Lithium Ion Battery Coating and Additives for Gas Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium nickel cobalt manganese ternary materials in lithium ion batteries suffer from high oxidizability, leading to electrochemical oxidation reactions, structural changes, and increased gas production due to residual lithium, which deteriorates performance, especially at high temperatures, and results in poor compressive strength and increased Direct Current Resistance (DCR) during cycling and storage.
Innovation Solution
A lithium ion battery design featuring a positive electrode active material with a matrix coated by two oxide layers, a first discrete island-like layer and a second continuous layer, along with additives in the electrolyte such as cyclic sultone compounds and lithium difluorobisoxalate phosphate, to reduce oxidative activity and gas production by forming a dense composite film and stabilizing the surface structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium nickel cobalt manganese ternary material with high nickel content is used to achieve high theoretical specific capacity, then the energy density is improved, but the oxidizability increases causing electrolyte decomposition and structural changes
Solution Approach 1:
The patent applies composite coating materials consisting of metal oxide (Al2O3, TiO2, ZnO, or ZrO2) and phosphorus-containing compounds (ammonium dihydrogen phosphate, ammonium hydrogen phosphate, or phosphoric acid) on the surface of lithium nickel cobalt manganese ternary particles. This composite structure provides both physical barrier protection against oxidation and chemical stabilization through phosphorus-containing compounds that form protective films during cycling, thereby maintaining high energy density while improving electrochemical performance stability.
Solution Approach 2:
The patent controls the coating thickness parameters precisely (total coating mass ratio of 0.1-5.0%, with metal oxide coating at 0.05-3.0% and phosphorus-containing compound coating at 0.05-2.0%). By optimizing these parameter ranges, the coating provides sufficient protection against oxidation and structural changes while minimizing the impact on the theoretical specific capacity and energy density of the high-nickel ternary material.
2Quantity of substance
If excess lithium salt is added during preparation to compensate for lithium loss during sintering, then the lithium content is improved, but residual lithium remains on the surface forming Li2O that absorbs CO2 and H2O to form LiOH and Li2CO3
Solution Approach 1:
The patent applies a coating layer that specifically targets and addresses the residual lithium on the particle surface. The phosphorus-containing compounds in the coating react with residual lithium to form stable lithium phosphate compounds that do not absorb CO2 and H2O, thereby extracting the harmful effect of residual lithium and converting it into a stable, non-gas-producing form.
Solution Approach 2:
The patent converts the harmful residual lithium (which forms gas-producing LiOH and Li2CO3) into beneficial stable lithium phosphate compounds through the phosphorus-containing compound coating. This transformation maintains the lithium content necessary for high capacity while eliminating the gas production problem, effectively turning a harmful byproduct into a protective feature.
3Ease of manufacture
If the ternary material is present as secondary particles formed by agglomeration of primary particles, then the manufacturing is improved, but the compressive strength is poor and specific surface area increases after crushing
Solution Approach 1:
The patent applies coating materials specifically on the surface of the secondary particles and at the interfaces between agglomerated primary particles. The metal oxide and phosphorus-containing compound coatings locally strengthen the particle structure and inter-particle bonds, providing enhanced compressive strength precisely where needed at the particle surfaces and interfaces without altering the overall secondary particle morphology or manufacturing process.
4Area of stationary object
If the specific surface area is significantly increased after the positive electrode active material is crushed, then the contact area with electrolyte is increased, but the gas production is intensified
Solution Approach 1:
The patent applies a protective coating layer before the electrode is assembled and before any crushing or cycling occurs. This pre-applied coating of metal oxide and phosphorus-containing compounds creates a stable surface that resists further reaction with the electrolyte, thereby preventing the intensification of gas production that would normally occur when the specific surface area increases due to crushing during electrode fabrication and cycling.
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 effectively reduces gas production, inhibits DCR increase, and enhances the mechanical strength and stability of the positive electrode, improving the overall performance and power retention of lithium ion batteries during cycling and storage.
Implementation Method 1
the electrolyte is likely to result in an electrochemical oxidation reaction on a surface of the positive electrode
Implementation Method 2
forming a dense composite film and stabilizing the surface structure
Implementation Method 3
an electrolyte including a lithium salt and an organic solvent
Data Source
Figure 1~2
Figure 3
AI summary
The present disclosure provides a lithium ion battery including a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. The positive electrode plate includes a positive electrode current collector, and a positive electrode film disposed on a surface of the positive electrode current collector and containing a positive electrode active material. The positive electrode active material includes a matrix, a first coating layer on the matrix in form of discrete islands, and a second coating layer on the first coating layer and the matrix as a continuous layer. The electrolyte includes an additive A and an additive B. The additive A is selected from a group consisting of cyclic sultone compounds represented by Formula 1 and Formula 2, and combinations thereof, and the additive B is one or two selected from lithium difluorobisoxalate phosphate and lithium tetrafluorooxalate phosphate.