Lithium Secondary Battery Cathode Structure for Crack Resistance
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Solution Overview
Problem
Lithium secondary batteries face degradation in electrochemical performance and operational reliability due to crack formation in lithium metal oxide particles during repeated charging and discharging, especially at high temperatures, leading to reduced lifespan and increased internal resistance.
Innovation Solution
A lithium secondary battery design featuring a cathode active material layer with lithium metal oxide particles having a specific rod-shape morphology and an electrolyte solution containing a compound represented by Chemical Formula 1, which improves the aspect ratio and crystallite size of the particles, reducing crack formation and enhancing lifespan properties at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal oxide particles are used as cathode active material, then high operational voltage and energy density are achieved, but cracks occur inside particles during repeated charging and discharging
Solution Approach 1:
The cathode active material is divided into primary particles (rod-shaped with aspect ratio 1.5-5) that aggregate to form secondary particles. This segmentation allows the primary particles to accommodate expansion and contraction during lithium ion intercalation/deintercalation, preventing cracks in the overall particle structure while maintaining high energy density.
Solution Approach 2:
The rod-shaped primary particles are pre-formed with specific aspect ratio (1.5-5) and oriented with their major axis perpendicular to the cathode sheet surface before assembly into secondary particles. This preliminary structural arrangement prepares the particles to better withstand mechanical stress during battery operation, preventing crack formation.
2Ease of operation
If conventional electrolyte solution is used, then basic battery operation is maintained, but electrochemical performance degrades at high temperatures
Solution Approach 1:
The electrolyte solution composition is modified by adding a specific compound (cyclic carbonate with fluorinated alkyl group) to the conventional mixture of cyclic and chain carbonates. This parameter change in electrolyte composition improves the battery's electrochemical performance and stability at high temperatures while maintaining normal operation conditions.
3Reliability
If rod-shaped primary particles with aspect ratio 1.5-5 are used, then crack formation is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The aspect ratio of primary particles is controlled within a specific range (1.5-5) through adjustment of synthesis parameters including metal salt ratios, precipitant addition rate, and drying conditions. This parameter optimization achieves the desired rod-shaped morphology that provides crack resistance while being manufacturable.
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 exhibits improved lifespan properties and reduced internal resistance during long-term charging and discharging at high temperatures, maintaining performance through reduced crack formation and optimized electrolyte interaction.
Implementation Method 1
lithium metal oxide particles capable of reversibly intercalating and de-intercalating lithium ions
Implementation Method 2
an electrolyte solution containing a lithium salt and an organic solvent
Data Source
AI summary
A lithium secondary battery includes a cathode including a cathode active material layer that includes a plurality of lithium metal oxide particles, each lithium metal oxide particle having a form of a secondary particle including a plurality of aggregated primary particles, an anode facing the cathode, and an electrolyte solution containing a lithium salt and an organic solvent. The organic solvent includes a compound represented by a specific chemical formula. The plurality of primary particles include rod-shape particles having an aspect ratio of 1.5 to 5. The rod-shape particles have a major axis oriented in a direction from a center of the lithium metal oxide particle to a surface of the lithium metal oxide particle.