Ternary Cathode Crystal Material With Fused Grain Boundaries
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Solution Overview
Problem
Current ternary positive-electrode materials for lithium-ion batteries suffer from low initial coulombic efficiency and reduced cycle stability due to Li/Ni disordering, surface reconstruction, and grain boundary issues that hinder lithium ion diffusion and lead to electrolyte seepage and crack formation.
Innovation Solution
A crystal material with modified grain boundaries, characterized by reduced intergranular gaps and strong bonding between monocrystalline grains, enhancing lithium ion diffusion kinetics and structural stability, achieved through specific processing methods involving metal salts and thermal treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional synthesis methods are used for ternary positive-electrode material, then manufacturing process is simple, but initial coulombic efficiency is low and cycle stability is reduced
Solution Approach 1:
The patent applies preliminary action by performing grain boundary modification through metal salt treatment and thermal processing before the material is fully formed and used. The metal salts are introduced to grain boundaries during synthesis, and subsequent thermal treatment activates the modification process, preparing the grain boundaries in advance to prevent harmful effects during battery cycling.
Solution Approach 2:
The patent employs parameter changes by controlling the thermal treatment temperature (400-900°C) and duration (1-12 hours) to optimize grain boundary modification. By adjusting these parameters, the grain boundary structure is transformed to reduce intergranular gaps and improve bonding, thereby enhancing cycle stability while maintaining manufacturing feasibility.
2Speed
If grain boundaries are not modified, then manufacturing process is simple, but lithium ion diffusion is hindered and transmission kinetics is slow
Solution Approach 1:
The patent uses parameter changes by optimizing thermal treatment temperature (400-900°C) and time (1-12 hours) to control grain boundary modification. This transforms the grain boundary structure to reduce intergranular gaps and improve bonding, thereby enhancing lithium ion diffusion speed while maintaining manufacturing feasibility.
Solution Approach 2:
The patent introduces metal salts as intermediaries that facilitate grain boundary modification. These metal salts are introduced during synthesis and act as mediators during thermal treatment, enabling the transformation of grain boundary structure without requiring complex direct processing methods.
3Reliability
If grain boundaries have large gaps, then material structure formation is easy, but electrolyte seepage and crack extension occur reducing cycle stability
Solution Approach 1:
The patent applies parameter changes by controlling thermal treatment temperature (400-900°C) and duration (1-12 hours) to optimize grain boundary modification. By adjusting these parameters, the grain boundary structure is transformed to reduce intergranular gaps and improve bonding, thereby enhancing cycle stability while maintaining manufacturing feasibility.
Solution Approach 2:
The patent introduces metal salts to grain boundaries during synthesis as a preliminary action. This preparation enables subsequent thermal treatment to effectively reduce intergranular gaps and strengthen grain boundary bonding, preventing electrolyte seepage and crack extension during battery operation.
4Productivity
If surface reconstruction occurs, then synthesis process is straightforward, but lithium ion diffusion is hindered and initial coulombic efficiency decreases
Solution Approach 1:
The patent employs parameter changes by optimizing thermal treatment temperature (400-900°C) and time (1-12 hours) to control grain boundary modification. This transforms the grain boundary structure to reduce intergranular gaps and improve bonding, thereby enhancing lithium ion diffusion and initial coulombic efficiency.
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 modified crystal material exhibits improved electrochemical performance, thermal stability, and extended cycle life by reducing intergranular gaps and enhancing grain boundary fusion, leading to higher initial coulombic efficiency and structural integrity.
Implementation Method 1
heating to 400° C. to 900° C. and keeping at the same temperature for 1 hour to 12 hours
Implementation Method 2
heating the mixture to melt the metal salt, and then cooling the mixture
Implementation Method 3
a ratio L3/L4 of a grain boundary length L3 of a grain boundary at which a width of an intergranular gap is greater than or equal to 2 nm to a total grain boundary length L4 is less than or equal to 0.8
Data Source
AI summary
Examples of a crystal material and a preparation method are described. One example crystal material includes a secondary particle formed by agglomerating a plurality of monocrystalline grains. There are grain boundaries between the grains. Another example crystal material includes a monocrystalline particle. Each monocrystalline particle includes one monocrystalline grain. The crystal material is obtained by modifying a crystal material primary product in which monocrystalline particles have few defects, a gap at a grain boundary of a secondary particle is small, and bonding between grains is strong.