Lithium Nickel-Based Composite Oxide with Lithium Halide Coating
Solution Overview
Problem
Rechargeable lithium batteries face challenges with high residual lithium levels on the surface of positive active materials, leading to gas generation and reduced cycle-life characteristics, which affects their stability and performance.
Innovation Solution
A lithium nickel-based composite oxide positive active material is developed, comprising large-diameter and small-diameter particles with different average particle diameters, where the small-diameter particles include lithium halide, reducing residual lithium and gas generation, and improving mixture density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional positive active materials are used, then the battery can operate, but residual lithium accumulates on the surface leading to gas generation and poor cycle-life
Solution Approach 1:
Lithium halide is introduced as an intermediary substance that mediates between the positive active material surface and the electrolyte. The lithium halide coating layer prevents direct contact and harmful interactions, reducing residual lithium accumulation and gas generation while maintaining electrochemical performance.
Solution Approach 2:
The surface composition parameter of the positive active material is changed by introducing lithium halide. This parameter change modifies the surface properties to reduce residual lithium and suppress gas generation, thereby improving cycle-life characteristics without sacrificing capacity.
2Quantity of substance
If particle size is reduced to improve mixture density, then packing efficiency improves, but surface area increases leading to more residual lithium and gas generation
Solution Approach 1:
Different regions of the particle system are given different properties: the core positive active material particles provide high density and capacity, while the lithium halide coating on the surface provides protective functionality. This local quality differentiation allows small particles to achieve high mixture density without the usual penalty of increased surface-related harmful effects.
3Object-generated harmful factors
If lithium halide is added to small-diameter particles, then residual lithium and gas generation are reduced, but particle complexity increases
Solution Approach 1:
The positive active material is transformed into a composite structure where lithium halide is integrated with the oxide particles. This composite approach combines the high capacity of the oxide core with the protective properties of lithium halide, achieving reduced residual lithium and gas generation while maintaining a relatively simple overall particle architecture.
Data Source
AI summary
This application relates to a positive active material for a rechargeable lithium battery including a lithium nickel-based composite oxide including a large-diameter particle and a small-diameter particle having different average particle diameters. The large-diameter particle includes secondary particles including a plurality of primary particles and the small-diameter particle includes lithium halide. The large-diameter particle has an average particle diameter (D50) of about 10 μm to about 20 μm, and the small-diameter particle has an average particle diameter (D50) of about 1 μm to about 8 μm. This application also relates to a method of preparing the positive active material, and a rechargeable lithium battery including the positive active material.