High-Ni Positive Electrode Surface Layer for Capacity Retention
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Solution Overview
Problem
Lithium transition metal composite oxides with high Ni content (80 mol% or more) in non-aqueous electrolyte secondary batteries experience unstable layered structures, leading to decreased battery capacity with repeated charge/discharge cycles due to excessive Li ion extraction during charging.
Innovation Solution
A positive electrode active material with a lithium transition metal composite oxide having a surface modification layer containing Sr, Ca, or Ba, which stabilizes the surface structure and suppresses reaction with the electrolyte, maintaining battery capacity and improving output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the Ni content is increased to 80 mol% or more to obtain high discharge capacity, then the battery capacity is improved, but the layered structure becomes unstable and battery capacity decreases with repeated charge/discharge cycles
Solution Approach 1:
The patent applies local quality by creating a surface modification layer with specific alkaline earth metal elements (Sr, Ca, or Ba) on the surface of the high-Ni lithium transition metal composite oxide particles. This surface layer has different compositional properties than the bulk material, providing localized structural stabilization at the particle surface where the layered structure is most vulnerable during charge/discharge cycles, while maintaining the high Ni content (80 mol% or more) in the bulk for high capacity.
Solution Approach 2:
The patent employs composite materials by combining the high-Ni lithium transition metal composite oxide with a surface modification layer containing alkaline earth metal elements (Sr, Ca, or Ba). This composite structure integrates the high-capacity characteristics of the Ni-rich bulk material with the structural stability provided by the alkaline earth metal surface layer, resolving the contradiction between capacity and stability.
2Quantity of substance
If the Ni content is increased to 80 mol% or more to obtain high discharge capacity, then the battery capacity is improved, but the reaction with electrolyte increases and charge/discharge cycle characteristics deteriorate
Solution Approach 1:
The surface modification layer containing alkaline earth metal elements (Sr, Ca, or Ba) acts as an intermediary between the high-Ni lithium transition metal composite oxide and the electrolyte. This intermediate layer reduces the direct harmful interaction between the reactive Ni-rich material and the electrolyte, thereby improving charge/discharge cycle characteristics while maintaining high battery capacity.
Solution Approach 2:
The patent applies preliminary anti-action by pre-forming a protective surface modification layer on the high-Ni particles before they come into contact with the electrolyte during battery operation. This pre-established protective layer prevents the deterioration of charge/discharge cycle characteristics that would otherwise occur due to the high reactivity of Ni-rich materials with the electrolyte.
3Reliability
If a surface modification layer containing Sr, Ca, or Ba is formed to stabilize the surface structure, then the charge/discharge cycle characteristic is improved, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by controlling the content of alkaline earth metal elements (Sr, Ca, or Ba) in the surface modification layer to be within a specific range (0.01-5.0 wt%). This parameter control ensures sufficient structural stabilization and improved charge/discharge cycle characteristics while avoiding excessive complexity in the material structure and composition.
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 surface modification layer stabilizes the lithium transition metal composite oxide, enhancing charge/discharge cycle characteristics and output performance by reducing reaction resistance and maintaining battery capacity over cycles.
Implementation Method 1
a surface modification layer formed on the surface of the primary particles of the lithium transition metal composite oxide, wherein: the lithium transition metal composite oxide at least contains Ni in an amount of 80 mol% or more relative to the total number of moles of metal elements excluding Li, and Al; and the surface modification layer at least contains at least one of Sr or Ca, and Ba
Implementation Method 2
the surface modification layer stabilizes the lithium transition metal composite oxide, enhancing charge/discharge cycle characteristics and output performance by reducing reaction resistance and maintaining battery capacity over cycles
Implementation Method 3
charging/discharging is performed by causing lithium ions or the like to move between the positive electrode and the negative electrode
Data Source
Figure 1
AI summary
This positive electrode active material for nonaqueous electrolyte secondary batteries contains: a lithium transition metal composite oxide having secondary particles, each of which is formed of aggregated primary particles; and a surface modification layer which is formed on the surface of each primary particle of the lithium transition metal composite oxide. The lithium transition metal composite oxide contains at least Al and 80% by mole or more of Ni relative to the total number of moles of the metal elements excluding Li; and the surface modification layer contains at least Ba, and at least one of Sr and Ca.