Solid Solution Cathode Material for High Capacity Retention
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Solution Overview
Problem
Conventional lithium ion secondary batteries using certain cathode compositions fail to achieve high discharge capacity and capacity retention ratio, despite advancements in energy storage for electric vehicles and hybrid systems.
Innovation Solution
A transition metal oxide containing solid solution lithium with a specific chemical formula (Li1.5[NiaCobMnc[Li]d]O3) is developed, incorporating a layered structure that transforms into a spinel structure during charge/discharge, enhancing discharge capacity and retention ratio, with a spinel structure change ratio of 0.25 to less than 1.0, and optimized through specific calcination and electrochemical pretreatment processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cathode compositions (Liy[M1(1-b)Mnb]O2 or Lix[M1(1-b)Mnb]O1.5+c) are used, then the battery structure remains stable without phase transition to spinel, but discharge capacity and capacity retention ratio are insufficient
Solution Approach 1:
The invention changes the chemical composition parameters by introducing a specific multi-element transition metal oxide system (Li1.5[NiaCobMnc[Li]d]O3) with controlled ratios of Ni, Co, Mn, and Li elements. This compositional parameter change enables both high discharge capacity (through the layered structure region) and structural stability (through the spinel structure region that prevents Jahn-Teller distortion), resolving the contradiction between capacity and stability.
Solution Approach 2:
The invention creates a composite cathode material combining layered structure regions (Li2MnO3) and spinel structure regions (LiMn2O4) within a single solid solution framework. The layered region provides high capacity while the spinel region provides structural stability and prevents phase transitions, achieving both improved discharge capacity and maintained reliability simultaneously.
2Productivity
If the spinel structure change ratio is increased to improve discharge capacity, then capacity retention may deteriorate due to excessive structural transformation
Solution Approach 1:
The invention optimizes the spinel structure change ratio parameter within the specific range of 0.25 to less than 1.0. This parameter control ensures that enough spinel structure is present to provide structural stability and prevent harmful phase transitions (maintaining capacity retention), while allowing sufficient layered structure to remain for high discharge capacity. The balanced composition Li1.5[NiaCobMnc[Li]d]O3 with a+b+c=1.2 and d=0.3 achieves this optimal ratio.
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 realizes higher initial discharge capacity and improved capacity retention, making it suitable for vehicle power supplies and portable instruments, while maintaining structural stability within defined chemical and physical parameters.
Implementation Method 1
a region changed to a spinel structure by being subjected to charge or charge/discharge in a predetermined potential range
Data Source
AI summary
A transition metal oxide containing solid solution lithium contains a transition metal oxide containing lithium, which is represented by a chemical formula: Li1.5[NiaCobMnc[Li]d]O3 where 0<a<1.4; 0≦b<1.4; 0<c<1.4; 0.1<d≦0.4; a+b+c+d=1.5; and 1.1≦a+b+c<1.4. The transition metal oxide containing lithium includes: a layered structure region; and a region changed to a spinel structure by being subjected to charge or charge/discharge in a predetermined potential range. When a ratio of an entire change from Li2MnO3 with a layered structure in a region to be changed to the spinel structure to LiMn2O4 with the spinel structure is defined to be 1, a spinel structure change ratio of the transition metal oxide containing lithium is 0.25 or more to less than 1.0.