Positive Electrode Active Material Cooling for Stable Cycle Capacity
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Solution Overview
Problem
There is a need for improved positive electrode active materials in lithium-ion secondary batteries to enhance discharge capacity, cycle performance, reliability, safety, and reduce cost.
Innovation Solution
A method for forming a positive electrode active material through a process involving mixing a composite oxide containing lithium and cobalt with magnesium and fluoride sources, followed by heat treatment at specific temperatures and cooling rates to achieve a stable crystal structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional heat treatment methods are used for forming positive electrode active material, then the manufacturing process is simple, but the discharge capacity and cycle performance are insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling heat treatment temperature (650-1130°C) and cooling rate (250°C/h or faster) to form a specific crystal structure. This transforms the physical state of the composite oxide to achieve both high discharge capacity and excellent cycle performance, resolving the contradiction between productivity and reliability.
Solution Approach 2:
The patent uses composite materials by combining lithium-containing composite oxide with magnesium source and fluoride source to create a multi-component system. This composite approach enhances both discharge capacity and cycle performance simultaneously, addressing the technical contradiction through material composition optimization.
2Productivity
If high capacity positive electrode materials are developed, then discharge capacity improves, but structural stability during charging and discharging deteriorates
Solution Approach 1:
The patent utilizes phase transitions by controlling the heat treatment and cooling process to form a specific stable crystal phase. The rapid cooling (250°C/h or faster) from high temperature heat treatment creates a metastable phase with both high capacity and structural stability, resolving the contradiction between discharge capacity and crystal structure stability.
Solution Approach 2:
By changing the thermal parameters (heating to 650-1130°C followed by rapid cooling at 250°C/h or faster), the patent achieves a crystal structure that maintains stability during charging and discharging while providing high discharge capacity. This parameter control resolves the contradiction between capacity and structural stability.
3Reliability
If conventional cooling rates are used after heat treatment, then energy consumption is low, but the crystal structure stability and safety are insufficient
Solution Approach 1:
The patent changes the cooling rate parameter to 250°C/h or faster, which is significantly higher than conventional cooling rates. This rapid cooling creates a stable crystal structure that enhances safety and reliability. The energy consumption increase is justified by the substantial improvement in product performance and safety.
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 method results in a positive electrode active material with high discharge capacity, resistance to structural breakdown during charging and discharging, and improved safety and reliability of the secondary battery.
Implementation Method 1
a second step of heating the mixture to form a second composite oxide; The temperature retained in the second process is higher than or equal to 650° C. and lower than or equal to 1130° C.
Implementation Method 2
a third step of cooling down the second composite oxide. The temperature decreasing rate in the cooling is higher than 250° C./h
Data Source
AI summary
A positive electrode active material that inhibits discharge capacity from decreasing during charge and discharge cycles is provided. Alternatively, a secondary battery with a high level of safety is provided. The secondary battery includes a positive electrode containing a positive electrode active material, a negative electrode, and an electrolyte. The positive electrode active material is formed in the following manner: a first composite oxide containing lithium and cobalt, a magnesium source, and a fluoride are mixed to form a mixture; the mixture is heated at higher than or equal to 650° C. and lower than or equal to 1130° C. to form a second composite oxide; and the second composite oxide is cooled down at a temperature decreasing rate higher than 250° C./h.