and B; andA is any one selected from the group consisting of F, S and Nby carrying out two or more degassing steps under the conditions of above and below a voltage that the structural variation of the cathode active material occurs, thereby inducing a uniform initial reaction in a cathode and an anode to enhance the life time of the battery.