LiNiCoM Positive Electrode Material for Stable Cyclability
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Solution Overview
Problem
Lithium ion secondary batteries face challenges with high resistance, low capacity, and reduced charge-discharge cyclability due to impurities on the surface of positive electrode active materials, which can lead to electrolyte decomposition and performance degradation.
Innovation Solution
A positive electrode active material with a specific composition, represented by Li1+xNiyCozM1−x−y−zO2, where x, y, and z are within defined ranges, and includes a free lithium compound with controlled proportions of lithium hydroxide and lithium carbonate to minimize surface impurities and promote stable lithium ion diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the layered positive electrode active material is dispersed in water for washing to reduce surface impurities, then the charge-discharge cyclability is improved, but Li in the active material may be eluted to reduce the crystallinity of the active material surface and increase resistance
Solution Approach 1:
The patent changes the chemical composition parameters of the positive electrode active material by introducing a specific compositional formula Li1+xNiyCozM1−x−y−zO2 with controlled stoichiometric ratios. By precisely controlling the values of x, y, z and the identity of M, the patent optimizes the material's surface properties and bulk structure to reduce Li elution during washing while maintaining charge-discharge cyclability. This compositional parameter optimization resolves the contradiction between improving cyclability through washing and preventing resistance increase from Li loss.
2Quantity of substance
If high Ni content is used in LiMO2 positive electrode active materials to achieve high charge-discharge capacity, then the energy density is improved, but the charge-discharge cyclability and output properties are reduced
Solution Approach 1:
The patent creates a composite material system by combining multiple elements (Li, Ni, Co, M) in a specific layered structure with formula Li1+xNiyCozM1−x−y−zO2. This composite approach allows the material to simultaneously achieve high charge-discharge capacity from Ni content while maintaining good cyclability through the stabilizing effects of Co and M elements. The synergistic combination of different elements resolves the contradiction between high capacity and high reliability.
3Reliability
If the amounts of impurities such as lithium hydroxide and lithium carbonate on the surfaces of particles are reduced to prevent electrolyte decomposition, then the charge-discharge cyclability is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary action by controlling the compositional parameters and surface properties of the positive electrode active material during the manufacturing process itself, rather than relying on post-manufacturing treatments. By optimizing the compositional formula Li1+xNiyCozM1−x−y−zO2 and controlling synthesis conditions to produce materials with appropriate surface characteristics, the patent reduces impurity formation at the source. This preliminary control approach improves charge-discharge cyclability while avoiding the need for complex additional processing steps.
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 solution results in a positive electrode active material with low resistance, high capacity, and improved charge-discharge cyclability by reducing electrolyte decomposition and maintaining high energy density, enabling better battery performance.
Implementation Method 1
promote stable lithium ion diffusion
Data Source
AI summary
A positive electrode active material includes a primary particle represented by Compositional Formula (1):Li1+xNiyCozM1−x−y−zO2 (1),where x is a number satisfying a relation represented by an expression −0.12≤x≤0.2; y is a number satisfying a relation represented by an expression 0.7≤y≤0.9; z is a number satisfying a relation represented by an expression 0.05≤z≤0.3; and M is at least one element selected from the group consisting of Mg, Al, Ti, Mn, Zr, Mo, and Nb; or a secondary particle into which the primary particle aggregates. The primary particle or the secondary particle includes a free lithium compound in a weight proportion of 0.1% or more and 2.0% or less, and the weight of lithium hydroxide in the free lithium compound is 60% or less of the weight of lithium carbonate in the free lithium compound.