Coated Ni-Rich Cathode Material for Stable Lithium Exchange
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Solution Overview
Problem
Lithium ion batteries, particularly those with Ni-rich electrode active materials, face issues with undesired surface reactions that can lead to electrolyte decomposition and capacity fade, despite attempts to coat the materials with oxides or remove impurities like LiOH or Li2CO3.
Innovation Solution
A process involving the reaction of electrode active materials with silicon alkoxide and alkyl aluminum compounds, followed by heat-treatment in an oxygen-containing atmosphere, to form a coated cathode active material with improved electrochemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrode active materials are coated with oxides (e.g., aluminium oxide or calcium oxide) to protect the surface, then electrolyte decomposition is reduced, but lithium exchange during charging and discharging is hindered
Solution Approach 1:
The coating composition is locally optimized by incorporating lithium-containing compounds (such as lithium phosphate, lithium carbonate, or lithium hydroxide) alongside protective oxides. This creates regions within the coating that are more conductive to lithium ions, allowing the coating to provide protection while maintaining lithium exchange capability in specific zones.
Solution Approach 2:
The coating is formed as a composite material combining multiple components: protective oxides (aluminum oxide, calcium oxide), lithium-containing compounds, and optionally carbon materials. This composite structure provides both the protective function against electrolyte decomposition and the conductive pathways for lithium ions through the lithium-containing phases and carbon networks.
2Manufacturing precision
If free LiOH or Li2CO3 is removed by washing with water, then surface impurities are reduced, but electrochemical properties do not improve in some instances
Solution Approach 1:
Instead of removing LiOH and Li2CO3 after material synthesis, the invention performs a preliminary action by intentionally incorporating controlled amounts of lithium-containing compounds into the coating formulation before the coating is applied and heat-treated. This transforms potential impurities into functional coating components that actively participate in lithium exchange.
Solution Approach 2:
The invention converts the harmful effect of free LiOH and Li2CO3 (which cause electrolyte decomposition) into a beneficial function by incorporating lithium-containing compounds into the coating structure. These compounds, when properly formulated and heat-treated, create conductive pathways for lithium ions while the protective oxide matrix prevents harmful reactions with the electrolyte.
3Quantity of substance
If Ni-rich electrode active materials are used to increase capacity, then energy density is improved, but surface reactions increase leading to capacity fade
Solution Approach 1:
The coating parameters are specifically optimized for Ni-rich materials by adjusting the ratio of protective oxides to lithium-containing compounds, controlling coating thickness, and optimizing heat-treatment temperature and duration. These parameter changes create a coating structure that is particularly effective at stabilizing the highly reactive Ni-rich surface while maintaining high lithium ion conductivity.
Solution Approach 2:
The coating acts as an intermediary layer between the Ni-rich electrode active material and the electrolyte. This intermediate structure mediates the interaction by providing a stable interface that prevents direct harmful reactions between the Ni-rich surface and electrolyte, while still allowing efficient lithium ion transfer through the lithium-containing compounds and carbon components in the coating.
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 process results in cathode active materials with enhanced cycling stability and reduced capacity fade, achieving excellent electrochemical performance by forming a protective layer that mitigates surface reactions.
Implementation Method 1
reacting said electrode active material with a silicon alkoxide and an alkyl aluminum compound
Implementation Method 2
reacting said electrode active material with a silicon alkoxide and an alkyl aluminum compound
Implementation Method 3
heat-treating the material so obtained in an oxygen-containing atmosphere at a temperature in the range of from 100 to 400°C
Data Source
AI summary
Process for making a coated electrode active material wherein said process comprises the fol-lowing steps: (a) providing an electrode active material according to general formula Li1+xTM1-xO2, wherein TM is a combination of metals according to general formula (I), and x is in the range of from zero to 0.2, with a moisture content in the range of from 500 to 1,500 ppm, (NiaCobMnc)1-dMd (I) with a. being in the range of from 0.3 to 0.4, b. being in the range of from zero to 0.1, c. being in the range of from 0.6 to 0.7, and d. being in the range of from zero to 0.1, M is Al or Ti or Zr or Mg, and a + b + c = 1, (b) reacting said electrode active material with a silicon alkoxide and an alkyl aluminum com-pound in one or more sub-steps, (c) heat-treating the material so obtained in an oxygen-containing atmosphere at a temperature in the range of from 100 to 400°C for 10 minutes to 4 hours.