Positive Electrode Coating for Low-Resistance All-Solid Lithium-Ion Batteries
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Solution Overview
Problem
All-solid lithium ion batteries face challenges in achieving sufficient output and cycle characteristics due to the high resistance of positive electrode active materials, even when coated with LiNbOs to suppress the formation of high resistant layers at the interface with sulfide-based solid electrolytes.
Innovation Solution
A positive electrode active material with a core composition of Li a Ni b Co c M d O 2, where M is selected from Mn, V, Mg, Ti, and Al, and a coated portion comprising Li and Nb with a transition metal of higher valency, such as W or Mo, is used to enhance ionic and electronic conductivity, reducing the battery's resistance and improving output and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiNbO3 coating is applied to suppress reaction with sulfide-based electrolyte, then interface stability is improved, but total resistance of active material increases
Solution Approach 1:
The patent applies a composite coating structure consisting of an inner LiNbO3 layer and an outer Li2MO4 layer (where M is W, Mo, or Ta). The LiNbO3 layer provides interface stability by suppressing reactions with sulfide-based electrolyte, while the outer Li2MO4 layer with higher electronic conductivity reduces the total resistance of the active material. This composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The patent implements different coating materials at different locations/positions within the coating structure. The inner layer uses LiNbO3 for interface protection, while the outer layer uses Li2MO4 for conductivity enhancement. This spatial differentiation of material properties allows each layer to perform its specific function optimally, resolving the contradiction between interface stability and resistance reduction.
2Duration of action of stationary object
If LiNbO3 coating is applied to prevent high resistant layer formation, then cycle characteristics are improved, but output characteristics deteriorate
Solution Approach 1:
The dual-layer coating structure with LiNbO3 inner layer and Li2MO4 outer layer simultaneously improves cycle characteristics (through interface stability from LiNbO3) and output characteristics (through enhanced electronic conductivity from Li2MO4), resolving the contradiction between durability and power performance.
Solution Approach 2:
The patent changes the material composition parameter of the coating by introducing Li2MO4 with higher electronic conductivity in the outer layer, while maintaining the protective LiNbO3 layer underneath. This parameter change enables simultaneous improvement of both cycle characteristics and output characteristics.
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 proposed solution results in improved ionic and electronic conductivity at the interface, leading to enhanced output and cycle characteristics for all-solid lithium ion batteries, with optimal ratios of Nb and higher valency transition metals in the coated portion achieving better performance without compromising capacity.
Implementation Method 1
enhance ionic and electronic conductivity at the interface
Implementation Method 2
enhance ionic and electronic conductivity at the interface
Data Source
AI summary
Provided is a positive electrode active material for all-solid lithium ion batteries, which exhibits good output characteristics and cycle characteristics when applied to all-solid lithium ion batteries. The positive electrode active material for all-solid lithium ion batteries includes: a core positive electrode active material having a composition represented by the following formula: LiaNibCocMdO2 in which M is at least one element selected from Mn, V, Mg, Ti and Al, 1.00 ≤ a ≤ 1.02, 0.8 ≤ b ≤ 0.9, and b + c + d = 1; and a coated portion formed on a surface of the core positive electrode active material, wherein the coated portion is an oxide comprising Li and Nb, and at least one transition metal having higher valency than that of Nb.