Composite Cathode Coating for Nickel-Rich RLC Suppression
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Solution Overview
Problem
Nickel-rich ternary positive electrode materials in secondary batteries suffer from poor cycling performance, storage performance, and rate performance due to the formation of residual lithium compounds (RLCs) on their surface, which hinder ion and electron diffusion, leading to increased internal resistance and capacity decay.
Innovation Solution
A composite positive electrode material is developed, comprising a positive electrode active material coated with a composite layer containing particles of elemental S, Se, or Te, and a lithium-ion conductor material, which inhibits RLC formation, enhances ionic conductivity, and improves ion transport by constructing a conductive network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nickel-rich ternary positive electrode material is used to achieve high reversible capacity, then energy density is improved, but cycling performance and storage performance deteriorate due to RLC formation
Solution Approach 1:
A coating layer comprising particles containing elemental M (S, Se, or Te) and a lithium-ion conductor material is introduced as an intermediary between the nickel-rich ternary positive electrode material and the environment. This coating layer prevents direct contact between the positive electrode active material and air, thereby inhibiting RLC formation while maintaining high energy density. The lithium-ion conductor material ensures that ion transport is not hindered by the coating.
Solution Approach 2:
The coating layer is constructed as a composite material combining particles containing elemental M with a lithium-ion conductor material. This composite structure provides both the protective function of preventing RLC formation and the conductive function of facilitating ion transport, thereby resolving the contradiction between energy density and cycling performance.
2Use of energy by moving object
If nickel-rich ternary positive electrode material is used to achieve high reversible capacity, then energy density is improved, but storage performance deteriorates due to RLC formation
Solution Approach 1:
The coating layer acts as a protective intermediary that prevents direct interaction between the nickel-rich ternary positive electrode material and the environment during storage. By inhibiting RLC formation, the coating layer maintains the material's electrochemical properties and storage performance over time while preserving the high energy density.
Solution Approach 2:
The coating layer creates an inert protective environment around the positive electrode active material, isolating it from external factors that would otherwise lead to RLC formation during storage. This protective barrier ensures long-term stability and storage performance.
3Reliability
If coating layer is added to inhibit RLC formation, then cycling performance is improved, but device complexity increases
Solution Approach 1:
The coating layer is designed as a thin film structure that provides protective functions without significantly increasing the overall device complexity. The coating comprises particles containing elemental M and a lithium-ion conductor material, forming a functional layer that is integrated into the existing electrode structure.
Solution Approach 2:
The coating layer is constructed as a composite material combining particles containing elemental M with a lithium-ion conductor material. This composite structure provides both protective and conductive functions in a single integrated layer, minimizing the increase in device complexity while achieving improved cycling performance.
4Duration of action of stationary object
If coating layer is added to inhibit RLC formation, then storage performance is improved, but device complexity increases
Solution Approach 1:
The coating layer is designed as a thin protective film that provides long-term storage stability without significantly complicating the device structure. By preventing RLC formation during storage, the coating layer extends the operational life and maintains performance over time.
Solution Approach 2:
The coating layer serves as a protective intermediary that isolates the positive electrode active material from environmental factors during storage. This simple yet effective approach improves storage performance by preventing degradation reactions without requiring complex structural modifications.
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 composite material improves cycling performance, storage performance, and rate performance by inhibiting RLC generation, increasing ionic conductivity, and widening interlayer spacing, thereby enhancing the stability and capacity of the battery.
Implementation Method 1
The lithium-ion conductor material can construct a good ion conductive network at the material level, thereby improving the ion transport rate of the composite positive electrode material
Implementation Method 2
elemental M can also react with the positive electrode active material, replacing some oxygen atoms on the surface of the positive electrode active material, thereby being doped into the positive electrode active material
Implementation Method 3
Compared with oxygen atoms, M atoms have stronger electronegativity and larger atomic radius, and doping them into positive electrode active materials can not only enhance the ionic conductivity of positive electrode active materials, but also widen the interlayer spacing
Data Source
AI summary
A composite positive material and a preparation method therefor, a positive electrode plate comprising same, a battery, and an electrical apparatus. The composite positive electrode material comprises a positive electrode active material and a coating layer, wherein the coating layer coats at least part of the surface of the positive electrode active material, the coating layer comprises a composite material, the composite material comprises particles containing elemental M and a lithium-ion conductor material attached onto the surface of the particles containing elemental M, and M comprises at least one of S, Se and Te.