Li-Rich Rock Salt Cathode Coating for Capacity Retention
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Solution Overview
Problem
The deterioration of positive electrode active materials in lithium ion secondary batteries due to repeated charging and discharging leads to capacity decrease, primarily caused by irreversible structural changes and mechanical deterioration associated with the use of electrolytic solutions in liquid-type batteries, which is also observed in all-solid-state batteries.
Innovation Solution
A positive electrode active material with an irregular rock salt structure represented by the formula LixTi2x-1Mn2-3xO or LixNbx-0.5Mn1.5-2xO, with a LiNbO3 coating, is used in all-solid-state lithium ion batteries, which suppresses deterioration by avoiding reactions with electrolytic solutions, and is manufactured through a process involving mixing Li2CO3, Mn2O3, and TiO2 or NbO2 in a ball mill and subsequent firing and pulverization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid electrolytic solutions are used in lithium ion batteries, then ionic conductivity and electrochemical performance are improved, but positive electrode active material deteriorates due to irreversible structural changes and mechanical deterioration
Solution Approach 1:
A solid electrolyte layer is introduced as an intermediary between the positive electrode active material and the external environment, preventing direct contact and harmful reactions between the material and liquid electrolytic solutions, thereby maintaining structural stability while enabling ionic transport
Solution Approach 2:
The electrolyte phase is changed from liquid to solid state, fundamentally altering the interaction mechanism between the electrolyte and positive electrode active material, eliminating solvent-induced structural changes and mechanical deterioration while maintaining ionic conductivity
2Stability of the object's composition
If solid electrolyte is used instead of liquid electrolyte, then structural stability of positive electrode active material is improved, but manufacturing complexity increases
Solution Approach 1:
The solid electrolyte layer is formed in advance on the positive electrode active material surface through simple processes such as coating or sintering, establishing protective coverage before battery assembly, which simplifies the overall manufacturing process compared to complex liquid electrolyte handling and sealing requirements
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
This approach significantly enhances the capacity retention rate of all-solid-state lithium ion secondary batteries, maintaining 99% or more of the initial charge-discharge capacity after multiple cycles, compared to liquid-type batteries which retain about 60%, by preventing structural and mechanical deterioration typically associated with electrolytic solutions.
Implementation Method 1
mixing Li2CO3, Mn2O3, and TiO2 or NbO2 in a ball mill
Implementation Method 2
subjecting a mixture to firing to obtain a product
Implementation Method 3
pulverizing the product in the ball mill
Data Source
AI summary
A positive electrode active material of the present disclosure is a positive electrode active material for an all-solid-state lithium ion secondary battery that is represented by a general formula: LixTi2x-1Mn2-3xO (0.500<x<0.650) or a general formula: LixNbx-0.5Mn1.5-2xO (0.500<x<0.650) and that has an irregular rock salt structure. At least a part of the positive electrode active material of the present disclosure may be covered with a LiNbO3 coating.