T2-Phase Positive Electrode Material for High-Voltage Rate Performance
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Solution Overview
Problem
Lithium-ion batteries face challenges in achieving high specific capacity and maintaining good cycling performance, especially at high rates and high-voltage conditions, due to the collapse of the positive electrode active material's crystal structure.
Innovation Solution
A positive electrode active material with a lithium metal oxide composition, specifically belonging to a Cmca space group with a T2 phase stacked structure, is developed. This material exhibits excellent specific capacity, cycling performance, and rate performance under high-voltage conditions, with a discharge peak number of at least 4 in the capacity-voltage differential curve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charge and discharge voltage is increased to increase the capacity of the lithium-ion battery, then the specific capacity is improved, but the crystal structure of the positive electrode active material collapses, leading to rapid capacity decay and significant reduction in cycling performance
Solution Approach 1:
The patent applies parameter changes by precisely controlling the ratio of Li to transition metal atoms within specific ranges (Li: 1.001-1.005, transition metal: 0.995-0.999), and by controlling the particle size distribution (Dv10-Dv90 ratio: 0.02-0.05 μm²). These parameter optimizations enable the material to achieve high specific capacity while maintaining crystal structure stability and preventing collapse during high-voltage charging and discharging cycles.
Solution Approach 2:
The patent employs composite material strategy by creating a lithium metal oxide with multi-element transition metals (including Co, Ni, Mn, Al, Ti, etc.) in specific compositional ranges. This composite structure combines the advantages of different metals: Co and Ni provide high capacity, while Mn, Al, and Ti enhance structural stability. The synergistic effect of these elements in controlled proportions allows the material to withstand high voltage without crystal structure collapse.
2Use of energy by moving object
If the voltage is increased to improve specific capacity, then the energy density is improved, but the crystal structure collapses under high voltage, causing rapid capacity decay
Solution Approach 1:
The patent optimizes critical parameters including the Li to transition metal ratio (1.001-1.005), particle size distribution (Dv10-Dv90 ratio: 0.02-0.05 μm²), and elemental composition ratios. These parameter controls enable the crystal structure to remain stable at high voltages up to 4.55V, preventing collapse while maintaining high energy density. The refined particle size distribution also reduces internal stress during lithiation-delithiation cycles.
Solution Approach 2:
The lithium metal oxide combines multiple transition metals (Co, Ni, Mn, Al, Ti) in optimized proportions where Co (0.1-0.3) and Ni (0.1-0.3) contribute to high capacity, while Mn (0.01-0.1), Al (0.01-0.05), and Ti (0.01-0.05) provide structural reinforcement. This composite approach creates a crystal structure that resists high-voltage-induced collapse while delivering high energy density.
3Power
If the battery is discharged at a high rate to improve power output, then the rate performance is improved, but the capacity deterioration becomes more prominent due to crystal structure instability
Solution Approach 1:
The patent controls particle size parameters (Dv10-Dv90 ratio: 0.02-0.05 μm²) and compositional ratios to optimize rate performance. The smaller, more uniform particle size reduces diffusion paths for lithium ions, enabling faster charge/discharge rates. Simultaneously, the optimized composition and size distribution prevent crystal structure instability during high-rate cycling, maintaining capacity retention.
4Quantity of substance
If the positive electrode active material is designed for high voltage operation to increase capacity, then the specific capacity is improved, but the material experiences rapid capacity decay due to structural collapse
Solution Approach 1:
The patent implements precise parameter control including Li content (1.001-1.005), transition metal content (0.995-0.999), particle size distribution (Dv10-Dv90 ratio: 0.02-0.05 μm²), and elemental composition ratios. These optimized parameters enable the material to achieve high specific capacity while maintaining structural integrity over extended cycling, preventing the rapid capacity decay that typically occurs at high voltages.
Solution Approach 2:
The multi-element lithium metal oxide composite combines high-capacity elements (Co, Ni) with structurally stable elements (Mn, Al, Ti) in optimized proportions. This composite structure provides both high specific capacity and long cycle life by distributing mechanical stress and preventing crystal structure collapse during repeated high-voltage charging and discharging cycles.
Data Source
AI summary
The present application provides a positive electrode active material, a positive electrode sheet and a lithium-ion battery. When the battery, which is formed by the positive electrode active material and a lithium metal negative electrode, is discharged to a discharge cut-off voltage of 3.0 V at a rate of less than 1 C after being charged to a SOC of 100% at a rate of less than 1 C with a charge cut-off voltage of 4.55 V to 4.65 V, the number N of discharge peaks in the capacity-voltage differential curve of the battery is not less than 4. Under high-voltage condition, the positive electrode active material not only has excellent specific capacity and cycling performance, but also has more prominent rate performance.