LiCoO2 Battery Electrolyte Additives for High-Temperature Cycling
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Solution Overview
Problem
Lithium-ion batteries using LiCoO2 as a positive active material face instability and rapid capacity decrease when operated at high voltages due to lattice deformation, gas production, and corrosion issues, leading to poor performance and short cycle life.
Innovation Solution
A lithium-ion battery design incorporating a metal ion-doped lithium cobalt oxide material (Lix1Coy1M1-y1O2-z1Qz1) with a polynitrile six-membered nitrogen-heterocyclic compound and a halogen-substituted cyclic carbonate additive in the electrolyte, forming a stable complex layer and dense solid electrolyte interphase film to reduce surface activity and side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiCoO2 is used as positive active material and voltage is increased above 4.2V to extract more lithium ions, then capacity is improved, but structural stability deteriorates due to lattice deformation and Co4+ instability
Solution Approach 1:
The patent modifies the chemical composition parameters of LiCoO2 by doping with metal ions (Al, Ti, Zr, Mg, Ta) and adjusting stoichiometric ratios (Li1.05Co0.98Mg0.005Zr0.005Ti0.01O1.9F0.1), which changes the crystal structure stability and enables safe operation at higher voltages while maintaining structural integrity during lithium extraction
Solution Approach 2:
The patent creates a composite material system combining doped lithium cobalt oxide with surface coating layers (such as Li2SiO3, Al2O3, or TiO2) to form a core-shell structure that provides both high capacity and structural stability, where the coating layer protects the bulk material from degradation
2Quantity of substance
If deep delithiation is performed to increase capacity, then more lithium ions are extracted, but gas production increases due to Co4+ oxidation of electrolyte and surface oxygen
Solution Approach 1:
The patent converts the harmful effect of Co4+ by using it in a controlled manner within a stabilized lattice structure where it can be formed and reduced reversibly without causing electrolyte oxidation, or by using alternative cathode materials like Li1.2Mn0.6Co0.1Ni0.1O2 where high voltage operation does not produce harmful Co4+
Solution Approach 2:
The patent introduces surface coating layers as intermediary barriers between the cathode material and electrolyte, preventing direct contact and harmful oxidation reactions while allowing lithium ion transport, thus eliminating gas production during deep delithiation
3Productivity
If HF corrosion is allowed to proceed to dissolve Co4+ and deposit on negative electrode, then ion transport might be enhanced, but battery swelling increases due to gas production from electrolyte reduction
Solution Approach 1:
The patent introduces protective coating layers as intermediary barriers that prevent HF from reaching and dissolving Co4+, thereby eliminating the chain reaction that leads to electrolyte reduction and gas production, while maintaining ion transport through the coating's lithium conductivity
Solution Approach 2:
The patent eliminates the harmful HF corrosion pathway entirely by using HF-resistant coating materials (such as Al2O3, TiO2, or Li2SiO3) that are chemically stable in the electrolyte environment, converting a potentially harmful process into a stable, controlled system
4Quantity of substance
If high voltage operation is implemented to increase energy density, then capacity is improved, but cycle life decreases due to rapid capacity decrease from structural collapse
Solution Approach 1:
The patent modifies the crystal structure parameters by doping with metal ions that have different ionic radii and oxidation states, which adjusts the lattice parameters and strengthens the crystal structure to withstand high voltage stress during cycling, preventing structural collapse and extending cycle life
Solution Approach 2:
The patent creates a composite structure with a doped LiCoO2 core and a protective coating shell, where the core provides high capacity and the shell provides structural stability and protection against degradation during high voltage cycling, enabling long cycle life at high energy density
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 enhances structural stability, reduces gas production, and improves cycle and storage performance, especially under high-temperature and high-voltage conditions, with optimal additive concentrations maintaining effective performance.
Implementation Method 1
forming a stable complex layer... with a polynitrile six-membered nitrogen-heterocyclic compound
Implementation Method 2
forming a dense solid electrolyte interphase film... with a halogen-substituted cyclic carbonate additive
Implementation Method 3
when the voltage is greater than 4.2 V, the remaining 1⁄2 of lithium ions contained in LiCoO2 may continue to be extracted
Implementation Method 4
during deep delithiation, Co3+ is oxidized into quite unstable Co4+, which oxidizes an electrolytic solution together with surface oxygen that loses a large quantity of electrons
Implementation Method 5
due to high overlapping between a 3d energy level of Co and a 2p energy level of O, the deep delithiation also causes lattice oxygen to lose a large quantity of electrons, resulting in sharp shrinkage of LiCoO2 unit cells
Data Source
AI summary
A lithium-ion battery and an apparatus. The lithium-ion battery includes an electrode assembly and an electrolytic solution. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separation film A positive active material in the positive electrode sheet includes Lix1Coy1M1-y1O2-z1Qz1. A negative active material in the negative electrode sheet includes one or more of Si, SiOx2, a Si/C composite material, and a Si alloy. The electrolytic solution contains an additive A and an additive B, the additive A is a polynitrile six-membered nitrogen-heterocyclic compound with a relatively low oxidation potential, and the additive B is a halogen-substituted cyclic carbonate compound. The lithium-ion battery has superb cycle performance and storage performance, especially under high-temperature and high-voltage conditions.