Lithium Cobalt Oxide Surface Modification for Battery Internal Resistance
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Solution Overview
Problem
Existing lithium batteries face challenges in reducing internal resistance and improving charge and discharge characteristics due to complex structures and production methods, particularly in the distribution of tungsten in positive electrode active materials and contact resistance between active materials and current collectors.
Innovation Solution
A composite body with a positive electrode active material composed of lithium composite metal oxide and a transition metal like cobalt, where the transition metal is exposed in a non-oxidized state on the surface, reducing internal resistance without additional elements, and an electrolyte system with a first and second electrolyte filling voids within the active material, enhancing ion conduction properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If W is unevenly distributed in the surface layer of the positive electrode active material to accelerate Li insertion/desorption reaction and suppress side reactions, then charge and discharge cycle characteristics are improved, but the structure and production method become complicated
Solution Approach 1:
The patent extracts the beneficial surface modification function from the complex W-containing crystalline compound structure and implements it through a simpler approach: forming a surface layer with specific Li, Co, and O ratios directly on the LiCoO3 particles. This eliminates the need for complex W distribution control while maintaining the acceleration of Li insertion/desorption reactions and suppression of side reactions.
Solution Approach 2:
The patent changes the compositional parameters of the surface layer by controlling the molar ratios of Li, Co, and O to satisfy specific relationships (Li:Co = 0.95-1.05 and Li:O = 0.47-0.53). This parameter control achieves the desired surface properties for accelerated Li reactions without requiring complex structural modifications or additional elements like W.
2Ease of manufacture
If the active material molded body is ground or polished to expose the surface for current collector contact, then the current collector can be bonded, but the contact resistance between active material and current collector remains high
Solution Approach 1:
The patent creates a localized surface layer with specific compositional quality (controlled Li, Co, and O ratios) that differs from the bulk material. This surface layer has enhanced properties for both bonding to the current collector and maintaining low contact resistance, solving the contradiction between ease of manufacture and electrical contact quality.
Solution Approach 2:
The patent creates a composite structure where a surface layer with specific stoichiometry (Li1-xCoyO2 or similar) coats the LiCoO3 particles. This composite surface layer provides both good bonding characteristics for current collector attachment and low contact resistance for electrical connectivity, resolving the contradiction between manufacturability and electrical performance.
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 reduces internal resistance and improves charge and discharge characteristics of lithium batteries by exposing non-oxidized transition metals on the surface and increasing the contact area with electrolytes, resulting in better ion conduction and battery performance.
Implementation Method 1
the transition metal of the positive electrode active material exposed on one surface is reduced... the internal resistance of a lithium battery can be reduced
Implementation Method 2
an electrolyte system with a first and second electrolyte filling voids within the active material, enhancing ion conduction properties
Data Source
AI summary
A composite body includes a positive electrode active material composed of a lithium composite metal oxide containing Li and at least one type of transition metal, and an electrolyte, wherein the positive electrode active material is present on one surface of the composite body, the one type of transition metal is Co, and the molar ratio of Co (cobalt) in the positive electrode active material (lithium cobalt oxide) present on the one surface is equal to or more than the molar ratio of O (oxygen).