Lithium Ion Battery Electrolyte Using Boron Compound
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Solution Overview
Problem
Lithium ion secondary batteries using polyanion type lithium salts face challenges with insufficient lithium ion dissociation, leading to suboptimal battery performance, and existing solutions struggle to balance chemical and thermal stability with cost considerations.
Innovation Solution
A lithium ion secondary battery design incorporating a polyanion type lithium salt blended with a boron compound and an organic solvent, which enhances lithium ion dissociation and ion conductivity, using specific examples like poly(lithium 2-acrylamido-2-methyl-1-propanesulfonate) and boron trifluoride alkyl ether complexes, along with a matrix polymer and LiBOB, to create a high-performance electrolyte membrane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a polyanion type lithium salt is used in the electrolyte, then the electrolyte can provide both polymer matrix function and lithium salt function, but the lithium ion dissociation is insufficient leading to suboptimal battery performance
Solution Approach 1:
The patent uses a composite electrolyte system combining polyanion type lithium salt with conventional lithium salts (LiPF6, LiBF4, etc.) and carbonates. This composite approach allows the polyanion salt to provide dual functionality while the conventional salts ensure sufficient lithium ion dissociation and conductivity, resolving the performance limitation.
Solution Approach 2:
The patent optimizes the concentration ratio of polyanion type lithium salt to conventional lithium salt in the electrolyte composition. By adjusting these parameters (concentrations of components A-B and C-D), the system achieves both the versatility benefits of polyanion salts and the performance requirements of sufficient ion dissociation.
2Reliability
If conventional lithium salts like LiPF6 are used, then the battery achieves good performance, but thermal stability is poor and hydrolysis occurs easily
Solution Approach 1:
The patent creates a composite electrolyte system where thermally stable polyanion type lithium salts (A-B) are combined with conventional high-performance lithium salts (C-D). This composite approach allows the system to maintain good battery performance from the conventional salts while gaining thermal stability from the polyanion salts.
Solution Approach 2:
The patent assigns different functional roles to different components: polyanion type lithium salts provide thermal stability and dual functionality, while conventional lithium salts provide high ion conductivity and performance. This local functional assignment resolves the contradiction between performance and stability.
3Stability of the object's composition
If LiN(SO2CF3)2 is used as lithium salt, then thermal stability is improved, but the cost increases significantly
Solution Approach 1:
The patent combines polyanion type lithium salts (which have inherent thermal stability) with conventional, cost-effective lithium salts like LiPF6 or LiBF4. This composite approach achieves the thermal stability benefit without requiring expensive specialized salts, maintaining ease of manufacture.
Solution Approach 2:
The patent uses conventional, inexpensive lithium salts (C-D) as the primary conductivity providers, supplemented by polyanion salts for stability. This approach avoids the high cost of specialized stable salts while achieving the desired stability through the composite system.
4Quantity of substance
If nonaqueous electrolytic solution is used, then energy density is improved, but safety risk increases due to volatilization, diffusion, and dendrite formation
Solution Approach 1:
The patent creates a composite electrolyte system combining polyanion type lithium salts with conventional lithium salts and carbonates. This composite approach maintains the high energy density benefits of nonaqueous electrolytes while the polyanion component provides improved safety characteristics.
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 battery exhibits improved ion conductivity, lithium ion transference number, and cycle life, suppressing degradation and internal short circuits, while allowing for increased energy density and safety, with enhanced processability and packaging simplicity.
Implementation Method 1
the dissociation degree of lithium ions is not necessarily sufficient... (B) a boron compound... enhances lithium ion dissociation and ion conductivity
Data Source
AI summary
A lithium ion secondary battery is provided, including: a positive electrode and a negative electrode into which, and from which, lithium ions can be introduced and be discharged reversibly, and an electrolyte membrane placed therebetween, wherein the electrolyte membrane is obtained using an electrolyte made by blending (A) a polyanion type lithium salt, (B) a boron compound, and (C) an organic solvent.